Serum lactate and base deficit as predictors of mortality in normotensive elderly blunt trauma patients.

BACKGROUND: Base deficit (BD) and lactate are used as markers of mortality, injury severity, and resource utilization in the general trauma population. No study has defined the role of these markers in the triage and management of the normotensive injured elderly patient.

METHODS: Retrospective cohort study of the trauma registry from a Level I trauma Center during the period of January 1, 2000 through December 31, 2006. Inclusion criteria were age > or = 65 years, initial systolic blood pressure > or = 90 mm Hg; blunt mechanism of trauma. Lactate was categorized as 0 to 2.4 mmol/L (normal), 2.5 to 4.0 mmol/L (moderately elevated), or > 4.0 mmol/L (severely elevated). BD was categorized as > 0 mEq/L (normal), 0 to -6 mEq/L (moderate), or < -6 mEq/L (severe). The primary outcome was inhospital mortality.

RESULTS: Mean lactate was higher in nonsurvivors compared with survivors (2.8 mm/L +/- 1.8 mm/L vs. 2.0 mm/L +/- 1.0 mm/L, p < 0.001). Normal, moderately elevated, and severely elevated lactate was associated with mortality rates of 15% (95% confidence interval [CI] 12-18.8%), 23.4% (95% CI 2-32.4%), and 39.6% (95% CI 26.5-52.8%), respectively. Compared with the normal lactate group, patients in the severely elevated lactate group had 4.2 increased odds of death. BD was more abnormal in nonsurvivors compared with survivors (-2.3 mEq/L +/- 5.2 mEq/L vs. 0.28 mEq/L +/- 1.0 mEq/L, p < 0.001). Normal, moderate, and severe BD were associated with mortality rates of 14% (95% CI 10.3-17.1%), 27% (95% CI 20.1-34.2%), and 40% (95% CI 24.9-54.1%), respectively. Compared with the normal BD group, patients in the severe group had 4.1 increased odds of death.

CONCLUSIONS: Both lactate and BD were associated with significantly increased mortality in normotensive elderly blunt trauma patients. However, because of the high baseline mortality rates in elderly trauma patients, "normal" lactate does not offer complete reassurance to the clinician.