[Beta-blocker intoxication].

Abstract

SEVERITY: Beta-blocker intoxication is not frequent but can produce particularly severe or fatal conditions which must not be underestimated. Severity of beta-blocker intoxication varies from one compound to another. The more toxic drugs are propranolol, sotalol, oxprenolol, metoprolol, atenolol, acebutolol, labetalol, and carvedilol. Besides the drug type, history taking can provide a precise assessment of risk, particularly important in when elderly patients with a cardiovascular history have taken more than 20 tablets, when emergency care is provided late, and when other cardiotoxic or psychotoxic drugs have been coingested. IMPLICATIONS: The diagnosis of beta-blocker intoxication must be suspected in any case associating hypotension and bradycardia. The main cardiovascular complications are cardiogenic shock, atrio-ventricular conduction disorders, and obviously life-threatening ventricular arrhythmia with cardiac arrest. Centrally induced respiratory arrest is a rare but dreadful consequence which can occur suddenly even without hemodynamic failure. Neurologic toxicity is mainly expressed by consciousness disorders and more sporadically by seizures. Laboratory tests show variable serum potassium, lactic acidosis, hypoxia-hypercapnia resulting from hypoventilation, and rarely hypoglycemia. The ECG should be recorded early because electrocardiographic signs usually appear before clinical signs and QRS enlargement is a factor predictive of severe ventricular arrhythmia. INTENSIVE CARE: The patient must be placed in an intensive care unit for continuous multiparametric monitoring. Besides gastric evacuation and symptomatic measures, treatment essentially requires glucagon for its positive inotropic effect after high intravenous doses. If glucagon infusion is ineffective or unavailable, an alternative would be to use high doses of vasoactive agents, choosing isoproterenol or epinephrine as the first intention drugs.