Carbon dioxide (CO2) is often used to euthanize laboratory rodents at the end of a research
study. A growing body of research has shown that CO2 is aversive to mice and rats. Inhalant anaesthetics, like isoflurane, are a humane alternative to CO2 for rendering animals unconscious. This allows for a two-step procedure: rodents are first anaesthetized using isoflurane, then upon insensibility they are killed with CO2. Unfortunately, some lab animal users switch from isoflurane to CO2 too early (before rodents are fully unconscious). New work by UBC researchers shows that users must continue isoflurane exposure for approximately 80 s after the initial sign of unconsciousness in mice (loss of body posture) before switching to CO2. This delay minimizes the chance that mice will consciously experience the unpleasant effects of CO2 exposure.