Predictive value of surgical pleth index for early postoperative pain in children undergoing general anesthesia: A prospective observational study

Background: Postoperative pain is common in children during early recovering from general anesthesia, especially for pediatric patients undergoing adenotonsillectomy surgery. There is no valid tool to predict postoperative pain at present. Methods: One hundred and fifty patients aged 4–8 years, scheduled to undergo adenotonsillectomy surgery were enrolled in the clinical trial. All patients were given intravenous general anesthesia and endotracheal intubation by the same pediatric anesthesiologist. Surgical pleth index (SPI) monitoring for each patient was performed from the same shared SpO ₂ measurement finger which was on the side opposite to the NIBP measurement through the CARESCAPE Monitor B650 (GE Healthcare, Helsinki, Finland). The SPI values, mean arterial pressure (MAP) and heart rate (HR) were recorded at each minute for five minutes immediately after surgery. The maximum values of SPI, MAP and HR (SPI _max , MAP _max and HR _max respectively) were taken for analysis. Early postoperative pain was assessed for each patient using the modified Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS) in postanesthesia care unit (PACU). Receiver-operating characteristics (ROC) curves and the associated areas under the curves (AUC) were computed to analyze the ability of SPI to predict early postoperative pain. Results: One hundred and thirty-two patients were included and analyzed finally. The SPI _max , MAP _max and HR _max of the patients whose CHEOPS scores less than 4 were 43±6, 58±9mmHg and 90±12 beat/min while of the patients whose CHEOPS scores equal or greater than 4 were 54±8, 67±11mmHg and 96±13 beat/min respectively. The SPI (AUC: 0.84, 95% CI: 0.74-0.92, P<0.001) had a good predictive value for postoperative moderate-to-severe pain compared with MAP (AUC: 0.53, 95% CI: 0.41-0.67, P=0.58) and HR (AUC: 0.62, 95% CI: 0.46-0.76, P=0.19). The best-fit (highest combined sensitivity and specificity ) cut-off values of SPI to distinguish mild pain from moderate-to-severe pain was 46 with the sensitivity of 79.4% and specificity of 87.8%. Conclusions: SPI can effectively predict the occurrence of early postoperative moderate-to-severe pain in pediatric patients undergoing adenotonsillectomy surgery under general anesthesia. SPI might be one reliable pain assessment tool to guide pediatric anesthesiologists for timely identification and management of postoperative pain. Trial registration: Chinese Clinical Trial Registry, identifier: ChiCTR2200058658 (13/04/2022).