Capillary blood sampling: should the heel be warmed?

The hypothesis that capillary blood sampling is made easier by warming the heel was examined in a randomised, controlled trial of healthy newborn infants. Sampling was performed using an automated lancet with or without prior warming. The time taken to collect a standard volume of blood, the number of repeat procedures needed, and the infants' behavioural responses were measured. Eighty one procedures were studied in 57 infants. Warming produced a median rise in heel skin temperature of 4.7 degrees C. However, there were no significant differences between the warmed and unwarmed groups in any of the outcome measures. Heel skin temperature is not an important factor in capillary blood sampling. Attention should be directed towards improving sampling devices and technique.