THE ADDITION OF 7.5-PERCENT GLUCOSE DOES NOT ALTER THE NEUROTOXICITY OF 5-PERCENT LIDOCAINE ADMINISTERED INTRATHECALLY IN THE RAT

Background: Recent reports of major and minor neurologic sequelae afte r spinal anesthesia have generated concern regarding the safety of som e currently used intrathecal agents. The role of glucose, if any, in n eurotoxic injury associated with spinal anesthesia is not known. The c urrent experiments sought to determine whether the presence of 7.5% gl ucose alters the neurotoxicity of intrathecally administered 5% lidoca ine. Methods: Two experiments were performed. First, 48 rats were impl anted with an intrathecal catheter and randomly divided into eight equ al groups, Each animal received a single intrathecal infusion of 5% li docaine (groups P1-P4) or 5% Lidocaine with 7.5% glucose (G1-G4) for 0 .5, 1, 2, or 4 h at a rate of 1 mu l/min. Sensory function was assesse d using the tail-flick test; a deficit was defined as a complete lack of response to the heat stimulus at the proximal, mid or distal portio n of the tail persisting 4 days after the infusion. In the second expe riment, 60 rats were randomly divided into two groups to receive a 1-h intrathecal infusion of 5% lidocaine or 5% lidocaine with 7.5% glucos e. Animals were evaluated for increase in the latency of the tail-nick reflex 4 days after infusion. Results: In the first experiment, the t wo lidocaine solutions produced similar dose-dependent loss of sensory function. In the second experiment, the two solutions induced similar alterations in tail-hick latency. Conclusions: The presence of 7.5% g lucose does not affect the potential of intrathecally administered 5% lidocaine to induce sensory impairment, These findings provide further support for the hypothesis that recent injuries after spinal anesthes ia resulted from a direct neurotoxic effect of the local anesthetic.