Evaluating the Effect of Intravenous Acetaminophen in Multimodal Analgesia After Total Hip Arthroplasty: A Randomized Controlled Trial

Postoperative pain is a significant concern of patients before surgery. Multimodal pain management is an effective method of pain control after major orthopedic surgery. Acetaminophen is the most commonly used analgesic for the management of pain. It was hypothesized that 1000 mg of intravenous acetaminophen (IA) dosed every 6 hours would significantly reduce the postoperative pain score at rest and the opioid consumption volume in patients who would undergo total hip arthroplasty (THA) when compared to a control group.

A single-center, prospective, open-label randomized control study was conducted. A total of 97 patients undergoing unilateral primary THA were divided into 2 groups: the study group (IA) (n = 45) and the control group (n = 52). The study group received administered IA after surgery, while the control group received only a standard pain control. Both groups received a preoperative femoral nerve block and postoperative intravenous fentanyl citrate. The primary outcome was the evaluation of the pain score at rest 24 hours after surgery. The pain score was measured using the Numerical Rating Scale. The primary outcome of this study was analyzed using generalized estimating equation.

The IA group had a significant improvement in Numerical Rating Scale score at rest 24 hours after THA compared to the control group (−0.91, 95% confidence interval −1.56 to −0.26, P = .006), suggesting a positive effect of IA usage for pain relief. The total fentanyl citrate consumption after surgery for 24 hours was significantly lower in the IA group than those of the control group (52.07 ± 7.64 vs 57.83 ± 12.44 mg, P < .001).

Postoperative administration of IA significantly reduced the postoperative pain score and opioid consumption volume after primary THA. IA was useful as one role of multimodal pain management after THA.

Level of Evidence: Level 2.