低流量紧闭麻醉时安氟醚吸入浓度的探讨

Evaluation of Inspiring Concentration of Enflurane at the Time of LFCCA

目的 探讨低流量紧闭麻醉 (LFCCA)时安氟醚吸入浓度 (Fi)与氧流量、挥发罐开启浓度 (Fo)及时间 (T)的关系。方法 根据吸入麻醉药的摄取量 =吸入浓度 (% )×摄取分数 (1—Fe/Fi)×肺泡通气量(ml/min) ;肺泡通气量≌ (0 3Kg +3)× 16 0ml/min ;吸入麻醉药的摄取量 =挥发器的输出量 -排出气体所带走的麻醉药量 =氧流量×Fo -排出的气体量×Fi=氧流量×Fo - (氧流量 -氧气摄取量 )×Fi;氧气的摄取量≌(0 3Kg +3)× 10ml/min ;得出 :Fo/Fi=(3Kg +30 ) (16摄取分数 - 1)÷氧流量 +1;选择ASAⅠ～Ⅱ级择期手术需气管内全麻的患者行静吸复合麻醉 ,麻醉开始后前 10min氧流量 5L/min ,Fo=2 % ;并根据气体监测结果适当调整Fo ,使Fi=2 % ,10min后改低流量 ,并按氧流量不同随机分为四组 ,Ⅰ、Ⅱ、Ⅲ、Ⅳ组氧流量分别为0 4L/min ,0 6L/min ,0 8L/min ,1 0L/min ,并分别于麻醉开始后 10min ,30min ,…… 190min时分别监测SP ,DP ,HR、SpO2 % ,Fi,安氟醚呼出浓度 (Fe) ,MV ,PetCO2 ,调整Fo使Fi=2 % ,比较实际观测Fo和公式计算Fo。结果 实际观测Fo和公式计算Fo无显著性差异 (P >0 0 5 )。结论 Fo/Fi=(3Kg +30 ) (16摄取分数- 1)÷氧流量 +1可以指导麻醉医师在无麻醉气体监护下施行LFCCA。

Objective To evaluate relationship between inspired concentration of Enflurane(Fi),oxygen flow,unbolted concentration of volatile(Fo)and time(T).Methods In view of the following formulas:uptake of inspired anesthetic=inspired concentration(%)×uptake faction(1-Fa/Fi)× alveolar ventilation(ml/min),alveolar ventilation≌(0 3Kg+3)×160ml/min,uptake of inspired anesthetic=out put of volatile-losing dose of anesthetic with expiration=oxygen flow×(Fo-losing dose)×Fi=oxygen flow×Fo-(oxygen flow-oxygen uptake)×Fi,oxygen uptake≌(0 3Kg+3)×10ml/min,then the last formula:Fo/Fi=(3Kg+30)(16 uptake faction-1)÷oxygen flow+1 was worked out,Twenty-four ASA grade Ⅰ～Ⅱ patients undergoing selective surgery with intratracheal general anesthesia were given vein-inhalation anesthesia.The oxygen flow is equal to 5L/min,Fo=2% at the first ten minutes.According to gas monitoring Fo was adjusted to make Fi=2%;low flow was used after ten minutes,then the patients were randomly divided into four groups.In group Ⅰ,Ⅱ,Ⅲ and Ⅳ,oxygen flow was maintained at 0 4L/min,0 6L/min,0 8L/min and 1 0L/min respectively.The time of monitoring SP,DP,SpO 2%,Fi,Enflurane expired concentration(Fa),MV,P et CO 2 were 10min,30min,......190min after anesthesia and adjust Fo to make Fi=2%.We compared actual Fo with computative Fo.Results Actual Fo and computative Fo have no significant differences( P <0 05).Conclusion The last formula:Fo/Fi=(3Kg+30)(16 uptake faction-1)÷oxygen flow+1 can be used to direct anesthetist to perform low-flow closed-circuit anesthesia.