[Shock caused by poisoning. Use of cardiotropic agents]

Abstract

At toxic doses, cardiotropic drugs may compromise cardiac output leading to circulatory shock. Specific treatment varies depending on the nature and the dose of the drugs ingested as well as causal mechanism including vasopegia, hypovolaemia, cardiogenic effects and sepsis. Progress in our understanding of the pharmacodynamic aspects of intoxication and the development of specific antidotes has led to reduced morbidity and mortality. In addition to the classical inotropes, mainly catecholamines and phosphodiesterase inhibitors, other therapeutic agents may have specific inotrope effects in such ad hoc situations. These include hypertonic alkaline saline solution, calcium, glucagon, hydroxocobalamine and other cobalt salts, oxygen and immunotoxicotherapy. Together with volum replacement, dobutamine at the dose of 7 to 20 micrograms/kg/min can usually restore cardiac performance in cases of carbamate-induced circulatory shock. In case of tricyclic antidepressant overdose, treatment should include respiratory assistance and infusion of alkaline sodium solutions to both reverse the extracellular acidosis and correct sodium balance. Catecholamines may be necessary in cases with severe hypotension. Major vasoplegia and impaired intraventricular conduction may be induced by overdoses of chloroquine and class I antiarrhythmic drugs. Signs of gravity are: ingested dose above 4 g, QRS > or = 0.12 s or systolic arterial pressure < or = 80 mmHg. Treatment with epinephrine, respiratory assistance and diazepam has been proven effective during the acute phase, but right catheterism is often required due to major haemodynamic instability during the first 72 first hours. Beta-blockers have both a bronchoconstrictor and respiratory depressor effects favouring cardiovascular failure by hypoemia. Symptoms occur in 30-40% of the cases of overdose. Shock results from the reduction in blood pressure and cardiac inotropism. Glucagon, isoprenaline and epinephrine, prescribed in that order, can considerably reduce mortality to less than 4%. Despite the development of specific molecules, the risk of mortality due to toxic shock caused by antiarrhythmics, chloroquine, colchicine, calcium inhibitors and paraquat remains high.