Evaluation of Intra-Articular Morphine for Postoperative Analgesia in Knee Arthroscopy as Compared to Bupivacaine

Abstract

There exists evidence that in addition to their central effects opioids can produce potent antinociceptive effects by interacting with opioid receptors in peripheral tissue. This study sought to compare the effects of morphine administered intra-articularly with those of bupivacaine following arthroscopic knee surgery. Methodology A double blind randomized study was conducted in patients undergoing elective knee arthroscopy to assess the effect of intra-articular morphine and bupivacaine alone and in combination. Patients in the control group (C) (n = 20) received 20 mL of 0.9% Normal Saline. Patients in the morphine group (M) (n = 20) received 5 mg of morphine in 20 mL of normal saline. The Bupivacaine group (B) patients received bupivacaine (0.25%) 20 mL. Twenty patients received a combination of 5 mg morphine and 20mL of 0.25% bupivacaine (BM). All solutions contained 1:200,000 adrenaline. All the drugs were injected intra-articularly at the end of operation and postoperative pain was assessed using Visual Analogue Scale at 0, 1, 6, 12, 24 hr after intra-articular injection. The need of analgesic supplement was recorded. Results Our result indicated that, in patients undergoing arthroscopic knee surgery, intra-articular bupivacaine results in good analgesia in the immediate postoperative period (i.e., 0 hr). In contrast, intra-articular morphine failed to provide significant analgesia during the same period. However the delayed analgesic effect was poor in the bupivacaine group as compared to groups M and BM. In all three active treatment groups (B, M, BM) there was a decrease in pain score when compared with placebo. The combination group had the best results with both early and delayed analgesia. Conclusion We conclude that combination of these drugs (bupivacaine+morphine) results in satisfactory analgesia following knee arthroscopy.