THE EFFECT OF APPLICATION OF TOURNIQUETS TO THE LEGS ON CARDIAC OUTPUT AND RENAL FUNCTION IN NORMAL HUMAN SUBJECTS 12

Abstract

The application of venous tourniquets to the thighs results in a slight but significant fall in cardiac output; highly significant falls in effective renal plasma flow, urine flow and Na excretion, and a fall in glomerular filtration rate of borderline significance toward the end of the tourniquet period. With release of the tourniquets all of the above measured functions return to normal. The renal changes occur at different rates; urine flow slowly, Na excretion more rapidly, and renal plasma flow quite promptly. The decrease in cardiac output is probably due to diminished effective blood volume and the diminished cardiac output in turn leads to a fall in renal plasma flow (and questionably glomerular filtration rate). The inherent errors in the available methods and the lack of methods for performing rapid successive detns. of cardiac output and renal clearances make it impossible to be certain that decrease in renal plasma flow is a result of decreased cardiac output. However, the observed changes in renal function are similar to those in other situations where cardiac output is diminished, i.e., chronic congestive heart failure and shock. The cause of Na retention is not clear but seems to be due to increased tubular reabsorption. The marked antidiuresis which occurs after tourniquets are applied may be due to increased activity of the neurohypophysis, occurring as the result of diminished effective blood volume.