Induction of euthanasia using carbon dioxide in rat: an overview of the available practical guidelines

Background and aims: Euthanasia is used to define ending an animal's life in a way that results in rapid anesthesia and death without pain or distress. One of the most common methods of performing euthanasia in rats is the administration of carbon dioxide (CO2). The aim of this study was to review the available practical guidelines for inducing euthanasia in rats by administrating CO2. Methods: This review study was conducted by searching in international databases, including PubMed, Google Scholar, and Science Direct, using Euthanasia, CO2, and Rats as keywords. Results: Euthanasia of rat using CO2 is a relatively simple, common, rapid, practical and economical method and does not require advanced apparatus or very expert personnel. For doing euthanasia, parameters including the method of CO2 administration, characteristics of CO2 chamber, concentration and flow rate of CO2 administration, duration of euthanasia, euthanasia approval, and disposal of animal carcasses after euthanasia should be considered. Conclusion: According to the overview of the available practical guidelines, a CO2 flow rate of 5.6 L/min is recommended for a standard cage (height, width, and length, 25.4, 22.86, and 48.26 cm, respectively) with a volume of 28 L, which is suitable for two rats. This CO2 flow should be maintained for 2-5 minutes to induce anesthesia and death and should be continued for at least one minute after observing death signs including lack of respiration and faded eye color.