Base deficit in the elderly: a marker of severe injury and death.

BACKGROUND: Base deficit has been used as a marker of significant injury and to predict resource utilization and mortality. The significance of base deficit in trauma patients 55 years and older has not been specifically evaluated. The purpose of this study was to determine the utility of base deficit in assessing older trauma patients versus a younger cohort.
METHODS: Data were obtained from the trauma registry on trauma patients admitted to a Level I trauma center. Arterial blood gases were obtained within 1 hour of arrival, by protocol, in 2,631 patients, and of these, 274 patients were 55 years or older. Data are presented as means+/-SEM. Statistical analysis was done by paired t test, analysis of variance, and chi2 analysis. Significance was attributed to a p value < 0.05.
RESULTS: Patients older than 55 years were significantly more likely to have sustained blunt trauma (86 vs. 69%; p < 0.001). Despite similar Injury Severity Scores and base deficit values, older patients had markedly greater mortality and intensive care unit lengths of stay. A base deficit of < or = -6 had positive predictive values for Injury Severity Scores > or = 16 for 76% of patients younger than 55 years and 78 % of patients 55 years and older. The negative predictive value of a normal base deficit for Injury Severity Scores < or = 16 was 60% for the younger cohort and only 40% for patients 55 years and older (p < 0.001; chi2).
CONCLUSIONS: A base deficit of < or = -6 is a marker of severe injury and significant mortality in all trauma patients, but it is particularly ominous in patients 55 years and older. Patients older than 55 years may have significant injuries and mortality risk without manifesting a base deficit out of the normal range.