Hemodynamic effects of hypertonic sodium bicarbonate on denervated canine hearts

The hemodynamic consequences of an intravenous bolus of hypertonic sodium bicarbonate were studied in normal dogs and in dogs that had undergone heart autotransplantation. Twenty-one autotransplanted dogs and seventeen sham-operated dogs were instrumented with an electromagnetic flow probe positioned around the ascending aorta. Hemodynamic data were collected three hours after the operation and then at daily intervals for one month, before and during sodium bicarbonate administration. The data indicates that hemodynamic base-line parameters remain lower in autotransplanted dogs than in the control animals during the whole length of the study. At the peak of the hypotensive response that follows the sodium bicarbonate injection the left ventricular performance is decreased to the same extent in both the autotransplanted and the control dogs. This negative inotropic response is enhanced in the presence of myocardial failure. In the autotransplanted group, reflex tachycardia was absent, resulting in a greater reduction in the cardiac index. These two effects explain the greater reduction of arterial pressure in the autotransplanted dogs.