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.