The effect of tourniquet release time on the analgesic efficacy of intraarticular morphine after arthroscopic knee surgery

Abstract

A randomized, controlled study was conducted in patients undergoing elective arthroscopic knee surgery to assess the effects of tourniquet release time on analgesia after intraarticular (I.A.) injection of morphine. Standardized general anesthetic and surgical techniques were used for all patients, including a thigh tourniquet inflated at pressures between 300 and 350 mm Hg. At the conclusion of the arthroscopic procedure, 5 mg morphine in 25 mL saline was administered I.A. Patients were then randomized to one of two treatment groups. In Group 1 (n = 20), the tourniquet was kept inflated for 10 min after I.A. injection, whereas in Group 2 (n = 20), the tourniquet was deflated immediately after I.A. injection. Postoperative pain was assessed using a visual analog scale in the recovery room when the patients were awake and at 2, 4, 6, 8, and 24 h after I.A. injection. Patients who complained of pain in the recovery room received increments of intravenous meperidine 25-50 mg. On discharge from the recovery room, patients received oral mefenamic acid 250-500 mg for pain relief. The time and quantity of analgesics required were recorded. Patients in Group 1 had significantly (P < 0.05) lower pain scores than those in Group 2 at 2, 4, 6, and 8 h postoperatively. These low pain scores were associated with lower requirements of supplementary analgesics. We conclude that, as compared with releasing the tourniquet immediately after I.A. injection of morphine, maintaining the tourniquet inflated for 10 min provides superior analgesia and decreases the need for supplemental analgesics.