Pulmonary Edema, Noncardiogenic

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Bilateral diffuse alveolar infiltrates are present with severe hypoxemia

• Pulmonary capillary wedge pressure (PCWP) is < 18 mm Hg

• Arterial partial pressure of oxygen/inspired oxygen concentration (PaO₂/FiO₂) of ≤ 200 mm Hg

GENERAL CONSIDERATIONS

• Acute respiratory distress syndrome (ARDS) is the most severe form of acute lung injury

• ARDS may be a manifestation of several conditions, such as sepsis, aspiration, hypertransfusion, toxic inhalation, severe nonthoracic trauma, and cardiopulmonary bypass

• Other incompletely understood causes include high-altitude pulmonary edema, neurogenic pulmonary edema, narcotic overdose, eclampsia, and cardioversion

• Clinically, one-third of ARDS patients have sepsis

• The mechanism of lung injury varies, but the common pathway involves elevated pulmonary capillary pressure resulting in pulmonary endothelial damage with increased capillary permeability

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Tachypnea, dyspnea, labored breathing

PHYSICAL EXAM FINDINGS

• Pulmonary rales

• Hypoxemia, tachycardia

DIFFERENTIAL DIAGNOSIS

• Cardiogenic pulmonary edema (PCWP is typically > 18 mm Hg)

• Lymphangitic carcinomatosis (PCWP is < 18 mm Hg)

• Unilateral pulmonary edema after evacuation of large pleural effusion (PCWP is normal)

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Blood cultures may be positive in sepsis

• Plasma B-type natriuretic peptide (BNP) may be used to distinguish heart failure and cardiogenic pulmonary edema from noncardiogenic causes

IMAGING STUDIES

• Chest x-ray:

  • – Shows diffuse patchy bilateral infiltrates initially; then confluence with air bronchograms

  • – The costophrenic angles are spared and effusions are unusual

  • – Heart size is normal

• Echocardiography: shows normal left ventricular function

DIAGNOSTIC PROCEDURES

• Right heart catheterization may be necessary to exclude cardiogenic shock

TREATMENT

CARDIOLOGY REFERRAL

• Suspected cardiogenic shock

HOSPITALIZATION CRITERIA

• All patients with ARDS are hospitalized

MEDICATIONS

• Treat the underlying cause if possible

• Give supplemental oxygen and noninvasive ventilatory support in early stages of acute lung injury

• Give mechanical ventilatory support with positive end-expiratory pressure and low tidal volumes (6–10 mL/kg) in established ARDS

• Novel ventilation strategies, including high-frequency ventilation and liquid ventilation, hold promise for improvement of outcomes

THERAPEUTIC PROCEDURES

• Endotracheal intubation is almost always required

MONITORING

• ECG monitoring in hospital as appropriate

• Routine right-heart catheter monitoring is not recommended

DIET AND ACTIVITY

• Intensive care unit protocol for parenteral nutrition in the critically ill

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

• Resolution of ARDS

• Correction of the underlying problem

FOLLOW-UP

• Depends on the cause

COMPLICATIONS