Pain relief after arthroscopic knee surgery: intravenous morphine, epidural morphine, and intra-articular morphine

OBJECTIVE: The aim of this study was to compare the analgesic efficacy and side effects of intravenous (IV), epidural, and intra-articular (IA) morphine after arthroscopic knee surgery. DESIGN: Prospective, randomized, double-blind clinical investigation. SETTING: Medical center, university teaching hospital. PATIENTS: Inpatients with an American Society of Anesthesiologists physical status of I or II who were scheduled for elective arthroscopic knee surgery. INTERVENTIONS AND OUTCOME MEASURES: A total of 75 patients scheduled for arthroscopic knee surgery under epidural anesthesia were randomly divided into three groups (n = 25 in each group). At the end of surgery, patients in group 1 received 3 mg of IV morphine, patients in group 2 received 3 mg of epidural morphine, and patients in group 3 received 3 mg of IA morphine. Patients were then observed for 24 hours. During the observation period, the proportion of patients requiring rescue analgesia with intramuscular diclofenac in each group was calculated and the occurrence of morphine-related side effects was recorded. RESULTS: We found that patients who received IV morphine requested more rescue analgesia than those who received either epidural or IA morphine. The proportions of patients requiring rescue analgesia in the IV, epidural, and IA groups were 65%, 13%, and 9%, respectively (p < 0.01 in group 1 vs. group 2 and in group 1 vs. group 3). Epidural morphine was associated with higher incidences of nausea and vomiting, pruritus, and urinary retention than IA morphine (range, p < 0.05-0.01 in group 2 vs. group 3). CONCLUSIONS: Patients who received IA morphine consumed less rescue analgesia than those who received IV morphine. They also reported fewer side effects than those patients who received epidural morphine. Intra-articular morphine may be the method of choice for pain relief after arthroscopic knee surgery.