静吸复合麻醉下小儿血中碳氧血红蛋白浓度的变化

Carboxyhemoglobin blood concentration during desflurane and enflurane anesthesia in children

目的 通过三种静吸复合麻醉条件下检测小儿血中碳氧血红蛋白(COHb)浓度的变化,评价其用于小儿的安全性。方法 行择期手术的患儿24例,根据使用吸入麻醉药及设置的新鲜气流量(FGF)的不同随机分为3组:Ⅰ组(地氟烷,500ml/min)、Ⅱ组(地氟烷,2000ml/min)和Ⅲ组(安氟烷,500ml/min),新鲜气流中O2:N2O为1:1。分别于机械通气前、后30、45、60min测定动脉血中COHb浓度,监测机械通气过程中各时点吸入麻醉药呼气末浓度(Cexp)、MAC等值。结果 (1)Ⅰ组和Ⅲ组:COHb在60min时点值高于其他时点值。Ⅱ组:COHb在45min时点值高于其他时点值。(2)Ⅰ组和Ⅱ组地氟烷Cexp分别为3.93％-4.24％、4.31％-4.43％,各时点相比差异无显著性(P>0.05);Ⅲ组安氟烷Cexp为0.87％-0.93％,与Ⅰ组相比各时点MAC值差异无显著性(P>0.05)。(3)Ⅰ组与Ⅱ组相比较、Ⅰ组与Ⅲ组相比较:各时点COHb浓度差异无显著性(P>0.05)。结论 含水量为6.08％以上的钠石灰、Cexp为0.87％～0.93％安氟烷或Cexp为3.93％～4.24％地氟烷(合并使用N2O)以及500ml/min FGF,这些条件可以安全地联合应用于机械通气在60min以内的小儿静吸复合麻醉;同样条件下,Cexp为4.31％-4.43％地氟烷和2000ml/min FGF同时应用于机械通气在60min以内的小儿静吸复合麻醉是安全的。

Objective To evaluate the safety of desflurane and euflurane anesthesia in children in terms of carboxyhemoglobin (COHb) blood concentration. Methods Twenty-four ASA Ⅰ - Ⅱ children weighing 18-30 kg undergoing elective surgery under general anesthesia were randomly assigned to one of three groups : group Ⅰ , desflurane FGF 500 ml·min-1 ( n = 8); groupⅡ , desflurane FGF 2000 ml ·min-1 ( n = 8) and group Ⅲ, enflurane FGF 500 ml·min-1 (n = 8) . The patients were premedicated with atropine 0.01 mg·kg-1 and diazepam 0.2 mg·kg-1 . Ketamine 2 mg·kg-1 was given im before induction of anesthesia. Radial artery was cannulated when the patients fell asleep, for BP monitoring and blood sampling. Anesthesia was induced with fentanyl 2μg·kg-1 , propofol 2 mg · kg-1 and vecuronium 0. 1 mg·kg-1 . The patients were mechanically ventilated after intubation. PET CO2 was maintained at 35-40 mm Hg. The inspired concentration of desflurane or enflurane was set at 1.0-1.3 MAC which was maintained throughout anesthesia. FGF rate was set at 2500 ml·min-1 ( O2/ N2O = 1000 ml /1500 ml) to accelerate the uptake of inhaled anesthetics during the first 15 min of mechanical ventilation, then reduced to 500 ml·min-1 in group Ⅰ and Ⅲ or 2 000 ml ·min-1 in group Ⅱ as planed. Blood samples were taken before induction of anesthesia (T0 , baseline) and at 30, 45, 60 min of mechanical ventilation (T1-3) for determination of blood Hb and COHb concentrations. Results The demographic dala and preoperative Hb were comparable among the three groups. The water content of the soda lime was 6.5%±0.3% when unpacked and was reduced to 6.1%±0.4% when kept in the anesthesia machine ovemight. In group Ⅰand ⅢCOHb concentration increased gradually from T1 and reached the peak value at T3 and in group Ⅱ COHb concentration peaked at T2 (45 min) . The end -tidal desflurane concentration was 3 .93% - 4.24% in group Ⅰ and 4. 3%-4. 43% in group Ⅱ. The end-tidal enflurane concentration was 0.87%-0.93%. There was no significant difference in end-tidal concentration of desflurane and euflurane in terms of MAC between group Ⅰ and Ⅲ ( P > 0.05) . There was no significant difference in COHb concentration between group Ⅰ and Ⅱ as well as group Ⅰand Ⅲ ( P > 0.05) . Conclusion It is safe to use soda lime containing more than 6.08% of water during enflurane or desflurane anesthesia with low flow (FGF = 500 ml·min-1 ) in children.