309 - Evaluating Pain Responses in Infants: Physiologic and Behavioral Perspectives

Publication Number: 4303.309

Na Li Yu, Chung-Ang University Gwangmyeong Hospital, Seoul, Seoul-t'ukpyolsi, Republic of Korea; Na Mi Lee, Chung Ang University Gwangmyeong Hospital, Gwangmyeong-si, Kyonggi-do, Republic of Korea

Background: Preterm infants are vulnerable to pain due to immature nervous systems. In the NICU stay, they undergo frequent procedures that may disrupt brain maturation and increase neurodevelopmental risks. Accurate pain assessment remains challenging, and the role of baseline characteristics is unclear.

Objective: To compare physiological and behavioral pain responses across comfort, pre-prandial (PP), and procedural states (arterial puncture [A], venipuncture [V], heel lance [H]) in neonates, and to identify factors associated with response direction and magnitude.

Design/Methods: We retrospectively analyzed 86 infants (GA ≥28 weeks, BW ≥1,000 g) admitted to our NICU from Sep 2022 to Nov 2023. Pain parameters included heart rate (HR), mean blood pressure (MBP), respiratory rate (RR), oxygen saturation (SpO₂), Newborn and infant Parasympathetic Evaluation (NIPE), and Face, Legs, Activity, Cry, Consolability (FLACC) scores. Comfort, PP, and procedures were compared using paired t-tests and ANOVA. Normal pain responses were defined as increases in HR, MBP, RR, and FLACC, and decreases in SpO₂ and NIPE. Logistic regression identified predictors of normal responsiveness; linear regression assessed factors affecting response magnitude.

Results: A total of 102 examinations were analyzed (PP=34, A=10, V=13, H=45). Compared with comfort, PP increased HR, MBP, RR, and FLACC, and decreased SpO₂ and NIPE. All procedures combined raised HR, MBP, and FLACC, and lowered NIPE; RR and SpO₂ were not significant. Arterial puncture increased HR, MBP, and FLACC; venipuncture increased HR and FLACC; heel lance increased HR and FLACC, and decreased SpO₂ and NIPE (Table 1). FLACC differed across procedures, being higher in A and V versus H (Table 2). Among puncture exams, 60.4% of preterm and 60.1% of term infants showed normal responses, with no difference in magnitude (Table 3). Female infants had higher odds of normal MBP response (OR 3.06, 95% CI 1.09-8.56), while greater GA, BW, and PMA were inversely associated with normal RR responses. No other baseline factors influenced the likelihood or magnitude of a normal pain response.

Conclusion(s): Both procedural and non-procedural stressors, particularly pre-prandial fasting, elicited measurable changes. HR and FLACC were the most reliable indicators, whereas RR and SpO₂ were less sensitive. NIPE responsiveness was inconsistent, with the most pronounced changes during heel lance. Pain response magnitude did not differ between preterm and term infants, but sex and maturity influenced patterns. These findings highlight the need for multimodal, individualized pain assessment in the NICU.

Table 1. The comparisons of pre-prandial and punctures with comfort
Data shown as mean (±SD)
* Marked on p <0.05
Abbreviations: HR, heart rate; MBP, mean blood pressure; RR, respiratory rate; FLACC, face-leg-activity-cry-consolability; NIPEm, Mean Newborn and Infant Physical Examination

Table 2. The comparisons of the punctures
Data shown as mean ± SD
* Marked on p <0.05
P values are computed using 1-way ANOVA

Table 3. The amount of changes in pain parameters in normal responders
Data shown as mean ± SD
P values are computed using independent two sample T test