Acute Kidney Injury following Cardiopulmonary Bypass: A Challenging Picture

Cardiac Surgery-Associated Acute Kidney Injury

AKI is a common and serious complication of cardiac surgery that has a significant impact on patient morbidity and mortality. The Kidney Disease Improving Global Outcomes definition of AKI is widely used to classify and identify AKI associated with cardiac surgery (cardiac surgery-associated AKI [CSA-AKI]) on the basis of changes in serum creatinine and/or urine output. There are various preoperative, intraoperative, and postoperative risk factors for the development of CSA-AKI which should be recognized and addressed as early as possible to expedite its diagnosis, reduce its occurrence, and prevent or ameliorate its devastating complications. Crucial issues are the inaccuracy of serum creatinine as a surrogate parameter of kidney function in the perioperative setting of cardiothoracic surgery and the necessity to discover more representative markers of the pathophysiology of AKI. However, except for the tissue inhibitor of metalloproteinase-2 and insulin-like growth factor binding protein 7 ratio, other diagnostic biomarkers with an acceptable sensitivity and specificity are still lacking. This article provides a comprehensive review of various aspects of CSA-AKI, including pathogenesis, risk factors, diagnosis, biomarkers, classification, prevention, and treatment management.

Incidence, Risk Factors and Outcomes of Acute Kidney Injury in Neonates Undergoing Open-heart Surgeries: Single Center Experience

Background

Incidence and outcomes of acute kidney injury (AKI) among neonates who underwent open-heart surgery are not well highlighted in the literature. We aim to assess the incidence, risk factors, and outcome of AKI among neonates undergoing open-heart surgery.

Methods

This is a retrospective cohort study between 2016 and 2021 for all neonates requiring open heart surgery. The cases were divided into 2 groups: the AKI (index) group and the non-AKI (control) group. The two groups were statistically compared for risk factors, needs for dialysis, and outcomes.

Results

100 patients fulfilled the inclusion criteria. Among them, 74 (74%) developed AKI, including 41 (55%), 15 (21%), and 18 (24%) patients in KDIGO stages 1, 2, and 3, respectively. Multivariate analysis comparing both groups demonstrated that low pre-operative creatinine (p = 0.01), prolonged bypass time (p = 0.0004) and high vasoactive inotropic score (VIS), (p = 0.0008) were risk factors for developing AKI post-operatively. Furthermore, in the AKI group, 17 (23%) neonates required renal replacement therapy in the form of peritoneal dialysis. The length of stay was higher in the AKI index group (p = 0.015). Patients who had AKI recovered their kidney function at discharge. There was no difference in mortality between both groups.

Conclusion

The AKI occurred in 74% of neonates undergoing open-heart surgery, with 23% of them needing peritoneal dialysis. Low pre-operative creatinine, high VIS score, and prolonged bypass time are potential risk factors for AKI development after neonatal open-heart surgery. AKI may lead to prolonged hospitalization, though most affected patients recovered their normal kidney function at discharge.

Adverse renal effects associated with cardiopulmonary bypass

Cardiac surgery on cardiopulmonary bypass (CPB) is associated with postoperative renal dysfunction, one of the most common complications of this surgical cohort. Acute kidney injury (AKI) is associated with increased short-term morbidity and mortality and has been the focus of much research. There is increasing recognition of the role of AKI as the key pathophysiological state leading to the disease entities acute and chronic kidney disease (AKD and CKD). In this narrative review, we will consider the epidemiology of renal dysfunction after cardiac surgery on CPB and the clinical manifestations across the spectrum of disease. We will discuss the transition between different states of injury and dysfunction, and, importantly, the relevance to clinicians. The specific facets of kidney injury on extracorporeal circulation will be described and the current evidence evaluated for the use of perfusion-based techniques to reduce the incidence and mitigate the complications of renal dysfunction after cardiac surgery.

Prediction of acute kidney injury following coronary artery bypass graft surgery in elderly Chinese population

BACKGROUND

Acute kidney injury (AKI) is a common and serious complication following coronary artery bypass graft (CABG) surgery. Advanced age is an independent risk factor for the development of AKI, and the incidence of AKI in the elderly increases more rapidly than that in younger patients. This study aimed to develop and validate the risk prediction model for AKI after CABG in elderly patients.

METHODS

Patients were retrospectively recruited from January 2019 to December 2020. AKI after CABG was defined according to the criteria of Kidney Disease Improving Global Outcomes (KDIGO). The entire population was divided into the derivation set and the verification set using random split sampling (ratio: 7:3). Lasso regression method was applied to screen for the variables in the derivation set. Decision curve analysis (DCA) and receiver operating characteristic (ROC) curves were plotted to analyze the predictive ability of the model for AKI risk in the derivation set and the verification set.

RESULTS

A total of 2155 patients were enrolled in this study. They were randomly divided into the derivation set (1509 cases) and the validation set (646 cases). Risk factors associated with AKI were selected by Lasso regression including T2DM, diabetes mellitus type intraoperative use of intra-aortic ballon pump (IABP), cardiopulmonary bypass (CPB), epinephrine, isoprenaline, and so on. The model was established by Lasso logistic regression. The area under the ROC curve (AUC) of the model for the derivation set was 0.754 (95% CI: 0.720 - 0.789), and that for the validation cohort was 0.718 (95% CI: 0.665 - 0.771).

CONCLUSION

In this study, the model with significant preoperative and intraoperative variables showed good prediction performance for AKI following CABG in elderly patients to optimize postoperative treatment strategies and improve early prognosis.

Molecular hydrogen: prospective treatment strategy of kidney damage after cardiac surgery

Cardiac surgery-associated acute kidney injury is a common post-operative complication, mostly due to increasing oxidative stress. Recently, molecular hydrogen (H2 gas) has also been applied to cardiac surgery due to its ability to reduce oxidative stress. We evaluated the potential effect of H2 application on the kidney in an in vivo model of simulated heart transplantation. Pigs underwent cardiac surgery within 3 h while connected to extracorporeal circulation (ECC) and subsequent 60 min of spontaneous reperfusion of the heart. We used two experimental groups: T-pigs after transplantation and TH-pigs after transplantation treated with 4% H2 mixed with air during inhalation of anesthesia and throughout oxygenation of blood in ECC. The levels of creatinine, urea and phosphorus were measured in plasma. Renal tissue samples were analyzed by Western blot method for protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2), Kelch-like ECH-associated protein 1 (Keap-1), and superoxide dismutase (SOD1). After cardiac surgery, selected plasma biomarkers were elevated. However, H2 therapy was followed by the normalization of all these parameters. Our results suggest activation of Nrf2/Keap1 pathway as well as increased SOD1 protein expression in the group treated with H2. The administration of H2 had a protective effect on the kidneys of pigs after cardiac surgery, especially in terms of normalization of plasma biomarkers to control levels.

Selenoprotein P-1 (SEPP1) as an Early Biomarker of Acute Kidney Injury in Patients Undergoing Cardiopulmonary Bypass

Background

Acute Kidney Injury (AKI) is a frequent, dangerous complication in patients undergoing cardiopulmonary bypass (CPB) with oxidative stress playing a crucial role. In this pilot study we evaluated the possible role of the selenoprotein-p1 (SEPP1), a circulating, anti-oxidant selenium transporter, as a predictive biomarker of AKI in this population setting.

Methods

Circulating SEPP1 was measured in the blood of 45 patients before surgery and at 4 h, 8 h and 12 h after CPB by Enzyme-Linked Immunosorbent Assay (ELISA).

Results

SEPP1 increased from 69 [IQR 39-85] to 3263 [IQR 1886.2-5042.7] ng/mL (p for trend < 0.0001). AKI occurred in 26.7% of patients. In these individuals, an earlier and more prominent increase in SEPP1 was observed at 4 h and 8 h, as compared with those not experiencing AKI (difference between trends p < 0.0001). Logistic regression analyses evidenced 4 h and 8 h SEPP1 as significantly associated with AKI (OR 1.035; 95% CI 1.002-1.068; p = 0.03 and 1.011; 95% CI 1.002-1.021; p = 0.02, respectively). ROC analyses displayed a remarkable discriminatory capacity of early SEPP1 measurements in identifying AKI (AUCs ranging from 0.682 to 0.854; p from 0.04 to < 0.0001). In addition, 12 h-SEPP1 showed diagnostic capacity to identify patients reaching a secondary composite endpoint including major adverse kidney events (MAKEs).

Conclusions

Findings from this pilot, exploratory study suggest that early SEPP1 measurement after CPB may hold great potential for improving renal risk stratification in cardiac surgery patients. Further studies in wider and more heterogeneous cohorts are needed to generalize these findings and to evaluate a possible applicability in daily practice.

Risk Factors for Acute Kidney Injury Following Cardiac Surgery and Performance of Leicester Score in a Spanish Cohort

The incidence of acute kidney injury following cardiac surgery (CSA-AKI) is up to 30%, and it places patients at an increased risk of death. The Leicester score (LS) is a new score that predicts CSA-AKI of any stage with better discrimination compared to previous scores. The aim of this study was to identify risk factors for CSA-AKI and to assess the performance of LS. A unicentric retrospective study of patients that required cardiac surgery with cardio-pulmonary bypass (CPB) in 2015 was performed. The inclusion criteria were patients over 18 years old who were operated on for cardiac surgery (valve substitution (VS), Coronary Artery Bypass Graft (CABG), or a combination of both procedures and requiring CPB). CSA-AKI was defined with the Kidney Disease Improving Global Outcomes (KDIGO) criteria. In the multivariate analysis, hypertension (odds ratio 1.883), estimated glomerular filtration rate (EGFR) <60 mL/min (2.365), and peripheral vascular disease (4.66) were associated with the outcome. Both discrimination and calibration were better when the LS was used compared to the Cleveland Clinic Score and Euroscore II, with an area under the curve (AUC) of 0.721. In conclusion, preoperative hypertension in patients with CKD with or without peripheral vasculopathy can identify patients who are at risk of CSA-AKI. The LS was proven to be a valid score that could be used to identify patients who are at risk and who could benefit from intervention studies.