Special populations: the patients who change your technique.

Infants, frail older adults, dialysis and mastectomy patients: the draws where technique changes and the exam concentrates its safety questions. A few firm reflexes carry this domain.

Why this matters

Most draws are routine. The ones that are not, infants, frail older adults, dialysis and mastectomy patients, are where harm happens and where the exam concentrates its safety questions. These are almost always single-best-answer items, so a few firm reflexes earn reliable points.

Key takeaways

• Infants: heel, usually. For infants under about one year the capillary heel stick is the common collection. For a term newborn, venipuncture is often less painful and is needed when the order requires more blood than a heel stick yields. Puncture only the medial or lateral plantar surface of the heel, never the center, back, or arch: the calcaneus sits closest to the skin at the central and posterior heel, so a stick there risks bone injury and osteomyelitis, while the medial and lateral surfaces keep the lancet away from bone.
• Mind the depth, warm the site. Heel puncture depth is no more than 2.0 mm in a full-term infant, and shallower in a premature or low-birth-weight infant, whose calcaneus can lie as little as 2.4 mm below the skin. Warm the heel first with a controlled commercial warmer, around 40 to 42 C, never an improvised heat source, which has burned infants; warming raises blood flow and cuts repeat sticks.
• Capillary order flips. Dermal blood begins clotting at once, so the capillary order of draw is blood gas first, then the EDTA (lavender) hematology tube, then other additive tubes, then serum last. That protects the CBC from platelet clumping, the reverse priority of a venous draw.
• Geriatric: anchor firmly, ease off the tourniquet. Older skin is loose and veins roll and tear easily. Anchor the vein well, choose a smaller gauge or a butterfly set, and use lighter tourniquet pressure, keeping the tourniquet on under a minute. Many older patients take anticoagulants, so hold pressure longer afterward. Do not probe.
• The arm you must not use. Never draw from an arm with a dialysis AV fistula or graft. For a mastectomy, use the other arm; if only the mastectomy side is available, current CLSI calls for documented physician approval first, and that holds no matter how long ago the surgery was and for bilateral mastectomies. With an IV running, draw from the opposite arm; if that is impossible, stop the infusion for at least two minutes, draw below the site, and pull a roughly 5 mL discard tube before the test tubes.
• Sites to skip. Edematous, burned, heavily scarred, or hematoma-covered skin gives an unreliable sample and risks the patient. Find another site rather than force the one in front of you.

Try the question your examiner is most likely to ask

You are asked to draw a patient who had a left-side mastectomy and has a dialysis fistula in the right forearm. Both arms have a reason to avoid a routine antecubital draw. What is the correct next step?

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Standards reference: CLSI GP41 (venous collection, including IV, mastectomy, and fistula precautions) and CLSI GP42 (capillary collection, heel-stick site and depth, capillary order of draw), cross-referenced against the ASCP BOC PBT content guideline. PhlebotomySkills.com is exam-preparation content. Not a degree, not for-credit coursework, and not affiliated with any certifying body. For a patient with no acceptable arm, collection requires a physician's order and is performed per facility protocol.