Comparison of bedside measurement of cardiac output with the thermodilution method and the Fick method in mechanically ventilated patients

Abstract

Introduction Bedside cardiac output determination is a common preoccupation in the critically ill. All available methods have drawbacks. We wished to re-examine the agreement between cardiac output determined using the thermodilution method (QTTHERM) and cardiac output determined using the metabolic (Fick) method (QTFICK) in patients with extremely severe states, all the more so in the context of changing practices in the management of patients. Indeed, the interchangeability of the methods is a clinically relevant question; for instance, in view of the debate about the risk-benefit balance of right heart catheterization. Patients and methods Eighteen mechanically ventilated passive patients with a right heart catheter in place were studied (six women, 12 men; age, 39-84 years; simplified acute physiology score II, 39-111). QTTHERM was obtained using a standard procedure. QTFICK was measured from oxygen consumption, carbon dioxide production, and arterial and mixed venous oxygen contents. Forty-nine steady-state pairs of measurements were performed. The data were normalized for repeated measurements, and were tested for correlation and agreement. Results The QTFICK value was 5.2 ± 2.0 l/min whereas that of QTTHERM was 5.8 ± 1.9 l/min (R = 0.840, P < 0.0001; mean difference, -0.7 l/min; lower limit of agreement, -2.8 l/min; upper limit of agreement, 1.5 l/min). The agreement was excellent between the two techniques at QTTHERM values < 5 l/min but became too loose for clinical interchangeability above this value. Tricuspid regurgitation did not influence the results.

Impedance cardiography (electrical velocimetry) and transthoracic echocardiography for non-invasive cardiac output monitoring in pediatric intensive care patients: a prospective single-center observational study

“…In vigorously breathing neonates, the variation was as high as 40% (as indicated by the Aesculon® monitor). The variation in stroke volume during the respiratory cycle is a problem for any method of determining CO [26,30,36,37]. Theoretically, variation in stroke volume should equally affect EV and TTE.…”

Physical Model of the Pulmonary Circulation Designed for Investigation on Cardiac Output Measurement by Means of the Thermodilution Method

“…Many authors compare the results of CO measurements obtained by means of the thermodilution and the Fick methods [6][7][8][9][10][11][12][13][14] but in fact, the accuracies of the others methods are unknown. Therefore only the correlation of results may be estimated.…”

Ultrasound dilution

“…PAC thermodilution method could be considered the current clinical standard and is commonly used to validate new CO measurement methods [4, 19–20, 24]. We chose the pediatric post heart transplant patient population undergoing hemodynamic evaluation in our catheterization laboratory primarily because all these patients have a PAC catheter and a central venous and arterial catheter placed irrespective of this study.…”