模拟紧闭环路内不同的碱石灰对地氟烷分解反应的比较

目的 研究模拟紧闭环路内三种成分不同的十燥碱石灰与地氟烷发生分解反应生成一氧化碳(CO)的差异。方法 选用钡石灰、国产钠石灰及Sofnolime。在麻醉机的Y-piece端接一贮气囊做为模拟肺。二氧化碳(CO_2)以200ml·min~(-1)的流速通入环路。设定分钟通气量6L·min~(-1),呼吸频率(RR)12次/min,使P_(ET)CO_2在35～45 mm Hg。根据碱石灰的种类不同将实验分为三组,每组实验重复三次。向环路内通入二氧化碳及氧气的同时开启蒸发罐,洗入期开始,当呼气未地氟烷浓度达9％时关闭蒸发罐及新鲜气流,紧闭环路,继续机械通气直至180min。监测 P_(ET)CO_2、重复吸入CO_2分压、地氟烷的吸入、呼出浓度及上下罐反应温度。用气相色谱仪测定CO浓度。结果 三种碱石灰分解地氟烷生成CO的峰浓度及平均浓度由高到低的顺序依次是钡石灰、Sofnolime及国产钠石灰。钡石灰组CO达峰浓度时间明显快于其它两组(P<0.05)。与上罐相比下罐温度上升时间延迟。国产钠石灰组洗入时间较其余两组短。在温度上升期钠石灰组上罐温度上升速度快而钡石灰组下罐温度上升速度快。结论 在模拟紧闭环路内,使用钡石灰发生CO中毒的危险性要高于钠石灰。但仅仅去除钠石灰中的KOH,不能减少吸入全麻药的分解,相反生成CO的量可能增多。

Carbon monoxide produced from degradation of desflurane reacting with different carbon dioxide absorbents in a closed anesthesia circuit

Objective It has been reported that carbon monoxide (CO) forms via reaction between desflurane and CO2 absorbent. The purpose of this study was to determine if there was any difference in formation of CO from degradation of desilurane reacting with different CO2 absorbents in a closed rebreathing circuit. Methods Dry soda lime, sofnolime and baralyme were used. The anesthesia machine used was Datex-Ohmeda Excel 210 SE with standard double canister. A latex bag was connected to the Y piece of the rebreathing circuit, substituting for human lung. 0.2 L.min of CO2 was added to the circuit to simulate the patient's expiratory gas. Ventilation was set to maintain PET CO2 at 35-40 mm Hg. Desflurane vaporizer was turned on during wash-in until end-tidal desflurane concentration reached 9 % . Mechanical ventilation was continued for 180 rain during which end-tidal desflurane concentration was maintained at 9 % . Inspiratory and end-tidal PCO2 , inspiratory and end-tidal desflurane concentration and the temperature of canister were continuously monitored. Gas sampling port was placed between the Y piece and the latex bag. Gas samples were obtained during the first hour of the experiment at 5 , 10, 15, 20, 25, 30, 40, 50 and 60 min, then every 15 min until the end of 180 min for determination of CO concentration by gas chromatography. Results The peak and average concentration oi CO in the circuit was highest with baralyme and lowest with soda lime (baralyme> sofnalime > soda lime). It took significant less time to reach the peak CO concentration with baralyme than with the other two CO2 absorbents. The temperature of top canister went up faster than that of the bottom one with soda lime; whereas with baralyme the temperature of the bottom canister went up faster. Conclusion In a simulated closed circuit the risk of CO poisoning was higher with baralyme than with soda lime. But KOH-free soda lime which still contains NaOH, such as sofnolime, may produce more CO than standard soda lime.