LARYNGEAL OEDEMA

    DEFINITION

    Laryngeal oedema is a condition characterized by acute or gradual
    onset with swelling of the larynx (vocal cords), and causing
    hoarseness, resonant barky cough, stridor and moderate to severe
    respiratory distress.

    TOXIC CAUSES (Partial list - many compounds)     

    Ammonia vapour
    Chlorine gas
    Mustard gas and other irritants used as chemical weapons
    Tear gases
    Dusts, mists and vapours of strong acids, alkali, and other corrosive
    or irritating compounds  

    NON-TOXIC CAUSES

    Anaphylaxis
    Infections (croup, epiglottitis)
    Thermal burns
    Trauma

    CLINICAL FEATURES

    Stridor and hoarseness are the principle findings.  Other features
    include tachypnoea, respiratory distress, and painful cough.  Forceful
    coughing or straining may produce facial petechiae and subconjunctival
    haemorrhage. Sudden laryngospasm or complete airway obstruction may
    occur, leading to acute hypoxaemia and death.

    There is often other evidence of acute irritant chemical exposure,
    such as conjunctival redness and excessive tearing, and sore throat.

    DIFFERENTIAL DIAGNOSIS

    Asthma
    Diphtheria
    Foreign body
    Laryngeal cysts and tumours

    RELEVANT INVESTIGATIONS

    Blood gases: if there is evidence of acute respiratory distress
    (findings may include decreased pH, decreased pO2, decreased or
    increased pCO2) 
    X-ray of larynx and chest
    Laryngoscopy (perform with caution)

    TREATMENT

    Humidified oxygen 
    Tracheal intubation or tracheotomy for patients with impending airway
    obstruction or severe hypoxaemia.
    Nebulized  racemic epinephrine (adrenalin) may be a useful
    temporizing measure if laryngeal oedema is caused by acute allergic
    angioedema or viral croup, and is of potential value in the management
    of toxic laryngeal oedema associated with hyperaemia.  The dose of
    nebulized  racemic epinephrine is 0.05 mLs/kg to a maximum of 1.5 mLs
    diluted in normal saline to a volume of 5 mLs.  Oxymetazoline may
    serve as an alternative if racemic epinephrine is not available. 
    Corticosteroids are of uncertain value and even when injected
    intravenously have a delayed onset of effect of several hours.

    CLINICAL COURSE AND MONITORING 

    Frequent re-evaluation of airway patency
    Vital signs
    Pulse oximetry

    LONG-TERM COMPLICATIONS

    Permanent damage to the larynx
    Brain damage from hypoxia 

    AUTHOR(S)/REVIEWERS

    Author:        Dr Anthony Wong, Director, Jabaquara Poisons Centre,
                   Sao Paulo, Brazil.

    Peer review:   Cardiff 9/96: V. Afanasiev, M. Burger, T. Della Puppa,
                   L. Fruchtengarten, K. Olsen, J. Szajewski.