Reduced Levels of Serum Potassium and Plasma Cholinesterase in Acute Organophosphate Poisoning: Possible Predictive Markers

Background: It is becoming apparent that although inhibition of cholinesterase plays a key role in organophosphate (OP) toxicity, other factors are also important. One of the contributing factors for severity of OP poisoning is electrolyte imbalances such as hypokalemia. This study was aimed at evaluating the value of hypokalemia in association with plasma cholinesterase (PChE) levels in predicting morbidity and mortality of acute OP poisoning. Methods: In this cross sectional study patients with definitive diagnosis of OP poisoning were enrolled. Pre-interventional clinical features were observed and noted with severity assessment as per Proudfoot classification, along with measurement of serum potassium ion ([K+]) concentration and PChE level. Results: Fifty OP poisoned patients (33 men, 17 women) were enrolled with median age of 27.1 years. The most common clinical manifestation was congested conjunctiva (82%) followed by miosis (78%) and bronchorrhea (78%). A total of 21 cases presented with one or more severe clinical features according to Proudfoot classification. Among them, 61.9% of cases (13 out of 21) developed hypokalemia. Muscle weakness or fasciculation developed with mean serum [K+] of 3.31 ± 0.11. Ventilatory support was required at the mean serum [K+] of 3.27 ± 0.10 mmol/L. Fatality was noted when the mean serum [K+] reduced to 2.90 ± 0.06 mmol/L. Correlation of the clinical effects and serum [K+] was significant (P < 0.001). In addition, muscle weakness, fasciculation, convulsion and respiratory distress were associated with marked suppression of PChE (>75%). Death was mostly observed among patients who had respiratory distress associated with hypokalemia and grossly reduced PChE. Conclusion: For severe clinical features of OP poisoning, serum [K+] and PChE level are greatly reduced. Hence, these biochemical findings can be proposed as OP poisoning predictive markers. Clinicians and medical toxicologists should consider hypokalemia associated with reduced PChE level as alarming signs of poor prognosis in OP poisoned patients.