Validation of the saline-dilution method for measuring cardiac output by simultaneous measurement with a perivascular...

The validity of measurements of right heart output obtained by the saline-indicator method with a catheter-mounted, tetrapolar resistivity sensor placed in the pulmonary artery was assessed. In ten anesthetized dogs, cardiac output was measured simultaneously by the saline-indicator method, using 5 ml of 3 per cent saline as the indicator, and by a perivascular electromagnetic flowprobe placed around the trunk of the pulmonary artery. Cardiac output was altered over a wide range by increasing the depth of halothane anesthesia and by bolus injections of isoproterenol. Linear regression analysis of cardiac output determined from 455 saline-indicator curves and from simultaneous recordings of the electromagnetic flow signal yielded a slope of 0.973, a Y intercept of -0.0047 1/minute, and a correlation coefficient of 0.965. Hence, this method provides accurate and precise measurement of cardiac output. The saline-indicator method with the catheter-mounted resistivity sensor is simple to use and eliminates or minimizes the disadvantages of other indicator-dilution techniques.