The influence of intrathecally admınıstered mıdazolam on analgesıc effects of intrathecally admınıstered ropivacaine on thermal induced pain model in rats

SUMMARYTHE INFLUENCE OF INTRATHECALLY ADMINISTERED MIDAZOLAM ONANALGESIC EFFECTS OF INTRATHECALLY ADMINISTERED ROPIVACAINEON THERMAL INDUCED PAIN MODEL IN RATSDr. Haci Balkaya, Dokuz Eylül University, Faculty of Medicine, Department ofAnesthesiology and Reanimation, Izmir/Turkey.Objective:This study was aimed to investigate whether the addition of midazolam to intratecaladministration of ropivacaine in rats effects analgesic activity and makes histopathologicaleffect to spinal cord.Methods:27 rats were included in the study. Spinal catheter was inserted and affixed to subjects underanesthesia. Subjects were randomised into 5 groups.Group Sham (n= 3): All surgical processes were done except catheter insertion.Group S ( n= 6) : 10 µL of % 0,9 saline was adminestered through the spinal catheters ofsubjects.Group R ( n= 6) : 10 µL ropivacaine including 50 µg ( 5 mg/ mL) was adminestered throughthe spinal catheters of subjects.Group M ( n=6) : 10 µL midazolam including 20 µg was administered through the spinalcatheters of subjects.Group MR ( n= 6) : 10 µL of midazolam and ropivacaine mixture (including 20 µgmidazolam and 50 µg ropivacaine) was adminestered through the spinal catheters of subjects.The catheters were flushed with 10 µL of saline was administration after injection of the studydrugs medicines in all catheter inserted groups. Tail-flick test and rotarod test were performedthe intratecal administration of medicine (0. minute) and at the 10., 20., 30., 45., 60., and 90.minutes after the administration of study drugs. The cross-sections obtained from the spinalcord of rats were histopathologically evaluated.Findings:The tail-flick test?s results showed that when group S with group R, group M and group MRwere compared; the mean values in group R, group M and group MR were significantly high(p<0.05). In the comparison of group R with group M and group MR, the tail-flick test meanvalues of group MR were found significantly high (p<0.05). The rotarod test?s results showedthat when group S was compared with group M and group MR; the mean rotarod values ofgroup M and group MR were found significantly low (p<0.05). No statistical histopathologicsignificance was found between the groups (p>0.05).Conclusion:The analgesic property of ropivacaine when administered intrathecally was augmented byintrathecally administered midazolam without producing any histopathological neurotoxicity.Keywords: Intrathecal, ropivacaine, midazolam, analgesia.