Variations in physiological responses to painful stimuli in preterm and term neonates: an observational study

Background: Appropriate neonatal pain assessment and management is a key component of quality medical care. Assessment of pain, however, is a challenge due to their inability to verbalize this subjective sensation. Preterms are hyper-sensitive to pain and experience it for prolonged periods but it is postulated that they may not express it as robustly and reliably as term neonates. This paper aims to assess and compare the behavioral and physiological pain responses in these groups. Methods: This prospective observational study was conducted in the outpatient and post-natal wards of a tertiary care teaching hospital. 90 clinically stable term and late preterm neonates requiring IV cannulation, IV blood sampling or heel prick were included. NIPS Pain Scale Scores and physiological parameters (heart rate, respiratory rate, SpO2, mean arterial pressure, total crying time) were recorded before and after the procedure. Results: 90 neonates were analysed. Significant pain response was noted in both groups post-procedure. In response to the same procedures, preterm neonates demonstrated lower NIPS Scores (4.00 vs. 4.93, P=0.003) and shorter cry times (64.30s vs. 87.35s, P=<0.05). Also noted were higher heart rates and respiratory rates with a prolonged fall in SpO2 and Mean Arterial Pressures in this group. Conclusions: Preterms, compared to term neonates demonstrate a blunted behavioral response to pain but a heightened and prolonged physiological response. This potential underestimation of pain in preterms indicate the need for incorporation of behavioral cues, physiological parameters and gestational age in the assessment of pain in newborns.