Balanced forced-diuresis compared to control as a reno-protective approach in cardiac surgery: secondary outcome of a randomized controlled trial, assessment of neutrophil gelatinase-associated lipocalin levels

Background: Neutrophil gelatinase-associated lipocalin (NGAL) is a recognised biomarker for acute kidney injury (AKI).This study investigated the impact of balanced forced-diuresis using RenalGuard® system (RG), in reducing acute kidney injury (AKI) rates and the associated NGAL levels (6-h post-CPB plasma level) post adult cardiac surgery with cardiopulmonary bypass (CPB). Methods: Patients included in the study were at high-risk for AKI post cardiac surgery, namely history of diabetes and/or anaemia, e-GFR 20–60 ml/min/1.73 m2, Logistic EuroScore > 5, anticipated CPB time > 120 min. Patients were randomized to either RG (n = 110) or managed as per current practice (control = 110). RIFLE-defined AKI rate (based on serum creatinine level increase) within first 3 days of surgery and 6-h post CPB NGAL levels were the primary and secondary end-points. Results: Pre and intra-operative characteristics between the two groups were similar (p > 0.05) including the pre-op NGAL levels, the oxygen delivery (ecDO2i) and the carbon dioxide production (ecVCO2i) during CPB. Patients in the RG group had a significantly lower post-operative RIFLE-defined AKI rate compared to control (10% (11/110) v/s 20.9% (23/110), p = 0.03). Overall, median 6-h post CPB NGAL levels in patients with AKI were significantly higher than those who did not develop AKI (211 vs 150 ng/ml, p < 0.001). Patients managed by balanced forced-diuresis had lower post-operative NGAL levels (146 vs 178 ng/ml, p = 0.09). Using previously reported NGAL cut-off level for AKI (142 ng/ml), binary logistic regression analysis confirmed a beneficial effect of the RG system, with an increased risk of AKI of 2.2 times in the control group (OR 2.2, 95% CI 1.14–4.27, p = 0.02). Conclusions: Overall, the 6-h post-CPB plasma NGAL levels were significantly higher in patients who developed AKI. Patients managed with the novel approach of balanced forced-diuresis, provided by the RenalGuard® system, had a lower AKI rate and lower NGAL levels indicating a lesser degree of renal tissue injury. Trial registration ClinicalTrials.gov website, NCT02974946, https://clinicaltrials.gov/ct2/show/NCT02974946.