Safety of local anesthetics administered intrathecally in diabetic rats

Although retrospective studies show the risk of neurological complications after spinal anesthesia with local anesthetics is small in diabetic patients, there is still concern about the safety of different local anesthetics in diabetics undergoing neuroaxial anesthesia. We examined block duration and histology of spinal cord and roots with intrathecal local anesthetics in diabetic rats.

Rats were made diabetic with streptozotocin injection. Blood glucose levels confirmed diabetes, and diabetic neuropathy was verified by tactile hypersensitivity. Diabetic and nondiabetic rats received four intrathecal injections at 3-4-day intervals of 0.75% bupivacaine, with/without 100 µg/mL epinephrine; and 2% lidocaine, with/without 100 µg/mL epinephrine, and duration of sensory (pinprick) and motor (toe-spreading reflex) response inhibition recorded. Four days after the last drug injection, histology of spinal cord and roots was performed.

All streptozotocin rats became diabetic and had pronounced tactile allodynia. Intrathecal injection of local anesthetics showed longer duration of sensory and motor block in diabetic rats vs nondiabetics. Histology of caudal spinal cord showed no difference in neuropathology between diabetic and nondiabetic rats. Necrotic neurons were not seen in either group, and white-matter pathology involved less than 0.1% of fibers. Histology of the spinal roots also showed no difference in pathology between groups, and pathology involved less than 0.1% of fibers. Neuron somas in the dorsal root ganglia were normal.

Duration of local anesthetic spinal block is longer in diabetic animals than in nondiabetics. However, there was no increased pathology of spinal cord, roots, or dorsal root ganglia.