Impact of age in critically Ill infected patients: a post-hoc analysis of the INFAUCI study

Purpose Older patients are the fastest expanding subgroup of intensive care units (ICU) and are particularly susceptible to bacterial infections and sepsis. The aim of this study was to address the epidemiology and the main determinants of outcome of infection in old and very old patients admitted to ICU. Methods We performed a post hoc analysis of all infected patients admitted to ICU enrolled in a 1-year prospective, observational, multipurpose study. Patients aged < 65, 65-74 and >= 75 years were compared. Results Of the 1652 patients included, 50% were older than 65 years. There were no significant differences between young, old and very old patients in either ICU, hospital length of stay, or nosocomial infection. All-cause mortality was significantly higher in participants aged >= 75. Increased Gram-negative microorganisms' isolates occurred in > 65 years (25% versus 31%; p = 0.034). Multidrug-resistant (MDR) microorganisms were directly associated to inappropriate empiric antibiotic therapy (OR 4.73; 95% CI 2.99-7.47) and inversely associated with community-acquired infection (OR 0.39; 95% CI 0.19-0.83). Age (65-74 years: OR 1.10; 95% CI 0.64-1.90 and >= 75 years: OR 1.52; 95% CI 0.89-2.59) and sepsis severity (sepsis: OR 0.67; 95% CI 0.18-2.46; severe sepsis: OR 1.17; 95% CI 0.40-3.44; septic shock: OR 0.77; 95% CI 0.27-2.24) were not associated to MDR bacteria. Conclusion Patients > 65 years accounted for 50% of infected patients admitted to an ICU. ICU and hospital length of stay, and nosocomial infection did not increase with age. Age did predispose to increased risk for infection by Gram-negatives. These findings may optimize strategies for infection management in older patients.