What diagnostic studies and initial treatments should I order for a 66‑year‑old patient presenting with crackles suggestive of pulmonary edema or pleural effusion?

Diagnostic Workup for a 66-Year-Old with Crackles

Order a chest X-ray immediately, followed by bedside lung ultrasound and serum NT-proBNP to differentiate cardiogenic pulmonary edema from other causes of respiratory distress. 1, 2

Initial Imaging Strategy

Chest radiography serves as the first-line imaging modality to confirm the presence of fluid and lateralize the process, though it has limited sensitivity (73%) and approximately 20% of patients with acute heart failure will have normal or non-diagnostic films. 1, 2 Look specifically for:

• Peri-bronchial cuffing (thickening around bronchi from interstitial fluid) 2
• Cardiomegaly (enlarged cardiac silhouette, though significant left ventricular dysfunction can exist without it) 2
• Pulmonary venous congestion (upper lobe blood flow redistribution with prominent vascular markings) 2
• Pleural effusion (typically bilateral in heart failure) 1, 2
• Obliteration of costophrenic angles (earliest sign of pleural effusion) 1

Superior Diagnostic Tool: Lung Ultrasound

Lung ultrasound significantly outperforms chest X-ray with 94% sensitivity and 92% specificity for pulmonary edema versus 73% sensitivity and 90% specificity for chest radiography. 2, 3 This bedside technique should be performed immediately if available, looking for:

• B-lines (vertical artifacts arising from the pleural line) indicating interstitial edema—four or more B-lines in a single intercostal space constitute "lung rockets" diagnostic of pulmonary edema 1, 4
• Pleural effusion characteristics (simple versus complex, free-flowing versus loculated) 1
• Absence of B-lines or presence of "spared areas" which suggest non-cardiogenic causes like ARDS 4

In one prospective study of 99 dyspneic patients, ultrasound identified 16 of 18 cases (89%) that chest X-ray missed, demonstrating clear superiority for detecting pulmonary edema. 3

Essential Laboratory Tests

Obtain the following blood work immediately: 1

• NT-proBNP or BNP: NT-proBNP ≥1500 pg/mL strongly supports cardiac origin; <1500 pg/mL suggests alternative diagnosis 1
• Troponin (to exclude acute coronary syndrome as precipitant) 1
• Complete blood count (infection, anemia) 1
• Basic metabolic panel (renal function, electrolytes) 1
• Serum albumin (hypoalbuminemia can cause transudative effusions) 1

Physical Examination Priorities

Assess immediately for:

• Oxygen saturation: SpO₂ <92% indicates severe disease requiring urgent intervention 1
• Blood pressure: Hypertension with crackles suggests fluid overload; hypotension suggests cardiogenic shock or intravascular depletion 1
• Mental status using AVPU (Alert, Visual, Pain, Unresponsive) as indicator of hypoperfusion 1
• Unilateral versus bilateral findings: Unilateral dullness, decreased breath sounds, and reduced chest expansion suggest pleural effusion requiring different management 1

Echocardiography Timing

Echocardiography is mandatory immediately only if cardiogenic shock or hemodynamic instability is present. 1 For stable patients, perform echocardiography after initial stabilization to evaluate:

• Left ventricular systolic function 1
• E/e' ratio (left ventricular filling pressures) 1
• Systolic pulmonary artery pressure 1
• Valvular abnormalities 1

Initial Treatment Approach

If hypertension and adequate perfusion are present with confirmed pulmonary edema, initiate intravenous furosemide 40 mg IV push over 1–2 minutes. 5 If inadequate response within 1 hour, increase to 80 mg IV over 1–2 minutes. 5

Contraindications to immediate diuretic therapy include: 6

• Marked hypotension or cardiogenic shock
• Clinical signs of severe hypovolemia despite edema
• Anuria

Critical Pitfalls to Avoid

Do not rely on chest X-ray alone—normal radiography does not exclude pulmonary edema, and ultrasound or natriuretic peptides must confirm the diagnosis. 1, 2

Beware of confounding factors for natriuretic peptides: 2

• Obesity causes falsely low BNP/NT-proBNP despite true pulmonary edema
• Renal dysfunction elevates natriuretic peptides independent of volume status
• Sacubitril/valsartan interferes with BNP measurement; use NT-proBNP instead in patients on this medication 1, 2

If the patient has unilateral findings or fails to improve within 48 hours, strongly consider alternative diagnoses including parapneumonic effusion, empyema, pulmonary embolism, or malignancy, and proceed to diagnostic thoracentesis under ultrasound guidance. 1, 7