Capillary Puncture Equipment and Procedures PDF

CHAPTER 10 Capillary Puncture Equipment and Procedures KEY TERMS Do the Key Term Matching exercise in the WORKBOOK to gain familiarity with these terms. arterialized hypothyroidism osteochondritis blood film/smear interstitial fluid osteomyelitis calcaneus intracellular fluid PKU CBGs lancet plantar su...

CHAPTER 10 Capillary Puncture Equipment and Procedures KEY TERMS Do the Key Term Matching exercise in the WORKBOOK to gain familiarity with these terms. arterialized hypothyroidism osteochondritis blood film/smear interstitial fluid osteomyelitis calcaneus intracellular fluid PKU CBGs lancet plantar surface cyanotic microcollection containers posterior curvature differential microhematocrit tubes whorls feather newborn/neonatal screening galactosemia OBJECTIVES Upon successful completion of this chapter, the reader should be able to: 1 Define the key terms and abbreviations listed at the beginning of this chapter. 2 List and describe the various types of equipment needed for capillary specimen collection. 3 Describe the composition of capillary specimens, identify which tests have different reference values when collected by capillary puncture methods, and name tests that cannot be performed on capillary specimens. 4 Identify indications for performing capillary puncture on adults, children, and infants. 5 List the order of draw for collecting capillary specimens. 6 Describe the proper procedure for selecting the puncture site and collecting capillary specimens from adults, infants, and children. 7 Describe how both routine and thick blood smears are made and the reasons for making them at the collection site. 8 Explain the clinical significance of capillary blood gas, neonatal bilirubin, and newborn screening tests and describe how specimens for these tests are collected. 320 UNIT III: BLOOD COLLECTION PROCEDURES OVERVIEW Drops of blood for testing can be obtained by puncturing or making an incision in the capillary bed in the dermal layer of the skin with a lancet, other sharp device, or laser. Terms typically used to describe this technique include capillary, dermal, or skin puncture, regardless of the actual type of device or method used to penetrate the skin, and the specimens obtained are respectively referred to as capillary, dermal, or skin puncture specimens. (To best reflect the nature and source of the specimen, and for simplification and consistency, the terms capillary specimen and capillary puncture are used in this chapter.) With the advent of laboratory instrumentation capable of testing small sample volumes, specimens for many laboratory tests can now be collected in this manner. This chapter covers capillary equipment, principles, collection sites, and procedures. Although steps may differ slightly, procedures in this chapter conform to CLSI Standards. KEY POINT Capillary specimen collection is especially useful for pediatric patients in whom removal of larger quantities of blood can have serious consequences. Capillary Puncture Equipment In addition to blood collection supplies and equipment described in Chapter 7, the following special equipment may be required for skin puncture procedures. LANCETS/INCISION DEVICES A lancet is a sterile, disposable, sharp-pointed or bladed instrument that either punctures or makes an incision in the skin to obtain capillary blood specimens for testing. Lancets are available in a range of lengths and depths to accommodate various specimen collection requirements. Selection depends on the age of the patient, collection site, volume of specimen required, and the puncture depth needed to collect an adequate specimen without injuring bone. Lancets are specifically designed for either finger puncture (Fig. 10-1), or heel puncture (Fig. 10-2), and must have OSHA-required safety features. KEY POINT An important OSHA required lancet safety feature is a permanently retractable blade or needle point to reduce the risk of accidental sharps injury. LASER LANCETS Several companies make devices that perforate the skin with a laser instead of a sharp instrument. A laser typically vaporizes water in the skin to produce a small hole in the capillary bed without cauterizing delicate capillaries. Because no sharp instrument is involved, there is no risk of accidental sharps injury, and no need for sharps disposal. The Lasette® (Fig 10-1C) (Beijing Sincoheren Science & Technology Developing Co., Ltd, Beijing, China) has single-use, disposable inserts to prevent cross-contamination between patients. It is cleared by the FDA for use on the fingers of adults and children 5 years of age and older. Use on children younger than 5 years of age is subject to a physician’s discretion. MICROCOLLECTION CONTAINERS Microcollection containers (Fig. 10-3), also called microtubes, are special small plastic tubes used to collect the tiny amounts of blood obtained from capillary punctures. They are often referred to as “bullets” because of their size and shape. Some come fitted with narrow plastic capillary tubes (Fig. 10-3B) to facilitate specimen collection. Most have color-coded bodies or stoppers that correspond to color-coding of ETS blood collection tubes, and markings for CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 321 A B C D Figure 10-1 Several types of finger puncture lancets. A. BD Microtainer® Contact Activated Lancets (Courtesy Becton Dickinson, Franklin Lakes, NJ). B. Tenderlett® Toddler, Junior, and Adult lancets (Courtesy ITC, Edison, NJ). C. Capiject® Safety Lancets. (Courtesy Terumo Medical Corp., Somerset, NJ). D. ACCU-CHEK® Safe-T-Pro Plus lancet with three depth settings (Roche Diagnostics, Indianapolis, IN). E. Lasette® laser lancet (Photo courtesy lancet developer Cell Robotics, Lasette now owned by Beijing Sincoheren Science & Technology Developing Co., Ltd, Beijing, China). E A B Figure 10-2 Several types of heel puncture lancets. A. BD QuikHeel® infant lancet, also available in a preemie version (Courtesy Becton Dickinson, Franklin Lakes, NJ). B. Tenderfoot® toddler (pink), newborn (pink/blue), preemie (white), and micro-preemie (blue) heel incision devices (Courtesy ITC, Edison, NJ). 322 UNIT III: BLOOD COLLECTION PROCEDURES A B D C E ® Figure 10-3 Examples of microcollection containers. A. Microtainers (Courtesy Becton Dickinson, Franklin Lakes, NJ). B. MiniCollect® Capillary Blood Collection Tubes (Courtesy of Greiner Bio-One International AG, Kremsmunster, Austria). C. Capiject® EDTA Capillary Blood Collection Tube (Terumo, Somerset, NJ). D. Samplette™ capillary blood collection collectors (Courtesy Tyco Healthcare, Kendall, Mansfield, MA). E. BD Microtainer®MAP (Courtesy Becton Dickinson, Franklin Lakes, NJ). minimum and maximum fill levels that are typically measured in microliters (μL) ,such as 250 μL and 500 μL, respectively (Fig. 10-3C). A relatively new microtube, the BD Microtainer® MAP (Fig. 10-3E) has a penetrable septum for use with automated hematology systems. Some manufacturers print lot numbers and expiration dates on each tube. CAUTION: Sometimes venous blood obtained by syringe during difficult draw situations is put into microcollection containers. When this is done, the specimen must be labeled as venous blood. Otherwise, it will be assumed to be a capillary specimen, which may have different reference ranges. MICROHEMATOCRIT TUBES AND SEALANTS Microhematocrit tubes (Fig. 10-4) are disposable, narrow-bore plastic or plastic-clad glass capillary tubes that fill by capillary action and typically hold 50 to 75 μL of blood. They are used primarily for manual hematocrit (Hct), also called packed cell volume (PVC), determinations. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 323 Figure 10-4 Plastic Clad Microhematocrit tubes (Courtesy Becton Dickinson, Franklin Lakes, NJ). The tubes come coated with ammonium heparin, for collecting Hct tubes directly from a capillary puncture, or plain, to be used when an Hct tube is filled with blood from a lavender-top tube. Heparin tubes typically have a red or green band on one end; nonadditive tubes have a blue band. Smaller microhematocrit tubes designed for use with special microcentrifuges, such as those available from StatSpin, Inc. (Norwood, MA), require as little as 9 μL of blood and are often used in infant and child anemia screening programs and pediatric clinics. Plastic or clay sealants that come in small trays are used to seal one end of microhematocrit tubes. Traditionally, the dry end of the tube was inserted into the clay to plug it. Because of safety concerns, it is now recommended that sealing methods be used that do not require manually pushing the tube into the sealant or products be used that measure Hct without centrifugation. CAPILLARY BLOOD GAS EQUIPMENT The following special equipment (Fig. 10-5) is used to collect capillary blood gas (CBG) specimens: CBG collection tubes: CBG collection tubes are long thin narrow-bore capillary tubes. They are normally plastic for safety and are available in a number of different sizes to accommodate volume requirements of various testing instruments. The most common Figure 10-5 Capillary blood gas collection equipment displayed with arterial blood gas syringes. (Courtesy Sarstedt, Inc., Newton, NC.) 324 UNIT III: BLOOD COLLECTION PROCEDURES Figure 10-6 An infant heel warmer. CBG tubes are 100 mm in length with a capacity of 100 μL. A color-coded band identifies the type of anticoagulant that coats the inside of the tube; it is normally green, indicating sodium heparin. Stirrers: Stirrers are small metal filings (often referred to as “fleas”) or small metal bars that are inserted into the tube after collection of a CBG specimen to aid in mixing the anticoagulant. Magnet: Both ends of a CBG tube are sealed immediately after specimen collection to prevent exposure to air, and a magnet is used to mix the specimen. The magnet typically has an opening in the center or side so that it can be slipped over the capillary tube and moved back and forth along the tube length, pulling the metal stirrer with it, and mixing the anticoagulant into the blood specimen. Plastic caps: Plastic end caps or closures are used to seal CBG tubes and maintain anaerobic conditions in the specimen. CBG tubes typically come with their own caps. MICROSCOPE SLIDES Glass microscope slides are occasionally used to make blood films for hematology determinations. (See Chapter 7, General Blood Collection Equipment and Supplies.) When you finish the chapter, have fun seeing how many types of equipment you can identify from among the crossword clues in the WORKBOOK. WARMING DEVICES Warming the site increases blood flow as much as seven times. This is especially important when performing heelsticks on newborns. Heel-warming devices (Fig. 10-6) are commercially available. To avoid burning the patient, the devices provide a uniform temperature that does not exceed 42°C. A towel or diaper dampened with warm tap water can also be used to wrap a hand or foot before skin puncture. However, care must be taken not to get the water so hot that it scalds the patient. Capillary Puncture Principles COMPOSITION OF CAPILLARY SPECIMENS Capillary specimens are a mixture of arterial, venous, and capillary blood, along with interstitial fluid (fluid in the tissue spaces between the cells) and intracellular fluid (fluid within the cells) from the surrounding tissues. Because arterial blood enters the capillaries under pressure, capillary blood contains a higher proportion of arterial blood than venous blood and therefore more closely resembles arterial blood in composition. This is especially true if the area has been warmed, because warming increases arterial flow into the area. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 325 REFERENCE VALUES Because the composition of capillary blood differs from that of venous blood, reference (normal) values may also differ. For example, the concentration of glucose is normally higher in capillary blood specimens, whereas total protein (TP), calcium (Ca2+), and potassium (K+), concentrations are lower. KEY POINT Although potassium values are normally lower in properly collected skin puncture specimens, levels may be falsely elevated if there is tissue fluid contamination or hemolysis of the specimen. INDICATIONS FOR CAPILLARY PUNCTURE A properly collected capillary specimen can be a practical alternative to venipuncture when small amounts of blood are acceptable for testing. Capillary puncture can be an appropriate choice for adults and older children under the following circumstances: Available veins are fragile or must be saved for other procedures such as chemotherapy. Several unsuccessful venipunctures have been performed and the requested test can be collected by capillary puncture. The patient has thrombotic or clot-forming tendencies. The patient is apprehensive or has an intense fear of needles. There are no accessible veins (e.g. the patient has IVs in both arms or the only acceptable sites are in scarred or burned areas). To obtain blood for POCT procedures such as glucose monitoring Capillary puncture is the preferred method of obtaining blood from infants and very young children for the following reasons: Infants have a small blood volume; removing quantities of blood typical of venipuncture or arterial puncture can lead to anemia. According to studies, for every 10 mL of blood removed, as much as 4 mg of iron is also removed. Large quantities removed rapidly can cause cardiac arrest. Life is threatened if more than 10% of a patient’s blood volume is removed at once or over a short period. Obtaining blood from infants and children by venipuncture is difficult and may damage veins and surrounding tissues. Puncturing deep veins can result in hemorrhage, venous thrombosis, infection, and gangrene. An infant or child can be injured by the restraining method used while performing a venipuncture. Capillary blood is the preferred specimen for some tests, such as newborn screening tests. CAUTION: Capillary puncture is generally not appropriate for patients who are dehydrated or have poor circulation to the extremities from other causes, such as shock, because specimens may be hard to obtain and may not be representative of blood elsewhere in the body. TESTS THAT CANNOT BE COLLECTED BY CAPILLARY PUNCTURE Although today’s technology allows many tests to be performed on very small quantities of blood, and a wide selection of devices are available to make collection of skin puncture specimens relatively safe and easy, some tests cannot be performed on skin puncture specimens. These include most erythrocyte sedimentation rate methods, coagulation studies that require plasma specimens, blood cultures, and tests that require large volumes of serum or plasma. 326 UNIT III: BLOOD COLLECTION PROCEDURES CAUTION: Although light blue top microtubes are available from some manufacturers, they are not to be used for capillary specimens. They are intended to be used for venous blood collected by syringe in difficult draw situations. ORDER OF DRAW The order of draw for collecting multiple specimens by capillary puncture is not the same as for venipuncture. Puncturing the skin releases tissue thromboplastin, which activates the coagulation process in the blood drops. Specimens must be collected quickly to minimize the effects of platelet clumping and microclot formation and to ensure that an adequate amount of specimen is collected before the site stops bleeding. Hematology specimens are collected first because they are most affected by the clotting process. Serum specimens are collected last because they are supposed to clot. The CLSI order of draw for capillary specimens is as follows: Blood gas specimens (CBGs) EDTA specimens Other additive specimens Serum specimens KEY POINT Specimens for newborn screening tests should be collected separately. Capillary Puncture Steps Capillary punctures have the same general steps regardless of whether they are fingersticks or heelsticks. The first four steps are the same as Chapter 8 venipuncture steps 1 through 4. STEP 1: REVIEW AND ACCESSION TEST REQUEST STEP 2: APPROACH, IDENTIFY, AND PREPARE PATIENT STEP 3: VERIFY DIET RESTRICTIONS AND LATEX SENSITIVITY STEP 4: SANITIZE HANDS AND PUT ON GLOVES STEP 5: POSITION PATIENT Position is important to patient comfort and the success of specimen collection. For finger punctures, the patient’s arm must be supported on a firm surface with the hand extended and palm up. A young child is typically held in the lap by a parent or guardian who restrains the child with one arm and holds the child’s arm steady with the other. For heel punctures, an infant should be supine (lying face up) with the foot lower than the torso so the force of gravity can assist blood flow. Confirm that you know how to select a safe site by doing WORKBOOK Labeling Exercises 10-1 and 10-2. STEP 6: SELECT THE PUNCTURE/INCISION SITE General site selection criteria include one that is warm, pink or normal color, and free of scars, cuts, bruises, or rashes. It should not be cyanotic (bluish in color), edematous (swollen), or infected. Swollen or previously punctured sites should be avoided, because accumulated tissue fluid can contaminate the specimen and negatively affect test results. Specific locations for capillary puncture include fingers of adults and heels of infants. Adults and Older Children The CLSI recommended site for capillary puncture on adults and children older than 1 year is the palmar surface of the distal or end segment of the middle or ring finger of the nondominant hand. (Fingers on the nondominant hand are typically less calloused.) The puncture site CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 327 Site This Not this Figure 10-7 The recommended site and direction of finger puncture. should be in the central, fleshy portion of the finger, slightly to the side of center and perpendicular to the grooves in the whorls (spiral pattern) of the fingerprint (Fig. 10-7). Finger puncture precautions are summarized and explained in Box 10-1. KEY POINT Some texts refer to the end segment of the finger as the distal phalanx. This is not to be confused with the use of the term phalanx (pl. phalanges) for finger bone. CAUTION: According to CLSI standards, capillary puncture must not be performed on the fingers or earlobes of newborns or other infants under 1 year of age. BOX 10-1 FINGER PUNCTURE PRECAUTIONS Do not puncture fingers of infants and children under 1 year of age. The amount of tissue between skin surface and bone is so small that bone injury is very likely. Infection and gangrene have been identified as complications of finger punctures in newborns. Do not puncture fingers on the same side as a mastectomy without consultation with the patient’s physician. The arm on the same side as a mastectomy is susceptible to infection, and effects of lymphostasis can lead to erroneous results. Do not puncture parallel to the grooves or lines of the fingerprint. A parallel puncture will allow blood to run down the finger rather than form a rounded drop, and make collection difficult. Do not puncture the fifth or little (pinky) finger. The tissue between skin surface and bone is thinnest in this finger, and bone injury is likely. Do not puncture the index finger. It is usually more calloused and harder to puncture. It is also more sensitive so the puncture can be more painful; and, because that finger is typically used more, a patient may notice the pain longer. Do not puncture the side or very tip of the finger. The distance between the skin surface and the bone is half as much at the side and tip as it is in the central fleshy portion of the end of the finger. Do not puncture the thumb. It has a pulse, indicating an artery in the puncture area, and the skin is generally thicker and more calloused, making it difficult to obtain a good specimen. 328 UNIT III: BLOOD COLLECTION PROCEDURES 0 mm Vascular bed Rich in capillary loops from 0.35 mm to 0.82 mm in depth 1 mm Pain fibers Pain fibers increase in abundance below 2.4 mm 2 mm Figure 10-8 A cross-section of full-term infant’s heel showing lancet penetration depth needed to access the capillary bed. Infants Do Matching 10-3 in the WORKBOOK to test your knowledge of heel puncture precautions. The heel is the recommended site for collection of capillary puncture specimens on infants less than 1 year of age. However, it is important to perform the puncture in an area of the heel where there is little risk of puncturing the bone. Puncture of the bone can cause painful osteomyelitis (os’te-o-mi’el-i’tis), inflammation of the bone marrow and adjacent bone, or osteochondritis (os’te-o-kon-dri’tis), inflammation of the bone and cartilage, as a result of infection. Additional punctures through a previous puncture site that is inflamed can spread an infection. Studies have shown that the calcaneus (kal-ka’ne-us) or heel bone of small or premature infants may be as little as 2.0 mm below the skin surface on the plantar or bottom surface of the heel and half that distance at the posterior curvature (back) of the heel. Punctures deeper than this may cause bone damage. The vascular or capillary bed (Fig. 10-8) in the skin of a newborn is located at the dermal–subcutaneous junction between 0.35 and 1.6 mm beneath the skin surface, so punctures 2.0 mm deep or less will provide adequate blood flow without risking bone injury. KEY POINT Pain fibers increase in abundance below the capillary bed, so deeper punctures are more painful. According to CLSI, to avoid puncturing bone the only safe areas for heel puncture are on the plantar surface of the heel, medial to an imaginary line extending from the middle of the great toe to the heel or lateral to an imaginary line extending from between the fourth and fifth toes to the heel (Fig. 10-9). Punctures in other areas risk bone, nerve, tendon, and cartilage injury. Heel puncture precautions are summarized in Box 10-2. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 329 Figure 10-9 An infant heel. Shaded areas indicated by arrows represent recommended safe areas for heel puncture. Memory Jogger One way to remember that the safe areas for heel puncture are the medial or lateral plantar surfaces of the heel is to think of the phrase “Make little people happy.” Using the first letter of each word, “M” stands for medial, “L” stands for lateral, “P” stands for plantar, and “H” stands for heel. STEP 7: WARM THE SITE IF APPLICABLE Warming increases blood flow up to sevenfold and, except for PaO2 levels, does not significantly alter results of routinely tested analytes. Increased blood flow makes specimens easier and faster to obtain and reduces the tendency to compress or squeeze the site, which can contaminate the specimen with tissue fluid and hemolyze red blood cells. Because the increase is caused by arterial flow into the area, a specimen obtained from a warmed site is described as being arterialized. Consequently, warming the site is essential when collecting capillary pH or blood gas specimens. Warming is typically recommended for heelstick procedures because infants normally have high red blood cell counts and other factors that result in relatively thick blood that flows slowly. Warming may also be required before fingersticks when patients have cold hands. Warming can be accomplished by wrapping the site for 3 to 5 minutes with a BOX 10-2 HEEL PUNCTURE PRECAUTIONS Do not puncture any deeper than 2.0 mm. Deeper punctures risk injuring the bone, even in the safest puncture areas. Do not puncture areas between the imaginary boundaries. The calcaneus may be as little as 2.0 mm deep in this area. Do not puncture in the arch and any areas of the foot other than the heel. Arteries, nerves, tendons, and cartilage in these areas can be injured. Do not puncture severely bruised areas. It is painful, and impaired circulation or byproducts of the healing process can negatively affect the specimen. Do not puncture the posterior curvature of the heel. The bone can be as little as 1 mm deep in this area. Do not puncture through previous puncture sites. This can be painful and can spread previously undetected infection. Do not puncture a site that is swollen. Excess tissue fluid in the area could contaminate the specimen. 330 UNIT III: BLOOD COLLECTION PROCEDURES washcloth, towel, or diaper that has been moistened with comfortably warm water or using a commercial heel warming device. CAUTION: The temperature of the material used to warm the site must not exceed 42°C (108°F) because higher temperatures can burn the skin, especially the delicate skin of an infant. STEP 8: CLEAN AND AIR-DRY SITE The collection site must be cleaned with an antiseptic before puncture, so that skin flora (microorganisms on the skin) do not infiltrate the puncture wound and cause infection. The CLSI-recommended antiseptic for cleaning a capillary puncture site is 70% isopropanol. CAUTION: Do not use povidone–iodine to clean skin puncture sites because it greatly interferes with a number of tests, most notably bilirubin, uric acid, phosphorus, and potassium. Memory Jogger Help remember the tests affected by povidone–iodine by associating them with the word BURPP, where “B” stands for bilirubin, “UR” stands for uric acid, and the two “Ps” stand for phosphorous and potassium. After cleaning, allow the site to air-dry to ensure maximum antiseptic action and minimize the chance of alcohol contamination of the specimen. Residual alcohol, in addition to causing a stinging sensation, causes rapid hemolysis of red blood cells. It has also been shown to interfere with glucose testing. STEP 9: PREPARE EQUIPMENT Gloves are put on at this point if not put on in step 4. Select collection devices according to the tests that have been ordered and place them within easy reach, along with several layers of gauze or gauze-type pads. Select a new, sterile lancet/incision device according to the site selected, age of the patient, and amount of blood to be collected. Prepare equipment in view of the patient or guardian to provide assurance that it is new and being handled aseptically. Verify lancet sterility by checking to see that packaging is intact before opening. Open the package or protective cover in an aseptic manner and do not allow the device opening to rest or brush against any nonsterile surface. If the lancet/incision device has a protective shield or locking feature that prevents accidental activation, remove or release it per manufacturer’s instructions. Hold the device between the thumb and index fingers or as described by the manufacturer. STEP 10: PUNCTURE THE SITE AND DISCARD LANCET Finger Puncture Grasp the patient’s finger between your nondominant thumb and index finger. Hold it securely in case of sudden movement. Place the lancet device flat against the skin in the central, fleshy pad of the finger, slightly to the side of center and perpendicular to the fingerprint whorls as described in step 6. KEY POINT With very young children it is usually best to grasp three or four of the child’s fingers (Fig. 10-10) between your fingers and thumb. If you grasp only one finger, the child may twist it trying to pull away. Although you are holding more fingers, it is still easy to puncture the middle finger because it is normally the longest and sticks out farthest. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 331 Figure 10-10 Holding a toddler’s fingers prior to capillary puncture (Courtesy ITC, Edison, NJ). Heel Puncture Grasp the foot gently but firmly with your nondominant hand. Encircle the heel by wrapping your index finger around the arch and your thumb around the bottom. Wrap the other fingers around the top of the foot. Place the lancet flat against the skin on the medial or lateral plantar surface of the heel. Follow manufacturer’s instructions for direction of puncture. KEY POINT Most manufacturers of heel incision devices recommend puncturing the heel at a 90-degree angle to the length of the foot. This creates a “gap” puncture (i.e., a puncture that opens when pressure is applied). Both Finger Puncture and Heel Puncture Use sufficient pressure to keep the device in place without deeply compressing the skin. Warn the patient (or patient’s parent or guardian) of impending puncture, and activate the release mechanism to trigger the puncture. Remove the device from the skin immediately following puncture and discard it in a sharps container. STEP 11: WIPE AWAY THE FIRST BLOOD DROP Position the site downward and apply gentle pressure toward the site to encourage blood flow. Wipe away the first drop of blood with a dry gauze pad. The first drop is typically contaminated with excess tissue fluid, and may contain alcohol residue that can hemolyze the specimen and also keep the blood from forming a well-rounded drop. In addition, there have been reports of isopropyl alcohol contamination causing errors in blood glucose testing. KEY POINT Some POCT instruments may allow use of the first drop, so follow manufacturer’s instructions. STEP 12: FILL AND MIX TUBES/CONTAINERS IN ORDER OF DRAW Continue to position the site downward to enhance blood flow and apply gentle, intermittent pressure to tissue surrounding a heel puncture site or proximal to a finger puncture site. CAUTION: Do not squeeze, use strong repetitive pressure, or “milk” the site, as hemolysis and tissue fluid contamination of the specimen can result. Collect subsequent blood drops using devices appropriate for the ordered tests. Collect slides, platelet counts, and other hematology specimens first to avoid the effects of platelet aggregation (clumping) and clotting. Collect other anticoagulant containers next, and serum specimens last according to the CLSI order of draw for capillary specimens. 332 UNIT III: BLOOD COLLECTION PROCEDURES To fill a collection tube or device, touch it to the drop of blood formed on the surface of the skin. If making a blood film, touch the appropriate area of the slide to the blood drop. A microhematocrit or narrow-bore capillary tube will fill automatically by “capillary” action if held in a vertical position above, or a horizontal position beside, the blood drop while touching one end to the blood drop. While maintaining contact with the blood drop, the opposite end of the tube may need to be lowered slightly and brought back into position now and then as it fills. Do not remove the tube from the drop or continually hold or tip the tube below the site. This can result in air spaces in the specimen that cause inaccurate test results. When the tube is full, plug the opposite (or dry end) with clay or other suitable sealant. To fill a microcollection container or microtube, hold it upright just below the blood drop. Touch the tip of the tube’s “scoop” to the drop of blood and allow the blood to run down the inside wall of the tube. The scoop should touch only the blood and not the surface of the skin. This allows blood to be collected before it runs down the surface of the finger or heel. CAUTION: Do not use a scooping motion against the surface of the skin and attempt to collect blood as it flows down the finger. Scraping the scoop against the skin activates platelets, causing them to clump, and can also hemolyze the specimen. You may need to tap microtubes gently now and then to encourage the blood to settle to the bottom. When filled to an appropriate level, seal containers with the covers provided. Mix additive microtubes by gently inverting them 8 to 10 times or per manufacturer’s instructions. If blood flow stops and you are unable to collect sufficient specimen, the procedure may be repeated at a new site with a new lancet. CAUTION: Pay strict attention to fill levels of microtubes containing anticoagulants. Excess anticoagulant in underfilled microtubes can negatively affect test results. Overfilling can result in the presence of microclots in the specimen or even complete clotting of the specimen. STEP 13: PLACE GAUZE AND APPLY PRESSURE After collecting specimens, apply pressure to the site with a clean gauze pad until bleeding stops. Keep the site elevated while applying pressure. An infant’s foot should be elevated above the body while pressure is applied. STEP 14: LABEL SPECIMEN AND OBSERVE SPECIAL HANDLING INSTRUCTIONS Label the specimens with the appropriate information (see Chapter 8). Include nature and source of specimen according to facility policy. Label in view of the patient/guardian, and affix labels directly to microcollection containers. Microhematocrit tubes can be placed in a nonadditive tube or an appropriately sized aliquot tube and identifying information written on the label; or follow laboratory protocol. Follow any special handling required, such as cooling in crushed ice (e.g., ammonia), transportation at body temperature (e.g., cold agglutinin), or light protection (e.g., bilirubin). STEP 15: CHECK THE SITE AND APPLY BANDAGE The site must be examined to verify that bleeding has stopped. If bleeding persists beyond 5 minutes, notify the patient’s nurse or physician. If bleeding has stopped and the patient is CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 333 an older child or adult, apply a bandage and advise the patient to keep it in place for at least 15 minutes. CAUTION: Do not apply bandages to infants and children under 2 years of age because they pose a choking hazard. In addition, bandage adhesive can stick to the paper-thin skin of newborns and tear it when the bandage is removed. STEP 16: DISPOSE OF USED AND CONTAMINATED MATERIALS Equipment packaging and bandage wrappers are normally discarded in the regular trash. Some facilities require contaminated items, such as blood-soaked gauze, to be discarded in biohazard containers. Follow facility protocol. STEP 17: THANK PATIENT, REMOVE GLOVES, AND SANITIZE HANDS Thanking the patient is courteous and professional. Gloves must be removed in an aseptic manner and hands washed or decontaminated with hand sanitizer as an infection control precaution. STEP 18: TRANSPORT SPECIMEN TO THE LAB Prompt delivery to the lab protects specimen integrity and is typically achieved by personal delivery, transportation via a pneumatic tube system, or a courier service. Capillary Puncture Procedures Most capillary punctures are fingersticks. Fingerstick procedure is illustrated in Procedure 10-1. Heel punctures are performed on infants under 1 year of age. Heelstick procedure is illustrated in Procedure 10-2. Check out the Capillary Blood Specimen Collection video and the Introductory and Identification Processes Required Prior to Blood Specimen Collection video at http://thepoint.lww.com/McCall5e. PROCEDURE 10-1 Fingerstick Procedure PURPOSE: To obtain a blood specimen for patient diagnosis or monitoring from a finger puncture EQUIPMENT: Gloves, warming device (optional), antiseptic prep pad, safety finger puncture lancet, microcollection tubes or other appropriate collection devices, gauze pads, sharps container, permanent ink pen, bandage Step Explanation/Rationale 1–3. See Chapter 8 Venipuncture steps 1 through 3. See Chapter 8 Procedure 8-2: steps 1 through 3. 4. Sanitize hands and put on gloves. Proper hand hygiene plays a major role in infection control by protecting the phlebotomist, the patient, and others from contamination. Gloves are required at this point to protect the phlebotomist from bloodborne pathogen exposure. 5. Position the patient. The patient’s arm must be supported on a firm surface with the hand extended and the palm up. A young child may have to be held on the lap and restrained by a parent or guardian. (continued) 334 UNIT III: BLOOD COLLECTION PROCEDURES PROCEDURE 10-1 Fingerstick Procedure (Continued) Step Explanation/Rationale 6. Select the puncture/incision site. Select a site in the central, fleshy portion and slightly to the side of center of a middle or ring finger that is warm, pink or normal color, and free of scars, cuts, bruises, infection, rashes, swelling, or previous punctures. 7. Warm the site, if applicable. Warming makes blood collection easier and faster, and reduces the tendency to squeeze the site. It is not normally part of a routine fingerstick unless the hand is cold, in which case, wrap it in a comfortably warm washcloth or towel for 3 to 5 minutes or use a commercial warming device. 8. Clean and air-dry the site. CLSI recommends 70% isopropanol for cleaning capillary puncture sites. Cleaning removes or inhibits skin flora that could infiltrate the puncture and cause infection. Letting the site dry naturally permits maximum antiseptic action, prevents contamination caused by wiping, and avoids stinging on puncture and specimen hemolysis from residual alcohol. 9. Prepare the equipment. Select a fingerstick lancet according to the age of the patient and amount of blood to be collected. Verify lancet sterility by checking to see that packaging is intact before opening; open and handle aseptically to maintain sterility. Select collection devices according to the ordered tests. Place items within easy reach along with several layers of gauze or gauze-type pads. Remove or release any lancet locking mechanism and hold the lancet between the thumb and index finger or per manufacturer’s instructions. 10. Puncture the site and discard the lancet/incision device. Grasp the patient’s finger between your nondominant thumb and index finger, holding it securely in case of sudden movement. Place the lancet flat against the skin in the central, fleshy pad of the finger, slightly to the side of center to avoid bone injury, and perpendicular to the fingerprint whorls so the blood will form easily collected drops and not run down the fingerprint. Warn the patient or parent/guardian, trigger the puncture, and discard the lancet in sharps container. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 335 PROCEDURE 10-1 Fingerstick Procedure (Continued) Step Explanation/Rationale 11. Wipe away the first blood drop. Apply gentle pressure until a blood drop forms, and use a clean gauze pad to wipe it away. This prevents contamination of the specimen with excess tissue fluid and rids the site of alcohol residue that could prevent formation of well-rounded drops and also hemolyze the specimen. 12. Fill and mix the tubes/containers in order of draw Collect subsequent blood drops using devices appropriate for the ordered tests and in the CLSI order of draw to minimize effects of clotting on specimens. Hold a microhematocrit tube above or beside the site and touch one end to the blood drop. You may need to lower the opposite end of the tube slightly as it fills, but do not remove it from the drop because this creates air spaces in the specimen that compromise results. When the tube is full, plug the opposite or dry end with clay or other suitable sealant. Hold a microcollection tube below the blood drop. Touch the scoop to the blood drop and allow it to run down the inside wall of the tube. The tube may need a gentle tap occasionally to settle blood to the bottom. Seal tubes when full and mix additive tubes by gently inverting them 8 to 10 times. (continued) 336 UNIT III: BLOOD COLLECTION PROCEDURES PROCEDURE 10-1 Fingerstick Procedure (Continued) Step Explanation/Rationale 13. Place gauze and apply pressure. Apply pressure with a clean gauze pad and elevate the site until bleeding stops. 14. Label the specimen and observe special handling instructions. Specimens must be labeled with the appropriate information (see Chapter 8). Affix labels directly to microcollection containers. Place microhematocrit tubes in a nonadditive or aliquot tube and place the label on this container. Follow any special handling required. 15. Check the site and apply bandage. Examine the site to verify that bleeding has stopped; apply a bandage if the patient is an older child or adult, and advise the patient to keep it in place for at least 15 minutes. If bleeding persists beyond 5 minutes, notify the patient’s nurse or physician. 16. Dispose of used and contaminated materials. Discard equipment packaging and bandage wrappers in the trash. Follow facility protocol for discarding contaminated items, such as blood-soaked gauze. 17. Thank patient, remove gloves, and sanitize hands. Thanking the patient is courteous and professional. Remove gloves aseptically and wash or decontaminate hands with sanitizer as an infection control precaution. 18. Transport specimen to the lab. Prompt delivery to the lab is necessary to protect specimen integrity. PROCEDURE 10-2 Heelstick Procedure PURPOSE: To obtain a blood specimen for patient diagnosis or monitoring from a heel puncture EQUIPMENT: Gloves, warming device, antiseptic prep pad, safety heel puncture lancet, microcollection tubes or other appropriate collection devices, gauze pads, sharps container, permanent ink pen Step Explanation/Rationale 1–3. See Chapter 8 venipuncture steps 1 through 3. See Chapter 8 Procedure 8-2: steps 1 through 3. 4. Sanitize hands and put on gloves. Proper hand hygiene plays a major role in infection control by protecting the phlebotomist, the patient, and others from contamination. Gloves should be put on at this point. 5. Position the patient. The infant should be lying face up with the foot lower than the torso so gravity can assist blood flow. 6. Select the puncture/incision site. Select a site on the medial or lateral plantar surface of the heel that is warm, normal color, and free of cuts, bruises, infection, rashes, swelling, or previous punctures. 7. Warm the site, if applicable. Warming makes blood collection easier and faster and reduces the tendency to squeeze the site. Warm the heel by wrapping it in a comfortably warm washcloth, towel, or diaper for 3 to 5 minutes or use a commercial heel-warming device. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 337 PROCEDURE 10-2 Heelstick Procedure (Continued) Step Explanation/Rationale 8. Clean and air-dry the site. CLSI recommends 70% isopropanol for cleaning capillary puncture sites. Cleaning removes or inhibits skin flora that could infiltrate the puncture and cause infection. Letting the site dry naturally permits maximum antiseptic action, prevents contamination caused by wiping, and avoids stinging on puncture and specimen hemolysis from residual alcohol. 9. Prepare the equipment. Select a heel puncture device. Verify packaging is intact to assure sterility. Open and handle aseptically to maintain sterility. Select blood collection devices according to the ordered tests. Place items within easy reach along with several layers of sterile gauze. Release any locking mechanism, and hold the lancet between the thumb and index finger. (continued) 338 UNIT III: BLOOD COLLECTION PROCEDURES PROCEDURE 10-2 Heelstick Procedure (Continued) Step Explanation/Rationale 10. Puncture the site and discard the lancet/incision device. Grasp the foot gently, but firmly with your nondominant hand. Encircle the heel with your index finger around the arch, thumb around the bottom, and other fingers around the top of the foot. Place the lancet flat against the skin on the medial or lateral plantar surface of the heel, using sufficient pressure to keep it in place without deeply compressing the skin. Trigger the puncture, and discard the lancet in a sharps container. 11. Wipe away the first blood drop. Position the foot downward and apply gentle pressure to the site to encourage blood flow. Wipe away the first blood drop with a gauze pad to prevent contamination of the specimen with excess tissue fluid and rid the site of alcohol residue that could prevent formation of wellrounded drops and also hemolyze the specimen. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 339 PROCEDURE 10-2 Heelstick Procedure (Continued) Step Explanation/Rationale 12. Fill and mix tubes/containers in order of draw. Collect subsequent blood drops using appropriate devices for the ordered tests and fill them in the same manner described in fingerstick procedure step 12. Follow CLSI order of draw for capillary specimens to minimize effects of clotting. 13. Place gauze and apply pressure. Apply pressure with a clean gauze pad and elevate the foot until bleeding stops. 14. Label the specimen and observe special handling instructions. Specimens must be labeled with the appropriate ID information (see Chapter 8). Affix labels directly to microcollection containers. Place microhematocrit tubes in a nonadditive or aliquot tube and place the label on this container. Follow any special handling required. 15. Check the site. Examine the site to verify that bleeding has stopped. If bleeding persists beyond 5 minutes, notify the patient’s nurse or physician. Do not apply a bandage to an infant because it can become a choking hazard and can also tear the skin when removed. (continued) 340 UNIT III: BLOOD COLLECTION PROCEDURES PROCEDURE 10-2 Heelstick Procedure (Continued) Step Explanation/Rationale 16. Dispose of used and contaminated materials. Discard equipment packaging and bandage wrappers in the trash. Follow facility protocol for discarding contaminated items, such as blood-soaked gauze. 17. Thank parent or guardian, remove gloves, and sanitize hands. Thanking the parent or guardian is courteous and professional. Remove gloves aseptically and wash or decontaminate hands with sanitizer as an infection control precaution. 18. Transport specimen to the lab. Prompt delivery to the lab is necessary to protect specimen integrity. Special Capillary Puncture Procedures CAPILLARY BLOOD GASES Capillary puncture blood is less desirable for blood gas analysis, primarily because of its partial arterial composition and also because it is temporarily exposed to air during collection, which can alter test results. Consequently, capillary blood gas specimens (CBGs) are rarely collected on adults. However, because arterial punctures can be hazardous to infants and young children, blood gas analysis on these patients is sometimes performed on capillary specimens. CBG specimens are collected from the same sites as routine capillary puncture specimens. Warming the site for 5 to 10 minutes before collection is necessary to increase blood flow and arterialize the specimen. Proper collection technique is essential to minimize exposure of the specimen to air. Collection of a capillary blood gas specimen by heel puncture is illustrated in Procedure 10-3. PROCEDURE 10-3 Collection of a Capillary Blood Gas (CBG) Specimen by Heel Puncture PURPOSE: To obtain a specimen for blood gas analysis by capillary puncture EQUIPMENT: Gloves, warming device, antiseptic prep pad, safety lancet, special capillary tube with caps, metal filings (fleas) or stirrer bar, magnet, sterile gauze pads, sharps container, permanent ink pen Step Explanation/Rationale 1–6. Same as routine heelstick procedures See capillary puncture steps 1 through 6 7. Warm the site. Warming the site is required to arterialize the specimen. It also makes blood collection easier and faster and reduces the tendency to squeeze the site. Warm the heel by wrapping it in a comfortably warm washcloth, towel, or diaper for 3 to 5 minutes or use a commercial heelwarming device. 8. Clean and air-dry the site. CLSI recommends cleaning a heel puncture site with 70% isopropanol to remove or inhibit skin flora that could infiltrate the puncture and cause infection. Letting the site dry naturally permits maximum antiseptic action, prevents contamination caused by wiping, and avoids stinging on puncture and specimen hemolysis from residual alcohol. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 341 PROCEDURE 10-3 Collection of a Capillary Blood Gas (CBG) Specimen by Heel Puncture (Continued) Step Explanation/Rationale 9. Prepare the equipment. Place a metal stirrer bar or metal filings (fleas) in the capillary tube to help mix the specimen during collection. Place tube caps and magnet within easy reach along with several layers of sterile gauze. Select, open, prepare, and hold a sterile puncture device as described in Heelstick Procedure 10-2 step 9. 10. Puncture the site and discard the lancet. Grasp the heel and puncture the site as described in Heelstick Procedure 10-2 step 10. Immediately discard the puncture device. 11. Wipe away the first drop of blood. Wiping the first drop removes excess tissue fluid and alcohol residue that could affect test results. 12. Fill the capillary tube with blood. Collect the specimen quickly to minimize exposure of the blood drops to air, and carefully to prevent introduction of air spaces in the tube. The tube must be completely full with no air spaces or results will be inaccurate. 13. Immediately cap both ends of the tube. The tube must be sealed as soon as possible to prevent exposure to air and protect blood gas composition. 14. Mix the specimen with the magnet. Run the magnet back and forth the full length of the tube several times. The magnet pulls the metal stirrer (or fleas) with it, mixing the blood with the heparin and preventing clotting. 15. Label the tube. Specimens must be labeled with the appropriate ID information. 16. Place the tube in ice slurry. Place the tube horizontally in ice slurry. Cooling slows WBC metabolism and prevents changes in pH and blood gas values. 17. Check the puncture site. Examine the site to verify that bleeding has stopped. If bleeding persists beyond 5 minutes, notify the patient’s nurse or physician. Do not apply a bandage to an infant because it can become a choking hazard and can also tear the skin when removed. 18. Dispose of used and contaminated materials. Discard equipment packaging and bandage wrappers in the trash. Follow facility protocol for discarding contaminated items, such as blood-soaked gauze. 19. Thank parent or guardian, remove gloves, and sanitize hands. Thanking the parent or guardian is courteous and professional. Remove gloves aseptically and wash or decontaminate hands with sanitizer as an infection control precaution. 20. Transport specimen to the lab. Prompt delivery to the lab is necessary to protect specimen integrity. Can you find “bilirubin” among the scrambled words in WORKBOOK Knowledge Drill 10-2? NEONATAL BILIRUBIN COLLECTION Neonates (newborns) are commonly tested to detect and monitor increased bilirubin levels caused by overproduction or impaired excretion of bilirubin. Overproduction of bilirubin occurs from accelerated red blood cell hemolysis associated with hemolytic disease of the newborn (HDN). Impaired bilirubin excretion often results from temporary abnormal liver 342 UNIT III: BLOOD COLLECTION PROCEDURES Figure 10-11 A newborn infant with jaundice. (Reprinted with permission from Carol Mattson Porth, Pathophysiology Concepts of Altered Health States, 7th ed., Philadelphia: Lippincott Williams & Wilkins; 2005.) function commonly associated with premature infants. High levels of bilirubin result in jaundice (yellow skin color) (Fig. 10-11). Bilirubin can cross the blood–brain barrier in infants, accumulating to toxic levels that can cause permanent brain damage or even death. A transfusion may be needed if levels increase at a rate equal to or greater than 5.0 mg/dL per hour or when levels exceed 18.0 mg/dL. Bilirubin breaks down in the presence of light. Consequently, jaundiced infants are often placed under special ultraviolet (UV) lights to lower bilirubin levels. CAUTION: The UV light must be turned off when collecting a bilirubin specimen to prevent it from breaking down bilirubin in the specimen as it is collected. Bilirubin specimens are normally collectd by heel puncture. Proper collection procedure is crucial to the accuracy of results. Specimens must be collected quickly to minimize exposure to light and must be protected from light during transportation and handling. To reduce light exposure, specimens are typically collected in amber-colored microcollection containers (Fig. 10-12). Specimens must be collected carefully to avoid hemolysis, which could falsely decrease bilirubin Figure 10-12 An amber-colored microcollection container used to protect a bilirubin specimen from effects of ultraviolet light. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 343 results. Because determining the rate of increase in bilirubin levels depends on accurate timing, specimens should be collected as close as possible to the time requested. NEWBORN/NEONATAL SCREENING Newborn/neonatal screening (NBS) is the state mandated testing of newborns for the presence of certain genetic (inherited), metabolic (chemical changes within living cells), hormonal, and functional disorders that can cause severe mental handicaps or other serious abnormalities if not detected and treated early. Some states also screen for infectious agents, such as toxoplasma and HIV. The number and type of newborn screening tests varies by state. Requirements for disorders to be included in NBS screening panels include benefits to early diagnosis, availability of accurate tests to confirm diagnosis, and better health as a result of early detection and treatment. For a fee, some labs will perform additional newborn screening tests that are not part of state-mandated testing. The March of Dimes recommends that all newborns be screened for 29 specific disorders, including hearing loss, for which there is effective treatment (Table 10-1). So far, 48 states and the District of Columbia screen for 21 or more of the 29 disorders. There are 25 other conditions that are often identified during NBS for which there is currently limited information or no treatment. Screening for phenylketonuria (PKU), galactosemia, and hypothyroidism is required by law in all 50 states and U.S. territories. Mandatory screening for cystic fibrosis (CF) became effective in all 50 states and the District of Columbia by the end of 2009. Phenylketonuria: Phenylketonuria is a genetic disorder characterized by a defect in the enzyme that breaks down the amino acid phenylalanine, converting it into the amino acid tyrosine. Without intervention, phenylalanine, which is in almost all food, accumulates in the blood and is only slowly metabolized by an alternate pathway that results in increased phenylketones in the urine. PKU cannot be cured but normally can be treated with a diet low in phenylalanine. If left untreated or not treated early on, phenylalanine can rise to toxic levels and lead to brain damage and mental retardation. PKU testing typically requires the collection of two specimens, one shortly after an infant is born and another after the infant is 10 to 15 days old. The incidence of PKU in the United States is approximately 1 in 10,000 to 25,000 births. Hypothyroidism: Hypothyroidism is a disorder that is characterized by insufficient levels of thyroid hormones. If left untreated, the deficiency hinders growth and brain development. Some forms of neonatal hypothyroidism, although congenital (present at birth), are not inherited but temporarily acquired because the mother has the condition. Newborn screening tests detect both inherited and noninherited forms. In the United States and Canada, the newborn screening test for hypothyroidism measures total thyroxine (T4). Positive results are confirmed by measuring thyroid-stimulating hormone (TSH) levels. The disorder is treated by supplying the missing thyroid hormone orally. The incidence of hypothyroidism is 1 in 4,000 births. Galactosemia: Galactosemia (GALT) is an inherited disorder characterized by lack of the enzyme needed to convert the milk sugar galactose into glucose needed by the body for energy. Within a week of birth, an infant with galactosemia will fail to thrive due to anorexia, diarrhea, and vomiting unless galactose and lactose (lactose breaks down to galactose and glucose) are removed from the diet. Untreated, the infant may starve to death. 344 UNIT III: BLOOD COLLECTION PROCEDURES TABLE 10-1 March of Dimes Recommended Newborn Screening Tests by Category Disorder Description Untreated Consequence if Screening Tests Category Organic acid metabolism disorders Inherited disorders resulting from inactivity of an enzyme involved in the breakdown of amino acids and other body substances, such as lipids, sugars, and steroids Toxic acids build up in the body and can lead to coma and death within the first month of life. IVA (isovaleric acidemia) GA I (glutaric acidemia ) HMG (3-OH,3-CH3-glutaric aciduria) MCD (multiple carboxylase deficiency) MUT (methylmalonic acidemia from mutase deficiency) Cbl A, B (methylmalonic acidemia) 3MCC (3-methylcrotonyl-CoA carboxylase deficiency) PROP (propionic acidemia) BKT (beta-ketothiolase deficiency) Fatty acid oxidation disorders Disorders involving inherited defects in enzymes that are needed to convert fat into energy The body is unable to produce alternate fuel when it runs out of glucose as can happen with illness or skipping meals. Glucose deprivation negatively affects the brain and other organs, and can lead to coma and death. MCAD (medium-chain acyl-CoA dehydrogenase deficiency) VLCAD (very long-chain acyl-CoA dehydrogenase deficiency) LCHAD (long-chain L-3-OH-acylCoA dehydrogenase deficiency) TFP (trifunctional protein deficiency) CUD (carnitine uptake defect) Amino acid metabolism disorders A diverse group of disorders. Some involve lack of an enzyme needed to breakdown an amino acid Others involve deficiencies of enzymes that aid in the elimination of nitrogen from amino acid molecules Toxic levels of amino acids or ammonia can build up in the body, causing a variety of symptoms and even death. Severity of symptoms varies by disorder. PKU (phenylketonuria) MSUD (maple syrup urine disease) HCY (homocystinuria) CIT (citrullinemia) ASA (argininosuccinic acidemia) TYR I (tyrosinemia type I) Hemoglobinopathies Inherited disorders of the red blood cells that result in varying degrees of anemia and other health problems Anemias that vary in severity by disorder and by individual Hb SS (sickle cell anemia) Hb S/Th (hemoglobin S/beta thalassemia) Hb S/C (hemoglobin S/C disease) Others Mixed group of inherited and noninherited disorders Severity varies from mild to life threatening, depending on the disorder. CH (congenital hypothyroidism) BIOT (biotinidase deficiency) CAH (congenital adrenal hyperplasia due to 21-hydroxylase deficiency) GALT (classic galactosemia) HEAR (hearing loss) CF (cystic fibrosis) Source: March of Dimes, Professionals and Researchers, Quick References and Fact Sheets, Recommended Newborn Screening Tests: 29 Disorders. Retrieved May 5, 2010 from http://www.marchofdimes.com/professionals/14332_15455.asp. Untreated infants that survive typically fail to grow, are mentally handicapped, and have cataracts. Treatment involves removing all milk and dairy products from the infant’s diet. Several less severe forms of galactosemia that may not need treatment can also be detected by newborn screening. The incidence of galactosemia is 1 in 60,000 to 80,000 births. Cystic Fibrosis: CF is a genetic disorder caused by one or more mutations in the gene that directs a protein responsible for regulating the transport of chloride across cell membranes. CF involves multiple organs, but primarily affects the lungs and pancreas. The mutation causes the body to produce thick, sticky mucus secretions that build up in the lungs and other organs. The mucus obstructs passageways in the lungs, leading to pulmonary infections. Mucus blockage of pancreatic enzymes needed for digestion can lead to malnutrition. Early diagnosis and treatment helps avoid respiratory distress and malnutrition, and has the potential to increase life expectancy. CF occurs in 1 of CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 345 Figure 10-13 Newborn screening specimen collection equipment. every 3,700 U.S. births. Prevalence at birth varies by race/ethnicity from 1 in 2,500 to 3,500 births among non-Hispanic whites, 1 in 4,000 to 10,000 among Hispanics, and 1 in 15,000 to 20,000 births among non-Hispanic blacks. Most NBS tests are ideally performed when an infant is between 24 and 72 hours old. Because of early hospital release, some infants are tested before they are 24 hours old. Early testing for some tests (e.g., PKU) may not give accurate results, so some states require repeat testing approximately 2 weeks later. Specimens for NBS tests are collected by heel puncture and require a special state form. Newborn screening equipment is shown in Figure 10-13. On-line information on newborn screening can be found at the National Newborn Screening and Genetic Resource Center at www.genes-r-us.uthscsa.edu/. Blood Spot Collection Newborn screening tests, except hearing tests, are typically performed on a few drops of blood obtained by heel puncture. The blood drops are collected by absorption onto circles printed on a special type of filter paper that is typically part of the NBS form (Fig. 10-14). The blood-filled circles are often referred to as blood spots. As many as 30 different disorders can be detected in the blood spots on one form. CAUTION: If an infant requires a blood transfusion, newborn screening specimens should be collected before it is started, as dilution of the sample with donor blood invalidates test results. To fill the circles, heel puncture is performed, and the first blood drop is wiped away in the normal manner. The filter paper is brought close to the heel, and a large drop of free-flowing blood is applied to the center of the first circle on the printed side of the paper. The paper Figure 10-14 A newborn screening form with collection circles displayed. 346 UNIT III: BLOOD COLLECTION PROCEDURES must not be allowed to touch the surface of the heel. This can result in smearing, blotting, and stoppage of blood flow, and incomplete penetration of blood through the paper. The original position of the paper must be maintained and blood must continue flowing until it completely fills the circle on both sides of the paper. The same process is continued until all circles are filled. Unfilled or incompletely filled circles can result in inability to perform all required tests. Circles must be filled from one side of the paper only and by one large drop that spreads throughout the circle. Application of multiple drops or filling circles from both sides of the paper causes layering of blood and possible misinterpretation of results. CAUTION: Do not contaminate the filter paper circles by touching them with or without gloves or allowing any other object or substance to touch them before, during, or after specimen collection. Substances that have been identified as contaminants in newborn screening specimens include alcohol, formula, lotion, powder, and urine. After collection, the specimen must be allowed to air-dry in an elevated, horizontal position away from heat or sunlight. Specimens should not be hung to dry or stacked together before, during, or after the drying process. Hanging may cause the blood to migrate and concentrate toward the low end of the filter paper and lead to erroneous test results on the sample. Stacking can result in cross-contamination between specimens, which also causes erroneous results. When dry, the requisition containing the sample is normally placed in a special envelope and sent to a state public health laboratory or other approved laboratory for testing. Results are sent to the infant’s physician or other healthcare provider. The procedure for collecting blood spots for newborn screening is shown in Procedure 10-4. PROCEDURE 10-4 Newborn Screening Blood Spot Collection PURPOSE: To obtain a newborn screening blood sample by heel puncture EQUIPMENT: Gloves, warming device, antiseptic prep pad, safety lancet, newborn screening filter paper, sterile gauze pads, sharps container, permanent ink pen Step Explanation/Rationale 1–4. Follow Chapter 8 venipuncture steps 1 through 4. See Chapter 8 Procedure 8-2: steps 1 through 4. 5. Position the patient. See Heelstick Procedure 10-2: step 5. 6. Select the puncture/incision site. See Heelstick Procedure 10-2: step 6. 7. Warm the site, if applicable. See Heelstick Procedure 10-2: step 7. 8. Clean and air-dry the site. See Heelstick Procedure 10-2: step 8. 9. Prepare the equipment. See Heelstick Procedure 10-2: step 9. 10. Puncture site and discard lancet. See Heelstick Procedure 10-2: step 10. 11. Wipe away the first blood drop. See Heelstick Procedure 10-2: step 11. 12. Bring the filter paper close to the heel. Ensures that drops fill the circles properly. The paper must not actually touch the heel; if it does, smearing, incomplete penetration of the paper, blotting, and stoppage of blood flow can result. 13. Generate a large, free-flowing drop of blood. It takes a large, free-flowing blood drop to fill a circle. Small drops can result in incomplete filling and the tendency to layer successive drops in a circle to fill it. 14. Touch the blood drop to the center of the filter paper circle. The drop must touch the center of the circle for blood to uniformly spread out to the perimeter. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 347 PROCEDURE 10-4 Newborn Screening Blood Spot Collection (Continued) Step Explanation/Rationale 15. Fill the circle with blood. Blood drop position is maintained until blood soaks through the circle, completely filling both sides of the paper. Caution: Do not fill spots from the reverse side to finish filling the circles because this causes layering and erroneous results. 16. Fill remaining blood spot circles. Fill all circles the same way. Unfilled or incompletely filled circles can result in inability to perform all required tests. 17. Place gauze and apply pressure. Apply pressure with a clean gauze pad and elevate the site until bleeding stops. 18. Label specimen. Specimens must be appropriately identified. 19. Check the site. Check the site to verify that bleeding has stopped, but do not apply a bandage because it can become a choking hazard and can also tear the skin when removed. 20. Dispose of used materials Equipment packaging and bandage wrappers can be discarded in the trash. Follow facility protocol for discarding contaminated items, such as blood-soaked gauze. 21. Allow the specimen to air-dry. The specimen must be allowed to air-dry in an elevated horizontal position away from heat or sunlight. It should not be hung to dry or stacked with other specimens before, during, or after the drying process. Hanging causes blood to migrate to the low end of the filter paper and leads to erroneous test results. 22. Dispatch specimen to testing facility. When dry, the sample-containing requisition is normally placed in a special envelope and sent to the appropriate laboratory for testing. 348 UNIT III: BLOOD COLLECTION PROCEDURES ROUTINE BLOOD FILM/SMEAR PREPARATION A blood film or smear (a drop of blood spread thin on a microscope slide) is required to perform a manual differential (Diff), a test in which the number, type, and characteristics of blood cells are determined by examining a stained blood smear under a microscope. A manual differential may be performed as part of a complete blood count or to confirm abnormal results of a machine-generated differential or platelet count. Two blood smears are normally prepared and submitted for testing. Although a common practice in the past, today blood smears are rarely made at the bedside. They are typically made in the hematology department from blood collected in an EDTA tube, either by hand or using an automated machine that makes a uniform smear from a single drop of blood. KEY POINT Blood smears prepared from EDTA specimens should be made within 1 hour of collection to eliminate cell distortion caused by the anticoagulant. A few special tests require evaluation of a blood smear made from a fresh drop of blood from a fingertip. An example is a leukocyte alkaline phosphatase (LAP) stain or score, which usually requires four fresh peripheral blood (blood from an extremity) smears. Skin puncture collection of peripheral smears is typically preferred. In addition, some hematologists prefer blood smears made from blood that has not been in contact with EDTA. When collected with other skin puncture specimens, blood smears should be collected first to avoid effects of platelet clumping. Blood smear preparation from a capillary puncture is illustrated in Procedure 10-5. PROCEDURE 10-5 Preparing a Blood Smear from a Capillary Puncture PURPOSE: To prepare two routine blood films (smears) for hematology or other studies using blood obtained by capillary puncture EQUIPMENT: Gloves, alcohol prep pad, lancet/incision device, two plain or frosted glass slides free of cracks or chipped edges, gauze pads, bandage, and a pencil Step Explanation/Rationale 1. Perform capillary puncture. Blood to make the slide can be obtained by normal finger or heel puncture, following applicable capillary puncture steps 1 through 9 until this point. 2. Wipe away first blood drop. Wiping the first drop removes excess tissue fluid and alcohol residue that could distort cell morphology. 3. Touch a slide the next blood drop The drop should be 1 to 2 mm in diameter and centered on the slide adjacent to the frosted end or 1/2 to 1 inch from one end of a plain slide. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES 349 PROCEDURE 10-5 Preparing a Blood Smear from a Capillary Puncture (Continued) Step Explanation/Rationale 4. Hold the blood drop slide between the thumb and forefinger of the nondominant hand. With the other hand, rest the second slide in front of the drop at an angle of approximately 30 degrees. The second slide is called the pusher or spreader slide and is held at one end, between the thumb and index finger in either a vertical or horizontal position. If blood is of normal thickness, a 30-degree angle will create a smear that covers approximately three fourths of the remaining area of the slide. 5. Pull the spreader slide back to the edge of the blood drop. Stop it as soon as it touches the drop, and allow the blood to spread along its width. The blood must spread the width of the pusher slide or a bullet-shaped film will result. (continued) 350 UNIT III: BLOOD COLLECTION PROCEDURES PROCEDURE 10-5 Preparing a Blood Smear from a Capillary Puncture (Continued) Step Explanation/Rationale 6. Push the spreader slide away from the drop in one smooth motion, carrying it the entire length and off the end of the blood drop slide. Let the weight of the spreader slide carry the blood and create the film or smear. Do not push down on the spreader slide because this creates lines and ridges and an unacceptable blood film. 7. Place the drop of blood for the second smear on the spreader slide. Use the slide with the first smear as the spreader slide for the second smear and make it in the same manner as the first one. This way, two smears can be made using only two slides. 8. Place gauze over the wound and ask the patient to apply pressure. A conscious, mentally alert patient can apply pressure; otherwise, the phlebotomist must apply pressure. 9. Label frosted blood slides by writing the patient information in pencil on the frosted area. If using a preprinted label, attach it over the writing or in the empty space at the blood drop end if it is a plain slide. Do not use ink because it may dissolve during the staining process. 10. Allow the blood films to air-dry and place them in a secondary container for transport. Never blow on a slide to dry it because red blood cell distortion may result. Be aware that unfixed slides are capable of transmitting disease and handle accordingly. 11. Thank patient, remove gloves, and sanitize hands. Thanking the patients, parents, and guardians is courteous and professional. Remove gloves aseptically and wash hands or use a hand sanitizer as an infection control precaution. 12. Transport specimen to the lab. Prompt delivery to the lab is necessary to protect specimen integrity. CHAPTER 10: CAPILLARY PUNCTURE EQUIPMENT AND PROCEDURES A B 351 C Figure 10-15 A. DIFF-SAFE blood drop delivery device. B. Applying a blood drop to a slide using a DIFF-SAFE device. C. Blood drop on slide (Courtesy Alpha Scientific, Malvern, PA). To prepare a smear manually from an EDTA specimen, the tube of blood must first be mixed for a minimum of 2 minutes to ensure a uniform specimen. A plain capillary tube or pipet is then used to dispense a drop of blood from the specimen tube onto the slide. A device called DIFF-SAFE (Fig. 10-15A–C) (Alpha Scientific, Malvern, PA) allows a slide to be made from an EDTA tube without removing the tube stopper. The device is inserted through the rubber stopper of the specimen tube and then pressed against the slide to deliver a uniform drop of blood. CAUTION: Blood smears are considered biohazardous or infectious until they are stained or fixed. Making a good blood smear is a skill that takes practice to perfect. Improperly made blood smears may not contain a normal, even distribution of blood cells and can produce erroneous results. An acceptable smear covers about one half to three fourths of the surface of the slide and has no holes, lines, or jagged edges. It should show a smooth transition from thick to thin when held up to the light. The thinnest area of a properly made smear, often referred to as the feather, is one cell thick and is the most important area because that is where a differential is performed. Smears that are uneven, too long (i.e., cover the entire length of the slide), too short, too thick, or too thin are not acceptable. The length and thickness of the smear can usually be controlled by adjusting the size of the drop or the angle of the spreader slide. Dirt, fingerprints, or powder on the slide, or fat globules and lipids in the specimen can result in holes in the smear. A chipped pusher slide, a blood drop that has started to dry out, or uneven pressure as the smear is made can cause the smear to have ragged edges. Table 10-2 lists common problems associated with routine blood smear preparation. THICK BLOOD SMEAR PREPARATION Thick blood smears are most often requested to detect the presence of malaria, a disorder caused by four species of parasitic sporozoan (types of protozoa) organisms called plasmodia. These organisms are transmitted to humans by the bite of infected female anopheles mosquitoes. Symptoms of malaria include serial bouts of fever and chills at regular intervals, related to the multiplication of certain forms of the organism within the red blood cells and the consequent rupture of those cells. The progressive destruction of red blood cells in certain types of malaria causes severe anemia. Malaria is diagnosed by the presence of the organism in a peripheral blood smear. Diagnosis often requires the evaluation of both regular and thick blood smears. Presence of the 352 UNIT III: BLOOD COLLECTION PROCEDURES TABLE 10-2 Common Problems Associated with Routine Blood Smear Preparation Problem Probable Cause Absence of feather Spreader slide lifted before the smear was completed Holes in the smear Dirty slide Fat globules in the blood Blood contaminated with glove powder Ridges or uneven thickness Too much pressure applied to spreader slide Smear is too thick Blood drop too large Spreader slide angle too steep Patient has high red blood cell count Smear is too short Blood drop too small Spreader slide angle too steep Spreader slide pushed too quickly Patient has high red blood cell count Smear is too long Blood drop too large Spreader slide angle too shallow Spreader slide pushed too slowly Patient has a low hemoglobin Smear is too thin Blood drop too small Spreader slide angle too shallow Patient has a low hemoglobin Streaks or tails in feathered edge Blood drop started to dry out Edge of spreader slide dirty or chipped Spreader slide pushed through blood drop Uneven pressure applied to spreader slide organism is observed most frequently in a thick smear; however, identification of the species requires evaluation of a regular blood smear. Malaria smears may be ordered STAT or at timed intervals and are most commonly collected just before the onset of fever and chills. To prepare a thick smear, a very large drop of blood is placed in the center of a glass slide and spread with the corner of another slide or cover slip until it is the size of a dime. The smear is allowed to dry for a minimum of 2 hours before staining with fresh diluted Giemsa stain, a water-based stain that lyses the red blood cells and makes the organism easier to see. STUDY AND REVIEW QUESTIONS See the EXAM REVIEW for more study questions. 1. Which of the following tests requires an arterialized specimen? a. Bilirubin c. Electrolytes b. CBGs d. Glucose 2. Capillary puncture supplies include all of the following except: a. Gauze pad c. Microcollection device b. Lancet d. Povidone–iodine pad 3. Capillary puncture blood contains: a. Arterial blood c. Venous blood b. Interstitial fluids d. All of the above 4. The concentration of this substance is higher in capillary blood than in venous blood: a. Blood urea nitrogen b. Carotene c. Glucose d. Total protein 5. Capillary puncture is typically performed on adults when: a. No accessible veins can be located b. Patients have thrombotic tendencies c. Veins are saved for chemotherapy d. All of the above