Efficacy of Intravenous Acetaminophen for Postoperative Analgesia in Primary Total Knee Arthroplasty.

Background: The use of intravenous acetaminophen has seen recent enthusiasm as one component of a multimodal approach to pain management. However, there is a lack of literature examining the efficacy of intravenous acetaminophen for pain control in total joint arthroplasty. The purpose of this study was to evaluate the efficacy of intravenous acetaminophen following primary total knee arthroplasty.

Methods: This is a retrospective review of 38 patients undergoing primary total knee arthroplasty by a single surgeon at one institution. Twenty-five patients received 1 gram of intravenous acetaminophen every 6 hours for 24 hours postoperatively. Thirteen patients received no additional intervention. Exclusion criteria were bilateral or concomitant procedures, allergy to medications included in the standard postoperative protocol, neuropathy or sensory disturbances, history of opioid dependence or abuse, deviations from protocol, revision procedures, and incomplete data. Primary outcomes were change in patient-reported visual analog scale (VAS) pain score, overall opioid consumption measured in morphine milligram equivalents, and hospital length of stay.

Results: We found no difference in length of stay, at 3.3 days in the control group and 2.9 days in the intervention group. There was a significant difference in VAS score between 16 and 24 hours. There was a statistically significant decrease in overall opioid consumption in the intravenous acetaminophen group 37.6 vs 18.6 morphine milligram equivalents.

Conclusion: Intravenous acetaminophen is effective in significantly reducing opioid requirements in the first 24 hours following primary total knee arthroplasty. Additionally, there is a clinically significant decrease in VAS pain scores in patients receiving this intervention.