Quantitative physical chemistry analysis of acid-base disorders in critically ill patients

Compared with the Henderson-Hasselbalch approach, the Stewart approach may better describe the mechanisms of acid-base physiology and disorders. We pr ospectively examined the acid-base disorders of 100 routine blood samples f rom critically ill patients using Stewart's physical chemistry analysis. Th e median results were pH 7.45, PaCO2 5.5 kPa, bicarbonate 27.2 mmol.l(-1) a nd base excess 3 mmol.l(-1). The median reference strong ion difference was 46.0 meq.l(-1) and the measured median was 45.5 meq.l(-1). The median refe rence total weak-acid concentration was 11.1 mmol.l(-1) The measured median total weak-acid concentration was 6.8 mmol.l(-1). From Stewart's approach, the most likely explanation for the overall alkalosis was decreased total weak-acid concentration resulting from decreased plasma albumin concentrati on.