Arterial thermodilution for the measurement of continuous cardiac output and intrathoracic blood volume

The current method for measurement of cardiac output (CO) is by thermodilut ion (TD) and necessitates the insertion of a pulmonary artery catheter (PAC ). CO may also be measured by arterial TD, with the injection done through a CVP line, and the change in temperature sensed in a thermistor that is em bedded in an arterial catheter. The arterial CO, which is less affected by respiratory variations, compares favorably with simultaneous PAC CO and wit h CO measured by the direct Fick method. The thermistor-tipped catheter is usually inserted into the femoral artery, although preliminary results show that arterial CO can also be measured through the axillary artery. The PiCCO system computes CO continuously by an improved arterial pulse con tour analysis. In addition the maximal and minimal stroke volume (SV) Value s are continuously displayed. The SV variability, termed the stroke volume variation (SVV), seems to be a promising hemodynamic parameter in mechanica lly ventilated patients. Although the PiCCO system utilizes just one (cold) indicator, the intrathoracic blood volume (ITBV), which is a measure of pr eload, and the extravascular lung water, can also be measured.