A comparison of cardiac output derived from the arterial pressure wave against thermodilution in cardiac surgery patients †

Abstract

In three clinical centres, we compared a new method for measuring cardiac output with conventional thermodilution. The new method computes beat-to-beat cardiac output from radial artery pressure by simulating a three-element model of aortic input impedance, and includes non-linear aortic mechanical properties and a self-adapting systemic vascular resistance. We compared cardiac output by continuous model simulation (MF) with thermodilution cardiac output (TD) in 54 patients (18 female, 36 male) undergoing coronary artery bypass surgery. We made three or four conventional thermodilution estimates spread equally over the ventilatory cycle. In 490 series of measurements, thermodilution cardiac output ranged from 2.1 to 9.3, mean 5.0 litre min(-1). MF differed +0.32 (1.0) litre min(-1) on average with limits of agreement of -1.68 and +2.32 litre min(-1). Differences decreased when the first series of measurements in a patient was used to calibrate the model. In 436 remaining series, the mean difference became -0.13 (0.47) litre min(-1) with limits of agreement of -1.05 and +0.79 litre min(-1). When consecutive measurements were made, the change was greater than 0.5 litre min(-1), on 204 occasions. The direction of change was the same with both methods in 199. The difference between the methods remained near zero during surgery suggesting that a single calibration per patient was adequate. Aortic model simulation with radial artery pressure as input reliably monitors changes in cardiac output in cardiac surgery patients. Before calibration, the model cannot replace thermodilution, but after calibration the model method can quantitatively replace further thermodilution estimates.

Hemodynamics and brain blood flow during posture change in younger women and postmenopausal women compared with age-matched men

“…Cardiac output quantification by Doppler ultrasound has been shown to have good correlation with thermodilution (10,38) and magnetic resonance imaging (65). Jansen et al (26) suggest that the Modelflow estimate of cardiac output should be calibrated to another measurement of cardiac output. Therefore, our measurement of cardiac output using Doppler ultrasound (13) was used to normalize the Modelflow estimated cardiac output from the Finometer.…”

Impaired Cerebral Autoregulation in Patients With Malignant Hypertension

“…When calibrated against a "gold standard" method to determine cardiac output (CO) such as thermodilution or the Fick method, this methodology provides accurate estimates of changes in SV in patients with septic shock 20 and cardiovascular disease 19,21 and during orthostatic stress. 22 The middle cerebral artery blood velocity (MCA V) was measured in the proximal segment of the right MCA (Multidop X4).…”

Cardiothoracic Anesthesia, Respiration and Airway Cardiac output by PulseCO™ is not interchangeable with thermodilution in patients undergoing OPCAB

“…However, the arterial pressure waveform often changes during surgery because the arterial compliance changes according to sympathetic activity, intravascular blood volume, position, etc. [3][4][5] These factors may induce miscalculation of the CO by PulseCO™ because of inaccurate estimation of pulse wave velocity. 2 The purpose of the present study was to determine whether CO measured by the PulseCO™ is interchangeable with CO measured by the bolus thermodilution method with the Vigilance™ monitor (Edwards Lifesciences LLC, Irvine, CA, USA) in patients undergoing OPCAB.…”