Perfusion index as an objective measure of postoperative pain in children undergoing adenotonsillectomy: a cohort study.

Postoperative pain in children is usually undertreated because of their inability to complain. While several pain assessment scales have been developed, they have shortcomings such as subjectivity and being observer-dependent. This study aimed to assess the validity of the perfusion index as an objective measure of postoperative pain in children undergoing adenotonsillectomy. Children aged 3-7 years were enrolled. The Children's Hospital of Eastern Ontario Scale (CHEOPS) was used to assess postoperative pain. The perfusion index was measured at the same time intervals as CHEOPS. The highest CHEOPS before rescue analgesia was administered and CHEOPS when the patients became pain-free were recorded with the corresponding perfusion index. The primary outcome was the correlation between the postoperative CHEOPS and the corresponding postoperative perfusion index. The secondary outcomes were the ability of perfusion index changes to predict the presence of postoperative pain and patients' response to analgesics. The postoperative perfusion index was negatively correlated with CHEOPS at 30 and 90 min postoperatively. The change in the preoperative baseline perfusion index (ΔPI-pre) was moderately correlated with the highest CHEOPS (CHEOPS-1) (r = 0.61, p = 0.001). The change in the postoperative perfusion index (ΔPI-po) was negatively correlated with the change in the CHEOPS (ΔCHEOPS) (r = - 0.53, P = 0.0001). The ΔPI-pre was an excellent predictor of postoperative pain (AUROC 0.83 with 71% sensitivity, 83% specificity, and a cut-off value of ≥ 0.26). The perfusion index is a good objective measure for predicting the presence of postoperative pain in children undergoing adenotonsillectomy under general anesthesia. Trial registration: ClinicalTrials.gov; ID: (NCT03854604) registered on February 2019.