The periarticular multimodal cocktail injection including morphine is currently commonly used to treat postoperative pain after total knee arthroplasty (TKA). Despite its analgesic effect, it is frequently reported to cause nausea and vomiting, which are adverse effects of opioids. This study aimed to assess the efficacy of morphine as a component of a multimodal cocktail injection for providing postoperative analgesia and alleviating swelling in patients who underwent TKA.
This is a prospective, single-center, randomized controlled trial involving 102 patients scheduled for unilateral TKA. A mixture of steroids, local anesthetics, nonsteroidal anti-inflammatory drugs, and epinephrine with or without morphine (10 mg) was injected to randomly assigned patients. Postoperative assessment was performed with all attending personnel and patients blinded to group assignment. Visual analog scale of pain, range of motion, nausea numerical rating scale, number of patients with vomiting, total dose of antiemetic drugs used, thigh swelling, the Western Ontario and McMaster Universities Osteoarthritis Index score, and adverse outcomes were compared between groups on postoperative days.
Visual analog scale scores did not differ between the 2 groups at any postoperative time point. The nausea numerical rating scale scores during the postoperative period from 30 min to 9 h, the number of vomiting episodes, and the total dose of antiemetic drugs administered were significantly higher in the morphine group. The thigh girth, Western Ontario and McMaster Universities Osteoarthritis Index, and the incidence of complications were not different between groups.
The results of this study suggested that addition of morphine to the multimodal cocktail injection is not effective for relieving postoperative pain, alleviating swelling, or improving range of motion, and results in nausea and vomiting.