Why do we give furosemide (Lasix) for pulmonary hypertension and pulmonary fibrosis?

Why We Give Furosemide (Lasix) for Pulmonary Hypertension and Pulmonary Fibrosis

We do NOT routinely give furosemide for pulmonary hypertension or pulmonary fibrosis as primary therapy for these conditions—furosemide is indicated when these patients develop volume overload, congestive symptoms, or right heart failure, not for the underlying pulmonary vascular or fibrotic disease itself.

The Core Misunderstanding

This question reflects a common clinical misconception. Furosemide is not a treatment for pulmonary hypertension (PH) or pulmonary fibrosis (PF) per se. Let me clarify the actual indications:

When Furosemide IS Indicated

For Pulmonary Hypertension:

• When PH leads to right ventricular failure with systemic venous congestion (peripheral edema, ascites, hepatic congestion)
• The diuretic addresses the consequence (volume overload from RV failure), not the PH itself
• Current guidelines for PH management 1 do not recommend diuretics as primary PH therapy—they recommend PH-specific therapies (phosphodiesterase-5 inhibitors, endothelin receptor antagonists, prostacyclins)

For Pulmonary Fibrosis:

• When patients develop left heart failure or volume overload from comorbid cardiac disease
• When PF progresses to cause pulmonary hypertension with subsequent right heart failure
• The 2022 ATS/ERS/JRS/ALAT guidelines 2 for idiopathic pulmonary fibrosis make NO recommendation for diuretics as treatment for the fibrotic process itself
• Antifibrotic agents (nintedanib, pirfenidone) are the primary therapies for IPF 2

The Evidence Against Routine Diuretic Use

In Heart Failure (the actual indication):

• Loop diuretics like furosemide are recommended for patients with heart failure and congestive symptoms 3, 4
• Furosemide 20-80mg IV initially, titrated to response 5, 6
• The goal is relief of congestion, not treatment of underlying cardiac dysfunction 3

Important Caveats:

• Diuretics have NOT been shown to improve survival in heart failure 3
• They can worsen renal function, which is independently associated with increased mortality 7, 8
• In acute heart failure with pulmonary edema, combination therapy with furosemide PLUS nitrates is superior to furosemide alone 8

The Pathophysiology Disconnect

Why furosemide doesn't treat PH or PF:

1. Pulmonary Hypertension results from:

   • Pulmonary vascular remodeling
   • Endothelial dysfunction
   • Vasoconstriction
   • Thrombosis
   • None of these are addressed by diuresis 1

2. Pulmonary Fibrosis results from:

   • Progressive fibrotic destruction of lung parenchyma
   • Abnormal wound healing
   • Extracellular matrix deposition
   • Diuretics have no anti-fibrotic properties 2

Historical Research Context

Some older studies 9, 10, 11 suggested furosemide might have direct pulmonary vascular effects (reducing pulmonary vascular resistance, decreasing lung water through non-diuretic mechanisms). However:

• These were small animal studies from the 1970s-1980s
• No clinical trials have validated these findings in humans with PH or PF
• Current guidelines do not incorporate these theoretical benefits into treatment recommendations

The Correct Clinical Approach

For Pulmonary Hypertension:

1. Confirm diagnosis with right heart catheterization 1
2. Initiate PH-specific therapy based on etiology (Group 1 PAH gets targeted therapies; other groups get treatment of underlying condition) 1
3. Add furosemide ONLY if right heart failure with volume overload develops
4. Typical dosing: 40-80mg IV/PO daily, titrated to clinical response 6

For Pulmonary Fibrosis:

1. Confirm diagnosis with high-resolution CT and multidisciplinary discussion 2
2. Initiate antifibrotic therapy (nintedanib or pirfenidone) 2
3. Screen for pulmonary hypertension with echocardiography 12, 2
4. If PH develops (common complication in IPF 13), consider PH evaluation and lung transplant referral 2
5. Add furosemide ONLY for volume overload from cardiac complications

For PH-IPF (Combined Disease):

• This represents a particularly high-risk population with poor prognosis 14, 13
• Inhaled treprostinil is currently the only approved PH therapy with evidence in PH-ILD 14
• Most PAH therapies have failed or caused harm in this population 14
• Furosemide may be needed for RV failure but does not treat the underlying PH or fibrosis

Common Clinical Pitfalls

1. Using diuretics as primary therapy for dyspnea in PH/PF patients - This delays appropriate diagnosis and treatment
2. Over-diuresis - Can worsen cardiac output and renal function, particularly dangerous in PH where preload is critical for RV function
3. Assuming improvement in symptoms from diuresis means the underlying disease is controlled - Symptom relief from volume removal does not modify disease progression

Bottom line: Furosemide treats volume overload and congestion, which may complicate PH or PF, but it is not a treatment for the pulmonary vascular disease or fibrotic lung disease themselves. The question conflates symptom management with disease-modifying therapy.