Severity of illness and the relationship between intensive care and survival.

Currently about 15 per cent of hospital costs are attributed to intensive care. Research using statistical models has not adequately demonstrated that therapy in intensive care units (ICUs) is associated with reductions in the probability of death. In a study of 613 consecutive admissions to a multidisciplinary ICU, we reevaluate the relationship between ICU care and survival using a new acute physiology scoring system to control for the severity of illness of the patient population. When our severity of illness index was employed, we found a statistically significant and nonlinear relationship between the use of intensive medical care and the probability of survival. This statistical relationship produced a U-shaped curve with three distinct segments. The first segment exhibited an overall decrease in the probability of death with increasing therapy (275 admissions); the second segment, a fairly stable survival rate (281 admissions). Only in the third segment, where there were 57 admissions, did we find an overall increase in the probability of death as utilization of therapy increased. These findings suggest that quantitative measurement of severity of illness, when used in clinical studies, could produce improved insights into the relationship between therapy and health outcomes.