Cardiac arrhythmias, electrolyte abnormalities and serum cardiac glycoside concentrations in yellow oleander (Cascabela thevetia) poisoning - a prospective study.

BACKGROUND: Consumption of yellow oleander (Cascabela thevetia) is a popular method of intentional self-harm in South India.

OBJECTIVES: The objectives of this study were to identify the cardiac arrhythmias and electrolyte abnormalities in yellow oleander poisoning and to identify the association between electrolyte abnormalities, cardiac glycoside concentrations at admission and the severity of cardiotoxicity. This study was also designed to identify clinical and biochemical parameters at presentation which predict serious arrhythmias and determinants of mortality.

MATERIALS AND METHODS: This was a prospective study among 192 patients who attended our Emergency department after consuming yellow oleander seeds. Patients were monitored with serial ECGs. Serious cardiac arrhythmias included sinus bradycardia <40/min, sinus arrest/exit block, second or third degree AV block, atrial tachyarrhythmias and ventricular tachyarrhythmias. Serum sodium, potassium, magnesium, total calcium and cardiac glycoside concentrations were measured at presentation for all 192 patients. Serial estimation of cardiac glycoside concentration was done in 43 patients who presented within 24 hours of consuming at least five seeds.

RESULTS: At presentation, 46 patients had serious arrhythmias and on follow-up, 11 developed new-onset serious arrhythmia. Sinus bradycardia (27%) was the most common arrhythmia followed by second-degree AV block (17%); multiple arrhythmias were observed in 18%. Digoxin effect in ECG correlated significantly with hyperkalemia. Mortality rate was 5%. Serum sodium, total calcium and magnesium levels did not correlate with cardiotoxicity. Cardiac glycoside concentration was of relatively modest clinical utility to discriminate patients with serious dysrhythmias (AUC: 0.719, 95% CI: 0.63-0.81). Prolonged PR interval and digoxin effect in ECG were significantly associated with an increased likelihood of serious dysrhythmias. Increase in 0.4 number of seed intake increased the odds of mortality by 1.5 times when all other independent variables were kept constant.

CONCLUSION: Cardiac glycoside concentration at the time of presentation predicted the development of new-onset serious arrhythmias. Although serum potassium correlated significantly with cardiac glycoside concentration at admission and overall serious dysrhythmias, it did not predict the development of new-onset serious arrhythmia. On the whole, serious dysrhythmias were significantly associated with higher number of seeds ingested, hypotension at admission, PR interval prolongation, presence of digoxin effect in ECG, hyperkalemia and higher cardiac glycoside concentration. The independent determinants of mortality were larger number of seeds ingested and hypotension at admission. Cardiac glycoside concentration and hyperkalemia failed to be independent markers of serious dysrhythmias as well as mortality.