Methemoglobinaemia is an impaired state of oxygen delivery to tissues, seen when Ferrous iron of haem is oxidized to Ferric iron. Ingestion of nitrobenzene (rarely indoxacarb) containing pesticides either accidentally or with a suicidal intent leads to Methemoglobinaemia. Nitrobenzene is a pale yellow oily liquid with a characteristic bitter almond smell. It is used as an intermediate in the synthesis of aniline dyes, manufacture of benzidine, quinoline, azobenzene, rubber chemicals, screening paints, etc. Methemoglobinaemia results due to the intermediates (nitrobenzene and phenylhydroxylamine) formed during the metabolism of nitrobenzene by the reduction of aniline. Indoxacarb is an oxadiazine pesticide used for the control of cotton ball worm and native budworm in cotton and soya beans. Indoxacarb metabolizes to produce aniline metabolites and aromatic compounds that produce methemoglobin on further metabolism. Here we are reporting a case series of 5 cases of methemoglobinemia following insecticide poisoning which presented to our ICU between 2013-2015. Methemoglobinaemia has remarkably normal pulse oximetry finding with significant cyanosis which presents a diagnostic dilemma. Due to the non-availability of co-oximetry in our institute, which is the most accurate tool to diagnose dyshemoglobinemia, we tried to prognosticate the outcome based on the duration from exposure, clinical history and presentation followed by pulse oximetry findings and lab investigations like ABG and Liver function tests throughout the stay.
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