Aim/objectives/background: Angiotensin-converting enzyme inhibitors (ACEIs) increase potent proinflammatory and pain mediators in local tissues. Consistent with these observations, animal and human studies demonstrate that ACEIs have hyperalgesic and proinflammatory properties. However, there is no information in literature whether or not the use of ACEIs is associated with increased postoperative pain. Specifically, we tested the primary hypothesis that use of ACEIs is independently associated with increased opioid requirements and pain scores during the initial 72 hours after surgery.
Methods: Data from 9993 patients undergoing colorectal resection, hysterectomy, nephrectomy, or open prostatectomy were obtained from the Cleveland Clinic Perioperative Health Documentation System. A propensity-matching procedure was used to pair ACEI users to similar nonusers. Corresponding estimates and Bonferroni-adjusted 95% confidence intervals for the effect of ACEIs on each outcome were also estimated. The exact matching procedure, based on type of surgery and propensity score, identified 1038 matched pairs. The final analyzed subsample size was 212.
Results and conclusions: The adjusted difference in mean 72-hour postoperative using a time-weighted average pain score was estimated at +0.17 [-0.40, +0.74] units on the verbal response scale. This was not statistically significant (P=0.50). Opioid use was estimated by the percent difference in mean 72-hour total postoperative intravenous morphine equivalent dose at -8.1% [-46%, +56%], which was not statistically significant (P=0.72). In conclusion, after controlling for all available factors, we found no significant difference that postoperative pain-as defined by either pain scores or opioid requirements-differed between patients taking ACEIs and patients not taking ACEIs.