Intentional sodium nitrite ingestion with severe methemoglobinemia

Abstract

Sodium nitrite (NaNO2) is a commonly available chemical that can be fatal even in small amounts when ingested. It acts by oxidizing iron in hemoglobin, converting it from its ferrous to ferric state, known as methemoglobin. Methemoglobin cannot directly bind with oxygen, leading to decreased oxygen delivery and subsequent cyanosis, along with systemic effects such as hypotension, metabolic acidosis, hyperlactatemia, and coronary ischemia. Methemoglobinemia can be suspected when a patient presents with severe cyanosis despite normal oxygen saturation, is otherwise asymptomatic, and shows no improvement with supplemental oxygen. We present a case of a nineteen-year-old woman who was brought in with intentional ingestion of NaNO2, with a subsequent serum methemoglobin level of 65%. The patient was treated with intravenous methylene blue, leading to restoration of normal methemoglobin levels within twenty-four hours. Severe methemoglobinemia can be fatal at high levels, but early clinical recognition and urgent initiation of its antidote, methylene blue, can rapidly reverse the condition. This case highlights the value of co-oximetry in the work-up of hypoxemia and cyanosis, and the need to suspect methemoglobinemia when cyanosis does not improve with supplemental oxygen.