Clinical profile and outcome of patients hospitalized with dimethyl and diethyl organophosphate poisoning

Abstract

The two major classes of organophosphate compounds, dimethyl and diethyl organophosphates, have different toxicokinetic properties. This study evaluated the clinical profile and outcomes in patients admitted with poisoning with these two classes of organophosphates. Methods. This retrospective study spanned 6 years (2002–2007). Patients were treated with atropine and supportive care including ventilation, as required, and followed up until death or hospital discharge. Oximes were not administered. Of the 422 charts retrieved, 396 fulfilled inclusion criteria. Data on the clinical profile, ventilation, length of hospital stay, incidence of intermediate syndrome and mortality were extracted. Results. The mean (±standard deviation) age was 31.4 ± 12.7 years with a male preponderance (2.6:1). The median (interquartile range (IQR)) admission pseudocholinesterase level of 317 (222–635) U/L indicated significant inhibition of cholinesterase activity. The median lag-time to presentation to our hospital was 5 (IQR 3–8.5) hours. Oximes were administered at a primary center in 33 patients (8.3%). Dimethyl organophosphate was ingested by 141 patients, diethyl organophosphate by 108, S-alkyl organophosphate by 2, and an un-identified organophosphate by 145 patients. Ventilation was required in 260 patients (65.7%); the median duration of ventilation being 7.5 (IQR 3–12) days. Overall mortality was 13.1%. There was a significant difference between dimethyl and diethyl organophosphate compounds in ventilatory requirement (76% vs. 56%, adjusted odds ratio (OR) 2.37, 95% CI 1.01–5.57, p = 0.047), duration of ventilation (11 (4–15) vs. 5 (2–9) days, adjusted OR 1.12, 95%CI 1.04–1.21, p = 0.002) and incidence of intermediate syndrome (72/125 (58%) vs. 24/92 (26%), adjusted OR 2.84, 95%CI 1.38–5.86, p = 0.004). Mortality was similar in the two groups (20/141 (14%) vs. 7/108 (6%), dimethyl vs. diethyl organophosphate, adjusted OR 1.29, 95%CI 0.43–3.94, p = 0.65). Conclusions. Patients admitted with dimethyl organophosphate poisoning have a worse outcome compared with diethyl organophosphate poisoning for clinically relevant patient outcomes.

Keywords:

• Dimethyl organophosphate
• Diethyl organophosphate
• Intermediate syndrome
• Outcome
• Poisoning
• Ventilation

Acknowledgements

This project was partly supported by the South Asian Clinical Toxicology Research Collaboration which is funded by the Wellcome Trust International Collaborative Research Grant (GR071669MA).