Hemodinamiese veranderings tydens hartglikosied vergiftiging by skape met spesiale verwysings na epoksiscillirosidien

Abstract

Cardiac glycosides are extensively used as drugs in the treatment of cardiac failures. Unfortunately it often causes toxicity due to over dosage or suicidal attempt. In animals it is one of the most common causes of plant poisoning in South Africa. Plants of the Iridaceae, Liliaceae an Grossulaceae contain cardiac glycosides. The main toxic principal of the Natal Yellow tulp HomePia glauca is let, 2a Epoxyscillirosidine and was issolated by Naude. By injecting Epoxyscil l irosidine intraveneously to sheep and registering its effect on ECG, bloodflow and the first dirivative of flow a study was made of the hemodynamic changes occuring during the effect of this Toxin. Very low dosages (.001 mg/Kg) were first given and gradually increased to the toxic dose in order to study the toxic effects. By using different dosages it was found that certain sheep has a much higher resistance to the toxin than others. Possible explanations for this is discussed . Acquired immunity may be the most possible explanation. It was found that the toxin has a strong positive inotropic action on the heart. As soon as toxic dosages were used delayed SA nodal discharges, AV blocking, AV dissociation, premature ventricular depolarisations and ectopic ventricular rhythms developed. Ventricular

tachycardia and fibrilation developed before death. The general influence of the toxin is that all the abnor= malities occur in a cyclic patern. The larger the dosage the longer the abnormal periods and the shorter the normal periodes. Possible explanations for this coupled rhythms are discussed as well as the existance of a central regulating mechanism. This control mechanism may function through the baroreceptors or may be centrally situated. In the literature it is stated that the reseptor for the cardiac glycosides is most possibly situated in the Na+K+-ATPase enzyme system. Possible causes tor the inotropic action is discussed. A new approach to the treatment of tulip poisoning in animals is suggested.