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Introduction ⬇

Capillary blood is preferred for a peripheral blood smear and can also be used for other hematology studies. Adult capillary blood samples require a skin puncture, usually of the fingertip or earlobe. For children older than 1 year, the tip of the finger is often used. For children younger than 1 year, the best sample is obtained from the great toe or side of the heel.

Procedure ⬆ ⬇

Capillary Blood

  1. Observe standard precautions (see Appendix A). Check for latex allergy. If allergy is present, do not use latex-containing products.

  2. Obtain capillary blood from fingertips or earlobes (adults) or from the great toe or heel (newborns and infants younger than 1 year). Avoid using the lateral aspect of the heel where the plantar artery is located.

  3. Disinfect puncture site, let it dry, and puncture skin with sterile disposable lancet, perpendicular to the lines of the patient’s fingers, no deeper than 2 mm. If chlorhexidine is used, allow to dry thoroughly.

  4. Wipe away the initial drop of blood. Collect subsequent drops in a microtube or prepare a smear directly from a drop of blood.

  5. After collection, apply a small amount of pressure briefly to the puncture site to prevent painful extravasation of blood into the subcutaneous tissues.

Procedural Alert

  1. Do not squeeze the site to obtain blood because this alters blood composition and invalidates test values.

  2. Warming the extremity or placing it in a dependent position may facilitate specimen collection.

Dried Blood Spot

  1. In this method, a lancet is used, and the resulting droplets of blood are collected by blotting them with filter paper directly.

  2. Check the stability of equipment and integrity of supplies when doing a finger stick. If provided, check the humidity indicator patch on the filter paper card. If the humidity circle is pink, do not use the filter paper card. The humidity indicator must be blue to ensure specimen integrity.

  3. After wiping the first drop of blood on the gauze pad, fill and saturate each of the circles in numerical order by blotting the blood droplet with the filter paper. Do not touch the patient’s skin to the filter paper; only the blood droplet should come in contact with the filter paper.

  4. If an adult has a cold hand, run warm water over it for approximately 3 minutes. The best flow occurs when the arm is held downward, with the hand below heart level, making effective use of gravity. If there is a problem with proper blood flow, milk the finger with gentle pressure to stimulate blood flow or attempt a second finger stick; do not attempt more than two times.

  5. When the blood circles penetrate through to the other side of the filter paper, the circles are fully saturated.

Interventions ⬆

Pretest Patient Care

  1. Instruct the patient about purpose and procedure of test.

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Apply small dressing or adhesive bandage to site.

  2. Evaluate puncture site for bleeding or oozing.

  3. Apply compression or pressure to the site if it continues to bleed.

  4. Evaluate patient’s medication history for anticoagulation, nonsteroidal anti-inflammatory drugs (NSAIDs), or acetylsalicylic acid (ASA)-type drug ingestion.

  5. Review test results; report and record findings. Modify the nursing care plan as needed.

  6. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.