Methemoglobinemia and Intravascular Hemolysis; Unusual Presentations of Metal Phosphides Poisoning

Introduction: Metal phosphides are highly effective insecticides and rodenticide. They are used as a cheap and effective rodenticide in developing countries. Hemolysis and methemoglobinemia are rare but reported complications of phosphide poisoning
Aim of the work: The aim of this study was to detect the incidence of methemoglobinemia and intravascular hemolysis in some cases of acute phosphide poisoning.
Patients and methods: A cross sectional study was conducted on 50 cases suffering from acute metal phosphide poisoning admitted to Tanta toxicology unit, from the start of October 2014 till the end of March 2015. For each case, the following were done: history taking, physical examination and laboratory investigations (including measurement of methemoglobin (Met-Hb) level, arterial blood gas analysis, routine investigations, lactate dehydrogenase enzyme and complete blood picture with reticulocytic count).
Results: Eight cases (16%) had combined methemoglobinemia and hemolysis. Aluminum phosphide was the toxic agent in seven of them and zinc phosphide in only one. Three cases (6%) had methemoglobinemia alone; one of them was poisoned by aluminum phosphide and the other two by zinc phospide. Another three cases had hemolysis alone; one of them was due to aluminum phosphide toxicity and the other two were due to zinc phospidetoxicity. So the present study included a total of eleven cases (22%) of methemoglobinemia. Their median age was 27 years old, while it was 24 years for patients with normal Met-Hb level. The median delay time was 4 hours for them and 2 hours for cases with normal Met-Hb level with significant statistical differences between both. The mean Met-Hb level was 14.45 ± 9.32% and1.63 ± 0.45% in cases with high and normal Met-Hb level respectively, with a significant statistical difference between both. Furthermore, the mean oxygen saturation showed a significant statistical difference between both. In addition, the present study included a total of eleven cases (22%) of hemolysis. Their median age was 27 years old, while it was 24 years for patients with no hemolysis. The median delay time was 3 hours in them and 2 hours in cases with no hemolysis.
Conclusion: It was concluded that methemoglobinemia and hemolysis can complicate the course of acute phosphide poisoning. 
Recommendations: Further studies on a large scale of cases of acute phosphide poisoning with assessment of the outcome of cases presented with methemoglobinemia and hemolysis and the efficacy of the available treatment for such cases are recommended. Furthermore, it is important that health care professionals be aware of these rare presentations of phosphide poisoning.