Intra-Articular Morphine versus Dexmedetomedine for Knee Arthroscopy under Local Anesthesia

Knee arthroscopy has both diagnostic and therapeutic applications which can be performed under general, regional, or local anesthesia. Morphine is used as an additive to local anesthetics. Dexmedetomedine, the highly selective alpha-2 (α2)-adrenoceptor agonist with the sedative and analgesic effect can be used also to augment local anesthetic effect.

Sixty patients submitted for elective knee arthroscopy whose age between 25 and 45 years, of either sex, the American society of anethesiologists physical status Classes I and II at a university hospital were enrolled in this study. Patients were classified into two groups. Morphine Group (M) (n = 30): Patients received 20 ml of 0.5% bupivacaine plus 5 ml of 0.2% lidocaine with epinephrine 1:200,000 plus 1 mg morphine. Dexmedetomedine Group (D) (n = 30): Patients received 20 ml of 0.5% bupivacaine plus 5 ml of 0.2% lidocaine with epinephrine 1:200,000 plus 1 μg/kg dexmedetomedine.

Demographic data of patients showed no significant difference among the studied groups. Heart rate (HR) was significantly lower in (D) Group compared to that of (M) Group 5 min from the start of procedure to immediately postoperatively. Moreover, (D) Group showed a significant decrease in HR 10 min up to 35 min intraoperatively compared to the basal value. Furthermore, mean arterial blood pressure (MBP) was significantly lower in (D) Group compared to that of (M) Group 15 min from the start of surgery up to 1 h postoperatively. Furthermore, (D) Group showed a significant decrease in MBP 15 min intraoperative up to 2 h postoperatively compared to the basal value. While there was no significant difference in (visual analogue score [VAS], onset and total consumption of ketorolac, surgeon and patients' satisfaction, side effects in (D) Group compared to (M) Group, respectively.

Addition of either morphine or dexmedetomidine to bupivacaine intraarticularly improved both intraoperative anesthesia and postoperative analgesia with minimal side effects or complications in knee arthroscopy, with superiority of dexmedetomidine compared to morphine on hemodynamic stability.