Effect of combination lidocaine with bupivacaine or ropivacaine on the spinal neurotoxicity in rats / 临床麻醉学杂志

ABSTRACT

Objective To observe spinal cord neurotoxicity injury induced by mixture of bupiv-acaine-lidocaine compared with mixture of ropivacaine-lidocaine.Methods Forty-eight SD rats,weig-hing 250-300 g,were randomly allocated into 6 groups (n =8)NS group (group N),1.065% bupi-vacaine group (group B),1.5% ropivacaine group (group R),5% lidocaine group (group L),mix-ture group of 5% lidocaine and 1.065% bupivacaine (group LB)or mixture group of 5% lidocaine and 1.5% ropivacaine (group LR).The rats were given intrathecal cathetering after anesthesia.Tail-flick test (TFL)and the mechanical withdrawal threshold (MWT)of rats in each group were meas-ured 1 d before operation (the baseline values)and 1 d,2 d,3 d and 4 d after intrathecal administra-tion.The movement of rat double hind legs were observed at 10 min,30 min,1 h,2 h,3 h and 4 h and 1 d,2 d,3 d and 4 d after intrathecal administration,and the changes of recovery time of lower limbs were recorded.The rats were sacrificed 4 days postoperatively followed by observation on the indexes mentioned above,and spinal cord and cauda equine were taken for staining.Then the patho-logical changes of spinal cord were observed under light and electron microscope,and caudal nerve was rated for pathological injury.Results TFLs of group LR were obviously longer than those of group N,L,B,R,LB 1-4 d after intrathecal administration (P <0.05);Compared with the group N,there was no statistical difference of TFL in the group L,B,R,LB;there was no statistically sig-nificant difference of rat MWT in comparison among the six groups at each time point.There was no statistically significant difference among six groups in recovery time of movement after intrathecal ad-ministration;and the pathological injury scores were obviously higher in group LR than that of group N,L,B,R,LB (P <0.05),respectively.Compared with the group N,there was no statistical difference of the pathological injury scores in the group L,B,R and LB,respectively.Under light microscopy observa-tionthe structure of spinal cord was normal in group N,B and R.In group L and LB,there was focal ede-ma of neurofibers.In group LR,there was edema of neurofibers or demyelination,accompanied with white mass edema in posterior horn of spinal cord.Under electron microscope,only slight edema of medullated fi-bers and unmyelinated nerve fiber was seen in group B and group R;part of the medullated fibers appeared sparse focal lamellar structure in group L and group LB;swelling and degeneration of neuraxon,separation of neuraxon from myelin sheath and disappearance of unmyelinated nerve fiber were seen in group LR. Conclusion The mixture of 5% lidocaine with 1.5% ropivacaine is more neurotoxic to spinal cord than the single administration of lidocaine or ropivacaine,moreover it is not obviously changed compared with the mixture of lidocaine with equipotent bupivacaine.