Automatic vs manual injections for thermodilution cardiac output determinations

To investigate the effects of operator variability on thermodilution cardiac output determinations, a group of physicians and nurses made a series of manual indicator injections and automatic injections using a gas powered injector in a simulated clinical situation. The data show significant variability in injection time, injectate flow rate, consistency of injection, and cardiac output values obtained during manual injections. There was little variability in these parameters during automatic injections. When other variables are properly controlled, the automatic injector may improve the precision of cardiac output measurements by controlling the consistency of injection and variables introduced by different operators performing manual injections. However, despite significant variation in parameters associated with manual injection, it is interesting to note that 8 out of 10 operators obtained cardiac output values by hand injection using room temperature injectate, which did not differ significantly from those obtained by automatic injection.