What is the recommended dosage and administration protocol for a Lasix (furosemide) drip?

Furosemide Drip Dosing and Administration Protocol

For acute heart failure with fluid overload, start with a 20-40 mg IV bolus over 1-2 minutes, followed by continuous infusion at 3-5 mg/hour, doubling hourly until adequate diuresis (>0.5 mL/kg/hour urine output) is achieved, with a maximum rate of 24 mg/hour and total dose limits of <100 mg in 6 hours and <240 mg in 24 hours. 1, 2, 3, 4

Critical Pre-Administration Requirements

Before initiating any furosemide drip, verify the following absolute requirements:

• Systolic blood pressure ≥90-100 mmHg without vasopressor support 1, 2, 3, 4
• Absence of marked hypovolemia (check skin turgor, mucous membranes, orthostatic vitals) 1, 2, 4
• Serum sodium >125 mmol/L (severe hyponatremia is an absolute contraindication) 1, 2
• No anuria or dialysis-dependent renal failure 2, 4
• Not within 12 hours of last vasopressor administration 4

Common pitfall: Starting furosemide in hypotensive patients expecting hemodynamic improvement—this worsens hypoperfusion and precipitates cardiogenic shock. Provide circulatory support (inotropes, vasopressors, or IABP) before or concurrent with diuretics. 1, 2, 4

Initial Dosing Algorithm

Step 1: Determine Starting Bolus Dose

• Diuretic-naive patients or new-onset acute heart failure: 20-40 mg IV bolus 1, 3, 5
• Patients on chronic oral diuretics: Initial IV dose must equal or exceed their home oral dose 1, 3, 4
  • Example: If taking 80 mg oral furosemide daily at home, start with at least 80 mg IV bolus 3, 4
• Acute pulmonary edema: 40 mg IV bolus (higher end of range) 5

Administer the bolus slowly over 1-2 minutes to avoid ototoxicity. 1, 3, 5

Step 2: Initiate Continuous Infusion

Standard preparation: Mix 400 mg furosemide in 500 mL of 5% dextrose (concentration 0.8 mg/mL) after adjusting pH to >5.5 3, 5

Starting infusion rate: 3-5 mg/hour 3, 4, 6

• For 0.8 mg/mL concentration: Set pump at 3.75-6.25 mL/hour 3
• For 1 mg/mL concentration: Set pump at 3-5 mL/hour 3

Maximum infusion rate: 4 mg/min (240 mg/hour) to prevent ototoxicity, though practical maximum is 24 mg/hour 3, 4, 5

Dose Escalation Protocol

Titration strategy: Double the infusion rate every 1 hour until adequate diuresis is achieved 3, 4

Example progression:

• Hour 1: 5 mg/hour
• Hour 2: 10 mg/hour (if urine output <0.5 mL/kg/hour)
• Hour 3: 20 mg/hour (if still inadequate response)
• Maximum: 24 mg/hour 3, 4

Target urine output: >0.5 mL/kg/hour (approximately 35-50 mL/hour for a 70 kg patient) 2, 4

Dose limits:

• First 6 hours: Total furosemide <100 mg 1, 2, 3
• First 24 hours: Total furosemide <240 mg 1, 2, 3

Managing Diuretic Resistance

If inadequate response after reaching 24 mg/hour infusion rate, do not exceed maximum furosemide dose. Instead, add sequential nephron blockade: 1, 2, 3, 4

• Thiazide diuretic: Hydrochlorothiazide 25 mg PO once daily 1, 2, 3
• Aldosterone antagonist: Spironolactone 25-50 mg PO once daily 1, 2, 3

This combination approach is more effective than escalating furosemide alone beyond the ceiling dose. 2, 3

Essential Monitoring Requirements

Immediate Monitoring (Every 15-30 Minutes First 2 Hours)

• Blood pressure (watch for hypotension) 2
• Urine output via Foley catheter (place catheter for accurate measurement) 1, 2, 3, 4

Ongoing Monitoring

• Hourly urine output targeting >0.5 mL/kg/hour 2, 4
• Daily weights targeting 0.5-1.0 kg loss per day 2, 7
• Electrolytes (sodium, potassium) within 6-24 hours, then every 3-7 days 1, 2, 3
• Renal function (creatinine, eGFR) within 24 hours 1, 2, 3
• Signs of hypovolemia: decreased skin turgor, hypotension, tachycardia 2

Safety Thresholds Requiring Immediate Action

Stop furosemide immediately if: 1, 2

• Serum sodium drops <120-125 mmol/L
• Serum potassium <3.0 mmol/L
• Systolic BP drops <90 mmHg
• Creatinine rises >0.3 mg/dL from baseline
• Anuria develops
• Signs of marked hypovolemia appear

Special Considerations and Contraindications

Concurrent Therapy Recommendations

Strongly consider starting IV nitroglycerin alongside furosemide for acute pulmonary edema, as the combination of high-dose nitrates with low-dose furosemide is more effective than high-dose diuretic monotherapy. 2

Avoid concurrent administration with acidic solutions (labetalol, ciprofloxacin, amrinone, milrinone) as they cause furosemide precipitation. 5

Hemodynamic Considerations

Furosemide causes transient hemodynamic worsening (increased heart rate, mean arterial pressure, LV filling pressure, decreased stroke volume) within 1-2 hours of administration. 1 This effect can be prevented with concurrent nitroglycerin. 1, 2

Prognostic Implications

Higher loop diuretic doses are associated with worsening renal function during hospitalization and increased 6-month mortality. 1, 3 This underscores the importance of using the minimum effective dose and adding combination therapy rather than escalating furosemide alone. 1, 2, 3

Alternative Administration: Intermittent Boluses

If continuous infusion is not feasible, intermittent boluses are equally acceptable: 1, 3

• Starting dose: 20-40 mg IV every 2-6 hours 1, 5
• Dose escalation: Increase by 20 mg increments not sooner than 2 hours after previous dose 5
• Maximum single bolus: 80-160 mg IV 5

Administer each bolus slowly over 1-2 minutes. 1, 3, 5

Transition to Oral Therapy

Replace IV therapy with oral furosemide as soon as the patient is clinically stable and able to take oral medications. 5 The oral dose should be approximately 2-2.5 times the effective IV dose due to ~50% oral bioavailability. 8