Validation of a new method to measure cardiac output during extracorporeal detoxification

Cardiac output was measured in 11 patients during extra-corporeal detoxification after open heart surgery. All patients were mechanically ventilated and had pulmonary artery catheters for cardiac output (COT) measured by thermodilution. A sensor on the arterial side of the extracorporeal circulation measured flow and sound velocity transients. Injections of 2-5 ml 0.9% saline at 37 degrees C into the arterial line upstream of the sensor permitted its calibration; 10-20 ml of the same solution was injected intravenously or into the venous dialysis injection port, and cardiac output (COUD) was calculated by the ultrasound velocity dilution technique. COT was measured within 5 min of the ultrasound dilution measurement. CO was in the range of 2-8 L/m. The regression equation was COUD = 1.09 x COT-0.32 (r = 0.97, n = 31). These data suggest agreement between the ultrasound dilution technique and thermodilution. Ultrasound dilution is preferable in patients undergoing extracorporeal detoxification when pulmonary artery catheterization is not required or dangerous.