Has Stewart approach improved our ability to diagnose acid-base disorders in critically ill patients?

Figure 1 Independent determinants of pH according to the Stewart approach.

Figure 2 Behavior of pH (top), HCO₃^- (middle) and PCO₂ (bottom) in a closed system (black dots) and in an open system with a PCO₂ of 40 mmHg (withe dots), during stepwise dilution with 0. 9% NaCl, as modified from Gattinoni et al[32].

Figure 3 Regression and Bland and Altman analysis between metabolic parameters of different approaches in seven normal volunteers. A: Lineal regression between base excess and strong ion difference; B: Agreement between base excess and strong ion difference; C: Lineal regression between albumin-corrected anion gap and strong ion gap; D: Agreement between albumin-corrected anion gap and strong ion gap; Panel B and D display the relationship between the mean value and the difference of both measurements. The lines indicate the mean difference between both parameters (bias) ± 2 SD (95% limits of agreement). Modified from Dubin et al[37].

Figure 4 Regression and Bland and Altman analysis between metabolic parameters of different approaches in 935 critically ill patients. A: Lineal regression between base excess and strong ion difference; B: Agreement between base excess and strong ion difference; C: Lineal regression between albumin-corrected anion gap and strong ion gap; D: Agreement between albumin-corrected anion gap and strong ion gap. Panel B and D display the relationship between the mean value and the difference between both measurements. The lines indicate the mean difference between both parameters (bias) ± 2 SD (95% limits of agreement). Modified from Dubin et al[37].

Figure 5 Arterial pH, and bicarbonate levels in patients with severe hyperlactatemia. Values for (A) arterial pH, (B) PCO₂, and (C) bicarbonate ([HCO₃^-]) in patients with severe hyperlactatemia, with normal or low base excess. ^aP < 0.05 vs the other group.

Figure 6 Strong-ion difference, sodium-corrected chloride, albumin, and nonvolatile weak acid levels in severe hyperlactatemia patients. Values for (A) the effective strong-ion difference (SID_effective), (B) sodium-corrected chloride levels (Cl^-_corrected), (C) the albumin concentration, and (D) nonvolatile weak acid (Atot) levels in patients with severe hyperlactatemia, with normal or low base excess. ^aP < 0.05 vs the other group. SID_effective: Effective strong-ion difference.