Treatment of Volume Overload
The loop diuretic furosemide is the most frequently prescribed diuretic for treatment of volume overload in HF. Initial oral doses of 20 to 40 mg once a day should be administered to patients with dyspnea on exertion and signs of volume overload who do not have indications for acute hospitalization. Severe overload and pulmonary edema are indications for hospitalization and intravenous furosemide.
Some patients with mild HF can be treated effectively with thiazide diuretics. Those who have persistent volume overload on a thiazide diuretic should be switched to an oral loop diuretic. Oral absorption of furosemide is diminished by physiologic changes in HF, particularly if the oral dose is taken on a full stomach. HF patients with poor oral absorption, renal insufficiency, or both may require much higher doses of a loop diuretic to reach a threshold level for diuresis. All patients who require diuretic treatment should be questioned about the use of NSAIDs and dietary sodium, as both may influence fluid retention and the diuretic dose needed.
Important adverse effects of diuretics that require periodic monitoring include orthostatic hypotension, prerenal azotemia, hyponatremia, hypomagnesemia, and hypokalemia. Most patients taking 40 mg or more of furosemide daily should supplement their oral potassium intake through dietary changes, prescribed potassium supplements, or both. The addition of an ACE inhibitor or spironolactove to the treatment regimen may also increase serum potassium levels.
Adding a second diuretic is sometimes necessary to achieve optimal fluid balance in patients with persistent water and sodium retention. Adding metolazone, 2.5 to 10 mg per day, to a daily furosemide dose can significantly increase diuresis for outpatient treatment of moderate volume overload. Such therapy is best used only for brief periods owing to the increased risk of electrolyte depletion, promoting prerenal azotemia, or lowering blood pressure to levels that make it difficult to add other disease progression modifying agents. Spironolactone can be added to standard regimens to increase diuresis and improves survival for patients with moderate to severe systolic dysfunction HF.
Once volume overload is corrected and an ACE inhibitor is initiated, the diuretic dose often can be carefully decreased. Some patients may only need intermittent diuretic therapy when symptoms and increases in daily weights signal a return of excess fluid volume.
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