Why the study?
Does systemic alpha adrenergic blockade alter myocardial oxygen supply and demand during moderate cardiac tamponade in anesthetized dogs?
Does systemic alpha adrenergic blockade alter myocardial oxygen supply and demand during moderate cardiac tamponade in anesthetized dogs?
Peripheral vasoconstriction attenuates the fall in aortic pressure during cardiac tamponade, but adequate myocardial oxygen supply depends on local metabolic vasodilatory systems rather than reflex adjustment.
Alpha blockade worsens hypotension in canine tamponade without impairing myocardial oxygenation; leaves open whether local metabolic control predominates in humans.
SummaryThe influence of reflex vasoconstriction on aortic pressure and myocardial oxygen supply and demand during moderate cardiac tamponade was examined in anesthetized, open-chest dogs by comparing responses before and after systemic alpha adrenergic blockade. After α blockade, aortic pressure fell more during cardiac tamponade but there was no change in the ability of myocardium to satisfy its oxygen demand. The data suggest that although peripheral vasoconstriction attenuates the fall in aortic pressure during cardiac tamponade, adequate oxygen supply to myocardium depends on local metabolic vasodilatory systems that couple metabolism to coronary vascular tone, and not on this reflex adjustment.
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Crystal et al. (1979) studied this question.
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