Heelstick Collection: Neonatal and Infant Skin Puncture

Heelstick Collection: Neonatal and Infant Skin Puncture

Capillary blood collection from a newborn's heel is one of the most common and most critical procedures a phlebotomy technician performs. Errors in site selection or technique can cause lasting injury to an infant. Understanding the anatomy, following the correct sequence, and using the right equipment are non-negotiable.

Why the Heel?

Newborns and young infants do not have veins large enough for routine venipuncture. The plantar surface of the heel provides an accessible capillary bed close to the skin. Blood collected here is used for newborn metabolic screening, bilirubin measurement, blood glucose, and other point-of-care tests.

Safe Anatomical Zones

The only acceptable puncture sites are the medial plantar surface and the lateral plantar surface of the heel. On a printed diagram, these zones fall roughly on the inner and outer lower thirds of the foot's sole, away from the arch and toes.

Three areas must never be punctured:

• The posterior curved surface of the heel — the rounded back of the heel where skin is thin and the calcaneus (heel bone) lies very close beneath it.
• The medial curved surface — similarly close to bone and to the medial plantar nerve and artery.
• The central arch area — contains nerves, tendons, and ligaments not suited for puncture.

The calcaneus is the largest tarsal bone. In a newborn it is largely cartilage, not yet fully ossified, but it still poses a serious risk. An unintended puncture into bone can introduce infection (osteomyelitis) or cause permanent structural damage. Because the distance from skin surface to bone is only a few millimeters in a newborn, depth control matters absolutely.

Warming the Heel

Warming the site before puncture increases local blood flow (arterialization) and produces a better specimen with less squeezing needed. Use a commercial heel warmer designed for neonatal use — not a towel soaked in hot water, which can cause burns. Follow the manufacturer's instructions for activation and application time, typically around 3 to 5 minutes. The device should feel warm, not hot, to your own skin before applying it to the infant.

Never use a microwave or any heat source not validated for this purpose. Burns in neonates can occur at temperatures that seem mild to an adult.

Device Selection

Use only neonatal-specific safety lancets. These devices are engineered to a controlled puncture depth appropriate for neonatal heel tissue — generally shallower than devices used for adult finger sticks. Adult lancets, even retractable ones, penetrate too deeply and risk bone contact. Always read the device label to confirm it is indicated for neonatal or infant heel use. Single-use, retractable, and blade-style neonatal devices are all acceptable; whichever you use must be neonatal-labeled.

The Heelstick Sequence

1. Verify patient identity using the two-identifier protocol (typically the armband and a parent/guardian confirmation in the NICU or nursery).

2. Gather and label all collection materials before touching the patient.

3. Don gloves. Gloves are required for all skin puncture collections.

4. Position the foot. Hold the infant's foot gently but firmly, ankle supported, heel accessible. The foot may be slightly lower than the body to encourage blood flow.

5. Warm the site with a commercial heel warmer for the recommended time.

6. Clean the site with an alcohol prep pad and allow it to dry completely. Residual alcohol dilutes the sample and can cause hemolysis.

7. Identify the safe zone visually. Puncture the medial or lateral plantar surface only.

8. Apply the lancet perpendicular to the skin and activate it in one smooth motion. Do not press so hard that the device bottoms out before firing.

9. Wipe away the first drop of blood with a clean, dry gauze pad. The first drop contains excess tissue fluid.

10. Collect the specimen. Apply gentle, intermittent pressure — not continuous milking or squeezing. Milking forces tissue fluid into the sample, diluting analytes and giving false low results.

11. Fill collection vessels. For a newborn screening filter paper card (Guthrie card), touch the single large drop to the center of each printed circle and allow blood to soak through to fill the circle completely from one continuous drop. Do not layer drop on top of drop; layering creates an uneven, clotted specimen that fails the laboratory's quality criteria.

12. Apply pressure with gauze until bleeding stops. Do not apply bandages to neonates — they are an aspiration and skin-injury risk.

13. Dispose of the lancet immediately into the sharps container.

14. Label and process specimens per your facility's policy.

Filter Paper Card (Guthrie Card) Specifics

Each circle on a newborn screening card must be filled with a single application of blood large enough to saturate the paper through to the back. Hold the card so the printed side faces the heel, touch it to the blood drop — do not smear or press repeatedly. Verify saturation by checking the reverse side. Incomplete circles or layered spots are rejected by the state screening laboratory, requiring a recollect and delaying critical diagnoses such as PKU and congenital hypothyroidism.

Allow the card to air-dry horizontally for the time specified on the card package (commonly around 3 hours) before placing it in the shipping envelope. Never stack wet cards or expose them to direct sunlight or heat.

Safety Summary

• Correct zone only — medial or lateral plantar surface.
• Neonatal-labeled device only.
• Commercial heel warmer only — no improvised heat.
• No milking; no layering on filter paper.
• No bandages on neonates.
• First drop discarded.
• Sharps disposed of immediately.

Patient safety in neonatal collection depends on discipline: every step in the right order, every time.