Opioid Use in Knee Arthroplasty After Receiving Intravenous Acetaminophen

BACKGROUND: Intravenous (IV) acetaminophen may be an effective component of multimodal postoperative pain management. The primary objective of this study was to evaluate the impact of IV acetaminophen on total opioid use in postoperative patients. The secondary objective was to evaluate the effect of IV acetaminophen on hospital length of stay. METHODS: This retrospective, case-control study evaluated the impact of IV acetaminophen on total opioid use in surgical patients. Patients were included if they received at least one perioperative dose of IV acetaminophen and underwent a surgical knee procedure. Controls were matched and randomly selected based on procedure type, age, and severity of illness. Postoperative opioids were converted into oral morphine equivalents, and overall use was compared between groups. RESULTS: One hundred patients were enrolled, with 25 patients receiving IV acetaminophen and 75 matched controls. A total of 135 mg versus 112.5 mg oral morphine equivalents were used in the IV acetaminophen group and control group, respectively (p=0.987). There were 45 mg/day oral morphine equivalents used in the IV acetaminophen group versus 37.5 mg in the control group (p=0.845). The median hospital length of stay in both groups was 3 days (p=0.799). CONCLUSION: IV acetaminophen did not significantly decrease postoperative opioid use in patients who underwent surgical knee procedures. In addition, there was a nonsignificant trend toward increased opioid use in the IV acetaminophen group. There was no significant difference in hospital length of stay between the IV acetaminophen group and the control group. These findings require further study in larger patient populations and in other orthopedic procedures that typically require longer hospital stays.