Hewett T A, Kovacs M S, Artwohl J E, Bennett B T
Biologic Resources Laboratory, University of Illinois at Chicago 60612.
Lab Anim Sci. 1993 Dec;43(6):579-82.
The two methods (prefilled and fixed flow rate filled chambers) recommended in the 1993 AVMA Euthanasia Panel report for using carbon dioxide to euthanatize rats were evaluated in terms of their effect on behavior and selected blood gas values. Responses were videotaped during exposure to > or = 90% carbon dioxide in a prefilled chamber or a gradually filled chamber, using a fixed flow rate of 20% chamber volume/min. Arterial blood samples were taken to determine partial pressure of oxygen, partial pressure of carbon dioxide, pH, and oxygen saturation prior to entering the chamber and at time points determined by rats' responses to carbon dioxide. Rats showed similar reactions when exposed to carbon dioxide by either method. Significant differences in mean time for each response to occur were seen between euthanasia methods. Maintaining a near atmospheric oxygen chamber concentration by using a 75% CO2: 20% O2: 5% N2 gas mixture to gradually fill the chamber did not change rats' reactions upon exposure. Significant differences were found between pre-exposure values and values from samples obtained when rats became immobile after entering the prefilled chamber. Partial pressure of carbon dioxide significantly increased, and pH and percent oxygen saturation significantly decreased from pre-exposure values in all samples obtained after rats entered the gradually filled chamber. Partial pressure of oxygen in these rats was greater than or equal to pre-exposure levels in all samples. Rats appeared sedated because of the anesthetic effects of carbon dioxide when immobility was observed. Distress was not observed in the rats when either method of euthanasia was used.
对1993年美国兽医协会安乐死专家组报告中推荐的两种使用二氧化碳对大鼠实施安乐死的方法（预充式和固定流速填充式气室），就其对行为和选定血气值的影响进行了评估。在预充式气室或逐渐填充式气室中，以20%气室容积/分钟的固定流速使大鼠暴露于≥90%二氧化碳的过程中，对其反应进行录像。在进入气室之前以及根据大鼠对二氧化碳的反应确定的时间点采集动脉血样，以测定氧分压、二氧化碳分压、pH值和氧饱和度。无论采用哪种方法让大鼠暴露于二氧化碳，它们都表现出相似的反应。安乐死方法之间，每种反应发生的平均时间存在显著差异。使用75% CO₂: 20% O₂: 5% N₂气体混合物逐渐填充气室以维持接近大气氧浓度，并未改变大鼠暴露时的反应。在预暴露值与大鼠进入预充式气室后失去活动能力时采集的样本值之间发现了显著差异。在大鼠进入逐渐填充式气室后采集的所有样本中，二氧化碳分压较预暴露值显著升高，pH值和氧饱和度百分比显著降低。这些大鼠所有样本中的氧分压均大于或等于预暴露水平。当观察到大鼠失去活动能力时，由于二氧化碳的麻醉作用，它们显得镇静。使用任何一种安乐死方法时，均未观察到大鼠出现痛苦。
