気道緊急時のECMO―救急医療の立場から―

Extracorporeal Membrane Oxygenation（ECMO）in Airway Emergencies：From the Perspective of Emergency Medicine

はじめに

　救急領域で経験する気道緊急のうち，心停止を来しうるすべての症例について体外式膜型人工肺（extracorporeal membrane oxygenation：ECMO）の適応がある。ECMOは心停止を回避するための有用なオプションであるが，気道緊急時の心停止リスクについては定まった評価方法がない。したがってどの段階でECMOを準備するかが非常に重要な判断となるが，外科的気道確保を念頭に置いたときに大腿動静脈確保を始めるというのが実際である。

　救急領域の気道緊急はそのほとんどが外因性疾患（異物・外傷）であり，麻酔科学会気道管理ガイドラインにおおむね準拠した気道管理を行うが，診療科の特性から外科的気道確保に対する閾値は低い。したがってECMO導入の準備はそれなりの頻度で行っているが，多くの場合外科的気道確保はECMO導入より迅速であるため，実際にECMO導入を要する症例は非常に限定的である。本論文では救急領域でECMO導入に至る代表的な症例について提示し，気道緊急における外科的気道確保とECMOの位置づけについて整理するとともに，困難気道管理（difficult airway management：DAM）戦略において有用な2つの組織スキル（Difficult Airway Management Team：DAMT, Crew Resource Management：CRM）について触れる。

　Extracorporeal membrane oxygenation（ECMO）is applicable to all airway emergency cases that may lead to cardiac arrest in an emergency room, and it is a useful option to avoid cardiac arrest. However, there is no established method to evaluate the risk of cardiac arrest in cases that involve an airway emergency. The decision regarding which stage is the most appropriate to prepare for the use of ECMO is thus very important, and in most cases, the femoral artery and vein are secured at the time point at which surgical airway management is considered.

　Most airway emergencies in the emergency field are caused by exogenous diseases（e.g., foreign bodies or trauma）. Airway management is generally performed in accordance with the JSA Airway Management Guidelines, whereas in emergency rooms the threshold for surgical airway management is low due to the underlying disease of the airway emergency. Therefore, although preparation for the introduction if ECMO is relatively frequent, the number of cases in which ECMO is actually required is extremely limited. This is because surgical airway management is always accomplished faster than ECMO introduction. In this article, we（i）introduce typical emergency-field cases that led to the introduction of ECMO, （ii）summarize the positioning of surgical airway management and ECMO in airway emergencies, and（iii）briefly describe two organizational skills that are useful in the difficult airway management（DAM）strategy：a difficult airway management team, and crew resource management.