Effect of Intravenous Acetaminophen on Postoperative Opioid Consumption in Adult Orthopedic Surgery Patients.

: Postoperative pain is managed with opioids, which are associated with adverse effects. The efficacy of intravenous (IV) acetaminophen in reducing opioid consumption has been studied with inconsistent results. The primary outcome of this study was to assess the effect of IV acetaminophen on opioid consumption 24 hours postoperatively. Secondary outcomes included the opiate consumption at 48 hours after the operation, opioid-related side effects 72 hours after the operation, discharge disposition, and length of stay. This was an IRB-approved, retrospective cohort study including adult patients who underwent an elective total knee arthroplasty (TKA). Patients were stratified into IV and no IV acetaminophen groups; patients who had received at least one dose of IV acetaminophen were included in the IV acetaminophen group. Total opioids were collected, converted to morphine equivalents, and compared between groups. Patients were excluded for alcohol abuse, substance abuse treatment, non-elective TKA, or medication mischarting. : Of the 161 patients evaluated, 148 patients were included: 86 in the IV acetaminophen and 62 in the no IV acetaminophen group. There were no differences in mean morphine equivalents between groups postoperatively at 24 hours (54.2 ± 35.9 mg vs 45.4 ± 30.2 mg; = .12) and 48 hours (99.2 ± 68.7 mg vs 79.5 ± 49.1 mg; = .06). There were no differences in secondary outcomes (administration of bowel regimen medications, antiemetics, naloxone, discharge disposition, or length of stay) between the groups. : The use of IV acetaminophen was not associated with a decrease in opiate use, opiate-related side effects, or any secondary outcomes in patients who underwent TKA.