| Objective:Our study plans to observe the serum levels ofMBP,motor function recovery and ultra microstructure of spinal cordafter continuous spinal anesthesia with polyurethane microspinalcatheters administration of different desity and dose ropivacaine in SDrats in 48 hrs.Methods:Ninety-six male SD rats weighing (280±20mg/kg) wereanesthetized. A polyurethane microspinal catheter was inserted into thelumbar subarachnoid space 8cm according to the method of Yaksh's.Theanimals were randomly divided into 4 groups of 24 animals each:in groupN the animals were given normal saline 40μl intrathecal every one andhalf hours for three times; in group R1 0.5％ropivacaine was given, ingroup R2 0.75％ropivacaine and group R3 1％ropivacaine were given asbefore. The motor function was assessed by modified Rivlin slope trialand BBB score before catheter insertion(T0), before intrathecalinjection(T1),after the last intrathecal administration 6h (T2), 12h (T3),24h(T4) and 48h(T5). Groups were divided in to four subgroups accordingto the last four time points(n=6 in each subgroup).Then 0.5ml blood wascollected from femoral artery for MBP determination, and animals weresacrificed and L1-2 segment of spinal cord and nerve roots wereimmediately removed for electron microscopic examination.Results:1.SBP(systolic blood pressure) in group N remains stable.SBP in group R1,R2,R3 decreased to different degree after the intrathecaladministration, and rised after 60min. SBP lower than 90mmHg isabsent.2.The respiratory frequency and extent, water and food intake,and free running of group N were the same after the intrathecaladministration.In group R1,R2,R3 in 15～30sec after every intrathecaladministration,hindlimbs muscle relaxed, movement disturbed;while theforward limb and neck movement maintained normal. In group R1,R2,R3hindlimbs muscular tension recovered 30～90min after intrathecaladministration.No respiratory depression, restlessness,convulsion,comaand death was observed in group R1,R2,R3.BBB scores before and aftercatheter insertion between group N,R1,R2 and R3 are insignificant(P＞ 0.05).BBB scores of group R3 between T2～T5 and To are significant (P＜0.01 ).The slope trial scores before and after catheter insertion betweengroup N,R1,and R3 are insignificant(P＞0.05).The critical angle of groupR3 at T2～T5 is reduced,and the slope trial scores between T2～T5 and Tois significant (P＜0.01).3.MBP levels at different time points: MBPlevels in N, R1,R2 group were notsignificantly different,while in R3 groupMBP levels were dissimilar compared with other three groups, afterintrathecal administration 6h (P＜0.05).MBP level of R3 group wassignificant higher at T2,T3,T4 and T5 compared with that at T0, T1 (P＜0.01).4.Ultramicrostructure of spinal cord of group N in T2, T3, T4 andT5 is normal. Electronmicroscope of R3 in T2, T3, T4 revealed partialneuronal shrinkage, electron density widening, petaloid ambulacranucleolemma, neurocyte degeneration, intracytoplasm cell organdegeneration. Ultramicrostructure of R3 in T5 is similar to T4 exceptindividual severe neurocyte degeneration. Ultramicrostructure of spinalcord of R3 in T2, T3, T4 and T5 is significant compare with group N andR1,R2. (P＜0.05).Conclusions1. 0.5％and 0.75％Ropivacaine intrathecal administration cause nomotor function deficits and spinal cord injury in 48hrs.2. 1％Ropivacaine may be injurious to spinal cord in 48hrs,andinadvisable for continuous spinal anesthesia.3. The serum levels of MBP is one of diagnosis makers for spinal cordinjury. |
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