Differences in early, intermediate, and long-term mortality among elderly patients admitted to the ICU: results of a retrospective observational study.

Background: Few studies have investigated both short- and long-term prognostic factors, and the differences between chronic and acute conditions in the very old critically ill patient. Our study aims to shed light in this field and to provide useful prognostic factors that may support clinical decisions in the management of the elderly.

Methods: Six ICUs collected data concerning 80-year-old (or more) patients admitted in 2015 and 2016 and followed-up until May 2018. Three prognostic models were developed: an in-hospital mortality model, a model for patients discharged from the hospital and entering follow-up, and an intermediate model for those alive after three days from ICU admission.

Results: Our centers admitted 1189 patients, 1071 (90.1%) had survived after three days from admission, 889 (74.8%) were discharged from the hospital, 701 (59.0%) survived six months after hospital discharge, 539 (45.3%) survived at the end of follow-up. Among survivors the median follow-up time was 810 days. Acute organ failures were the main causes of death in the hospital mortality multivariable model. These factors are modifiable and potentially a target for intervention to improve outcome. The model focused on mortality six months after hospital in patients that survived a three-day time-limited trial, showed a clear shift toward chronic diseases, unmodifiable factors crucial for prognostic assessment. This trend was even more evident at the end of follow-up.

Conclusions: Among very old ICU patients, prognostic factors shift from acute to chronic conditions in passing from in-hospital to posthospital outcomes.