Comparison of ropivacaine and lidocaine for intravenous regional anesthesia in volunteers - A preliminary study on anesthetic efficacy and blood level

Background: Ropivacaine may bet useful for intravenous regional anesthesia, but its anesthetic effectiveness and toxicity have not been evaluated. Methods: Two doses of ropivacaine (1.2 and 1.8 mg/kg) and one dose of lidoc aine (3 mg/kg) were compared for intravenous regional anesthesia in 15 volu nteers. An arm tourniquet was inflated for 30 min after injection and then deflated in two cycles. Sensory block was measured by response to touch, co ld, pinprick, and transcutaneous electric stimulation, and motor function w as measured by hand grip strength and muscle power. Median, ulnar, radial, and musculocutaneous nerve functions were tested before local anesthetic in jection and then at 5-min intervals until blocks resolved. The plasma ropiv acaine and lidocaine concentrations were determined from arterial and venou s blood samples drawn from the unanesthetized arm. Results: Sensory and motor blocks were complete within 25 min and 30 min, r espectively, in all three treatment groups. However, recovery of sensory an d motor block after tourniquet release was slowest In the high-dose ropivac aine group. Anesthesia to pinprick and transcutaneous electric stimulation was sustained in all the volunteers in the high-dose ropivacaine group for 55 min and 85 min, respectively, whereas complete recovery was observed in the lidocaine group (P = 0.008) and partial recovery in the low-dose ropiva caine group (P < 0.05) during the same period. Motor block also was sustain ed in the high-dose ropivacaine group for 70 min, which was significantly l onger than in the lidocaine group (P < 0.05). All volunteers (five of five) given lidocaine and one volunteer given high-dose ropivacaine reported lig ht-headedness and hearing disturbance during tourniquet release when the ar terial plasma lidocaine and ropivacaine concentrations were 4.7 +/- 2.1 mu g/ml (mean) and 2.7 mu/ml, respectively. Conclusion: Compared with lidocaine, intravenous regional anesthesia with r opivacaine appears to be comparable but has longer-lasting residual anesthe sia.