I NSIGHT Dr Matthew Cove
Associate Consultant, Dept of Cardiac, Thoracic & Vascular Surgery (CTVS), National University Heart Centre, Singapore (NUHCS) Dr Matthew Cove graduated from Leicester Medical School in England in 1999. He completed his post-graduate internal medicine training at Providence St Vincent, Portland Oregon, in the United States, where he was first exposed to critical care medicine. He then practiced internal medicine with the Mayo Health System in western Wisconsin for two and a half years, before undergoing further training in critical care medicine. He completed a fellowship in critical care medicine at the University of Pittsburgh in the United States and then moved to Singapore to practice as an Intensivist. During his time in Singapore and Pittsburgh, Dr Matthew Cove became interested in the clinical application of extracorporeal technology in critically illness, as well as the research implications. Email: firstname.lastname@example.org
Extracorporeal membrane oxygenation (ECMO) is one of the new, hot topics in the management of the critical ill. ECMO provides support to adult patients with respiratory failure, or cardiogenic shock, refractory to conventional support strategies. It is also used in children, particularly for conditions such as primary pulmonary hypertension of the new born and congenital heart disease. However, it is not without controversy and it may be surprising to learn that the technology is not especially new; ECMO was first successfully used in 1971. The concept is ingeniously simple – blood is removed from the body via a large cannula placed into a central vein, pumped through an oxygenator, where oxygenation and decarboxylation occurs and then returned to the body. In veno-arterial ECMO (VA-ECMO), blood is returned to an artery (Figure 1) and in veno-venous ECMO (VV-ECMO), blood is returned via a vein (Figure 2). Returning blood through an artery provides both circulatory and respiratory support and is most suitable for
Extracorporeal Membrane Oxygenation (ECMO)
Figure 2: VV-ECMO, deoxygenated blood is removed from a femoral vein, pumped through an oxygenator and the oxygenated is then returned via the other femoral vein or the superior vena cava.
Figure 1: VA-ECMO, deoxygenated blood is removed from a femoral vein and returned to a femoral artery after being pumped through an oxygenator.
circulatory failure, whereas VV-ECMO provides only respiratory support. Although the concept is simple, the provision of ECMO requires a multi-disciplinary team that is composed of perfusionists, specially trained nurses, intensivists and cardiothoracic surgeons. Despite being available for over 40 decades, acceptance of ECMO had a slow start. After the publication of the first successful use in 1971, there was an initial flurry of excitement. The National Institute of Health (NIH) in the USA quickly funded a randomised controlled trial of ECMO in acute respiratory distress syndrome (ARDS). The results were published in 1979; and disappointingly, no improvement in outcomes was demonstrated (Figure 3).
However, this reflected a misunderstanding of ECMO and ARDS at the time; perhaps not surprising since ARDS was a relatively new disease first described in 1967. Following the NIH trial, many clinicians lost interest in the technology but one clinician, Robert Bartlett, refused to believe ECMO had no future. He sought out the optimal patients for ECMO – neonates who developed respiratory distress due to pulmonary hypertension of the new born. By using ECMO in these patients he demonstrated a survival improvement from barely 10% to over 75%. However, it took several small trials and a large, randomised controlled trial in the UK to convince the larger medical community. Indeed, this dramatic jump in survival is often cited when people consider the
Survival With ECMO
Survival without ECMO
Zapol et al 1979 1 Peek et al 2009 2
Figure 3: Trials using ECMO in adult acute respiratory distress syndrome
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