effect of dexmedetomidine as an adjunct to ultrasound guided modified four-in-one block for perioperative analgesia in arthroscopic knee surgery

Arthroscopic knee surgery commonly causes postoperative pain, which is challenging to manage. with the advent of ultrasound, peripheral nerve blocks of the lower limb have become widely accepted. this study evaluated the efficacy of a single injection of modified four-in-one block with or without dexmedetomidine for perioperative analgesia in arthroscopic knee surgery. one hundred patients undergoing elective arthroscopic knee surgery were randomized into two equal groups to receive an ultrasound-guided modified four-in-one block. group i received 0.25% bupivacaine (30 ml), while group ii received bupivacaine (30 ml) plus 50 µg dexmedetomidine. patients were assessed for sensory block onset, postoperative pain, need for analgesia, and total analgesic consumption on the first postoperative day. sensory block onset was significantly delayed in group i (6.76 ± 1.34 min) compared to group ii (2.76 ± 0.74 min). pain severity (vas) was significantly reduced in group ii at early postoperative time points (5, 15, 30, and 60 minutes; 2 and 4 hours). the need for postoperative analgesia was significantly higher in group i (40.0% vs 20.0%). furthermore, group i experienced a significantly shorter time to first analgesic request (3.95 ± 0.75 hours vs. 12.90 ± 2.02 hours) and required a significantly higher total amount of analgesics (diclofenac: 67.5 ± 21.61 mg vs. 40.0 ± 12.90 mg) than group ii. these findings suggest that adding dexmedetomidine to local anesthetics as an adjunct for arthroscopic knee surgery significantly improves postoperative pain control and reduces postoperative analgesic requirements.