Leg elevation caused variable changes in stroke volume and stroke work, whereas phenylephrine increased stroke work and dP/dtmax in all patients without changing stroke volume.
Does leg elevation compared to phenylephrine administration differentially affect left ventricular function in coronary surgery patients?
Load-dependent impairment of LV function after leg elevation in coronary surgery patients appears related to deficient length-dependent regulation rather than an impaired contractile response to increased systolic pressures.
BACKGROUND: Load-dependent impairment of left ventricular (LV) function was observed after leg elevation in a subgroup of coronary surgery patients. The present study investigated underlying mechanisms by comparing hemodynamic effects of an increase in LV systolic pressures with leg elevation to effects of a similar increase in systolic pressures with phenylephrine. METHODS: The study was performed in patients undergoing elective coronary surgery prior to cardiopulmonary bypass. High-fidelity LV pressure tracings (n = 25) and conductance LV volume data (n = 10) were obtained consecutively during leg elevation and after phenylephrine administration (5 microg/kg). RESULTS: Leg elevation resulted in a homogeneous increase in end-diastolic volume. The change in stroke volume (SV), stroke work (SW) and dP/dtmax was variable, with an increase in some patients but no change or a decrease in other patients. For a matched increase in systolic pressures, phenylephrine increased SW and dP/dtmax in all patients with no change in SV. Load dependence of relaxation (slope R of the tau-end-systolic pressure relation) was inversely related for changes in SV, SW, and dP/dtmax with leg elevation but not with phenylephrine. CONCLUSIONS: The different effects of leg elevation and phenylephrine suggest that the observed decrease in SV, SW, and dP/dtmax with leg elevation in some patients could not be attributed to an impaired contractile response to increased systolic LV pressures. Instead, load-dependent impairment of LV function after leg elevation appeared related to a deficient length-dependent regulation of myocardial function.
Hert et al. (Sun,) conducted a other in Coronary surgery (n=25). Leg elevation and phenylephrine vs. Within-subject comparison was evaluated on Hemodynamic effects (stroke volume, stroke work, dP/dtmax). Leg elevation caused variable changes in stroke volume and stroke work, whereas phenylephrine increased stroke work and dP/dtmax in all patients without changing stroke volume.