Extracorporeal membrane oxygenation

Extracorporeal Membrane Oxygenation (ECMO) enables the technology associated with cardiopulmonary bypass to be utilized in the setting of intensive care units. Although ECMO is based on CPB there are fundamental differences (seeTable 14.1). ECMO provides a means of supporting blood gas exchange using a membrane oxygenator. Venous blood is pumped through the oxygenator, where gas exchange occurs, and is actively re-warmed before being returned to the patient, via either the venous or arterial circulation. There are thus two types of ECMO (see Table 14.2): veno-venous (VV) ECMO, in which blood is returned to the patient via a vein; and; veno-arterial (VA) ECMO, in which the blood is returned to an artery. VA ECMO provides gas exchange as well as direct cardiac support, as arterial circulatory flow is augmented by the pump in the ECMO circuit. VV ECMO only provides gas exchange. History: The first successful use of ECMO was reported by Hill for the treatment of posttraumatic ARDS in an adult patient in 1972. Following this early success, in 1979 Zapol conducted a randomized controlled trial of VA ECMO in adult patients in the USA. It showed no benefit of VA ECMO compared to continued conventional treatment with approximately 10% survival in each group. However, this trial was fundamental to the development of a number of treatment principles relating to ECMO: selecting patients before irreversible ventilator-associated lung injury has occurred; the use of lung protective ventilation; the use of low-range heparinization; and the use of veno-venous ECMO for respiratory support. Following Zapol's study, clinical ECMO use was largely confined to indications in the neonatal and pediatric age groups.