Hypotension and myocardial metabolism

This study investigated the effect of hypotension produced by nitroprusside or halothane on haemodynamics and myocardial metabolism. It is postulated that halothane might influence the balance of supply and demand of oxygen to the heart more favourably than nitroprusside. The results in six open-chested dogs do not support this view. Despite the fact that the two drugs lowered the mean arterial pressure by radically different mechanisms, the reduction in demand for oxygen by the heart seemed to be matched by a similar reduction in supply with both drugs. No evidence of anaerobic metabolism or increased a-v O₂ content differences was found. It is concluded that the reduction in mean arterial pressure to these levels by either method is not likely to impair myocardial energetics in healthy hearts with normal coronary anatomy.