Heel Warming in Very-Low-Birth-Weight Newborns for Capillary Blood Sampling

To determine if performing heel stick procedures for capillary blood sampling without prior heel warming is noninferior to the standard practice of warming the heel in very-low-birth-weight newborns.

Noninferiority randomized control trial.

The study took place in two Level 3 NICUs in The Netherlands.

Newborns born at less than 32 weeks gestation in their second or third week of life without an arterial line in situ or known coagulopathy (N = 100).

We randomized participants to undergo a heel stick procedure in one of two groups: without heel warming (n = 50) and heel warming with a washcloth warmed with 37 °C tap water (n = 25) or with a microwaved hot pack (n = 25). The primary outcome was length of time for obtaining the required blood sample. The secondary outcomes were number of attempts, reliability of the blood sample, newborn comfort, and adverse events.

We observed no differences in background characteristics between groups and found no statistically significant or clinically relevant differences in primary or secondary outcomes.

Among participants, not warming the heel before a heel stick was noninferior to warming the heel. Therefore, preheating the heel as a standard of care may be an unnecessary nursing intervention.