Association Between Initial Icu Admission Diagnosis And Outcomes In Chronic Critically Ill Patients: A Retrospective Cohort Study

INTRODUCTION: Advancements in the care of acutely ill patients has reduced intensive care unit (ICU) mortality but has also led to the emergence of a group of patients who have a prolonged dependency on life support measures. Despite this rapidly growing demographic, a relatively minimal amount is known in the way of identifiable risk factors for outcomes in chronic critically ill patients. We sought to explore the association between admission diagnostic category and acute hospital mortality in chronic critically ill patients. METHODS: The study is a retrospective cohort study of adult patients aged 18 and over, admitted to two Canadian, university associated ICUs between July 2012 and June 2013. We included in our study all patients who had a tracheostomy placed for prolonged mechanical ventilation in the ICU. The primary outcome was ultimate acute hospital mortality. A univariate and multivariate analysis was performed to assess the association of admission diagnostic category and ultimate acute hospital mortality. RESULTS: One hundred and forty-four patients received a tracheostomy in the ICU during the study period with 134 patients eligible for analysis. We demonstrated both baseline characteristics and outcomes differences between medical patients, non-trauma surgical patients and trauma patients. The trauma group had a lower ICU and hospital mortality even after adjusting for potential confounders such as severity of illness and co-morbidities (OR: 0.1 95% CI 0.0-0.3, p < 0.001). They were also more likely to be discharged home or to a rehabilitation center. CONCLUSION: In conclusion, we demonstrated that ICU admission diagnostic category is associated with acute hospital mortality. Chronic critically ill trauma patients were found to have lower acute hospital mortality rates than medical or non-trauma surgical patients even after adjustment for confounders using severity of illness scores that contain variables for admission type. Admission diagnostic category should inform patients, surrogate decision makers and the health care team regarding decisions related to tracheostomy placement and prolonged supportive care.