What is the rationale for using furosemide (Lasix) in a patient with acute post-infectious Glomerulonephritis (GN)?

Furosemide in Acute Post-Infectious Glomerulonephritis

The primary rationale for using furosemide in acute post-infectious glomerulonephritis is for management of edema (option B). Furosemide is indicated for treating the volume overload and edema that commonly occurs in this condition, not primarily for hypertension, hematuria, or proteinuria.

Pathophysiology of Post-Infectious GN and Edema

Post-infectious glomerulonephritis (PIGN) is characterized by immune complex deposition in the glomeruli following an infection (typically streptococcal). This leads to:

• Decreased glomerular filtration rate
• Sodium and water retention
• Development of edema
• Potential hypertension as a secondary effect

Evidence-Based Management of Edema in PIGN

The KDIGO 2021 guidelines for glomerular diseases specifically address management of edema in glomerulonephritis 1:

• Diuretics are the preferred agents for edema management
• Dietary sodium restriction is recommended concurrently
• If diuretic response is insufficient, mechanistically different diuretics should be added

Loop diuretics like furosemide work by:

• Inhibiting the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle
• Increasing sodium and water excretion
• Reducing extracellular fluid volume
• Decreasing edema formation

Dosing and Administration

When initiating furosemide for edema in PIGN:

• Start with appropriate dosing based on severity of edema
• For children, intravenous doses of ≥1 mg/kg have been shown to increase urine volume in all patients with acute glomerulonephritis 2
• Oral doses <2 mg/kg may be less effective and show variable response 2
• Monitor for electrolyte disturbances, especially hyponatremia and hypokalemia

Important Considerations and Monitoring

1. Monitor fluid status: Assess for resolution of edema without causing volume depletion

2. Electrolyte monitoring: Regular checks of sodium, potassium, and chloride levels are essential as electrolyte disturbances are common side effects 3

3. Renal function: Monitor serum creatinine as aggressive diuresis may potentially worsen renal function 1

4. Blood pressure: While furosemide can help with hypertension, this is a secondary effect rather than the primary indication

Potential Pitfalls

1. Overdiuresis: Excessive diuresis can lead to volume depletion, hypotension, and worsening renal function

2. Electrolyte imbalances: Hypokalemia, hyponatremia, and metabolic alkalosis are common complications

3. Limited hemodynamic effect: Research shows furosemide has primarily a diuretic effect rather than a hemodynamic effect on the kidney 4

4. Long-term outcomes: A 10-year follow-up study of patients with epidemic post-infectious glomerulonephritis showed no worsening of renal function parameters over time, suggesting that appropriate management during the acute phase (including edema control) is important 5

In conclusion, while furosemide may have some effect on hypertension, its primary role in post-infectious glomerulonephritis is managing edema through its diuretic effects, not treating hematuria or proteinuria directly.