The association between cardiac surgery - associated acute kidney injury and elevated liver function tests. A...

Acute kidney injury after cardiac surgery (CSA-AKI) is common and associated with worse outcome. Venous congestion contributes to CSA-AKI and liver dysfunction. We hypothesized that elevated liver enzymes may serve as early markers for CSA-AKI.

In a single-center cohort study we included adult cardiac surgery patients during a 6-year period. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured at ICU admission, 12 h and 24 h. The primary objective was to assess whether liver enzymes at ICU admission, normalized to their upper limits of normal (ULN), predicted CSA-AKI. Secondary outcomes included prediction of CSA-AKI severity, use of renal replacement therapy (RRT), and the association between central venous pressure (CVP) and liver enzymes.

Among 3415 patients, 65.4% developed CSA-AKI, 37.4% had AKI stage ≥2 and 3.8% received RRT. AST/ULN and ALT/ULN at ICU admission predicted CSA-AKI [AUC-ROC (95% CI; resp. 0.587 (0.570-0.604); 0.534 (0.517-0.551); both p < 0.001)], with AST performing better (p < 0.001). The discriminating power of AST/ULN and ALT/ULN at ICU admission for AKI ≥2 were respectively AUC-ROC (95% CI); 0.594 (0.577-0.610) and 0.541 (0.524-0.585) (both p < 0.001). AST/ULN 12 h after ICU admission was the strongest predictor for RRT [AUC-ROC (95% CI; 0.751 (0.733-0.768); p < 0.001)], with a 4-fold increased RRT risk when AST exceeded 1.6 times the ULN. AST and ALT 24 h post ICU admission were weakly associated with CVP (respectively: R² = 0.007; p = 0.003 and ALT: R² = 0.006; p = 0.004).

AST activity may have potential as a predictor of CSA-AKI and use of RRT, although liver enzymes demonstrated a weak association with CSA-AKI.