Response to rapid infusion or diuresis in acute cardiac infarction.

The effect on the right atrial pressure and oxygen saturation of expansion of the plasma volume by rapid infusion of 500 ml. 5 per cent glucose has been studied in I4 patients with recent uncomplicated cardiac infarction, and in 5 patients with cardiogenic shock. The findings are contrasted with the effect of intravenousfrusemide (40 mg.) in 8 patients with recent cardiac infarction complicated by pulmonary congestion, as judgedfrom the chest radiograph. The right atrial pressure and oxygen saturation are a useful guide to the haemodynamic state of the patient, and can be obtained without undue risk or disturbance. There is a high correlation between the right atrial oxygen saturation and the coronary prognostic index on admission to hospital. Rapid infusion produced a significant increase in right atrial oxygen saturation in the uncomplicated patients; there was no rise in right atrial pressure, and pulmonary congestion was not produced. Three of the 5 patients with shock showed improvement in right atrial oxygen saturation without a rise in right atrial pressure, and 2 recovered. Frusemide produced improvement in both right atrial pressure and oxygen saturation in the patients with pulmonary congestion. The favourable response to a fluid load in some patients suggests that an increase in filling pressure is sometimes needed in cardiac infarction to obtain an optimal ventricular response. A high venous pressure in patients without evidence of pulmonary congestion is not an indication for diuretic treatment.