Effects of acute reduction of cardiac output on the renal circulation of the dog.

Clinical studies on congestive heart failure have revealed a disproportionately large decrease in renal blood flow as compared to the reduction in cardiac output. Merrill (1) has reported an average diminution of renal blood flow to about onefifth of normal in a large series of decompensated patients whose average cardiac output had decreased to approximately one-half of normal. An average reduction of renal blood flow to about onethird of normal has been described by Mokotoff, Ross, and Leiter (2) in a similar group of patients, but cardiac outputs were not determined. Since these changes occurred in patients who presumably had arterial pressures within or near normal ranges, the question arises whether a reduction of cardiac output per se produces such a marked impairment of the renal circulation. These findings have prompted us to investigate the effects of acutely reduced cardiac output upon the renal blood flow under experimental conditions in which the cardiac output could be rapidly altered. In a previous paper (3), we described the cardiovascular dynamics of acute graded stenosis of the pulmonary artery, and demonstrated that it is possible to achieve significant reduction of cardiac output while maintaining the arterial pressure within normal limits. This was accomplished by compressing the pulmonary artery to a degree where right atrial pressures were significantly elevated while arterial pressures were only slightly reduced or remained essentially unchanged. We suggested that this procedure would be a convenient and relatively simple method for simulating acutely the conditions which are induced chronically in clinical congestive heart failure. This being the case, the procedure would afford an opportunity for assaying the responses of the