AJP - Heart and Circulatory Physiology, Vol 232, Issue 1 5-11, Copyright © 1977 by American Physiological Society
Effect of autonomic blockade on the hemodynamic findings in acute cardiac tamponade
H. S. Friedman, F. Lajam, Q. Zaman, J. A. Gomes, J. Calderon, N. D. Marino, H. A. Fernando and S. S. Choe
Twenty-three closed-chest, alpha-chloralose-anesthetized, volume-expanded,
alpha- and beta-adrenergic-blockaded dogs with rate fixed by atrial pacing
had 30-90 ml of saline at 37 degrees C infused into the pericardial sac a)
with vagus intact, b) after vagotomy, and c) with vagus intact but with
systolic pressure augmented with a balloon. A significant reduction in left
ventricular (LV) systolic pressure (SP), and cardiac output (CO) occurred
at a pericardial volume of 30-60 ml, when LV end-diastolic (ED) and right
atrial (RA) pressures were not increased. Whereas the percentage decline of
CO, LVSP, maximum negative and maximum positive dP/dt was greater in group
A (vagus intact) than in group B (vagus cut), significant residual
depressed performance was demonstrated only in group B. In four paced,
atropinized, beta-blockaded dogs, response to tamponade was similar to that
in intact dogs; vagotomy at 90 ml in these dogs resulted in a fall in CO, a
rise of LVSP and a significant elevation in LVED and RA pressures. Thus, in
the early phases of cardiac tamponade a sympathetic neurohumoral response
supports cardiac performance while the vagus nerve exerts a myocardial
protective effect. Vagal afferents appear to modulate this response.
