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

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Abstract
Compared with the Henderson−Hasselbalch approach, the Stewart approach may better describe the mechanisms of acid−base physiology and disorders. We prospectively examined the acid−base disorders of 100 routine blood samples from critically ill patients using Stewart's physical chemistry analysis. The median results were pH 7.45, Paco2 5.5 kPa, bicarbonate 27.2 mmol.l−1 and 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 reference 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 concentration.