What is considered a satisfactory urine output after administration of IV Lasix (furosemide) in the first 1-2 hours?

Satisfactory Urine Output After IV Furosemide

A satisfactory urine output response to IV furosemide in the first 1-2 hours is at least 100-150 mL/hour, with a spot urine sodium concentration ≥50-70 mEq/L at 2 hours indicating adequate diuretic response. 1

Expected Urinary Response Thresholds

First 2 Hours Post-Administration

• Urine output <100-150 mL/hour during the first 6 hours denotes an insufficient diuretic response and should prompt rapid uptitration of the diuretic dose 1
• A spot urine sodium concentration <50-70 mEq/L at 2 hours after loop diuretic administration similarly indicates inadequate response 1
• These early markers allow for rapid decision-making to optimize natriuresis rather than waiting for delayed clinical endpoints 1

Minimum Acceptable Output

• Urine output should be maintained at ≥0.5 mL/kg/hour (approximately 50-80 mL/hour for an average adult) as a baseline minimum 1
• In pediatric patients, the target is 80-100 mL/m²/hour (or 4-6 mL/kg/hour if <10 kg) 1

FDA-Approved Dosing and Expected Response

• The FDA label states that "ordinarily a prompt diuresis ensues" after the initial 20-40 mg IV dose given slowly over 1-2 minutes 2
• If satisfactory response does not occur within 1 hour for acute pulmonary edema, the dose may be increased to 80 mg IV 2
• For edema, if needed, another dose may be administered 2 hours later or the dose may be increased by 20 mg 2

Clinical Context and Predictors

Factors Affecting Response

• Measured creatinine clearance is the only reliable predictor of urinary output response to furosemide (AUC 0.75), with both pharmacokinetics and pharmacodynamics altered when CrCl <40 mL/min/1.73 m² 3
• In moderate heart failure, mean urine volume 6 hours post-40 mg IV furosemide was 1,100 ± 281 mL (approximately 183 mL/hour), while in advanced heart failure it was only 764 ± 257 mL (approximately 127 mL/hour) 4
• Acute kidney injury staging and markers like CVP, BNP, and fractional sodium excretion were NOT predictive of urinary response 3

Quantitative Benchmarks from Research

• In children with normal renal function receiving 1 mg/kg IV furosemide, a significant correlation exists between furosemide urinary excretion and urine volume collected during the first 6 hours 5
• The lowest mean furosemide urinary excretion rate associated with significant diuresis was 0.58 ± 0.33 μg/kg/min 5

Critical Pitfalls to Avoid

• Do not wait beyond 2 hours to assess response - early identification of inadequate diuresis (via hourly urine output or 2-hour spot urine sodium) allows for timely dose escalation 1
• Persistent low urine output despite IV fluid boluses, urine output <4 mL/kg over 8 hours, or serum creatinine 2.5-2.9 mg/dL are indications to hold further diuretic therapy 1
• In ARDS patients without shock, if urine output remains <0.5 mL/kg/hour despite CVP >8 mmHg, furosemide should be given and reassessed in 1 hour 1
• Monitoring must include not just volume but also electrolytes and renal function, as the drug's effectiveness depends heavily on renal clearance 6, 7