Effect of clonidine on upper extremity tourniquet pain in healthy volunteers.

Background And Objectives: Tourniquet pain is often a limiting factor during intravenous regional anesthesia (IVRA). The purpose of this study was to evaluate the efficacy of 1 microg/kg of clonidine added to IVRA-lidocaine in decreasing the onset of severe tourniquet pain.

Methods: Upper extremity IVRA was performed in 15 volunteers with a double-cuffed tourniquet on 2 separate occasions at least 1 week apart. IVRA was established with either 40 mL 0.5% lidocaine (IVRA-L) or 40 mL 0.5% lidocaine with 1 microg/kg clonidine (IVRA-Cl). Verbal pain scores (VPS) from 0 to 10 were recorded every 5 minutes. When the VPS reached 6, the distal cuff was inflated, and the proximal cuff was deflated. This was defined as the first tourniquet time (T1). The study was terminated at a VPS of 10, or at 60 minutes, whichever occurred first. The time from distal cuff inflation to deflation was defined as the second tourniquet time (T2). Total tourniquet time (TT) was the sum of T1 and T2.

Results: T1 for IVRA-L (21.6 +/- 3.9) and IVRA-Cl (22.7 +/- 2.7) were not significantly different. T2 and TT were significantly longer (P < .0001; P < .0007, respectively) for IVRA-Cl (33.0 +/- 6.2; 55.6 +/- 6.6) than for IVRA-L (25.5 +/- 4.4; 47.1 +/- 5.2).

Conclusion: This study shows that the addition of 1 microg/kg of clonidine to 40 mL of 0.5% IVRA-L delays the onset time of tourniquet pain in healthy, unsedated volunteers.