Clinical Assessment of Arterial Dynamic Elastance in ICU Patients, Dependent on Inotropic or Vasopressor Drugs.

Assessment of the cardiovascular status and haemodynamics comprise directly or indirectly cardiac output, which is determined by left ventricular preload, contractility, afterload and heart rate. Various haemodynamic monitors have been introduced in anaesthesia and ICU practice, providing cardiac output either non-invasively or invasively. The combined use of arterial pressure monitoring with these devices provides insight not only in cardiac output but offers bedside assessment of most determinants of cardiovascular function. Both pulse pressure variation (PPV) and stroke volume variation (SVV) have been described as dynamic descriptors of fluid responsiveness, a measure allowing optimization of preloading conditions if haemodynamics show signals of insufficient perfusion.

Arterial load can be assessed based on a two-element Windkessel model with a static and dynamic component. The static part consists of a resistive element (systemic vascular resistance: SVR = (MAP/C0)*80, with MAP, mean arterial pressure; CO, cardiac output) and a pulsatile component (net arterial compliance C = SV/arterial pulse pressure with SV, stroke volume). Arterial elastance is considered being an integrative variable, associating both steady elements and heart rate (Ea = .9*SAP/SV with EA, arterial elastance; SAP, systolic arterial pressure). The dynamic component Eadyn is the ratio of PPV and SVV during a mechanical ventilator cycle, providing a functional assessment of ventriculo-arterial coupling.

Combined use of arterial pressure tracing (or its non-invasive surrogate) and (non-) invasive stroke volume actually may provide an interesting framework for haemodynamic monitoring and subsequent optimization in many surgical, postoperative or ICU patients. This study aims to copy as good as possible the handling and the way of management as in a clinical setting.