Effects of intrathecal anesthesia with different concentrations and doses on spinal cord, nerve roots and cerebrospinal fluid in dogs

Objective: To investigate the effects of intrathecal anesthesia with bupivacaine, levobupivacaine and ropivacaine hydrochloride at different doses on the spinal cord, nerve roots and cerebrospinal fluid (CSF) in dogs. Methods: Forty-two mongrel dogs were randomly divided into normal saline group (C; 2 ml), 0.5% (B1) and 0.75% (B2) bupivacaine hydrochloride groups (2 ml), 0.5% (L1) and 0.75% (L2) levobupivacaine hydrochloride group (2 ml), 0.5% (R1) and 0.75% (R2) ropivacaine hydrochloride group (2 ml), and drugs were intrathecally injected. Results: The contents of Ca2+ and MDA and SOD activity of the spinal cord were comparable among groups (P > 0.05). In Groups B1, L1 and R1, the neuronal cytoplasm of spinal tissues was basically normal, the majority of mitochondria and endoplasmic reticulum had complete structure, and the lamellar structure of modulated fibers was nearly normal. In Groups B2, L2 and R2, a small amount of mitochondrial vacuolar degeneration was found in the neuronal cytoplasm of spinal cord, but their structures were basically normal; the neural tissues exhibited focal mild edema, and most of the lamellar structure of modulated fibers and Schwann cells were nearly normal except for loose structure in several fibers and cells. Conclusion: When compared with 0.75% anesthetics for local anesthesia, the early adverse effects on the ultrastructure of the spinal cord and nerve root reduce after focal anesthesia with 0.5% anesthetics.