Cardiovascular effects of high doses of thiamine (vit B1) in the dog with special reference to myocardial oxygen consumption.

The purpose of this study was to determine the reactions of the cardiovascular system with special reference to myocardial oxygen consumption (MVO2) after the administration of graded doses (up to 2.4 g/kg) of thiamine. The data obtained indicate that thiamine: 1. Decreases mean peripheral pressure up to 25%. 2. Decreases LVEDP, left ventricular pressure, and LV dP/dtmax up to 10%, 15%, and 20% respectively. 3. Reduces pulse rate up to 25%. 4. Reduces coronary sinus blood flow up to 31%. 5. Reduces myocardial oxygen consumption up to 45%. The reduction in LVEDP, LVP, and LV dP/dtmax could be antagonized by dextran or norepinephrine infusion. It is suggested that thiamine blocks alpha-receptors which leads to pooling of blood with a concomitant reduction in pre- and afterload of the heart. The effect on MVO2 suggests that thiamine, the essential coenzyme for the formation of high energy substrates reduced the metabolic needs of the heart. The drug warrants further investigation for the treatment of myocardial ischemia.