Prognostic role of unmeasured anions determined by the Stewart approach in septic shock: A prospective cohort study

Abstract

Background: Unlike standard methods for the analysis of acid-base disturbances, the Stewart approach allows for a precise quantification of unmeasured anions (strong ion gap, SIG). The prognostic value of these unmeasured anions has been reported in various clinical situations in the intensive care unit (ICU), but not specifically in septic shock. The aim of the present study was to assess whether or not the SIG could be a prognostic marker for 28-day mortality in critically ill patients admitted to the ICU for septic shock. Methods: This prospective cohort study was conducted from June 2016 to December 2017 in three ICUs of a French teaching hospital. All patients admitted to the ICU for septic shock and equipped with an arterial blood line were eligible. Oral consent was collected after delivering oral and written information to the patient or his/her family. The SIG was calculated from a complete blood sampling (blood electrolytes and arterial blood gas) collected immediately upon ICU admission. Receiver operating characteristics (ROC) curves were determined to assess the ability of SIG to predict 28-day mortality. Results: A total of 116 patients were analyzed. The 28-day mortality rate was 41.4%. Median (interquartile range [IQR]) SIG at admission was 7.1 (4.6-9.6) mEq/L for the 28-day survivors and 8.0 (6.1-10.3) mEq/L for non-survivors (P = 0.051). The area under ROC of SIG at admission for 28-day mortality prediction was 0.607 (95% confidence interval [CI] 0.504-0.710; P = 0.051). Conclusion: SIG is not a relevant prognostic marker for mortality in septic shock.