Renoprotective Postoperative Monitoring: What Is the Best Method for Computing Renal Perfusion Pressure? An...

Low mean arterial pressure (MAP) is a well-known risk factor for postoperative acute kidney injury (AKI), but probably it is not the sole hemodynamic parameter that can influence the development of renal failure. There are data in cardiac patients supporting the role of renal venous congestion in the development of AKI. The aim of our study was to determine a combination of factors best predicting the development of AKI.

Data were collected prospectively for adult patients admitted after major abdominal surgery to 9 Hungarian intensive care units. Hemodynamic and laboratory parameters were compared in patients with AKI vs. no-AKI at the time of admission. Renal perfusion was computed by different methods from hemodynamic measurements involving MAP, central venous pressure (CVP), intraabdominal pressure (IAP), and mean airway pressures (Pmean). Twelve different, clinically interpretable equations were tested. Statistical evaluation was performed by the Mann-Whitney U test and ROC analysis.

Eighty-four patients were enrolled in the study. Renal perfusion pressure was significantly lower in all equations. The equations MAP-IAP-Pmean (1-area under the curve [AUC]: 0.796; likelihood ratio [LR]+: 3.520; LR-: 0.337; p < 0.01), MAP-IAP-CVP-Pmean (1-AUC: 0.794; LR+: 2.743; LR-: 0.282; p < 0.01), and MAP-2 × IAP-CVP-Pmean (1-AUC: 0.791; LR+: 4.321; LR-: 0.262; p < 0.001) showed small to moderate effect on AKI but have better performance than severity score systems (SAPS II [AUC: 0.696; LR+: 3.143, LR-: 0.433; p < 0.01], SOFA [AUC: 0.717; LR+: 2.089; LR-: 0.528; p < 0.001]).

We found that the best parameter predicting AKI is the MAP-2 × IAP-CVP-Pmean. Further investigation is needed to analyze the role of CVP and Pmean, and to characterize renal venous congestion and tubular pressure more in detail.