Effect of timed semirecumbency and furosemide dosing on urinary sodium excretion in patients with compensated heart failure

PURPOSE: The management of chronic cardiac failure, a salt-sensitive state, frequently includes administration of a loop diuretic to enhance urinary Na excretion. We hypothesized that a period of timed semirecumbency (vis-à-vis upright posture) would enhance the natriuresis that accompanies oral furosemide dosing in patients with compensated cardiac failure. METHODS: Four ambulatory patients with compensated chronic cardiac failure (NYHA Class III) of ischemic and nonischemic origin and systolic dysfunction (ejection fraction <35%), who were receiving a stable regimen of oral furosemide and angiotensin-converting enzyme inhibitor, were enrolled into the study. In the institution's Clinical Research Center, we monitored and compared urine flow rate (mL/min) and Na excretion rate (mEq/hr) in each patient in response to two different protocols. Protocol 1 consisted of an initial 90-minute period of bedrest followed by the patient's oral furosemide dose and 180 minutes of upright activity and a subsequent 90-minute period of bedrest. Protocol 2 was similar, with the exception that furosemide dosing was given after upright activity and immediately prior to the second period of bedrest. RESULTS: With each patient serving as his or her own control, both urine flow rate and urinary Na excretion rate were markedly increased when furosemide was given prior to bedrest as compared to its dosing prior to upright activity. CONCLUSIONS: In patients with compensated chronic cardiac failure, the natriuresis that accompanies oral furosemide dosing is enhanced when given just prior to a period of timed semirecumbency. This approach represents a more optimal use of this loop diuretic in patients with compensated heart failure.