METAHEMOGLOBINEMIA: CHALLENGES IN EMERGENCY SERVICES

Resumo

CLINICAL CASE:
INTRODUCTION: Metahemoglobinemia can go unnoticed, which is why its diagnosis can be delayed due to its low frequency and sometimes the lack of detailed assessment of arterial blood gases in emergency services. 
CASE REPORT: A 63-year-old male with no signficant history was transferred by his employers from construction site, reporting los of alertness 30 minutes prior to the accidental ingestión of a setting Accelerator used as a cement additive in construction, ingesting approximately 100ml; he was seen to be marble-like with SaO2 75% room air and with an ECG of 7 points, peripheral cyanosis and marble-like skin, with crackles inbilateral lung bases on auscultation.Endotraqueal intubation was performed and mechanical ventilation was started, when taking blood simples, the black color of the same is striking, despite having high ventilatory parameters, the patient persists cyanotic and with low oxygen saturations, he is attached with hypotension 70/43 mmHg, arterial blood gas: pH 7.23,PCO2 34.1, PO2 378, lactate 9.6, HCO3 13.8, PaO2/FiO2 100%, FmetHb 91%; given the gasometric result and identification of the ingested product, treatment was initiated with methylene blue at a dose of 0.2ml/kg (1% solution) plus vasopresor; after the administration of the antidote, a considerable improvement in the clinical picture is seen, being extubated at 36 hours and discharged 8 days after event.
 DISCUSSION: Metahemoglobinemia is a pathology characterized by the oxidation of divalent iron to trivalent iron in the hemoglobin molecule. Oxygen can bind to hemoglobin only in its divalent form, and as a result of this binding, oxygen is temporarily oxidized to the ferric form. Symptoms are a direct consequence of inadequate oxygen transport; it can occur as a result of a congenital defect or an acquired disorder, which are more common. Treatment with methylene blue is indicated in symptomatic patients with levels greater than 20% or even les but with central nervious system, cardovascular and pulmonary involment; quickly reverses the adverse effects. Considering that the literature mentions that levels above 70 % are fatal.