BackgroundThe heart rate variability‐derived Newborn Infant Parasympathetic Evaluation (NIPE™) Index is a continuous noninvasive tool to assess pain and discomfort in infants <2 years. Initial studies focused on pain monitoring in the neonatal intensive care unit environment.AimsThe aim of this study was to investigate the performance of the NIPE in infants under sevoflurane anesthesia. The primary objective of this study was to compare the NIPE and heart rate as tools to help recognize the need for additional opioid drugs. Secondary objectives were the course of the NIPE and heart rate around specific standardized noxious procedural mile‐stones.MethodsNIPE and heart rate values recorded during a 120 seconds interval before the anesthetist's decision to administer additional opioid due to the perceived insufficient antinociception and during a 120 seconds interval after drug administration were analyzed by means of a repeated measures ANOVA. The same analyses were performed for datasets around per protocol administration of morphine for postoperative analgesia, performance of a caudal block and surgical incision.ResultsIn patients with a NIPE value <50, an additional opioid drug administration resulted in a rise of NIPE values, reaching a maximum increase of 5.1 (95% CI: 0.22‐9.99) units 120 seconds after drug administration (P = 0.041). There was no evidence of a change in heart rate during these two 120 seconds periods. Per protocol administration of morphine, caudal block, and surgical incision did not result in changes of the NIPE, which was around 65 units on these occasions, and heart rate.ConclusionIn infants anesthetized with sevoflurane, NIPE values <50 might be indicative of insufficient antinociception. The results of this observational pilot study might suggest that the NIPE could be a better measure of the nociception/antinociception balance than heart rate.

BackgroundThe heart rate variability (HRV)‐derived Analgesia Nociception Index (ANI™) is a continuous noninvasive tool to assess the nociception/antinociception balance in unconscious patients. It has been shown to be superior to haemodynamic variables in detecting insufficient antinociception in children, while little is known about its predictive value.MethodsThe primary objective of this prospective observational pilot study in paediatric surgical patients under sevoflurane anaesthesia was to compare the predictive value of the ANI and heart rate to help decide to give additional opioids. The paediatric anaesthesiologist in charge was blinded to ANI values.ResultsIn patients with an ANI value <50 (indicating insufficient antinociception) at the moment of decision, ANI values dropped from ±55 (indicating sufficient antinociception) to ±35, starting 60 s before decision. Within 120 s after administration of fentanyl (1 μg/kg), ANI values returned to ±60. This phenomenon was only observed in the ANI values derived from HRV data averaged over 2 min. Heart rate remained unchanged. In patients with ANI values ≥50 at the time of decision, opioid administration had no effect on ANI or heart rate. The same accounts for morphine for postoperative analgesia and fentanyl in case of intraoperative movement.ConclusionsThis study provides evidence of a better predictive value of the ANI in detecting insufficient antinociception in paediatric surgical patients than heart rate. The same accounts for depicting re‐establishment of sufficient antinociception after opioid drug administration.SignificanceIn paediatric surgical patients anaesthetized with sevoflurane, the heart rate variability‐derived Analgesia Nociception Index (ANI) appears to be a better predictor of insufficient antinociception than heart rate. The ANI also appears to depict re‐establishment of sufficient antinociception better than heart rate.