低流量紧闭麻醉时异氟醚吸入和呼出浓度与时间及挥发罐开启浓度的关系

The relations among Inspired or expired isoflurane concentration and anaesthesia duration or/and vaporizer output concentration during low-flow closed circuit anaesthesia

目的 探讨低流量紧闭麻醉（ＬＦＣＣＡ）时异氟醚吸入浓度（Ｃｉ）和呼出浓度（Ｃｅ）与时间（Ｔ）及挥发罐开启浓度（Ｃｏ）的关系。方法 选４３例ＡＳＡⅠ～ Ⅱ级择期手术需气管内全麻的患者行静吸复合麻醉，按Ｃｏ不同将患者随机分为三组，Ⅰ、Ⅱ、Ⅲ组Ｃｏ分别为１．５％、３．０％、５．０％。氧流量固定为０．５Ｌ·ｍｉｎ^（－１），持续静注异丙酚以维持适当麻醉深度。用Ｄａｔｅｘ监测仪监测Ｃｉ、Ｃｅ。用最小二乘法求出 Ｃｉ、Ｃｅ与时间及Ｃｏ的相关方程。结果 在 ２４０分钟的观察中，Ｃｅ和 Ｃｉ未达到相等，Ｃｅ／Ｃｉ随时间延长而增大。Ｃｉ、Ｃｅ与时间呈线性相关。Ｃｏ越大，相关方程的斜率越大，即Ｃｉ、Ｃｅ随时间上升越快。Ｃｉ、Ｃｅ与时间、Ｃｏ之间亦呈线性相关。结论 在ＬＦＣＣＡ时，Ｃｉ、Ｃｅ随时间的延长而升高，随Ｃｏ的增大而升高加快，因此在实施过程中，随着麻醉时间的延长，应调整Ｃｏ，以防麻醉过深。

Objective To evaluate the relations among inspired or expired isoflurane concentration (Ci, Ce) and anaesthesia duration (T ) or/and vaporizer output concentration (Co ) during lowflow closed circuit anaesthesia(LFCCA). Methods Under intravenous combined inhalational anaesthesia, 43 ASA gradeⅠ or Ⅱ patients undergoing elective surgical procedure,were randomly divided into 3 groups according to the different Co,the Co of group Ⅰ,Ⅱ or Ⅲ was 1. 5%,3. 0% or 5. 0% respectively. The fresh oxygen flow was fixed at 0.５L· min^(-l). Simultaneously,propofol was continuously administered via vein to achieve adequate anaesthesia depth. Datex monitor was applied to measuring Ci and Ce. The coeffecients and regression equations among Ci or Ce and T and /or Co,were worked out by least square method. Results Ci and Ce did not equilibrate during 240-min inhalational anesthesia. The ratio of Ce/Ci increased following anaesthesia. There was linear correlation between Ci or Ce and T ;The higher Co,the higher sloope of the equation,meaning Ci and Ce increased more rapidly. There also was linear correlation among Ci or Ce and T and Co. Conclusion The prolongation of LFCCA duration requires lowering properly the vaporizer output concentration in order to prevent deep anesthesia,