Optimum concentration and dose of ropivacaine for caudal block in neonates undergoing laparotomy under general anesthesia: evaluation of postoperative outcome

Objective To investigate the optimum concentration and dose of ropivacaine for caudal block in the neonates undergoing laparotomy under general anesthesia.Methods One hundred pediatric patients of both sexes,aged 9-30 days,weighing 2.5-4.5 kg,scheduled for elective pyloromyotomy,were randomly divided into 5 groups (n =20 each) using a random number table:control group (group C),0.10％ ropivacaine 1.0 ml/kg group (group 0.1％ L1),0.15 ％ ropivacaine 1.0 ml/kg group (group 0.15 ％ L1),0.10 ％ ropivacaine 1.2 ml/kg group (group 0.10 ％ L2),and 0.15 ％ ropivacaine 1.2 ml/kg group (group 0.15 ％ L2).Anesthesia was induced with sevoflurane and cisatracurium.The pediatric patients were tracheally intubated and mechanically ventilated.Remifentanil was infused intravenously at 0.2-0.3 μg· kg-1 · min-1 in group C.In 0.10 ％ L1,0.15 ％ L1,0.10 ％ L2 and 0.15％L2 groups,the corresponding concentrations and doses of ropivacaine were injected into the sacral canal under the guidance of ultrasound.The operation was started at 15 min after administration and sevoflurane was inhaled and the end-tidal concentration of sevoflurane was maintained at 0.8-1.0 MAC.Before induction (T1),at pyloric muscle retraction (T2),and at 4,8,12 and 24 h after operation (T3-6),blood samples were collected from the central vein for determination of plasma concentrations of cortisol and interleukin-6 (IL-6).Pain was assessed using CRIES score at T3-6.When CRIES scores ＞ 3,10％ chloral hydrate 0.5 ml/kg was given by retention enema for analgesia,and the requirement for chloral hydrate was recorded.The emergence time,extubation time,duration of stay in post-anesthesia care unit (PACU) and hospital discharge time were recorded.Bradycardia and hypotension during operation,and development of motor block of lower extremities,infection and dehiscence of incision,vomiting,and urinary retention after operation were also recorded.Results Compared with group C,no significant changes were found in the emergence time,extubation time,duration of stay in PACU,hospital discharge time,plasma concentrations of cortisol and IL-6,the requirement for chloral hydrate,and the incidence of bradycardia,hypotension,motor block of lower extremities,and infection and dehiscence of incision in 0.10％ L1 and 0.15 ％ L1 groups,the emergence time,extubation time,duration of stay in PACU,hospital discharge time were significantly shortened,and the plasma concentrations of cortisol and IL-6,requirement for chloral hydrate,and the incidence of hypotension and infection of incision were decreased in 0.10％ L2 and 0.15％ L2 groups,and the incidence of vomiting and urinary retention was increased in 0.15％ L1 and 0.15％ L2 groups.Compared with group 0.10％ L2,the incidence of vomiting and urinary retention was significantly decreased,and no significant changes were found in the other parameters mentioned above in 0.15％ L2 group.Conclusion The optimum concentration and dose of ropivacaine are 0.10％ and 1.2 ml/kg,respectively,for caudal block in the neonates undergoing laparotomy under general anesthesia. Key words: Amides ; Anesthesia, caudal ; Anesthesia, general; Infant, newborn