What is the proper administration protocol for Lasix (furosemide) injection in a patient, considering factors such as age, weight, and impaired renal function?

Furosemide Injection Administration Protocol

Initial Dosing Strategy

For acute fluid overload, administer furosemide 20-40 mg IV push slowly over 1-2 minutes, with the specific dose determined by prior diuretic exposure: use 20 mg for diuretic-naïve patients and 40 mg (or equivalent to home oral dose) for those on chronic diuretics. 1, 2, 3

Route and Rate of Administration

• Intravenous push must be given slowly over 1-2 minutes to prevent ototoxicity 1, 2
• Intramuscular injection is an alternative when IV access is unavailable, though IV is strongly preferred for acute situations requiring rapid diuresis 1, 2
• For high-dose therapy (>80-100 mg), use continuous infusion at rates not exceeding 4 mg/min to avoid hearing loss 1, 2

Critical Pre-Administration Requirements

Before administering furosemide, verify the following absolute requirements:

• Systolic blood pressure ≥90-100 mmHg - furosemide will worsen hypoperfusion and precipitate cardiogenic shock in hypotensive patients 2, 3
• Absence of marked hypovolemia - assess for adequate tissue perfusion, skin turgor, and absence of tachycardia 2, 3
• Absence of severe hyponatremia (serum sodium must be >120-125 mmol/L) 2
• Absence of anuria - verify some urine output exists 2, 3

Dose Escalation Protocol

Reassessment Timing and Dose Adjustment

• If inadequate response after initial dose, wait 1-2 hours before reassessing 1, 2
• For acute pulmonary edema specifically: if no satisfactory response within 1 hour of 40 mg dose, increase to 80 mg IV push over 1-2 minutes 1
• For general edema: increase by 20 mg increments, waiting at least 2 hours between doses until desired diuretic effect achieved 1

Maximum Dosing Limits by Timeframe

• First 6 hours: do not exceed 100 mg total furosemide 2
• First 24 hours: do not exceed 240 mg total furosemide 2
• For acute heart failure, these limits prevent excessive electrolyte shifts while allowing adequate decongestion 2

Continuous Infusion Strategy

When transitioning to continuous infusion after initial bolus:

• Start at 3-5 mg/hour, doubling hourly until adequate diuresis achieved 3, 4
• Maximum infusion rate: 4 mg/min (240 mg/hour) 1, 2
• Prepare infusion by adding furosemide to normal saline, lactated Ringer's, or D5W only after adjusting pH above 5.5 1
• Never mix with acidic solutions (labetalol, ciprofloxacin, amrinone, milrinone) as furosemide will precipitate at pH <7 1

Special Population Adjustments

Pediatric Dosing

• Initial dose: 1 mg/kg IV or IM, given slowly under close supervision 1, 5
• If inadequate response, increase by 1 mg/kg increments, waiting at least 2 hours between doses 1
• Maximum: 6 mg/kg/day - doses exceeding this are not recommended 1, 2
• Premature infants: maximum 1 mg/kg/day 1
• Do not use high doses (>6 mg/kg/day) for longer than 1 week 2

Geriatric Patients

• Start at the low end of dosing range (20 mg) and titrate cautiously 1
• Elderly patients have increased risk of hypotension and electrolyte disturbances 1

Renal Impairment

• Higher doses are required to achieve therapeutic drug levels in renal tubules when GFR is reduced 2
• The initial IV dose for patients with chronic kidney disease should equal or exceed their home oral dose 2, 3
• Monitor closely for ototoxicity at high doses, particularly with rapid administration 2

Cirrhosis with Ascites

• Prefer oral route when possible - IV administration causes acute GFR reduction in cirrhotic patients 2, 3
• When IV necessary: start with 40 mg combined with spironolactone 100 mg 2
• Maximum: 160 mg/day - exceeding this indicates diuretic resistance requiring paracentesis 2, 3

Monitoring Requirements

Immediate Monitoring (First 2 Hours)

• Place Foley catheter for accurate hourly urine output measurement 2, 3
• Target urine output: >0.5 mL/kg/hour 2, 3
• Blood pressure every 15-30 minutes to detect hypotension 2
• Assess for signs of hypovolemia: decreased skin turgor, tachycardia, hypotension 2

Laboratory Monitoring

• Electrolytes (sodium, potassium) within 6-24 hours after initial dose 2
• Renal function (creatinine, BUN) within 24 hours 2
• During first weeks of therapy: check electrolytes every 3-7 days 2

Target Weight Loss

• Without peripheral edema: maximum 0.5 kg/day 2
• With peripheral edema: maximum 1.0 kg/day 2
• Exceeding these targets increases risk of intravascular volume depletion and acute kidney injury 2

Management of Inadequate Response (Diuretic Resistance)

Sequential Nephron Blockade

When reaching high doses without adequate response, add a second diuretic class rather than further escalating furosemide alone:

• Add hydrochlorothiazide 25 mg PO or metolazone 2.5-5 mg PO for thiazide effect 2, 3
• Add spironolactone 25-50 mg PO for aldosterone antagonism 2, 3
• This combination approach is more effective and safer than monotherapy escalation 2, 6

Alternative Strategies

• Consider continuous infusion over bolus dosing - provides more consistent diuresis with lower total dose 4, 6
• In cirrhosis exceeding 160 mg/day: perform large-volume paracentesis rather than further dose escalation 2, 3

Absolute Contraindications Requiring Immediate Cessation

Stop furosemide immediately if any of the following develop:

• Severe hyponatremia (sodium <120-125 mmol/L) 2
• Severe hypokalemia (<3.0 mmol/L) 2
• Progressive renal failure or acute kidney injury (creatinine rise >0.3 mg/dL) 2
• Anuria (complete cessation of urine output) 2, 3
• Marked hypotension (SBP <90 mmHg) without circulatory support 2, 3
• Worsening hepatic encephalopathy in cirrhotic patients 2

Common Pitfalls to Avoid

• Never give furosemide to hypotensive patients expecting hemodynamic improvement - it causes further volume depletion and worsens shock 2, 3
• Never underdose chronic diuretic users - the initial IV dose must equal or exceed their home oral dose to overcome diuretic resistance 3
• Never use furosemide as monotherapy in acute pulmonary edema - concurrent IV nitroglycerin is superior and should be started immediately 2
• Never mix furosemide with acidic IV solutions - drug will precipitate and line must be flushed 1
• Never give high doses as rapid push - infuse doses >80-100 mg over 4 hours to prevent ototoxicity 2, 1

Concurrent Therapy Considerations

Acute Pulmonary Edema

• Start IV nitroglycerin concurrently - more effective than high-dose furosemide alone 2
• Consider non-invasive positive pressure ventilation (CPAP/BiPAP) if respiratory rate >20 and SBP >85 mmHg 2
• Morphine 2.5-5 mg IV may be given for anxiety, dyspnea, or chest pain 2

Circulatory Support

• If SBP <100 mmHg or >30 mmHg below baseline, provide inotropes, vasopressors, or mechanical support before or concurrent with diuretics 2
• Do not delay circulatory support waiting for diuretic response 2, 3