Isoflurane for spinal anesthesia in the rat.

Although isoflurane, a non-water soluble agent, has been known to block Na+ currents, its spinal anesthetic effect was not exposed. The aim of this experiment was to evaluate the local anesthetic effect of isoflurane in spinal anesthesia. After intrathecal injection of isoflurane on rats, the spinal anesthetic effect in motor function, proprioception and nociception were evaluated. Lidocaine, a common used local anesthetic, was used as control. Isoflurane acted like lidocaine and produced dose-related spinal blockades of motor function, proprioception and nociception. Although isoflurane [27.6 (25.4-30.0)] had less potency when compared with lidocaine [1.0 (0.9-1.1)] (P<0.001) in spinal anesthesia, it caused a much longer duration of spinal blockades than lidocaine at equianesthetic doses (P<0.001). Our results showed that when compared with lidocaine, isoflurane produced a less potency but much longer duration in spinal anesthesia.