Diagnostic Testing
With the arrival of health care reform, reimbursement practices such as managed care, and medicolegal concerns, health care is redefining the importance of history taking and physical examinations with a decreasing reliance on diagnostic tests. In the last two decades, before reform acts, health care relied heavily on the use of diagnostic testing to determine the nature of the client’s condition. Health care providers are using the findings from a thorough history and physical to determine the need for diagnostic testing. The client’s history and presenting symptoms determine which diagnostic procedures are necessary to formulate a medical diagnosis and the course of treatment. The challenge of cost-effective health care pushes practitioners to rely on basic assessment and to be selective with expensive diagnostic tests.
To reflect the emphasis on cost containment, the nurse’s role has changed from doing for the client to teaching clients to do for themselves. The role of the nurse is to teach the client, family, and significant others about the procedures involved with diagnostic testing, the steps to be taken in preparation for the specific test, and the care that will follow the procedure. Although the primary focus is on teaching, the nurse may assist in performing various noninvasive and invasive procedures. Nurses must be aware of the implications of diagnostic testing so as to deliver appropriate nursing care to the client. The terms test and procedure are used interchangeably throughout the chapter. The term practitioner is used in this chapter to refer to either the physician or other authorized prescribers. Most state boards of nursing allow advanced practice registered nurses to order and perform certain diagnostic tests.
UNDERSTANDING DIAGNOSTIC TESTING
To understand the nature of diagnostic tests, nurses need to review anatomy and physiology. Knowing the anatomical and physiological functions of the body will assist nurses in relating certain diagnostic tests to specific disease processes.
NONINVASIVE AND INVASIVE DIAGNOSTIC TESTING
Diagnostic tests are either noninvasive or invasive. Noninvasive means the body is not entered with any type of instrument. The skin and other body tissues, organs, and cavities remain intact. Invasive means accessing the body’s tissue, organ, or cavity through some type of instrumentation procedure.
Nursing Care of the Client
Diagnostic testing is a critical element of assessment. Assessment data are used to formulate nursing diagnoses, a plan of care, and outcome measures in collaboration with the client. Ongoing client assessment and evaluation of the client’s expected outcomes requires the incorporation of diagnostic findings.
Preparing a Client for Diagnostic Testing
The nurse plays a key role in scheduling and preparing the client for diagnostic testing. “The emphasis of pretest is on appropriate test selection, proper patient preparation, individualized patient education, and emotional support” (Fischbach, 2000, p. 9). When tests are not scheduled correctly, the client is inconvenienced. It may also delay interventions, which places the client’s health status at risk. The institution is also at risk to lose money. Table 28-1 presents a sample protocol of the nursing care to prepare a client for diagnostic testing.
The nursing care contained in the protocol provides a systemic format, based on the nursing process, to prepare the client for most diagnostic studies. During the assessment of the client, make sure the client is wearing an identification band (Figure 28-1). The identification band is a key factor to ensure client safety in all health care settings. Other key nursing measures to ensure client safety are to establish baseline vital signs, identify known allergies, and assess the effectiveness of teaching. In the ambulatory and outpatient centers, the nurse might have only one opportunity to assess and record the vital signs; it is important for the nurse to confirm that these findings are normal values for the client. To accurately assess the client’s response to anesthetic agents and the procedure, the nurse has to compare the vital signs taken during and after the procedure with the baseline data.
The client needs to know what to expect during the procedure. Teaching can increase the client’s level of cooperation and should decrease the degree of anxiety. The client’s family should also know what will happen during the procedure and approximately how long the procedure normally lasts. Reference is made to Table 28-1 throughout this chapter. This protocol provides you with the direction and guidance needed to plaursing care. Nurses must also know the institution’s protocols and procedures because these are not standardized in all practice settings.
Care of the Client During Diagnostic Testing
Although the care of the client needs to be individualized for a specific procedure, general guidelines for client care during a procedure are given in Table 28-2. Protocols are used to assist the nurse with client care. Standard Precautions are initiated when exposure to body fluids presents a threat to the safety of the caregiver. Protective barriers, such as gloves and a gown, should be used during invasive procedures. The nurse is responsible for labeling any specimen with the client’s name, room number (hospitalized clients), date, time, and source of the specimen. Some specimens may need to be taken immediately to the laboratory or placed on ice (e.g., arterial blood gases).
In order to promote the client’s comfort and cooperation during diagnostic tests, nurses must consider the management of procedural pain. Although not all procedures are painful, advances in diagnostic and therapeutic studies have placed clients at risk for painful procedures. Clients who are repeatedly subjected to painful procedures without adequate analgesia become anxious and anticipate pain; if pain is experienced during one procedure, the client is reluctant to return for the same procedure or other tests. “Unrelieved procedural pain also can have adverse physiologic effects, even if the pain is temporary” (Pasero, 1998, p. 18).
Recognizing that diagnostic procedures are performed in various settings, intravenous conscious sedation (conscious sedation) is often used to manage pain during diagnostic testing.
Conscious sedation is a minimally depressed level of consciousness during which the client retains the ability to maintain a continuously patent airway and respond appropriately to physical stimulation or verbal commands (Fischbach, 2000). The nurse managing conscious sedation is usually functioning in an expanded role that requires additional education and demonstrated ability beyond basic education.
See the accompanying display for some procedures that may require analgesia or sedation.
Ongoing assessment of the client’s status is required during the procedure. Always assess the patency of theclient’s airway, which may be compromised by the client’s position, anesthesia, or the procedure itself. During an invasive procedure the nurse needs to monitor for signs and symptoms of accidental perforation of an organ (e.g., sudden changes in vital signs). The nurse has additional responsibilities:
· Preparing the room (e.g., adequate lighting).
· Gathering and charging for supplies used during the procedure
· Testing the equipment to ensure it is functional and safe
· Securing proper containers for specimen collection
Practitioners usually have preference cards within the diagnostic testing area that specify the type of equipment to be used, the position to place the client, and the type of sedation or anesthesia.
Care of the Client After Diagnostic Testing
Nursing care postprocedure is directed toward restoring the client’s prediagnostic level of functioning (Table 28-3). Nursing assessment and interventions are based mainly on the nature of the test and whether or not the client received anesthesia. Anesthesia can be administered in one of three ways:
· Local anesthesia—client loses sensation to a localized body part—spraying the back of the throat with lidocaine to decrease the gag reflex
· Regional anesthesia—client loses sensation in an area of the body—laparoscope for a tubal sterilization
· General anesthesia—client loses all sensation and consciousness—major surgical procedures
The client is monitored closely for signs of respiratory distress and bleeding. Some diagnostic procedures require that the vital signs be measured every 15 minutes for the first hour, then gradually decreased in frequency until the client is stable (alert and vital signs within the client’s normal range).
Some diagnostic tests require the use of medications that are excreted through the kidneys; the nurse monitors the client’s intake and output for 24 hours. The client is taught how to monitor intake and output.
Instruct the client to report hematuria (presence of blood in the urine). Clients receiving radioactive iodine must have their urine collected and properly discarded in a special container, according to agency policy for handling radioactive medical wastes.
When clients are discharged after diagnostic tests, they should receive written instructions. Most agencies have discharge forms for the nurse to document teaching regarding medications, dietary and activity restrictions, and signs and symptoms to be reported immediately to the practitioner. Clients may also need to have follow-up appointments made for them.
LABORATORY TESTS
Common laboratory studies are usually simple measurements to determine how much or how many analytes, (a substance dissolved in a solution, also called a solute) are present in a specimen. Laboratory tests are ordered by practitioners to:
· Detect and quantify the risk of future disease
· Establish and exclude diagnoses
· Assess the severity of the disease process and determine the prognosis
· Guide the selection of interventions
· Monitor the progress of the disorder
· Monitor the effectiveness of the treatment
Nurses are often the first to view results of laboratory studies and they need to know the terminology regarding laboratory tests: purpose, process, procedure, and normal test values. The clinical value of a test is related to (Fischbach, 2000):
1. Specificity—the ability of a test to correctly identify those individuals who do not have the disease
2. Sensitivity—the ability of a test to correctly identify those individuals who have the disease
3. Incidence—the prevalence of a disease in a population or community. the predictive value of the same test can be different when applied to people of differing ages, genders, and geographic locations.
4. Predictive value—the ability of screening test results to correctly identify the disease state—a true-positive correctly identifies persons who actually have the disease, whereas a true-negative correctly identifies persons who do not actually have the disease.
Laboratory test results are based oormal range values. Le Système International d’Unités (SI), the International System of Units, is an international normal range reference established for reporting laboratory results (Pagana & Pagana, 1999). For example, the SI reference range for reporting red blood cell count for a woman is 4.0 to 5.2 × 1012/L, the conventional range would appear as 4,000,000 to 5,200,000/mm3 of blood.
Specimen Collection
The scheduling and sequencing of laboratory tests is an important function of the nurse. All tests requiring venipuncture (the puncturing of a vein with a needle to aspirate blood) are grouped together so that the clientis subjected to only one venipuncture. Fasting laboratory and radiologic studies are scheduled on the same day so that the client has to fast for only one day. Appropriate scheduling increases the client’s comfort level and satisfaction. “Communication errors account for more incorrect results than do technical errors” (Fischbach, 2000, p. 13). Accuracy in laboratory testing requires that:
· The practitioner’s order is transcribed onto the correct requisition form.
· All information requested should be written onto the form (e.g., the client’s full name and medical number).
· Pertinent data that could influence the test’s results, such as medication taken, must be included.
· Collection of the specimen from the correct client is confirmed by the identification band.
· Laboratory results are placed on the correct client’s medical record.
The risk for errors increases when clients have the same last name. Always check the full name of the client and the medical record number before placing the laboratory results report onto a chart.
Point of care testing (POCT) is a common practice in critical care settings and is proving to be a cost-effective, quality intervention for both clients and agencies. With advances in POCT technology over the past two decades, critical care nurses can perform a blood analysis and within seconds to minutes have a measurement upon which to change or implement an intervention. Schallom (1999) suggests that nurses be involved in the implementation and evaluation process of POCT since accuracy of the test is contingent on correct calibration and correct usage by the test performer. The following advantages are inherent in POCT (McConnell, 1999; Schallom, 1999):
· Prompt client diagnosis, treatment, and monitoring by decreasing turnaround time (TAT)
· Decreasing the risk for error by eliminating many of the steps in conventional laboratory testing
· Decreasing prolonged hospital stays and avoiding unnecessary hospitalizations by facilitating appropriate triage from emergency departments and prehospital settings
· Decreasing delays or cancellations of surgical procedures due to unavailable laboratory results, and the actual time the client spends in surgery;
· Minimizing blood loss due to phlebotomy since POCT devices usually require only a few microliters or drops of blood versus 25 to 125 microliters per day for the critically ill client due to laboratory testing
Studies regarding POCT’s clinical and financial value have revealed positive results: improved overall day-stay unit operations and client services; and earlier therapeutic decision-making time that required blood test results for emergency room clients (McConnell, 1999).
Although studies have proven positive results in settings where the client’s condition is acute and unstable, critical care applications may be quite different from that on a general medical/surgical unit. Studies will need to document the usefulness of POCT as a quality intervention ionacute care settings.
Venipuncture
Venipuncture can be performed by various members of the health care team. Laboratories employ a phlebotomist (an individual who performs venipuncture) to collect blood specimens; however, it is the responsibility of a nurse to know how to perform a venipuncture. Nurses routinely perform venipuncture in the home, long-term care settings, and hospital critical care units. Venipuncture can either be performed by using a sterile needle and syringe or a vacuum tube holder with a sterile two-sided needle. Test tubes are used to collect blood specimens. Test tubes have different colored stoppers to indicate the type of additive in the test tube.
Collecting tubes are universally color coded as follows:
· Red—no additive
· Lavender—EDTA (ethylenediaminotetraacetic acid)
· Light blue—sodium citrate
· Green—sodium heparin
· Gray—potassium oxalate
· Black—sodium oxalate
Noe and Rock (1994) address three sources of venipuncture variability that can cause inaccurate results. Hemoconcentration is the reduced volume of plasma water and the increased concentration of blood cells, plasma proteins, and protein-bound constituents.
It occurs with increased capillary hydrostatic pressure that causes water to shift from the intravascular into the interstitial space. Hemoconcentration can be caused from prolonged standing or a prolonged time of application of a tourniquet during venipuncture. Alterations in the circulating blood volume can also cause hemoconcentration, such as occurs with dehydrated and burned clients.
Hemolysis is the breakdown of red blood cells and the release of hemoglobin. Hemolysis occurs with the rapid flow of blood through small-bore needles and exposure to large negative pressures. A negative pressure exists inside the collecting test tubes and syringe. To minimize the possibility of hemolysis use a large-bore needle, moderate flow rates, and moderate negative pressures.
The third source of variability occurs when a blood specimen is drawn from a site above an intravenous infusion. The specimen is contaminated with intravenous solutions. Blood should be drawn from the client’s other arm or below the infusion site.
Venipuncture is an invasive procedure. Health care providers performing venipuncture are at risk for the transmission of blood-borne organisms, such as human immunodeficiency virus (HIV) and hepatitis. HIV is the causative agent for acquired immunodeficiency syndrome (AIDS).
Correct selection and preparation of equipment and vein provides for a safe and efficient venipuncture (Procedure 28-1). Review of the client’s health history and physical assessment data will assist in identifying special client considerations. If the client has a bleeding disorder or is taking anticoagulant therapy, apply pressure to the puncture site for 3 to 5 minutes after the removal of the needle.
Arterial Puncture
Assessment of arterial blood gases (ABG) reveals the ability of the lungs to exchange gases by measuring the partial pressures of oxygen (PO2) carbon dioxide (PCO2) and evaluates the pH of arterial blood. Blood gases are ordered to evaluate:
• Oxygenation
• Ventilation and the effectiveness of respiratory therapy
• Acid-base level of the blood
Arterial blood samples are drawn from a peripheral artery (e.g., radial or femoral) or from an arterial line. The arterial blood sample is collected in a 5-ml heparinized syringe. The syringe is then rotated to mix the blood with the heparin to prevent clotting. The blood sample is placed on ice to reduce the rate of oxygen metabolism.
In some agencies it is within the scope of nursing practice to perform radial artery puncture; however, femoral artery puncture is usually performed only by an advanced practitioner. An increased risk of hemorrhage exists with a femoral puncture. Although it is not common practice for student nurses to draw ABG samples, students often have to assist with the procedure and care for the client after the procedure.
Arterial punctures should not be performed:
· If the client is hyperthermic
· Immediately after breathing and suctioning treatments
· If there have been changes on ventilator settings
Arterial samples are also contraindicated in the following conditions:
· Anticoagulant therapy
· Clotting disorders
· Symptomatic peripheral vascular disease
· Negative Allen test
An Allen test is performed to measure the collateral circulation to the radial artery. Regardless of who performs the arterial puncture, the nurse is responsible for assessing the client for symptoms of bleeding or occlusion postpuncture. Direct pressure must be applied to the puncture site until all bleeding has stopped, a minimum of 5 minutes. Ensure that all bleeding has stopped before releasing the pressure. Symptoms of impaired circulation include:
· Numbness and tingling
· Bluish color
· Absence of a peripheral pulse
Capillary Puncture
Skin punctures are performed when small quantities of capillary blood are needed for analysis or when the client has poor veins. Capillary puncture is also commonly performed for blood glucose analysis, discussed later in this chapter. The common sites for capillary punctures are the:
· Heel—most common site for neonates and infants
· Fingertip—the inner aspect of palmar fingertip used most commonly in children and adults
· Earlobe—when the client is in shock or the extremities are edematous
To perform a skin puncture, assemble the equip ment, prepare the client, and select the appropriate site (Procedure 28-2). Figure 28-3 shows a capillary puncture of a fingertip.
Central Lines
Blood samples can be collected from central lines. A central line refers to a venous catheter inserted into the superior vena cava through the subclavian, internal, or external jugular vein. Central lines are used to treat alterations in fluid or electrolytes. The client’s nursing diagnoses may include the following: Deficient Fluid Volume related to nausea and/or vomiting or Imbalanced Nutrition, Less than Body Requirement related to anorexia.
A central line is inserted when a peripheral route cannot be obtained, for treatment, and to withdraw blood for analysis. Nurses need to know the type and location of the central line catheter. There are various types of central lines. Central lines can have either one or more lumens inside the catheter. For example, a central venous catheter has either one or two lumens, whereas a Hickman multilumen catheter, may have either two or three catheters contained in one sheath (Figure 28-4).
It is standard practice to mark each lumen of a multilumen catheter with the name of the infusion (e.g., fluid or medication). Lumens are marked to prevent the mixing of medications. Lumens without continuous infusion of fluids are capped with an infusion plug and flushed with a heparin solution every 8 hours according to agency protocol. Heparin prevents obstruction of the catheter lumen with a blood clot. The first sample of blood drawn from the central line cannot be used for diagnostic testing; it must be discarded. The amount of discard volume is directly related to the dead space (catheter size).
The agency’s protocol should indicate the volume to discard relative to the type and size of catheter. The nursing care of central lines requires strict sterile technique. The practitioner has to write an order to allow a blood sample to be obtained from a central line. Refer to the Nursing Checklist for how to draw a blood sample from a central line.
Implanted Port
Some clients have a port-a-cath (a port that has been implanted under the skin) over the third or fourth rib. The port has a catheter that is inserted into the superior vena cava or right atrium through the subclavian or internal jugular vein. The implanted port is used for the same purpose as the central lines.
Blood can be withdrawn for sampling by accessing the port using strict sterile technique. Accessing a port should only be performed by a nurse with proper education. Students are not usually taught how to access an implanted port.
Urine Collection
The kidneys are responsible for maintaining homeostasis of the body’s buffering systems and the volume, and ionic and osmotic composition of its fluid compartments. “Although the results of kidney functions are reflected in analyses of blood, the mechanisms by which normalcy of body fluids is preserved can be understood only through studies of urine” (Kirschbaum, Sica, & Anderson, 1999, p. 597).
Urine can be collected for various studies. The type of testing determines the method of collection. The different methods of urine collection are:
· Random collection (routine analysis)
· Timed collection
· Collection from a closed urinary drainage system
· Clean-voided specimen
The urine from a closed urinary drainage system is a sterile specimen. Client teaching depends on the client’s age and the method of collection. Initiate the protocol for preparing the client for testing (see Table 28-1). The method of collection should be written on the laboratory requisition.
Random Collection
The practitioner usually writes the order for a UA (routine urine analysis), which is also called a random collection. It can be collected at any time using a clean cup. The urine does not have to be collected in a sterile container. Instruct the client to urinate into the specimen cup or into a clean bedpan or urinal. Wearing gloves, transfer the urine into a clean container. Seal the lid tightly, label, and place in a biohazard bag for transport to the laboratory. Submit the specimen immediately to the laboratory to prevent the growth of bacteria or changes in the urine’s analytes (substances).
Timed Collection
Timed collection is done over a 24-hour period. The urine is collected in a plastic gallon container that contains preservative(s), some of which are caustic. The laboratory usually adds the preservatives to the container. If the analyte to be studied is light sensitive, a dark plastic container is necessary. Provide the client with specific instructions. The client is told to void (the process of urine evacuation) and discard the specimen at the beginning of the collection. The 24-hour collection begins with the first discarded voiding. For example, if the client is instructed to void at 1000 hours (24-hour clock time frame), discard the urine, save all other voided specimens until 1000 hours the following day. The client can void throughout the test into a clean container, then pour the urine into the collection bottle. Toilet tissue should not be dropped into the container used to catch the urine.
The collection container should be refrigerated or kept on ice throughout the 24 hours. This retards bacterial growth and stabilizes the analytes. The last urine collection, 1000 hours, should be a complete, forced voiding at the exact timed period. Seal the labeled container tightly and take immediately to the lab.
Collection from a Closed Drainage System
A sterile specimen can be collected from a client with an indwelling Foley catheter with a closed drainage system. A sterile specimen is used to culture the urine. The urine specimen should not be obtained from the drainage bag. The analytes in the urine drainage bag change; this will cause inaccurate results. Bacteria grow quickly in the drainage bag. The catheter’s closed drainage tubing has an aspiration port that is used for a sterile specimen collection (Procedure 28-3).
Clean-Voided Specimen
Clean-voided (clean-catch, or midstream) specimen collection is done to secure a specimen uncontaminated by skin flora. A clean-voided specimen should be obtained on first voiding in the morning. Most adult clients are capable of following instructions to perform this test. Different aseptic techniques are used for women and men. Poor technique in cleaning the perineum can contaminate the specimen. Instruct the female client to cleanse from the front to the back (Procedure 28-4).
Instruct the male client to perform the same procedure except for the cleansing of the perineal area; men should cleanse from the tip of the penis downward. The Nursing Checklist describes the procedure for obtaining a clean-voided specimen from a man. When obtaining a clean-voided specimen from infants and small children, secure assistance. Follow the Nursing Checklist.
Stool Collection
Explain to the client why the stool specimen is being collected. Instruct the client to defecate into a clean bedpan or container, discarding tissue into the toilet. Stools can be collected for either a one-time defecation or over 24, 48, or 72 hours. If a specimen is needed over a prolonged period of time, all stools must be placed into a container and refrigerated. Once collected, label the container with the client’s name, date, time, and the test to be performed on the specimen. All stool specimens are placed in a biohazard bag before transport to the laboratory.
Hematologic System
Understanding the hematologic system requires a knowledge of the blood’s composition and its functions. Table 28-4 discusses the origin, normal range values, and the major function for each of the three types of cells found in blood:
· Red blood cells (erythrocytes)
· White blood cells (leukocytes)
· Platelets
Forty to 45% of the blood’s volume is composed of blood cells; the remaining blood volume is plasma as shown in Figure 28-6. Plasma is part of the body’s extracellular fluid system, consisting of water and analytes. Blood proteins form the largest portion of the plasma analytes. The average plasma volume for a normal adult is 3 L.
Red Blood Cells
Red blood cells (RBCs), in embryonic life, are produced first in the yolk sac until the middle trimester; then the liver becomes the main organ of RBC production. RBC production becomes the exclusive function of the bone marrow by the end of gestation, after birth, and throughout life. RBC bone marrow site production changes with age:
· From birth to age 5—all bone marrow
· Five to 20 years—the shaft of the long bones (tibia and femur)
· After 20 years—the membranous bones (ilia, ribs, sternum, and vertebrae). As part of the normal aging process, the production of RBCs decreases with age.
Functions of the RBCs include:
· Transporting oxygen carrying hemoglobin
· Transporting carbon dioxide in the form of sodium bicarbonate
· Being an acid-base buffer for whole blood
White Blood Cells
There are six types of white blood cells (WBCs, leukocytes) found in the blood.
· Neutrophils
· Eosinophils
· Basophils
· Monocytes
· Lymphocytes
· Plasma cells
The polymorphonuclear cells, neutrophils, eosinophils, and basophils a have granular appearance, hence the name granulocytes or polys. The granulocytes and monocytes are responsible for phagocytosis (process by which certain cells engulf and dispose of foreign bodies). The lymphocytes and plasma cells function mainly as the body’s immune system.
The WBCs are formed and stored in the bone marrow until needed by the body. Table 28-5 presents laboratory studies for a complete blood count with SI values and when each analyte is either increased or decreased in clinical situations.
Red Cell Indices
Red cell indices measure the size and hemoglobin content of the RBCs. The RBC indices are:
· Mean red cell hemoglobin (MCH)
· Mean red cell hemoglobin concentration (MCHC)
· Mean red cell volume (MCV)
The indices are diagnostic in determining the type ofanemia. For example, an elevated MCHC means that spherocytes (smaller, thicker red cells) are present; this occurs in acquired hemolytic anemia.
Platelets
Platelets are fragments of a seventh type of WBC found in the bone marrow, the megakaryocytes. Platelets maintain hemostasis and blood coagulation by being the active mechanism of the blood in vascular repair. The active factors necessary for blood to coagulate are found in the cytoplasm of platelets. Blood coagulation is a comprehensive, sequential process of the body’s response to injury.
The blood coagulation flow chart (Figure 28-7) reviews the key elements of vascular constriction and coagulation. Prothrombin (factor II) is a plasma protein, formed in the liver, and requires vitamin K for synthesis. It is activated when blood vessels are damaged. Prothrombin activator causes the conversion of prothrombin into thrombin, which then causes fibrinogen to form threads. This whole process takes 10 to 15 seconds.
Prothrombin activator is the governing element in blood coagulation. Prothrombin time (PT) measures the defects in this extrinsic clotting mechanism, specifically fibrinogen (factor I), prothrombin (factor II), and factors V, VII, and X (Pagana & Pagana, 1999).
Drugs can either increase or decrease the PT. Common drugs that increase the PT include salicylates, steroids, sulfonamides, oral anticoagulants, antibiotics, quinidine, Dilantin, Aldomet, Tagamet, cathartics, and alcohol. Other drugs can decrease the PT: digitalis, oral contraceptives, corticosteroids, chloral hydrate, barbiturates, vitamin K, Placidyl, Doriden, griseofulvin, Alupent, and rifampin.
Partial thromboplastin (PTT) or activated partial thromboplastin time (aPTT) measures the intrinsic clotting mechanism factors (I, II, V, X, XI, XII). There are five primary screening tests to diagnose suspected coagulation disorders (Pagana & Pagana, 1999; Fischbach, 2000):
1. Platelet count, size, and shape
2. Bleeding time—the ability of platelets to functioormally and the ability of capillaries to constrict their walls, prolonged with deficiencies in platelets and other clotting factors
3. PTT—measures the ability of the blood to clot, prolonged with any intrinsic factor deficiencies such as hemophilia A (factor VIII) and hemophilia B (factor X)
4. PT—measures the total quantity of prothrombin in the blood, monitors the effectiveness of coumarin therapy, prolonged with deficiencies in the extrinsic factors and vitamin K
5. Fibrinogen level—investigates abnormal PT and APTT and to screen for disseminated intravascular coagulation (DIC) (an acquired hemorrhagic syndrome characterized by uncontrolled formation and deposition of thrombi) and fibrin-fibronogenolysis; levels increase with acute inflammatory reactions, trauma, coronary heart disease and cigarette smoking and decrease in liver disease, DIC, cancer, primary fibrinolysis and congenital hypofibrinogenemia.
Thrombin time (TT) measures the fibrinogen portion of the hemostatic mechanism; it is infrequently used today to evaluate the fibrinogen-to-fibrin reaction. Direct measurements of fibrinogen level and the increasing use of other tests have decreased the usefulness of TT (Pagana & Pagana, 1998).
Other common laboratory tests that measure hematologic functions are presented in Table 28-6.
Type and Crossmatch
A type and crossmatch is a laboratory test that identifies the client’s blood type and determines the compatibility of blood between a potential donor and recipient (client).
There are four basic blood types: A, B, AB, and O that are determined by the presence or absence of A or B antigens as seen in Figure 28-10. Antigens are substances, usually proteins, that cause the formation of and react specifically with antibodies. Antibodies are immunogloulins produced by the body in response to bacteria, viruses, or other antigenic substances. Type A and type B are antigens that are classified as agglutinogens, which are substances that cause agglutination (clumping of RBCs).
Agglutinins are specific kinds of antibodies whose interaction with antigens is manifested as agglutination.
Blood types are also designated as either positive or negative, depending on the presence or absence of the Rh factor. Rh factor refers to an antigen found on the RBC. Rh positive means the antigen is present; Rh negative means the antigen is absent.
When factoring the four basic blood types with either Rh positive or Rh negative factor there are eight possible combinations (see accompanying box). An individual’s blood type is determined by heredity.
Crossmatch determines the compatibility of the donor’s blood with that of the recipient. In the laboratory, a sample of the recipient’s blood is mixed with the blood of a possible donor. If the blood sample is compatible, the mixed sample does not agglutinate. For example, blood type A negative means that the person’s blood contains the A antigen but does not contain the anti-Rh agglutinins. The first time the person is exposed to A-positive blood, either through a transfusion or by giving birth to an Rh-positive child, agglutination does not occur because the body has no antibodies against the antigen. However, once the body has had time to build up antibodies (agglutinins), agglutination will occur.
Blood Chemistry
Blood chemistry analytes can be ordered separately or as profile groups (panels) that consist of 4 to 20 biochemical tests performed on a few milliliters of serum with an instrument called a sequential multiple analyzer (SMA). The studies are referred to as SMA panels based on the number of analytes being tested; refer to accompanying display.
Blood Glucose
Glucose is a simple sugar formed from the digestion of carbohydrates and used by the cells for energy. Insulin is needed to transport glucose into the cells. Glucose measurement is performed by either skin puncture or venipuncture, fasting blood sugar (FBS) or nonfasting (usually 2-hours postprandial). The normal fasting value is 70 to 115 mg/dl and less than 120 mg/dl postprandial. The 2-hour postprandial blood sugar is drawn 2 hours after the client eats a meal. This test is used to screen for diabetes mellitus; if the results are abnormal, the practitioner may order a glucose tolerance test. A glucose tolerance test is the most accurate test for diagnosing hypoglycemia and hyperglycemia (diabetes mellitus). The client is asked to fast until the test begins. The test is conducted as follows:
· Initial blood and urine specimens are obtained.
· An oral loading dose of glucose is administered.
· Blood and urine specimens are obtained at 30 minutes, 1 hour, 2 hours, 3 hours, and sometimes 4 hours after loading dose.
Figure 28-11 is a graphic presentation of the results of a glucose tolerance test, showing results that indicate hyperglycemia, normal glucose, and hypoglycemia.
Glucose results reveal deficits in either the digestion of carbohydrates or glucose metabolism (e.g., diabetes mellitus). Drugs, especially diuretics and steroids, can cause physiological changes resulting in elevated blood glucose values. Clients receiving intravenous fluids with a high glucose content need to have their glucose levels monitored for hyperglycemia.
Serum Electrolytes
An electrolyte is an element or compound that, when dissolved in water or another solvent, separates into ions and provides for cellular reactions. Some electrolytes act on the cell membrane allowing for the transmission of electrochemical impulses ierve and muscle fibers. Other electrolytes determine the activity of different enzymatically catalyzed reactions that are necessary for cellular metabolism.
Cations are ions that have a positive charge: sodium (Na+), potassium (K+), calcium (Ca++), and magnesium (Mg++). Anions are ions that have a negative charge: chloride (Cl–) and phosphate (HPO4–).
The routine electrolyte laboratory tests are presented in Table 28-7. These tests measure the serum concentration of sodium, potassium, calcium, chloride, magnesium, and phosphate.
Blood Enzymes
Enzymes are globular proteins produced in the body that catalyze chemical reactions within the cells by promoting the oxidative reactions and synthesis of various chemicals, such as lipids, glycogen, and adenosine triphosphate (ATP). Enzyme tests play a key role in diagnosing the degree of tissue damage mainly to the myocardium and, to a lesser degree, to the brain.
Elevations in plasma levels of intracellular enzymes occur during myocardial necrosis (tissue death as the result of disease or injury). Enzymes are released into the bloodstream in proportion to the degree of cellular damage. Table 28-7 discusses the common alterations of electrolytes and their clinical significance.
Enzymes are not used as single diagnostic values in determining a diagnosis but are viewed in relation to other diagnostic studies. The results from several diagnostic procedures will assist the practitioner in determining the cause of clinical symptoms.
Creatine phosphokinase (CPK) is an enzyme used to convert creatine to phosphocreatine and adenosine diphosphate (ADP) to ATP. ATP provides energy to the cells to carry on metabolism. CPK levels indicate the degree of normal tissue catabolism. Elevated values of CPK reflect the damage that has occurred in tissue with a high CPK content. For example, the myocardium has a high CPK content; when the client has a myocardial infarction, CPK is elevated because the heart’s tissue has been damaged, requiring ATP to repair the damaged myocardium. Creatine phosphokinase has three isoenzymes of differing molecular structure that are present in different tissue (Table 28-8). The isoenzymes provides clinical data to the practitioner in diagnosing the site and extent of tissue injury.
Aspartate aminotransferase (AST) is one of two enzymes that catalyze the transfer of the nitrogenous portion of an amino acid to an acid residue. It is an intracellular enzyme found mainly in the liver, heart, skeletal muscles, kidney, pancreas, and RBCs. The normal range is:
· Adults/children 4–36 IU/L
· Newborns 4 times as high as those of adults.
Blood for AST is drawn to determine:
· A recent myocardial infarction (together with the CPK and lactic dehydrogenase levels)
· Acute hepatic disease
· The client’s progress and prognosis in cardiac and hepatic diseases
Certain drugs may increase the AST (see the accompanying box). Remember to note drugs on the laboratory requisition when a client is taking a drug that can influence the results of testing.
Lactic dehydrogenase (LDH), a cellular enzyme that contributes to carbohydrate metabolism, catalyzes the reversible conversion of muscle pyruvic acid into lactic acid. The diagnostic value of serum LDH is limited because it is present in almost all body tissue; however, through electrophoresis, five isoenzymes can be related to specific tissue (Table 28-9).
The percent of isoenzymes changes with tissue damage. For example, in an acute myocardial infarction the LHD1 becomes greater than LDH2 12 to 48 hours postinfarction.
α-Hydroxybutyrate dehydrogenase (HBD) is the total LDH forced to act on α-ketobutyric acid rather than lactic or pyruvic acid. It is a serum measurement used when the assay of isoenzymes of LDH is not available in the laboratory. Once a myocardial infarction has been diagnosed, the HBD has clinical significance by indicating the duration of tissue injury. HBD will remain elevated up to 2 weeks after infarction.
Alkaline phosphatase (a zinc-dependent enzyme) influences bone calcification and lipid and metabolite transport. The normal plasma range is 30 to 120 IU/L. Alkaline phosphatase is used to detect:
· Osteoblastic activity
· Hepatic tumors or abscess
· Impaired zinc status
· The response of vitamin D in the treatment of deficiency-induced rickets
Certain drugs can cause a mild to moderate elevationin the alkaline phosphatase (see the accompanying box).
Acid phosphatase is an enzyme found primarily in the adult male prostate gland. It is used clinically to distinguish between encapsulated and metastatic carcinoma of the prostate gland. If the cancer cells are contained within a capsule, the acid phosphatase levels remaiormal (0.2 to 0.8 IU/L).
Glucose-6-phosphate dehydrogenase is a RBC enzyme. The normal range and the clinical significance were shown in Table 28-6.
The main proteolytic enzymes for digestion are contained in the pancreatic juices (trypsin, chymotrypsin, and carboxypeptidase). The common laboratory tests for measuring the digestive enzymes are presented in Table 28-10.
Cholinesterase is an enzyme, manufactured in liver, hat is responsible for the breakdown of acetylcholine and other choline esters. The normal range for cholinesterase in adults and children is 8 to 18 IU/L. It s elevated in diabetes, hyperthyroidism, and nephritic yndrome. Decreases in cholinesterase can result from severe anemias and infections, exposure to some insecticides, liver disease, malnutrition, shock, and uremia (Cavanaugh, 1999).
Blood Lipids
Coronary heart disease (CHD) is the number one killer of both men and women in the
According to the
Blood cholesterol for adults is classified by levels. Exogenous cholesterol is present in the diet and absorbed into the gastrointestinal tract. Endogenous cholesterol is formed in the liver and other cells in the body. As much as 80% of cholesterol is converted into cholic acid to form bile salts. Cholesterol is also needed:
Throughout the body for the formation of membranes
· By the adrenal glands to form adrenocortical hormones
· By the ovaries to form progesterone and estrogen
· By the testes to form testosterone
· By the skin to provide a water-soluble barrier
Cholesterol and other fats cannot dissolve in the blood; they have to be transported to and from the cells by special carries called lipoproteins (blood lipids bound to protein). The types of lipoproteins are described below, but the ones to be most concerned about are low-density lipoprotein (LDL) and highdensity lipoprotein (HDL).
Chylomicrons—mainly ingested triglycerides
· Very low-density lipoproteins (VLDLs)—mainly endogenous triglycerides
· Low-density lipoproteins (LDLs)—moderate amounts of phospholipids with 50% cholesterol
· High-density lipoproteins (HDLs)—50% protein LDL is the major cholesterol carrier in the blood.
When too much LDL circulates in the blood, it can slowly build up in the walls of the arteries feeding the heart and brain. The build up of LDL and other substances causes the formation of atherosclerotic plaque, a thick, hard deposit that can clog the arteries in the heart and brain. A thrombus (a blood clot) can develop around the plaque that blocks the flow of blood to part of the heart muscle and causes a myocardial infarction (MI). If the thrombus blocks the flow of blood to part of the brain, it results in a cerebrovascular accident (CVA).
High levels of LDL cholesterol (more than 130 mg/dl) increase the risk for CHD; this type of cholesterol is often called bad cholesterol.
HDL accounts for one-third to one-fourth of blood cholesterol and carries the cholesterol away from the arteries and back to the liver, where it is removed from the blood. HDL removes excess cholesterol from atherosclerotic plaques, slowing their growth. HDL is known as good cholesterol because a high level of HDL seems to decrease the risk of CHD.
Triglycerides are the chemical form in which most fat exists in food as well as in the body; they account for more than 90% of dietary intake and comprise 95% of fat stored in tissues (Fischbach, 2000). Triglycerides are insoluble in water and are the main plasma glycerol ester. An increase in triglyceride levels can be detected by plasma measurements; this test evaluates suspected atherosclerosis and measures the body’s ability to metabolize fat.
Table 28-11 shows the relationship of lipids to a client being at risk for CHD. The practitioner must examine all of the lipid levels together. For instance, a client whose total cholesterol, LDL cholesterol, and triglycerides are all slightly elevated and whose HDL is slightly decreased is at a greater risk for CHD than someone whose cholesterol is elevated but whose HDL is also high.
The nurse must prepare clients for the lipid level testing by teaching them to:
· Eat a regular diet 3 to 7 days before the test
· Fast 12 to 14 hours before the test
· Refrain from vigorous exercise 24 hours before the test
· Refrain from caffeine and nicotine 24 hours before the test
· Per practitioner order, withhold drugs 24 hours before the test (many drugs affect the serum triglycerides level)
· Be aware that repeat tests may be necessary to confirm elevated levels because results can vary 15% or more from day to day.
Diurnal variation causes triglycerides to be lowest in the morning and highest around noon (Fischbach, 2000). Several factors can affect the test results. The client’s position, such as lying down, causes a redistribution between vascular and extravascular compartments. For instance, after 5 minutes in a recumbent position, total plasma cholesterol may be significantly reduced (10–15% decrease after 20 minutes). Recent trauma and severe infections may decrease the cholesterol level by 10% to 30%. Because pregnancy increases the HDL, LDL, VLDL levels 20% to 30%, postpone testing 3 to 4 months postdelivery.
Therapeutic Drug Monitoring
Therapeutic drug monitoring is performed when a quantitative relationship exists between the drug concentration and drug response or toxicity is known. For a drug concentration to be significant:
· It must be determined in a blood sample drawn after the drug has been completely absorbed from the oral or intramuscular route.
· It has had an opportunity to be distributed to its site of action.
· Its steady state has been reached (e.g., four to five half-lives must have passed).
For instance, with digoxin (a cardiac medication, administered on a daily schedule) the absorption and distribution phases may take 6 to 12 hours to complete.
For a meaningful interpretation, the blood specimen should be drawn at least midway through the elimination phase (6 hours before the next dose). If the specimen is drawn just before the next dose, one obtains a trough concentration, whereas a specimen drawn 6 to 12 hours after dosing yields a peak concentration. For digoxin, the swing between peak and trough would be expected to be minimal because the drug is given at intervals that are less than the drug’s terminal half-life (42 ± 19 hours). Generally, such sampling is most significant after steady state has been reached (about 8 days for digoxin). Trough and peak sampling help the practitioner to determine the dose rate, keeping the drug level below toxic value.
Arterial Blood Gases
Blood gas results are reported in millimeters of mercury (Hg). Normal ABG ranges are:
• PO2 75–100 mm Hg
• PCO2 35–45 mm Hg
• pH 7.35–7.45
The clinical interpretation of gases studies the relationship between the gasses. For example, a low PO2 combined with a high PCO2 may indicate bronchiole obstruction or that the alveoli are filled with fluid. In both situations, there is an impairment of gaseous exchange.
Urine Tests
The primary function of the kidneys to rid the body of waste products and to maintain homeostasis through regulation of the acid-base balance, fluid and electrolyte balance, and arterial blood pressure. Urine leaves the kidneys through the ureters. Peristaltic waves move the waste products through the ureters to the bladder. Normally, the bladder stores 200 to 400 ml of urine; however, its capacity is greater.
Urinalysis (UA) is an essential part of an examination for both diagnostic and preventive purposes. UAs are easy to collect and can be a valuable screening procedure. The kidneys have the ability to regulate sodium and urine concentration and dilution in accordance with the needs of the individual. The main urine constituents are water, urea, uric acid, creatinine, ammonia, sulfates, sodium, potassium, chloride, calcium, magnesium, and phosphate. Other kidney filtrates found in the urine include hormones, vitamins, and medications.
The urine may also contain other constituents indicative of disease such as RBCs and WBCs, casts, crystals, mucus, bacteria, protein, glucose, and ketones. See the accompanying box for normal values.
Although laboratories provide a wide range of urine tests, some types of tablet, tapes, and dipstick tests for UA can be performed outside the laboratory setting. Kerr, Marshall, and Sinclair (1999) conducted a study to determine if there was a difference in the urine results obtained by the emergency department physician as compared with the results obtained by a trained laboratory technician.
On comparison, the results were similar for both dipstick and microscopic components of urinalysis: red blood cell urinalysis and microscopy, leukocyte esterase, and nitrite testing; however, emergency physicians were not able to consistently perform UA for microscopic white cells and bacteria, and testing for proteinuria.
Urine pH
The pH is governed by the hydrogen ion concentration of the urine. Disorders such as diabetes mellitus, dehydration, diarrhea, emphysema, and starvation make the urine acidic. Chronic renal failure, renal tubular acidosis, urinary tract infections, and salicylate poisoning cause the urine to be alkaline.
Specific Gravity
Specific gravity measures the number of solutes in a solution. Urea and uric acid (the byproducts of nitrogen metabolism) have the greatest influence on the specific gravity of urine. A urinometer and cylinder are used to measure the specific gravity (Figure 28-12). The urinometer has a specific gravity scale and a weighted mercury bulb. A fresh urine specimen is poured into the cylinder. The nurse inserts and twirls the urinometer into the cylinder. The depth of the urinometer is determined by the concentration of dissolved analytes. When the urinometer stops spinning, the nurse reads the urinometer at eye level.
The specific gravity increases with conditions that increase the loss of fluids from the body, such as diabetes mellitus, gastrointestinal fluid losses, third-space fluid accumulation, and fear or anxiety. Decreases in the specific gravity result from renal disease. When the amount of urine increases and the specific gravity decreases there is an absence of the antidiuretic hormone (ADH), usually triggered by diabetes insipidus (a disorder of the posterior pituitary gland).
Urine Glucose
When the blood levels of glucose exceed the renal threshold (180 mg/dl), glucose spills into the urine. Multiple agents are available for measuring the glucose content of urine. These agents are not as accurate a test method as blood glucose levels.
Some of the reducing agents can measure other products, such as protein and blood, along with the glucose (Clinitest and Clinistix). Each product has specific step-by-step instructions for performing the test and reading the results. Teach the client how to perform these urine tests.
Urine Ketones
Ketones are products of fatty acid metabolism and are completely metabolized by the liver under normal conditions. The most common cause of ketonuria is diabetes. However, with strenuous exercise, starvation, and sustained febrile and hypoxic conditions an increase in fatty acid metabolism causes ketoacidosis, resulting in ketone bodies in the urine.
Urine Cells and Casts
Normally the urine is free from blood cells and casts. When the renal system is impaired as in renal damage or failure, nephritis, and stones and infections in the urinary tract, the following can occur:
· Bleeding with resulting RBCs in the urine
· Accumulation of epithelial cells with cast formation
· WBCs, which indicate infections
Stool Tests
Stool analysis is used to determine the various constituents of the stool for diagnostic purposes such as diseases of the gastrointestinal tract, the liver, and the pancreas. Normal constituents of the stool are urobilinogen, porphyrins, sodium, chloride, potassium, and small amounts of nitrogen and lipids. The most frequent tests ordered on feces include leukocytes, blood, fat, ova and parasites, and pathogens.
Urobilinogen
Urobilinogen is derived from the normal bacterial action of intestinal flora on bilirubin. It is increased with severe hemolysis of RBCs and decreased with most biliary obstructions.
Occult Blood
When blood is invisible on inspection it is said to be occult; it is blood that can only be detected through a microscope or by chemical means. In the gastrointestinal tract, the digestive process acts on blood, making it occult. Random sampling for occult blood is done to diagnose gastrointestinal bleeding, ulcers, and malignant tumors. Colorectal cancer is a leading cause of cancer deaths in the United States. Most colorectal cancers begin as a polyp, a small abnormal growth of tissue, in the wall of the colon. As the polyp grows, it may cause bleeding from the rectum, blood in the stool, or a change in the shape of the stool. Screening for colorectal cancer begins with fecal occult blood testing. Cancer screening guidelines recommend annual fecal occult blood testing for adults aged 50 years and older (Mandelson, LaCroix, Anderson, Nadel, & Lee, 1999).
Any person age 50 years or older but asymptomatic are considered average risk for colorectal cancer. The risk factors increase when one or more of the following exist:
• Close relative(s) who have had colorectal cancer or an adenomatous polyp
• Family history of familial adenomatous polyposis
• Family history of hereditary nonpolyposis colorectal cancer
• History of adenomatous polyps
• History of colorectal cancer
• Inflammatory bowel disease
See the accompanying box for the complete set of guidelines for colorectal screening as developed by the American Cancer Society, the American College of Gastroenterology, and the American Society of Gastrointestinal Endoscopists. See Table 28-12 for the diagnostic procedures: colonoscopy and proctosigmoidoscopy.
When the practitioner is using occult blood to confirm suspicions of a gastrointestinal disorder, the client is placed on a 3-day diet free of meat, poultry, and fish to decrease the possibility of a false-positive result. Common drugs that can cause a positive test for occult blood are salicylate, steroids and indomethacin.
Parasites
The gastrointestinal tract can harbor parasites and their eggs (ova). Some of these parasites are harmless, whereas others cause clinical symptoms. With the exception of pinworms (which can enter the body through both the oral and anal routes), all other common parasites gain portal entry through the mouth by ingesting contaminated water or food. Roundworm, hookworm, whipworm, tapeworm, Trichinella spiralis, and Entamoeba histolytica are common parasites found in the United States.
Culture and Sensitivity Tests
Culture refers to the growing of microorganisms to identify the pathogen. Culture and sensitivity (C&S) tests are performed to identify both the nature of the invading organisms and their susceptibility to commonly used antibiotics. Sensitivity allows the practitioner to select the appropriate antibiotic therapy. All C&S specimens should be taken immediately to the laboratory.
Blood Culture
Bacteremia is bacteria in the blood. The blood culture should be obtained while the client is experiencing chills and fever. A series of three venipuncture collections are performed using strict sterile technique; change the needle after the specimen is collected before injecting the blood sample into the test tube.
Swab (Throat) Culture
The throat normally colonizes many organisms. Throat cultures serve to isolate and identify such pathogens as ß-hemolytic streptococci; Staphylococcus aureus; meningococci; gonococci; Bordetella pertussis; and Corynebacterium diphtheria. A throat swab is commonly done to identify streptococcal infections, which, if untreated, can cause rheumatic fever or glomerulonephritis.
To obtain a throat swab, use a wooden blade to depress the tongue and swab the white patches, exudate, or ulcerations of the throat with a sterile applicator. Avoid touching other parts of the mouth with the swab. Once obtained, place the applicator in a sterile container.
Sputum Culture
Sputum tests are done for culture, smear, and cytology. Sputum is created by the mucous glands and goblet cells of the tracheobronchial tree and is raised by coughing. Sputum is sterile until it reaches the throat and mouth where it comes in contact with normal flora. Sputum can be obtained by tracheobronchial suctioning and transtracheal aspiration, producing a more accurate identification of pulmonary organisms.
A sputum smear will identify the same organism found in a culture plus eosinophils, epithelial cells, and other substances. Smears are helpful in diagnosing asthma (eosinophils) and fungal infection. The specimeeeds to be refrigerated if it cannot be taken immediately to the laboratory.
Sputum can also be examined for cytology (the study of cells). It is performed to diagnose cancer of the lungs. The specimen should be collected early in the morning after a deep cough.
Urine Culture
Urinary C&S tests are performed whenever a urinary tract infection is suspected. Organisms enter the urinary system by one of two ways:
1. Ascending urinary tract infections are associated with Escherichia coli and Candida albicans from the rectum, vagina and catheterization.
2. Descending sources are caused from Staphylococcus and Streptococcus entering the urinary system from the blood.
Stool Culture
Stool C&S is performed to identify bacterial infections. If the client has diarrhea, a rectal swab can be taken as a specimen; fecal material must be visible on the swab for the laboratory to perform the test.
Wound Culture
Clinical specimens taken from abscesses or infected wounds reveal a variety of aerobic and anaerobic microorganisms. “Because anaerobic microorganisms are the preponderant microflora in humans and are consistently present in the upper respiratory, gastrointestinal, and genitourinary tracts, they are also likely to invade other parts of the body to cause severe, and sometimes fatal, infections” (Fischbach, 2000, p. 554).
Pathogens are likely to be present in the following wound specimens: pus, necrotic tissue, debrided material, postoperative wound drainage, lower-extremity ulcers, and pressure ulcers. Use standard precautions when obtaining a wound culture.
Bone Marrow
Bone marrow specimens are examined by either culture or smear for identification of microorganisms. Smear slides are prepared at the client’s bedside by the nurse.
Papanicolaou Test
Papanicolaou test (smear method of examining stained exfoliative cells), commonly called a Pap smear, is done to evaluate the cell maturity, metabolic activity, and morphologic variations of the cervical tissue. Papanicolaou testing can also be used for tissue specimens from other organs, such as bronchial aspirations and gastric secretions. Cervical Pap smear testing is recommended every 2 to 3 years after the onset of sexual activity. Annual testing is indicated for women:
· Over 40 years of age
· With a family history of cervical cancer
· With a previous positive test
To increase the accuracy of a cervical specimen, the client should be told to avoid intercourse, douches, and vaginal creams for 24 hours before the test. The vaginal speculum should not be lubricated. This test should not be performed if the client is menstruating because the specimen will be unsuitable for cytologic study.
RADIOLOGIC STUDIES
Radiography (the study of x-rays or gamma ray-exposed film through the action of ionizing radiation) is used by the practitioner to study internal organ structure.
Fluoroscopy (the immediate, serial images of the body’s structure and function) is used to demonstrate the motion of organs when used with contrast medium (a radiopaque substance that facilitates roentgen imaging of the body’s internal structures). X-rays are valuable to the practitioner in either formulating a diagnosis (e.g., pneumonia) or as a tool to determine if other studies are necessary (e.g., lung lesion requiring biopsy to differentiate between a benign or malignant tumor).
Certain radiologic tests will require a contrast medium that could interfere with other diagnostic studies. Barium and iodine are commonly used contrast media. Laboratory blood samples measuring the thyroid function should be drawn before an intravenous pyelogram (IVP) where radioactive iodine dye is administered. If the client needs both an IVP and barium enema, the IVP is done first because the barium is likely to decrease the visualization of the kidneys.
Precautions need to be taken to ensure client safety. It is essential during history taking that the client is questioned about the possibility of pregnancy, asthma, and allergic reactions to contrast media (iodine) as well as to other foods and drugs. If the client has never received iodine, this should be noted on the requisition.
Chest X-Ray
The most common radiologic study is the noninvasive, noncontrasted chest x-ray. The best results are obtained when the films are taken in the radiology department; however, a portable chest x-ray can be performed at the bedside.
Radiographic projection positions of chest x-ray films are taken from various views (Figure 28-13). Multiple views of the chest are necesary for the practitioner to assess the entire lung field. To prepare the client for a chest x-ray, remove metal objects (jewelry) and all clothing from the waist up and replace with a gown. Metal will appear on the x-ray film thereby obscuring visualization of parts of the chest. Pregnant women are draped with a metal apron to protect the fetus. Chest films can indicate the following alterations and diseases:
· Lesions (tumors, cysts, masses) in the lung tissue, chest wall, bony thorax or heart
· Inflammation of lung tissue (pneumonia, atelectasis, abscesses, tuberculosis); pleura (pleuritis); and pericardium (pericarditis)
· Fluid accumulation in the lung tissue (pulmonary edema, hemothorax); pleura (pleural effusion); and pericardium (pericardial effusion)
· Bone deformities and fractures of the rib and sternum
· Air accumulation in the lungs (chronic obstructive pulmonary disease, emphysema), and pleura (pneumothorax)
· Diaphragmatic hernia
Kidney-Ureter-Bladder
A kidney-ureter-bladder, also known as a KUB (x-ray of the abdomen), is used to visualize the kidney, ureter, and bladder and sometimes the gallbladder, liver, and spleen. The results can reveal congenital abnormalities, enlarged organs, lesions, and obstructions.
Mammography
Mammography (a low-dose radiographic study of breast tissue) is used to reveal congenital abnormalities and lesions. The American Cancer Society (1997) recommends a baseline mammogram by age 40, followed by a mammogram every 2 years until age 50, and every year after age 50.
Skeletal X-Rays
Skeletal x-rays are taken of any bony processes to reveal congenital abnormalities, fractures, joint and spine abnormalities, and degeneration (arthritis).
Computed Tomography
Computed tomography (CT) is the radiologic scanning of the body with x-ray beams and radiation detectors that transmit data to a computer that transcribes the data into quantitative measurement and multidimensional images of the internal structures. Figure 28-14 demonstrates the directions of sagittal, transverse, and coronal planes taken during CT scanning.
This procedure requires the client’s written consent. Because the client will be positioned on the scanning table and told to remain motionless, the client’s cooperation is essential during the scanning. Prepare the client with an explanation and pictures of what to expect. Figure 28-15 shows the direction of CT scan waves. A simple drawing of this figure can be used in client teaching to increase understanding of the test.
Assess the client’s ability to relax and review imagery relaxation. Sedation can be administered with an order from the practitioner. Clients who will receive a contrast medium need to be kept NPO 2 to 4 hours before the test. The client should void before the test unless the pelvic area is to be studied. A full bladder enhances visualization of the pelvic area.
Barium Studies
Barium(a chalky white contrast medium) is an oral preparation that allows for roentgenographic visualization of the internal structures of the digestive tract. The results of barium studies can reveal: congenital abnormalities; lesions; spasm, reflux, stricture, and obstruction; inflammation and ulceration; varices; and fistula. General client preparation for barium studies should include:
· Placing the client on NPO status after midnight
· Administering a laxative the evening before and enemas the morning of the test
· Forcing fluid postprocedure
· Follow-up 2 to 3 days postprocedure to ensure the client has had a normal brown stool
Postprocedure barium will be expelled in the stool, making it milky white. Fluids are forced to help with the excretion of barium. If the barium is not completely excreted, it can cause an intestinal obstruction.
Barium Swallow
Barium swallow (also called esophography) is a fluoroscopic visualization of the esophagus following the ingestion of barium sulfate. Implement the nursing care discussed above for client having a barium study.
Upper Gastrointestinal Study
Upper gastrointestinal (UGI) study is a fluoroscopic visualization of the stomach and small bowel following the ingestion of barium sulfate. In addition to the general preparation of the client for a barium study, also instruct the client:
· Not to smoke 24 hours before the procedure (smoking causes an increased production of gastric juices)
· That during the procedure (which will last approximately 2 hours) pictures will be taken at 30-minute intervals with the client in different positions
Barium Enema
Barium enema (a rectal infusion of barium sulfate) is the roentgenographic study of the lower intestinal tract. The colon should be free of all fecal material to allow for maximum visualization. Instruct the client:
· To eat a low residue diet 2 days prior to the test
· That during the procedure various positions will need to be assumed on the table to facilitate movement of the barium in the intestines
· The test will take about 1 hour.
· The postprocedure cleansing enemas will be given to help remove the barium
Angiography
Angiography allows visualization of the vascular structures through the use of fluoroscopy with a contrast medium. It is performed in radiology or diagnostic studies departments. The test reveals the blood flow to the heart, lungs, brain, kidneys, and lower extremities. It is also useful in diagnosing an aneurysm (weakness in the wall of a blood vessel).
Arteriography
Arteriography is the radiographic study of the vascular system following the injection of a radiopaque dye through a catheter. The practitioner uses fluoroscopy to thread the catheter through a peripheral artery into the area to be studied, such as the aorta or the cerebral, coronary, pulmonary, renal, iliac, femoral, or popliteal arteries. The client is placed on a cardiac monitor. Dye is injected in a vascular catheter with a rapid sequence of films to visualize the vasculature.
Cardiac Catheterization
Cardiac catheterization is a radiographic study with the use of a contrast medium injected into a vascular catheter that is threaded into the heart and coronary or pulmonary vessels. The client is placed in a supine position and connected to a cardiac monitor.
· The peripheral site, either the groin or brachial area, is prepped and injected with xylocaine. A catheter is inserted and threaded:
· Right-sided catheterization—into the right atrium, ventricle and pulmonary artery
· Left-sided catheterization—into the aorta to the coronary arteries or the left ventricle
The study includes pressure measurements, blood gas sampling, and viewing the integrity of the heart’s valves. Postcatheterization the nurse should:
· Place the client on telemetry.
· Apply manual pressure (for 30 minutes or longer) when the catheter sheath is removed, then apply a pressure dressing.
· Keep the client on bed rest with the involved extremity straight and immobile.
· Monitor and record vital signs to include the presence, quality, and character of peripheral pulses; and the color, temperature and tactile sensation of the involved extremity.
· Encourage oral fluids and record intake and output.
· Instruct the client to report any warm, tickling sensations at the puncture site that would indicate bleeding.
· Monitor for procedural complications: bleeding or hematoma formation at the site; allergic reactions; and cardiovascular, pulmonary, and neurologic changes.
Digital Subtraction Angiography
Digital subtraction angiography is a computerized imaging of the vasculature with visualization on a monitor screen after the intravenous injection of iodine through a catheter. The results reveal the presence of vascular malformations (stenosis, occlusion, obstruction, ulceration, plaques, and aneurysms), lesions, and emboli.
Lymphangiography
Lymphangiography is a radiographic study of the lymphatic system after a catheter injection of an oil-based dye. A lymphatic vessel is first identified with an intradermal injection of a blue dye into either the foot or hand depending on the area to be studied. The results reveal the presence of a lymphoma, metastatic disease, and the degree of edema in lymphatic tissue.
Venography
Venography is a radiographic study of the venous system of the lower extremities after the injection of an iodine contrast agent. A venogram reveals both the presence and degree of trauma or disease (e.g., incompetent valves) to a vein, soft tissue compression, and the presence of thrombi.
Dye Injection Studies
Iodine is a common dye used in radiographic studies. Iodine injection might cause the client to experience temporary symptoms of shortness of breath, nausea, and a warm, hot flushed sensation. Most dye injection studies are invasive, requiring written consent. General guidelines for a client receiving a dye injection study should include:
· Preprocedure—NPO 6 to 12 hours before testing.
· Postprocedure—drink 2500 ml of water daily to encourage dye excretion. Notify the practitioner of decreased urinary output, bleeding, and signs of infection.
Test findings can reveal congenital abnormalities, lesions, inflammation, stones, obstruction, and organspecific disorders.
Cholangiography
Cholangiography is the roentgenographic procedure visualizing the integrity of the biliary system by a radiopaque contrast medium. There are three methods of performing a cholangiogram: intravenous, percutaneous, and direct injection into a T-tube (an artificial drain placed in common bile duct during surgery). The client is placed NPO 8 to 12 hours before the test with a cleansing enema the evening before.
Intravenous Cholangiography
Intravenous Cholograffin (contrast agent) is administered with photographs taken every 15 to 30 minutes until the common bile ducts are visualized. If the gallbladder has not been removed, a fatty meal is given the evening before. The x-ray films are taken to show the contraction of the dye in the gallbladder.
Percutaneous Cholangiography
The percutaneous method for performing a cholangiogram requires the contrast agent to be injected directly into the liver tissue. A venous catheter or long needle is inserted into the liver tissue during fluoroscopy.
For this method, the client must have a normal prothrombin time and platelet count before the procedure.
Postprocedure the client is placed on bed rest. Assess the insertion site for bleeding. Clients are at risk for bile peritonitis. Instruct the client to report immediately to the practitioner if any of the following symptoms occur: abdominal pain, distension and rigidity; chills and fever; and nausea or vomiting.
T-Tube Cholangiography
T-tube cholaneography requires the instillation of iodine to visualize the patency of the hepatic and common bile ducts. The client is at risk for bile peritonitis.
Oral Cholecystography
Oral cholecystography is the visualization of the gallbladder and presence of stones through the administration of radiopaque iodine tablets. The evening before the test the client eats a fatty meal and takes the iodine tablets 5 minutes apart with 8 ounces of water. The number of tablets administered is based on weight.
Cystography
Cystography is a radiographic study that uses an aqueous iodine contrast agent instilled into the bladder through a urinary catheter. It is used to visualize the bladder, urethra, and ureteral openings. Postprocedure, instruct the client on how to monitor urinary output and to notify the practitioner of bleeding, decreased output, and signs of infection.
Intravenous Pyelogram
An intravenous pyelogram (IVP) is a series of x-ray films of the kidneys, ureters, and bladder following the administration of an intravenous iodine preparation. The test may reveal organ specific disorders such as hydronephrosis, polycystic disease, chronic pyelonephritis, and acute renal failure.
ULTRASONOGRAPHY
Ultrasound (echogram) is a noninvasive study that uses high-frequency sound waves to visualize deep body structures. This test should be scheduled before any studies using a contrast medium or air to ensure accuracy because an ultrasound does not require any contrast medium. The client is instructed to lie still during the procedure.
Ultrasound is used to evaluate the brain, thyroid gland, heart, vascular structure, abdominal aorta, spleen, liver, gallbladder, pancreas, and pelvis. An ultrasound is commonly done during pregnancy to evaluate the size of the fetus and placenta; a full bladder is needed to ensure visualization. Instruct the mother to drink 6 to 8 glasses of water and to avoid urination before testing.
A coupling agent (lubricant) is placed on the surface of the body area to be studied to increase the contact between the skin and the transducer (instrument that converts electrical energy to sound waves). The transducer emits waves that travel through the body tissue and are reflected back to the transducer and recorded. The varying density of body tissues deflects the waves into a differentiated pattern on an oscilloscope. Photographs can be taken of the sound wave pattern on the oscilloscope.
Echocardiograms
An echocardiogram is an ultrasonographic procedure used to reveal abnormal structure or motion of the heart wall and thrombi. This test is also used after radiofrequency ablation (the delivery of low-voltage, high-frequency alternating electrical current to cauterize the abnormal myocardial tissue) to identify the potential complications of pericardial effusion.
Doppler Ultrasonography
Doppler (a hand-held transducer) transmits high frequency sound waves to the artery or vein being studied. The sound waves strike the moving RBCs and are reflected back to the transducer, which amplifies the sound and produces a graphic recording. Doppler ultrasonography reveals blood clots and peripheral vascular disease.
MAGNETIC RESONANCE IMAGING
Magnetic resonance imaging (MRI) is an imaging technique that uses radiowaves and a strong magnetic field to make continuous cross-sectional images of the body.
The client is instructed to wear earphones to decrease the discomfort from the machine’s clanging sound. A noniodine intravenous paramagnetic contrast agent may be used during the study. The study reveals lesions and changes in the body’s organs, tissues, vascular, and skeletal structures.
RADIOACTIVE STUDIES
Radionuclide imaging (nuclear scanning) uses radionuclides (or radiopharmaceuticals) to image the morphologic and functional changes in the body’s structure. A scintigraphic scanner is placed over the area of study to detect the radiation emission and to produce a visual image of the structure on film. Radiopharmaceutical agents are administered by various routes with consideration given to time delays of absorption. The results reveal congenital abnormalities, lesions, skeletal changes, infections, and gland and organ enlargement.
ELECTRODIAGNOSTIC STUDIES
These diagnostic tests use devices to measure the electrical activity of the heart, brain, and skeletal muscles.
Electrical sensors (electrodes) are placed at certain anatomic points to measure the tone, velocity, and direction of the impulses. The impulses are then transmitted to an oscilloscope or printed on graphic paper.
Electrocardiography
An electrocardiogram (ECG or EKG) is a graphic recording of the heart’s electrical activity. The client may be asked not to smoke or drink caffeinated beverages 24 hours before the test. Nicotine and caffeine can affect the heart rate. Electrodes are applied to the chest wall and extremities. A lubricating gel applied to the electrodes increases the conduction of electrical activity between the skin and electrode. The client is instructed to lie still during the pain-free test. The test can reveal abnormal transmission of impulses and electrical position of the heart’s axis.
A portable cardiac monitor (Holter monitor) is a device that records the heart’s electrical activity. It produces a continuous recording over a specified period of time (e.g., 24 hours). The portable unit allows the client to ambulate and perform regular activities. Clients are instructed to maintain a log of activities that occur when they feel their heart beating faster or irregularly. The practitioner reviews the ECG tracing in relation to the client’s log to determine if certain activities, such as walking, are associated with abnormal transmission of impulses.
Signal-Averaged Electrocardiography
Signal-averaged electrocardiography (SAECG) is a surface ECG that amplifies late potentials (the electrical activity that occurs after normal depolarization of the ventricles). The test requires a specialized ECG machine and small computer to detect the late potentials. It is performed on clients who have had a myocardial infarction. The test reveals the client’s risk for ventricular tachycardia.
Stress Test
A stress test measures the client’s cardiovascular response to exercise tolerance. It demonstrates the ability of the myocardium to respond to increased oxygen requirements (the result of exercise) by increasing the blood flow to the coronary arteries.
The client is connected to an ECG machine and asked to walk on a treadmill. Continuous ECG recordings are made of the client’s heart response (rate, electrical activity, and cardiac recovery time) to frequent changes in the treadmill’s speed and slope. The test is stopped immediately if the client experiences any symptoms of decreased cardiac output (chest pain, dyspnea, fatigue, or ischemic changes on the ECG monitor).
Electroencephalography
An electroencephalogram (EEG) is the graphic recording of the brain’s electrical activity. The procedure is painless and takes about an hour. The test is performed in a quiet, nonstimulating environment. It can reveal the presence and type of seizure disorder and intracranial lesion. The absence of brain’s electrical activity is used to confirm death.
During the procedure, electrodes are placed on the client’s scalp. The electrodes transmit the impulses from the brain to an EEG machine. The machine amplifies the brain’s impulses and makes a recording of the waves on strips of paper.
ENDOSCOPY
Endoscopy is the visualization of a body organ or cavity through a scope. The procedure is performed with an endoscope (a metal or fiberoptic tube) being inserted directly into the body structure to be studied (see Figure 28-16). A light at the end of the scope allows the practitioner to assess for lesions and structural problems. The endoscope has an opening at the distant tip that allows the practitioner to administer an anesthetic agent, lavage, suction, and biopsy tissue. Common endoscopic procedures are presented in Table 28-12.
General client preparation and positioning depend on the structure being studied as discussed in Table 28-12. As with all invasive procedures, the client needs to sign a consent form and the nurse needs to establish baseline vital signs before administering sedative agents.
Postprocedure the nurse monitors the vital signs, observes for bleeding, and assesses for procedural risks (e.g., return of the gag and swallowing reflexes following an esophagogastroduodenoscopy with local anesthesia).
ASPIRATION/BIOPSY
Aspiration is performed to withdraw fluid that has abnormally collected or to obtain a specimen. Aseptic technique and Standard Precautions are used during aspiration. Aspiration diagnostic studies are invasive; implement the protocols for diagnostic tests. A local anesthetic is administered in the area being studied to decrease the client’s discomfort when the skin is pierced by the needle.
A stylet needle with an outer, hollow-bore needle is used to pierce the skin. Once the needle is in place, the stylet is withdrawn, leaving only the outer needle to aspirate the fluid. A tissue biopsy (excision of a small amount of tissue) can be obtained during aspiration or with other diagnostic tests (e.g., bronchoscopy). A biopsy can be taken from most of the body’s tissue.
Bone Marrow Aspiration/Biopsy
The sternum and iliac crest are the common sites for bone marrow puncture. During a bone marrow puncture a fluid specimen (aspiration) or a core of marrow cells (biopsy) can be obtained. Both tests are commonly done concurrently to obtain the best marrow specimen.
The test can reveal anemias or cancer, such as leukemia, multiple myeloma, or Hodgkin’s disease, or the client’s response to chemotherapy.
There are no restrictions on fluids or food before the puncture. The nurse should explain the procedure to elicit the client’s support during the procedure. The client must lay perfectly still throughout the procedure. The client is usually fearful; allay the client’s fear with relaxation methods or sedation. Infants and small children are restrained by holding them throughout the procedure.
Client positioning is determined by the site to be used, supine (sternum) or side-lying (iliac crest). The site is prepped for puncture to decrease the skin’s normal flora. Explain to the client that pressure may be experienced as the specimen is withdrawn. The client should not move when the specimen is being withdrawn; a sudden movement may dislodge the needle.
Postprocedure the client should be on bed rest for an hour. The nurse monitors vital signs to assess for bleeding (rapid pulse rate, low blood pressure). Instruct the client to report to the practitioner any bleeding or signs of inflammation.
Paracentesis
Paracentesis is the aspiration of fluid from the abdominal cavity. This test can either be diagnostic, therapeutic, or both. For instance, with endtage liver or renal disease there is ascites (an accumulation of fluid in the abdomen). Pressure caused from the ascites can interfere with breathing and gastrointestinal functioning.
Aspiration in this instance is therapeutic. If a culture specimen is taken, it is also diagnostic.
Have the client void and obtain a body weight before the procedure. Place the client in a high Fowler’s position in a chair or sitting on the side of the bed. The skin is prepped, anesthetized, and punctured with a trocar (a large-bored abdominal paracentesis needle). The trocar is held perpendicular to the abdominal wall and advanced into the peritoneal cavity. When fluid appears, the trocar is removed, leaving the inner catheter in place to drain the fluid. Observe the client for pressure changes that can result from the rapid removal of fluid.
Postprocedure apply a sterile dressing to the puncture site. Monitor the client for changes in vital signs and electrolytes. Instruct the client to record the color, amount, and consistency of drainage on the dressing after discharge.
Thoracentesis
Thoracentesis is the aspiration of fluids from the pleural cavity. The pleural cavity normally contains a small amount of fluid to lubricate the lining between the lungs and pleura. Infection, inflammation, and trauma may cause an increased production of fluid, which can impair ventilation.
Position the client with arms crossed and resting on a bedside table to allow access to the rib cage (Figure 28-17). Instruct the client not to cough during insertion of the needle. The practitioner selects, preps, and anesthetizes the puncture site. The needle is usually inserted into the intercostal space at the location of maximum dullness to percussion. Posteriorly, the site should be above the ninth rib, and laterally, above the seventh rib During the procedure, monitor the client for symptoms of a pneumothorax (collection of air or gas in the pleural space causing the lungs to collapse), such as dyspnea, pallor, tachycardia, vertigo, and chest pain.
Postprocedure observe for cardiopulmonary changes and a mediastinum shift as assessed by vital signs and bloody sputum.
Cerebrospinal Fluid Aspiration
Lumbar puncture (“spinal tap”) is the aspiration of CSF from the subarachnoid space. The specimen is examined for organisms, blood, and tumor cells. A spinal tap is also performed:
· To obtain a pressure measurement when blockage is suspected
· During a myelogram, as discussed earlier
· To instill medications (anesthesia, antibiotics, or chemotherapy)
A spinal tap is contraindicated in clients with increased intracranial pressure, hemorrhagic diathesis, and an infection at the proposed puncture site. Place the client in a lateral recumbent position with the craniospinal axis parallel to the floor and flat of the back perpendicular to the procedure table. Have the client assume a flexed knee-chest position to bow the back. This position separates the vertebrae. Most clients will require assistance in maintaining this position throughout the procedure. To assist, the nurse stands facing the client with one hand across the client’s posterior shoulder blades and the other hand over the buttocks.
The practitioner selects, preps, and anesthetizes the puncture site (usually interspace L3-L4, L4-L5, or L5-S1). The needle and stylet are inserted into the midsagittal space and advanced through the longitudinal subarachnoid space (Figure 28-18).
Once in the subarachnoid space, the stylet is removed, leaving the needle in place. An initial CSF pressure reading is taken:
· A three-way stopcock with a manometer (calibrated column) is securely connected to the spinal needle.
· The stopcock is opened toward the manometer to allow the CSF to rise in the column. Under normal conditions, the CSF will fluctuate in the column with respirations.
· When the CSF stabilizes, a pressure reading is taken.
If the pressure reading is greater than 200 mm H2O or falls quickly, only 1 or 2 ml CSF is obtained for analysis. If the pressure is less than 200 mm H2O, an adequate specimen sampling is withdrawn slowly.
After the pressure reading is taken, the stopcock is turned to allow the CSF to slowly flow into a sterile test tube. A sterile cap is placed on the test tube, and the sample is transported to the laboratory for analysis. Rapid withdrawal of CSF can cause a transient postural headache. Throughout the procedure, monitor the client’s cardiorespiratory status.
Postprocedure, pressure is applied and then a sterile bandage. Assess the bandage for leakage of CSF and the client’s neurologic and cardiorespiratory status. A postural headache is the most common complication of a lumbar puncture; using a small-bore spinal needle minimizes the chances of a headache.
