During refractory cardiogenic shock and cardiac arrest, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used to restore a circulatory output. However, it also impacts significantly arterial oxygenation. Recent guidelines of the Extracorporeal Life Support Organization (ELSO) recommend targeting postoxygenator partial pressure of oxygen (PPOSTO2) around 150 mmHg. In this narrative review, we intend to summarize the rationale and evidence for this PPOSTO2 target recommendation. Because this is the most used configuration, we focus on peripheral VA-ECMO. To date, clinicians do not know how to set the sweep gas oxygen fraction (FSO2). Because of the oxygenator’s performance, arterial hyperoxemia is common during VA-ECMO support. Interpretation of oxygenation is complex in this setting because of the dual circulation phenomenon, depending on both the native cardiac output and the VA-ECMO blood flow. Such dual circulation results in dual oxygenation, with heterogeneous oxygen partial pressure (PO2) along the aorta, and heterogeneous oxygenation between organs, depending on the mixing zone location. Data regarding oxygenation during VA-ECMO are scarce, but several observational studies have reported an association between hyperoxemia and mortality, especially after refractory cardiac arrest. While hyperoxemia should be avoided, there are also more and more studies in non-ECMO patients suggesting the harm of a too restrictive oxygenation strategy. Finally, setting FSO2 to target strict normoxemia is challenging because continuous monitoring of postoxygenator oxygen saturation is not widely available. The threshold of PPOSTO2 around 150 mmHg is supported by limited evidence but aims at respecting a safe margin, avoiding both hypoxemia and severe hyperoxemia.

中文翻译：

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外周静脉-动脉 ECMO 期间优化 PO2：叙述性回顾

在难治性心源性休克和心脏骤停期间，静脉-动脉体外膜肺氧合 (VA-ECMO) 用于恢复循环输出。然而，它也显着影响动脉氧合。体外生命支持组织 (ELSO) 的最新指南建议将氧合器后的氧分压 (PPOSTO2) 设定在 150 mmHg 左右。在这篇叙述性综述中，我们打算总结这一 PPOSTO2 目标推荐的理由和证据。因为这是最常用的配置，所以我们专注于外围 VA-ECMO。迄今为止，临床医生不知道如何设置吹扫气氧气分数 (FSO2)。由于氧合器的性能，在 VA-ECMO 支持期间动脉高氧血症很常见。由于双循环现象，在这种情况下对氧合的解释很复杂，取决于自然心输出量和 VA-ECMO 血流。这种双重循环导致双重氧合，沿主动脉具有不均匀的氧分压 (PO2)，以及器官之间的不均匀氧合，具体取决于混合区的位置。关于 VA-ECMO 期间氧合的数据很少，但一些观察性研究报告了高氧血症与死亡率之间的关联，尤其是在难治性心脏骤停后。虽然应该避免高氧血症，但也有越来越多的针对非 ECMO 患者的研究表明过度限制性氧合策略的危害。最后，将 FSO2 设定为严格的正氧血症是一项挑战，因为对氧合器后氧饱和度的持续监测并不广泛。