A physicochemical approach to acid-base balance in critically ill trauma patients minimizes errors and reduces inappropriate plasma volume expansion.

BACKGROUND: This study assesses if a physicochemical (PC) approach to acid-base balance improves the accuracy of acid-base diagnosis, and reduces inappropriate fluid loading.

METHODS: Hundred consecutive patients with trauma admitted to a surgical intensive care unit at a level I trauma center were prospectively analyzed. Demographics, acid-base data and diagnoses, and interventions were collected. Patients were cared for by one physician using a PC approach, or four using conventional (CONV) acid-base balance techniques. The diagnoses and interventions made by CONV physicians were reviewed by the PC physician for accuracy and appropriateness using PC techniques. Data are mean +/- SD or percents; p values reflect PC evaluation of CONV analysis.

RESULTS: There were 50 PC patients and 50 CONV. There were no differences in age (p = 0.13), injury severity score (p = 0.21), number of operations (p = 0.87), transfusions (p = 0.87), or survival (p = 0.15). CONV missed 12 diagnoses of metabolic acidosis (p = 0.03), 10 of hyperchloremic metabolic acidosis (p = 0.003), 11 metabolic alkalosis (p = 0.02), and 19 tertiary disorders (p < 0.001). CONV missed 38 diagnoses of increased unmeasured ions (p < 0.001). PC normalized their acid-base balance sooner than CONV (3.3 days +/- 3.4 days vs. 8.3 days +/- 7.4 days, p < 0.01).

CONCLUSIONS: A PC approach improves acid-base diagnosis accuracy. CONV often miss acidosis (particularly those because of hyperchloremia), alkalosis, and tertiary disorders. Inappropriate volume loading follows in the wake of misinterpretation of increased base deficit using CONV and is avoided using PC. PC-directed therapy normalizes acid-base balance more rapidly than CONV.