Organophosphorus Compound Poisoning and Serum Cholinesterase Levels: An Observational Study on Clinical Severity and Outcome

Abstract

Background: Organophosphorus compound (OPC) poisoning remains one of the leading causes of hospital admission and preventable mortality in agrarian regions of the developing world. Serum cholinesterase estimation and clinical severity scoring at presentation are widely used to grade the poisoning and anticipate outcome. The objective of this study is to assess the demographic and clinical profile of patients with acute OPC poisoning, to correlate serum cholinesterase levels with clinical severity (Peradeniya Organophosphorus Poisoning score) and with outcome (death versus survival), and to identify factors associated with mortality. Methods: This observational study was carried out in the Department of Internal Medicine, Stanley Medical College, Chennai, over a six-month period. One hundred clinically suspected cases of OPC poisoning aged above 12 years were evaluated; patients with mixed/double poisoning, chronic medical illness, concurrent use of confounding drugs, and pregnancy were excluded. Serum cholinesterase was estimated at admission in all patients, and clinical severity was graded using the Peradeniya Organophosphorus Poisoning (POP) score. Outcome was dichotomised into a death group and a survival group and analysed with the unpaired t test, Chi-square/Fisher's exact test, and Pearson correlation, taking p<0.05 as significant. Results: Among the analysed cohort (30 patients; 6 deaths, 24 survivors), mortality was exclusively seen in the severe category of the POP score (100% of deaths versus 4.17% of survivors, p<0.0001). The mean amount of OPC consumed was significantly higher in the death group (131.67 ± 60.80 ml) than in survivors (65.63 ± 26.51 ml, p=0.0003). Mean serum cholinesterase was markedly lower in the death group (336.17 ± 164.66 IU/L) compared with survivors (2732.33 ± 2415.77 IU/L, p=0.0235), and fell progressively with increasing clinical severity (mild 5090.09, moderate 782.92, severe 315.29 IU/L; p<0.0001, ANOVA). A strong inverse correlation was found between serum cholinesterase level and POP score (Pearson r = -0.767, R² = 0.588, p<0.0001). Requirement of mechanical ventilation (100% versus 8.33%, p<0.0001) and longer ICU stay (5.17 versus 2.79 days, p=0.0201) were also significantly associated with death. Age, gender, occupation and the type of OPC consumed did not differ significantly between the two groups. Conclusion: Low serum cholinesterase level at admission correlates strongly with higher clinical severity, need for mechanical ventilation, prolonged ICU stay and mortality in acute OPC poisoning. Serum cholinesterase, together with the Peradeniya score, is a simple and reliable bedside tool for early risk stratification and outcome prediction.

Keywords: Organophosphorus poisoning; serum cholinesterase; pseudocholinesterase; Peradeniya score; pesticide poisoning; mortality; mechanical ventilation.