Complications and outcome of patients with severe influenza infection admitted to intensive care unit

INTRODUCTION. Seasonal influenza epidemic constitutes a global health problem with serious complications leading to high morbidity and mortality, particularly among elderly patients and patients with chronic underlying conditions According to WHO, the most effective way to prevent the disease is annual vaccination. OBJECTIVES. To evaluate the complications and outcome of patients with confirmed influenza infection requiring admission to the intensive care unit during 2018-2019 flu season in a tertiary hospital in Greece. We also investigated factors associated with poor prognosis. METHODS. This is a retrospective observational study that included all patients admitted to the ICU of a tertiary hospital for complicated influenza infection, between October 1st 2018 and April 10th 2019. Demographic variables, clinical features, comorbidities, complications and ICU outcome were reviewed. RESULTS. A total of 15 patients were included with a median age of 68 (range 49-87) years. Nine of them (60%) were male. Eleven patients (73%) were infected with influenza A and four patients (27%) with influenza B. 46,6% of the patients (n=7) were vaccinated against influenza. Median length of ICU stay was 17 days (range 4-37) and the ICU mortality rate was 33% (n=5). The median APACHE II score on admission was 25 (range 21-38). The most common underlying diseases of the patients were chronic obstructive pulmonary disease (53%), diabetes mellitus (47%) and coronary artery disease (20%). 60% were smokers and 33% were immunosuppressed (Rheumatoid Arthritis, Chronic Lymphocytic Leukemia, Multiple Sclerosis, Sarcoidosis). The majority of patients presented bacterial superinfections- 40% (n=6) ventilator associated tracheobronchitis or pneumonia and 13% (n=2) secondary bacteremia. More frequent complications were acute kidney injury (AKI) in 8 patients (53%) requiring CRRT in one third of the cases, acute heart failure (n=5, 33%), and rhabdomyolysis (n=5, 33%). Less frequent complications were myopathy/neuropathy (20%), ARDS (13%), encephalitis (7%), pulmonary embolism/DVT (7%), and invasive aspergillosis (7%). Compared with survivors, nonsurvivors were older (median age 71 vs 63,5), had longer ICU stay (median 26 days vs 13,5d), higher APACHE II score (median 30 vs 26), suffered more infectious complications (80% vs 30%), more cardiac complications (80% vs 20%), and presented AKI in 100% of the cases (vs 30% of survivors). Among survivors 40% (n=4) were vaccinated, and 60% (n=3) among non-survivors. CONCLUSION. Findings from our single center study suggest that patients requiring intensive care management during the recent influenza outbreak, in contrast with previous years, suffered less ARDS and more extra-pulmonary complications. Although our study population is limited, and we cannot extrapolate conclusions, it seems that vaccination did not protect against multiple organ failure and fatal outcomes.