Canadian Study: H1N1 Influenza May Overwhelm ICUs

November 2009

By Robert Finn
Elsevier Global Medical News 

Intensive care units could become overwhelmed if the pandemic influenza A(H1N1) virus spreads as widely as feared and progresses as rapidly as observed in a March-July 2009 outbreak in Canada, said Dr. Anand Kumar and colleagues in a study published online in the Journal of the American Medical Association and presented at a meeting of the European Society of Intensive Care Medicine in Vienna.

All beds in intensive care units in Winnipeg, Man., the site of the largest pandemic cohort, were occupied at the peak of the outbreak in June 2009, reported Dr. Kumar of St. Boniface General Hospital, Winnipeg. Among the 168 patients admitted to the ICU with confirmed or probable 2009 influenza A(H1N1), the average time from the onset of symptoms to hospitalization was 4 days, and the average time from hospitalization to ICU admission was 1 day. The average age of these patients was 32.3 years; 67% were female, and 30% were children.

The findings were based on prospective and retrospective data from 38 adult and pediatric intensive care units (JAMA 2009 Oct. 12 [doi:10.1001/jama.2009.1496]).

On the first day of ICU admission, 81% of the patients required mechanical ventilation and 33% required inotropes or vasopressors, often with high levels of sedatives to help them adapt to the ventilator.

The median stay in the ICU was 12 days, as was the median time on mechanical ventilation.

"If, as expected, the prevalence of 2009 influenza A(H1N1) infection increases with the upcoming flu season, there will be an acutely increased demand for ICU care, including the need for rescue therapies that are not currently widely available. Clinicians and policy makers will need to examine feasible methods to optimally expand and deploy ICU resources to meet this need," the researchers wrote.

In an accompanying editorial, Dr. Douglas B. White and Dr. Derek C. Angus of the University of Pittsburgh noted that many hospitals in the United States may not have enough physicians with expertise in the needed rescue therapies, and even those hospitals with expert physicians may not have the staffing structures in place that would allow timely treatment 24 hours a day (JAMA 2009 Oct. 12 [doi:10.1001/jama.2009.1539]).

Dr. White and Dr. Angus proposed that care could be regionalized, with a few hospitals accumulating experience managing the sickest patients. Telemedicine consultations between experts and physicians at outlying hospitals might help. Additionally, hospitals could make temporary staffing changes.

"Hospitals must develop explicit policies to equitably determine who will and will not receive life-support should absolute scarcity occur," Dr. White and Dr. Angus wrote. "Any deaths from 2009 influenza A(H1N1) will be regrettable, but those that result from insufficient planning and inadequate preparation will be especially tragic."

Within the first 28 days of critical illness, 24 of the 168 patients died. An additional five patients died within 90 days, for an overall mortality rate of 17%. Of the deaths, 72% occurred in females.

The "striking" female susceptibility to influenza has not previously been described, according to the researchers. Studies during other pandemics have found that pregnancy is a risk factor for infection, and this may provide a partial explanation.

Of the 50 children admitted to the ICU, 4 (8%) died.

Virtually all of the ICU patients (98%) had one or more comorbidities, and 30% had a major comorbidity. Chronic lung disease was present in 41%, obesity in 33% (morbid obesity in 24%), and hypertension in 24%.

None of the investigators reported any relevant financial conflicts. The Public Health Agency of Canada, the Ontario Ministry of Health and Long-Term Care, the Heart and Stroke Foundation Canada, and the Canadian Institutes of Health Research provided support for the Canadian study. Dr. White received grant funding from the Greenwald Foundation and from the National Institute on Aging's Beeson Physician Faculty Scholars Program.


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