This prospective, multi-center, observational study of 2069 multiple trauma patients evaluated the prognostic significance of the posttrauma base deficit (BD) on hospital and intensive care unit (ICU) admission to hemodynamic changes, volume and transfusion requirements, lactate and coagulation, as well as mortality. Furthermore, the importance of the BD development throughout a patient's course of critical illness from the time of injury to ICU admission is analyzed as a prognostic factor for fatal outcome. The data were obtained by the trauma registry of the 'Deutsche Gesellschaft für Unfallchirurgie.' The patients were subdivided into five categories of increasing BD values on hospital and ICU admission: Category I, BD < or = -2; Category II, -2 < BD < or = 2; Category III, 2 < BD < or = 6; Category IV, 6 < BD < or = 10; and Category V, BD > 10. A statistical analysis was performed by means of the ANOVA and chi-square tests. In 1264 (61.1%) of 2069 multiple trauma patients (age 39 +/- 19 years, 70.0% males, injury severity score 22 +/- 13, 18.6% mortality), the BD was documented on hospital and in 1536 (74.2%) patients on ICU admission. At both points in time, an increase in the BD category was associated with a significant decrease in systolic blood pressure and prothrombin time as well as increases in heart rate, lactate level and mortality (P < 0.0001). Also transfusion requirements (Category I: 4.5 +/- 7.7 and Category V: 13.7 +/- 13.0 packed red blood cells) increased significantly on hospital admission (P < 0.0001) with a worsening in the BD category. Mortality increased significantly (P < 0.0001) with a worsening of BD from hospital to ICU admission (from a mortality of 13% in patients with a hospital and an ICU admission BD of <6 to 45% in patients with a hospital and an ICU admission BD of >6). These data show that the base deficit is an early available important indicator to identify trauma patients with hemodynamic instability, high transfusion requirements, metabolic and coagulatory decompensation, as well as a high probability of death. The base deficit development may help to guide an early and aggressive therapy for the trauma/hemorrhage induced tissue hypoxia.