Diuretic Prescribing in Heart Failure

Diuretic prescribing in heart failure relieves congestion and symptoms but does not improve survival, so the aim is euvolaemia on the lowest effective dose. Loop diuretics are the mainstay, and thiazide-like diuretics, acetazolamide and mineralocorticoid antagonists are added when response is poor. Oral absorption of furosemide is variable and falls in gut oedema, so intravenous dosing is used in acute decompensation.

Assessment. Document the dry weight, jugular venous pressure, oedema, orthopnoea, chest findings and natriuretic peptide. Check kidney function and electrolytes before and during treatment.

Response check. After the first intravenous dose, urine output should exceed 100 to 150 mL/hour over the first 6 hours, or spot urine sodium should exceed 50 to 70 mmol/L at 2 hours.

Chronic oral therapy. Furosemide 20 to 40 mg orally once or twice daily if diuretic naive, 40 to 80 mg if eGFR is under 60 mL/min/1.73 m2, titrated to weight loss of 0.5 to 1 kg daily. Equivalent doses: furosemide 40 mg is about bumetanide 1 mg or torasemide 20 mg.

Acute decompensation. Furosemide intravenously at 1 to 2.5 times the daily oral dose as a bolus, or 20 to 40 mg if naive. Repeat every 6 to 12 hours. If response is inadequate at 2 hours, double the dose. Give no faster than 4 mg/min. A continuous infusion of 5 to 10 mg/hour after a bolus is an alternative. Usual daily maximum is 400 to 600 mg furosemide.

Sequential nephron blockade. Add metolazone 2.5 to 5 mg orally once daily, 30 minutes before the loop diuretic, or hydrochlorothiazide 25 to 50 mg once daily, or acetazolamide 500 mg intravenously once daily, for 1 to 3 days with daily electrolyte checks.

Mineralocorticoid antagonist. Spironolactone 25 to 50 mg daily adds diuresis and spares potassium.

Special groups. In pregnancy use loop diuretics only for pulmonary oedema, and avoid thiazides. In older adults start at 20 mg and check for dehydration, falls and urinary retention. In hepatic impairment, use spironolactone with a loop diuretic and avoid rapid fluid shifts. In sulphonamide allergy, cross-reaction with loop diuretics is rare. In gout, loop and thiazide diuretics raise urate.

Monitoring. Daily weight, fluid balance, and sodium, potassium, magnesium and creatinine daily in acute treatment, then at 1 to 2 weeks after any dose change.

Thresholds. Replace potassium if under 4.0 mmol/L. Correct magnesium. Reduce the dose if sodium falls under 125 mmol/L or creatinine rises while the person is euvolaemic. A creatinine rise during effective decongestion is acceptable.

Maintenance. Once euvolaemic, reduce to the least dose that maintains dry weight, and teach a flexible plan with an extra dose for a weight gain of over 2 kg in 3 days.

Switching. Change to torasemide or bumetanide, or give intravenous doses, when oral furosemide fails.

Stopping. Stop or reduce a diuretic for dehydration, hypotension, acute kidney injury or hyponatraemia, and withhold during vomiting and diarrhoea.

Common errors. Under-dosing in kidney impairment, continuing diuretics after euvolaemia is reached, and giving a thiazide-like drug without daily electrolytes.

Referral and escalation. Refer if there is no response to doubled intravenous doses plus a second diuretic, worsening kidney function, hypotension, or resistant congestion.