What is the recommended dosing for a Lasix (furosemide) infusion?

Furosemide Infusion Dosing Guidelines

For patients with acute heart failure requiring a furosemide infusion, the recommended initial dose is 20-40 mg IV bolus followed by a continuous infusion at a rate not exceeding 4 mg/min, with a total dose limit of 100 mg in the first 6 hours and 240 mg during the first 24 hours. 1

Initial Assessment and Bolus Dosing

• For new-onset AHF or patients not on oral diuretics:

  • Initial dose: 20-40 mg IV furosemide bolus 2
  • Administer slowly over 1-2 minutes to avoid ototoxicity

• For patients on chronic diuretic therapy:

  • Initial IV dose should be at least equivalent to their oral dose 2
  • For significant volume overload, consider higher initial doses

Continuous Infusion Protocol

After the initial bolus:

1. Add furosemide to either Sodium Chloride Injection, Lactated Ringer's Injection, or Dextrose (5%) Injection
2. Ensure pH is adjusted to above 5.5 to prevent precipitation 1
3. Administer as a controlled IV infusion at a rate not greater than 4 mg/min 1
4. Total dose should remain < 100 mg in first 6 hours and < 240 mg during first 24 hours 2

Monitoring and Dose Adjustment

• Required monitoring:

  • Urine output (consider bladder catheter for accurate measurement)
  • Renal function and electrolytes (especially potassium)
  • Symptoms of congestion
  • Blood pressure

• Dose adjustment:

  • Titrate according to clinical response, urine output, and patient's symptoms 2
  • If inadequate response after 1 hour, consider increasing the infusion rate

Advantages of Continuous Infusion

Continuous infusion following a loading dose produces significantly greater diuresis and natriuresis than intermittent administration (12-26% increase in urine output and 11-33% increase in sodium excretion) 3.

Combination Therapy for Diuretic Resistance

For patients with diuretic resistance:

• Consider adding a thiazide diuretic (hydrochlorothiazide 25 mg PO) or
• Consider adding an aldosterone antagonist (spironolactone/eplerenone 25-50 mg PO) 2
• These combinations are often more effective with fewer side effects than higher doses of furosemide alone

Important Precautions

• Contraindications/cautions:

  • Hypotension (SBP < 90 mmHg)
  • Severe hyponatremia
  • Acidosis
  • Patients with these conditions are unlikely to respond to diuretic treatment 2

• Compatibility issues:

  • Furosemide is a buffered alkaline solution with pH ~9
  • Do not mix with acidic solutions (e.g., labetalol, ciprofloxacin, amrinone, milrinone) 1
  • Do not add to running IV lines containing acidic products

Potential Adverse Effects

• Electrolyte disturbances (hypokalaemia, hyponatraemia, hyperuricaemia)
• Hypovolemia and dehydration
• Neurohormonal activation
• Increased risk of hypotension when initiating ACEIs/ARBs 2

Special Populations

• Elderly patients: Start at the lower end of the dosing range 1
• Pediatric patients: 1 mg/kg body weight initially, may increase by 1 mg/kg not sooner than 2 hours after previous dose, maximum 6 mg/kg 1
• Premature infants: Maximum dose should not exceed 1 mg/kg/day 1

Remember that parenteral therapy should be replaced with oral therapy as soon as practical, and close medical supervision is necessary when furosemide is given for prolonged periods.