Efficacy of lipophilic vs lipophobic opioids in addition to hyperbaric bupivacaine for patients undergoing lower segment caeserean section

BACKGROUND: Subarachnoid block is the preferred technique for providing anesthesia for patients undergoing cesarean section. Various pharmacological agents in added to local anesthetics (LA) modify their original effects in terms of block characteristics and quality of analgesia. However, there is ongoing debate about this practice of using adjuncts with LA. We tested whether addition of lipophilic versus lipophobic opioids to LA gives any clinical benefits to maternal and fetal outcome when used in these patients requiring spinal anesthesia. SUBJECTS AND METHODS: Sixty American Society of Anesthesiologists I and II parturients, undergoing elective cesarean section requiring subarachnoid block, were included in our study. The parturients were allocated randomly to three groups of 20 each to receive bupivacaine 12.5 mg (Group I), bupivacaine 12.5 mg + morphine 0.2 mg (Group II), bupivacaine 12.5 mg + fentanyl 25 μg (Group III), preservative free physiological saline 0.9% was added to all the solutions to achieve a total volume of 4 ml. The parameters studied were the time of onset, sensory level of the block achieved, total duration of analgesia, any need of rescue analgesics, maternal side effects, and fetal outcome. RESULTS: Onset of block was early 4.30 ± 0.12 min in Group III as compared to Group I 4.64 ± 0.28 min and Group II 4.505 ± 0.22 min. Mean duration of analgesia (hours) was higher in Group II 15.91 ± 0.96 h as compared to Group I 1.95 ± 0.55 h and Group III 4.39 ± 0.2 h. Incidence of nausea, vomiting, and shivering was more in the control group as compared to study groups, whereas sedation and pruritus were seen more in the study groups. No adverse effects on fetus were seen with use of opioids and comparable Apgar scores were noted. CONCLUSION: Addition of intrthecal fentanyl causes rapid onset of block whereas intrathecal morphine provides prolonged analgesia with comparable neonatal wellbeing.