COMPARATIVE, TOXICITY OF GLUCOSE AND LIDOCAINE ADMINISTERED INTRATHECALLY IN THE RAT

Background and Objectives. Glucose is a common component of anesthetic solutions used for spinal anesthesia. However, its possible contribut ion to recent injuries occurring with spinal anesthesia has not been a dequately addressed. Accordingly, the present studies compare the func tional and morphologic effects of intrathecally administered glucose w ith those of lidocaine. Methods. Twenty rats, implanted with intrathec al catheters, were divided into three groups to receive a 1-hour infus ion of 5% lidocaine (n = 6), 10% glucose (n = 7), or normal saline (n = 7). Four days after infusion, animals were evaluated for persistent sensory impairment using the tail-nick test. Three days later, the ani mals were sacrificed, and the spinal cord and nerve roots were examine d by a neuropathologist blinded to the solution received and the resul ts of sensory testing. Results. Lidocaine-treated animals exhibited pe rsistent sensory impairment, whereas glucose- and saline-treated anima ls did not. Neuropathologic evaluation revealed moderate to severe ner ve root injury in lidocaine-treated animals. Histologic changes in glu cose- and saline-treated animals were minimal, similar, and restricted to the area adjacent to the catheter. Morphologic damage associated w ith lidocaine preferentially affected the nerve roots, with relative s paring of the spinal cord and dorsal root ganglia. Conclusions. These results suggest that, at clinically relevant concentrations, glucose d oes not induce neurologic injury, providing indirect evidence that rec ent clinical injuries occurring after spinal anesthesia resulted from a neurotoxic effect of the local anesthetic. Additionally, the present studies suggest that deficits resulting from neurotoxicity of intrath ecally administered anesthetic result from injury to the axon.