Patients with influenza admitted to a tertiary-care hospital in Riyadh between 2018 and 2022: characteristics, outcomes and factors associated with ICU admission and mortality

Abstract

Abstract Background Influenza is a common cause of hospital admissions globally with regional variations in epidemiology and clinical profile. We evaluated the characteristics and outcomes of patients with influenza admitted to a tertiary-care center in Riyadh, Saudi Arabia. Methods This was a retrospective cohort of adult patients admitted with polymerase chain reaction-confirmed influenza to King Abdulaziz Medical City-Riyadh between January 1, 2018, and May 31, 2022. We compared patients who required intensive care unit (ICU) admission to those who did not and performed multivariable logistic regression to assess the predictors of ICU admission and hospital mortality. Results During the study period, 675 adult patients were hospitalized with influenza (median age 68.0 years, females 53.8%, hypertension 59.9%, diabetes 55.1%, and chronic respiratory disease 31.1%). Most admissions (83.0%) were in the colder months (October to March) in Riyadh with inter-seasonal cases even in the summertime (June to August). Influenza A was responsible for 79.0% of cases, with H3N2 and H1N1 subtypes commonly circulating in the study period. Respiratory viral coinfection occurred in 12 patients (1.8%) and bacterial coinfection in 42 patients (17.4%). 151 patients (22.4%) required ICU admission, of which 62.3% received vasopressors and 48.0% mechanical ventilation. Risk factors for ICU admission were younger age, hypertension, bilateral lung infiltrates on chest X-ray, and Pneumonia Severity Index. The overall hospital mortality was 7.4% (22.5% for ICU patients, p 20%. Female sex, high Pneumonia Severity Index, ischemic heart disease, and immunosuppressed state were associated with increased mortality.

Keywords

• Pneumonia
• Influenza
• Intensive care
• Mechanical ventilation
• Outcomes