Lactate and base deficit in trauma: does alcohol or drug use impair their predictive accuracy?

BACKGROUND: Abnormal blood lactate and base deficit (BD) reflect hypoperfusion and have been documented to predict outcome in trauma. Alcohol and drug use may also induce metabolic acidosis in trauma victims, potentially diminishing the predictive accuracy of lactate and BD. We, therefore, sought to examine the effect of alcohol and drug use on the predictive accuracy of admission blood lactate and BD in trauma.
METHODS: Prospective data were collected on 15,179 patients admitted to the R Adams Cowley Shock Trauma Center over a 3-year period from 1998 to 2000. Patients were stratified by age, gender, race, injury severity score (ISS), Glasgow coma score (GCS), alcohol concentration and illicit drug use. Multiple regression analyses were used to assess admission blood lactate and BD as independent risk factors for mortality, intensive care unit (ICU) admission, and ICU and hospital length of stay (LOS) controlling for alcohol and drug use [cocaine, phencyclidine and methamphetamines] by measured serum concentrations.
RESULTS: The mean age of the study cohort was 37 +/- 19 years, mean ISS was 9 +/- 10, mean GCS 14.1 +/- 2.7, 71% were male and 77% sustained blunt trauma. Alcohol testing was completed in 13,102 of 15,179 (86.3%) of patients. Alcohol screen was positive in 27% (n = 3536) of the total cohort tested (n = 13,102) with a mean blood alcohol concentration of 141 +/- 95 mg/dL; 7% (n = 992) had positive drug screens. Increasing injury severity was associated with significantly increased admission blood lactate and BD (p < 0.001). Patients with positive alcohol and drug screens had significantly increased admission blood lactate, BD and injury severity compared with patients with negative alcohol and drug screens (p < 0.01). Patients with positive alcohol and drug screens had a significant increase in admission to the ICU (p < 0.05), but no significant increase in mortality, ICU or hospital LOS compared with patients with negative screens. Multiple logistic and linear regression analyses confirmed admission lactate and BD as significant independent predictors of mortality, ICU and hospital LOS (p < 0.01). These results were unchanged after controlling for alcohol and drug use as covariates in the logistic and linear regression analyses.
CONCLUSION: Alcohol and drug use are common in trauma, but do not impair the predictive accuracy of admission lactate and BD in trauma outcome. Admission lactate and BD are therefore confirmed as significant independent predictors of trauma outcome in patients with acute alcohol and drug use in this largest clinical study to date.