Surviving Nonsurvivable Injuries: Patients Who Elude the 'Lethal' Abbreviated Injury Scale Score of Six.

BACKGROUND

The Abbreviated Injury Scale (AIS) score is used widely to quantify injury severity by body region. The maximal AIS score is 6, which defines a nonsurvivable injury. This study was undertaken to define mortality after AIS-6 injuries in order to determine if they are uniformly lethal and, if not, if differences between survivors and nonsurvivors exist which may aid in prognostication or refinement of the current AIS system.

METHODS

All patients in the National Trauma Data Bank (2007-2017) with ≥1 AIS-6 injury were included. Exclusions were age <16 years, AIS-6 coding in the face/extremities (i.e., coding errors, as there are no AIS-6 injuries in these regions), and missing data. In-hospital mortality defined study groups, i.e., survivors vs. nonsurvivors. Univariable analysis compared clinical/injury data and outcomes. Multivariable analysis examined independent factors associated with mortality.

RESULTS

19,247 patients met inclusion/exclusion criteria. Of these, 25% (n=4,886) survived to hospital discharge and 75% (n=14,361) died. The most common discharge destination among survivors was home (n=2,187,45%) Nonsurvivors had significantly worse GCS in the field (3 vs. 14, p<0.001) and ED (3 vs. 15, p<0.001). Median AIS was higher among nonsurvivors in the Head (5 vs. 3, p<0.001), Abdomen (3 vs. 2, p<0.001), and External regions (1 vs. 1, p<0.001). Median time to death was 0.65h, with maximum time to death 8.76h. Multivariable analysis revealed External AIS-6 injuries were associated with greatest odds of mortality (OR 34.002, p<0.001) followed by Head AIS-6 (OR 10.501, p<0.001).

CONCLUSION

AIS-6 injuries are not uniformly fatal, with 25% of such patients surviving to hospital discharge. Therefore, AIS-6 injuries may not be as catastrophic as previously considered. External and Head AIS-6, i.e. extensive burns and severe traumatic brain injuries, were associated with greatest odds of mortality. When death occurs after AIS-6 injury, it occurs rapidly, with all mortalities in this series occurring <9h after arrival. We suggest that the AIS-6 verbiage be revised to remove 'nonsurvivable'.