Inadvertent severe hypercarbia associated with anesthesia machine malfunction in one cat and two dogs

Severe acute hypercarbia occurred in a cat and 2 dogs as a result of anesthesia machine malfunction. In each case, the anesthesia machine had been checked by the anesthesia technician and clinician, and no problems were found. After it was noticed that the same machine had been used on each animal, further investigation revealed an expiration valve that was functional with large breaths or positive pressure ventilation but was not functional with small breaths with low peak inspiratory flow. Rebreathing of expired carbon dioxide occurred, and the patients subsequently became severely hypercarbic. Recovery from anesthesia was prolonged in 2 animals, and cardiac and respiratory arrest occurred in the third. Hypercarbia from rebreathing can be detected through the use of blood gas analysis or end-tidal carbon monoxide monitoring.