Admission Anion Gap Metabolic Acidosis and Its Impact on Patients in Medical Intensive Care Unit

Association between serum anion gap and 28-day mortality in critically ill patients with infective endocarditis: a retrospective cohort study from MIMIC IV database

BACKGROUND

The relationship between serum anion gap (AG) and 28-day mortality in critically ill patients with infective endocarditis is currently not well established.

OBJECTIVE

This study aims to investigate the impact of serum AG on 28-day mortality in critically ill patients with infective endocarditis.

METHODS

A retrospective cohort study was conducted involving 449 participants diagnosed with infective endocarditis and admitted to intensive care units (ICU). Vital signs, laboratory parameters and comorbidity were collected for all participants to analyze the association between anion gap levels and 28-day mortality.

RESULTS

A total of 449 critically ill patients with infective endocarditis (IE) were included in the study. The mean age was 57 years, and 64% were male. The overall 28-day mortality rate was 20%. A greater AG on admission were significantly associated with increased 28-day mortality in unadjusted analysis (hazard ratio [HR] 1.13; 95% confidence interval [CI] 1.09-1.18; p < 0.001). After adjusting for all confounders, the association remained significant (adjusted HR 1.07; 95% CI 1.02-1.13; p = 0.003). When AG was converted into categorial variables (quartiles), the risk of 28-day mortality in the greatest Q4 group was significantly higher compared with that in the lowest Q1 group (model 4: HR = 2.62, 95%CI: 1.17-5.83, p = 0.019). Subgroup analysis showed consistent results across different groups.

CONCLUSION

A greater AG on admission were independently associated with increased 28-day mortality in critically ill patients with IE. These findings suggest that the AG can serve as a prognostic marker in this population, aiding in risk stratification and guiding clinical management.

The association between anion gap and length of stay in patients undergoing hip fracture surgery: data from the MIMIC-IV database

OBJECTIVE

To explore the relationship between anion gap (AG) and length of stay (LOS) in patients undergoing hip fracture surgery.

METHODS

Clinical data of patients diagnosed with hip fracture and undergoing surgery were extracted from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Logistic regression analysis by adjusting different covariables and threshold effect analysis were used to analyze the relationship between AG and LOS. Subgroup analysis and interaction test were also performed to detect their relationship. Receiver Operating Characteristic (ROC) analysis was performed to identify the prediction performance and cutoff value of AG.Kaplan-Meier (KM) survival analysis was used to explore the influence of AG on overall survival.

RESULTS

A total of 1508 patients were enrolled and the median LOS was 4.9 days. The correlation between AG and LOS > 7 days was observed among 3 regression models when regarding AG as continuous variables (all OR > 1, all P < 0.05). After stratifying samples with AG quartiles, their relationship was only presented in the Q4 group both in model 1 and model 2 (all P < 0.001). The risk of LOS > 7 days gradually increased with increasing AG quartiles (all P for trend < 0.05). Further, threshold effect analysis found that their association was mainly observed when AG ≥ 14 mEq/L (OR = 1.122, P < 0.001). Subgroup analysis showed that their correlation was not influenced by sex, age, BMI, ethnicity, classification of fracture, therapeutic method, CHD, hypertension, osteoporosis, diabetes and admitted to the ICU (all P for interaction > 0.05). ROC analysis identified 14.5 as the cutoff value of AG for predicted LOS > 7 days. Survival analysis found that patients in the AG < 14.5 group had better overall survival.

CONCLUSION

In patients undergoing hip fracture surgery, the AG was positively correlated with LOS, and 14.5 mEq/L AG was the cutoff value for predicting LOS > 7 days. The cutoff value can favorably distinguish the survival difference of patients.

Association between the anion gap and mortality in critically ill patients with influenza: A cohort study

Introduction

Influenza is an important global health concern, particularly in critically ill patients. The anion gap, a marker of metabolic acidosis, is associated with mortality in various critical illnesses. However, its association with mortality in critically ill patients with influenza remains unclear. This study investigated the association between the anion gap on admission and 28-day mortality in critically ill patients with influenza.

Methods

A retrospective cohort study was conducted using data from MIMIC-IV database. Patients admitted to the intensive care unit (ICU) with influenza were included. The anion gap was measured within the first 24 h of ICU admission. The primary outcome was the 28-day mortality. The secondary outcomes were 60-day mortality and in-hospital mortality. Multivariable Cox regression was used to assess the association between the anion gap and mortality.

Results

A total of 276 critically ill patients with influenza were included in the study. The mean age was 65 years, and 60 % were male. The overall 28-day mortality was 15.5 %. A greater anion gap on admission was associated with significantly increased 28-day mortality in the unadjusted analysis (hazard ratio [HR], 1.11; 95 % confidence interval [CI], 1.03-1.2; p < 0.001). The association remained significant after adjusting for age, sex, race, and illness severity (adjusted HR, 1.09; 95 % CI, 1.02-1.17; p = 0.017). Subgroup analysis showed consistent results across the different groups.

Conclusion

A greater anion gap on admission was independently associated with increased 28-day mortality in critically ill patients with influenza. These findings suggest that the anion gap can be used as a prognostic marker in patients with influenza, aiding in risk stratification and guiding clinical management.

Association between Albumin-Corrected Anion Gap and Mortality in Patients with Cardiogenic Shock

Background

Cardiogenic shock (CS) is a critical illness with a high mortality rate in clinical practice. Although some biomarkers have been found to be associated with mortality in patients suffering from CS in previous studies. The albumin-corrected anion gap (ACAG) has not been studied in depth. Our study aimed to explore the relationship between ACAG and mortality in patients with CS.

Methods

All baseline data was extracted from Medical Information Mart for Intensive Care-IV version: 2.0 (MIMIC-IV). According to the prognosis at 30 days of follow-up, they were divided into survivors and non-survivors groups. The survival curves between the two groups were drawn using the Kaplan-Meier method and the log-rank test. Valid factors were selected using the least absolute shrinkage and selection operator (LASSO) logistic analysis model. Analysis was performed to investigate the relationship between mortality and all enrolled patients using restricted cubic spline (RCS) and Cox proportional hazards models. Receiver operating characteristic (ROC) curves were used to assess the predictive ability of ACAG. Evaluation of final result stability using sensitivity analysis.

Results

839 cases were selected to meet the inclusion criteria and categorized into survivors and non-survivors groups in the final analysis. The ACAG value measured for the first time at the time of admission was selected as the research object. Kaplan-Meier (K-M) survival curves showed that cumulative 30- and 90-day survival decreased progressively with elevated ACAG (p < 0.001), and multifactorial Cox regression analyses showed ACAG to be an independent risk factor for increased 30- and 90-day mortality in patients suffering from CS (p < 0.05). RCS curves revealed that all-cause mortality in this group of patients increased with increasing ACAG ( χ 2 = 5.830, p = 0.120). The ROC curve showed that the best cutoff value for ACAG for predicting 30-day mortality in patients with CS was 22.625, with a sensitivity of 44.0% and a specificity of 74.7%. The relationship between ACAG and CS short-term mortality remained stable in all sensitivity analyses (All p < 0.05).

Conclusions

The ACAG is an independent risk factor for 30- and 90-day mortality in CS patients and predicts poor clinical outcomes in CS patients. According to our study, elevated ACAG at admission, especially when ACAG > 20 mmol/L, was an independent predictor of all-cause mortality in CS.

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

Background

Serum anion gap (AG) has been proven to be associated with prognosis in critically ill patients. However, few studies have investigated the association between AG and all-cause mortality in critically ill patients with chronic obstructive pulmonary disease (COPD).

Objective

We hypothesized that the initial AG level would predict the mortality risk in critically ill patients with COPD.

Methods

This retrospective cohort study was based on the Medical Information Mart for Intensive Care (MIMIC) IV database. We extracted demographics, vital signs, laboratory tests, comorbidity, and scoring systems from the first 24 hours after patient ICU admission. Multivariable logistic regression analysis models were used to explore the association between serum AG levels and mortality. Interaction and stratified analyses were conducted including age, gender and comorbidity.

Results

A total of 5531 critically ill patients with COPD were enrolled, composed of 53.6% male and 46.4% female with a median age of 73 years. The all-cause mortality of these patients during ICU hospitalization was 13.7%. The risk of all-cause mortality increased as the AG level increased in the univariate logistic regression analysis (OR=1.13, 95% CI: 1.11-1.15, p<0.01). After adjusting for all the covariates in multivariate logistic regression analysis, the odds ratio was 1.06 (95% CI: 1.04-1.09, p<0.01). Compared with the lowest AG group Q1 (≤11mmol/L), the adjusted OR value for AG and mortality in Q2 (12-13mmol/L) was 0.89 (95% CI: 0.63-1.25, p=0.502), Q3 (14-15mmol/L) was 0.95 (95% CI: 0.68-1.34, p=0.788), and Q4 (≥16mmol/L) was 1.49 (95% CI: 1.10-2.02, p=0.009) respectively. In addition, the results of the subgroup and stratified analyses were robust.

Conclusion

AG is positively related to all-cause mortality in critically ill patients with COPD.

Relationship between anion gap and in-hospital mortality in intensive care patients with liver failure: a retrospective propensity score matching analysis

OBJECTIVES

To elucidate the association between anion gap (AG) and in-hospital mortality in intensive care patients with liver failure.

METHODS

Demographic and clinical characteristics of intensive care patients with liver failure in the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database were collected, and binomial logistic and Cox regression was conducted to investigate the association between AG and in-hospital mortality. The area under the receiver operating characteristic (ROC) curve (AUC) was conducted to characterize the performance of AG in predicting in-hospital mortality, and was compared with the albumin corrected anion gap (ACAG) and the End-Stage Liver Disease (MELD) score. The Kaplan-Meier curve was plotted for in-hospital survival analysis of AG and patients with liver failure. The propensity score matching (PSM) analysis was performed to mitigate selection bias.

RESULTS

AG was an independent risk factor for in-hospital mortality in intensive care patients with liver failure. Before PSM, the AUCs of AG, ACAG, and MELD were 0.666, 0.682, and 0.653, respectively. After PSM, the AUCs of AG, ACAG, and MELD scores were 0.645, 0.657, and 0.645, respectively, and there is no difference in the predictive performance of the three indicators upon comparison. Compared with the low-AG (≤20 mmol/L) group, the hazard ratio (HR) for in-hospital death of the high-AG (>20 mmol/L) group was determined to be 2.1472 (before PSM)/1.8890 (after PSM).

CONCLUSIONS

AG is associated with in-hospital mortality in intensive care patients with liver failure and demonstrates a moderate predictive value, which is comparable to the predictive power of the MELD score. AG may serve as an indirect marker of in-hospital mortality of patients with liver failure by reflecting the degree of metabolic acidosis.

Association between albumin corrected anion gap and all-cause mortality in critically ill patients with acute kidney injury: a retrospective study based on MIMIC-IV database

BACKGROUND

The early identification of patients at high risk for acute kidney injury (AKI) with a poor prognosis is crucial to prevent complications and minimize mortality. This study sought to investigate the association between albumin-corrected anion gap (ACAG) and all-cause mortality among critically ill patients with AKI.

METHODS

All eligible AKI patients from the Medical Information Mart for Intensive Care IV (MIMIC-IV version 2.0) database were considered for participation in this study. We employed Kaplan-Meier curves to assess the 30-d and 360-d cumulative survival rates among various groups. Flexibly visualizing the connection between ACAG and mortality, we utilize restricted cubic splines (RCS) and multivariate Cox regression models. Result robustness underwent assessment through subgroup analyses and sensitivity analyses. Receiver-operating characteristic (ROC) curves were generated to evaluate the predictive performance of ACAG.

RESULTS

The study included 9625 AKI participants, of whom 58.60% were male, and the 360-d all-cause mortality rate was 39.89%. According to Kaplan-Meier analysis, the 30-d and 360-d cumulative survival rates for AKI patients were significantly lower in the high ACAG group than in the normal ACAG group. RCS analysis indicated that ACAG levels had a non-linear correlation with the risk of 30-d and 360-d mortality for AKI patients. Cox regression analysis demonstrated that ACAG is an independent risk indicator for 30-d and 360-d prognosis in AKI patients in the ICU.

CONCLUSIONS

Elevated ACAG levels (> 20 mmol/L) at ICU admission were associated with 30-d and 360-d all-cause mortality in critically ill patients with AKI.

The relationship between albumin corrected anion gap levels and mortality in patients with asthma in the ICU

Although previous studies have suggested that albumin-corrected anion gap (ACAG) may be a predictor of mortality in critically ill patients in intensive care unit (ICU), its utility in the context of asthma has not been definitively established. In this study, baseline data, albumin concentration, anion gap (AG) and 30-d mortality data were retrieved from the Medical Information Mart for Intensive Care IV database (MIMIC-IV) for patients with asthma in the intensive care unit. Receiver operating characteristic (ROC) curves were constructed to analyze the predictive ability of ACAG and AG. The risk of 30-day mortality among patients with ACAG and asthma was analyzed using a restricted cubic spline (RCS) plot. Decision curve analysis (DCA) was used to evaluate the clinical usefulness of ACAG as a prognostic factor for 30-day mortality. Subsequently, subgroup analysis was conducted to explore potential variations in the relationship between ACAG and 30-day mortality based on factors such as sex, age, whether the asthma was acute, and other co-morbidities. Our study reveals that ACAG is a significant independent predictor of 30-day mortality in asthmatic patients receiving intensive care. The area under the AUC curve for ACAG was found to be 0.703, which is higher than that of AG, indicating that ACAG has a better predictive ability for 30-day mortality in this population. Furthermore, higher levels of ACAG were found to be associated with increased risk of 30-day mortality in asthmatic patients. In addition, decision curve analysis (DCA) demonstrated that the net benefit of ACAG was greater than that of AG. These findings suggest that ACAG may be a valuable prognostic factor for predicting 30-day mortality in asthmatic patients in the ICU. Our study provides evidence that ACAG is associated with an increased risk of 30-d mortality and has better predictive value in patients with combined asthma who are admitted to the ICU than AG.

The association between acid-base status and clinical outcome in critically ill COVID-19 patients admitted to intensive care unit with an emphasis on high anion gap metabolic acidosis

OBJECTIVE

The aim of this study was to identify arterial blood gas (ABG) abnormalities, with a focus on a high anion gap (AG) metabolic acidosis and evaluate outcomes in coronavirus disease 2019 (COVID-19) patients admitted to the ICU.

METHODS

A retrospective, observational study was conducted in a tertiary hospital in Cape Town during the first and second COVID-19 waves. Age, gender, sodium (Na), potassium (K), chloride (Cl), bicarbonate (HCO₃std), pH, partial pressure of carbon dioxide (pCO₂), creatinine, estimated glomerular filtration rate (eGFR), lactate levels and ABG results were obtained. The Pearson χ2 test or Fisher exact test and the Wilcoxon rank-sum test were used to compare mortality and survival. To identify factors associated with non-survival, a multivariable model was developed.

RESULTS

This study included 465 patients, 226 (48%) of whom were female. The sample population's median (IQR) age was 54.2 (46.1-61.3) years, and 63% of the patients died. ABG analyses found that 283 (61%) of the 465 patients had alkalosis (pH ≥ 7.45), 65 (14%) had acidosis (pH ≤ 7.35) and 117 (25%) had normal pH (7.35-7.45). In the group with alkalosis, 199 (70.3%) had a metabolic alkalosis and in the group with acidosis, 42 (64%) had a metabolic acidosis with an increased AG of more than 17. Non-survivors were older than survivors (56.4 years versus 50.3 years, p < .001).

CONCLUSION

Most of the COVID-19 patients admitted to the ICU had an alkalosis, and those with acidosis had a much worse prognosis. Higher AG metabolic acidosis was not associated with patients' characteristics.

The association between albumin corrected anion gap and ICU mortality in acute kidney injury patients requiring continuous renal replacement therapy

The relationship between albumin corrected anion gap (ACAG) and mortality in acute kidney injury (AKI) patients who received continuous renal replacement therapy (CRRT) has not been investigated in any previous studies. This study aimed to investigate the relationship between ACAG at CRRT initiation and all-cause mortality among these patients in the intensive care unit (ICU). Patients diagnosed with AKI and treated with CRRT in the ICU from the Medical Information Mart for Intensive Care-IV version 1.0 (MIMIC IV) database and Huzhou Central Hospital were retrospectively enrolled. Participants were divided into two groups: the normal ACAG group (12-20 mmol/L) and high ACAG group (> 20 mmol/L). The Kaplan-Meier method and log-rank test were used to compare the survival rate between the two groups. Restricted cubic spine (RCS) and Cox proportional-hazards models were utilized to analyze the relationship between ACAG at CRRT initiation and ICU all-cause mortality of these patients. A total of 708 patients met the inclusion criteria in the study. The all-cause mortality of these patients during ICU hospitalization was 41.95%. Patients in the high ACAG group exhibited significantly higher ICU all-cause mortality rate than patients in the normal ACAG group (all P < 0.001). The Kaplan-Meier survival curves showed that the normal ACAG group had a higher ICU cumulative survival rate than the high ACAG group (log-rank test, χ₁²= 13.620, χ₂² = 12.460, both P < 0.001). In the multivariate COX regression analyses, patients with higher ACAG (> 20 mmol/L) levels at the time of CRRT initiation in the MIMIC IV database and Huzhou Central Hospital were significantly correlated with ICU all-cause mortality after adjusting multiple potential confounding factors with hazard ratios of 2.852 (95% CI 1.718-4.734) and 2.637(95% CI 1.584-4.389), respectively. In critically AKI patients who undergo CRRT, higher ACAG (> 20 mmol/L) level at the initiation of CRRT was significantly correlated with ICU all-cause mortality. Therefore, clinicians should pay more attention to those patients with a higher ACAG value.