Bilateral intravenous regional anesthesia: a new method to test additives to local anesthetic solutions

BACKGROUND: Ketorolac, when added to lidocaine, has been shown to reduce early tourniquet pain during intravenous regional anesthesia (i.v.RA) in patients. Although the effectiveness of ropivacaine 0.2% for i.v.RA is equal to that of lidocaine 0.5% but significantly reduces central nervous system side effects after release of the tourniquet, it provides no advantage with regard to tourniquet tolerance times. Simultaneous bilateral i.v.RA with ropivacaine 0.2% was used to test the hypothesis that ketorolac modifies tourniquet tolerance and to test whether drug combinations can be evaluated in one study session. METHODS: Ten healthy, unsedated volunteers received 30 ml of ropivacaine 0.2% in each upper arm with 2 ml of normal saline in one arm and 30 mg of ketorolac in the contralateral arm for i.v.RA. Both proximal tourniquets remained inflated for 30 min, followed by inflation of the distal tourniquets and release of the proximal ones. Verbal numeric scores for tourniquet pain were recorded for both extremities. Central nervous system side effects were graded after release of each distal tourniquet. RESULTS: There was no difference between the two upper extremities with regard to surgical anesthesia and tourniquet tolerance. Total tourniquet tolerance was a median of 58.5 min (range, 45-90 min) and 60.5 min (39-79 min) in the normal saline and ketorolac groups, respectively. After release of the distal tourniquets, 5 of 10 volunteers experienced mild dizziness. CONCLUSIONS: The addition of ketorolac to ropivacaine does not improve tourniquet tolerance. Minimal central nervous system side effects after tourniquet release suggest that a total of 60 ml ropivacaine 0.2% for bilateral i.v.RA is a useful model for comparison of i.v.RA drug combinations.