What are the causes and treatments of pulmonary edema?

Pulmonary Edema: Causes and Treatment

Causes of Pulmonary Edema

Cardiogenic Causes (Hydrostatic)

The most common cause of pulmonary edema is increased hydrostatic pressure from cardiac dysfunction, which forces fluid from pulmonary capillaries into the interstitium and alveoli. 1

Acute Heart Failure and Myocardial Dysfunction

• Acute myocardial infarction or acute myocardial injury represents a critical cause requiring revascularization within 2 hours 1
• Decompensated chronic heart failure with left ventricular systolic or diastolic dysfunction 1
• Acute valvular disorders including severe mitral or aortic insufficiency, particularly from mechanical complications like papillary muscle rupture or ventricular septal defect 1
• Prosthetic valve thrombosis 1

Hypertensive Crisis

• Rapid, excessive blood pressure elevation typically manifests as acute pulmonary edema 1
• The mechanism involves marked increase in systemic vascular resistance superimposed on insufficient myocardial functional reserve, causing increased left ventricular diastolic pressure and subsequent pulmonary venous congestion 2

Arrhythmias

• Atrial fibrillation with rapid ventricular response shortens diastolic filling period and increases left atrial pressure 1

Other Cardiac Causes

• Aortic dissection with valvular or coronary involvement 1
• Massive pulmonary embolism causing acute right ventricular failure with secondary elevation of pulmonary pressures 1

Non-Cardiogenic Causes (Increased Permeability)

Non-cardiogenic pulmonary edema results from increased capillary permeability allowing protein-rich fluid to leak into alveoli, distinguishable by pulmonary edema occurring at normal pulmonary capillary wedge pressure. 3, 4

Acute Respiratory Distress Syndrome (ARDS)

• Diffuse pulmonary infections 1
• Acute interstitial lung diseases 1
• Drug or chemical-induced lung injury 1

High-Altitude Pulmonary Edema (HAPE)

• Occurs in susceptible individuals exposed to hypoxia at altitudes typically above 2,500 meters 1

Iatrogenic Causes

• Fluid overload from excessive intravenous fluid administration 1
• Injurious mechanical ventilation 1
• Massive blood transfusions 1

Special Pulmonary Vascular Causes

Pulmonary Veno-Occlusive Disease (PVOD)

• Rare condition causing pulmonary edema through venous obstruction rather than typical cardiac or permeability mechanisms 5
• Characterized by digital clubbing, bi-basal crackles, severe hypoxemia, and very low diffusion capacity 5
• High-resolution CT shows subpleural thickened septal lines and centrilobular ground-glass opacities 5
• Critical warning: vasodilators, especially prostanoids, must be used with extreme caution due to high risk of severe drug-induced pulmonary edema 5

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Treatment of Pulmonary Edema

Immediate Stabilization

The first priority is ensuring adequate oxygenation and ventilation, preferably with high-flow nasal cannula oxygen or noninvasive positive pressure ventilation before intubation. 5, 6

• Oxygen therapy for hypoxemia with SpO2 <90% or PaO2 <60 mmHg 5
• Non-invasive ventilation (NIV) or endotracheal intubation with mechanical ventilation for respiratory distress 5
• Positive end-expiratory pressure (PEEP) improves gas exchange by recruiting collapsed alveoli 3

Cardiogenic Pulmonary Edema Treatment

Vasodilators (First-Line for Severe Cases)

High-dose nitrates combined with low-dose furosemide are superior to high-dose diuretic treatment alone for severe pulmonary edema. 7

• Start glyceryl trinitrate (GTN) at 20 mcg/min and increase to 200 mcg/min as tolerated, or isosorbide dinitrate (ISDN) at 1-10 mg/h 7
• Confirm systolic BP >110 mmHg before initiating and rule out severe aortic or mitral stenosis 7
• Check BP every 3-5 minutes during titration; reduce dose if systolic BP falls below 90-100 mmHg 7
• Target systolic BP reduction of 10 mmHg mean arterial pressure or systolic BP 90-100 mmHg 7
• Nitrate effectiveness is limited to 16-24 hours with continuous high-dose IV infusion due to tolerance 7
• Avoid low-dose nitrates due to limited effectiveness 7

Diuretics

For acute pulmonary edema, the usual initial dose of furosemide is 40 mg injected slowly intravenously over 1-2 minutes. 8

• If unsatisfactory response within 1 hour, increase to 80 mg IV slowly over 1-2 minutes 8
• Use low-dose diuretics when combined with high-dose nitrates 7
• Avoid high-dose diuretics as monotherapy due to worsening hemodynamics and increased mortality 7
• For resistant peripheral edema, combine loop diuretic with thiazide (e.g., bendroflumethiazide or metolazone) for a few days with careful monitoring 5

Opiates

• Morphine may be useful in acute pulmonary edema to reduce anxiety, relieve dyspnea, provide venodilation, and reduce sympathetic drive 5
• Caution: opiates induce nausea (requiring antiemetic) and depress respiratory drive, potentially increasing need for invasive ventilation 5

Inotropes and Vasopressors (Reserved for Shock)

• Reserve dobutamine for patients with severe reduction in cardiac output causing vital organ hypoperfusion (usually hypotensive/shocked) 5
• Warning: inotropes cause sinus tachycardia, may induce myocardial ischemia and arrhythmias, and have long-standing concern for increased mortality 5
• Consider levosimendan or phosphodiesterase III inhibitor (milrinone) to counteract beta-blocker effects 5
• Norepinephrine for marked hypotension, but increases LV afterload 5

Specific Cardiac Interventions

• Coronary reperfusion for ST-elevation myocardial infarction 5
• Electrical cardioversion or pacing for life-threatening arrhythmias 5
• Surgical or percutaneous intervention for acute mechanical complications 5

Critical Pitfalls to Avoid

Never use beta-blockers (especially labetalol) to treat hypertension in the setting of pulmonary edema from topical vasoconstrictors or acute cardiac stress, as this can worsen cardiac output and precipitate cardiac arrest. 5

• Beta-blockade impairs compensatory mechanisms (increased heart rate and contractility) needed to preserve cardiac output when systemic vascular resistance is elevated 5
• If beta-blocker is inadvertently given and pulmonary edema develops, immediately administer glucagon to counteract loss of cardiac contractility 5
• Esmolol's brief duration may prevent progression to cardiac arrest compared to labetalol 5

Non-Cardiogenic Pulmonary Edema Treatment

• Focus on treating underlying cause (infection, sepsis, inflammatory process) 3, 4
• Supportive care with mechanical ventilation and PEEP 3
• Corticosteroids for ARDS remain controversial with no established optimal dose 3
• Avoid excessive fluid administration 1

PVOD-Specific Considerations

Patients with PVOD should be managed only in centers with extensive PH experience due to risk of severe pulmonary edema after initiation of PAH therapy. 5

• Lung transplantation is the only curative therapy; refer eligible patients immediately upon diagnosis 5
• High-dose diuretics, oxygen therapy, and slow increases in epoprostenol doses if vasodilators are attempted 5