How do you administer a Lasix (furosemide) infusion?

How to Administer a Lasix (Furosemide) Infusion

For acute heart failure, start with a 20-40 mg IV bolus given slowly over 1-2 minutes, then either continue with intermittent boluses or switch to continuous infusion at rates not exceeding 4 mg/min, keeping total dose <100 mg in first 6 hours and <240 mg in first 24 hours. 1, 2, 3

Initial Bolus Dosing

• Diuretic-naive patients: Give 20-40 mg IV furosemide as initial dose, administered slowly over 1-2 minutes 1, 2, 3
• Patients already on chronic diuretics: Initial IV dose should be at least equivalent to their oral maintenance dose 2
• If inadequate response: May repeat or increase dose by 20 mg increments, waiting at least 2 hours between doses 3

Continuous Infusion Preparation and Administration

Standard Preparation

• Concentration: Mix furosemide 400 mg in 500 mL of 5% dextrose (yields 0.8 mg/mL) 2
• Alternative concentration: 1 mg/mL can also be used 2
• Critical pH requirement: Ensure pH is adjusted to above 5.5 before adding furosemide, as the drug precipitates at pH <7 3

Infusion Rate Guidelines

• Maximum rate: Never exceed 4 mg/min 3
• Typical starting rate: 5-6 mg/hour (approximately 5-6.25 mL/hr depending on concentration) 2
• Low-dose infusion: Studies show 5.1 mg/hour as mean initial dose is effective and safe 4

Dose Escalation Limits

• First 6 hours: Keep total dose <100 mg 1, 2
• First 24 hours: Keep total dose <240 mg 1, 2

Bolus vs. Continuous Infusion Decision

Either intermittent boluses or continuous infusion are equally acceptable 1, 2. The choice depends on:

• Clinical response to initial bolus
• Need for precise fluid management
• Institutional protocols

Critical Safety Monitoring

Immediate Monitoring Requirements

• Place bladder catheter to accurately monitor urinary output and rapidly assess treatment response 1, 2
• Monitor regularly: Symptoms, urine output, renal function, and electrolytes 1, 5, 2
• Check labs: Within 1-2 weeks after starting or dose changes 5

Contraindications and Cautions

• Do not use if systolic blood pressure <90 mmHg—these patients are unlikely to respond 1, 2
• Avoid in severe hyponatremia, acidosis, or severe hypokalemia (<3 mmol/L) 1, 5

Important Pitfalls and How to Avoid Them

Hemodynamic Worsening

• Furosemide can cause transient hemodynamic deterioration (1-2 hours) with increased heart rate, mean arterial pressure, LV filling pressure, and decreased stroke volume 1, 2
• Prevention strategy: Consider concurrent nitroglycerin administration to prevent this adverse effect 1, 2

Drug Incompatibility

• Never mix with acidic solutions (labetalol, ciprofloxacin, amrinone, milrinone) as furosemide will precipitate 3
• Do not add to running IV lines containing acidic products 3

Diuretic Resistance

• If inadequate response: Consider combination therapy with thiazide-type diuretic (hydrochlorothiazide 25 mg PO) or aldosterone antagonist (spironolactone 25-50 mg PO) 1, 2
• Alternative approach: IV vasodilators may reduce need for high-dose diuretics 1, 2

Prognostic Considerations

• Higher loop diuretic doses are associated with worsening renal function during hospitalization 1, 2
• Worsening renal function correlates with increased 6-month mortality and in-hospital mortality 1, 2
• Low-dose continuous infusion (mean 5.1 mg/hour) was effective in achieving diuresis without detectable effect on renal function in retrospective studies 4

Laboratory Thresholds Requiring Action

• Stop furosemide if severe hypokalemia occurs (<3 mmol/L) 5
• Temporarily withdraw if serum sodium decreases below 120-125 mmol/L 5
• Discontinue if severe hyponatremia (<125 mmol/L), acute kidney injury, or worsening hepatic encephalopathy develops 5