Upon initiation of bypass, the perfusionist became aware of an oxygenation issue; arterial blood was dark and desaturated. Team informed, lungs switched on, came off bypass and called for help. Hardware sweep yielded no discrepancies, and air was flowing as expected - the vaporiser was set to 0% as CPB had been terminated. When turning the isoflurane to 1% it was discovered that air flow was blocked post vaporiser. Decision was made to replace the vaporiser and re-test of bypass. Air flow was now restored at 1% iso.

‍

Bypass was initiated for the second time. There was adequate oxygen delivery, although settings were higher than expected - this was attributed to oxygen debt. Sweep and FiO2 settings came down throughout the case, consistent with this theory, although settings were still higher than usual.

‍

Approximately an hour into the second bypass run, there was a sudden decrease in pO2 and sharp increase in pCO2 observed through CDI inline monitoring - in the space of 20 seconds. Help called again, max settings set on sweep and FiO2 and rise in pCO2, oxy recirculation line opened. This attenuated the fall in pO2 and rise in pCO2, but numbers were not recovering to pre-event levels. Decision made by 3 perfusionists to bypass the vaporiser using 1/4" connector to connect the pre and post vaporiser gas lines together. Anaesthetist started propofol infusion.

‍

Numbers restored to safe and expected levels. CPB continued without further issues.