Utility of red blood cell acetylcholinesterase measurement in mechanically ventilated subjects after organophosphate poisoning.

BACKGROUND Many patients with organophosphate poisoning require mechanical ventilation. Muscle acetylcholinesterase (AChE) activity determines the impairment of muscle force generation, and red blood cell (RBC) AChE has been regarded as a surrogate for muscle AChE in organophosphate poisoning. Therefore, this study was conducted to investigate whether RBC AChE at presentation can predict the duration of mechanical ventilatory support and whether RBC AChE at weaning can predict weaning trial outcomes in patients on mechanical ventilation for organophosphate poisoning. METHODS This retrospective observational case series identified 74 patients with a history of mechanical ventilation secondary to organophosphate poisoning and whose RBC AChE levels were available at presentation to the emergency department, at 24 h of presentation, or at weaning. Data were collected for plasma cholinesterase assay results, weaning outcome, duration of mechanical ventilation, and details of patient management (including ICU stay and amount of atropine and pralidoxime administered). RESULTS RBC AChE activity levels at presentation and at 24 h of presentation had a negative correlation with duration of mechanical ventilation in subjects who ingested dimethyl organophosphate, but this correlation was not observed for those who had ingested diethyl or unclassified organophosphate. The optimal cutoff value of RBC AChE activity at presentation for predicting mechanical ventilation for < 7 d was 1,330 U/L in subjects intoxicated with dimethyl organophosphate. However, there was no difference in RBC AChE activity at the time of weaning trial between successful and failed weaning events, regardless of the chemical formulation of organophosphate. CONCLUSIONS We conclude that RBC AChE activity within 24 h of presentation can help predict the duration of mechanical ventilation for dimethyl organophosphate intoxication; however, RBC AChE activity at the time of weaning trial may not be a suitable parameter for predicting a patient's ability to be weaned from mechanical ventilation.