Sex and the Risk of AKI Following Cardio-thoracic Surgery: A Meta-Analysis

Intraoperative central venous pressure during cardiopulmonary bypass is an alternative indicator for early prediction of acute kidney injury in adult cardiac surgery

BACKGROUND

The relationship between venous congestion in cardiopulmonary bypass (CPB) and acute kidney injury (AKI) in cardiac surgery has not utterly substantiated. This study aimed at investigate the relationship between CVP in CPB and the occurrence of AKI.

METHODS

We retrospectively reviewed 2048 consecutive patients with cardiovascular disease undergoing cardiac procedure with CPB from January 2018 to December 2022. We used the median CVP value obtained during CPB for our analysis and patients were grouped according to this parameter. The primary outcomes were AKI and renal replacement therapy(RRT). Multivariable logistic regression was used to explore the association between CVP and AKI.

RESULTS

A total of 2048 patients were enrolled in our study and divided into high CVP group (CVP ≥ 6.5 mmHg) and low CVP group (CVP < 6.5 mmHg) according to the median CVP value. Patients in high CVP group had the high AKI and RRT rate when compared to the low CVPgroup[(367/912,40.24%)vs.(408/1136,35.92%),P = 0.045;(16/912,1.75%vs.9/1136;0.79%), P = 0.049]. Multivariate logistic regression analysis displayed CVP played an indispensable part in development of renal failure in surgical.

CONCLUSIONS

Elevated CVP(≥ 6.5mmH2OmmHg) in CPB during cardiac operation is associated with an increased risk of AKI in cardiovascular surgery patients. Clinical attention should be paid to the potential role of CVP in predicting the occurrence of AKI.

Protein Kinase N1 Level Predicts Acute Kidney Injury in Patients Undergoing Cardiac Surgery: A Prospective Cohort Study

INTRODUCTION

The objective of this study was to examine the utility of protein kinase N1 (PKN1) as a biomarker of cardiac surgery-associated AKI (CSA-AKI).

METHODS

A prospective cohort study of 110 adults undergoing on-pump cardiac surgery was conducted. The associations between post-operative PKN1 and CSA-AKI, AKI severity, need for renal replacement therapy (RRT), duration of AKI, length of ICU stay, and post-operative hospital stay were evaluated.

RESULTS

Patients were categorized into three groups according to PKN1 tertiles. The incidence of CSA-AKI in the third tertile was 3.4-fold higher than that in the first. PKN1 was an independent risk factor for CSA-AKI. The discrimination of PKN1 to CSA-AKI assessed by ROC curve indicated that the AUC was 0.70, and the best cutoff was 5.025 ng/mL. This group (>5.025 ng/mL) was more likely to develop CSA-AKI (p < 0.001). The combined AUC of EuroSCORE, aortic cross-clamp time, and PKN1 was 0.82 (p < 0.001). A higher level of PKN1 was related to increased need for RRT, longer duration of AKI, and length of ICU and post-operative hospital stays.

CONCLUSIONS

PKN1 could be a potential biomarker for the prediction of CSA-AKI. The combination of PKN1, EuroSCORE, and aortic cross-clamp time was likely to predict the occurrence of CSA-AKI.

Sex differences in blood pressure regulation and hypertension: renal, hemodynamic, and hormonal mechanisms

The teleology of sex differences has been argued since at least as early as Aristotle's controversial Generation of Animals more than 300 years BC, which reflects the sex bias of the time to contemporary readers. Although the question "why are the sexes different" remains a topic of debate in the present day in metaphysics, the recent emphasis on sex comparison in research studies has led to the question "how are the sexes different" being addressed in health science through numerous observational studies in both health and disease susceptibility, including blood pressure regulation and hypertension. These efforts have resulted in better understanding of differences in males and females at the molecular level that partially explain their differences in vascular function and renal sodium handling and hence blood pressure and the consequential cardiovascular and kidney disease risks in hypertension. This review focuses on clinical studies comparing differences between men and women in blood pressure over the life span and response to dietary sodium and highlights experimental models investigating sexual dimorphism in the renin-angiotensin-aldosterone, vascular, sympathetic nervous, and immune systems, endothelin, the major renal sodium transporters/exchangers/channels, and the impact of sex hormones on these systems in blood pressure homeostasis. Understanding the mechanisms governing sex differences in blood pressure regulation could guide novel therapeutic approaches in a sex-specific manner to lower cardiovascular risks in hypertension and advance personalized medicine.

Differences in the epidemiology, management and outcomes of kidney disease in men and women

Improved understanding of differences in kidney disease epidemiology, management and outcomes in men and women could help nephrologists to better meet the needs of their patients from a sex- and gender-specific perspective. Evidence of sex differences in the risk and outcomes of acute kidney injury is mixed and dependent on aetiology. Women have a higher prevalence of chronic kidney disease (CKD) stages 3-5 than men, whereas men have a higher prevalence of albuminuria and hence CKD stages 1-2. Men show a faster decline in kidney function, progress more frequently to kidney failure and have higher mortality and risk of cardiovascular disease than women. However, the protective effect of female sex is reduced with CKD progression. Women are less likely than men to be aware of, screened for and diagnosed with CKD, started on antiproteinuric medication and referred to nephrologist care. They also consistently report a poorer health-related quality of life and a higher symptom burden than men. Women experience greater barriers than men to access the waiting list for kidney transplantation, particularly with respect to older age and obesity. However, women also have longer survival than men after transplantation, which may partly explain the comparable prevalence of transplantation between the sexes.

Sex and Gender Differences in AKI

Sex differences in AKI continue to be identified. Generally, women are protected from AKI when compared to men. Much of the protection exhibited in women is diminished after menopause. These sex and age effects have also been noted in animal models of AKI. Gonadal hormones, as modifiers of incidence, severity, and progression of AKI, have been offered as likely contributors to this sex and age effect. In animal models of AKI, estrogen and testosterone seem to modulate susceptibility. Questions remain however regarding cellular and molecular changes that are initiated by modulation of these hormones because both estrogen and testosterone have effects across cell types that play a role in AKI. Although findings have largely been informed by studies in males, molecular pathways that are involved in the initiation and progression of AKI may be modulated by gonadal hormones. Compounding the hormone-receptor effects are developmental effects of sex chromosomal complement and epigenetic influences that may confer sex-based baseline differences in gene and protein expression, and gene dosage effects of X inactivation and escape on molecular pathways. Elucidation of sex-based protection may afford a more complete view of AKI and potential therapeutic interventions. Furthermore, the effect on susceptibility to AKI in transgender patients, who receive life-altering and essential gender-affirming hormone therapy, requires greater attention. In this review, several potential contributors to the sex differences observed in humans and animal models are discussed.

Association between intraoperative hyperglycemia/hyperlactatemia and acute kidney injury following on-pump cardiac surgery: a retrospective cohort study

Background

Despite the long-lasting notion about the substantial contribution of intraoperative un-stabilization of homeostasis factors on the incidence on acute kidney injury (AKI), the possible influence of intraoperative glucose or lactate management, as a modifiable factor, on the development of AKI remains inconclusive.

Objectives

To investigated the relationship between intraoperative hyperglycemia, hyperlactatemia, and postoperative AKI in cardiac surgery.

Methods

A retrospective cohort study was conducted among 4,435 adult patients who underwent on-pump cardiac surgery from July 2019 to March 2022. Intraoperative hyperglycemia and hyperlactatemia were defined as blood glucose levels >10 mmol/L and lactate levels >2 mmol/L, respectively. The primary outcome was the incidence of AKI. All statistical analyses, including t tests, Wilcoxon rank sum tests, chi-square tests, Fisher's exact test, Kolmogorov-Smirnov test, logistic regression models, subgroup analyses, collinearity analysis, and receiver operating characteristic analysis, were performed using the statistical software program R version 4.1.1.

Results

Among the 4,435 patients in the final analysis, a total of 734 (16.55%) patients developed AKI after on-pump cardiac surgery. All studied intraoperative metabolic disorders was associated with increased AKI risk, with most pronounced odds ratio (OR) noted for both hyperglycemia and hyperlactatemia were present intraoperatively [adjusted OR 3.69, 95% confidence intervals (CI) 2.68-5.13, p < 0.001]. Even when hyperglycemia or hyperlactatemia was present alone, the risk of postoperative AKI remained elevated (adjusted OR 1.97, 95% CI 1.50-2.60, p < 0.001).

Conclusion

The presence of intraoperative hyperglycemia and hyperlactatemia may be associated with postoperative acute kidney injury (AKI) in patients undergoing on-pump cardiac surgery. Proper and timely interventions for these metabolic disorders are crucially important in mitigating the risk of AKI.

Sex as a biological variable in acute kidney injury

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of the preclinical and clinical studies investigating sex as a biological variable, as well as the impact of gender, on the development of and progression of acute kidney injury (AKI).

RECENT FINDINGS

Despite a matched degree of ischemia-reperfusion AKI based on measured glomerular filtration rates, male and female mice demonstrated important sex biases in cardiorenal outcomes (1). Although the 2012 Kidney Disease Improving Global Outcomes (KDIGO) Clinical Practice Guideline for AKI reported that female sex is associated with increased rates of hospital acquired AKI, subsequent meta-analyses do not show increased risk of AKI in women. Recent large scale, multicenter epidemiologic studies suggest males have higher rates of hospital acquired AKI. However, women have been consistently shown to have worse renal outcomes after AKI. There may be also be gender-based differences in presentation to care and management.

SUMMARY

Sex is an important biological variable in animal models of acute kidney injury. The impact of sex on AKI likely varies based on the etiology of AKI. Preclinical studies demonstrate the nuances of sex chromosomes, sex hormones and epigenetic factors on AKI, however these have not been well studied in humans. Gender may also impact processes of care, treatment and clinical outcomes related to AKI. The scientific rigor and reproducibility of translational studies benefit from the consideration of sex and gender.

Colistin treatment in older adults: why should we know more?

OBJECTIVES

We aimed to investigate the risk factors of colistin-associated nephrotoxicity in patients older than 65 years treated in the palliative care unit.

METHODS

119 palliative care patients who received intravenous colistimethate for at least 7 days were included in the study. The estimated glomerular filtration rate (GFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2021 equation. Data were obtained from the hospital information system.

RESULTS

The mean age of the participants was 76.7 ± 9.9 years and 49.4% were female. Of the 119 patients, 57 had colistin-induced nephropathy (CIN) according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria. The rate of CIN was higher in women than in men. The baseline phosphate level was higher in the CIN (+) group than in the CIN (-) group. The lower GFR values in patients with pneumonia persisted at days 14 and 30, whereas the lower GFR in patients without pneumonia did not. According to multivariate logistic regression, female gender and baseline phosphate level ≥ 4.5 mg/dl were found as independent variables for the development of nephropathy.

CONCLUSIONS

The creatinine levels of the patients with pneumonia and CIN did not improve after nephrotoxicity, whereas the creatinine levels of the other patients without pneumonia and CIN did. Female gender and baseline phosphate were independent risk factors for CIN. Prolonged kidney failure may lead to a more difficult clinical follow-up process for clinicians. Therefore, clinicians should be aware of persistent renal insufficiency in older patients with pneumonia receiving colistimethate.

Effect of preoperative risk on the association between intraoperative hypotension and postoperative acute kidney injury in cardiac surgery

BACKGROUND

Acute kidney injury (AKI), a common and severe complication after cardiac surgery, has been demonstrated to be associated with intraoperative hypotension (IOH). The reproducibility of this finding and whether preoperative risk modifies the association remain unclear. We hypothesised that the relationship between IOH and AKI after cardiac surgery varies by preoperative risk.

METHODS

We conducted a single-centre, retrospective cohort study to analyse the association between IOH and postoperative AKI by stratifying patients using preoperative risk factors. IOH was defined as a mean arterial pressure (MAP) of less than 65 mmHg and characterised by the cumulative duration and area under the curve (AUC).

RESULTS

Ten variables could be identified as risk factors: age, smoking status, NYHA III/Ⅳ, emergency surgery, peripheral vascular disease, cerebrovascular disease, heart failure, hypertension, previous cardiac surgery, and NT-proBNP concentration. The risk prediction model divided the patients into three equal-sized preoperative risk groups. Low-risk patients demonstrated no association between AKI and IOH of any severity, while high-risk patients demonstrated a statistically significant association between AKI and IOH with a cumulative duration greater than 104 min (adjusted odds ratio [OR]: 2.27, 95% confidence interval [CI]: 1.10-4.74; and adjusted OR: 3.63, 95% CI: 1.77-7.58) and an AUC greater than 905 mmHg min (adjusted OR: 2.08, 95% CI: 1.01-4.36; and adjusted OR: 4.00, 95% CI: 1.95-8.43).

CONCLUSION

IOH is a significant independent risk factor for AKI after cardiac surgery. Patients with higher baseline risk showed a more prominent relationship between IOH and postoperative AKI than low-risk patients.

Future Directions in Optimizing Anesthesia to Reduce Perioperative Acute Kidney Injury

BACKGROUND

Perioperative acute kidney injury (AKI) is common in surgical patients and is associated with high morbidity and mortality. There are currently few options for AKI prevention and treatment. Due to its complex pathophysiology, there is no efficient medication therapy to stop the onset of the injury or repair the damage already done. Certain anesthetics, however, have been demonstrated to affect the risk of perioperative AKI in some studies. The impact of anesthetics on renal function is particularly important as it is closely related to the prognosis of patients. Some anesthetics can induce anti-inflammatory, anti-necrotic, and anti-apoptotic effects. Propofol, sevoflurane, and dexmedetomidine are a few examples of anesthetics that have protective association with AKI in the perioperative period.

SUMMARY

In this study, we reviewed the clinical characteristics, risk factors, and pathogenesis of AKI. Subsequently, the protective effects of various anesthetic agents against perioperative AKI and the latest research are introduced.

KEY MESSAGE

This work demonstrates that a thorough understanding of the reciprocal effects of anesthetic drugs and AKI is crucial for safe perioperative care and prognosis of patients. However, more complete mechanisms and pathophysiological processes still need to be further studied.

Kidney Injury after Cardiac Surgery: Prevention-Associated Cost Reduction

INTRODUCTION

Cardiac surgery may induce acute kidney injury and the need for renal replacement therapy. It is also associated with higher hospital costs, morbidity and mortality. The aims of this study were to investigate predictors of cardiac surgery associated acute kidney injury in our population and to determine the burden of acute kidney injury in elective cardiac surgery, evaluating the potential cost effectiveness of preventing it through the application of the Kidney Disease: Improving Global Outcomes bundle of care to high-risk patient groups identified by the [TIMP-2]x[IGFBP7] used as a screening test.

MATERIAL AND METHODS

In a University Hospital single-center retrospective cohort study we analyzed a consecutive sample of adults who underwent elective cardiac surgery between January and March 2015. A total of 276 patients were admitted during the study period. Data from all patients was analyzed until hospital discharge or the patient's death. The economic analysis was performed from the hospital costs' perspective.

RESULTS

Cardiac surgery associated acute kidney injury occurred in 86 patients (31%). After adjustment, higher preoperative serum creatinine (mg/L, ORadj = 1.09; 95% CI: 1.01 - 1.17), lower preoperative hemoglobin (g/dL, ORadj = 0.79; 95% CI: 0.67 - 0.94), chronic systemic hypertension (ORadj = 5.00; 95% CI: 1.67 - 15.02), an increase in cardiopulmonary bypass time (min, ORadj = 1.01; 95% CI: 1.00 - 1.01) and perioperative use of sodium nitroprusside (ORadj = 6.33; 95% CI: 1.80 - 22.28) remained significantly associated with cardiac surgery related acute kidney injury. The expected cumulative surplus cost for the hospital linked with cardiac surgery associated acute kidney injury (86 patients) was €120 695.84. Based on a median absolute risk reduction of 16.6%, by dosing kidney damage biomarkers in every patient and using preventive measures in high-risk patients, we would expect a break-even point upon screening 78 patients, which would translate, in our patient cohort, into an overall cost benefit of €7145.

CONCLUSION

Preoperative hemoglobin, serum creatinine, systemic hypertension, cardiopulmonary bypass time and perioperative use of sodium nitroprusside were independent predictors of cardiac surgery associated acute kidney injury. Our cost-effectiveness modelling suggests that the use of kidney structural damage biomarkers combined with an early prevention strategy could be associated with potential cost savings.

Effect of Colchicine on the Risk of Perioperative Acute Kidney Injury: Clinical Protocol of a Substudy of the Colchicine for the Prevention of Perioperative Atrial Fibrillation Randomized Clinical Trial

Background

Inflammation during and after surgery can lead to organ damage including acute kidney injury. Colchicine, an established inexpensive anti-inflammatory medication, may help to protect the organs from pro-inflammatory damage. This protocol describes a kidney substudy of the colchicine for the prevention of perioperative atrial fibrillation (COP-AF) study, which is testing the effect of colchicine versus placebo on the risk of atrial fibrillation and myocardial injury among patients undergoing thoracic surgery.

Objective

Our kidney substudy of COP-AF will determine whether colchicine reduces the risk of perioperative acute kidney injury compared with a placebo. We will also examine whether colchicine has a larger absolute benefit in patients with pre-existing chronic kidney disease, the most prominent risk factor for acute kidney injury.

Design and Setting

Randomized, superiority clinical trial conducted in 40 centers in 11 countries from 2018 to 2023.

Patients

Patients (~3200) aged 55 years and older having major thoracic surgery.

Intervention

Patients are randomized 1:1 to receive oral colchicine (0.5 mg tablet) or a matching placebo, given twice daily starting 2 to 4 hours before surgery for a total of 10 days. Patients, health care providers, data collectors, and outcome adjudicators will be blinded to the randomized treatment allocation.

Methods

Serum creatinine concentrations will be measured before surgery and on postoperative days 1, 2, and 3 (or until hospital discharge). The primary outcome of the substudy is perioperative acute kidney injury, defined as an increase (from the prerandomization value) in serum creatinine concentration of either ≥26.5 μmol/L (≥0.3 mg/dL) within 48 hours of surgery or ≥50% within 7 days of surgery. The primary analysis (intention-to-treat) will examine the relative risk of acute kidney injury in patients allocated to receive colchicine versus placebo. We will repeat the primary analysis using alternative definitions of acute kidney injury and examine effect modification by pre-existing chronic kidney disease, defined as a prerandomization estimated glomerular filtration rate (eGFR) <60 mL/min per 1.73 m2.

Limitations

The substudy will be underpowered to detect small effects on more severe forms of acute kidney injury treated with dialysis.

Results

Substudy results will be reported in 2024.

Conclusions

This substudy will estimate the effect of colchicine on the risk of perioperative acute kidney injury in older adults undergoing major thoracic surgery.

Clinical trial registration number

NCT03310125.

Risk factors associated with contrast-associated acute kidney injury in ST-segment elevation myocardial infarction patients: a systematic review and meta-analysis

OBJECTIVE

The objective of this systematic review and meta-analysis was to evaluate the risk factors for contrast-associated acute kidney injury (CA-AKI) in ST-elevation myocardial infarction patients treated with primary percutaneous coronary intervention.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

We searched the databases of PubMed, Embase and Ovid, up to February 2022, for observational studies that investigated the association between risk factors and CA-AKI.

RESULTS

A total of 21 studies were included in the meta-analysis. Of the total 22 015 participants, 2728 developed CA-AKI. Pooled incidence was 11.91% (95% CI 9.69%, 14.14%). Patients with CA-AKI were more likely to be older, female, also had comorbidities (hypertension, diabetes, previous heart failure). Smoking (OR: 0.60; 95% CI 0.52, 0.69) and family history of CAD (coronary artery disease) (OR: 0.76; 95% CI 0.60, 0.95) were associated with lower risk of CA-AKI. Left anterior descending (LAD) artery occlusion (OR: 1.39; 95% CI 1.21, 1.59), left main disease (OR: 4.62; 95% CI 2.24, 9.53) and multivessel coronary disease (OR: 1.33; 95% CI 1.11, 1.60) were risk factors for CA-AKI. Contrast volume (weighted mean difference: 20.40; 95% CI 11.02, 29.79) was associated with increased risk in patients receiving iso-osmolar or low-osmolar non-ionic contrast.

CONCLUSIONS

In addition to the known risk factors, LAD artery infarction, left main disease and multivessel disease are risk factors for CA-AKI. The unexpected favourable association between smoking, as well as family history of CAD, and CA-AKI requires further investigation.

PROSPERO REGISTRATION NUMBER

CRD42021289868.

Sirtuin 6 is a key contributor to gender differences in acute kidney injury

Acute kidney injury (AKI) is rapidly increasing nowadays and at a high risk to progress into chronic kidney disease (CKD). Of note, men are more susceptive to AKI, suggesting gender differences in AKI patients. However, the underlying mechanisms remain largely unclear. To test it, we adopted two experimental models of AKI, including ischemia/reperfusion injury and rhabdomyolysis, which were constructed in age-matched male and female mice. We found severe damages of tubular apoptosis, mitochondrial dysfunction, and loss of renal function showing in male mice, while female mice only had very mild injury. We further tested the expression of Sirtuins, and found that female mice could preserve more Sirtuin members' expression in case of kidney damage. Among Sirtuin family, Sirtuin 6 was maximally preserved in injured kidney in female mice, suggesting its important role involved in the gender differences of AKI pathogenesis. We then found that knockdown of androgen receptor (AR) attenuated tubular damage, mitochondrial dysfunction and retarded the loss of renal function. Overexpression of Sirtuin 6 also showed similar results. Furthermore, in cultured tubular cells, dihydrotestosterone (DHT) decreased Sirtuin 6 expression and exacerbated cell apoptosis. Ectopic expression of Sirtuin 6 sufficiently inhibited DHT-induced cell apoptosis. Mechanically, we found AR inhibited Sirtuin 6, leading to the repression of binding of Sirtuin 6 with PGC-1α. This resulted in acetylation of PGC-1α and inhibition of its activity, further triggered the loss of mitochondrial homeostasis. Our results provided new insights to the underlying mechanisms of gender differences in AKI, suggesting Sirtuin 6 maybe a new therapeutic target for preventing AKI in male patients.

Gender-Related Discrepancies in Short-Term Outcomes in Patients Undergoing Off-Pump Coronary Artery Bypass Grafting Surgery

The sex differences in patients undergoing off-pump coronary artery bypass grafting (OPCAB) surgery are still unclear. Our aim was to investigate the impact of gender on short-term outcomes in males and females after off-pump bypass procedures. Our research was designed as a double-center retrospective analysis. Generally, 343 patients (men (n = 255) and women (n = 88)) who underwent an OPCAB procedure were included in our study. To provide a statistical analysis of unequal cohorts, we created a propensity score-based matching (PSM) analysis (men, n = 61; women, n = 61). The primary endpoint was all-cause in-hospital mortality. Dialysis, transient ischemic attack (TIA), low cardiac output syndrome (LCOS), reoperation due to postoperative bleeding, wound infection and duration of hospital stay were secondary outcomes in our analysis. No significant differences were detected within the male and female groups regarding age (p = 0.116), BMI (p = 0.221), diabetes (p = 0.853), cardiogenic shock (0.256), STEMI (p = 0.283), NSTEMI (p = 0.555) and dialysis (p = 0.496). Males underwent significantly more frequently (p = 0.005) total-arterial revascularization with T-graft technique (p = 0.005) than females. In contrast, temporary pacer use was significantly higher (p = 0.022) in females compared to males. The in-hospital mortality rate was not significantly higher (p = 0.496) in the female group compared to the male group. Likewise, secondary outcomes did not differ significantly between the non-adjusted and the adjusted groups. Based on our findings, gender has no impact on short-term outcomes after OPCAB surgery.

Incidence, predictors and prognosis of acute kidney injury in acute ST-segment elevation myocardial infarction patients undergoing emergent coronary angiography/primary percutaneous coronary intervention

BACKGROUND

Acute kidney injury (AKI) after coronary angiography (CAG) and primary percutaneous coronary intervention (PPCI) is frequently observed, and often interpreted as contrast induced-AKI. This study aimed to investigate the incidence, predictors and outcomes of AKI in acute ST-segment elevation myocardial infarction (STEMI) patients undergoing emergent CAG/PPCI using the control group of STEMI patients who were not exposed to contrast agents within the first 72 h.

METHODS

We performed a retrospective analysis of 1670 STEMI patients. Of them, 673 patients underwent emergent CAG/PPCI, and 997 patients treated with thrombolysis or no reperfusion therapy who were not exposed to contrast material during the first 72 h. AKI was defined as an increase of serum creatinine ≥ 44.2 mmol/L or ≥ 25% from baseline within 72 h. Patents were then followed up for the occurrence of all-cause mortality for 40 months (interquartile range: 24-55 months).

RESULTS

After propensity score matching, 505 pairs of patients were matched. Overall, the incidence of AKI was 27.4%, and AKI rates were not significantly different in patients with and without emergent CAG/PPCI procedure (27.5% vs. 27.3%, P = 0.944). Multivariate logistic regression analysis identified that the independent predictors of AKI were female, elevated interleukin-6 level, decreased lymphocyte count, left ventricular ejection fraction < 50% and use of diuretics in patients with emergent CAG/PPCI. Patients with AKI than those without AKI experienced higher incidence of acute heart failure with Killip class III (9.4% vs. 3.3%, P = 0.005; 15.2% vs. 6.8%, P = 0.003, respectively) and mortality (5.8% vs. 1.4%, P = 0.014; 12.3% vs. 4.6%, P = 0.002, respectively) in patients with and without emergent CAG/PPCI. Multivariate Cox regression analysis confirmed that AKI was independently associated with long-term mortality rate at 40 months follow-up in patients with and without emergent CAG/PPCI (HR = 1.867, 95% CI: 1.086-3.210, P = 0.024; HR = 1.700, 95% CI: 1.219-2.370, P = 0.002, respectively).

CONCLUSIONS

Approximately 27.0% of STEMI patients experience AKI, which is strongly associated with an increased short- and long-term mortality regardless of emergent CAG/PPCI procedure. The development of AKI is mainly related to female gender, inflammation reaction, heart failure and use of diuretics in STEMI patients undergoing emergent CAG/PPCI.

Machine learning in the prediction of cardiac surgery associated acute kidney injury with early postoperative biomarkers

Purpose

To establish novel prediction models for predicting acute kidney injury (AKI) after cardiac surgery based on early postoperative biomarkers.

Patients and methods

This study enrolled patients who underwent cardiac surgery in a Chinese tertiary cardiac center and consisted of a discovery cohort (n = 452, from November 2018 to June 2019) and a validation cohort (n = 326, from December 2019 to May 2020). 43 biomarkers were screened using the least absolute shrinkage and selection operator and logistic regression to construct a nomogram model. Three tree-based machine learning models were also established: eXtreme Gradient Boosting (XGBoost), random forest (RF) and deep forest (DF). Model performance was accessed using area under the receiver operating characteristic curve (AUC). AKI was defined according to the Kidney Disease Improving Global Outcomes criteria.

Results

Five biomarkers were identified as independent predictors of AKI and were included in the nomogram: soluble ST2 (sST2), N terminal pro-brain natriuretic peptide (NT-proBNP), heart-type fatty acid binding protein (H-FABP), lactic dehydrogenase (LDH), and uric acid (UA). In the validation cohort, the nomogram achieved good discrimination, with AUC of 0.834. The machine learning models also exhibited adequate discrimination, with AUC of 0.856, 0.850, and 0.836 for DF, RF, and XGBoost, respectively. Both nomogram and machine learning models had well calibrated. The AUC of sST2, NT-proBNP, H-FABP, LDH, and UA to discriminate AKI were 0.670, 0.713, 0.725, 0.704, and 0.749, respectively. In addition, all of these biomarkers were significantly correlated with AKI after adjusting clinical confounders (odds ratio and 95% confidence interval of the third vs. the first tertile: sST2, 3.55 [2.34-5.49], NT-proBNP, 5.50 [3.54-8.71], H-FABP, 6.64 [4.11-11.06], LDH, 7.47 [4.54-12.64], and UA, 8.93 [5.46-15.06]).

Conclusion

Our study provides a series of novel predictive models and five biomarkers for enhancing the risk stratification of AKI after cardiac surgery.

Postoperative Acute Kidney Injury by Age and Sex: A Retrospective Cohort Association Study

BACKGROUND

Acute kidney injury (AKI) after noncardiac surgery is common and has substantial health impact. Preclinical and clinical studies examining the influence of sex on AKI have yielded conflicting results, although they typically do not account for age-related changes. The objective of the study was to determine the association of age and sex groups on postoperative AKI. The authors hypothesized that younger females would display lower risk of postoperative AKI than males of similar age, and the protection would be lost in older females.

METHODS

This was a multicenter retrospective cohort study across 46 institutions between 2013 and 2019. Participants included adult inpatients without pre-existing end-stage kidney disease undergoing index major noncardiac, nonkidney/urologic surgeries. The authors' primary exposure was age and sex groups defined as females 50 yr or younger, females older than 50 yr, males 50 yr or younger, and males older than 50 yr. The authors' primary outcome was development of AKI by Kidney Disease-Improving Global Outcomes serum creatinine criteria. Exploratory analyses included associations of ascending age groups and hormone replacement therapy home medications with postoperative AKI.

RESULTS

Among 390,382 patients, 25,809 (6.6%) developed postoperative AKI (females 50 yr or younger: 2,190 of 58,585 [3.7%]; females older than 50 yr: 9,320 of 14,4047 [6.5%]; males 50 yr or younger: 3,289 of 55,503 [5.9%]; males older than 50 yr: 11,010 of 132,447 [8.3%]). When adjusted for AKI risk factors, compared to females younger than 50 yr (odds ratio, 1), the odds of AKI were higher in females older than 50 yr (odds ratio, 1.51; 95% CI, 1.43 to 1.59), males younger than 50 yr (odds ratio, 1.90; 95% CI, 1.79 to 2.01), and males older than 50 yr (odds ratio, 2.06; 95% CI, 1.96 to 2.17).

CONCLUSIONS

Younger females display a lower odds of postoperative AKI that gradually increases with age. These results suggest that age-related changes in women should be further studied as modifiers of postoperative AKI risk after noncardiac surgery.

EDITOR’S PERSPECTIVE

Original research gender differences in recovering from cardiac and vascular surgery associated acute kidney injury: A six-year retrospective comparative study in Nigeria

Introduction

Gender differences exist in the demographic, clinical characteristic and outcome of patients with cardiac and vascular surgery (CVS) associated acute kidney injury (AKI).

Materials and Methods

This retrospective study had a total of 88 participants for which socio-demographic, clinical and laboratory (serum electrolyte, full blood count, urine analysis and urine volume, creatinine, and glomerular filtration rate) data of participants were taken preoperative and postoperative days 1, 7, and 30.

Results

A total of 88 (66 males and 22 females) participants were studied. Diseases of the heart valves were more common in females than males. The mean age of the participants was 65.9 ± 6.9 years, with males 65.1 ± 7.6 years and females 68.3 ± 8.4 years, P = 0.02. Before surgery, a significantly greater proportion of females had kidney dysfunction compared to males, P = 0.003. Valvular surgery and coronary bypass were the most common surgeries. The proportion of emergency surgeries and admissions <7 days were significantly higher in females than males, P = 0.04 and P = 0.02, respectively. Full recovering from AKI was significantly higher in males as partial recovery and death were significantly lower in them, P = 0.02. Of the 35 (39.8%) who had dialysis, 85.7% recovered fully, 5.7% became dialysis, and dependent while 8.6% died. The predictors of nonrecovery from CVS-AKI were female gender, elderly, preoperative kidney dysfunction and AKI stage 3.

Conclusion

Males with AKI were younger than the females. Valvular surgeries were most common. Background kidney dysfunction and advance age were risk factors for AKI. Postoperative, AKI was commoner in males who were more likely to recover full kidney function. Optimizing patient preparation could reduce the incidence of CVS-AKI.

Predicting the risk of acute kidney injury after cardiopulmonary bypass: development and assessment of a new predictive nomogram

BACKGROUND

Acute kidney injury (AKI) is a common and severe complication of cardiac surgery with cardiopulmonary bypass (CPB). This study aimed to establish a model to predict the probability of postoperative AKI in patients undergoing cardiac surgery with CPB.

METHODS

We conducted a retrospective, multicenter study to analyze 1082 patients undergoing cardiac surgery under CPB. The least absolute shrinkage and selection operator regression model was used to optimize feature selection for the AKI model. Multivariable logistic regression analysis was applied to build a prediction model incorporating the feature selected in the previously mentioned model. Finally, we used multiple methods to evaluate the accuracy and clinical applicability of the model.

RESULTS

Age, gender, hypertension, CPB duration, intraoperative 5% bicarbonate solution and red blood cell transfusion, urine volume were identified as important factors. Then, these risk factors were created into nomogram to predict the incidence of AKI after cardiac surgery under CPB.

CONCLUSION

We developed a nomogram to predict the incidence of AKI after cardiac surgery. This model can be used as a reference tool for evaluating early medical intervention to prevent postoperative AKI.

Insight Into Kidney Protection by Vacuum-Assisted Venous Drainage in Adult Cardiac Operation ― A Multicenter Study ―

BACKGROUND

The relationship between venous congestion and acute kidney injury (AKI) in cardiac surgery after cardiopulmonary bypass has not thoroughly investigated. Vacuum-assisted venous drainage (VAVD) reduces venous congestion, so we hypothesized that it would reduce the incidence of AKI in cardiovascular surgery.Methods and Results: We used a retrospective propensity score-matched analysis to evaluate the effect of VAVD on AKI in adult patients undergoing cardiac surgery. The primary outcomes were AKI and renal replacement therapy (RRT). Multivariable logistic regression was used to explore the association between VAVD exposure and adverse kidney outcomes. Of 15,387 eligible subjects, 13,480 and 1,907 had gravity drainage (GD) or VAVD, respectively, during cardiopulmonary bypass. On the basis of propensity scores, there were 1,468 matched patient pairs for GD and VAVD. The average central venous pressure (CVP) in the GD group was higher than in the VAVD group (4.43±1.23 mmHg vs. 2.30±0.98 mmHg, P<0.001). The occurrence of AKI and RRT was statistically significantly different in the 2 groups [(600/1,468, 40.87%) vs. (445/1,468, 30.31%), P<0.001; (36/1,468, 2.45% vs. 8/1,468; 0.54%), P<0.001, respectively)]. Multivariate logistic regression analysis revealed that VAVD was effective in protecting kidney function.

CONCLUSIONS

VAVD was associated with a lower CVP and lower incidence of AKI, suggesting it protects adult cardiac patients from adverse renal outcomes.

Derivation and Validation a Risk Model for Acute Kidney Injury and Subsequent Adverse Events After Cardiac Surgery: A Multicenter Cohort Study

Purpose

To establish a risk model for acute kidney injury and subsequent adverse events in Chinese cardiac patients.

Patients and Methods

This study included 11,740 patients who had cardiac surgery at 14 institutions in China. Patients were randomly assigned to a derivation cohort (n = 8197) or a validation cohort (n = 3543). Variables ascertained during hospitalization were screened using least absolute shrinkage and selection operator and logistic regression to construct a nomogram model. Model performance was evaluated using C-statistic, calibration curve, and Brier score. The nomogram was further compared with the five conventional models: Mehta score, Ng score, AKICS score, SRI score, and Cleveland Clinic score. Acute kidney injury was defined according to the Kidney Disease Improving Global Outcomes criteria. Subsequent adverse events included mid-term outcomes: death from all causes and major adverse kidney events (defined as composite outcome of death from renal failure, dialysis, and advanced chronic kidney disease).

Results

Acute kidney injury occurred in 3237 (27.6%) patients. The model included 12 predictors. The total score generated from the nomogram ranged from 0 to 556. The nomogram achieved a C-statistic of 0.825 and 0.804 in the derivation and validation cohorts, respectively, and had well-fitted calibration curves. The model performance of the nomogram was better than other five conventional models. After risk stratification, moderate-risk or high-risk groups were associated with significantly higher rates of death from all causes and major adverse kidney events compared with low-risk group during 7-year follow-up.

Conclusion

The nomogram could serve as an effective tool for predicting acute kidney injury and evaluating its subsequent adverse events after cardiac surgery.

Acute kidney disease predicts chronic kidney disease in pediatric non-kidney solid organ transplant patients

BACKGROUND

Acute kidney disease (AKD) is defined as impaired kidney function present for <90 days with or without an acute kidney injury (AKI) event. Adults with AKD have an increased risk for progression to chronic kidney disease (CKD) and mortality. There are no data on the epidemiology of AKD in children after transplant. The aim of this study was to evaluate the incidence and risk factors for AKI, AKD, and CKD in children after transplantation.

METHODS

This is a retrospective cohort study of all children undergoing non-kidney solid organ transplant between 2011 and 2019 at UPMC Children's Hospital of Pittsburgh. AKI and AKD were defined using the Kidney Disease Improving Global Outcomes criteria. Patients with a new estimated glomerular filtration rate <60 ml/min/1.73m² persisting for >3 months met criteria for new CKD. Variables associated with AKI, AKD, and CKD were analyzed.

RESULTS

Among 338 patients, 37.9% met criteria for severe AKI, 13% for AKD, and 8% for a new diagnosis of CKD. Stage 3 AKI was independently associated with AKD (OR: 5.35; 95% CI: 2.23-12.86). Severe AKI was not associated with new-onset CKD, whereas AKD was associated with new-onset CKD (OR: 29.74; CI: 11.22-78.82).

CONCLUSION

AKD may be superior to AKI in predicting risk of CKD in children after non-kidney solid organ transplantation.

Intraoperative risk factors of acute kidney injury after liver transplantation

Acute kidney injury (AKI) is one of the most common complications of liver transplantation (LT). We examined the impact of intraoperative management on risk for AKI following LT. In this retrospective observational study, we linked data from the electronic health record with standardized transplant outcomes. Our primary outcome was stage 2 or 3 AKI as defined by Kidney Disease Improving Global Outcomes guidelines within the first 7 days of LT. We used logistic regression models to test the hypothesis that the addition of intraoperative variables, including inotropic/vasopressor administration, transfusion requirements, and hemodynamic markers improves our ability to predict AKI following LT. We also examined the impact of postoperative AKI on mortality. Of the 598 adult primary LT recipients included in our study, 43% (n = 255) were diagnosed with AKI within the first 7 postoperative days. Several preoperative and intraoperative variables including (1) electrolyte/acid-base balance disorder (International Classification of Diseases, Ninth Revision codes 253.6 or 276.x and International Classification of Diseases, Tenth Revision codes E22.2 or E87.x, where x is any digit; adjusted odds ratio [aOR], 1.917, 95% confidence interval [CI], 1.280-2.869; p = 0.002); (2) preoperative anemia (aOR, 2.612; 95% CI, 1.405-4.854; p = 0.002); (3) low serum albumin (aOR, 0.576; 95% CI, 0.410-0.808; p = 0.001), increased potassium value during reperfusion (aOR, 1.513; 95% CI, 1.103-2.077; p = 0.01), and lactate during reperfusion (aOR, 1.081; 95% CI, 1.003-1.166; p = 0.04) were associated with posttransplant AKI. New dialysis requirement within the first 7 days postoperatively predicted the posttransplant mortality. Our study identified significant association between several potentially modifiable variables with posttransplant AKI. The addition of intraoperative data did not improve overall model discrimination.

Dimorphic Response of Sex and Hospital-acquired Acute Kidney Injury

The risk of hospital-acquired acute kidney injury (HA-AKI) depends on a person's intrinsic susceptibility, the presence of risk factors, and on the type and extent of exposure to kidney insults. Older cohort studies have focused on male-only or mostly male populations, assuming a lower incidence of HA-AKI in women. Insufficient statistical power suggested that female sex was a shared susceptibility factor for HA-AKI. It was included as a risk factor in risk prediction models of HA-AKI. With the inclusion of women in clinical research studies, this presumption was challenged. Recent meta-analyses of sex-stratified studies showed that the risk for HA-AKI was significantly higher in men. These results suggested a protective role of female sex hormones. However, these studies were complicated by the inclusion of women across an age spectrum that includes the menopausal shift. Preliminary clinical and basic research data suggest that postmenopausal women lose their protection from HA-AKI. The number, size, and quality of reported clinical studies are low. There is an unmet need to characterize the susceptibility factor sex, to assess its clinical relevance and to evaluate renoprotection by sex hormone administration.

Caloric restriction reduces the pro-inflammatory eicosanoid 20- hydroxyeicosatetraenoic acid to protect from acute kidney injury

Acute kidney injury is a frequent complication in the clinical setting and associated with significant morbidity and mortality. Preconditioning with short-term caloric restriction is highly protective against kidney injury in rodent ischemia reperfusion injury models. However, the underlying mechanisms are unknown hampering clinical translation. Here, we examined the molecular basis of caloric restriction-mediated protection to elucidate the principles of kidney stress resistance. Analysis of an RNAseq dataset after caloric restriction identified Cyp4a12a, a cytochrome exclusively expressed in male mice, to be strongly downregulated after caloric restriction. Kidney ischemia reperfusion injury robustly induced acute kidney injury in male mice and this damage could be markedly attenuated by pretreatment with caloric restriction. In females, damage was significantly less pronounced and preconditioning with caloric restriction had only little effect. Tissue concentrations of the metabolic product of Cyp4a12a, 20-hydroxyeicosatetraenoic acid (20-HETE), were found to be significantly reduced by caloric restriction. Conversely, intraperitoneal supplementation of 20-HETE in preconditioned males partly abrogated the protective potential of caloric restriction. Interestingly, this effect was accompanied by a partial reversal of caloric restriction-induced changes in protein but not RNA expression pointing towards inflammation, endoplasmic reticulum stress and lipid metabolism. Thus, our findings provide an insight into the mechanisms underlying kidney protection by caloric restriction. Hence, understanding the mediators of preconditioning is an important pre-requisite for moving towards translation to the clinical setting.

Procalcitonin, Interleukin-6 and C-reactive Protein Levels Predict Renal Adverse Outcomes and Mortality in Patients with Acute Type A Aortic Dissection

Background

Acute type A aortic coarctation (AAAD) is a highly deadly and serious life-threatening disease. The purpose of this study was to estimate the predictive value of peak procalcitonin, interleukin-6, and C-reactive protein levels on adverse renal outcomes and mortality in patients undergoing surgery for AAAD.

Methods

Perioperative peak PCT, CRP, and IL-6 levels were retrospectively collected in 331 patients hospitalized with AAAD from 2009 to 2021. The primary endpoints were AKI stage 2–3 and mortality. The receiver operating characteristic (ROC) curves were used to compare the predictive values of peak PCT, CRP, and IL-6 for different clinical outcomes. Multivariable logistic regression analysis was used to find risk factors for AKI and 30-day mortality.

Results

The incidence of AKI stage 2–3 following AAAD was 50.8% (168/331). The 30-day and overall mortality were significantly greater in the AKI 2–3 group than in the AKI 0–1 group (P = 0.000). ROC curve analysis showed that peak PCT, with an area under the ROC curve (AUC) of 0.712, was a more accurate predictor of adverse renal outcomes than peak IL-6 and CRP. Multivariable logistic regression analysis revealed that PCT > 0.39 ng/mL was an independent risk factor for AKI stage 2–3. Peak IL-6 > 259 pg/mL was found to be an independent risk factor for 30-day mortality.

Conclusion

In patients with surgery for AAAD, peak PCT provides a well-predictive indicator of AKI stage 2–3 and peak IL-6 indicates a favorable predictor of 30-day mortality.

Prediction of acute kidney injury after cardiac surgery: model development using a Chinese electronic health record dataset

Background

Acute kidney injury (AKI) is a major complication following cardiac surgery that substantially increases morbidity and mortality. Current diagnostic guidelines based on elevated serum creatinine and/or the presence of oliguria potentially delay its diagnosis. We presented a series of models for predicting AKI after cardiac surgery based on electronic health record data.

Methods

We enrolled 1457 adult patients who underwent cardiac surgery at Nanjing First Hospital from January 2017 to June 2019. 193 clinical features, including demographic characteristics, comorbidities and hospital evaluation, laboratory test, medication, and surgical information, were available for each patient. The number of important variables was determined using the sliding windows sequential forward feature selection technique (SWSFS). The following model development methods were introduced: extreme gradient boosting (XGBoost), random forest (RF), deep forest (DF), and logistic regression. Model performance was accessed using the area under the receiver operating characteristic curve (AUROC). We additionally applied SHapley Additive exPlanation (SHAP) values to explain the RF model. AKI was defined according to Kidney Disease Improving Global Outcomes guidelines.

Results

In the discovery set, SWSFS identified 16 important variables. The top 5 variables in the RF importance matrix plot were central venous pressure, intraoperative urine output, hemoglobin, serum potassium, and lactic dehydrogenase. In the validation set, the DF model exhibited the highest AUROC (0.881, 95% confidence interval [CI] 0.831–0.930), followed by RF (0.872, 95% CI 0.820–0.923) and XGBoost (0.857, 95% CI 0.802–0.912). A nomogram model was constructed based on intraoperative longitudinal features, achieving an AUROC of 0.824 (95% CI 0.763–0.885) in the validation set. The SHAP values successfully illustrated the positive or negative contribution of the 16 variables attributed to the output of the RF model and the individual variable’s effect on model prediction.

Conclusions

Our study identified 16 important predictors and provided a series of prediction models to enhance risk stratification of AKI after cardiac surgery. These novel predictors might aid in choosing proper preventive and therapeutic strategies in the perioperative management of AKI patients.

Sex Differences in Acute Kidney Injury

Female sex confers renoprotection in chronic progressive kidney disease. It is less well recognized that sexual dimorphism also is evident in the development of ischemic and nephrotoxic acute kidney injury (AKI). Animal studies consistently have shown that female sex protects against the development of renal injury in experimental models of ischemic AKI. However, the consensus opinion is that in human beings, female sex is an independent risk factor for AKI. Based on a systematic review of experimental and clinical literature, we present data to support the conclusion that, contrary to consensus opinion, it is male sex, not female sex, that is associated with the development of AKI.

Experimental models of acute kidney injury for translational research

Preclinical models of human disease provide powerful tools for therapeutic discovery but have limitations. This problem is especially apparent in the field of acute kidney injury (AKI), in which clinical trial failures have been attributed to inaccurate modelling performed largely in rodents. Multidisciplinary efforts such as the Kidney Precision Medicine Project are now starting to identify molecular subtypes of human AKI. In addition, over the past decade, there have been developments in human pluripotent stem cell-derived kidney organoids as well as zebrafish, rodent and large animal models of AKI. These organoid and AKI models are being deployed at different stages of preclinical therapeutic development. However, the traditionally siloed, preclinical investigator-driven approaches that have been used to evaluate AKI therapeutics to date rarely account for the limitations of the model systems used and have given rise to false expectations of clinical efficacy in patients with different AKI pathophysiologies. To address this problem, there is a need to develop more flexible and integrated approaches, involving teams of investigators with expertise in a range of different model systems, working closely with clinical investigators, to develop robust preclinical evidence to support more focused interventions in patients with AKI.

Decreased preoperative urinary uromodulin as a predictor of acute kidney injury and perioperative kidney dysfunction in patients undergoing cardiac surgery: a prospective cohort study

BACKGROUND

Acute kidney injury (AKI) is a major complication following cardiac surgery that substantially increases mortality. We explored the clinical utility of urinary uromodulin (uUMOD), a marker of renal tubular reserve, for preoperative identification of patients at risk for AKI and perioperative kidney dysfunction.

METHODS

This prospective observational study included patients who underwent cardiac surgery between December 2019 and January 2021. AKI was defined according to the Kidney Disease Improving Global Outcomes criteria; perioperative kidney dysfunction was accessed using a longitudinal estimated glomerular filtration rate.

RESULTS

A total of 409 participants were enrolled. Patients with uUMOD ≤ 20.7 µg/mL were associated with a higher risk for AKI (odds ratio, 3.24; 95% confidence interval: 1.87-5.63, P < 0.001), independent of baseline kidney function. The uUMOD exhibits adequate discrimination for predicting AKI, with an area under the receiver operating characteristic curve of 0.713 (95% confidence interval: 0.652-0.773), and has well-fitted calibration (Hosmer-Lemeshow goodness-of-fit test, P = 0.163). The trajectory analysis revealed that decreased uUMOD levels were linked to a higher risk of patients being assigned to a worse perioperative kidney function cluster.

CONCLUSIONS

Decreased preoperative uUMOD is independently associated with an increased risk of AKI and perioperative kidney dysfunction after cardiac surgery.

The Neglected Price of Pediatric Acute Kidney Injury: Non-renal Implications

Preclinical models and emerging translational data suggest that acute kidney injury (AKI) has far reaching effects on all other major organ systems in the body. Common in critically ill children and adults, AKI is independently associated with worse short and long term morbidity, as well as mortality, in these vulnerable populations. Evidence exists in adult populations regarding the impact AKI has on life course. Recently, non-renal organ effects of AKI have been highlighted in pediatric AKI survivors. Given the unique pediatric considerations related to somatic growth and neurodevelopmental consequences, pediatric AKI has the potential to fundamentally alter life course outcomes. In this article, we highlight the challenging and complex interplay between AKI and the brain, heart, lungs, immune system, growth, functional status, and longitudinal outcomes. Specifically, we discuss the biologic basis for how AKI may contribute to neurologic injury and neurodevelopment, cardiac dysfunction, acute lung injury, immunoparalysis and increased risk of infections, diminished somatic growth, worsened functional status and health related quality of life, and finally the impact on young adult health and life course outcomes.

The Association Between Acute Kidney Injury and Mortality After Coronary Artery Bypass Grafting Was Similar in Women and Men

OBJECTIVE

To assess sex differences in short- and long-term mortality in patients who develop acute kidney injury (AKI) after coronary artery bypass grafting (CABG).

DESIGN

An observational cohort study.

SETTING

A multicenter, nationwide, population-based, observational cohort study.

PARTICIPANTS

All patients (n = 32,013) who underwent primary nonemergent isolated CABG in Sweden between January 1, 2003, and December 31, 2013.

INTERVENTIONS

AKI and its association with 90-day mortality were analyzed using logistic regression. AKI and its association with long-term mortality were analyzed using Cox regression analysis.

MEASUREMENTS AND MAIN RESULTS

AKI was defined as an absolute increase by 26 µmol/L or a relative increase by 50% postoperatively compared with the preoperative serum creatinine concentration. Ninety-day mortality was defined as death by any cause within 90 days after surgery. Long-term mortality was defined as death by any cause from day 91 after surgery to the end of the study period. In total, 13.9% of women and 14.4% of men developed AKI after CABG. The multivariate-adjusted odds ratio (95% confidence interval [CI]) for death within 90 days in patients with AKI compared to those without AKI was 5.1 (3.6-7.2) and 5.2 (4.2-6.6) in women and men, respectively (p for interaction = 0.74). The multivariate-adjusted hazard ratio (95% CI) for long-term death in those with AKI compared to those without AKI was 1.4 (1.2-1.7) and 1.3 (1.2-1.4) in women and men, respectively (p for interaction = 0.27).

CONCLUSION

AKI after CABG was associated with a similar increase in 90-day and long-term mortality in both women and men.

Prediction of acute kidney injury after cardiac surgery from preoperative N-terminal pro-B-type natriuretic peptide

BACKGROUND

Acute kidney injury (AKI) is common after cardiac surgery and is difficult to predict. N-terminal pro-B-type natriuretic peptide (NT-proBNP) is highly predictive for perioperative cardiovascular complications and may also predict renal injury. We therefore tested the hypothesis that preoperative NT-proBNP concentration is associated with renal injury after major cardiac surgery.

METHODS

We included 35 337 patients who had cardiac surgery and measurements of preoperative NT-proBNP and postoperative creatinine. The primary outcome was Kidney Disease: Improving Global Outcomes Stages 1-3 AKI. We also separately considered severe AKI, including Stage 2, Stage 3, and new-onset dialysis.

RESULTS

Postoperative AKI occurred in 11 999 (34.0%) patients. Stage 2 AKI occurred in 1200 (3.4%) patients, Stage 3 AKI in 474 (1.3%) patients, and new-onset dialysis was required in 241 (0.7%) patients. The NT-proBNP concentrations (considered continuously or in quartiles) were significantly correlated with any-stage AKI and severe AKI (all adjusted P<0.01). Including NT-proBNP significantly improved AKI prediction (net reclassification improvement: 0.24 [0.22-0.27]; P<0.001) beyond basic models derived from other baseline factors in the overall population. Reclassification was especially improved for higher grades of renal injury: 0.30 (0.25-0.36) for Stage 2, 0.46 (0.37-0.55) for Stage 3, and 0.47 (0.35-0.60) for dialysis.

CONCLUSIONS

Increased preoperative NT-proBNP concentrations were associated with postoperative AKI in patients having cardiac surgery. Including NT-proBNP substantially improves AKI predictions based on other preoperative factors.

Expression of ACE2 in the Intact and Acutely Injured Kidney

Background

The actions of angiotensin-converting enzyme 2 (ACE2) oppose those of the renin-angiotensin-aldosterone system. ACE2 may be a cytoprotectant in some tissues. This study examined ACE2 expression in models of AKI.

Methods

ACE2 mRNA and protein expression and ACE2 activity were assessed in murine ischemic AKI. Renal ACE2 mRNA expression was evaluated in LPS-induced AKI in wild-type (C57BL/6J) mice, in heme oxygenase-1+/+ and heme oxygenase-1-/- mice, and after unilateral ureteral obstruction (UUO) in wild-type mice. The effect of sex and age on renal ACE2 protein expression was also assessed.

Results

In ischemic AKI, ACE2 mRNA and protein expression and ACE2 activity were reduced as compared with such indices in the intact kidney. In ischemic AKI, ACE2, which, in health, is prominently expressed in the tubular epithelium, especially proximal tubules, is decreased in expression in these segments. Decreased ACE2 expression in AKI did not reflect reduced GFR, because ACE2 mRNA expression was unaltered after UUO. LPS induced renal ACE2 mRNA expression in wild-type mice, but this effect did not occur in heme oxygenase-1-deficient mice. In ischemic and LPS-induced AKI, renal expression of the Mas receptor was increased. In the intact kidney, renal ACE2 protein expression decreased in female mice as compared with male mice, but was unaltered with age.

Conclusion

We conclude that renal ACE2 expression is decreased in ischemic AKI, characterized by decreased GFR and abundant cell death, but is upregulated in LPS-induced AKI, an effect requiring heme oxygenase-1. Determining the significance of ACE2 expression in experimental AKI merits further study. We suggest that understanding the mechanism underlying ACE2 downregulation in AKI may offer insights relevant to COVID-19: ACE2 expression is downregulated after ACE2 mediates SARS-CoV-2 cellular entry; such downregulation is proinflammatory; and AKI commonly occurs and determines outcomes in COVID-19.

Dickkopf 3-a novel biomarker of the 'kidney injury continuum'

Chronic kidney disease (CKD) is a global public health problem accompanied by substantial comorbidities and reduced life expectancy. In this respect, progressive CKD leading to uraemia can be seen as a systemic disease with a critical impact on virtually all organ systems. Therefore, it is of particular importance to identify patients with ongoing CKD progression, which is challenging, because the individual course of CKD is difficult to predict. Patterns of progression in CKD patients include linear and non-linear trajectories of GFR loss, but kidney function can also remain stable for years. Moreover, a substantial GFR decline may occur in the absence of higher-grade albuminuria (non-proteinuric CKD), rendering the measurement of albuminuria less reliable for progression prediction in such individuals. In the present review, we focus on the recently identified glycoprotein Dickkopf-3 (DKK3) as a stress-induced, renal tubular epithelial cell-derived, pro-fibrotic molecule. In experimental CKD models, DKK3 promoted renal tubulointerstitial fibrosis through modulation of the canonical Wnt/β-catenin signalling pathway. In clinical studies, increased urinary DKK3 levels identified patients at high risk for short-term CKD progression, regardless of the cause of kidney disease, baseline kidney function and albuminuria. Moreover, increased urinary DKK3 levels are associated with a high risk for acute kidney injury and the subsequent loss of kidney function after cardiac surgery. These findings highlight DKK3 as a mediator of renal tubular cell damage in kidney injury and short-term progression of kidney disease, with potential therapeutic implications.

Influence of age on gender-related differences in acute kidney injury after minimally invasive radical or partial nephrectomy

BACKGROUND

Female gender is known to be protective against acute kidney injury (AKI) after radical or partial nephrectomy and estrogen is considered a protective factor. If estrogen is a major contributor to the protective effects of female gender against renal injury, these protective effects may be diminished in postmenopausal women. Therefore, this retrospective study investigated the influence of female age on gender-related differences in AKI after minimally invasive radical or partial nephrectomy.

METHODS

Patients who underwent minimally invasive radical (n = 765) or partial (n = 1161) nephrectomy were selected. These patients were stratified by gender and divided into three age categories considered to be pre, peri, and postmenopausal periods in women: ≤ 40 years, 41-59 years, and ≥ 60 years, respectively. Adjusted logistic regression analyses were conducted to identify the risk of AKI according to gender and age.

RESULTS

The incidence of AKI after radical or partial nephrectomy was significantly higher in men as compared to women in all age categories. Women aged ≥ 60 years had a significantly increased risk of AKI as compared to women aged < 60 years in radical nephrectomy, but not in partial nephrectomy. When compared with women aged ≥ 60 years, men aged > 40 years accompanied significantly higher risk of AKI following both radical and partial nephrectomy, even after adjusting confounders. However, men aged ≤ 40 years had a similar risk of AKI after radical nephrectomy, but a significantly higher risk after partial nephrectomy as compared to women aged ≥ 60 years.

CONCLUSION

Male gender was associated with a higher risk of AKI after radical and partial nephrectomy as compared to postmenopausal women. This calls for more thorough preoperative counseling and renal protective strategies in male patients when undergoing radical and partial nephrectomy.

Acute Kidney Injury following Cardiopulmonary Bypass: A Challenging Picture

Recent studies have recognized several risk factors for cardiopulmonary bypass- (CPB-) associated acute kidney injury (AKI). However, the lack of early biomarkers for AKI prevents practitioners from intervening in a timely manner. We reviewed the literature with the aim of improving our understanding of the risk factors for CPB-associated AKI, which may increase our ability to prevent or improve this condition. Some novel early biomarkers for AKI have been introduced. In particular, a combinational use of these biomarkers would be helpful to improve clinical outcomes. Furthermore, we discuss several interventions that are aimed at managing CPB-associated AKI, may increase the effect of renal replacement therapy (RRT), and may contribute to preventing CPB-associated AKI. Collectively, the conclusions of this paper are limited by the availability of clinical trial evidence and conflicting definitions of AKI. A guideline is urgently needed for CPB-associated AKI.

Estrogen and estrogen receptors in kidney diseases

Acute kidney injury (AKI) and chronic kidney disease (CKD) are posing great threats to global health within this century. Studies have suggested that estrogen and estrogen receptors (ERs) play important roles in many physiological processes in the kidney. For instance, they are crucial in maintaining mitochondrial homeostasis and modulating endothelin-1 (ET-1) system in the kidney. Estrogen takes part in the kidney repair and regeneration via its receptors. Estrogen also participates in the regulation of phosphorus homeostasis via its receptors in the proximal tubule. The ERα polymorphisms have been associated with the susceptibilities and outcomes of several renal diseases. As a consequence, the altered or dysregulated estrogen/ERs signaling pathways may contribute to a variety of kidney diseases, including various causes-induced AKI, diabetic kidney disease (DKD), lupus nephritis (LN), IgA nephropathy (IgAN), CKD complications, etc. Experimental and clinical studies have shown that targeting estrogen/ERs signaling pathways might have protective effects against certain renal disorders. However, many unsolved problems still exist in knowledge regarding the roles of estrogen and ERs in distinct kidney diseases. Further research is needed to shed light on this area and to enable the discovery of pathway-specific therapies for kidney diseases.

Gender and coronary artery bypass grafting in cardiogenic shock

Purpose

Bypass surgery in patients undergoing cardiogenic shock caused by acute coronary syndrome is one of the most urgent and often performed cardiac operations. It remains unclear if patients gender independently influences the outcome. Literature reveals that females and males primarily differ from each other with regard to many important preoperative characteristics. Our objective was to compare the outcome and postoperative courses of both genders, using matched samples, eliminating these preoperative differences.

Methods

Between 2007 and 2015, 491 patients in cardiogenic shock underwent urgent bypass surgery in our institution. To assess the impact of gender on outcomes, we performed a propensity score matching to create two groups [males and females] which were matched for age, severity of shock, coronary artery disease morphology, and other comorbidities. Two groups were created: (1) 103 female and (2) 103 male patients. We analyzed the outcomes, complications and potential mortality predictors.

Results

Most of the patients had three-vessel disease (70.1%, n = 344) with proximal left anterior descending lesion (88%, n = 432). Our study showed no differences between female and male patients regarding choice of conduits, number of anastomosed vessels, and outcome. Acute kidney injury (AKI) occurred significantly more often in female patients and pericardial tamponade in their male counterparts. There were no differences regarding other major complications.

Conclusion

Gender does not appear to influence long-term outcomes in the study sample. Female gender is an independent risk factor for postoperative AKI. Other complications occurred with comparable rates in both genders. Exertion tolerance in the follow-up period was similar between genders.

Association of gender, age, and race on renal outcomes and mortality in patients with severe sepsis and septic shock

BACKGROUND

The association of age, gender and race with renal outcomes in patients with severe sepsis and septic shock (SEP) is not completely elucidated. We aimed to shed light on these relationships.

METHODS

We performed a retrospective cohort study of hospitalized patients in the USA discharged between January 1st, 2005 and December 31st, 2014 using the National Inpatient Sample. We adjusted analyses using the Charlson comorbidity index.

RESULTS

65,772,607 records were included of which 1,064,790 had SEP. There were 60% female and 12% African American (AA). The incidence of SEP was 1.6% and patients with SEP were older, had more AA and less females. Acute kidney injury (AKI) and mortality among patients with SEP were 62% and 30.7% respectively. AA race was associated with increased risk of SEP, AKI and dialysis, (OR = 1.12, 1.25 and 1.7 respectively, all p < 0.001). Female gender was associated with lower risk of all measured outcomes with odds ratios ranging from 0.65 to 0.78 (p < 0.001). Increasing age was associated with a higher risk of all outcomes except for dialysis.

CONCLUSION

Female gender is associated with a lower risk of poor renal outcomes and death among patients with SEP, while AA race places patients at higher risk of poor outcomes in that setting. Increasing age is generally associated with adverse outcomes.

Delayed remnant kidney function recovery is less observed in living donors who receive an analgesic, intrathecal morphine block in laparoscopic nephrectomy for kidney transplantation: a propensity score-matched analysis

BACKGROUND

This study analyzed remnant kidney function recovery in living donors after laparoscopic nephrectomy to establish a risk stratification model for delayed recovery and further investigated clinically modifiable factors.

PATIENTS AND METHODS

This retrospective study included 366 adult living donors who underwent elective donation surgery between January 2017 and November 2019 at our hospital. ITMB was included as an analgesic component in the living donor strategy for early postoperative pain relief from November 2018 to November 2019 (n = 116). Kidney function was quantified based on the estimated glomerular filtration rate (eGFR), and delayed functional recovery of remnant kidney was defined as eGFR < 60 mL/min/1.73 m² on postoperative day (POD) 1 (n = 240).

RESULTS

Multivariable analyses revealed that lower risk for development of eGFR < 60 mL/min/1.73 m² on POD 1 was associated with ITMB, female sex, younger age, and higher amount of hourly fluid infusion (area under the receiver operating characteristic curve = 0.783; 95% confidence interval = 0.734-0.832; p < 0.001). Propensity score (PS)-matching analyses showed that prevalence rates of eGFR < 60 mL/min/1.73 m² on PODs 1 and 7 were higher in the non-ITMB group than in the ITMB group. ITMB adjusted for PS was significantly associated with lower risk for development of eGFR < 60 mL/min/1.73 m² on POD 1 in PS-matched living donors. No living donors exhibited severe remnant kidney dysfunction and/or required renal replacement therapy at POD 7.

CONCLUSIONS

We found an association between the analgesic impact of ITMB and better functional recovery of remnant kidney in living kidney donors. In addition, we propose a stratification model that predicts delayed functional recovery of remnant kidney in living donors: male sex, older age, non-ITMB, and lower hourly fluid infusion rate.

Risk Stratification for Targeted AKI Prevention After Surgery: Biomarkers and Bundled Interventions

Perioperative acute kidney injury (AKI) is a surgery-associated complication with increasing incidence, not only because of enhanced awareness for the diagnosis, but also as a result of the aging society with a growing number of severe comorbidities undergoing major surgical procedures. The dilemma of AKI as a global health burden lies in the discrepancy between its importance as a significant risk factor for morbidity and mortality, and the unavailability of specific therapies to modify these adverse outcomes. Thus, it is all the more important to focus management on AKI prevention, and when AKI occurs to focus on early recognition and immediate adaption of individualized care. AKI is the result of an inter-relationship between patient susceptibility and determinants of perioperative exposures. Screening for constellations of risk factors along with measurement of novel biomarkers allows for early identification of patients who are susceptible to AKI and to initiate early targeted care. Targeted care involves implementation of a bundle of interventions adapted from a consensus management guideline, and is a strategy with growing evidence of a beneficial effect on patients' short- and long-term outcomes.

Perioperative acute kidney injury: Stratification and risk reduction strategies

Perioperative acute kidney injury (AKI) is associated with increased morbidity and mortality. Patient comorbidities, the type of surgery, timing of surgery, and exposure to nephrotoxins are important contributors for developing acute kidney injury. Urgent or emergent surgery, cardiac, and organ transplantation procedures are associated with a higher risk of acute kidney injury. Nephrotoxic drugs, contrast dye, and diuretics can worsen preexisting kidney dysfunction or act as an additive and/or synergistic insult to perioperative injury. A history of preoperative chronic kidney disease is the main risk factor for developing AKI, conferring as much as a 10-fold risk. However, beyond the preoperative renal function, the development of AKI is a complex phenomenon that involves a combination of patient-related and surgery-related factors.

Association of acute kidney injury with readmissions after hospitalization for acute exacerbation of chronic obstructive pulmonary disease: a population-based study

Background

Little is known about the relationship between acute kidney injury (AKI) and outcomes after acute exacerbation of chronic obstructive pulmonary disease (AECOPD). We aimed to investigate associations between AKI and readmission risks after hospitalization for AECOPD.

Methods

A retrospective, population-based cohort study using State Inpatient Databases from seven U.S. states (Arkansas, California, Florida, Iowa, Nebraska, New York, and Utah) from 2010 through 2013. We identified all adults (aged ≥40 years) hospitalized for AECOPD during the study period. Among them, we further identified patients with a concurrent diagnosis of new AKI. The outcome measures were any-cause readmissions within 30 days and 90 days after hospitalization for AECOPD. To determine associations between AKI and readmission risk, we constructed Cox proportional hazards models examining the time-to-readmission. We also identified the primary reason of readmission.

Results

We identified 356,990 patients hospitalized for AECOPD. The median age was 71 years and 41.9% were male. Of these, 24,833 (7.0%) had a concurrent diagnosis of AKI. Overall, patients with AKI had significantly higher risk of 30-day all-cause readmission compared to those without AKI (hazard ratio 1.47; 95% CI 1.43–1.51; P < 0.001). Likewise, patients with AKI had significantly higher risk of 90-day all-cause readmission (hazard ratio 1.35; 95% CI 1.32–1.38; P < 0.001). These associations remained significant after adjustment for confounders (both P < 0.05). Additionally, patients with AKI were likely to be readmitted for non-respiratory reasons including sepsis, acute renal failure, and congestive heart failure.

Conclusions

Among patients hospitalized for AECOPD, patients with AKI were at higher risk of 30-day and 90-day readmission, particularly with non-respiratory reasons.

Gender Differences in Postoperative Outcomes After Cardiac Surgery

Women presenting for cardiac surgery tend to be older and have hypertension, diabetes, and overweight or underweight body mass index than men. Despite improvements in surgical techniques and medications, women have increased risk for morbidity and mortality after multiple types of cardiac surgery. Women presenting for transcatheter aortic valve replacement are older and frailer than men, and have increased risk of intraoperative complications, but lower mortality at mid- and long-term ranges compared with men. Adherence to recovery and rehabilitation from cardiac surgery is challenging for women. Solutions should focus on increased family support, and use of group exercise and activities.

Heme oxygenase-2 protects against ischemic acute kidney injury: influence of age and sex

Heme oxygenase (HO) activity is exhibited by inducible (HO-1) and constitutive (HO-2) proteins. HO-1 protects against ischemic and nephrotoxic acute kidney injury (AKI). We have previously demonstrated that HO-2 protects against heme protein-induced AKI. The present study examined whether HO-2 is protective in ischemic AKI. Renal ischemia was imposed on young and aged HO-2+/+ and HO-2-/- mice. On days 1 and 2 after renal ischemia, there were no significant differences in renal function between young male HO-2+/+ and HO-2-/- mice, between young female HO-2+/+ and HO-2-/- mice, or between aged female HO-2+/+ and HO-2-/- mice. However, in aged male mice, HO-2 deficiency worsened renal function on days 1 and 2 after ischemic AKI, and, on day 2 after ischemia, such deficiency augmented upregulation of injury-related genes and worsened histological injury. Renal HO activity was markedly decreased in unstressed aged male HO-2-/- mice and remained so after ischemia, despite exaggerated HO-1 induction in HO-2-/- mice after ischemia. Such exacerbation of deficiency of HO-2 protein and HO activity may reflect phosphorylated STAT3, as activation of this proinflammatory transcription factor was accentuated early after ischemia in aged male HO-2-/- mice. This exacerbation may not reflect impaired induction of nephroprotectant genes, since the induction of HO-1, sirtuin 1, and β-catenin was accentuated in aged male HO-2-/- mice after ischemia. We conclude that aged male mice are hypersensitive to ischemic AKI and that HO-2 mitigates such sensitivity. We speculate that this protective effect of HO-2 may be mediated, at least in part, by suppression of phosphorylated STAT3-dependent signaling.