Computer-based data collection and objective gathering of degree of illness severity and risk of death with a prognostic scoring system make it possible to obtain, in addition to epidemiological and aetiological data, risk-related outcome values for patients in an intensive care unit.All 2054 patients who during a 2-year period (1995-1996) had stayed in a medical intensive care unit (MICU) for more than 4 hours were studied prospectively. The simplified acute physiology score II (SAPS II), risk of death, duration of stay in the MICU and in the hospital, and death rates during MICU and hospital stay were determined. Mean and median values and histograms of the various parameters as well as the standardized mortality index (SMI: observed/ predicted death rate with 99% confidence limits) were calculated for each of the patients and certain defined subgroups (basic disease, age, risk). Receiver operating characteristics curves (discrimination) and calibration curves were obtained for SAPS II.Mean age for the cohort was 59.8 years, duration of stay in the MICU 3.1 days, in hospital 14.7 days, SAPS II was 30.3 points, death risk 0.17, death rate during ICU stay was 8.3%, during hospital stay 13.9% and the SMI 0.8% (0.74-0.88). Cardiac disease was the most common underlying condition (60%), while the small group of neurological conditions was remarkable for the high degree of severity and unfavourable prognosis. Both death rate and degree of disease severity increased with age. But the SMI was not significantly higher than 1.0 in both the elderly patients and the high-risk group of patients (on ventilator, renal replacement procedures, death risk > 0.5).Most patients in a MICU have underlying cardiac disease. Permanently available neurological consultation is essential. The high hospital death rate for elderly patients and those requiring respiratory support is a problem of disease severity, not of the quality of treatment. The risk of death is high on transfer to a general ward. Determination of the SMI is recommended for internal quality control in an ICU.
