Expert: Dr Ian Jackson - please note UK based - 3/23/2011

Question
Hello, suppose one has a total hip replacement surgery that takes about 3 hours and the anesthetic technique is ETT with a cuff.  For a 90 kilogram 81 year old with DVT, is there a minimum oxygen / N2O flow rate recommended for those 3 hours?  Thank you for your time.

Answer
This sounds a bit like homework?
If you are working with a 'closed system' with CO2 absorber which you are implying by saying you are using a cuffed ETT then you can move down to minimal basal requirement gas flows. With modern monitoring of the inspired O2 this would be around 250ml/min of O2 added to the circuit and similar volumes of N2O. In reality few anaesthetist go below flows of 1 litre/min overall as they feel anxious despite modern monitoring.
Hope this helps
Dr Ian Jackson