Cardiology

Answer 5 Rapid, repeated intravenous administration of loop diuretics is safe. Large, rapid, intravenous doses of loop diuretics may be effective but incur the risk of ototoxicity and should not be administered repeatedly. Constant intravenous infusion of loop diuretics is effective and prevents resistance from postdiuretic tubular reabsorption of sodium. Several causes contribute to diuretic resistance in CHF, including dietary noncompliance with salt restriction. Nonsteroidal anti-inflammatory drugs cause salt and fluid retention by inhibiting the formation of vasodilator prostaglandins, reducing renal blood flow, and decreasing the glomerular filtration rate. Worsening renal function results in inadequate concentrations of diuretics in the tubular lumen, necessitating intravenous therapy, larger doses of the drugs, or combination therapy with a thiazide. Typically, the thiazide, which has a longer half-life than a loop diuretic, is administered 30 to 60 minutes before the loop diuretic for synergy. SUGGESTED READINGS 1. Consensus recommendations for the management of chronic heart failure. On behalf of the membership of the advisory council to improve outcomes nationwide in heart failure. Am J Cardiol 1999;83:1A-38A. 2. Gomberg-Maitland M, Baran DA, Fuster V. Treatment of congestive heart failure: guidelines for the primary care physician and the heart failure specialist. Arch Intern Med 2001;161:342-52. 3. Heart failure. In: Arky RA, Kettyle WM, Hatem CJ, editors. MKSAP 12: Cardiovascular medicine. Philadelphia: American College of Physicians - American Society of Internal Medicine; 2001:38-49. Click here to return to the questions

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