The effect of intrathecal ropivacaine on spinal cord in dogs / 中华麻醉学杂志

ABSTRACT

ve When a new drug is introduced for intrathecal (IT) administration, its effect on spinal cord should be studied for safety reason. The aim of this study was to determine the ultra-microstructure of spinal cord and Ca2+ content in spinal cord after IT administration of ropivacaine in dogs. Methods Eighteen mongrel dogs of either sex weighing about 10kg were randomly assigned to one of three groups according to the dose of ropivacaine administered IT group A received normal saline 2ml IT and served as control; group B received 0.5% ropivacaine 2ml(10mg) IT; group C received 1% ropivacaine 2ml(20mg) IT. Anesthesia was induced with intramuscular ketamine 20mg.kg-1 and atropine 0.05mg?kg-1 and maintained with intermittent iv boluses of ketamine 3mg?kg-1 and fentanyl 5?g?kg-1 Left internal jugular artery was cannulated for intra-arterial pressure monitoring. An incision was made in the back at L3-4 and lumbar puncture was confirmed by aspiration of cerebral-spinal fluid (CSF). Normal saline or ropivacaine was then injected over 20 seconds. 3 hours after IT administration the animals were sacrificed and L1-2 segment of spinal cord and nerve roots were immediately removed for Ca content determination and electron microscopic examination. Results The Ca2+ content of spinal cord was significantly higher in group C than that in group A and B. Electron microscope revealed that in group A and B neurolemma of the nerve root and mitochondria and endoplasmic reticulum of the neurons in spinal cord were intact, while in group C neurolemma was stratified and partly disrupted and mitochondria and endoplasmic reticulum underwent swelling and there was vacuole degeneration. Conclusions Ropivacaine of high concentration or at high dose may be injurious to spinal cord.