What is the appropriate initial dose and frequency of Lasix (furosemide) for an inpatient with congestive heart failure (CHF) and fluid overload?

Inpatient IV Furosemide Dosing for CHF

For a hospitalized CHF patient with fluid overload, the initial IV furosemide dose must equal or exceed their total daily oral dose—not 20 mg every 4 hours, which is inadequate for patients already on chronic diuretics. 1

Initial Dosing Algorithm

For Patients Already on Oral Diuretics

• Start with IV furosemide at a dose ≥ their total daily oral dose (e.g., if taking 40 mg PO twice daily = 80 mg total, give at least 80 mg IV initially) 1, 2
• Administer as a slow IV push over 1-2 minutes or divide into boluses every 2 hours 1, 3
• Starting with 20 mg IV every 4 hours (80 mg/day) is only appropriate if the patient's home oral dose was ≤80 mg/day total 1

For Diuretic-Naïve Patients

• Initial dose: 20-40 mg IV furosemide as a single slow push 1, 2, 3

Dose Escalation Protocol

If inadequate diuresis occurs after the initial dose:

• Increase by 20 mg increments every 2 hours until desired diuretic effect is achieved 2
• Maximum recommended doses: <100 mg in first 6 hours, <240 mg in first 24 hours 1, 2
• Consider switching from intermittent boluses to continuous infusion at ≤4 mg/min for persistent volume overload 3, 4

For diuretic resistance despite dose escalation:

• Add a second diuretic (thiazide such as metolazone 2.5-10 mg daily, or spironolactone 25-50 mg) 1, 5
• Low-dose combinations are more effective with fewer side effects than high-dose monotherapy 1, 2

Critical Monitoring Requirements

Hourly initially:

• Urine output (bladder catheter placement is usually desirable) 1, 2
• Blood pressure and respiratory status 2

Daily during active IV diuresis:

• Weight at same time each day (target 0.5-1.0 kg daily loss) 2, 5
• Electrolytes (especially potassium), BUN, and creatinine 1, 2
• Fluid intake/output 5

Essential Concurrent Management

Continue guideline-directed medical therapy:

• Do NOT stop ACE inhibitors/ARBs or beta-blockers unless patient is hemodynamically unstable (SBP <90 mmHg with end-organ hypoperfusion) 1, 2, 5
• These medications work synergistically with diuretics and blunt deleterious neurohormonal activation 2, 5

Supplemental therapies:

• Oxygen if SpO₂ <90-94% 2
• Consider non-invasive ventilation for respiratory distress with pulmonary edema 2
• IV vasodilators (nitroglycerin, nitroprusside) may be considered if SBP >110 mmHg without symptomatic hypotension 1, 2

Common Pitfalls to Avoid

Starting with doses lower than home oral dose is inadequate:

• A patient on 40 mg PO BID (80 mg/day total) requires at least 80 mg IV initially, not 20 mg 1, 2
• 20 mg IV every 4 hours may be appropriate ONLY if this equals or exceeds their home dose 1

Excessive concern about hypotension and azotemia:

• Can lead to underutilization of diuretics and refractory edema 2
• Small-to-moderate BUN/creatinine elevations should not prompt therapy reduction if renal function stabilizes 5
• If hypotension or azotemia occurs before treatment goals are achieved, slow the rate of diuresis but maintain it until fluid retention is eliminated 2

Stopping ACE inhibitors/ARBs or beta-blockers prematurely:

• Continue unless true hypoperfusion exists (SBP <90 mmHg with cool extremities, altered mental status, oliguria, elevated lactate) 2, 5
• Inappropriate discontinuation undermines the efficacy of heart failure therapy 2

Inadequate monitoring:

• Electrolyte depletion (especially hypokalemia with combination diuretics) can precipitate life-threatening arrhythmias 1, 5
• Treat electrolyte imbalances aggressively while continuing diuresis 2

Special Considerations for Renal Impairment

For patients with reduced renal function (e.g., CrCl 44 mL/min):

• Higher doses are often necessary to achieve adequate diuresis 2
• May require escalation up to 600 mg/day in severe cases before adding sequential nephron blockade 5
• Monitor renal function closely but do not prematurely reduce diuretic dose for modest creatinine elevations 5

1, 2, 5, 3