No abstract

Introduction: Acute kidney injury (AKI) is a serious complication of cardiac surgery. The current ‘gold standard’ for determining AKI is change in serum creatinine and urine output, however, this change occurs relatively late after the actual injury occurs. Identification of new biomarkers that detect early AKI is required. Recently, new biomarkers, such as the NephroCheck® Test and AKIRisk have also been tested and found to be good indicators of AKI. Neutrophil gelatinase-associated lipocalin (NGAL) has shown promise in paediatric patients but has displayed varied results in adult populations, particularly post cardiac surgery. The aim of this study was to assess the value of urinary NGAL as a biomarker of AKI in patients with pre-existing renal impairment (eGFR >15ml/min to eGFR<60ml/min). Methods: A post-hoc analysis of urinary NGAL concentrations from 125 patients with pre-existing kidney impairment, who participated in a randomised trial of haemofiltration during cardiac surgery, was undertaken. Urinary NGAL was measured using ELISA at baseline, post-operatively and 24 and 48 hours after surgery, and serum creatinine was measured pre and postoperatively and then at 24, 48, 72 and 96 hours as routine patient care. NGAL concentrations were compared in patients with and without AKI determined by changes in serum creatinine concentrations. A Kaplan-Meier plot compared survival for patients with or without AKI and a Cox proportional hazards analysis was performed to identify factors with the greatest influence on survival. Results: Following surgery, 43% of patients developed AKI (based on KDIGO definition). Baseline urinary NGAL was not found to be significantly different between patients that did and did not develop AKI. Urinary NGAL concentration was increased in all patients following surgery, regardless of whether they developed AKI and was also significant between groups at 24 (p=0.003) and 48 hours (p<0.0001). Urinary NGAL concentrations at 48 hours correlated with serum creatinine concentrations at 48 hours (r=0.477, p<0.0001), 72 hours (r=0.488, p<0.0001) and 96 hours (r=0.463, p<0.0001). Urinary NGAL at 48 hours after surgery strongly predicted AKI (AUC=0.76; P=0.0001). A Kaplan- Meier plot showed that patients with postoperative AKI had a significantly lower 7-year survival compared with those without AKI. Postoperative urinary NGAL at 48 hours >156ng/mL also strongly predicted 7-year survival. However, additive EuroSCORE, age, current smoking and post-operative antibiotics usage were distinctly significantly more predictive of 7-year survival as compared with postoperative urinary NGAL at 48 hours >156ng/mL. Conclusions: Our study demonstrated that postoperative urinary NGAL levels at 48 hours postsurgery strongly predicts the onset or severity of postoperative AKI based on KDIGO classification in patients with preoperative kidney impairment and were also strongly related to 7-year survival.

No abstract

Acute exercise can result in temporary decrease in endothelial function, which may represent a transient period of risk. Numerous mechanisms underpin these responses included release of extracellular vesicles (EVs) derived from apoptotic or activated endothelial cells and platelets. This study aimed to compare the time-course of endothelial responses to two exercise protocols: moderate-intensity-continuous-exercise (MICE) and high-intensity-interval-exercise (HIIE) and the associations with EV release. Eighteen young healthy males (age: 22.6±3.7y, BMI: 25.6±2.5m2/kg, VO2peak: 38.6±6.5ml/kg/min) completed two randomly assigned exercises; HIIE (10x1min-@-90% heart rate reserve (HRR), 1min passive recovery) or MICE (30min-@-70% HRR) on a cycle ergometer. FMD was used to assess endothelial function and blood samples were collected to evaluate endothelial cell-derived EV (CD62E+) and platelet-derived EV (CD41a+), prior- and 10, 60, and 120min post-exercise. There were similar increases, but different time-courses (P=0.017) in FMD (increased 10min post-HIIE, P<0.0001 and 60min post-MICE, P=0.038). CD62E+ remained unchanged (P=0.530), whereas overall CD41a+ release was reduced 60min post-exercise (P=0.040). FMD was not associated with EV absolute release or change (P>0.05). Acute exercise resulted in similar improvements, but different time-course in FMD following either exercise. Whilst EVs were not associated with FMD, the reduction in platelet-derived EVs may represent a protective mechanism following acute exercise.