Effect of ondansetron on sensory level produced by intrathecal bupivacaine

Abstract

Background: For spinal anesthesia there are drugs which can increase the level and quality of analgesia. Any drug which decreases sensory block level in spinal anesthesia is of great concern as it may need analgesic, sedative, supplement or even conversion to general anesthesia. Ondansetron is one such drug which has been reported to decrease the height of sensory block achieved after subarachnoid administration of bupivacaine. In this prospective observational study, we studied the effect of administration of ondansetron on the level of the sensory block achieved after subarachnoid blockade. Methods: In Group II, 4 mg ondansetron was given and 15 mins before giving spinal anesthesia Group II against control group receiving 2 ml saline intravenous (Group I). 15 mins before giving spinal anesthesia. Both groups received 3.5 ml of bupivacaine heavy was given intrathecally. Sensory and motor block was assessed 5, 15, and 30 mins. We analyzed both highest spinal block level achieved and time to regress to L1 level. Results: We found that in Group II both highest level of sensory block (T6 by median method) duration to regress to L1 level (1.43±0.22 hrs) was lesser as compared to group I and Group III T4 by median method and time to regress from T6 to L1 Group I 2.03±0.06 hrs Group III 1.84±0.27 hrs. Motor block did not differ between groups. Conclusions: We concluded that probably ondansetron was responsible for lower spinal block level and early recovery from spinal anesthesia after intrathecal bupivacaine and should not be given empirically for nausea and vomiting.