Haematocrit During Cardiopulmonary Bypass and Risk for Acute Kidney Injury: An Observational Single-Centre Study

Area of Science:

• Cardiovascular Surgery
• Nephrology
• Critical Care Medicine

Background:

• Low hematocrit during cardiopulmonary bypass is a known risk factor for acute kidney injury (AKI).
• The impact of high hematocrit on AKI risk remains less understood.
• Identifying an optimal hematocrit range may reduce postoperative complications.

Purpose of the Study:

• To investigate the association between hematocrit levels and the risk of acute kidney injury (AKI) in cardiac surgery patients.
• To determine if a specific hematocrit range is associated with reduced AKI risk.
• To analyze the impact of hematocrit exposure during aortic cross-clamp on postoperative kidney function.

Main Methods:

• Observational study of 3798 cardiac surgery patients (2016-2020) using registry data.
• AKI defined as serum-creatinine increase >1.5x baseline or renal replacement therapy initiation.
• Weighted hematocrit exposure calculated based on time and magnitude above/below thresholds.
• Multivariable logistic regression adjusted for established AKI risk factors.

Main Results:

• Postoperative AKI occurred in 15.7% of patients.
• A non-linear association was observed between hematocrit exposure and AKI risk.
• Hematocrit below 25% (aOR 1.006 per 1 [%×min]) and above 38% (aOR 1.006 per 1 [%×min]) during aortic cross-clamp were associated with increased AKI risk.

Conclusions:

• Hematocrit levels outside the 25%-38% range during aortic cross-clamp are associated with increased postoperative AKI risk.
• These findings suggest a potential optimal hematocrit range for cardiac surgery.
• Further research is warranted to validate these results and guide clinical practice.