INFLUENZA PANDEMIC (H1N1) 2009 (69): CASE MANAGEMENT
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In this update:
[1] ECMO (Australia and New Zealand)
[2] Canadian experience

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[1] ECMO (Australia and New Zealand)
Date: Tue 13 Oct 2009
Source: ABC Science [edited]
<http://www.abc.net.au/science/articles/2009/10/13/2711206.htm>


Oxygen treatment key to swine flu survival
------------------------------------------
A new Australian and New Zealand study, published in today's edition of the 
Journal of the American Medical Association [JAMA], found that 79 per cent 
of swine flu patients treated with extracorporeal membrane oxygenation 
(ECMO) survived. Intensive care specialist Dr Daryl Jones of Monash 
University in Melbourne, says ECMO is an artificial heart and lung machine. 
It takes the blood out of the body, removes the carbon dioxide and replaces 
it with oxygen and then sends the blood back in and around the body, he says.

The study collected data on swine flu [influenza pandemic (H1N1) 2009 virus 
infection] patients from all 15 centres that offer ECMO treatment in 
Australia and New Zealand. Of the 5000 people infected with swine flu in 
Australia and New Zealand that needed hospitalisation, 61 required 
treatment with ECMO, he says. Jones says that's a significant increase on 
the amount of people who've required ECMO in the past. "Last year only 4 
patients across Australia and New Zealand required ECMO during winter."

Jones says that, unlike seasonal influenza, swine flu has affected many 
young adults. "A substantial number of young people became very sick with 
pneumonia [due to] the virus or a secondary infection," he says. According 
to Jones, when patients become very short of breath and have respiratory 
failure, they're put on a ventilator. If that doesn't work, ECMO treatment 
is the last resort.

Paediatrician Professor Robert Booy, of the Children's Hospital at Westmead 
in Sydney, says patients that require ECMO are "extremely unwell and 
teetering on death". Of the 61 swine flu patients treated with ECMO, 79 per 
cent survived, which Booy says is "very impressive". Without ECMO, about 90 
per cent of people suffering from severe influenza associated respiratory 
failure would have died, he says. But Booy says the current swine flu death 
rate statistics in Australia are "hiding" those saved from intensive care 
management. "When we say we've had just under 200 deaths, the numbers could 
easily have been twice that, but for the fact we've got such high quality 
intensive care in Australia and New Zealand."

Booy says the study is extremely important, and demonstrates that intensive 
care doctors across Australia and New Zealand have a "superb" network, 
which allows them to publish important research quickly. Jones admits the 
study was unable to determine the survival rate of those with severe 
respiratory failure associated with swine flu who did not receive ECMO 
treatment.

He says Australian clinicians were "forewarned" of what to expect before 
swine flue arrived in Australia, by the experiences of doctors in Mexico 
and the US. When the outbreak of swine flu was announced in Mexico, he says 
a lot of young people were presenting with severe pneumonia. "They also 
reported a very high fatality rate per case of infection." Jones hopes 
their study will be of similar value to the Northern Hemisphere who have 
yet to experience swine flu outbreaks during winter. "Given what we learned 
from the Mexican experience, we felt we had an obligation to reciprocally 
provide advanced warning for people in the north."

An editorial also published in the latest edition of JAMA written by Dr 
Douglas White and Dr Derek Angus, both of the University of Pittsburgh, 
says any deaths from swine flu will be regrettable. "But those that result 
from insufficient planning and inadequate preparation will be especially 
tragic."

-- 
communicated by:
ProMED-mail rapporteur Mary Marshall

[The interactive HealthMap/ProMED map of Australia is available at 
<http://healthmap.org/r/00cS>. The interactive HealthMap/ProMED map of New 
Zealand is available at <http://healthmap.org/r/00c3> - CopyEd.EJP]

******
[2] Canadian experience
Date: Mon 12 Oct 2009
Source: CBC Health [edited]
<http://www.cbc.ca/health/story/2009/10/12/h1n1-virus-infection-females-young-aboriginals-study.html>


Severe H1N1 infection in females "striking"
-------------------------------------------
Many of the Canadians who died or were sent to hospital earlier this year 
[2009] with H1N1 virus [influenza pandemic (H1N1) 2009 virus] were young 
adults, female and aboriginal, a new study suggests. The study, published 
in Monday's online issue of JAMA, looked at 168 patients with confirmed or 
probable swine flu. Of the group, 24 or 14.3 per cent, died within the 
first 28 days of becoming critically ill, Dr Anand Kumar, an intensive care 
specialist at the Health Sciences Centre and St. Boniface Hospital in 
Winnipeg and his colleagues found. "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," the study's 
authors wrote. The ages in the mortality pattern were similar to that of 
the 1918 H1N1 Spanish flu pandemic, they said.

-- 
communicated by:
ProMED-mail rapporteur Mary Marshall

[To put thee findings in perspective the commentary of the authors of the 
JAMA paper referred to above 
(<http://jama.ama-assn.org/cgi/content/full/2009.1496>) is reproduced 
below. - Mod.CP

"The spring outbreak of influenza A(H1N1) 2009 virus infection in Canada 
affected primarily young, female, and aboriginal patients without major 
co-morbidities, and conferred a 28-day mortality of 14.3 per cent among 
critically ill patients. A history of lung disease or smoking, obesity, 
hypertension, and diabetes were the most common co-morbidities. Critical 
illness occurred rapidly after hospital admission and was associated with 
severe oxygenation failure, a requirement for prolonged mechanical 
ventilation, and the frequent use of rescue therapies.

"We identified unusual features of severe disease in the current pandemic 
compared with most previous well-characterized pandemics, including the 
(probable) H2N2 1890 Russian influenza pandemic, the H2N2 1957 Asian 
influenza pandemic, and the H3N2 1968 Hong Kong pandemic. In these previous 
influenza pandemics, an increased predilection for infection among children 
and young adults has been documented, although mortality curves were 
U-shaped with increased deaths in the very young and the aged.

"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 
previously seen only during the 1918 H1N1 Spanish pandemic. Few patients 
older than 60 years in this study were admitted to the ICU. A potential 
biological basis for this observation is that patients in this age group 
have a cross-reactive antibody to 2009 influenza A (H1N1) at much higher 
rates than younger patients.

"The increased fraction of the aboriginal community presenting with severe 
influenza A (H1N1) 2009 infection is notable but not unique. This finding 
is reflected in the history of the 1918 H1N1 Spanish influenza pandemic 
during which mortality in aboriginal communities in North America (3 per 
cent to 9 per cent) was many times higher than nonaboriginal communities 
(generally <0.75 per cent). In 1918, mortality within Alaskan and Labrador 
Inuit populations was 30 per cent to 90 per cent. Although mortality was 
not substantially greater among aboriginal Canadians in this report, the 
number of patients with severe disease and knowledge of prior illness 
patterns in this community is cause for concern.

"The tendency of females to develop severe influenza A(H1N1) 2009 virus 
infection in this series is striking. A general female susceptibility has 
not been observed in other influenza case series of variable severity 
including the initial reports of influenza A (H1N1) 2009 virus infections. 
In most infectious diseases and related conditions such as sepsis and 
septic shock, males represent a larger proportion of cases and have a 
higher mortality. The explanation for increased risk of severe disease and 
death among females in this report is unclear but the role of pregnancy as 
a risk factor has been noted in previous influenza pandemics.

"The most common comorbidities among critically ill patients in our study 
were lung disease, obesity, hypertension, and a history of smoking or 
diabetes, each occurring in 30 per cent to 40 per cent of patients. All 
these conditions are known to be increased in frequency in the aboriginal 
population that comprises a substantial portion of cases within this 
cohort. The extent to which these comorbidities contribute to severity of 
disease is unclear because a large portion of the aboriginal population 
(which may be a risk factor itself on the basis of genetic susceptibility) 
often have such comorbidities.

"Among critically ill patients, obesity has been shown to be a risk factor 
for increased morbidity, but not consistently with mortality. The 
association of obesity with severe influenza A(H1N1) 2009 virus infection 
has been reported by others and may be a novel finding of this pandemic; 
however, even though obesity was more common in our series than in the 
general Canadian population (33 per cent versus approximately 24 per cent), 
we did not find a significant difference in BMI [body mass index] between 
survivors and nonsurvivors.

"Critically ill patients with diabetes and hyperglycemia also are known to 
be at increased risk of complications and death; similarly, alcohol abuse, 
which is known to be a risk factor for acute respiratory distress syndrome, 
may have been a risk factor some patients in our series. These 
relationships also have been reported with seasonal influenza. The relative 
absence of serious co-morbidities emphasizes that young, relatively healthy 
adults were the primary population affected by severe influenza A(H1N1) 
2009 infection during this outbreak.

"Patients with influenza A (H1N1) 2009 virus infection-related critical 
illness experienced symptoms for an average of 4 days prior to hospital 
presentation, but rapidly worsened and required care in the ICU within 1 to 
2 days. Apart from the usual symptoms seen in seasonal influenza, these 
cases stand out for the presence of gastrointestinal tract symptoms, 
dyspnea, purulent sputum production, and occasional frothy lung fluid on 
cough or endotracheal aspiration. Chest radiographs demonstrating bilateral 
mixed interstitial or alveolar infiltrates were found in three-quarters of 
the patients.

"Approximately one-third of patients required vasopressor support on day 1 
following ICU admission; however, in many cases this appeared temporally 
associated with the need for substantial sedation to optimize ventilation. 
Broad-spectrum antibacterial agents were initiated in almost all patients 
because of the initial suspicion of community-acquired bacterial pneumonia. 
However, actual bacterial lung infection was typically documented later in 
the course of critical illness.

"In addition, approximately one-third of patients in our cohort required 
advanced ventilatory support and rescue therapies for profound hypoxemic 
respiratory failure, including high levels of inspired oxygen and PEEP, 
pressure control, and airway pressure release ventilation, high-frequency 
oscillatory ventilation, prone positioning ventilation, neuromuscular 
blockade, inhaled nitric oxide, and extracorporeal membrane oxygenation 
[ECMO]. The fact that severe illness arises in a young, previously healthy 
population with a high probability of survival given the availability of 
appropriate resources has important societal implications.

"In Winnipeg, Manitoba, Canada, site of the largest pandemic cohort of 
patients, the capacity for the care of critically ill patients was 
seriously challenged at the outbreak peak in June with full occupancy of 
all regional ICU beds, similar to the 2002 Toronto, Ontario, Canada, 
experience with severe acute respiratory syndrome. If, as expected, the 
prevalence of influenza A (H1N1) 2009 virus 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.

"This study has a number of strengths. It represents the largest series of 
patients with severe influenza A (H1N1) 2009 infection yet described, and 
includes both adults and children from geographically and racially diverse 
settings across Canada, which improves the generalizability of our results 
to other regions. These observations of the epidemiological risk factors, 
typical clinical features, response to therapy, and prognosis should aid in 
the recognition, diagnosis, and clinical management of such infections. Our 
finding that patients can often be supported through 2009 influenza A 
(H1N1) infection­related critical illness with prolonged, aggressive life 
support, and the expectation that the number of cases will likely increase 
substantially over the next 6 months, highlight important potential 
limitations in critical care capacity.

"This study also has limitations. Our focus on severe disease requiring ICU 
admission may not reflect important presenting features in less severe 
cases. The ongoing deaths throughout the course of the study period suggest 
the possibility of late deaths after the observation period. This may 
result in a final hospital mortality rate that exceeds the mortality rate 
we are reporting. Although we describe cases in most regions of Canada, 
many were from an outbreak in a single province (Manitoba) and involved an 
aboriginal Canadian population near Winnipeg, which is Manitoba's largest 
city. This may lead to overrepresentation or underrepresentation of certain 
comorbidities and clinical features.

"In conclusion, we have demonstrated that 2009 influenza A(H1N1) 
infection­related 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. With such therapy, we found that most patients can be 
supported through their critical illness." - Mod.CP

The interactive HealthMap/ProMED map of Canada is available at 
<http://healthmap.org/r/007x> - CopyEd.EJP]

[see also:
Influenza pandemic (H1N1) 2009 (68): Viet Nam, virus clearance 20091011.3519
Influenza pandemic (H1N1) 2009 (67): vaccine delivery 20091011.3515
Influenza pandemic (H1N1) 2009 (66): case counts 20091010.3510
Influenza pandemic (H1N1) 2009 (65): update 20091009.3495
Influenza pandemic (H1N1) 2009 (64): Canada, vaccination update 20091005.3457
Influenza pandemic (H1N1) 2009 (63): USA military vaccine 20091002.3437
Influenza pandemic (H1N1) 2009 (62): Taiwan hosp cases 20091001.3421
Influenza pandemic (H1N1) 2009 (61): FLAARDS 20091001.3419
Influenza pandemic (H1N1) 2009 (60): bacterial coinfection 20090930.3410
Influenza pandemic (H1N1) 2009 (50): oseltamivir-resistance 20090917.3260
Influenza pandemic (H1N1) 2009 (40): global update 20090906.3138
Influenza pandemic (H1N1) 2009 (30): assumptions 20090813.2879
Influenza pandemic (H1N1) 2009 (20): Peru, 33 percent asymptomatic 
20090730.2668
Influenza pandemic (H1N1) 2009 (10): vaccine 20090720.2577
Influenza pandemic (H1N1) 2009 - Viet Nam: patient data 20090708.2450]

...................cp/ejp/sh



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