Loop diuretics can cause clinical natriuretic failure: a prescription for volume expansion.

Ultrafiltration enhances volume removal and weight reduction vs diuretics. However, their differential impact on total body sodium, potassium, and magnesium has not been described. Fifteen patients with congestion despite diuretic therapy had urine electrolytes measured after a diuretic dose. Ultrafiltration was initiated and ultrafiltrate electrolytes were measured. The urine sodium after diuretics (60+/-47 mmol/L) was less than in the ultrafiltrate (134+/-8.0 mmol/L) (P=.000025). The urine potassium level after diuretics (41+/-23 mmol/L) was greater than in the ultrafiltrate (3.7+/-0.6 mmol/L) (P=.000017). The urine magnesium level after diuretics (5.2+/-3.1 mg/dL) was greater than in the ultrafiltrate (2.9+/-0.7 mg/dL) (P=.017). In acute decompensated heart failure patients with congestion despite diuretic therapy, diuretics are poor natriuretics and cause significant potassium and magnesium loss. Ultrafiltration extracts more sodium while sparing potassium and magnesium. The sustained clinical benefits of ultrafiltration compared with diuretics may be partly related to their disparate effects on total body sodium, potassium, and magnesium, in addition to their differential efficacy of volume removal.