Using population death rate to predict rate of admissions to the intensive care unit.
OBJECTIVE: To determine whether the intensive care unit (ICU) admission rates of new health plan members can be predicted by the mortality of non-ICU-treated members. DESIGN: Retrospective study of health records. PATIENTS: Five sequential cohorts of new health plan members (298,974 members) seen at any of three tertiary care medical centers of a health maintenance organization in northern California who joined the health plan during the first quarter of 1994, 1995, 1996, 1997, or 1998 and retained membership for > or =1 yr. SETTING: Three medical centers in northern California. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We measured rates of ICU admission, death, and mechanical ventilation among cohort members. ICU admission rate varied between hospitals and over time but was predicted by non-ICU mortality-ICU admission rate = 0.83 x non-ICU mortality-and was linear throughout its range. In no hospital or time period was a higher mortality associated with fewer ICU admissions. Seventeen percent of population deaths occurred among ICU patients and did not differ among medical centers. CONCLUSIONS: A single linear equation predicted ICU admission rate from death rate of non-ICU-treated patients among cohorts of new members. ICU admission rates can be predicted from a measure of population illness burden, such as the mortality of non-ICU-treated patients. It may be possible to extend this analysis to other hospitals and health care systems to evaluate the adequacy of ICU services provided.