Epidural bupivacaine suppresses local glucose utilization in the spinal cord and brain of rats

Using the 2-[14C]deoxyglucose method, the effects of analgesic doses of epidural bupivacaine (300 micrograms) on local spinal cord glucose utilization (SP-LGU) of the cervical, thoracic, and lumbar regions and local cerebral glucose utilization (BR-LGU) in 38 brain structures were examined in conscious rats. In addition, the effects of intramuscular bupivacaine (300 micrograms) and the spinal cord transection (T2) were examined to determine whether the induced metabolic changes, if any, are related to the drug's systemic effect and/or deafferentation. Lumbar epidural bupivacaine sufficient to produce analgesia decreased SP-LGU in the thoracic (18-28%) and lumbar (21-29%) spinal cord but not in the cervical cord. Epidural bupivacaine decreased BR-LGU (15-26%) in 35 of 38 structures examined. With intramuscular bupivacaine, SP-LGU remained unchanged in almost all regions, while BR-LGU was significantly decreased (11-23%) in 23 structures. Plasma concentrations of bupivacaine in the epidural and intramuscular groups were comparable. With spinal cord transection alone, SP-LGU significantly decreased with varying degrees depending on the structure examined, but BR-LGU did not decrease in 36 of 38 structures examined. These results indicate that analgesic doses of epidural bupivacaine decrease SP-LGU, probably reflecting decreased neuronal activity of the spinal cord, and that reduced BR-LGU by epidural bupivacaine is most likely due to the drug's systemic effect rather than deafferentation.