Critically ill patients with 2009 influenza A(H1N1) infection in Canada.
BACKGROUND
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.


METHODS
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.


METHODS
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).


CONCLUSIONS
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.
Kumar
Anand
A
Section of Critical Care Medicine, Health Sciences Centre, JJ 399, 700 William Ave, Winnipeg, MB R3E-0Z3 Canada. akumar61@yahoo.com
Zarychanski
Ryan
R
Pinto
Ruxandra
R
Cook
Deborah J
DJ
Marshall
John
J
Lacroix
Jacques
J
Stelfox
Tom
T
Bagshaw
Sean
S
Choong
Karen
K
Lamontagne
Francois
F
Turgeon
Alexis F
AF
Lapinsky
Stephen
S
Ahern
Stéphane P
SP
Smith
Orla
O
Siddiqui
Faisal
F
Jouvet
Philippe
P
Khwaja
Kosar
K
McIntyre
Lauralyn
L
Menon
Kusum
K
Hutchison
Jamie
J
Hornstein
David
D
Joffe
Ari
A
Lauzier
Francois
F
Singh
Jeffrey
J
Karachi
Tim
T
Wiebe
Kim
K
Olafson
Kendiss
K
Ramsey
Clare
C
Sharma
Sat
S
Dodek
Peter
P
Meade
Maureen
M
Hall
Richard
R
Fowler
Robert A
RA
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002170:Canada / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D016638:Critical Illness; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000209:etiology; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000150:complications / Q000175:diagnosis / Q000401:mortality / Q000628:therapy; D007362:Intensive Care Units; D053208:Kaplan-Meier Estimate; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D009102:Multiple Organ Failure / Q000209:etiology / Q000401:mortality; D011446:Prospective Studies; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000401:mortality; D055815:Young Adult