To compare dexmedetomidine administered via different routes for epidural anesthesia during second cesarean section.

Sixty parturients who were at full term with a singleton fetus, of American Society of Anesthesiologists physical statusⅠor Ⅱ, aged 22-38 yr, weighing 58-84 kg, undergoing a second caesarean section under epidural anesthesia, were divided into 3 groups(n=20 each)using a random number table: IV infusion of dexmedetomidine combined with epidural injection of ropivacaine group(VDER group), epidural injection of a mixture of ropivacaine and dexmedetomidine group(ERD group)and epidural injection of ropivacaine group(ER group). The epidural puncture was performed at L_{2, 3}.After identification of the epidural space and a negative aspiration test for blood or cerebrospinal fluid, the mixture of 0.75% ropivacaine 15 ml and 0.9% normal saline 2 ml was injected epidurally, and dexmedetomidine 1 μg/kg was intravenously infused for 10 min at the same time in VDER group; the mixture of 0.75% ropivacaine 15 ml and 1 μg/kg dexmedetomidine 2 ml was injected epidurally in ERD group; the mixture of 0.75% ropivacaine 15 ml and 0.9% normal saline 2 ml was injected epidurally in ER group.The onset time of epidural block, maximum level of epidural block, time to reach the maximum epidural block and time of sensory block were recorded.Ramsay sedation scores were assessed at 30 min after the end of epidural administration, and intraoperative traction reaction was also assessed.The development of hypotension, bradycardia, respiratory depression and shivering was observed.The number of patients in whom remifentanil was used before delivery and Apgar scores at 1 and 5 min after birth were recorded.

Compared with VDER group and ER group, the onset time and time to reach the maximum epidural block were significantly shortened, and the time of sensory block was prolonged in ERD group(P<0.05). Compared with ER group, the rate of satisfactory sedation was significantly increased, the number of patients in whom remifentanil was used before delivery was decreased, the degree of intraoperative traction reaction was mitigated, and the incidence of respiratory depression and shivering was decreased(P<0.05), and no significant change was found in Apgar scores at 1 and 5 min after birth in VDER and ERD groups(P>0.05).

Both IV and epidural dexmedetomidine can enhance the efficacy of epidural anesthesia during second cesarean section, producing no adverse effects on neonates; epidural injection of a mixture of ropivacaine and dexmedetomidine provides faster onset and prolonged time of sensory block, which is helpful for postoperative analgesia.

Dexmedetomidine; Anesthesia, epidural; Cesarean section; Scar uterus