What is the recommended dosing and titration protocol for intravenous furosemide (Lasix) infusion in an adult patient?

Intravenous Furosemide Infusion Dosing for Adults

Initial Bolus and Infusion Start

For acute heart failure with volume overload, administer a 20–40 mg IV bolus over 1–2 minutes, then initiate continuous infusion at 5 mg/hour, doubling the rate hourly until urine output exceeds 0.5 mL/kg/hour, with a maximum infusion rate of 24 mg/hour. 1

Pre-Administration Safety Checklist

Before starting any furosemide infusion, verify:

• Systolic blood pressure ≥90–100 mmHg without vasopressor support 1
• Serum sodium >125 mmol/L (severe hyponatremia is an absolute contraindication) 1
• Absence of anuria (no urine output excludes furosemide use) 2
• No marked hypovolemia on clinical examination 1

Bolus Dose Selection

• Diuretic-naïve patients: Start with 20–40 mg IV bolus 2, 1
• Patients on chronic oral furosemide: Use IV dose at least equivalent to their home oral dose 2, 1
• Severe volume overload with prior diuretic exposure: Consider 40–80 mg initial bolus 2

Administer the bolus slowly over 1–2 minutes to minimize ototoxicity risk 2, 3.

Continuous Infusion Protocol

Standard Preparation and Rates

• Typical concentration: 400 mg furosemide in 500 mL D5W = 0.8 mg/mL 1
• Starting rate: 5 mg/hour (6.25 mL/hour at 0.8 mg/mL concentration) 1
• Escalation: Double the infusion rate every 1 hour until adequate diuresis 1
• Maximum rate: 24 mg/hour (never exceed 4 mg/min to prevent ototoxicity) 1, 3

Dose Limits in First 24 Hours

The European Society of Cardiology sets strict early dosing caps 2, 1:

• First 6 hours: Total dose <100 mg
• First 24 hours: Total dose <240 mg

These limits reflect safety data showing higher early doses correlate with worsening renal function and increased mortality 1.

Monitoring Requirements

Hourly Assessment

• Urine output: Target >0.5 mL/kg/hour; place bladder catheter for accurate measurement 2, 1
• Blood pressure: Check every 15–30 minutes in first 2 hours, then hourly 2

Laboratory Monitoring

• Electrolytes (Na, K) and creatinine: Within 6–24 hours of starting infusion, then every 3–7 days during active titration 2, 1
• Daily weights: Same time each morning, targeting 0.5–1.0 kg loss per day 2

Immediate Stop Criteria

Discontinue furosemide infusion immediately if 2, 1:

• Systolic BP drops <90 mmHg
• Serum sodium falls <120–125 mmol/L
• Serum potassium drops <3.0 mmol/L
• Anuria develops

Managing Inadequate Response

When to Add Combination Therapy

If urine output remains <0.5 mL/kg/hour despite reaching 24 mg/hour infusion rate, add sequential nephron blockade rather than further escalating furosemide. 1

Recommended additions 2, 1:

• Hydrochlorothiazide 25 mg PO once daily, or
• Spironolactone 25–50 mg PO once daily, or
• Metolazone 2.5–5 mg PO once daily

Do not exceed 160 mg total daily furosemide without adding a second diuretic class, as this represents the ceiling effect for loop diuretic monotherapy 2.

Bolus vs. Continuous Infusion: Evidence Comparison

Continuous Infusion Advantages

• More sustained, less variable hourly diuresis compared to intermittent boluses 4
• Avoids rebound sodium reabsorption between bolus doses 2
• May overcome diuretic resistance more effectively through stable tubular drug concentrations 2

Clinical Equivalence Data

A randomized trial of 41 heart failure patients found no significant difference between twice-daily bolus (mean 162 mg/24 hours) and continuous infusion (mean 162 mg/24 hours) in 5:

• Change in creatinine (−0.02 vs. +0.13 mg/dL, p=0.18)
• Total urine output (5,113 vs. 4,894 mL, p=0.78)
• Length of stay (8.8 vs. 9.9 days, p=0.69)

However, a low-dose continuous infusion study (mean 5.1 mg/hour) demonstrated significant increase in mean hourly urine output (150 vs. 116 mL/hour, p<0.001) with only 19% developing acute kidney injury 6.

Special Considerations

Concurrent Vasodilator Therapy

Intravenous nitroglycerin should be started alongside furosemide for acute pulmonary edema, as high-dose nitrates are superior to high-dose furosemide alone and prevent transient hemodynamic worsening from diuretic-induced volume depletion 2, 1.

pH and Compatibility

Furosemide injection has pH ~9 and precipitates at pH <7 3. **Never mix with acidic solutions** (labetalol, ciprofloxacin, amrinone, milrinone) in the same IV line 3. When preparing high-dose infusions, adjust pH to >5.5 before adding furosemide 3.

Geriatric Patients

Older adults have 2–3 times longer furosemide half-life and reduced renal clearance 2. Start at the lower end of dosing ranges (20 mg bolus, 3 mg/hour infusion) and titrate more slowly with frequent blood pressure monitoring 2.

Common Pitfalls to Avoid

• Do not use furosemide in hypotensive patients expecting hemodynamic improvement—it worsens tissue perfusion and can precipitate cardiogenic shock 1
• Do not persist with monotherapy beyond 160 mg/day—add combination diuretics instead of escalating furosemide alone 2, 1
• Do not administer rapid boluses >1–2 minutes—this increases ototoxicity risk, especially at doses ≥250 mg 2
• Do not use furosemide to treat acute kidney injury itself—it is indicated only for managing volume overload that complicates AKI 2