Chemical pneumonitis

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Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753; Philip Marcus, M.D., M.P.H.[2]

Overview

Chemical pneumonitis is inflammation of the lung caused by irritation from aspirated vomitus or barium used in gastro-intestinal imaging, ingested gasoline or other petroleum distillates, ingested or skin absorbed pesticides, gases from electroplating, or other irritants. It is sometimes called a "chemical pneumonia", though it is not infectious. May also be caused by the use of inhalants.When the toxic substance is an oil, the pneumonia may be called lipoid pneumonia.

Historical perspective

• Mendelson's syndrome is a type of chemical pneumonia in which aspiration of gastric acid is present.
• It was first described in pregnant females who aspirated gastric content during anesthesia, with development of respiratory distress, cyanosis and lung infiltrates on chest Xray .

Natural History, Complications and Prognosis

Prognosis

• Approximately, 3 in 5 patients have clinical improvement with clearing of chest Xray.
• Approximately, 1 in every 3rd patient shows a rapid improvement followed with a new progressive infiltrate suggesting secondary superimposed bacterial infection or the development of ARDS.
• The least common course but with worst prognosis is the development of fulminant disease resulting in acute death.

History & Symptoms

• Acute onset dyspnea
• Cyanosis
• Low grade fever
• Productive cough with pink frothy sputum

Physical examination

Vitals

• Tachypnea
• Tachycardia
• Fever
• Hypoxemia on pulse oximetry

General

• Cyanosis

Lung

Auscultation

• Diffuse crackles

Diagnosis

• Documented aspiration may be absent or present
• History, symptoms, physical examination
• CXR with infiltrates in dependent pulmonary lobe
• Bronchoscopy - Bronchial inflammation

Chest XRay

• Infiltrates on chest Xray
  • Either unilateral or bilateral
  • Commonly in the dependent pulmonary segment
  • Dependent lobes in the upright position are the lower lobes
  • Dependent lobes in recumbent position are superior segments of the lower lobes and the posterior segments of the upper lobes.

Bronchoscopy

• Erythema of the bronchi

Medical therapy

• Tracheal suction (observed aspiration). However, the initial lung injury can't be prevented as it occurs rapidly

Supportive Pulmonary therapy

• Positive pressure ventilation
• Intravenous fluids (high molecular weight colloid)
• Sodium nitroprusside infusion in the pulmonary artery
• Mechanical ventilation (if respiratory failure)
• Antimicrobial agents prophylactically for superimposed bacterial infection
• Use of steroids is controversial