Shekar Kiran, Buscher Hergen, Brodie Daniel
Adult Intensive Care Services and Critical Care Research Group, the Prince Charles Hospital, Brisbane, Queensland, Australia.
Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
J Thorac Dis. 2020 Nov;12(11):6854-6860. doi: 10.21037/jtd-20-1515.
Venovenous extracorporeal membrane oxygenation (VV ECMO) is now an established modality of support for patients with the who are failing evidence-based conventional therapies. Minimising ventilator-induced lung injury is the guiding principle behind patient management with VV ECMO. Patients with acute respiratory distress syndrome (ARDS) supported with VV ECMO are liberated from ECMO at a stage when native lungs have recovered sufficiently to support physiologic demands and the risks of iatrogenic lung injuries after discontinuation of ECMO are perceived to be small. However, native lung recovery is a dynamic process and patients rely on varying degrees of contributions from both native lungs and ECMO for gas exchange support. Patients often demonstrate near total ECMO dependence for oxygenation and decarboxylation early in the course of the illness and this may necessitate higher ECMO blood flow rates (EBFRs). Although, reliance on high EBFR for oxygenation support may remain variable over the course of ECMO, blood flow requirements typically diminish over time as native lungs start to recover. Currently, protocol-driven modulation of the EBFR based on changing physiologic needs is not common practice and consequently patients may remain on higher than physiologically necessary EBFR. This exposes the patient to potential risks because maintaining higher blood flows often requires a less restrictive fluid balance and deeper sedation. Both may be harmful in the setting of recovery from ARDS. In this article, we propose a strategy that involves daily assessments of native lung function and a protocol-driven daily optimisation of EBFR. This is followed by optimisation of sweep gas flow rate (SGFR) and the fraction of delivered oxygen in the sweep gas (FdO). This staged approach to weaning VV ECMO allows us to fully utilise the "decoupling" of oxygenation and decarboxylation that is possible only during extracorporeal support. This approach may benefit patients by allowing for greater fluid restriction, more aggressive fluid removal, expedited weaning of sedation and neuromuscular blocking agents (NMBAs), and early physical rehabilitation. Ultimately, prospective studies are needed to evaluate optimal VV ECMO weaning practices.
静脉-静脉体外膜肺氧合（VV ECMO）现已成为对那些经循证医学的传统治疗无效的患者的一种既定支持方式。尽量减少呼吸机诱发的肺损伤是VV ECMO患者管理背后的指导原则。接受VV ECMO支持的急性呼吸窘迫综合征（ARDS）患者在自身肺脏已充分恢复以支持生理需求且停用ECMO后医源性肺损伤风险被认为较小时的阶段脱离ECMO。然而，自身肺脏恢复是一个动态过程，患者在气体交换支持方面依赖自身肺脏和ECMO不同程度的贡献。患者在疾病早期通常表现出几乎完全依赖ECMO进行氧合和脱碳，这可能需要更高的ECMO血流速率（EBFRs）。尽管在ECMO过程中对高EBFR进行氧合支持的依赖可能会有所变化，但随着自身肺脏开始恢复，血流需求通常会随时间减少。目前，基于生理需求变化对EBFR进行方案驱动的调节并不常见，因此患者可能会维持高于生理必需的EBFR。这使患者面临潜在风险，因为维持较高的血流通常需要限制较少的液体平衡和更深的镇静。在ARDS恢复的情况下，这两者都可能有害。在本文中，我们提出一种策略，包括每日评估自身肺功能以及对EBFR进行方案驱动的每日优化。随后优化扫气流量速率（SGFR）和扫气中输送氧气的分数（FdO）。这种分阶段撤离VV ECMO的方法使我们能够充分利用仅在体外支持期间才可能实现的氧合和脱碳“解耦”。这种方法可能通过允许更大程度的液体限制、更积极的液体清除、加快镇静和神经肌肉阻滞剂（NMBAs）的撤机以及早期身体康复而使患者受益。最终，需要前瞻性研究来评估最佳的VV ECMO撤机实践。
