When should furosemide (Lasix) be administered?

When to Give Furosemide

Administer furosemide when there is clinical evidence of fluid overload, manifested by peripheral edema, pulmonary congestion, ascites, or elevated central venous pressure, across conditions including heart failure, nephrotic syndrome, cirrhosis, and ARDS. 1

Primary Clinical Indications

Heart Failure with Congestion

• Give IV furosemide 20-40 mg bolus when patients present with symptoms of congestion and volume overload (dyspnea, orthopnea, peripheral edema, pulmonary rales). 1
• Limit total dose to <100 mg in the first 6 hours and <240 mg during the first 24 hours in acute heart failure. 1
• Escalate treatment when oral doses exceed 160 mg/day, as this indicates refractory disease. 1
• Continuous infusion may be considered after initial bolus in patients with persistent volume overload. 1

Nephrotic Syndrome with Severe Edema

• Start furosemide 0.5-2 mg/kg per dose IV or orally up to six times daily (maximum 10 mg/kg per day) when severe edema is present. 1
• Administer IV furosemide 0.5-2 mg/kg at the end of albumin infusions, but only when hypovolemia and hyponatremia are absent. 1
• Do not exceed 6 mg/kg/day for longer than 1 week. 1

Cirrhosis with Ascites

• Begin with oral furosemide 40 mg combined with spironolactone 100 mg as a single morning dose when ascites develops. 1
• Prefer oral over IV administration due to better bioavailability and avoidance of acute GFR reduction. 1
• Increase doses simultaneously every 3-5 days if weight loss and natriuresis are inadequate, up to maximum furosemide 160 mg/day. 1

ARDS with Fluid Overload

• Give furosemide when central venous pressure >8 mmHg with urine output <0.5 mL/kg/h OR when CVP >4 mmHg with urine output ≥0.5 mL/kg/h. 1

Absolute Contraindications to Administration

Stop or avoid furosemide when any of the following are present: 1

• Marked hypovolemia (assess peripheral perfusion, capillary refill)
• Hypotension with systolic blood pressure <90 mmHg
• Severe hyponatremia (typically <120 mEq/L)
• Anuria or complete renal shutdown
• Severe metabolic acidosis

Dosing Strategy by Route

Oral Administration

• Start with 20-80 mg as a single dose for edema in adults. 2
• Increase by 20-40 mg increments no sooner than 6-8 hours after previous dose until desired effect achieved. 2
• May carefully titrate up to 600 mg/day in clinically severe edematous states with close monitoring. 2
• In pediatric patients, start with 2 mg/kg as single dose, increase by 1-2 mg/kg no sooner than 6-8 hours if needed (do not exceed 6 mg/kg). 2

Intravenous Administration

• Use IV route in acute situations requiring rapid diuresis (acute decompensated heart failure, acute pulmonary edema). 1
• Infuse over 5-30 minutes to avoid ototoxicity. 1
• Consider continuous infusion at 20 mg/h, gradually increasing up to 160 mg/h in diuretic-resistant cases. 3

Managing Diuretic Resistance

When inadequate response occurs despite appropriate dosing: 1

• Combine furosemide with thiazides (hydrochlorothiazide 25 mg) for sequential nephron blockade
• Add aldosterone antagonists (spironolactone 25-50 mg) in heart failure
• Use amiloride instead of spironolactone in nephrotic syndrome
• Consider continuous IV infusion rather than bolus dosing 3

Essential Monitoring Parameters

Before each dose, assess: 1

• Peripheral perfusion and blood pressure (avoid if SBP <90 mmHg)
• Volume status (jugular venous pressure, peripheral edema, lung examination)
• Electrolytes, particularly potassium and sodium
• Kidney function (urine output, estimated GFR)
• Acid-base status

During ongoing therapy, monitor for: 1

• Hypokalemia (supplement or add potassium-sparing diuretic)
• Hyponatremia (stop if severe)
• Progressive renal failure (stop if worsening)
• Ototoxicity (more common with rapid IV infusion or very high doses)
• New-onset gout 4

Common Pitfalls to Avoid

• Do not use IV furosemide in cirrhotic patients unless emergent, as oral administration has better bioavailability and avoids acute GFR drops. 1
• Do not infuse rapidly (always give over 5-30 minutes) to prevent hearing loss. 1
• Do not continue high doses (>6 mg/kg/day) beyond 1 week in pediatric patients. 1
• Do not ignore electrolytes—hypokalemia and hyponatremia are the most common complications requiring intervention. 1