Persistence of yellow phosphorus paste in gastric content beyond one hour: an observational study using bedside silver nitrate and molybdate testing.

INTRODUCTION: Yellow phosphorus poisoning remains a major cause of morbidity and mortality in South Asia. International toxicology guidelines restrict decontamination to within one hour of ingestion, despite limited human evidence defining the duration of intragastric persistence of yellow phosphorus paste. Objective bedside assessment of ongoing gastric activity may help refine decontamination decisions, particularly in delayed presenters.

METHODS: This observational study included 22 consecutive patients presenting within 24 hours of confirmed yellow phosphorus paste ingestion to a tertiary care emergency department over a five-year period. Gastric aspirates were tested using a silver nitrate assay with confirmatory molybdate testing. Demographic data, time to presentation, decontamination measures, organ dysfunction, and in-hospital outcomes were recorded. Given the small sample size over five years, analyses were descriptive.

RESULTS: Silver nitrate positivity indicating phosphine activity was detected in 8 of 22 patients (36.3%). Positivity was observed in all patients presenting within one hour (2/2), remained frequent at 2-8 hours (4/9, 44%), and persisted at 8-24 hours after ingestion (2/11, 18%). Gastric lavage was performed in nine patients (40.9%), while activated charcoal was administered in four patients, all in combination with gastric lavage. All nine patients who underwent gastric lavage survived. All six deaths (27.3%), due to refractory shock (n = 2) or acute hepatic failure (n = 4), occurred among patients who did not undergo gastric lavage. Major organ failure, mechanical ventilation, and vasopressor use were confined to the non-gastric lavage group.

DISCUSSION: Detection of gastric phosphine activity across all presentation windows provides clinical evidence that reactive yellow phosphorus material may persist well beyond conventional decontamination time limits. Although outcome differences cannot be interpreted causally, the consistent survival among patients who received gastric lavage is hypothesis-generating and challenges strictly time-based decontamination restrictions.

CONCLUSION: Residual gastric activity consistent with yellow phosphorus may persist up to 24 hours after ingestion, supporting prospective evaluation of activity-guided decontamination strategies.