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    BRONCHOSPASM

    DEFINITION

    Reversible constriction of the small air passages of the lower
    respiratory tract.

    TOXIC CAUSES

    Beta adrenergic blocking drugs
    Dust
    Hydrocarbon aspiration
    Irritant gases:     Ammonia   
                        Chlorine
                        Fluorine
                        Hydrochloric acid fumes 
                        Nitrogen dioxide
                        Ozone
                        Phosgene
                        Sulphur dioxide
    Metal fumes ("metal fume fever")
    Organophosphates
    Smoke

    NON-TOXIC CAUSES

    Anaphylaxis
    Asthma 

    CLINICAL FEATURES

    Dyspnoea, wheezing, cyanosis and cough are the presenting features. 
    The patient may also be too breathless to speak.  There may be a
    'silent' chest.  There is usually a tachycardia.  In severe cases,
    "pulsus paradoxus" may be evident.

    DIFFERENTIAL DIAGNOSIS

    Airways obstruction due to increased bronchial secretions
    Chronic obstructive airways disease
    Hyperventilation
    Left ventricular failure (cardiac asthma)
    Pulmonary thromboembolism
    Pneumonia
    Pneumothorax
    Respiratory compensation for metabolic acidosis
    Upper airway obstruction

    RELEVANT INVESTIGATIONS

    Arterial blood gases (in severely ill patients)
    Chest X-ray
    Peak Expiratory Flow Rate (PEFR)
    Forced Expiratory volume in one second (FEV1).

    TREATMENT

    Administer supplemental oxygen.

    In the first instance, give a beta-adrenergic agonist such as
     salbutamol as an aerosol using a nebulizer (2ml of 0.5% salbutamol
    respirator solution contains 10mg of salbutamol).  The dose may be
    repeated at 20 minute intervals or even continuously.   Salbutamol 
    may also be given intravenously, starting with an infusion of a
    solution containing 5 mg in 500 ml (10 mcg/mL) at a rate of 3 to 20
    mcg/minute.

    If there is no satisfactory response to 2 to 3 administered doses of
    salbutamol, give  hydrocortisone 300mg, intravenously stat and 200mg
    intravenously every four hours thereafter until the patient is better. 
    Oral  prednisolone 40mg/day may be started at the same time as
    intravenous corticosteroids.

    In severe cases,  aminophylline may be added (a loading dose of
    5 mg/kg infused over 60 minutes, and 0.5 to 0.9 mg/kg each hour
    thereafter, aiming to obtain a serum concentration between 8 and
    20 mg/L). 

    If the patient's clinical condition and arterial blood gases
    deteriorate despite the above measures, intermittent positive pressure
    ventilation (IPPV) may be necessary.  Ventilation however is rarely
    necessary for bronchospasm following toxic exposures.

    CLINICAL COURSE AND MONITORING

    Unless the patient is an asthmatic, improvement is generally rapid. 
    Fatalities are rare.  The patient should be carefully monitored until
    improvement occurs. 

    LONG-TERM COMPLICATIONS

    None from the bronchospasm itself. 

    Sensitization to a toxic substance may result in reactive airways
    disease.

    AUTHOR(S)/REVIEWERS

    Author:        Dr Ravindra Fernando
                   National Poisons Information Centre
                   Faculty of Medicine
                   Kynsey Road
                   Colombo 8
                   Sri Lanka

                   Tel: +94 1 686142
                   Fax: +94 1 691581

    Reviewers:     Rio de Janeiro 9/97: J.N. Bernstein, E. Birtanov,
                   R. Fernando, H. Hentschel, T.J. Meredith, Y. Ostapenko,
                   P. Pelclova, C.P. Snook, J. Szajewski.
                   London 3/98:  T. Della Puppa, T.J. Meredith, L. Murray,
                   A. Nantel.