Demographic and clinical variation of adult intensive care unit utilization from a geographically defined population

To determine population-based rates of adult intensive care unit (ICU) use and evaluate the effects that demographic variables and chronic illness have on ICU utilization.

Retrospective, population-based cohort study.

Olmsted County, Minnesota.

Adult residents admitted to an ICU in 1998.

None.

Measurements included demographics, Acute Physiology and Chronic Health Evaluation III score, ICU admission diagnosis, ICU interventions, Charlson comorbidity index and conditions, ICU length of stay (LOS), and ICU, hospital, 1-month, and 1-yr mortalities. Risk of ICU admission and rates of ICU utilization increased substantially with increasing age, peaking in the very elderly. The rates of ICU admission and utilization in those > or =85 yrs old were 58.2 admissions/1,000 residents and 195.8 days/1,000 residents compared with 3.8 admissions/1,000 residents and 11.5 days/1,000 residents in those 18 to 44 yrs old. Residents > or =85 yrs old were 3.75 times as likely (p < .001) to be admitted to the ICU compared with those 18-44 yrs old after controlling for the presence of comorbid illness. ICU admission rates increased with an increasing number of comorbid illnesses. Residents with cardiovascular conditions and renal disease had high rates of ICU admission. Repeat users of the ICU were more likely to have a chronic condition and higher degree of comorbid illness compared with nonrepeat users. ICU mortality was similar across all age groups, except in those > or =85 yrs old, for whom mortality was greater. One-year mortality after ICU admission increased with increasing age.

Population-based rates of ICU admission and utilization in Olmsted County, Minnesota, increased with age and are highest in the very elderly. The presence of chronic illness, particularly cardiovascular conditions, significantly increases ICU utilization and risk of ICU admission.