Does the type of arthroscopic surgery modify the analgesic effect of intraarticular morphine and bupivacaine? A preliminary study

Objective: To analyze the different analgesic response to intraarticular morphine and bupivacaine in different types of arthroscopic surgery. Design: Prospective, randomized and double-blinded. Fifty-three consecutive patients undergoing an arthroscopic knee procedure under general anesthesia. They were studied separately in 2 groups (types of surgery): (1) "Low inflammatory surgery": diagnostic arthroscopy, partial meniscectomy; and (2) "High inflammatory surgery": ACL (anterior cruciate ligament) reconstruction, lateral release, patellar shaving and plicae removal. At the end of the procedure, patients were randomized to receive 25 mL of bupivacaine 0.25% with epinephrine (1/200,000), 5 mg of morphine, or saline (placebo) into the knee joint. Postoperative pain was determined through the visual analog scale (VAS). Supplemental analgesia (ketorolac) was administered via intravenous patient-controlled analgesia (IV PCA). Pain and requirements of analgesia were compared between bupivacaine, morphine, and placebo in each group of surgery. Results: When considering only the "Low inflammatory" group of patients, those who received bupivacaine showed a lower postoperative pain score at 4 and 8 hours (P < 0.05). When considering only the "High inflammatory" group, the patients who received morphine showed a lower postoperative pain score at 24 hours and less requirements of ketorolac (P < 0.05). Conclusions: The analgesic effect of morphine and bupivacaine is different depending on the type of arthroscopic surgery. Intraarticular bupivacaine is effective in surgeries with a low inflammatory response. For surgeries with a higher inflammatory response, morphine has a better analgesic effect. Postoperative intraarticular analgesic therapy should be indicated according to the performed arthroscopic procedure.