Related Experiment Video
Updated: May 27, 2026

Technical Refinement of a Bilateral Renal Ischemia-Reperfusion Mouse Model for Acute Kidney Injury Research
Published on: November 3, 2023
Hidden renal dysfunction causes increased in-hospital mortality risk after coronary artery bypass graft surgery
Mathias Alexandre Volkmann1, Paulo Eduardo Ballvé Behr, Jayme Eduardo Burmeister
1Universidade Luterana do Brasil, Canoas, RS, Brasil.
Insights
Patients undergoing cardiac surgery with normal serum creatinine may still have impaired kidney function. This subgroup faces double the mortality risk and longer hospital stays, highlighting the need for better renal assessment.
Area of Science:
- Nephrology
- Cardiology
- Surgical Outcomes
Background:
- Preoperative chronic kidney dysfunction is a significant predictor of mortality in cardiac surgery patients.
- Serum creatinine levels within the normal range do not always reflect normal renal function.
- Assessing renal function beyond serum creatinine is crucial for accurate risk stratification.
Purpose of the Study:
- To compare mortality rates, total hospital stay, and post-surgical hospital stay in cardiac surgery patients with normal serum creatinine but varying levels of estimated creatinine clearance.
- To identify patients with potentially undetected renal dysfunction despite normal serum creatinine levels.
- To evaluate the impact of impaired renal function, defined by creatinine clearance, on outcomes after coronary artery bypass surgery.
Main Methods:
- Utilized data from 4,765 patients undergoing coronary artery bypass surgery (January 1996 - June 2004).
- Estimated creatinine clearance using the Cockroft-Gault equation.
- Defined impaired renal function as creatinine clearance <60 mL/min/1.73 m² (National Kidney Foundation-USA chronic kidney disease stage 3).
- Compared in-hospital mortality, total hospital stay, and post-surgical hospital stay between groups.
Main Results:
- Analyzed data from 4,688 patients; 4,403 had serum creatinine < 1.5 mg/dL.
- Within the normal serum creatinine group, 1,226 patients (Group B) had creatinine clearance <60 mL/min, compared to 3,177 (Group A) with clearance >60 mL/min.
- Group B patients experienced significantly longer total hospital stays (2.85 days more) and post-surgical stays (1.79 days more) (P < 0.0001).
- Group B had a 2.09 times higher relative risk of in-hospital death (95% CI: 1.54-2.84) compared to Group A.
Conclusions:
- Over 25% of patients with serum creatinine < 1.5 mg/dL exhibited creatinine clearance <60 mL/min.
- This significant proportion of patients with undetected renal dysfunction faced double the mortality risk.
- These findings underscore the inadequacy of serum creatinine alone for assessing renal function in cardiac surgery candidates and highlight the importance of estimated creatinine clearance for predicting outcomes.
Introduction And Objectives:
Preoperative chronic renal dysfunction is an independent predictor of mortality in cardiac surgery. As normal range serum creatinine is not representative of normal renal function, we compared mortality rates, total hospital stay and post-surgical hospital stay for patients who underwent isolated coronary artery bypass surgery with serum creatinine < 1.5mg/dL as to their estimated creatinine clearance, normal or impaired.
Methods:
In 4,765 patients submitted to coronary artery bypass surgery between January/1996 and June/2004, the creatinine clearance was estimated by the Cockroft-Gault equation. Impaired renal function was considered as a creatinine clearance <60 mL/min/1.73 m² (chronic renal disease stage 3 - National Kidney Foundation-USA). In hospital mortality, total hospital stay, and post-surgical hospital stay were compared.
Results:
4,688 patients had the required data, and 4,403 presented serum creatinine < 1.5 mg/dL - 3,177 with creatinine clearance > 60 mL/min (Group A), and 1,226 with <60 mL/min (Group B). Group B patients had significantly higher total hospital stay and post-surgical hospital stay than those in Group A (respectively 2.85 and 1.79 more days--P < 0.0001). Relative risk of in-hospital death was 2.09 to Group B (95%CI:1.54-2.84) when compared to Group A.
Conclusions:
More than one quarter of the patients with serum creatinine <1.5 mg/dL had creatinine clearance <60 mL/min. This expressive number of patients, that would not have their renal dysfunction detected by the serum creatinine parameter alone, had double the risk of death, longer total hospital stay and post-surgical hospital stay than the other patients with serum creatinine < 1.5mg/dL.
Related Concept Videos
Cardiac Catheterization I: Pre-Procedure Overview
Acute Kidney Injury IV: Diagnostic Studies and Prevention
Kidney Transplant II: Surgical Procedure
Kidney Transplant III: Nursing Management
Heart Failure Drugs: Diuretics
Acute Kidney Injury I: Introduction
