DEXMEDETOMIDINE PREMEDICATION BEFORE INTRAVENOUS REGIONAL ANESTHESIA IN MINOR OUTPATIENT HAND SURGERY

Study Objective: To assess the efficacy and safety of intravenous (IV) dexmedetomidine, an alpha-2 agonist, as a Premedication before IV regional anesthesia. Design: Randomized, double-blind, placebo-controlled study with two parallel groups. Setting: Day-case surgery unit, Department of Surgery, Turku University Hospital, Turku, Finland. Patients: 30 healthy ASA Physical status I outpatients scheduled for minor hand surgery with IV regional anesthesia. Interventions: Patients were assigned to one of two groups to receive either dexmedetomidine 1 mu g/kg IV(n = 15) or saline placebo IV (n = 15) 10 minutes before exsanguination and inflation of a tourniquet. Regional blockade was induced with 0.5% lidocaine 3 mg/kg (maximum 200 mg). Additional fentanyl 1 mu g/kg intraoperatively and oxycodone 0.05 mg/kg postoperatively were administered for analgesia if needed. Measurements and Main Results: Dexmedetomidine preoperatively induced 16% to 20% decreases in systolic blood pressure (p < 0.001), diastolic blood pressure (p < 0.001), and heart rate (p < 0.001), which were mainly abolished within the 4-hour postoperative follow-up period. A clinically significant decrease in arterial oxygen saturation was not observed. The subjective intensity of pain during tourniquet inflation was similar in both groups, but fewer intraoperative (p = 0.009,) opioid analgesics were needed in the dexmedetomidine group. Dexmedetomidine decreased sympathoadrenal responses: plasma norepinephrine concentration decreased to one-fourth of the baseline level (p < 0.001), and one of its main metabolites, 3,4-dihydroxyphenylglycol, decreased by 27% (p < 0.001). Dexmedetomidine also prevented an increase in plasma epinephrine concentration following tourniquet inflation (p = 0.003). Dexmedetomidine induced subjective sedation (p = 0.002), but the Maddox Wing test did not show any statistically significant differences between the groups. General effectiveness was graded superior in the dexmedetomidine group (p < 0.001). Conclusions: Dexmedetomidine is an effective premedication before IV regional anesthesia because it reduces patient anxiety, sympathoadrenal responses, and opioid analgesic requirements.