Determinants of long-term survival after intensive care*

Abstract

To identify prognostic determinants of long-term survival for patients treated in intensive care units (ICUs) who survived to hospital discharge. An ICU clinical cohort linked to state-wide hospital records and death registers. Adult patients admitted to a 22-bed ICU at a major teaching hospital in Perth, Western Australia, between 1987 and 2002 who survived to hospital discharge (n = 19,921) were followed-up until December 31, 2003. The main outcome measures are crude and adjusted survival. The risk of death in the first year after hospital discharge was high for patients who survived the ICU compared with the general population (standardized mortality rate [SMR] at 1 yr = 2.90, 95% confidence interval [CI] 2.73-3.08) and remained higher than the general population for every year during 15 yrs of follow up (SMR at 15 yrs = 2.01, 95% CI 1.64-2.46). Factors that were independently associated with survival during the first year were older age (hazard ratio [HR] = 4.09; 95% CI 3.20-5.23), severe comorbidity (HR = 5.23; 95% CI 4.25-6.43), ICU diagnostic group (HR range 2.20 to 8.95), new malignancy (HR = 4.60; 95% CI 3.68-5.76), high acute physiology score on admission (HR = 1.55; 95% CI 1.23-1.96), and peak number of organ failures (HR = 1.51; 95% CI 1.11-2.04). All of these factors were independently associated with subsequent survival for those patients who were alive 1 yr after discharge from the hospital with the addition of male gender (HR = 1.17; 95% CI 1.10-1.25) and prolonged length of stay in ICU (HR = 1.42; 95% CI 1.29-1.55). Patients who survived an admission to the ICU have worse survival than the general population for at least 15 yrs. The factors that determine long-term survival include age, comorbidity, and primary diagnosis. Severity of illness was also associated with long-term survival and this suggests that an episode of critical illness, or its treatment, may shorten life-expectancy.