How to prepare an infusion of Lasix (furosemide)

Furosemide Infusion Preparation and Administration

Preparation of Furosemide Infusion

For continuous infusion, add furosemide to either Sodium Chloride Injection USP, Lactated Ringer's Injection USP, or Dextrose (5%) Injection USP after adjusting the pH to above 5.5, and administer at a controlled rate not exceeding 4 mg/min. 1

Critical pH Requirements

• Furosemide injection is a buffered alkaline solution with a pH of approximately 9 and will precipitate at pH values below 7 1
• The prepared infusion solution must maintain a weakly alkaline to neutral pH range 1
• Never add acid solutions or acidic medications (labetalol, ciprofloxacin, amrinone, milrinone) to the same infusion line, as they will cause precipitation of furosemide 1

Infusion Rate and Dosing

• The maximum infusion rate is 4 mg/min to prevent ototoxicity 1
• For continuous infusions, start at 5-10 mg/hour and titrate based on response 2
• Very high-dose continuous infusions (40-240 mg/hour) have been used safely in refractory cases, though this exceeds standard recommendations 3

Initial Dosing Strategy

Standard Acute Situations

• For edema: Start with 20-40 mg IV push given slowly over 1-2 minutes 1
• For acute pulmonary edema: Start with 40 mg IV push given slowly over 1-2 minutes 1
• If inadequate response after 1 hour in pulmonary edema, increase to 80 mg IV push over 1-2 minutes 1

Dose Escalation Protocol

• If initial dose is insufficient, increase by 20 mg increments no sooner than 2 hours after the previous dose 1
• For patients already on chronic oral furosemide >40 mg daily, start with at least their equivalent oral dose IV 2
• Total dose should not exceed 100 mg in the first 6 hours and 240 mg in the first 24 hours for acute heart failure 2

Continuous Infusion vs. Bolus Dosing

Continuous infusion following a loading dose produces significantly greater diuresis (12-26% increase in urine output) and natriuresis (11-33% increase in sodium excretion) compared to intermittent bolus administration. 4

When to Use Continuous Infusion

• Patients requiring doses ≥120 mg or showing inadequate response to bolus therapy 2
• Severe volume overload with diuretic resistance 5
• Refractory heart failure requiring high-dose therapy 5

Continuous Infusion Protocol

• Give loading dose of 20-40 mg IV push, then immediately start continuous infusion 4
• Start infusion at 20 mg/hour and titrate up to 160 mg/hour based on response 5
• In refractory cases, rates up to 240 mg/hour have been used safely under close monitoring 3

Critical Pre-Administration Assessment

Do not administer furosemide if systolic blood pressure is <90-100 mmHg, or if marked hypovolemia, severe hyponatremia, or anuria is present. 2

• Verify adequate blood pressure (SBP ≥90-100 mmHg) 2
• Exclude severe hyponatremia (serum sodium <120-125 mmol/L) 2
• Confirm absence of anuria or acute kidney injury without volume overload 2
• Check baseline electrolytes (potassium, sodium) and renal function 2

Monitoring Requirements

During Administration

• Monitor blood pressure every 15-30 minutes in the first 2 hours 2
• Place bladder catheter to assess hourly urine output in acute settings 2
• Expect peak diuretic effect within 1-1.5 hours 2

Laboratory Monitoring

• Check electrolytes (sodium, potassium) within 6-24 hours after initiation 2
• Monitor renal function (creatinine) within 24 hours 2
• For continuous infusions, check electrolytes every 3-7 days initially 2

Target Response

• Aim for urine output >0.5 mL/kg/hour 2
• Target weight loss of 0.5-1.0 kg/day (0.5 kg/day without peripheral edema, 1.0 kg/day with edema) 2

Common Pitfalls to Avoid

• Never give furosemide to hypotensive patients expecting hemodynamic improvement—it will worsen tissue perfusion and precipitate shock 2
• Do not administer furosemide concurrently with acidic medications in the same IV line 1
• Avoid infusion rates >4 mg/min due to ototoxicity risk 1
• Do not use furosemide to prevent or treat acute kidney injury itself—only for managing volume overload complicating AKI 2

Special Considerations

Pediatric Dosing

• Initial dose: 1 mg/kg IV given slowly under close supervision 1
• May increase by 1 mg/kg increments no sooner than 2 hours after previous dose 1
• Maximum dose: 6 mg/kg/day (premature infants: maximum 1 mg/kg/day) 1

Geriatric Patients

• Start at the low end of the dosing range (20 mg) 1
• Use cautious dose escalation with careful monitoring 1

Diuretic Resistance

• Consider combination therapy with thiazides (hydrochlorothiazide 25 mg) or aldosterone antagonists (spironolactone 25-50 mg) rather than escalating furosemide alone beyond 160 mg/day 2
• Continuous infusion is more effective than bolus dosing in resistant cases 4, 5