RE: Anaesthesia questions - CO2 and blood pressures

V E S — Mon, 28 Aug 2017 10:08:08 GMT

Thank you so much!! This was very helpful and I'll take a look at those fluid therapy guidelines :)

RE: Anaesthesia questions - CO2 and blood pressures

Susanna Taylor — Mon, 28 Aug 2017 05:04:04 GMT

Hi Victoria, These are pretty common questions and definitely worth researching!

Hypercapnia is nearly always a respiratory caused problem, that is, the patient not removing carbon dioxide adequately. (very very rarely a metabolic problem of over production). It is not directly related to receiving low oxygen levels, but hypoxia can be a concern; turning up oxygen is not going to help, but if the patient is not breathing adequately to remove CO2 it may not be breathing adequately to gain enough oxygen (even at 100% O2).

Common reasons for hypoventilation will be; too deeply anaesthetised, respiratory depression caused by drugs (like high dose opioids), or positional/equipment reasons making respiration hard (fat dog on back, sternal recumbency in barrel dogs, kinks in ET tube, position of ET tube trachea, sticky valves on circle system). Some of these things can also present as fast low ETCO2 breaths, but high ETCO2 when given IPPV.

SO treatment for hypercapnia can be as simple as lightening the GA, repositioning the patient or equipment, or you need to initiate IPPV short term or continuously depending on the cause. Only values over 60mmHg really need IPPV though, as this is when acidaemia or intercranial changes start

Hypotension is most commonly caused by vasodilation under anaesthesia (ACP, Prop, Iso etc all are dose dependant vasodilators). hypovolamea, hypothermia and cardiac issues are also possible causes. Treatment basically should be advancing through: lower anaesthetic depth, crystalloid bolus, colloid bolus, inotropic drugs. The best resource is the AAHA fluid therapy guidelines, which are open access, so i suggest you have a look at these for details! also regarding surgical rate fluids! (much lower than 10ml/kg/hr)

Thanks for asking the questions, and feel free to ask anything else if it doesn't make sense.

Im sure some others will chip in too