Sun Qirong, Yue Jianming, Liang Peng
Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, China.
Day Surgery Center, Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, China.
Transl Pediatr. 2022 Jun;11(6):1058-1062. doi: 10.21037/tp-21-588.
Inhaled nitric oxide (iNO) is a choice for the treatment of pulmonary hypertension (PH), especially in cases after cardiac surgery. Potential side effects include the formation of higher oxides of nitrogen and methemoglobin (MetHb). Methemoglobinemia is the oxidation of ferrous iron to iron within hemoglobin, impairing its ability to transport oxygen and resulting in tissue hypoxemia. A level of MetHb >10% will induce clinical hypoxia manifestations, and MetHb >70% may be fatal.
Herein we report a rare case of methemoglobinemia due to iNO therapy in a child after cardiac surgery. We found that as MetHb concentrations increased, pulse oximetry overestimated oxygen supplementation without warning clinicians that dangerous hypoxia was developing. Finally, MetHb and oxyhemoglobin (OHb) in arterial blood gas (ABG) provide diagnostic clues. Methylene blue and low dose vitamin C (VC) were used to successfully save the life of the child.
iNO administration in the intensive care unit should be managed with close monitoring of MetHb levels during treatment. We emphasize the limitations of traditional methods used to assess oxygenation status, especially in the context of methemoglobinemia. In addition, treatment for methemoglobinemia in acute settings should be initiated as soon as possible.
吸入一氧化氮（iNO）是治疗肺动脉高压（PH）的一种选择，尤其是在心脏手术后的病例中。潜在的副作用包括氮的更高氧化物和高铁血红蛋白（MetHb）的形成。高铁血红蛋白血症是指血红蛋白中的亚铁离子被氧化为铁，损害其运输氧气的能力，导致组织低氧血症。高铁血红蛋白水平>10%会引发临床缺氧表现，而高铁血红蛋白>70%可能是致命的。
在此，我们报告一例心脏手术后儿童因iNO治疗导致高铁血红蛋白血症的罕见病例。我们发现，随着高铁血红蛋白浓度的增加，脉搏血氧饱和度仪高估了氧补充情况，却未向临床医生警示危险的缺氧情况正在发展。最后，动脉血气（ABG）中的高铁血红蛋白和氧合血红蛋白（OHb）提供了诊断线索。亚甲蓝和低剂量维生素C（VC）成功挽救了患儿的生命。
在重症监护病房使用iNO治疗时，应在治疗期间密切监测高铁血红蛋白水平。我们强调用于评估氧合状态的传统方法的局限性，尤其是在高铁血红蛋白血症的情况下。此外，急性情况下的高铁血红蛋白血症治疗应尽早开始。
