Long-term outcomes for patients treated in the Intensive Care Unit (ICU): a cohort study using linked data

Teresa Williams

Research output: ThesisDoctoral Thesis

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Abstract

Royal Perth Hospital is the largest hospital in Western Australia and also has the largest intensive care unit (ICU) in the State. It was the first public hospital to provide intensive care services in Western Australia. This thesis examines the intermediateand long-term outcomes of patients admitted to the Royal Perth Hospital ICU between 1987 and 2002. Intermediate-term survival, defined as survival after discharge from hospital to one year and long-term survival, that exceeding one year after discharge, are important outcomes. Information on outcomes can be used by ICU staff in discussions with patients and their families and to inform policy decision-making and future research. The aim of this research was to examine one-year and long-term outcomes of patients admitted to the ICU between 1987 and 2002 and explore the factors that might be associated with the outcomes for 22,298 patients admitted to the ICU. A clinical ICU database was linked to morbidity and mortality databases by Data Linkage WA. A wide range of demographic and clinical factors were examined for their effect on outcome. These included age, sex, comorbidity, severity of illness, organ failure, ICU diagnostic groups, type of admission (medical, elective surgical and non-elective surgical), length of stay in ICU and era of admission (1987-1990, 1991-1994, 1995-1998, 1999-2002). Patients were followed-up to study end, 31st December 2003 or death if it occurred before study end, that is, up to 17 years after the index ICU admission. Kaplan Meier survival curves and Cox regression models were used to examine intermediate and long-term survival for patients who survived to hospital discharge. A comparison of admissions to hospital before and after the index ICU admission was made using descriptive statistics and logistic regression. Throughout the study period survival for the ICU cohort was shorter when compared to the Australian population. This was consistent throughout the follow-up period. The most important determinants of long-term survival were age, comorbidity, severity of illness and diagnostic group but the strength of association varied with the duration of follow-up. Although age, comorbidity and severity of illness increased among the critically ill survival improved over time. Hospital admissions were more frequent after a discharge from hospital that required an admission to ICU than before the index admission, even after adjusting for the ageing of the cohort. This study provides unique information about the survival and other outcomes of patients discharged from a hospital admission that included an ICU stay. The strength of this study lies in the follow-up to 17 years and the more comprehensive range of explanatory factors than in previous studies. This thesis demonstrates that follow-up studies after intensive care should be of sufficient duration to account for the changes that occur in survival over time and indicates the range of factors that should be taken into account when making comparisons of long-term survival.
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2008

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