Effect of continuous spinal anesthesia with ropivacaine on the ultrastructuFe of spinal cord and nerve roots in rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of continuous spinal anesthesia with different concentrations and doses of ropivacaine on the ultrastructure of the spinal cord and nerve roots. Methods Twenty-four male SD rats weighing 220-280 g were anesthetized with intraperitoneal 10% chloral hydrate 300-350 mg/kg. A polyurethane microcatheter was inserted into the lumbar subarachnoid space according to the technique described by Yaksh. An 8-cm catheter segment was left in the subarachnoid space. The animals were randomized to receive normal saline, 0.5%, 0.75% or 1.0% ropivacaine 40 ? 1 intrathecally 3 times at 1.5 h interval. Six hours after the first intrathecal administration the animals were decapitated and L1 ,2 segment of the spinal cord and nerve roots were immediately removed for electron microscopic examination. Results Electron microscopic examination revealed that in animals which received intrathecal (i.t.) normal saline, 0.5% or 0.75% ropivacaine the neurolemma of the nerve roots and the mitochondria and endoplasmic reticulum of the neurons in the spinal cord were intact, while in animals which received i.t. 1.0% ropivacaine the neurolemma was stratified and partly disrupted and there were swelling of endoplasmic reticulum and vacuole degeneration. Conclusion Six hours continuous spinal anesthesia with 1.0% ropivacaine may be injurious to the spinal cord and nerve roots.