Relationship of Admission Serum Anion Gap and Prognosis of Critically Ill Patients: A Large Multicenter Cohort Study

Abstract

Background. There were controversies over the relationship between Anion gap (AG) and mortality in critically ill patients. Therefore, a large multicenter cohort study was conducted to evaluate the association of AG and mortality in large-scale intensive care units (ICUs) patients. Methods. This retrospective cohort study included adult ICU patients enrolled from eICU Collaborative Research Database. According to initial serum AG upon ICU admission, patients were divided into three groups: AG < 8 mmol / L , 8 ≤ AG ≤ 16 mmol / L , and AG > 16 mmol / L . Logistic regression models were built to investigate the association between serum AG and ICU and hospital mortalities. Serum AG was added into Acute Physiology and Chronic Health Evaluation (APACHE) IV score and the model discrimination was assessed by the area under the curve (AUC) of receiver operating characteristic curves. The relationship between serum AG and mortalities in patients with different acid-base status and serum lactate were also evaluated. An external validation was performed with the Critical care database comprising patients with infection at Zigong Fourth People’s Hospital. Results. A total of 8520 patients entered the final cohort. There are 42 patients with serum AG < 8 mmol / L , 3238 patients with 8 ≤ AG ≤ 16 mmol / L , and 5240 patients with AG > 16 mmol / L . Serum AG > 16 mmol / L is related with increased ICU mortality (odds ratio [OR], 1.530; 95% confidence interval [CI], 1.305–1.794) and hospital mortality (OR, 1.618; 95% CI, 1.415–1.849), compared with 8 ≤ AG ≤ 16 mmol / L . Adding Serum AG to APACHE IV score could statistically improve the prediction of ICU (0.770 [0.761–0.779] to 0.774 [0.765–0.783], P = 0.001 ) and hospital mortalities (0.756 [0.747–0.765] to 0.761 [0.751–0.770], P = 0.012 ). The associations between serum AG and mortalities remain robust in patients with different acid-base statuses and serum lactate. The findings are validated in the external cohort. Conclusions. Initial serum AG > 16 mmol / L after ICU admission is associated with increased mortality in critically ill patients.

Albumin Corrected Anion Gap and the Risk of in-Hospital Mortality in Patients with Acute Pancreatitis: A Retrospective Cohort Study

“…AG, as a biomarker for assessing the acid–base of the biotic internal environment, is associated with higher in-hospital mortality in patients presenting with cardiac arrest and sepsis; 7 , 8 with higher ICU and in-hospital mortality in critically ill patients. 9 An elevated level of AG increases all-cause mortality in unselected adults. 10 Moreover, AG can predict short-time prognosis for cerebral infarction patients.…”

“… 24 There is controversy on the relevance between AG and lactate. Some research found AG was related to lactate, 7 , 9 while some insisted that AG cannot predict hyperlactatemia 25 and the use of AG as an alternative to lactate cannot be recommended. 26 The possible reason results from the various baseline AG levels, albumin levels, clinical setting among individuals, and differences between arterial, venous, and capillary lactate.…”

Association Between Serum Anion Gap and Mortality in Critically Ill Patients with COPD in ICU: Data from the MIMIC IV Database

“… 16 AG is commonly used to evaluate acid-base disorders and analyze primary metabolic acidosis. 6 High AG metabolic acidosis is a subcategory of metabolic acidosis, 9 and therefore, AG may be a useful predictor of adverse clinical outcomes in ICU patients. 17 Recent retrospective studies have shown that elevated AG is associated with increased mortality in ICU patients with aortic aneurysm, 7 AKI requiring CRRT, 9 cardiogenic shock, 10 acute pancreatitis 11 and hip fractures.…”

“…AG is used to detect acid-base disorders and analyze the primary metabolic acidosis. 6 Recent studies have shown that a high AG level is associated with increased mortality in ICU patients with conditions such as aortic aneurysm, 7 sepsis, 8 acute kidney injury(AKI) requiring continuous renal replacement therapy(CRRT), 9 cardiogenic shock, 10 acute pancreatitis 11 and hip fractures. 12 However, few studies have investigated the association between AG and all-cause mortality in critically ill patients with COPD.…”