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October 12, 2009

Journal of the American Medical Association Studies of H1N1 (swine) flu deaths in Canada and Mexico

Journal of American Medical Association published study of people who die from H1N1 in Canada

Key Takeaways:
* Get into the hospital before you get supersick from flu and your organs start showing problems
* Unlike regular flu where the very young and very old are at more risk, H1N1 is hitting harder those who are 10-60 years of age.
* Those 60 and over seem to have some immunity. Pre-1949, apparently some virus went around that was similar. This further indicates that it is a good idea to get the H1N1 vaccination when they are widely available
* The rate of hospitalization and death is higher than a regular flu season.
* Key symptoms are fever and respiratory problems (flu symptoms and trouble/difficulty breathing means go to the hospital)

From the Wall Street Journal, Anand Kumar, lead author of one of the studies and ICU attending physician for the Winnipeg Regional Health Authority in Canada. "There's almost two diseases. Patients are either mildly ill or critically ill and require aggressive ICU care. There isn't that much of a middle ground." About 3.9% of total reported cases of flu for the period in Canada had people who became extremely ill.

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


So if you get really, really sick then if you are at a good hospital and have machines doing your breathing, you can be supported through the critical phase of the illness where you would have died otherwise. (If there was nothing else wrong with you and were healthy otherwise)

Between March and July 2009, the largest number of confirmed cases of 2009 influenza A(H1N1) infection occurred in North America. A prospective observational study of 168 critically ill patients with 2009 influenza A(H1N1) infection in 38 adult and pediatric intensive care units (ICUs) in Canada between April 16 and August 12, 2009. Conclusion Critical illness due to 2009 influenza A(H1N1) in Canada occurred rapidly after hospital admission, often in young adults, and was associated with severe hypoxemia, multisystem organ failure, a requirement for prolonged mechanical ventilation, and the frequent use of rescue therapies.

Patients who died were more likely to have higher severity of illness at presentation and greater organ dysfunction. Although this overall population was young, older patients were more likely to die. Because nearly all patients received early treatment with neuraminidase inhibitors, we were unable to investigate differences in outcome due to treatment or timing of these agents

The spring outbreak of 2009 influenza A(H1N1) infection in Canada affected primarily young, female, and aboriginal patients without major comorbidities, and conferred a 28-day mortality of 14.3% among critically ill patients. A history of lung disease or smoking, obesity, hypertension, and diabetes were the most common comorbidities. 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.


Journal of American Medical Association published study of people who die from H1N1 in Mexico.

On April 21, 2009, the Centers for Disease Control and Prevention reported the detection of 2 cases of human infection with 2009 influenza A(H1N1) in California. The greatest initial burden of critical illness and death occurred in Mexico between March 18, 2009, and June 1, 2009, with 5029 cases and 97 documented deaths. By August 30, 2009, there were more than 116 046 cases with 2234 deaths in the Americas and 277 607 documented cases and at least 3205 deaths worldwide. A regular flu season has about 30,000 deaths in the United States. From Sept, 2009 to Mar 2010 is when the higher flu season normally occurs. April to late August is not flu season.



Our analysis of critically ill patients with 2009 influenza A(H1N1) reveals that this disease affected a young patient group. Fever and respiratory symptoms were harbingers of disease in almost all cases. There was a relatively long period of illness prior to presentation to the hospital, followed by a short period of acute and severe respiratory deterioration. These patients had severe hypoxia and acute respiratory distress syndrome and required high FIO2, PEEP, and ventilatory pressures. Within 60 days, 41% of critically ill patients had died.

The mortality rate of 41% for 2009 influenza A(H1N1)–associated critical illness is not dissimilar to that for acute respiratory distress syndrome resulting from other influenza but is higher than that for severe acute respiratory syndrome (SARS), and deaths in Mexico appear to have been more directly related to respiratory rather than multiorgan failure.20-22 The low median age and relatively good prior health of this critically ill group are different from those for seasonal influenza and SARS,22 in which older patients appear more susceptible to severe disease.

Although serologic studies suggest that 2009 influenza A(H1N1) is a novel influenza strain with little protection afforded by seasonal influenza vaccination, adults older than 60 years appear to have some preexisting immunity to this novel virus


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