Comparative in vitro study of relative anesthetic potency of ropivacaine and lidocaine

Abstract

The purpose of this experimental study was the accurate evaluation of relative anesthetic potency of lidocaine and ropivacaine electrophysiologically in vitro. Total 18 sciatic nerves from male Wistar rats weighing between 250-300 g were used. The sciatic nerves were dissected from the spinal cord to the knee, immersed in a standard saline solution and mounted across a three-chambered recording bath. The 18 nerves were divided in 2 groups. In group A 300 μL of ropivacaine 0.2% and in group B 300 μL of lidocaine 0.2% were applied. Each local anesthetic remained in the perfusion chamber until the reduction of the compound action potential reach the 50% of the originally measured value (IT50) and this reduction was accepted as establishment of anesthesia. Ropivacaine 0.2% was proved to be of statistically less potency regarding the establishment of anesthesia compared to lidocaine 0.2% (p = 0.000497) in the pH of 7.4. The IT50 for the nerves, which came in direct contact with ropivacaine 0.2% was estimated to be 25.28±7.61 min(n = 9). As for lidocaine 0.2% theIT50 was estimated to be 11.78±4.18. © Medwell Journals, 2010.