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Published on: April 4, 2011
Critically ill patients with 2009 influenza A(H1N1) infection in Canada
Anand Kumar1, Ryan Zarychanski, Ruxandra Pinto
1Section of Critical Care Medicine, Health Sciences Centre, JJ 399, 700 William Ave, Winnipeg, MB R3E-0Z3 Canada. akumar61@yahoo.com
Insights
Critically ill patients with 2009 influenza A(H1N1) in Canada experienced rapid disease progression, severe hypoxemia, and organ failure. Outcomes included prolonged mechanical ventilation and significant mortality, highlighting the need for intensive care.
Area of Science:
- Infectious Diseases
- Critical Care Medicine
- Epidemiology
Background:
- The 2009 influenza A(H1N1) pandemic saw a significant number of cases in North America.
- Understanding the characteristics of critically ill patients is crucial for managing severe influenza infections.
Purpose of the Study:
- To characterize critically ill patients with 2009 influenza A(H1N1) in Canada.
- To describe their treatment and outcomes, including mortality and resource utilization.
Main Methods:
- Prospective observational study of 168 critically ill patients with confirmed or probable 2009 influenza A(H1N1).
- Data collected from 38 Canadian adult and pediatric intensive care units (ICUs).
- Primary outcomes: 28-day and 90-day mortality; Secondary outcomes: mechanical ventilation and ICU stay duration.
Main Results:
- The study included young adults and children, with a high proportion of females and Aboriginal Canadians.
- Patients presented with rapid critical illness, severe hypoxemia, and frequent multisystem organ failure.
- High rates of mechanical ventilation (81.0%) and prolonged ICU stays (median 12 days) were observed, along with frequent use of rescue therapies.
Conclusions:
- Critical illness from 2009 influenza A(H1N1) developed quickly, affecting young individuals.
- Severe hypoxemia, organ failure, and prolonged mechanical ventilation were common, necessitating intensive care interventions.
Context:
Between March and July 2009, the largest number of confirmed cases of 2009 influenza A(H1N1) infection occurred in North America.
Objective:
To describe characteristics, treatment, and outcomes of critically ill patients in Canada with 2009 influenza A(H1N1) infection.
Design, Setting, And Patients:
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.
Main Outcome Measures:
The primary outcome measures were 28-day and 90-day mortality. Secondary outcomes included frequency and duration of mechanical ventilation and duration of ICU stay.
Results:
Critical illness occurred in 215 patients with confirmed (n = 162), probable (n = 6), or suspected (n = 47) community-acquired 2009 influenza A(H1N1) infection. Among the 168 patients with confirmed or probable 2009 influenza A(H1N1), the mean (SD) age was 32.3 (21.4) years; 113 were female (67.3%) and 50 were children (29.8%). Overall mortality among critically ill patients at 28 days was 14.3% (95% confidence interval, 9.5%-20.7%). There were 43 patients who were aboriginal Canadians (25.6%). The median time from symptom onset to hospital admission was 4 days (interquartile range [IQR], 2-7 days) and from hospitalization to ICU admission was 1 day (IQR, 0-2 days). Shock and nonpulmonary acute organ dysfunction was common (Sequential Organ Failure Assessment mean [SD] score of 6.8 [3.6] on day 1). Neuraminidase inhibitors were administered to 152 patients (90.5%). All patients were severely hypoxemic (mean [SD] ratio of Pao(2) to fraction of inspired oxygen [Fio(2)] of 147 [128] mm Hg) at ICU admission. Mechanical ventilation was received by 136 patients (81.0%). The median duration of ventilation was 12 days (IQR, 6-20 days) and ICU stay was 12 days (IQR, 5-20 days). Lung rescue therapies included neuromuscular blockade (28% of patients), inhaled nitric oxide (13.7%), high-frequency oscillatory ventilation (11.9%), extracorporeal membrane oxygenation (4.2%), and prone positioning ventilation (3.0%). Overall mortality among critically ill patients at 90 days was 17.3% (95% confidence interval, 12.0%-24.0%; n = 29).
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.
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