Starting Dose of Lasix (Furosemide) in the Emergency Room
For patients presenting to the ER with acute heart failure and fluid overload, initiate IV furosemide at 20-40 mg as a slow IV push (over 1-2 minutes), with the dose adjusted based on prior diuretic use and renal function. 1
Dosing Algorithm
For Diuretic-Naive or New-Onset Acute Heart Failure
- Start with 20-40 mg IV furosemide given slowly over 1-2 minutes 2, 1
- This lower range (20-40 mg) is appropriate for patients not previously on chronic diuretic therapy 2
- The FDA label specifically recommends this initial dose for edema 1
For Patients on Chronic Diuretic Therapy
- Initial IV dose should be at least equivalent to their home oral dose 2
- If a patient takes 40 mg oral furosemide daily at home, start with at least 40 mg IV 2
- Patients with chronic heart failure and prior diuretic use typically require higher initial doses than diuretic-naive patients 2
For Acute Pulmonary Edema
- Start with 40 mg IV furosemide given slowly over 1-2 minutes 1
- If inadequate response within 1 hour, increase to 80 mg IV slowly over 1-2 minutes 1
- The 2007 ACEP guidelines note that studies used furosemide 1 mg/kg IV (approximately 80 mg for average adult) in acute pulmonary edema trials 2
Critical Considerations
Combination Therapy is Preferred Over Monotherapy
- Level B recommendation: Treat moderate-to-severe pulmonary edema with furosemide in combination with nitrate therapy 2
- Aggressive diuretic monotherapy is unlikely to prevent intubation compared to aggressive nitrate therapy 2
- The Cotter study demonstrated that high-dose nitrates with low-dose furosemide (40 mg) was superior to high-dose furosemide (80 mg every 15 min) with low-dose nitrates 2
Hemodynamic Concerns
- Avoid furosemide in patients with systolic blood pressure <90 mmHg until adequate perfusion is restored 2
- Furosemide transiently worsens hemodynamics for 1-2 hours after administration, increasing systemic vascular resistance and left ventricular filling pressures while decreasing stroke volume 2
- This paradoxical effect supports using vasodilators first in hypertensive acute heart failure 2
Administration Details
- Always give IV furosemide slowly (over 1-2 minutes) to minimize adverse effects 1
- Assess response frequently; consider bladder catheter for accurate urine output monitoring 2
- If initial dose inadequate, may repeat or increase by 20 mg increments at 2-hour intervals 1
Dose Escalation Limits
- Total furosemide dose should remain <100 mg in first 6 hours and <240 mg in first 24 hours 2
- For continuous infusion (if needed after initial bolus), rate should not exceed 4 mg/min 1
Common Pitfalls to Avoid
Diuretic Resistance Recognition
- Patients with hypotension (SBP <90 mmHg), severe hyponatremia, or acidosis are unlikely to respond to diuretics 2
- Consider alternative strategies (vasodilators, ultrafiltration) rather than escalating diuretic doses in these patients 2
Renal Function Monitoring
- Diuretics should be administered judiciously given the association between high-dose diuretics, worsening renal function, and increased long-term mortality 2
- Worsening renal function during hospitalization is associated with increased in-hospital mortality (OR 2.7) 2
- Monitor electrolytes, renal function, and urine output closely 2
Special Populations
- Elderly patients: Start at low end of dosing range (20 mg), as they have increased risk of ototoxicity and nephrotoxicity 1
- Pediatric patients: 1 mg/kg IV is the standard initial dose 1, 3
- Renal insufficiency: Reduce dosing frequency but maintain mg/kg dose to preserve concentration-dependent effect 1