Background and aims: Moderate to severe immediate postoperative pain remains frequent after major and even minor-to-medium level surgical procedures. Pain relief has been found to be undermanaged and distressing to patients and staff alike. This prospective study aims to determine the predictive factors of opioid requirement of patients in PACU.
Methods: We collected details from adult patients undergoing elective surgery who were admitted to PACU including characteristics as well as anesthetic-related, surgical-related and PACU-related data. Continuous and categorical variables are compared between patients who received and did not receive opioids in PACU, using univariate analysis. Associations between potential predictors and use of opioid are evaluated using multivariate logistic regression. 
Results: Of 1,977 patients, 848 patients (42.9%) received opioid in PACU. From multivariate analysis, anesthetic techniques including monitor anesthesia care (MAC), target controlled infusion (TCI), spinal anesthesia and neuraxial block are predictive factors for not using opioid in PACU. General surgery, gynecological surgery, reoperation, intraoperative blood transfusion and verbal numerical pain score (VNRS) upon PACU arrival are predictive factors for receiving opioid in the immediate postoperative period.
Conclusions: The predictive factors for patients’ requirement of opioid in PACU are general and gynecological surgeries, reoperation, intraoperative blood transfusion as well as VNRS.

FACTORS RELATED TO AMOUNT OF ANALGESIC REQUIREMENT IN POST-ANESTHESIA CARE UNIT (PACU): A PROSPECTIVE STUDY