Effects of preoperative high-oral protein loading on short- and long-term renal outcomes following cardiac surgery: a cohort study

Abstract Background Post-cardiac surgery acute kidney injury (AKI) is associated with increased mortality. A high-protein meal enhances the renal blood flow and glomerular filtration rate (GFR) and might protect the kidneys from acute ischemic insults. Hence, we assessed the effect of a preoperative high-oral protein load on post-cardiac surgery renal function and used experimental models to elucidate mechanisms by which protein might stimulate kidney-protective effects. Methods The prospective “Preoperative Renal Functional Reserve Predicts Risk of AKI after Cardiac Operation” study follow-up was extended to postoperative 12 months for 109 patients. A 1:2 ratio propensity score matching method was used to identify a control group (n = 214) to comparatively evaluate the effects of a preoperative protein load and standard care. The primary endpoints were AKI development and postoperative estimated GFR (eGFR) loss at 3 and 12 months. We also assessed the secretion of tissue inhibitor of metalloproteases-2 (TIMP-2) and insulin-like growth factor–binding protein 7 (IGFBP7), biomarkers implicated in mediating kidney-protective mechanisms in human kidney tubular cells that we exposed to varying protein concentrations. Results The AKI rate did not differ between the protein loading and control groups (13.6 vs. 12.3%; p = 0.5). However, the mean eGFR loss was lower in the former after 3 months (0.1 [95% CI − 1.4, − 1.7] vs. − 3.3 [95% CI − 4.4, − 2.2] ml/min/1.73 m2) and 12 months (− 2.7 [95% CI − 4.2, − 1.2] vs − 10.2 [95% CI − 11.3, − 9.1] ml/min/1.73 m2; p