Pain expression in neonates: facial action and cry

Area of Science:

• Neonatal pain research
• Infant behavior and development
• Pain perception

Background:

• Pain expression in neonates is crucial for understanding infant well-being.
• Gate-control theory suggests pain perception is modulated by the infant's functional state.
• Previous research on infant cry characteristics may not fully apply to healthy infants across different states.

Purpose of the Study:

• To systematically describe neonatal pain expression using facial and cry measures.
• To compare pain responses across different sleep/waking states and sexes.
• To investigate the influence of infant state on pain behavior, aligning with gate-control theory.

Main Methods:

• Systematic observation of neonates undergoing heel-lance for blood sampling.
• Measurement of facial expressions and cry characteristics (e.g., fundamental frequency).
• Comparison of pain responses across awake-alert, quiet sleep, and active sleep states, and by sex.

Main Results:

• Infants in the awake-alert state exhibited the most facial activity.
• Infants in quiet sleep showed the least facial reaction and the longest latency to cry.
• Fundamental frequency of cry did not vary with sleep/waking state.
• Boys displayed quicker responses (cry and facial action) to heel-lance compared to girls.

Conclusions:

• Neonatal pain expression is significantly influenced by the infant's behavioral state and sex.
• The context of a pain event, including the infant's state, affects behavioral expression.
• Findings highlight the importance of state-dependent pain assessment in neonates.
• Sex differences in pain response timing were observed in healthy neonates.