The effect of carbon dioxide flow rate on the euthanasia of laboratory mice

• Published in: Laboratory animals (London) 2014-10, Vol.48 (4), p.298-304
• Main Authors: Moody, CM, Chua, B, Weary, DM
• Format: Article
• Language: English
• Subjects: Animals; Carbon Dioxide; Dose-Response Relationship, Drug; Euthanasia, Animal - methods; Female; Mice; Mice, Inbred C57BL; Respiratory Rate
• ISSN: 0023-6772; 1758-1117
• DOI: 10.1177/0023677214546509

Laboratory rodents are commonly euthanized by exposure to gradually increasing concentrations of carbon dioxide (CO2). Current recommended flow rates range between 10 and 30% chamber vol/min and result in insensibility before exposure to painful concentrations (3% aversive. This study aimed to assess the effect of CO2 flow rates on time between the onset of dyspnea and various measures of insensibility (recumbency, loss of the righting reflex and loss of the pedal withdrawal reflex) to identify flow rates that minimize the potential experience of dyspnea. The results of this study indicate that a flow rate of 50% chamber vol/min, while holding the CO2 cage concentration just below 40%, minimizes the interval between the onset of labored breathing and recumbency. Using a 50% flow rate this interval averaged (±SE) 30.3 ± 2.9 s versus 49.7 ± 2.9 s at 20% chamber vol/min (F3,22 = 7.83, P = 0.0013). Similarily, the interval between the onset of labored breathing and loss of the righting reflex averaged 38.2 ± 2.4 s at a flow rate of 50% versus 59.2 ± 2.4 s at 20% chamber vol/min of CO2 (F3,22 = 13.62, P