Outcomes among critically ill adults with influenza infection

Abstract

Background: Influenza infection is a major cause of mortality in critical care units. Methods: Data on critically ill adult patients with influenza infection from 2014 to 2019 were retrospectively collected, including mortality and critical care resource utilization. Independent predictors of mortality were identified using Cox regression. Results: One hundred thirty patients with confirmed influenza infection had a mean age of 56 (SD 16) years; 72 (55%) were male. Mean Acute Physiology and Chronic Health Evaluation (APACHE II) score was 22 (SD 9). One hundred eight (83%) patients had influenza A (46% H1N1pdm09, 33% H3N2); 21 (16%) had influenza B. Fifty-five (42%) patients had bacterial co-infection. Only 5 (4%) had fungal co-infection. One hundred eight (83%) patients required mechanical ventilation; 94 (72%), vasopressor support; 26 (20%), continuous renal replacement therapy (CRRT); and 11 (9%), extracorporeal membrane oxygenation. One hundred twenty one (93%) patients received antiviral therapy (median 5 d). Thirty-day mortality was 23%. Patients who received antiviral treatment were more likely to survive with an adjusted hazard ratio (aHR) of 0.15 (95% CI 0.04 to 0.51, p = 0.003). Other independent predictors of mortality were the need for CRRT (aHR 2.48, 95% CI 1.14 to 5.43, p = 0.023), higher APACHE II score (aHR 1.08, 95% CI 1.02 to 1.14, p = 0.011), and influenza A (aHR 7.10, 95% CI 1.37 to 36.8, p = 0.020) compared with influenza B infection. Conclusions: Among critically ill influenza patients, antiviral therapy was independently associated with survival. CRRT, higher severity of illness, and influenza A infection were associated with mortality.