Is furosemide (Lasix) a treatment for hyperkalemia?

Is Furosemide a Treatment for Hyperkalemia?

Yes, furosemide can be used to treat hyperkalemia, but it is not a first-line acute treatment and works best in specific clinical contexts, particularly when managing spironolactone-induced hyperkalemia in cirrhotic patients with ascites or in non-acute hyperkalemia with adequate renal function.

Clinical Context and Mechanism

Furosemide is a loop diuretic that promotes potassium excretion in the urine by acting on the Na-K-2Cl receptors in the thick ascending limb of Henle's loop 1. While hypokalemia is actually a common side effect of furosemide, this kaliuretic property can be therapeutically exploited to correct hyperkalemia in certain situations 1.

Primary Indication: Spironolactone-Induced Hyperkalemia

The most well-established use of furosemide for hyperkalemia is in cirrhotic patients receiving aldosterone antagonists:

• Furosemide should be added when spironolactone monotherapy causes hyperkalemia in patients being treated for ascites 1
• The combination of spironolactone and furosemide in a 100:40 mg ratio maintains normokalemia while effectively managing ascites 1
• When hyperkalemia develops during spironolactone therapy, furosemide can be added sequentially rather than stopping the aldosterone antagonist entirely 1
• Initial combination therapy (spironolactone 100 mg + furosemide 40 mg) yields faster ascites control with lower risk of hyperkalemia compared to aldosterone antagonist monotherapy 1

Role in Acute vs. Non-Acute Hyperkalemia

Important distinction: Furosemide is not a first-line treatment for acute, life-threatening hyperkalemia:

• In acute hyperkalemic emergencies, the recommended sequence is: (1) calcium injection, (2) beta-2 agonists, (3) insulin/glucose, (4) sodium bicarbonate (if acidotic), (5) hemodialysis, and (6) furosemide or cation exchange resins only in non-acute situations 2
• Furosemide is appropriate for mild hyperkalemia as part of initial measures including dietary potassium restriction, correction of acidosis, and increasing urinary excretion 3

Mechanism of Action in Hyperkalemia

Furosemide works by:

• Increasing urinary potassium excretion through enhanced distal tubular flow 1
• Counteracting the potassium-retaining effects of aldosterone antagonists 1
• In hyporeninemic hyperkalemia, furosemide can stimulate the renin-aldosterone system in volume-expanded patients, with plasma renin activity increasing significantly after 2 weeks of furosemide 20 mg daily 4

Clinical Scenarios Where Furosemide is Effective

Use furosemide for hyperkalemia in these contexts:

• Cirrhotic patients on spironolactone who develop hyperkalemia (most common and best-supported indication) 1
• Type II pseudohypoaldosteronism, where furosemide combined with dDAVP successfully controls hyperkalemia, hyperchloremic acidosis, and hypertension 5
• Non-acute hyperkalemia with adequate renal function, where increasing urinary potassium excretion is feasible 3, 2
• Hyporeninemic hyperkalemia with volume expansion, where furosemide can restore renin-aldosterone responsiveness 4

Critical Limitations and Contraindications

Do not rely on furosemide alone when:

• Severe hyperkalemia (>6.0 mmol/L) with ECG changes is present—this requires immediate membrane stabilization and intracellular potassium shift 2
• Significant renal impairment exists, as furosemide requires adequate glomerular filtration to work 1
• Acute kidney injury is present—diuretics should be stopped 1
• The patient has severe hypokalemia (<3 mmol/L), in which case furosemide should be temporarily withheld 1

Monitoring Requirements

When using furosemide for hyperkalemia management:

• Monitor serum potassium, creatinine, and sodium frequently, especially during the first weeks of treatment 1
• Aldosterone antagonists should be reduced or stopped if severe hyperkalemia (>6 mmol/L) persists despite furosemide 1
• Assess for development of hypokalemia, which may occur with excessive furosemide dosing 1

Practical Algorithm

For hyperkalemia management with furosemide:

1. If cirrhotic with ascites on spironolactone: Add furosemide 40 mg daily, maintaining 100:40 ratio with spironolactone 1
2. If mild hyperkalemia (5.0-5.5 mmol/L) with normal renal function: Consider furosemide 20-40 mg daily as part of conservative management 3
3. If severe hyperkalemia (>6.5 mmol/L) or ECG changes: Do NOT use furosemide as primary treatment—use calcium, insulin/glucose, beta-agonists, and consider dialysis 2
4. If hyperkalemia persists despite furosemide: Stop aldosterone antagonists and consider alternative treatments including dialysis 1