半紧闭系统吸入麻醉药提取的研究

Uptake of inhalation anesthetics in semiclosed system.

为探讨吸入麻醉药的摄取规律，选择４６例心肺功能正常的患者，年龄１９～６５岁，拟全麻下行非开胸手术。随机分７组：分别吸入１％、１．５％、２％异氟醚和安氟醚及５０％氧化亚氮。患者于气管插管后行机械通气，潮气量１０ｍｌ·ｋｇ－１，呼吸频率１２ｂｐｍ，氧流量３Ｌ·ｍｉｎ－１。监测吸入浓度出现时间、吸入浓度、呼出浓度及吸一呼浓度差，以吸一呼浓度差作为摄取指标。结果显示：１％和１．５％异氟醚吸入浓度出现时间明显短于等浓度的安氟醚。各组在开启挥发器２～３分钟内，吸一呼浓度差曲线逐渐上升，达峰值后３０分钟内几乎恒定不变。吸入５０％氧化亚氮，吸一呼浓度差在前５分钟迅速下降，继而渐降。结论：（１）吸入麻醉药出现时间及浓度国麻醉机系统对各药的吸收程度不同而异；（２）在患者实际摄取麻药前，有２～３分钟的平衡过程；（３）氧化亚氮的摄取主要在前５分钟，持续吸入３０分钟后摄取量甚微。

To investigate the uptake process of inhalation agents, forty-six patten.ts,aged 19-65 years, ASA grade Ⅰ to Ⅱ, scheduled to undergo elective nonthoracic operations, were randomly divided into 7 groups. Following intubation the lungs were mechanically ventilated at the oxygen flow rate of 3L·min-1 and the frequency of 12 bpm and tidal volume of 10ml·kg-1. The subjects of 7 groups inhaled 1%, 1.5%, 2% of isoflurane (I) or enflurane (E), or 50% nitrous oxide,respectively. The onset times of inspiratory concentrations were measured. The difference in concentration between inspiration and expiration (C1-CE) was used as the parame ter for uptake of inhalation anesthetic. The results showed that onset time of inspuratory concentration of I was signifiCantly shorter than that of E, with concentrations of I% and 1. 5 %, but not with 2%. Following administration of I or E at each concentration, the level of CI CE was ascended gradually to the peak value in 2 to 3 mins, then kept constant during the subsequant procedures, while CI-CE of 50% nitrolls oxide showed a rapid decrease in first 5 min followed by a further gradual decrease during 30 min. It is concluded that the difference in the onset time of inspiratory concentration between 1 and E mainly results from different absorption of various anesthetic by the delivery system. Prior to the process of stable uptake, an equilibrium within the patient's lung is required about 2-3 mln, which may be related to anesthestic vapor's being diluted by function residual capacity. The nitrous oxide is uptaken mainly in the first 5 min following administration.