Tuesday, June 23, 2009

Tuesday June 23, 2009

Q: For cardiac output measurement via thermodilution method, cold (or room temerature) saline should be injected through which port?


Answer: Proximal port

The idea is very simple. Thermodilution method of cardiac output measurement involves injection of a small amount (10ml) of cold saline/dextrose (or room temperature) into the pulmonary artery via proximal port into right ventricle and measuring the temperature (after it is mix with blood) a known distance away while it pass through the same catheter at thermistor near distal port.




The time-temperature curve is made through electronic instrument. The curve is called Q wave. High Q means temperature is changing rapidly (high CO), and low Q means change in temperature is slow (Poor CO). Usually three or four repeated measures are averaged to improve accuracy.

Modern catheters are fitted with a heating filament which intermittently heats and measures the thermodilution curve providing serial Q measurement.



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