Nonlinear Relationship between Early Postoperative Pulse Pressure Variation and Acute Kidney Injury Risk in Older...

Area of Science:

• Nephrology
• Cardiology
• Critical Care Medicine

Background:

• Acute kidney injury (AKI) is a common complication in older surgical intensive care unit (ICU) patients, increasing mortality and hospital stays.
• Traditional AKI detection methods (serum creatinine, urine output) often lead to delayed diagnosis.
• Pulse pressure variation (PPV) offers early hemodynamic insights but its association with AKI risk is unclear.

Purpose of the Study:

• To investigate the relationship between early postoperative PPV and AKI development in elderly cardiothoracic surgery patients.
• To identify potential nonlinear associations and optimal PPV thresholds for AKI risk prediction.
• To evaluate the predictive utility of PPV at 12 and 24 hours post-ICU admission.

Main Methods:

• Retrospective cohort analysis using MIMIC-IV and MIMIC-III databases.
• Inclusion of patients aged ≥60 years undergoing cardiothoracic surgery with available PPV data within 24 hours of ICU admission.
• Logistic regression and restricted cubic spline (RCS) modeling to assess PPV-AKI association, with AKI defined by KDIGO criteria.

Main Results:

• A U-shaped relationship was found between PPV at 12 hours (PPV₁₂h) and AKI risk (p=0.0224).
• The lowest AKI risk was observed at PPV₁₂h ≈ 0.14, associated with significant risk reduction in both primary and validation cohorts.
• PPV₁₂h demonstrated better predictive value for AKI than PPV at 24 hours (PPV₂₄h).

Conclusions:

• Early postoperative PPV exhibits a U-shaped correlation with AKI risk in older cardiothoracic surgery patients.
• A PPV₁₂h around 0.14 is consistently associated with the lowest AKI risk.
• Routine early PPV monitoring can aid hemodynamic assessment and potentially mitigate postoperative renal complications.