9: Extracorporeal Cardiopulmonary Membrane Oxygenation

INTRODUCTION

Despite advances in critical care, severe pulmonary and cardiac failure continue to be associated with high mortality. Out-of-hospital cardiac arrest and acute respiratory distress syndrome (ARDS) continue to have a high mortality rate, as high as 30% to 40%, 50% for patients with cardiogenic shock.¹ Patients failing conventional and advanced and supportive measures have few rescue therapy options. In the late 1960s, prolonged cardiopulmonary bypass support was used to provide extended circulatory support and gas exchange. Out of that work was born extracorporeal cardiopulmonary membrane oxygenation (ECMO), which has been widely used in the neonatal population for conditions such as pulmonary hypertension and meconium aspiration syndrome with a high rate of success. However, in the adult population, this level of success did not hold true until recently.

ECMO is continuing to grow in clinical practice, largely as a consequence of advances in technology. The 2009 H1N1 pandemic and the recent CESAR trial² propagated the use of ECMO worldwide. The new Berlin definition of ARDS provided a separate classification for “severe ARDS” as PaO₂/FiO₂ ratio <100, (refer to the ARDS chapter for more detailed information), which is associated with high mortality rates. ECMO should be considered in these patients (Figure 9-1). This chapter will review the clinical indications for ECMO the different modalities available, the associated complications, and contraindications.

ECMO BACKGROUND AND PRINCIPLES

Cardiopulmonary bypass was developed for use in the operating room to provide short-term support during cardiac surgical procedures. Technological advances in cardiopulmonary bypass to promote longer periods of support started in the 1960s. ECMO and extracorporeal life support (ECLS) refers to cardiopulmonary bypass modified for support over days to weeks.

In most circumstances, ECMO is a rescue technique for patients with imminently lethal disease despite conventional support. Earlier implementation may be used for patients with acute organ failure based on anticipated clinical trajectory. Prime ECMO candidates have acute, severe, but reversible respiratory or cardiac failure. In this context, ECMO provides physiologic maintenance for anticipated native organ recovery. ECMO may also be used to bridge patients with irreversible cardiac or respiratory disease to a more durable form of support such as ventricular assist device (VAD) or heart or lung transplant. Clarification of destination candidacy prior to ECMO initiation is an important step for patients with low probability of native organ recovery.

The ECMO system consists of an extracorporeal circuit, pump, and oxygenator. ECMO configuration and type of cannulation dictates the mode of support, ...