A new method to quantitatively describe pain behavior in infants.

Photogrammetric techniques were used to record the responses of 10 newborn infants to heelstick procedures at 4 hours of age. The responses consisted of an immediate withdrawal of both the affected and unaffected leg, followed by facial grimacing and crying. The median latency of withdrawal in response to the first heelstick was 0.3 seconds for the unaffected and 0.4 seconds for the affected leg, respectively. The median latency following a second heelstick was 0.2 seconds for both legs. The median latency of cry was 1.8 seconds following the first heelstick and 1.6 seconds following the second heelstick. Other quantitative parameters of the response, velocity of first affected leg movements, number of leg movements, and number of movements directed toward the stimulus, were also measured. This pilot study demonstrated a method by which quantitative data regarding pain responses in infants can be obtained and evaluated.