Body movements: an important additional factor in discriminating pain from stress in preterm infants.

Objectives: To describe developmentally appropriate, specific body movements and other biobehavioral responses of preterm infants to a group of routine care giving tasks (Clustered Care), and to compare responses to acute pain with those of Clustered Care.

Methods: In a randomized design, 54 preterm infants were assessed at 32 weeks gestational age during 3 phases of blood collection (Baseline, Lance/squeeze, Recovery) and of diaper changing, measuring abdominal girth and axillary temperature, and mouth care (Baseline, Clustered Care, Recovery) in a neonatal intensive care unit. The Newborn Individualized Developmental Care and Assessment Program and 1 facial action from the Neonatal Facial Coding System, Brow Bulge, were coded from separate continuous bedside video recordings. Heart rate and oxygen saturation were also acquired continuously.

Results: Brow Bulge, heart rate, and a subset of 9 Newborn Individualized Developmental Care and Assessment Program movements increased and oxygen saturation decreased significantly to Lance/squeeze compared to Baseline. Similar facial and physiological changes occurred during Clustered Care, but with less intensity. However, infants showed greater frequencies and variety of Newborn Individualized Developmental Care and Assessment Program stress cues during Clustered Care than during Lance/squeeze. Stress cues persisted after Clustered Care, whereas the infants returned to Baseline following Lance/squeeze.

Discussion: Changes in facial activity and heart rate remain the most sensitive markers of pain in preterm infants. Tactile procedures, such as diaper changing, produce lower intensity facial and physiological responses than pain procedures, but greater body reactions. Also, the effects from tactile procedures appear to last longer. Adding observations of a small number of specific body movements to the assessment of pain and stress provides complementary information particularly for those infants who may show dampened facial reactivity as a result of repeated pain exposure.