Dexmedetomidine (DMT) has been shown to prolong spinal anaesthesia. We evaluated the effects of intravenous DMT on low‐dose bupivacaine spinal anaesthesia in elderly patients.

Fifty‐one elderly patients undergoing transurethral resection of the prostate were randomized into two groups receiving either 1.0 μg/kg DMT (DMT group, n = 26) or normal saline (control group n = 25) intravenously prior to spinal anaesthesia with 1.2 ml of bupivacaine, 5 mg/ml.

The mean time to two‐segment regression (39 min vs. 78 min for cold, 41 min vs. 61 min for pinprick) and that to motor regression (23 min vs. 46 min) were longer in the DMT group than in the control group. The atropine‐requiring bradycardia was more frequent in the DMT group than in the control group (24.0% vs. 3.8%). The median sedation scores (ranges) during surgery were 4 (2–6) in the DMT group and 2 (1–3) in the control group (P < 0.001). Two patients in the DMT group showed oxygen desaturation (peripheral oxygen saturation < 90%) during surgery. The duration of post‐operative care unit stay was longer in the DMT group than in the control group (58 min vs. 96 min). Post‐operative pain intensity was lower and the mean time to first request for post‐operative analgesia was longer in the DMT group compared to the control group (6.6 h vs. 2.1 h).

Intravenous DMT prolonged the duration of spinal anaesthesia and improved post‐operative analgesia. However, more profound sedation with desaturation was observed with more frequent bradycardia, and delayed recovery should be considered in elderly patients.