The study was conducted in 38 ICUs in 28 hospitals participating in CHQC. Nineteen of the study ICUs were mixed medical and surgical units, eight ICUs were medical, eight ICUs were surgical, and three were neurologic and/or neurosurgical. Thirteen additional ICUs in study hospitals that specialized in coronary care (n = 11) or cardiovascular surgery (n = 2) were excluded from the study, as per CHQC protocols. Five hospitals were members of the Council of Teaching Hospitals of the Association of American Medical Colleges during the period of data collection, and were considered major teaching hospitals for the current study. Other characteristics of participating hospitals and ICUs have been described previously.
The eligible sample was drawn from 134,402 consecutive ICU admissions from March 1, 1991 to March 31, 1995 Source allergies pills. Patient data were collected on all ICU admissions with the following exceptions: individuals < 16 years of age; burn patients; patients admitted solely for hemodialysis or peritoneal dialysis; patients who die within 1 h of admission to the ICU or within the first 4 h after admission to the ICU in cardiopulmonary arrest; and patients undergoing coronary artery bypass, cardiac valve, or heart transplant surgery. These exclusions are consistent with those reported in the original APACHE III or were directed by CHQC data collection policies. Of the eligible sample, 8,114 (6.0%) who were readmitted to an ICU during a single episode of hospitalization, 9,167 (6.8%) who were discharged to other acute-care hospitals for further management, and 781 (0.6%) who had missing severity of illness or outcome information were excluded from analysis. The final sample consisted of 116,340 patients.
Data were abstracted from patients’ ICU records by trained data reviewers using standard forms and data collection software (provided by APACHE Medical Systems, Inc; McLean, VA). Variables included elements necessary to determine an APACHE III acute physiology score (APS): age; presence of specific severe comorbid conditions (eg, AIDS, metastatic cancer, hepatic failure, lymphoma); and the most abnormal value during the first 24 h of ICU admission for 17 specific physiologic variables (eg, mean arterial BP, serum sodium and BUN, arterial oxygen tension, arterial pH, abbreviated Glasgow Coma Score).