Capillary Puncture PDF

L2 1 Dr. Hajaya After studying this lecture, the student will: ▪ Explain why a capillary puncture is performed. ▪ Identify suitable sites for capillary punctures. ▪ Discuss capillary puncture in infants, children, and adults. ▪ Choose and prepare a site for capillary puncture. ▪ Perform a cap...

L2 1 Dr. Hajaya After studying this lecture, the student will: ▪ Explain why a capillary puncture is performed. ▪ Identify suitable sites for capillary punctures. ▪ Discuss capillary puncture in infants, children, and adults. ▪ Choose and prepare a site for capillary puncture. ▪ Perform a capillary puncture. ▪ Collect a blood specimen from a capillary puncture. ▪ Discuss how collection procedure affects capillary specimen quality. ▪ List the safety precautions to be observed when performing a capillary puncture. ▪ Define the glossary terms. 2 capillary / a minute blood vessel that connects the smallest arteries to the smallest veins and serves as an oxygen exchange vessel. capillary action / the action by which a fluid enters a tube because of the attraction between the fluid and the tube. capillary tube / a slender glass or plastic tube used for laboratory procedures. heparin / an anticoagulant used therapeutically to prevent thrombosis; also used as an anticoagulant in certain laboratory procedures. lancet / a sterile, sharp-pointed blade used to perform a capillary puncture. lateral / toward the side. 3 Capillary puncture, also called dermal puncture, is a safe, rapid, and efficient means of collecting a blood specimen. To perform capillary puncture, a small sterile lancet or blade is used to puncture the skin and capillaries to create a blood flow. Capillary punctures are performed when only a small amount of blood is required, when obtaining blood from infants, or when the patient has a condition that makes venipuncture difficult. 4 In the clinical laboratory, capillary blood has been used only in special situations, because of the small sample volume and potential for rapid clotting of the sample. However, the increased use of small, portable, easy-to-use instruments that require only a drop or two of blood, has made capillary blood the specimen of choice for these analyzers. The rapid increase in the use of these instruments in bedside testing, physician office laboratories (POLs), and other point-of-care (POC) testing sites has increased the need to train a variety of medical personnel in correct capillary puncture techniques. 5 Factors that must be considered in performing a capillary puncture are the age of the patient, type of lancet required, and type of container used to collect the blood. 6 The usual site for capillary puncture in adults and children is the fingertip (Figure 1-71). In adults, the ring finger is often selected because it usually is less calloused. For newborns and infants, capillary blood can be obtained from the lateral or side portion of the heel pad (Figure 1-72). Once an infant begins to walk (about the age of 1 year) blood should be collected from a fingerstick. 7 8 9 Equipment required for capillary puncture includes lancets and a variety of collection containers. 10 Several designs of disposable, sterile safety lancets are available for capillary puncture. These lancets make punctures of uniform depth at the touch of a button and are available in several blade lengths for use in different situations (Figure 1-73). Special pediatric lancets that produce a shallow puncture should be used with infants. 11 12 Capillary blood can be collected in capillary tubes or collection vials. Capillary blood can also be applied directly to a test strip, cuvette, or cartridge for use in POC instruments. Capillary tubes are slender tubes used primarily for microhematocrit measurements. Several types of capillary tubes are available: plain, heparinized, precalibrated, flexible, and self sealing. Tubes coated with the anticoagulant heparin have a red ring on one end. These are used to prevent clotting of the blood during the collection of capillary blood samples. Precalibrated tubes are usually heparinized and are intended to be used only in the special microhematocrit centrifuges designed for them. Non-heparinized (blue ring) capillary tubes are used with venous blood that has been previously collected in an anticoagulant. 13 Capillary blood required for tests other than microhematocrit, such as chemistry tests, can be collected in special vials with a capillary or other extension for directing the blood into the vial (Figure 1-75). These vials are available plain or with anticoagulant. Using these vials, a small quantity of whole blood, plasma, or serum can be obtained without performing venipuncture, which is particularly useful with pediatric patients. 14 15 Several hematology procedures such as blood cell counts, hemoglobin, microhematocrit, and the blood smear can be performed using capillary blood. Small handheld analyzers in POLs and a variety of POC testing sites also use capillary blood for coagulation, immunology, glucose, and other chemistry tests. 16 Although the capillary blood collection procedure appears to be simple, the technician must consider several factors. Careful technique must be used to collect a quality specimen. 17 18 19 All materials should be assembled within easy reach of the phlebotomist (Figure 1-76). The capillary puncture procedure should be explained to the patient. The patient’s fingertips should be examined for a suitable site that is not calloused and has good blood circulation. Patients whose work involves physical labor can have very calloused fingertips and the technician must take extra care to find a suitable site. Warm skin indicates adequate circulation; cool skin indicates decreased circulation. A patient’s hands can be gently massaged briefly to enhance circulation. Recent puncture sites should be avoided, especially in pediatric patients. 20 21 An alcohol swab should be used to cleanse the puncture site. The site must then be allowed to air-dry or can be wiped dry with sterile gauze. A puncture should not be made on moist skin because the blood will not form a good drop. 22 The patient’s hand and finger should be held so the puncture site is readily accessible. Using a safety lancet, the puncture is made at the tip of the fleshy pad and slightly to the side (Figure 1-77A). A lancet with a longer blade can be used for fingertips that are calloused or have thickened skin. The lancet should be discarded into a nearby sharps container (Figure 1-78). 23 24 25 The first drop of blood should be wiped away with dry, sterile gauze. This first drop contains tissue fluid, which dilutes the blood drop and can also activate clotting. The second and following drops of blood are used for the test sample. A well- rounded drop of blood should be allowed to form before collection begins (Figure 1-77B). The hand can be gently massaged to increase blood flow, but excessive pressure near the puncture site should be avoided. (Squeezing the fingertip can force tissue fluid into the blood sample.) 26 Capillary blood should be collected as quickly as possible to prevent clotting. The capillary tube should be held in an almost horizontal position, or tilted slightly downward; the blood collecting vial should be held vertically so blood will flow down into the tube (Figure 1-77C, D). When the tip of the capillary tube is touched to the blood drop, blood will enter the tube by capillary action because of the attraction between the liquid and the tube. Capillary tubes should be filled three-quarters full. Test strips or cartridges are filled following the manufacturer’s directions. 27 After the blood has been collected, sterile gauze or a cotton ball should be placed on the puncture site and pressure applied until bleeding stops. A small adhesive bandage can be applied if necessary. 28 29