Echo flow versus (non-)invasive haemodynamics 2

Rationale: Diligent fluid management is instrumental to improve postoperative outcome, cost, and quality of care.
Objective: To determine the accuracy of cardiac output estimated by carotid blood flow measurements using ultrasound, compared to thermodilution based cardiac output analysis, and both invasive, and non-invasive pulse-contour analysis.
Study design: Prospective observational diagnostic accuracy study
Study population: 18 adult patients, scheduled for coronary arterial bypass graft surgery and/or mono valve surgery.
Intervention: Functional hemodynamic test; end-expiratory occlusion test, inspiratory hold, passive leg raise test.
Main study parameters/endpoints: Cardiac output based on ultrasound measurements of carotid blood flow and its variations. The accuracy of these hemodynamic estimates is compared to thermodilution derived cardiac output, along with pulse-contour analysis derived cardiac output (invasive or non-invasive) after functional hemodynamic tests to induce changes in preload or systemic vascular resistance.
We will also measure continuous invasive arterial blood pressure (systolic, diastolic, and mean arterial pressure), stroke volume variation, central venous pressure, heart rate, electrocardiogram, peripheral flow index, peripheral oxygen saturation, end-tidal carbon dioxide, respiratory waveform and respiratory rate.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Patients participating in the study will be exposed to minimal burden as only non-invasive ultrasound measurements will be performed additional to standard of care. Only 3 measurements will be performed with the patient awake; all other additional ultrasound measurements will be performed under anaesthesia. In cardiac surgery patients, central venous cannulation and continuous intra-arterial blood pressure monitoring by cannulation of the radial, brachial or femoral artery is standard of care. In this study, we standardly perform femoral artery cannulation for transpulmonary thermodilution. Compared to radial or brachial artery cannulation, there are no additional risks.

We aim to compare the accuracy of ultrasound derived blood flow parameters from the carotid artery to pulse-contour derived cardiac output and non-invasive cardiac output measurements. Our motivation is to develop a non-invasive, radiation-free, ultrasound flow measurement method to monitor hemodynamic parameters relevant for ICU patient’s status.

First 4 hours postoperative, 8 hours postoperative, one day postoperative

We will perform non-invasive ultrasound measurements of the carotid blood flow in ICU patients, before and after events that are expected to change preload or SVR, that may also result in change of cardiac output. We will collect simultaneously data from blood flow measurements and invasive and non-invasive pressure waveforms together with pulse-contour data. The events involve functional hemodynamic tests, passive leg raise tests, positional changes, administration of fluids, and discontinuation of sedation or vasopressors.