What is the recommended dose of Lasix (furosemide) for a continuous infusion?

Furosemide Continuous Infusion Dosing

For continuous infusion of furosemide in acute heart failure, start at 5-10 mg/hour after an initial loading bolus, with a maximum infusion rate of 4 mg/min and total dose limits of <100 mg in the first 6 hours and <240 mg in the first 24 hours. 1, 2, 3

Initial Loading and Infusion Strategy

• Administer a loading dose of 20-40 mg IV push over 1-2 minutes before starting the continuous infusion 2, 3
• For patients already on chronic oral diuretics, use an IV loading dose at least equivalent to their home oral dose 1, 2
• Begin continuous infusion at 5-10 mg/hour (typical starting rate for a 70 kg patient) 1, 2
• The standard preparation is furosemide 400 mg in 500 mL of 5% dextrose, yielding 0.8 mg/mL concentration 2

Critical Administration Requirements

• Never exceed an infusion rate of 4 mg/min to prevent ototoxicity 3
• Adjust the pH of the infusion solution to above 5.5 before adding furosemide, as the drug precipitates at pH values below 7 3
• Do not mix furosemide with acidic solutions (labetalol, ciprofloxacin, amrinone, milrinone) in the same IV line, as precipitation will occur 3
• Administer through a dedicated IV line to avoid drug incompatibility 3

Dose Escalation Protocol

• If inadequate diuresis occurs, increase the infusion rate by increments based on urine output response 1
• Total furosemide dose must remain <100 mg in the first 6 hours 1, 2
• Total furosemide dose must remain <240 mg in the first 24 hours 1, 2
• For severe refractory cases, doses up to 500 mg can be used, but must be given by infusion over 4 hours to prevent ototoxicity 1

Mandatory Monitoring Parameters

• Place a bladder catheter to monitor hourly urine output and assess treatment response 1, 2
• Target urine output of 150-200 mL/hour during active diuresis 4
• Check blood pressure every 15-30 minutes in the first 2 hours 1
• Monitor electrolytes (sodium, potassium) within 6-24 hours after starting infusion 1, 2
• Check renal function (creatinine, estimated glomerular filtration rate) within 24 hours 1, 2
• Monitor daily weights targeting 0.5-1.0 kg loss per day 1

Absolute Contraindications to Infusion

• Systolic blood pressure <90 mmHg without circulatory support 1, 2
• Marked hypovolemia or clinical signs of volume depletion 1, 2
• Severe hyponatremia (serum sodium <120-125 mmol/L) 1
• Anuria or acute kidney injury 1
• Severe hypokalemia (<3 mmol/L) 1

Evidence for Continuous vs. Bolus Administration

Continuous infusion is superior to intermittent boluses for diuretic efficacy in severe heart failure. 5 In a randomized crossover study of 20 patients receiving high-dose furosemide (mean 690 mg/day), continuous infusion produced significantly higher daily urine output (2,860 mL vs 2,260 mL, p=0.0005) and sodium excretion (210 mmol vs 150 mmol, p=0.0045) compared to bolus injection 5. Critically, continuous infusion caused no ototoxicity, while 5 patients experienced reversible hearing loss with bolus administration 5.

Meta-analysis of 12 parallel-group trials (923 patients) confirmed that continuous infusion achieves greater body weight reduction (0.63 kg more, 95% CI 0.23-1.02) without differences in mortality, length of stay, or adverse events 6, 7.

Common Clinical Pitfalls

• Do not use furosemide as monotherapy in acute pulmonary edema—concurrent IV nitroglycerin is superior and should be started immediately 1
• Do not give furosemide to hypotensive patients expecting hemodynamic improvement—it causes further volume depletion and worsens tissue perfusion 1, 2
• Do not administer rapid boluses of high-dose furosemide—this causes ototoxicity that continuous infusion avoids 5
• Acute renal injury develops in 19% of patients, with 70% occurring within the first 48 hours, so early monitoring is essential 4

When to Add Combination Therapy

• If congestion persists after 24-48 hours at maximum infusion rates, add thiazide diuretic (hydrochlorothiazide 25 mg PO) or aldosterone antagonist (spironolactone 25-50 mg PO) rather than further escalating furosemide 1, 2
• Consider adding low-dose dopamine (2.5 μg/kg/min) if adequate diuresis is not achieved despite high-dose furosemide and adequate left ventricular filling pressure 1