體外膜氧合治療的臨床使用

Extracorporeal membrane oxygenation (ECMO) is a technique for providing life support to patients with severe cardiac and/or pulmonary problems. This was an adaption of conventional cardiopulmonary bypass techniques which require the diversion of blood from a major systemic vessel through a gas exchange device (membrane oxygenator) and back to a major blood vessel. Because the ECMO is a closed system without blood reservoir, it does not require much anticoagulant to prevent embolus formation in the patient. Two types of ECMO are clinically used. The venoarterial (VA) approach has served as the primary mode of cannulation for both cardiac and respiratory failure since the advent of extracorporeal support. Utilizing a central vein for drainage and an artery for return, VA cannulation thus provides direct cardiovascular support. Alternatively, venovenous (VV) cannulation provides a means of extracorporeal support for patients with severe respiratory failure who do not require cardiac support. Utilizing a major vein for blood drainage and a vein for the return of oxygenated blood to the heart, the VV approach, while not directly providing circulatory support, replaces the pulmonary gas exchange and theoretically offers indirect cardiac support without ligation of a major artery. ECMO is currently in wide use by patients with critically traumatic conditions, cardiac failure, or severe respiratory failure. Early application of ECMO may offer survival benefit to carefully selected patients. Appropriate ventilator settings and adjustments during ECMO therapy are crucial in order to avoid ventilator-induced lung injury. Because ECMO therapy is costly, the decisions to apply or not apply the modality and the timing to remove it are important issues to consider regarding the allocation of limited medical resource.