Clinical evaluation of the HemoSonic monitor in cardiac surgical patients in the ICU

The HemoSonic monitor (HemoSonic 100, Arrow International, Reading, PA, U.S.A.) is a minimally invasive device to determine cardiac output by means of M-mode and pulsed Doppler ultrasound. We evaluated the HemoSonic monitor by comparing its output to paired measurements obtained by the standard thermodilution technique in patients who had recently undergone cardiac surgery. Forty-seven paired measurements were carried out in 13 patients. The correlation between the two methods was very good with a correlation coefficient of 0.81. Comparison of the two techniques using the method described by Bland and Altman showed a mean of the differences of -0.23. The limits of agreement were -2.35 to 1.89. There was a reduced correlation between techniques at higher values of cardiac output. We concluded that the HemoSonic monitor has a place in intensive care monitoring, with good correlation with cardiac output measured by the thermodilution technique. It appears to be less suitable for use in patients with a high cardiac output state. The oesophageal probe is moderately difficult for patients to tolerate and is only appropriate for use in sedated patients. The accuracy of the device is somewhat operator-dependent.