Choking agents and chlorine gas - History, pathophysiology, clinical effects and treatment.

INTRODUCTION: Choking agent exposure, among them chlorine gas, occurs in household or industrial accidents, chemical warfare and terrorist attacks.

AIMS: Review of published animal and human data regarding the history, pathophysiology, clinical effects and management of chlorine exposure.

PATHOPHYSIOLOGY: Highly soluble agents cause quick upper respiratory tract symptoms. Chlorine gas has a medium solubility, also causing delayed lower airway symptoms, mainly due to its oxidizing potential by releasing hypochlorous and hydrochloric acid, but also by interacting with Transient Receptor Potential channels.

SYMPTOMS: Eyes may show conjunctival injection, abrasions and corrosions. Burns of the oronasal mucosa and trachea can occur. Dyspnea, bronchospasm and possible retrosternal pain occur frequently. Glottis edema or laryngospasm are acute life-threatening emergencies. Chlorine gas can cause toxic pneumonitis, lung edema and acute respiratory distress syndrome (ARDS).

MANAGEMENT: General management includes physical examination, pulse oximetry and arterial blood gases. Eyes should be irrigated, humidified oxygen and inhalative bronchodilators administered. An EKG, cardiac enzymes and complete-blood-count should be obtained if there is retrosternal pain. Routine chest x-ray is not recommended - except if pulmonary edema is suspected. Laryngoscopy should be performed if glottis edema is suspected. Sodium bicarbonate inhalation after chlorine gas inhalation is discussed controversially. Mechanical ventilation with continuous-positive-airway-pressure or intubation/tracheotomy with high positive-end-expiratory-pressure may be necessary. Glucocorticoids for prevention of pulmonary edema should be applied restrictively. Prophylactic antibiotics are not recommended. In severe ARDS, extracorporeal membrane oxygenation (ECMO) can be considered.

CONCLUSION: Treatment is mainly symptom oriented. New and promising therapies are in development.