Use of Intensive Care Units for Patients With Low Severity of Illness

OBJECTIVE: To determine variations among hospitals in use of intensive care units (ICUs) for patients with low severity of illness. DESIGN: Retrospective cohort study. SETTING: Twenty-eight hospitals with 44 ICUs in a large metropolitan region. PATIENTS: Consecutive eligible patients (N=104,487) admitted to medical, surgical, neurological, or mixed medical-surgical ICUs from March 1, 1991, to March 31, 1995. OUTCOME MEASURES: The predicted risk of in-hospital death for each patient was assessed using a validated method that is based on age, ICU admission source, diagnosis, severe comorbid conditions, and abnormalities in 17 physiologic variables. Admissions were classified as low severity if the patient's predicted risk of death was less than 1%. In a subset of 12,929 consecutive patients, use of 19 specific interventions typically delivered in ICUs was examined. RESULTS: Twenty thousand four hundred fifty-one admissions (19.6%) were categorized as low severity, including 23.6% of postoperative and 16.9% of nonoperative admissions. Alcohol and other drug overdoses accounted for 40.2% of nonoperative low-severity admissions; laminectomy and carotid endarterectomy accounted for 52.3% of postoperative low-severity admissions. Mortality among patients with low-severity illness was 0.3%, and only 28.6% received an ICU-specific intervention during the first ICU day. Although mean ICU length of stay was shorter (P<.001) in low-severity admissions (2.2 vs 4.7 days in nonoperative and 2.4 vs 4.2 days in postoperative admissions), low-severity admissions accounted for 11.1% of total ICU bed days. Rates of low-severity admissions varied (P<.001) across hospitals, ranging from 5% to 27% for nonoperative and 9% to 68% for postoperative admissions. CONCLUSIONS: A large proportion of patients admitted to the ICU have a low probability of death and do not receive ICU-specific interventions. Rates of low-severity admissions varied among hospitals. The development and implementation of protocols to target ICU care to patients most likely to benefit may decrease the number of low-severity ICU admissions and improve the cost-effectiveness of ICU care.