RE: What causes increase in end tidal CO2?

James Colver Cert. Ed, RVN — Tue, 16 Jan 2018 13:55:06 GMT

Assuming there is no inspired CO2 (indicating rebreathing) and you're just asking about increased ETCO2?

In which case, as you have already said the most likely reason is hypoventilation (commonly caused by patient being too deep). Other reasons could include the animal not ventilating properly, for example respiratory depression / lung disease. Less commonly, it could indicate that the animal is in a hypermetabolic state - malignant hyperthermia (in 18 years of observing animals under GA I still have not seen this).

Regarding what to do about it - firstly look at ways to reduce the anaesthetic agent (e.g. asking vet to perform local blocks) and don't be afraid to get the ETCO2 down by manually ventilating the patient - for the entire duration of the procedure if necessary.

If there is also a reading for inspired CO2 as well, (1 - 2 mmHg is acceptable I think) then the patient is rebreathing (examples could include insufficient FGF, exhausted soda lime, faulty valve etc.)

Hope this answers your question. Just to clarify, if the inspired CO2 is at zero and it's only the increased ETCO2 you are worried about - patient is most likely too deep. If not, it could be ventilating inadequately due to effects of GA drugs or disease. Steps to take are to reduce volatile agent where possible and begin ventilating.

RE: What causes increase in end tidal CO2?

jojofruits — Tue, 16 Jan 2018 10:05:56 GMT

too deep, length of anaesthesia, exhausted sodalime...

RE: What causes increase in end tidal CO2?

molladog — Tue, 16 Jan 2018 08:11:49 GMT

Possibly rebreathing C02, too deep ( check depth of anaesthesia ), too low o2 flow rate.....