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Background <p>Cardiac surgery patients face significant postoperative risks. The albumin-corrected anion gap (ACAG) has emerged as a potential prognostic marker, but its role in predicting outcomes following cardiac surgery remains understudied. This study examined the association between preoperative ACAG levels and 28-day mortality following ICU admission in patients undergoing cardiac surgery.</p> Methods <p>This retrospective cohort study analyzed 5,006 cardiac surgery patients from the MIMIC-IV database. Patients were categorized based on ACAG levels: low (&lt; 12 mmol/L), normal (12–20 mmol/L), and high (&gt; 20 mmol/L). Hierarchical Cox proportional hazards models, restricted cubic spline (RCS) analysis, and exploratory mediation analysis were used to evaluate the association between preoperative ACAG and 28-day mortality following ICU admission. Incremental predictive analyses were additionally performed to assess whether ACAG improved the prognostic performance of models based on SOFA and SAPS II.</p> Results <p>Elevated ACAG levels (&gt; 20 mmol/L) were significantly associated with a heightened risk of 28-day mortality following ICU admission across all models. In the most comprehensively adjusted model, the hazard ratio was 1.049 (95% CI 1.024–1.075, <i>P</i> &lt; 0.001). ACAG demonstrated superior predictive value for 28-day mortality following ICU admission compared to the traditional anion gap (AUC 0.776 vs. 0.690). RCS revealed a nonlinear relationship, with mortality risk sharply increasing at ACAG levels above 20 mmol/L.In incremental predictive analyses, adding ACAG improved the prognostic performance of both SOFA- and SAPS II-based models. Exploratory mediation analyses suggested that SAPS II, GCS, and several electrolyte-related variables accounted for part of the observed association between preoperative ACAG and 28-day mortality.</p> Conclusions <p>Elevated preoperative ACAG levels were associated with increased 28-day mortality risk in cardiac surgery patients. Although part of this association may reflect overall illness severity and postoperative physiological stress, ACAG may serve as a useful early risk-stratification marker and could complement existing prognostic assessment frameworks. However, its causal role cannot be inferred from this observational study, and prospective studies are needed to validate these findings.</p>

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Association of preoperative albumin-corrected anion gap with 28-day mortality in cardiac surgery patients: a retrospective cohort study

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月27日

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  • Haiyang Hu,
  • Zhibo Zhang,
  • Wangping Peng,
  • Pengfei Du,
  • Wenkui Yu

摘要

Background

Cardiac surgery patients face significant postoperative risks. The albumin-corrected anion gap (ACAG) has emerged as a potential prognostic marker, but its role in predicting outcomes following cardiac surgery remains understudied. This study examined the association between preoperative ACAG levels and 28-day mortality following ICU admission in patients undergoing cardiac surgery.

Methods

This retrospective cohort study analyzed 5,006 cardiac surgery patients from the MIMIC-IV database. Patients were categorized based on ACAG levels: low (< 12 mmol/L), normal (12–20 mmol/L), and high (> 20 mmol/L). Hierarchical Cox proportional hazards models, restricted cubic spline (RCS) analysis, and exploratory mediation analysis were used to evaluate the association between preoperative ACAG and 28-day mortality following ICU admission. Incremental predictive analyses were additionally performed to assess whether ACAG improved the prognostic performance of models based on SOFA and SAPS II.

Results

Elevated ACAG levels (> 20 mmol/L) were significantly associated with a heightened risk of 28-day mortality following ICU admission across all models. In the most comprehensively adjusted model, the hazard ratio was 1.049 (95% CI 1.024–1.075, P < 0.001). ACAG demonstrated superior predictive value for 28-day mortality following ICU admission compared to the traditional anion gap (AUC 0.776 vs. 0.690). RCS revealed a nonlinear relationship, with mortality risk sharply increasing at ACAG levels above 20 mmol/L.In incremental predictive analyses, adding ACAG improved the prognostic performance of both SOFA- and SAPS II-based models. Exploratory mediation analyses suggested that SAPS II, GCS, and several electrolyte-related variables accounted for part of the observed association between preoperative ACAG and 28-day mortality.

Conclusions

Elevated preoperative ACAG levels were associated with increased 28-day mortality risk in cardiac surgery patients. Although part of this association may reflect overall illness severity and postoperative physiological stress, ACAG may serve as a useful early risk-stratification marker and could complement existing prognostic assessment frameworks. However, its causal role cannot be inferred from this observational study, and prospective studies are needed to validate these findings.