Abstract
IntroductionInfluenza is easily overlooked in intensive care units (ICUs), particularly in patients with alternative causes of respiratory failure or in those who acquire influenza during their ICU stay.MethodsWe performed a prospective study of patients admitted to three adult ICUs of our hospital from December 2010 to February 2011. All tracheal aspirate (TA) samples sent to the microbiology department were systematically screened for influenza. We defined influenza as unsuspected if testing was not requested and the patient was not receiving empirical antiviral therapy after sample collection.ResultsWe received TA samples from 105 patients. Influenza was detected in 31 patients and was classified as unsuspected in 15 (48.4%) patients, and as hospital acquired in 13 (42%) patients. Suspected and unsuspected cases were compared, and significant differences were found for age (53 versus 69 median years), severe respiratory failure (68.8% versus 20%), surgery (6.3% versus 60%), median days of ICU stay before diagnosis (1 versus 4), nosocomial infection (18.8% versus 66.7%), cough (93.8% versus 53.3%), localized infiltrate on chest radiograph (6.3% versus 40%), median days to antiviral treatment (2 versus 9), pneumonia (93.8% versus 53.3%), and acute respiratory distress syndrome (75% versus 26.7%). Multivariate analysis showed admission to the surgical ICU (odds ratio (OR), 37.1; 95% confidence interval (CI), 2.1 to 666.6; P = 0.01) and localized infiltrate on chest radiograph (OR, 27.8; 95% CI, 1.3 to 584.1; P = 0.03) to be independent risk factors for unsuspected influenza. Overall mortality at 30 days was 29%. ICU admission for severe respiratory failure was an independent risk factor for poor outcome.ConclusionDuring the influenza season, almost one third of critical patients with suspected lower respiratory tract infection had influenza, and in 48.4%, the influenza was unsuspected. Lower respiratory samples from adult ICUs should be systematically screened for influenza during seasonal epidemics.
Highlights
Influenza is overlooked in intensive care units (ICUs), in patients with alternative causes of respiratory failure or in those who acquire influenza during their ICU stay
Our objectives were to determine the incidence of influenza among adult ICU patients with a tracheal aspirate (TA) sample obtained during the influenza season, and to demonstrate the frequency of unsuspected cases and the rate of hospital-acquired episodes
During the study period, 618 patients were admitted to our adult ICUs
Summary
Influenza is overlooked in intensive care units (ICUs), in patients with alternative causes of respiratory failure or in those who acquire influenza during their ICU stay. Influenza is a common cause of admission to the intensive care unit (ICU) during the influenza season and influenza pandemics [1,2,3,4]. It may be overlooked, in patients with clinical manifestations that can be explained by alternative infectious or noninfectious causes [5]. Influenza may not be suspected when respiratory function deteriorates or fails in patients already admitted to the ICU.
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