Differences between organophosphates in respiratory failure and lethality with poisoning post the 2011 bans in Sri Lanka

Introduction: Self-poisoning with organophosphorus pesticides (OPs) has high morbidity and mortality. The most toxic OP formulations have been progressively banned in Sri Lanka over the past three decades. However, respiratory failure (RF) requiring ventilation remains a major contributor to fatalities. Therefore, this study was conducted to examine the frequency of RF and death after poisoning with the currently available OPs to determine if further bans might be warranted to reduce the burden of OP poisoning in Sri Lanka. Methods: Five hundred and forty patients with confirmed OP self-poisoning were prospectively observed throughout their hospital stay following admission to Peradeniya hospital in the Central Province of Sri Lanka. Clinical data including the time and duration of intubation were documented prospectively in structured datasheets. Results: One hundred and forty-nine patients required ventilation (27%), and 34 (23%) of those died. Males with alcohol co-ingestion were more likely to develop RF. Compared to other OPs, profenofos (Odds Ratio [OR] = 2.5, 95% CI: 1.5-3.9), and quinalphos (OR = 4.5, 95% CI: 1.6-12.6) were more likely to, and chlorpyrifos (OR = 0.2, 95% CI: 0.1-0.4) less likely to lead to RF than other OPs. Profenofos was also associated with higher mortality (OR = 2.3, 95% CI: 1.1-4.6) than other OPs. The median time to intubation was longer for profenofos, but the duration of intubation was similar for all OP formulations. Conclusion: RF and deaths following OP ingestion continue to be a major problem in Sri Lanka, with profenofos being the major current agent of concern. Strategies to replace profenofos and quinalphos use with less toxic insecticides should be explored. Doctors should be alert to the high probability of delayed and prolonged RF after profenofos poisoning.