Non-invasive Prediction of Fluid and Noradrenaline Responsiveness Using the Carotid Wave Intensity.

The goal of this observational study is to study a new method to compute ventricular-arterial coupling (VAC) in adult intensive care patients after cardiac surgery. VAC is a metric that describes the interaction between the heart and the arterial system. The new method of measuring VAC uses carotid ultrasound measurements. The main questions this study aims to answer are: * Can VAC measured using carotid ultrasound predict the hemodynamic response to drugs? * What is the concordance of VAC measurements obtained via carotid ultrasound with VAC measurements obtained via the standard, single-beat method? Measurements will be performed in the operating room and at the ICU.