Height-based dose adjustment of bupivacaine for combined spinal-epidural anesthesia in elective caesarean section

WU Chang-yi; ZHANG Li-ping

Abstract：Objective:To investigate the height-based dose adjustment of bupivacaine for combined spinalepidural anesthesia in elective caesarean section. Methods: One hundred ASA Ⅰ～Ⅱ nulliparous pregnant women at term were randomly assigned to two groups. They were given 0. 5% hyperbaric bupivacaine 1.7 mL (group A, n =50) , or a volume of 0.5% hyperbaric bupivacaine adjusted according to the patient's height (group B, n =50). Spinal puncture was performed at L_(3-4) interspace. A catheter was inserted 4 cm in the epidural space cephalad. If spinal analgesia was inadequate, 1.75 % lidocaine carbonates was given epidurally. The following indicators were assessed : anesthesia time (from spinal injection to supine position, t_1), time required for block height to reach or above T_4(t_2), numbers of patients with sensory block to T_4or above T_4(N_1), maximum sensory block height (T_(max)) and numbers of patients with sensory block to T_(max)and blood pressure. The clinical efficacy was rated as 0 ～Ⅲ (0 = worst, Ⅲ = best) based on analgesia, muscle relaxation and visceral traction response. Apgar score of the neonates, occurrences of nausea and vomiting, hypotension (decrease in systolic blood pressure >30% or <90 mmHg) and ephedrine requirements were recorded. Results: Adequate anesthesia was provided inall patients in both groups. No differences in T_1, T_2, T_(max) or the dosage of epidural lidocaine carbonates were observed (P > 0.05). There were no significant differences in the incidence of maternal nausea and vomiting or in neonatal outcome as assessed by Apgar scores (P >0.05). The numbers of patients with sensory block to T_4 or above T_4, and the numbers of patients with sensory block to T_2 were higher in group A than in group B (P < 0. 01). Hypotension occurred in 54% vs 32% of patients, respectively, in group A and group B (P < 0.05), and ephedrine requirements were less in group B (P < 0.05). Conclusion : The height-based dose adjustment of bupivacaine for combined spinal-epidural anesthesia in elective caesarean section results in a reduced incidence of hypotension and less ephedrine requirements.