Extracorporeal Membrane Oxygenation in the Context of the 2009 H 1 N 1 Influenza A Pandemic

Background: Extracorporeal membrane oxygenation (ECMO) incorporates surgical techniques as adjuncts in the management of refractory respiratory dysfunction. For many years, its primary application was for support of neonatal infants in cardiorespiratory failure. As the 2009 H1N1 influenza A pandemic developed, more reports came in of severe respiratory dysfunction and even death that seemed to be occurring preferentially in younger adults. Centers with the capability began to use ECMO to salvage these patients. Results: The H1N1 virus is a subtype of influenza A. The hemagglutinin receptor binding is similar to that of the seasonal influenza virus, but 2009 H1N1 also binds to a2,3-linked receptors, which are found in the conjunctivae, distal airways, and alveolar pneumocytes. Influenza viruses elude host immune responses through drift and shift in the hemagglutinin (HA) and neuraminidase (NA) proteins. The incubation period ranges from 1–7 days. The majority of patients present with fever and cough, but a broad spectrum of clinical syndromes has been reported, and laboratory testing remains the mainstay of diagnosis. Most patients recover within a week without treatment. The H1N1 virus remains largely sensitive to the NA inhibitors but is resistant to the matrix protein-2 inhibitors. Extracorporeal membrane oxygenation provides continuous pulmonary (and sometimes cardiac) support and minimizes ventilator-induced lung injury. The potential for life-threatening complications is high. In 2009, in the Conventional Ventilation or ECMO for Severe Adult Respiratory Failure (CESAR) randomized trial of ECMO, the overall survival rate was 63% in the ECMO group compared with 47% in the control group (p1⁄4 0.03). Similar studies have been reported from Australia and New Zealand, Canada, and France. Conclusions: Supportive management is continued along with ECMO. Antiviral drugs and antimicrobial agents should be given as appropriate, as should nutritional support. Volume management should be used. Ventilator settings should be reduced as ECMO support allows, with a goal of reducing airway pressures, ventilator rate, and FiO2. Complications of ECMO are common. Bleeding, the most common, can result in death, especially if it occurs intracranially. Extracorporeal membrane oxygenation (ECMO) incorporates surgical techniques as adjuncts in the management of refractory respiratory dysfunction. For many years, its primary application was for support of neonatal patients in cardiorespiratory failure. Adult ECMO was practiced in relatively few centers. In February 2009, a novel swine-associated (H1N1) influenza virus infection was reported to the U.S. Centers for Disease Control and Prevention (CDC). The child, who was in contact with pigs, recovered uneventfully, and the case was barely mentioned in the April 17, 2009 edition of the Morbidity and Mortality Weekly Report [1]. However, note was made the next week of two cases of influenza A (H1N1) virus infection [2]; both were in children who had no history of contact with pigs. The two viruses were genetically similar and substantially different from prior H1N1 strains. The lack of contact with pigs and the novelty of the strain raised concern about human-to-human transmission of a virus to which there was no large-scale immunity. By the next week, 64 confirmed cases were reported by the CDC [3], and the World Health Organization (WHO) described 26 confirmed cases from Mexico. On April 29, 2009, the WHO upgraded its level of pandemic alert from phase 4 to phase 5, indicating humanto-human spread in at least two countries in one region [4]. By May 5, Mexico had identified almost 12,000 suspected cases with 42 deaths [4]. As the pandemic progressed, more reports Division of Acute Care Surgery, University of Michigan, Ann Arbor, Michigan. SURGICAL INFECTIONS Volume 12, Number 2, 2011 a Mary Ann Liebert, Inc. DOI: 10.1089/sur.2010. 082