Effect of Oral Ketamine on the Postoperative Pain and Analgesic Requirement Following Orthopedic Surgery

Background: Ketamine is a potent analgesic agent in addition to its anesthetic properties. Oral ketamine has been used to treat postoperative stump pain following lower limb amputation. In this study, oral ketamine was used to reduce the severity of postoperative pain following orthopedic surgery. Methods: Seventy-two adult traumatic patients undergoing orthopedic operations were randomly divided into ketamine and placebo groups. In ketamine group, oral ketamine administered at 8-hour intervals postoperatively. Severity of postoperative pain, amount of morphine used, and the time to first rescue analgesic were determined and compared between two groups. Results: Patients in ketamine group had significantly lower scores of postoperative pain (5.2 ± 1.2, 4.9 ± 1.6, 4.4 ± 2.2, 4.3 ± 1.5, and 3.4 ± 1.3 at 2, 4, 8, 16, and 24 h postoperatively vs. 7.7 ± 1.5, 7.3 ± 1.6, 6.3 ± 1.9, 6.0 ± 1.6, and 5.1 ± 1.8 in placebo group; P < 0.05). The amount of morphine required in the first postoperative day was significantly lower in ketamine group (10.1 ± 5.6 mg vs. 13.4 ± 7.8 mg in placebo group; P < 0.05). Time to first rescue analgesic in the ward was significantly longer in ketamine group (3.5 ± 1.5 h vs. 1.9 ± 1.2 h in placebo group; P < 0.05). A female patient in ketamine group developed postoperative emergence reaction following extubation. Conclusions: Oral ketamine may be used to reduce postoperative pain following orthopedic procedures in the traumatic patients. Since only one patient developed psychological side effect (which we can not attribute to ketamine with certainty) it can be concluded that oral ketamine is not so fearsome with respect to emergence reaction.