Stewart's Approach for Acid-base Disorders: Does the Strong Ion Difference and Effects Have an Impact on Intensive Care Unit Mortality?

Objective: The diagnosis and treatment of electrolyte and acid-base imbalances in intensive care unit (ICU) patients have critical importance. The value of Stewart's approach in revealing acid-base disorders is known. There are parameters defined according to this approach. This study investigates the impact of the chloride effect (Cl-Effect), sodium effect (Na-Effect), sodium-chloride effect (Na-Cl-Effect), strong ion difference (SIDnl) and Cl/Na ratio values calculated according to Stewart's approach on ICU mortality. Materials and Methods: Two thousand patients whose Na, Cl, K, standard base excess (SBE), pH values were recorded and SIDnl, Cl-Effect, Na-Effect, Na-Cl-Effect, Acute Physiology Assessment and Chronic Health Evaluation-II (APACHE-II) and Sequential Organ Failure Assessment (SOFA) scores calculated are included in this study. Cl-Effect, Na-Effect, Na-Cl-Effect, SIDnl, Cl/Na ratio values were evaluated with a multivariable logistic regression model in terms of ICU mortality. Results: Abnormal ranges of SIDnl (SIDnl <30 or SIDnl =43) were significantly increased in nonsurvivors than survivors (p=0.026). Cl-Effect, Na-Effect, Na-Cl-Effect, Cl/Na ratio and their percentages of abnormal ranges were similar between survivor and non-survivor patients. In the multivariate logistic regression model, the likelihood of mortality was 3.5-fold (2.9-4.3), 1.7-fold (1.4-2.1) and 1.2-fold (1.0-1.5) increased by APACHE-II >= 26, SOFA >7, and SIDnl <30 or SIDnl >= 43 (p<0.001, p<0.001, p=0.041, respectively). Conclusion: SIDnl is associated with ICU mortality, but pH, SBE, Cl-Effect, Na-Effect, Na-Cl-Effect and Cl/Na ratio is not. SIDnl is one of the independent variables of Stewart's approach and is a valuable parameter in blood gas evaluations.