What is the role of extracorporeal membrane oxygenation for hypoxic failure during an influenza pandemic?

Abstract

Many of us have participated in the planning for disasters and pandemics at the hospitals where we practice. And for many this has included system level plans for surge capacity. Anesthesiologists and critical care physicians are acutely aware of issues of system capacity in general. The recent experiences with influenza A (H1N1) 2009 globally have caused many of us to think about our system capacity and to do mental experiments imagining different scenarios of demand and supply ratios for critical care capacity. When these ratios are imagined in the extreme, the value of primary prevention quickly becomes paramount. However, much of our practice is about how to respond when primary prevention fails or is insufficient. Typically, while we try to steer our populations and patients in a healthier direction, we develop a strategy to deal at each juncture with the worse scenario. In the context of disasters and pandemics we must ask the questions: what is it that might be required at each of the junctures, and what is our capacity to provide it? It is the intersection of these two questions that creates the difficulties. The capacity obviously depends on what we are asked to provide; and in turn what we can provide depends on the capacity required. Nevertheless the history of modern critical care is the process of building capacity. When planning for a pandemic, the natural history of the disease makes critical differences. Modeling the demand for different types of resources is essential for planning capacity. For influenza pandemics that migrate across the world, there is the advantage for some countries of a preview of what to expect from the prior experience of others. Of critical importance however is the development of standardized case report forms so that the natural history of the illness can be compared and even tracked as it evolves. In this regard, Canada has played an important role in developing a standardized case reporting methodology that has been used to compare the disease internationally. At a population level influenza is characterized by a pyramid where very large numbers of people may be exposed, but the severity of illness worsens in exponentially fewer people. Not surprisingly the approach from a public health perspective is to focus on reducing exposure and on immunization. When the illness strikes, therapy for the most part is home-based supportive measures. The most compelling questions arising from influenza A (H1N1) 2009 have been about the determinants of this pyramid of severity. What is the ratio of those with influenza who need hospitalization? What are the co-morbid, phenotypic or genotypic risk factors? Why does it progress so rapidly and so severely in some people? And practically, what are effective treatment or support options in the more severely affected? In this last regard another innovation, in which Canada is actively involved in the leadership, is the International Forum for Acute Care Trialists (InFACT) group – a global consortium of organizations aiming to undertake large scale interventional trials with agents that are simple to use and approved already. Some of the questions include the dosing of existing antiviral agents, or the utility of steroids in reducing the severity of adult respiratory distress syndrome. People who have the most severe manifestation of the illness have died from rapidly evolving multiple organ failure including severe adult respiratory distress syndrome. The approaches to severe hypoxic respiratory A. J. Baker, MD (&) Department of Critical Care Medicine and Anesthesia, St. Michael’s Hospital, 30 Bond Street, 4010 Bond Wing, Toronto, Ontario M5B 1W8, Canada e-mail: bakera@smh.toronto.on.ca