Using the Stewart Model at the Bedside

Disorders of acid-base balance are among the most common abnormalities seen, especially in critically ill and injured patients. While many disorders are benign or self-limiting, severe disorders of acid-base balance are life threatening, especially when these derangements develop quickly. Although controversy exists as to the effect of mild to moderate acid-base disorders, severe abnormalities can be the direct cause of organ dysfunction [1]. For example, acidemia is associated with increased adrenergic tone [1] and, on this basis, can promote the development of cardiac dysrhythmias in critically ill patients or increase myocardial oxygen demand in patients with myocardial ischemia. Emerging evidence suggests that changes in acid-base variables influence immune effector cell function [2,3]. It is therefore important to understand both the causes of acid-base disorders and the limitations of various treatment strategies. It is the Stewart approach that may be most helpful in this respect. A list of terms and abbreviations are shown in Table 19.1.