Ok so I'm prepared to take a beating over this question as I am sure this is something I should understand but please bear in mind I am a first year SRNA.
I've had two cases now where in the time span between BP cycles (~ 3 minutes) my ETCO2 falls to 26-28 or so, I make appropriate vent changes to lower minute ventilation, no change, Both times seasoned CRNA says (different ones) "your next BP is gonna be low" and sure enough it is. Now I fully understand that hyperventilation= hypocapnia= vasoconstriction. What I do not understand is the mechanism by which a patient is ditching CO2 under controlled mechanical ventilation ( Not breathing over vent, paralyzed) If that's even whats going on. The best I can come up with is a change in carbonic anyhdrase activity in response to the hypotension? If so what is the mechanism for this response? Both times no significant change in HR. Please be kind........