Effect of IV Acetaminophen Administration in the Perioperative Period on the Quality of Postoperative Pain Relief and Adverse Side Effects

Background: The administration of intravenous (IV) acetaminophen during the perioperative period has been studied to evaluate its impact on postoperative pain management, opioid-sparing effects, rescue opioid analgesic use, and side effects [e.g., postoperative nausea and vomiting (PONV)]. However, the reports on the impact of the timing of IV acetaminophen administration during the perioperative period have yielded conflicting results. This review synthesizes findings from various studies to provide an understanding of the optimal timing and effectiveness of IV acetaminophen in different surgical settings. Methods: A literature review was conducted to evaluate studies related to IV acetaminophen administration, timing, dosing, and its effects on pain scores, opioid consumption, and common side effects (e.g., PONV). Specifically, the effect of the timing of IV acetaminophen administration (pre-, intrapostoperative, or perioperative) on clinical outcomes was studied. Results: Preemptive administration of IV acetaminophen before the surgical incision can significantly reduce opioid consumption and postoperative pain scores after abdominal and laparoscopic hysterectomy, cesarean surgeries, hip and knee arthroplasty, and endoscopic thyroidectomy. Intraoperative administration of IV acetaminophen during surgery has demonstrated reductions in opioid use and enhanced recovery metrics (e.g., earlier ability to discontinue PCA and advancement to solid food). Postoperative administration in the recovery room has been effective in reducing opioid consumption and improving pain scores, particularly in total knee arthroplasty. However, despite these benefits, some studies reported no significant differences in pain relief or opioid consumption. Comparisons with oral acetaminophen highlight its cost-benefit because even though it is more expensive, the IV formulation is faster-acting. IV administration shows advantages in specific settings like orthopedic surgeries (total knee and hip arthroplasty), major abdominal surgery, abdominal & laparoscopic hysterectomy, endoscopic thyroidectomy, cesarean deliveries, cardiac surgery, and spine fusion. IV acetaminophen achieves peak plasma concentrations rapidly, providing rapid analgesic effects with the recommended dose of 1g, and a maximum daily dose of 4g/day. Some studies suggest that an initial loading dose of 2 g may offer better analgesia. Conclusions: IV acetaminophen administration significantly influences its effectiveness in managing postoperative pain and reducing opioid use. Its most significant impact likely lies in reducing opioid requirements. Opioids carry a substantial risk of adverse events, especially in the postoperative setting. Reducing opioid dependence is a crucial public health goal. Clinicians should consider incorporating IV acetaminophen into multimodal analgesia regimens, emphasizing its benefits in pain control and opioid reduction.