Intrathecal morphine for postoperative analgesia: A randomized, controlled, dose-ranging study after hip and knee arthroplasty

In this series, we examined analgesia and side effects of intrathecal morphine sulfate (ITMS) after hip and knee arthroplasty over a dose range of 0.0-0.3 mg. Eighty patients undergoing hip (n = 40) or knee (n = 40) arthroplasty were randomized to receive ITMS (0.0, 0.1, 0.2, or 0.3 mg). A patient-controlled analgesia (PCA) device provided free access to additional analgesics. Morphine use, pain relief, and side effects were recorded for 24 h. Data were analyzed with analysis of variance and linear regression. After hip arthroplasty morphine use was less in patients receiving 0.1, 0.2, or 0.3 mg of ITMS than in control patients (P < 0.05). After knee arthroplasty, ITMS did not reduce Postoperative morphine requirements. Nausea and vomiting and the incidence of oxygen saturation < 93% were similar in all groups. Pruritus was more common after ITMS. Patients receiving 0.2 or 0.3 mg of ITMS were more satisfied with their pain control than those receiving 0.0 or 0.1 mg after both hip and knee arthroplasty. Analgesic needs are greater after knee arthroplasty than after hip arthroplasty. We conclude that combining small-dose (0.2 mg) ITMS with PCA morphine provides good to excellent pain control in most patients after total hip or knee arthroplasty. However, PCA morphine use was reduced by the addition of ITMS only after hip arthroplasty.