CANADA: H1N1 critical illness can occur rapidly; predominantly affects young patients

12.oct.09
JAMA and Archives Journal
Heidi Graham

Critical illness among Canadian patients with 2009 influenza A(H1N1)
occurred rapidly after hospital admission, often in young adults, and
was associated with severely low levels of oxygen in the blood,
multi-system organ failure, a need for prolonged mechanical ventilation,
and frequent use of rescue therapies, according to a study to appear in
the November 4 issue of JAMA. This study is being published early online
to coincide with its presentation at a meeting of the European Society
of Intensive Care Medicine.
Infection with the 2009 influenza A(H1N1) virus has been reported in
virtually every country in the world. The World Health Organization
declared the first phase six (phase indicating widespread human
infection) global influenza pandemic of the century on June 11, 2009.
The largest number of confirmed cases occurred in North America between
March and July 2009, according to background information in the article.
Anand Kumar, M.D., of the Health Sciences Centre and St. Boniface
Hospital, Winnipeg, Manitoba, Canada, and colleagues with the Canadian
Critical Care Trials Group H1N1 Collaborative conducted an observational
study of critically ill patients with 2009 influenza A(H1N1) in 38 adult
and pediatric intensive care units (ICUs) in Canada between April 16 and
August 12, 2009. The study focused on the death rate at 28 and 90 days,
as well as the frequency and duration of mechanical ventilation and the
duration of ICU stay.
The researchers found that a total of 168 patients had confirmed or
probable 2009 influenza A(H1N1) infection and became critically ill
during this time period, and 24 (14.3 percent) died within the first 28
days from the onset of critical illness. Five more patients died within
90 days. The average age of the patients with confirmed or probable 2009
influenza A(H1N1) was 32.3 years, 113 were female (67.3 percent), and 50
were children (29.8 percent).
"Our data suggest that severe disease and mortality in the current
outbreak is concentrated in relatively healthy adolescents and adults
between the ages of 10 and 60 years, a pattern reminiscent of the
W-shaped curve [rise and fall in the population mortality rate for the
disease, corresponding to age at death] previously seen only during the
1918 H1N1 Spanish pandemic," the authors write.
Patients with 2009 influenza A(H1N1) infection-related critical illness
experienced symptoms for a median (midpoint) of four days before
entering the hospital, but worsened rapidly and required care in the ICU
within one or two days. Shock and multi-system organ failure were
common, and 136 patients (81 percent) received mechanical ventilation,
with the median duration being 12 days. The average ICU stay was 12
days. Lung rescue therapies included neuromuscular blockade, inhaled
nitric oxide and high-frequency oscillatory ventilation.
"In conclusion, we have demonstrated that 2009 influenza A(H1N1)
infection-related critical illness predominantly affects young patients
with few major comorbidities and is associated with severe hypoxemic
respiratory failure, often requiring prolonged mechanical ventilation
and rescue therapies," the authors write. "With such therapy, we found
that most patients can be supported through their critical illness."
(JAMA. 2009;302(17):doi:10.1001/jama.2009.1496). Available pre-embargo
to the media at www.jamamedia.org)
Editor's Note: Please see the article for additional information,
including other authors, author contributions and affiliations,
financial disclosures, funding and support, etc.
Editorial: Preparing for the Sickest Patients With 2009 Influenza
A(H1N1)
In an accompanying editorial, Douglas B. White, M.D., M.A.S., and JAMA
Contributing Editor Derek C. Angus, M.D., M.P.H., of the University of
Pittsburgh School of Medicine, write that many U.S. hospitals may not
have adequate numbers of physicians or staffing structures to facilitate
timely treatment of the most seriously ill patients with 2009 influenza
A(H1N1).
"Hospitals must develop explicit policies to equitably determine who
will and will not receive life support should absolute scarcity occur,"
they write. "Any deaths from 2009 influenza A(H1N1) will be regrettable,
but those that result from insufficient planning and inadequate
preparation will be especially tragic," they conclude.
(JAMA. 2009;302(17):doi:10.1001/jama.2009.1539). Available pre-embargo
to the media at www.jamamedia.org)