Prognostic value of serum cholinesterase in organophosphate poisoning

Objective: To determine whether serum cholinesterase level has a prognostic value in human acute organophosphorus poisoning. Design: Cohort (prospective) prognosis study. Setting: Medical ICU at University Hospital. Patients: Thirty consecutive patients admitted to the ICU for acute organophosphate poisoning. Measurements: Serum cholinesterase level was measured in all patients at the time of hospital admission. Severity of intoxication was assessed by the total dose of atropine required to relieve poisoning manifestations, the Simplified Acute Physiology Score, the need for assisted ventilation, and by a specific grading system previously validated that identified two groups of patients: group 1 (low severity, n=18) and group 2 (high severity, n=12). Results: Serum cholinesterase level did not correlate with the total dose of atropine or with the Simplified Acute Physiology Score. Mean serum cholinesterase level was not significantly different between group 1 and group 2 patients (448 ± 409 U/L in group 1 compared with 611 ± 575 U/L in group 2 (p=NS); it was also not significantly different between patients with and without mechanical ventilation support (567 ± 571 vs 470 ± 409, respectively). Conclusion: Serum cholinesterase levels have no prognostic value in acute organophosphate poisoning. Thus, a grading system to identify high-risk patients based on this measurement is most likely unreliable.