What are the indications for starting furosemide in patients with suspected fluid overload, such as those with heart failure, liver disease, or impaired renal function?

Indications for Starting Furosemide

Furosemide should be initiated in patients with clinical evidence of fluid overload manifesting as edema, ascites, or pulmonary congestion, specifically in the settings of heart failure, cirrhosis with ascites, nephrotic syndrome, or acute pulmonary edema, provided systolic blood pressure is ≥90-100 mmHg and there is no marked hypovolemia, severe hyponatremia (<125 mmol/L), or anuria. 1, 2, 3

FDA-Approved Indications

The FDA label explicitly approves furosemide for:

• Edema associated with congestive heart failure, cirrhosis of the liver, and renal disease including nephrotic syndrome in both adults and pediatric patients 2, 3
• Acute pulmonary edema as adjunctive therapy, with IV administration indicated when rapid onset of diuresis is desired 3
• Hypertension (oral formulation only), though patients inadequately controlled with thiazides will likely not respond to furosemide alone 2

Disease-Specific Initiation Criteria

Heart Failure with Fluid Overload

Start IV furosemide 20-40 mg bolus immediately when patients present with symptoms of congestion and volume overload, particularly pulmonary edema or significant peripheral edema. 1 Critical prerequisites include:

• Systolic blood pressure ≥90-100 mmHg 1
• Absence of marked hypovolemia 1
• No severe hyponatremia or anuria 1

A common pitfall is attempting to use furosemide in hypotensive patients expecting hemodynamic improvement—this worsens tissue perfusion and can precipitate cardiogenic shock. 1 If SBP is <100 mmHg, patients require circulatory support with inotropes, vasopressors, or mechanical support before or concurrent with diuretic therapy. 1

For patients already on chronic oral diuretics, the IV dose should equal or exceed their home oral dose. 1 In acute cardiogenic pulmonary edema, furosemide should not be used as monotherapy—IV nitroglycerin is superior and should be started concurrently, titrated to the highest hemodynamically tolerable dose. 1

Cirrhosis with Ascites

The approach differs fundamentally from heart failure:

For first episode of grade 2 (moderate) ascites, start with spironolactone 100 mg/day alone, increasing stepwise every 72 hours (in 100 mg steps) to maximum 400 mg/day. 4

Add furosemide 40 mg/day only if:

• Body weight reduction is <2 kg/week on spironolactone alone 4
• Hyperkalemia develops on spironolactone 4

For long-standing or recurrent ascites, start combination therapy immediately: spironolactone 100 mg plus furosemide 40 mg as a single morning dose. 4, 1 Increase both drugs sequentially (spironolactone in 100 mg steps, furosemide in 40 mg steps) every 3-5 days if weight loss and natriuresis are inadequate, maintaining the 100:40 ratio. 4, 1 Maximum furosemide dose is 160 mg/day; exceeding this indicates diuretic resistance requiring large volume paracentesis. 4, 1

Critical contraindications before starting diuretics in cirrhosis: 4

• GI hemorrhage
• Renal impairment
• Hepatic encephalopathy
• Hyponatremia
• Electrolyte abnormalities

These must be corrected first. 4

Nephrotic Syndrome

For 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). 1 In congenital nephrotic syndrome, administer IV furosemide 0.5-2 mg/kg at the end of albumin infusions, but only in the absence of marked hypovolemia or hyponatremia. 1

High doses (>6 mg/kg/day) should not be given for periods longer than 1 week. 1 Infusions must be administered over 5-30 minutes to avoid ototoxicity. 1

Acute Respiratory Distress Syndrome (ARDS)

In ARDS patients with fluid overload, administer furosemide when: 1

• Central venous pressure >8 mmHg with urine output <0.5 mL/kg/h, OR
• Central venous pressure >4 mmHg with urine output ≥0.5 mL/kg/h

Absolute Contraindications to Initiation

Do not start furosemide if any of the following are present: 4, 1

• Marked hypovolemia (decreased skin turgor, hypotension, tachycardia)
• Severe hyponatremia (serum sodium <120-125 mmol/L)
• Anuria or acute kidney injury without volume overload
• Systolic blood pressure <90 mmHg without circulatory support
• Persistent overt hepatic encephalopathy (in cirrhosis)

Route Selection

IV administration is indicated when: 3

• Rapid onset of diuresis is required (acute pulmonary edema)
• GI absorption is impaired
• Oral medication is not practical
• Emergency clinical situations

Oral administration is preferred when: 1

• Patient is hemodynamically stable
• In cirrhosis (good bioavailability, avoids acute GFR reduction)
• Chronic maintenance therapy

Parenteral use should be replaced with oral furosemide as soon as practical. 3

Monitoring Requirements After Initiation

During the first weeks of treatment, perform frequent clinical and biochemical monitoring: 4, 1

• Daily weights (target 0.5 kg/day without edema, 1.0 kg/day with edema)
• Electrolytes (sodium, potassium) every 3-7 days initially
• Renal function (creatinine, urine output)
• Blood pressure and signs of hypovolemia
• In acute settings, place bladder catheter to assess response hourly

Stop furosemide immediately if: 4, 1

• Severe hyponatremia develops (sodium <125 mmol/L)
• Severe hypokalemia occurs (<3 mmol/L)
• Acute kidney injury or worsening renal function without adequate diuresis
• Worsening hepatic encephalopathy
• Incapacitating muscle cramps
• Marked hypotension or anuria