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Sixty per cent of a control series of the dogs died from a standard toxic dose of digitalis. In a series rendered toxic by a similar dose of digitalis, only 10 per cent died when they were treated with the combination of sodium-potassium citrate salts. A combination of sodium and potassium citrate salts administered intravenously is effective for the treatment of digitalis-induced arrhythmias.

SUMMARY Elective cardiac arrest, accomplished by perfusion of potassium citrate solution into the coronary circulation, has made possible excellent surgical exposure of intra-cardiac structures during open cardiotomy in 80 patients with a wide variety of congenital and acquired lesions. The cardioplegic effect of potassium was reversed by perfusing the coronary arteries with oxygenated blood. In no instance was death or surgical failure attributable to the use of cardiac arrest. Forty-five patients have survived. Reasons for death have been stated within the limits of our present knowledge. The post-operative status of surviving patients has been evaluated on the basis of clinical findings and, when possible, by heart catheterization and cinecardioangiography six to 14 months after operation. Anatomic correction with restoration of normal function may be anticipated in patients with atrial or ventricular septal defects, provided complete absence of the septum is not encountered. Severe pulmonary hypertension is not a contra-indication to closure of septal defects, if there is a large left to right shunt with increased pulmonary flow. In patients with Tetralogy of Fallot, inadequate closure of the ventricular septal defect has been found in most instances when a prosthesis has not been incorporated into the defect. These patients have shown clear-cut evidence of functional improvement, with increased pulmonary blood flow and relief of arterial hypoxemia, but anatomic correction and restoration of normal cardiovascular dynamics has usually not been obtained. Experience with this small group of patients emphasizes the need for further refinements in diagnosis, surgical technique, artificial perfusion and post-operative management before the ultimate potential of open heart surgery may be fully realized.

The isolated Langendorf dog's heart preparation with cross circulation was arranged for studying the effect of anoxia by coronary occlusion and cardiac arrest by drugs, potassium citrate, potassium bicarbonate, and potassium chloride with or without 500mg. of glucose and 10 units of insulin. The heart rate, coronary blood flow, myocardial oxygen consumption and histological changes were studied.(1) The more severe and profuse histological changes, mainly irreversible myocardial degeneration, were produced when potassium citrate was used than those produced by 30 minutes coronary occlusion.(2) The effect of anoxia, i.e., the prominent reactive hyperemia, the sustained increase of the coronary flow and the oxygen consumption and the increase of heart rate observed by the 30 minutes coronary occlusion were definitely restricted by the use of potassium citrate. The concomitant use of the glucose with insulin alleviated the toxic effect of citrate to some extent.(3) The alkalization in order to avoid the metabolic acidosis of the heart muscle occurring during cardiac arrest left a long lasting tachycardia and thus produced an increase of myocardial oxygen consumption for a period of observation.

• A complete, temporary arrest of cardiac motion was induced and an almost bloodless operative field was obtained by the use of potassium citrate in 37 patients undergoing open-heart surgery. The largest group consisted of 18 children with congenital interventricular septal defect. The heart-lung machine, consisting of a pump and an oxygenator, was connected so as to remove blood from the venae cavae, oxygenate it, and return it to the aorta. The aorta was occuluded 2 or 3 cm. above the heart, and a mixture of 2 ml. of 25% potassium citrate solution with 18 ml. of blood was injected into the aorta proximal to the point of occlusion. The potassium citrate solution was injected until the heart stopped. If 20 ml. was not enough, more was injected. It was found that under these conditions the human heart could resume its normal action after periods of arrest as long as 40 minutes. The flaccidity of the heart facilitated extensive repairs, but distortions and tensions that were produced when large defects were closed sometimes resulted in tears elsewhere after the spontaneous beat was restored. The potassium citrate itself did not seem to introduce any new dangers. Of the 13 patients who died, three had transposition of the great vessels and one had a single ventricle. Twenty-four patients recovered. All of the nine patients who had the tetralogy of Fallot were in the group who recovered.