Study confirms swine flu saw skyrocketing ICU admissions

1 April 2010

Last winter’s pandemic flu saw intensive care admissions for acute respiratory distress skyrocket to 15 times higher than previous years, a study has confirmed.

The average winter admissions for viral pneumonitis in Australasian ICUs is 57 patients, but pandemic swine flu saw 15 times this number admitted last winter.

A full analysis of the 722 patients with confirmed pandemic H1N1 flu in ICUs last winter was published in the New England Journal of Medicine late last year.

The Australian and New Zealand Intensive Care (ANZIC) study was a collaborative project involving data gathered by clinicians at Australasia’s intensive care units from June 1 to August 31, 2009.

In all 856 flu patients were admitted to the ICUs last winter, with 722 confirmed to have the pandemic H1N1 strain. About two-thirds of them needed mechanical ventilation.

Unlike seasonal flu the highest number of ICU admissions were amongst patients 25-49 years of age and infants.

Disproportionately represented were adults with a BMI over 35 (about 28.5 per cent) and while pregnant woman make up about one per cent of the population they made up nine per cent of admissions.

Also disproportionately represented were adults with asthma or other chronic pulmonary disease (about 33%) and Māori, who make up about 14 per cent of population but made up 25 per cent of admissions.

But nearly a third of patients (32%) were young or middle-aged adults who were not pregnant and didn’t have any other known condition or pre-disposing factor.

About two-thirds of the pandemic swine flu patients had to be mechanically ventilated while in ICU for an average of about eight days. Overall, patients spent an average of about 7.5 days in ICU and just over 12 days in hospital.

The proportion of patients who died in hospital (16%) was no higher than with seasonal influenza but, unlike seasonal flu admissions, which are mostly elderly people with co-existing conditions, the higher number of younger people admitted for pandemic flu meant the majority of deaths occurred in younger patients.

The maximum number of ICU beds occupied by pandemic flu patients was 7.4 beds per million inhabitants in late July. The data indicates the greatest impact on ICU in a region is about four to six weeks after the first confirmed winter ICU admission, and the extra workload would last several weeks.



93% under 65 years

9% pregnant

28.5% BMI over 35

33% asthma or other chronic pulmonary disease

25% Māori

32% no known predisposing factor

65% on mechanical ventilators

16% died

*Based on data gathered on pandemic H1N1 patients admitted to Australian or NZ ICUs in June to August 2009.