system (Mullins et al., 1996). A more recent publication reinforced earlier findings, demonstrating that mortality improvements were attributable to the introduction of the trauma system rather than to concurrent improvements in new technologies and treatments (Mullins et al., 1998).
The studies cited above focus on the hospital phase of care. There is scanty knowledge of outcomes in the prehospital (Spaite et al., 1993) and rehabilitation phases of care (IOM, 1997a). For example, there is incomplete understanding of the effectiveness of many widely used prehospital interventions, such as fluid repletion, its nature and timing, as a means of patient resuscitation (NIH, 1994). There is another critical gap in research on outcomes relating to morbidity, in both the short and the long term (NIH, 1994). Measures of morbidity have to transcend the traditional medical model to encompass measures of productivity, disability, and quality of life. Morbidity outcomes also need to be tracked post-discharge from acute and rehabilitative care. Additionally, research on the design and effectiveness of trauma systems must take into account the differences between trauma systems that are related to the mechanism of injury (e.g., blunt versus penetrating trauma) in each system.
In summary, studies demonstrate that acute trauma care reduces patient mortality. However, very few studies have addressed improved long-term morbidity with trauma systems (Rhodes et al., 1988) and improved quality of care (Shackford et al., 1986). Much work remains in order to demonstrate the benefits of trauma care in relation to morbidity. Additional work also is necessary to identify which elements of a trauma system are most responsible for reductions in morbidity and mortality. Research that identifies the most effective elements is difficult to perform for the following reasons: the elements have to be carefully defined and measured for comparative analysis, major trauma itself requires better definition, and an appropriate comparison group has to be identified as a control population.
Evaluating outcomes of trauma systems often depends on the availability of research measures for evaluating patient outcomes and clinical effectiveness. Research is needed to develop more reliable and valid measures of (1) injury severity and case mix and (2) short- and long-term outcomes that are sensitive to changes over time and to differences in treatment. These two areas are discussed below.
Indicators used as a basis for assessing the severity of an injury include anatomical descriptors for assessing the extent of tissue damage; the mechanism