Muir W W, Gadawski J
Department of Veterinary Clinical Sciences, Ohio State University, Columbus 43210, USA.
Am J Vet Res. 1998 May;59(5):603-8.
To determine the concentrations of sevoflurane and compound A (a degradation product of sevoflurane) in the anesthetic circuit when sevoflurane was delivered with an in-circuit vaporizer, and to determine the cardiorespiratory effects of sevoflurane in dogs.
6 mixed-breed dogs.
In-circuit vaporizers were connected to the inspiratory limb of a circle rebreathing system connected to a ventilator. A reservoir bag was attached to the Y-piece connector to act as an artificial lung, and sevoflurane concentrations in the anesthetic circuit were measured at vaporizer settings of 1, 3, 5, 7, and 10 and oxygen flow rates of 250 and 500 ml/min. Cardiorespiratory effects of sevoflurane were determined in dogs while they were breathing spontaneously, during controlled ventilation, and during closed circuit anesthesia. Concentrations of compound A were determined by means of gas chromatography with flame ionization.
The concentration of sevoflurane in the anesthetic circuit increased with vaporizer setting and time. For oxygen flow rates of 250 and 500 ml/min, vaporizer settings between 5 and 7 and between 7 and 10, respectively, produced sevoflurane concentrations closest to values reported to produce surgical anesthesia in dogs. Significant differences were not observed in cardiorespiratory variables with time or among anesthetic conditions. Concentrations of compound A in the anesthetic circuit were less than values reported to produce renal toxicoses and death in rats.
Results suggested that sevoflurane can be administered to nonsurgically stimulated dogs, using an in-circuit vaporizer and low (< 15 ml/kg/min) oxygen flow rates, without causing significant cardiorespiratory depression or clinically important concentrations of compound A.
确定使用回路内蒸发器输送七氟醚时麻醉回路中七氟醚和化合物A（七氟醚的一种降解产物）的浓度，并确定七氟醚对犬的心肺影响。
6只杂种犬。
将回路内蒸发器连接到与呼吸机相连的循环再呼吸系统的吸气支路上。在Y形接头处连接一个贮气囊作为人工肺，并在蒸发器设置为1、3、5、7和10以及氧流量为250和500 ml/min时测量麻醉回路中的七氟醚浓度。在犬自主呼吸、控制通气和闭合回路麻醉期间确定七氟醚的心肺影响。通过带有火焰离子化的气相色谱法测定化合物A的浓度。
麻醉回路中七氟醚的浓度随蒸发器设置和时间增加。对于250和500 ml/min的氧流量，蒸发器设置分别在5至7之间和7至10之间时产生的七氟醚浓度最接近据报道可在犬中产生外科麻醉的数值。在心肺变量方面，未观察到随时间或麻醉条件之间的显著差异。麻醉回路中化合物A的浓度低于据报道可在大鼠中产生肾毒性和死亡的数值。
结果表明，使用回路内蒸发器和低（<15 ml/kg/min）氧流量，可将七氟醚用于未接受手术刺激的犬，而不会引起显著的心肺抑制或产生具有临床意义浓度的化合物A。
