Virus-associated hemophagocytic syndrome as a major contributor to death in patients with 2009 influenza A (H1N1) infection (Critical Care)

IntroductionVirus-associated hemophagocytic syndrome (VAHS) is a severe complication of various viral infections often resulting in multi organ failure and death. The purpose of this study was to describe baseline characteristics, development of virus-associated hemophagocytic syndrome, related treatments and associated mortality rate of consecutive critically ill patients with confirmed 2009 influenza A (H1N1) infection and respiratory failure. Methods: To perform a prospective observational study of 25 critically ill patients with 2009 influenza A (H1N1) infection at a single center intensive care unit in Germany between October 5, 2009, and January 4, 2010. Demographic data, comorbidities, diagnosis of virus-associated hemophagocytic syndrome, illness progression, treatments, and survival data were collected. The primary outcome measure was the development of virus-associated hemophagocytic syndrome and related mortality. Secondary outcomes variables included duration of mechanical ventilation, support of extracorporeal membrane oxygenation, and duration of viral shedding. Results: Virus-associated hemophagocytic syndrome developed in nine out of 25 (36%) critically ill patients with confirmed 2009 influenza A (H1N1) infection; eight of them (89%) died. In contrast, the mortality rate in the remaining 16 patients without hemophagocytic syndrome was 25% (P=0.004 for the survival difference in patients with or without hemophagocytosis by log-rank analysis). Patients were young (median, 45 [IQR, 35 to 56] years), however 18 (72%) presented one or more risk factors for severe course of illness. All 25 patients received mechanical ventilation for severe acute respiratory distress syndrome and refractory hypoxemia with duration of mechanical ventilation of median (IQR) 19 (13 to 26) days and an additional 17 (68%) of whom required extracorporeal membrane oxygenation for median (IQR) 10 (6 to 19) days. Conclusions: Findings raise the possibility that VAHS may be a frequent complication of severe 2009 influenza A (H1N1) infection and represents an important contributor to multi organ failure and death in these patients.