Critical care services and 2009 H1N1 influenza in Australia and New Zealand.

Cynthia Farquhar

Cynthia Farquhar

Cynthia Farquhar

+ -1 Evaluators

Australia and New Zealand had eight times the incidence of H1N1 virus infection than the Northern Hemisphere in the months of June to August 2009. There was a substantial impact on intensive care services from the H1N1 influenza in Australia and New Zealand over three winter months in 2009. This paper gives some insight into which patients are at risk and will aid in planning critical care services in the Northern Hemisphere. The majority of patients admitted to intensive care were adults younger than 65 years, and 9.1% were pregnant (pregnant women represent approximately 1% of the general population). A total of 28% had a body mass index (BMI) >35; 32% of the patients had asthma or another chronic pulmonary disease. Indigenous people (aboriginal or Maori) were also over-represented in the group who were admitted. Of the 722 admitted patients with confirmed H1N1 infection, 14% died. Overall, only one-third did not have any predisposing factors. Either viral or bacterial pneumonia was present in almost 70% of the patients. Death was found to be independently associated with the requirement for invasive ventilation, any co-existing condition and older age.

Willem J Wiersinga

Willem J Wiersinga

Willem J Wiersinga

Gavin Koh

Gavin Koh

Gavin Koh

+ 0 Evaluators

This report on the impact of influenza A (H1N1) 2009 on intensive care services during the winter in Australia and New Zealand demonstrates the significant burden on intensive care units (ICUs) and can assist planning for the upcoming winter influenza season in the Northern hemisphere. In this epidemiological survey, investigators from the Australian and New Zealand intensive care study group (ANZIC) evaluated the morbidity and mortality of 722 patients who were confirmed to have pandemic H1N1 influenza and were admitted to one of 187 ICUs. The following risk factors were identified: of the patients admitted to ICU, 9% were pregnant, 29% had a body mass index >/=35 and most admissions were in the age groups <1 year and between 25 to 65 years. The overall mortality was 14%. The median duration of ICU treatment was 7 days and 2/3 of ICU admitted patients required mechanical ventilation. As pointed out in the accompanying editorial, the great asset of this study is its usefulness in anticipating the intensive care capacity that is likely needed in the first 4 weeks (most influenza epidemics peak after about 4 weeks) of the anticipated second wave of the H1N1 influenza epidemic {1}. The following are numbers of key surge capacity needed for the treatment of H1N1 influenza patients on ICUs which can be easily extrapolated to the situation in countries in the Northern hemisphere in numbers per million inhabitants: 28.7 admissions to ICUs, 350 bed days in ICUs, 208 mechanical ventilation days in ICUs and 2.1 episodes of extracorporeal membrane oxygenation (ECMO) in ICUs {1}. These numbers indicate that the H1N1 influenza epidemic can cause a severe burden on intensive care resources -- the peak percentage of ICU beds occupied by patients with 2009 H1N1 influenza in the current study ranged from 8.9 to 19.0% -- but, at the same time, circumspectly seem to indicate that, currently, with appropriate planning, the 2009 H1N1 influenza epidemic will be manageable. Lastly, this study by the ANZIC study group further underscores the importance of research networks in tackling important and timely biomedical questions. On the SEPSIS 2009 conference in Amsterdam, where the current study was also presented, John Marshall, past chair of the International Sepsis Forum, advocated critical care physicians to join a global collaboration of ICU clinicians committed to improving the care of patients with severe H1N1 infection. This recent initiative, which is named International Forum for Acute Care Trialists (InFACT), has launched a comprehensive research program consisting of a global clinical registry, clinical trials of widely available interventions that might minimize the sequelae of severe H1N1 infection, a biobank to characterize genetic risk factors of severe infection and an initiative to attenuate severe H1N1 disease in the developing world where its toll will be greatest (InFACT).