Title : Different effects of volatile and intravenous anesthetics on left ventricular - arterial
coupling in dogs.
Authors : Y. Deryck, K. Fonck, L. Debaerdemaker, R. Naeije, S. Brimioulle
Laboratory of Physiology, Faculty of Medicine, Free University of Brussels, Belgium
Introduction : General anesthetics do have profound cardiovascular effects, which usually
results in a decreased systemic arterial blood pressure, and an impaired left ventricular –
arterial (VA) coupling. VA coupling refers the interaction between the left ventricle (LV) and
its arterial load in terms of the mechanical energy transfer between these two components.
Criteria for defining optimal VA coupling are maximal mechanical power output and
maximal external mechanical efficiency. The ratio of ventricular end-systolic elastance (Ees)
to effective arterial elastance (Ea) is also an indicator of the coupling between ventricular
contractile properties and arterial load properties. This investigation was undertaken to better
define which factors (cardiac or arterial) are responsible for the deterioration of VA coupling
during sevoflurane anesthesia (a volatile anesthestic) and propofol (an intravenous
anesthetic). Because of their rapid elimination, both drugs could be studied in the same
animals using a cross-over design (random order). Methods :The experiments were
conducted in anesthetized open chest dogs instrumented for measurement of: heart rate,
thermodilution cardiac output, aortic pressure (AoP) and aortic flow, and LV pressure (LVP).
Measurements and signal recordings were performed during anesthesia with 0.5, 1.0 and 1.5
MAC sevoflurane and 12, 24 and 36 mg.kg-1.hr-1 propofol (MAC = minimal alveolar
concentration). The values of Ees and Ea were estimated from the LVP signal by a “single
beat method”. Arterial load was also assessed for its : 1/ steady component : calculation of the
systemic vascular resistance SVR and construction of pressure-flow curves, and 2/ pulsatile
components, aortic compliance and wave reflections, by means of the calculation of the aortic
input impedance spectrum. Results :Both anesthetics decreased AoP, but AoP was always
higher with propofol. Compared to sevoflurane, propofol better maintained VA coupling and
flow. Sevoflurane caused a dose-related impairment of VA coupling (decreased Ees/Ea ratio)
because of a decreased contractile performance (decreased Ees) and increased arterial load
(Ea). Sevoflurane decreased AoP through a reduction in flow, whereas propofol decreased
AoP because of a reduction in arterial tonus. Conclusion : Propofol may be beneficial in
clinical conditions presenting with a VA mismatch, e.g. heart failure.