A population-based study of outcome after injury to car occupants and to pedestrians

The literature indicates that trauma center pedestrian mortality rates approximate twice that of injured car occupants. This study was performed to test the hypothesis that outcomes will be similar given similar degrees of injury severity if analyzed from an epidemiologic perspective. Differences are expected in the cause and place of death because of different injury profiles.

Prospective population-based study.

The study group consisted of all adult car occupants and pedestrians sustaining major injury -- Injury Severity Score (ISS) of >15 -- in a defined area of central Sydney from mid-1991 to mid-1994.

The study included 65 car occupants (median ISS,32) and 101 pedestrians (median ISS,34). Major abdominal injury (p = 0.003) and thoracic aortic disruption (p = 0.06) were more common in car occupants, but major injury to the brains (p = 0.004), lower extremity long bone fractures (p = 0.0005), and thoracolumbar fractures (p = 0.01) occurred more frequently in pedestrians. The overall car occupant mortality was 38% compared with 46% in the pedestrians (p = 0.37). Seventy-two percent of car occupant fatalities occurred in the field, most commonly from ruptured thoracic aorta, whereas 63% of pedestrian deaths occurred in hospital (p = 0.005), most commonly from head injury.

These findings have important implications for prehospital care. A policy of "scoop and run" is advocated for injured car occupants in shock because of the high frequency of aortic and abdominal injuries. Advanced life support measures are appropriate at the scene to stabilize the airway and to protect the entire spine in pedestrians with multiple injuries because of the high frequency of brain and vertebral trauma.