BETA-ADRENERGIC CRISIS

    DEFINITION

    Stimulation of beta-adrenergic receptors due to exposure to partial or
    pure beta-agonists, resulting in a syndrome characterised
    predominantly by tachycardia, hypokalaemia, and tachydysrhythmias.

    TOXIC CAUSES

    Salbutamol (albuterol) and terbutaline
    Isoprenaline (isoproterenol)
    Orciprenaline (metaproterenol)  
    Ephedrine
    Pseudoephedrine
    Phenylpropranolamine
    Phenylephrine.

    CLINICAL FEATURES

    Sinus tachycardia, hypokalaemia and tachydysrhythmias. 
    Hyperglycaemia, tremor, sweating, confusion and hyper- or hypotension. 
    Convulsions, rhabdomyolysis and acute renal failure have also been
    reported.

    DIFFERENTIAL DIAGNOSIS

    Sympathomimetic (including xanthines) poisoning
    Anticholinergic poisoning
    Hyperthyroidism.
    Acute hypo- or hypertension of non-toxic origin.
    Disulfiram/alcohol reaction. 

    RELEVANT INVESTIGATIONS

    Routine clinical chemistry, especially serum potassium and blood
    sugar.
    Creatine phosphokinase activity.
    Electrocardiogram.
    Serum creatinine. 

    TREATMENT

    Asymptomatic or uncomplicated sinus tachycardia:  observation only is
    required.

    Correction of hypokalaemia and/or dehydration.

    Pronounced, symptomatic sinus tachycardia:  A selective ß1-selective
    antagonists such as  esmolol at a dose of 50 to 100 µg/kg/minute
    intravenously.  Give an initial loading dose of 500 µg/kg if a more
    rapid onset of action (5 to 10 minutes) is desired.  Alternatively,
     atenolol or  metoprolol could be used, the latter especially in

    asthmatic patients. The dose of  atenolol is 2.5 mg intravenously
    over 2.5 minutes and then repeat this dose every 5 minutes until a
    satisfactory response is observed.  A total dose of 5 mg should be
    adequate and a total dose of 10 mg should not be exceeded. The dose of
     metoprolol is 5 mg intravenously over 2.5 minutes and then repeat
    this dose every 5 minutes until a satisfactory response is observed. 
    A total dose of 10 mg should be adequate and a total dose of 20 mg
    should not be exceeded.

    Ventricular tachycardia:  lidocaine (lignocaine) 1 mg/kg
    intravenously as a bolus, followed by a further dose of 0.5 mg/kg if
    required.  If necessary, further administration of an intravenous
    infusion of 20 to 40 µg/kg/minute.  Cardioversion if necessary.

    CNS excitation and convulsions:  diazepam as per Convulsions
    Treatment Guide.

    CLINICAL COURSE AND MONITORING

    A beta-adrenergic crisis is transient, the exact duration of signs and
    symptoms dependent on the agent involved and the dose received. 
    Monitoring should continue until the crisis resolves and should
    include vital signs, cardiac rhythm, and fluid and electrolyte
    balance.

    LONG-TERM COMPLICATIONS

    Unlikely unless hypoxic organ damage results from ventricular
    dysrhythmias or convulsions.

    AUTHOR(S)/REVIEWERS

    Author:        Albert J. Nantel
                   Directeur, Centre de Toxicologie du Québec
                   Quebec
                   Canada

    Reviewers:     Cardiff 9/96: M. Burger, J. Deng, L. Fruchtengarten,
                   L. Lubomirov, T. Meredith, H.Persson