Question

C. Diagram the correct location to perform a dermal puncture on an infant’s heel and an adult’s third finger.

D. Describe the composition of blood samples collected via dermal puncture.  

Answer 1

C. Dermal puncture in infants

Infants who are not walking, we can use lateral or medial portion of plantar surface of heel.

Dermal puncture in adults

In hand, best locations are 3rd and 4th fingers of non-dominant hand. Avoid tip or center of the finger.

D. Blood specimen can be collected from veins, arteries and capillaries.

Composition of collected blood varies depending on the source.

Capillary blood taken via dermal puncture contain venous blood, arterial blood along with tissue fluid. Arterial blood is more because it enters capillaries under pressure.

Glucose in capillary blood is normally greater than that in venous or arterial blood.

Potassium, Calcium and total proteins are normally lower.

Squeezing the site may falsely elevate the potassium levels .