[The effects of adenosine-induced hypotension on myocardial metabolism]

The effects of hypotension induced by adenosine on myocardial metabolism were studied in ten mongrel dogs anesthetized with 0.5% isoflurane. Adenosine was infused intravenously to reduce mean arterial blood pressure by approximately 30% during a period of 20 min. Although heart rate was unchanged, cardiac output increased and coronary blood flow increased 3-fold of the preinfusion value. Oxygen tension of the myocardium, and oxygen extraction as well as lactate extraction of the myocardium decreased. Myocardial oxygen uptake and myocardial lactate uptake were unchanged, but lactate production was observed in three of ten dogs. In addition, coronary venous lactate/pyruvate ratio and excess lactate increased, and excess lactate became positive in five of ten dogs. The results suggest that adenosine-induced hypotension may inhibit the myocardial aerobic metabolism.