Tazón-Varela Manuel Antonio, Padilla-Mielgo Ángel, Villaverde-Plazas Raquel, Espinoza-Cuba Fabiola, Gallo-Salazar Nekane, Muñoz-Cacho Pedro
Emergency Department, Laredo Hospital, 39770 Laredo, Spain.
Community Health Group, Valdecilla Research Institute (IDIVAL), 39011 Santander, Spain.
J Clin Med. 2023 Jan 17;12(3):734. doi: 10.3390/jcm12030734.
Methemoglobinemia (MetHb) is a rare and potentially severe dyshemoglobinemia that can be induced by exposure to oxidizing agents, decreasing the functional capacity of the hemoglobin molecule to transport and release oxygen into the tissues. MetHb can originate from gases with oxidizing capacity generated by internal combustion engines, although since the universalization of catalyst converters in automobiles, a tiny proportion of MetHb poisoning is due to exposure to engine gases and fumes. Within this group, only two cases due to suicidal motivations have been reported in the last 30 years.
Here, we expose the case of a patient with MetHb levels of 25.2% (normal 0-1.5%) who with suicidal motivations had attached and locked a hose to the exhaust pipe of her vehicle with electrical tape, becoming exposed to a sustained concentration of the vehicle's exhaust. Upon her arrival at the emergency department, the presence of generalized greyish cyanosis with alterations of the sensorium, dissociation between saturation measured by arterial blood gas analysis and pulse oximetry (98% vs. 85%), no response to high-flow oxygen therapy, and an excellent response to intravenous methylene blue treatment were highlighted.
This report illustrates an original case of acute toxic acquired MetHb due to inhalation of oxidizing substances originating from the bad ignition of an internal combustion engine. When evaluating a patient with suspected gas intoxication, we usually consider poisoning by the most common toxins, such as carbon monoxide or cyanide. In this context, we propose an algorithm to assist in the suspicion of this entity in patients with cyanosis in the emergency department. MetHb poisoning should be suspected, and urgent co-oximetry should be requested when there is no congruence between cyanosis intensity and oxygen saturation measured by pulse oximetry, if there is discordance between the results of oxygen saturation measured by arterial blood gas and pulse oximeter, and if there is no response to oxygen treatment. This algorithm could be useful to not delay diagnosis, improve prognosis, and limit potential sequelae.
高铁血红蛋白血症（MetHb）是一种罕见且可能严重的血红蛋白异常血症，可由接触氧化剂诱发，降低血红蛋白分子向组织输送和释放氧气的功能能力。MetHb可源自内燃机产生的具有氧化能力的气体，不过自汽车普遍安装催化转化器以来，因接触发动机气体和烟雾导致的MetHb中毒比例极小。在这一群体中，过去30年仅报告了两起因自杀动机导致的病例。
在此，我们报告一例高铁血红蛋白水平达25.2%（正常范围0 - 1.5%）的患者，该患者出于自杀动机，用胶带将一根软管固定并锁在其车辆排气管上，持续接触车辆尾气。她抵达急诊科时，表现为全身灰蓝色发绀伴意识改变，动脉血气分析测得的饱和度与脉搏血氧饱和度存在差异（98%对85%），对高流量氧疗无反应，而对静脉注射亚甲蓝治疗反应良好。
本报告阐述了一例因吸入内燃机点火不良产生的氧化性物质导致的急性中毒性获得性高铁血红蛋白血症的独特病例。在评估疑似气体中毒的患者时，我们通常会考虑由最常见毒素如一氧化碳或氰化物导致的中毒情况。在此背景下，我们提出一种算法，以协助急诊科对发绀患者怀疑存在该病症。当发绀强度与脉搏血氧饱和度测量的氧饱和度不一致、动脉血气测得的氧饱和度结果与脉搏血氧仪结果不一致且对氧疗无反应时，应怀疑高铁血红蛋白中毒，并紧急进行血气共检测定。该算法有助于不延误诊断、改善预后并限制潜在后遗症。
