Cao X, et al. – In this study, researchers compared the analgesic effects and incidence of adverse events associated with intravenous patient-controlled analgesia (iv-PCA) using different sufentanil–tramadol combinations for postoperative pain control. They retrospectively analyzed parturients (n=5,794) who had been scheduled for cesarean section under neuraxial anesthesia and had received iv-PCA between September 2013 and March 2017. With a moderate increase in the concentrations of sufentanil and tramadol administered in iv-PCA over 24 hours after surgery, the investigators observed a decrease in the visual analog scale scores for postoperative pain. A significant reduction in the total sufentanil requirement without increasing the incidence of adverse effects was evident with this analgesic strategy.