Epidemiological features of influenza in Canadian adult intensive care unit patients

Abstract

SUMMARYTo identify predictive factors and mortality of patients with influenza admitted to intensive care units (ICU) we carried out a prospective cohort study of patients hospitalized with laboratory-confirmed influenza in adult ICUs in a network of Canadian hospitals between 2006 and 2012. There were 626 influenza-positive patients admitted to ICUs over the six influenza seasons, representing 17·9% of hospitalized influenza patients, 3·1/10 000 hospital admissions. Variability occurred in admission rate and proportion of hospital influenza patients who were admitted to ICUs (proportion range by year: 11·7–29·4%; 21·3% in the 2009–2010 pandemic). In logistic regression models ICU patients were younger during the pandemic and post-pandemic period, and more likely to be obese than hospital non-ICU patients. Influenza B accounted for 14·2% of all ICU cases and had a similar ICU admission rate as influenza A. Influenza-related mortality was 17·8% in ICU patients compared to 2·0% in non-ICU patients.

Influenza-mediated reduction of lung epithelial ion channel activity leads to dysregulated pulmonary fluid homeostasis

“…The mucosal barrier of the conducting airways and integrity of the alveolar blood-gas exchange barrier are central to the sequelae of severe IAV infections, and investigations into the molecular mechanisms are urgently needed. Maintenance of the pulmonary mucosal barrier and gas exchange unit are critically dependent on intricate regulation of Na + absorption and Cland HCO 3 secretion via the ENaC and CFTR channels, respectively (reviewed in ref. 13).…”

“…Acquired respiratory distress syndrome (ARDS) secondary to lower respiratory tract infections, particularly to viruses, remains a serious clinical outcome following infection. Upward of 10% of admissions to intensive care settings during the typical influenza (IAV) season are for pneumonia or ARDS requiring respiratory support (1)(2)(3). Viral-mediated pneumonia is recognized across most common respiratory viral infections, and with the lack of broad-spectrum antiviral therapies, treatment is largely supportive and nonspecific.…”

“…Proper lung function requires a hydrated airway epithelium to facilitate mucociliary clearance and conductance of air, while the alveolar epithelium must be essentially devoid of water for oxygen to diffuse efficiently for gas exchange. Pulmonary fluid regulation is mediated by a complex interplay of epithelial tight junctions and secretion and reabsorption of transcellular ions, such as Na + , Cl -, HCO 3 -, and K + , to which water travels passively along osmotic gradients (4)(5)(6). These ions move passively through channels and transporters, down a favorable electrochemical gradient established by the energy-consuming, ouabain-sensitive, Na,K-ATPase located in the basolateral surface (5).…”

Diagnosis of severe respiratory infections in immunocompromised patients

“…Allogeneic HSCT recipients are at particularly high risk of death from CARV infection [54]. Among immunocompromised patients with the most severe forms of influenza, one-third requires ICU admission and mechanical ventilation and one-fifth have a fatal outcome [66].…”

Influenza virus-related critical illness: prevention, diagnosis, treatment

“…A Southern Hemisphere study reported influenza VE of 82% in reducing influenza-associated ICU admissions among adults [43] while a study in Spain showed an adjusted influenza VE of 23% in preventing ICU admission and death [44]. Despite the benefits of influenza vaccination, there continues to be low vaccine coverage among adults admitted to the ICU who often have a high prevalence of high-risk comorbidities [45,46]. In children, low influenza vaccination coverage has also been reported among those admitted to pediatric ICUs, even among those with underlying high-risk conditions [47].…”