Dexmedetomidine premedication before intravenous regional anesthesia in minor outpatient hand surgery.

STUDY OBJECTIVE: To assess the efficacy and safety of intravenous (i.v.) dexmedetomidine, an alpha-2 agonist, as a premedication before i.v. 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 i.v. regional anesthesia.

INTERVENTIONS: Patients were assigned to one of two groups to receive either dexmedetomidine 1 microgram/kg i.v. (n = 15) or saline placebo i.v. (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 microgram/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 i.v. regional anesthesia because it reduces patient anxiety, sympathoadrenal responses, and opioid analgesic requirements.