A prospective randomised double blind study of intrathecal fentanyl and dexmedetomidine added to low dose bupivacaine for spinal anesthesia for lower abdominal surgeries

Background and Aims: The potentiating effect of short acting lipophilic opioid fentanyl and a more selective a2 agonist dexmedetomidine is used to reduce the dose requirement of bupivacaine and its adverse effects and also to prolong analgesia. In this study, we aimed to find out whether quality of anaesthesia is better with low dose bupivacaine and fentanyl or with low dose bupivacaine and dexmedetomidine. Methods: This prospective randomised double-blinded study was carried out in a tertiary health care centre on 150 patients by randomly allocating them into two groups using a computer generated randomisation table. Group F (n = 75) received bupivacaine 0.5% heavy (0.8 ml)fentanyl 25 mu g (0.5 ml) normal saline 0.3 ml and Group D (n = 75) received bupivacaine 0.5% heavy (0.8 ml) dexmedetomidine 5 mg (0.05 ml) normal saline 0.75 ml, aiming for a final concentration of 0.25% of bupivacaine (1.6 ml), administered intrathecally. Time to reach sensory blockade to T10 segment, peak sensory block level (PSBL), time to reach peak block, time to two segment regression (TTSR), the degree of motor block, side-effects, and the perioperative analgesic requirements were assessed. Results: There were no significant differences between the groups in the time to reach T10 segment block (P > 0.05) and TTSR (P > 0.05);time to reach PSBL (P < 0.05) and modified Bromage scales (P < 0.05) were significant. PSBL (P = 0.000) and time to first analgesic request (P = 0.000) were highly significant. All patients were haemodynamically stable and no significant difference in adverse effects was observed. Conclusion: Both groups provided adequate anaesthesia for all lower abdominal surgeries with haemodynamic stability. Dexmedetomidine is superior to fentanyl since it facilitates the spread of the block and offers longer post-operative analgesic duration.