What is the optimal dosing strategy for furosemide (loop diuretic) in patients with acute heart failure, comparing bolus dosing versus continuous infusion?

Furosemide Administration in Acute Heart Failure: Bolus vs Continuous Infusion

Either intermittent bolus or continuous infusion of furosemide is acceptable in acute heart failure, as both strategies produce equivalent clinical outcomes in most patients. 1

Guideline Recommendations

The European Society of Cardiology explicitly states that diuretics can be given either as intermittent boluses or as a continuous infusion, with dose and duration adjusted according to symptoms and clinical status (Class I, Level B recommendation). 1 This represents the highest level of guideline support, indicating both strategies are equally valid first-line approaches.

Initial Dosing Strategy

For patients new to diuretics or not on chronic therapy, start with 20-40 mg IV furosemide as a bolus over 1-2 minutes. 1, 2 For patients already on oral diuretics, the initial IV dose should be at least equivalent to their oral dose. 1

When to Consider Continuous Infusion

Continuous infusion may be considered after the initial bolus dose in patients with significant volume overload or those requiring high doses. 1 The typical infusion rate is 5-10 mg/hour, with a maximum rate not exceeding 4 mg/min during administration. 3, 2

Evidence Comparing Both Strategies

The research evidence reveals important nuances that guidelines don't fully capture:

Efficacy Differences

High-dose furosemide (mean 690 mg/day) administered as continuous infusion produces significantly greater diuresis than bolus dosing - 27% more urine output (2,860 ml vs 2,260 ml, p=0.0005) and 40% more sodium excretion (210 mmol vs 150 mmol, p=0.0045) despite lower urinary furosemide excretion. 4 This suggests continuous infusion achieves more efficient drug delivery to the nephron.

Continuous infusion preceded by a loading dose increases total urine output by 12-26% and sodium excretion by 11-33% compared to intermittent boluses in patients with severe heart failure. 5

Safety Profile

Continuous infusion causes significantly less ototoxicity than bolus dosing. 4 In one study, reversible hearing loss occurred in 5 patients receiving bolus injections but in zero patients receiving continuous infusion, despite equivalent total doses. 4 This occurs because bolus injection produces peak plasma concentrations of 95 μg/ml compared to only 24 μg/ml during infusion (p<0.0001). 4

Patient Selection Matters

Patients on higher outpatient diuretic doses (≥120 mg furosemide equivalent) may paradoxically respond better to bolus dosing than continuous infusion. 6 There was a significant interaction between outpatient dose and mode of therapy (p=0.01) regarding net fluid loss at 72 hours. 6 These patients have more advanced disease, worse renal function, and greater diuretic resistance. 6

Practical Algorithm for Choosing Strategy

Start with Bolus Dosing if:

• Patient is diuretic-naïve or on low outpatient doses (<120 mg/day) 6
• Rapid assessment of diuretic responsiveness is needed 1
• Mild to moderate volume overload 1

Switch to Continuous Infusion if:

• Inadequate response to initial bolus doses within 2-6 hours 1, 3
• Severe volume overload requiring high doses (>160 mg/24 hours) 4, 5
• History of ototoxicity with bolus dosing 4
• Patient on low chronic diuretic doses but presenting with severe decompensation 6

Critical Monitoring Requirements

Regardless of administration method, place a bladder catheter to monitor urinary output and rapidly assess treatment response. 1 Monitor urine output hourly, targeting >0.5 mL/kg/hour. 3

Check electrolytes (particularly potassium and sodium) and renal function within 6-24 hours, then every 3-7 days during active therapy. 1, 3

Monitor blood pressure frequently, as both strategies can cause hypotension. 1 Furosemide should not be administered if systolic blood pressure is <90 mmHg without circulatory support. 1, 3

Dosing Limits and Escalation

Total furosemide dose should remain <100 mg in the first 6 hours and <240 mg during the first 24 hours. 1 If adequate diuresis is not achieved at these doses, add a second diuretic class (thiazide or aldosterone antagonist) rather than further escalating furosemide alone. 1

Common Pitfalls to Avoid

Do not use continuous infusion as first-line therapy in all patients - the DOSE-AHF trial showed no superiority of continuous infusion over bolus dosing for primary clinical endpoints in unselected acute heart failure patients. 6 The choice should be guided by individual patient characteristics, particularly outpatient diuretic dose and severity of volume overload.

Do not assume continuous infusion is always safer - while ototoxicity risk is lower, the overall safety profile regarding renal function and electrolyte disturbances is similar between strategies. 7, 4

Avoid giving furosemide to patients with marked hypovolemia, severe hyponatremia (<120-125 mmol/L), or anuria - these are absolute contraindications regardless of administration method. 1