AJP - Heart and Circulatory Physiology, Vol 233, Issue 4 444-H450, Copyright © 1977 by American Physiological Society
Effect of hyperosmotic mannitol on myocardial oxygen consumption
G. J. Vlahakes and W. J. Powell Jr
Hyperosmotic mannitol produces salutary hemodynamic and histologic effects
during experimental myocardial ischemia. However, the administration of
hyperosmotic mannitol is associated with a positive inotropic influence.
Positive inotropic interventions, which increase myocardial oxygen
consumption (MVO2), also tend to increase the extent of ischemic myocardial
injury. Thus, the purpose of this study was to determine the effect of
mannitol on MVO2. Anesthetized dogs on right-heart bypass under conditions
of controlled hemodynamics were studied. Both coronary arteries were
perfused; mannitol was infused via the coronary perfusion cannulas to
produce a 35 mosmol increase in osmolality. Heart rate was maintained
constant. Cardiac output was held constant or deliberately increased so
that left ventricular end-diastolic pressure and tension-time index, two
other hemodynamic correlates of MVO2, remained constant or increased. MVO2
significantly decreased under conditions of decreased myocardial perfusion
(P less than 0.025). This was in spite of a significant increase (P less
than 0.001) in the peak rate of rise of left ventricular pressure (LV
dP/dt), a hemodynamic correlate of MVO2. Thus, hyperosmotic mannitol under
conditions of reduced coronary perfusion increases myocardial efficiency.
