[HSF] AV fistulas- CPB flows

[prasannasimha]

If they are Brescio Cimino fistulae  the shunt flow is not 
"hemodynamically really significant". The problem can be significant if 
it is a shunt to the brachial artery.
You could place a femoral venous cannula but remember that the venous 
cannula if placed at the level of the renals or hepatic veins can give a 
falsely high venous sat too.
Monitoring Lactate would probably be a better option. The better option 
as far as monitoring venous oximetry is to perfuse at MVO2 max by 
measuring the O2 content of the arterial (arterial line) and venous 
side(from the venous reservoir) and  calculating the O2 consumption and 
determining (titrating) increasing flows till maximal oxygen consumption 
is reached. This can easily be done and is a standard exercise I give 
for my final year perfusion students. It takes 5 -10 minutes and a few 
ABG's (and is still easier if you have an inline oximeter to determine 
when to sample). MVO2 max (I cannot get the dot on the acronymn so it is 
looking like  mixed venous Sat - sorry for the error) should remain 
above 3.5 ml /Kg / min when Normothermic and fully anesthetized.
Prasanna
sekhar le wrote:
>
> We occasionally have patients with upper limb  AV fistulas for CRF 
> coming for surgery. Sometimes the Fistulas appear to be aneurysmal 
> and   having high flows.
> We have been managing by empirically increasing CPB flows by 20%.
> Should we have a venous catheter in the femoral vein to be able to 
> check venous saturation in the lower segment of the body   to make 
> sure that adequate flows are delivered to lower segment of the body?
>
> Dr Sekhar
>
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