Perioperative acute kidney injury

Incidence, risk factors, and outcomes of the transition of HIPEC-induced acute kidney injury to acute kidney disease: a retrospective study

BACKGROUND

Acute kidney injury (AKI) is recognized as a common complication following cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). Characterized by prolonged renal function impairment, acute kidney disease (AKD) is associated with a higher risk of chronic kidney disease (CKD) and mortality.

METHODS

From January 2018 to December 2021, 158 patients undergoing CRS-HIPEC were retrospectively reviewed. Patients were separated into non-AKI, AKI, and AKD cohorts. Laboratory parameters and perioperative features were gathered to evaluate risk factors for both HIPEC-induced AKI and AKD, with the 90-day prognosis of AKD patients.

RESULTS

AKI developed in 21.5% of patients undergoing CRS-HIPEC, while 13.3% progressed to AKD. The multivariate analysis identified that ascites, GRAN%, estimated glomerular filtration rate (eGFR), and intraoperative (IO) hypotension duration were associated with the development of HIPEC-induced AKI. Higher uric acid, lessened eGFR, and prolonged IO hypotension duration were more predominant in patients proceeding with AKD. The AKD cohort presented a higher risk of 30 days of in-hospital mortality (14.3%) and CKD progression (42.8%).

CONCLUSIONS

Our study reveals a high incidence of AKI and AKI-to-AKD transition. Early identification of risk factors for HIPEC-induced AKD would assist clinicians in taking measures to mitigate the incidence.

Associations between hollow viscus injury and acute kidney injury in blunt abdominal trauma: A national trauma data bank analysis

PURPOSE

It is well established that hollow viscus perforation leads to sepsis and acute kidney injury (AKI) in non-trauma patients. However, the relationship between traumatic hollow viscus injury (HVI) and AKI is not well understood. Utilizing data from the National Trauma Data Bank, we investigated whether HVI serves as a risk factor for AKI. Additionally, we examined the characteristics of AKI in stable patients who underwent conservative treatment.

METHODS

We reviewed blunt abdominal trauma (BAT) cases from 2012 to 2015, comparing patients with and without AKI. Significant factors from univariate analysis were tested in a multivariate logistic regression (MLR) to identify independent AKI determinants. We also analyzed subsets: patients without HVI and stable patients given conservative management.

RESULTS

Out of the 563,040 BAT patients analyzed, 9073 (1.6%) developed AKI. While a greater proportion of AKI patients had HVI than those without AKI (13.3% vs. 5.2%, p < 0.001), this difference wasn't statistically significant in the MLR (p = 0.125). Notably, the need for laparotomy (odds = 3.108, p < 0.001) and sepsis (odds = 13.220, p < 0.001) were identified as independent risk factors for AKI. For BAT patients managed conservatively (systolic blood pressure >90 mmHg, without HVI or laparotomy; N = 497,066), the presence of sepsis was a significant predictor for the development of AKI (odds = 16.914, p < 0.001).

CONCLUSIONS

While HVI wasn't a significant risk factor for AKI in BAT patients, the need for laparotomy was. Stable BAT patients managed conservatively are still at risk for AKI due to non-peritonitis related sepsis.

Internal and External Validation of Machine Learning Models for Predicting Acute Kidney Injury Following Non-Cardiac Surgery Using Open Datasets

This study developed and validated a machine learning model to accurately predict acute kidney injury (AKI) after non-cardiac surgery, aiming to improve patient outcomes by assessing its clinical feasibility and generalizability. We conducted a retrospective cohort study using data from 76,032 adults who underwent non-cardiac surgery at a single tertiary medical center between March 2019 and February 2021, and used data from 5512 patients from the VitalDB open dataset for external model validation. The predictive variables for model training consisted of demographic, preoperative laboratory, and intraoperative data, including calculated statistical values such as the minimum, maximum, and mean intraoperative blood pressure. When predicting postoperative AKI, our gradient boosting machine model incorporating all the variables achieved the best results, with AUROC values of 0.868 and 0.757 for the internal and external validations using the VitalDB dataset, respectively. The model using intraoperative data performed best in internal validation, while the model with preoperative data excelled in external validation. In this study, we developed a predictive model for postoperative AKI in adult patients undergoing non-cardiac surgery using preoperative and intraoperative data, and external validation demonstrated the efficacy of open datasets for generalization in medical artificial modeling research.

Preliminary investigation of the effect of non-cardiac surgery on intraoperative islet and renal function: a single-center prospective cohort study

Background

The effect of different non-cardiac surgical methods on islet and renal function remains unclear. We conducted a preliminary investigation to determine whether different surgical methods affect islet function or cause further damage to renal function.

Methods

In this prospective cohort study, the clinical data of 63 adult patients who underwent non-cardiac surgery under general anesthesia were evaluated from February 2019 to January 2020. Patients were divided into the abdominal surgery group, the laparoscopic surgery group, and the breast cancer surgery group. The primary outcome was the difference between the effects of different surgical methods on renal function.

Results

Islet and renal function were not significantly different between the groups. The correlation analysis showed that hematocrit (HCT) and hemoglobin (HB) were negatively correlated with fasting plasma glucose (FPG) (p < 0.05), MAP was positively correlated with C-peptide (p < 0.05), and HCT and Hb were positively correlated with serum creatinine (SCr) (p < 0.05). Fasting insulin (FINS) and C-peptide were negatively correlated with SCr (p < 0.05), and the homeostatic model assessment of insulin resistance (HOMA-IR) was positively correlated with SCr (p < 0.05). FINS, C-peptide, HOMA-IR, and the homeostatic model assessment of β-cell function (HOMA-β) were positively correlated with cystatin C (Cys C) (p < 0.05).

Conclusion

FINS, C-peptide, and HOMA-IR had positive effects on beta-2-microglobulin (β2-MG). FINS, C-peptide, and HOMA-IR were positively correlated with Cys C and β2-Mg. While FINS and C-peptide were negatively correlated with SCr, HOMA-IR was positively correlated with SCr.

Development and external validation of multimodal postoperative acute kidney injury risk machine learning models

Objectives

To develop and externally validate machine learning models using structured and unstructured electronic health record data to predict postoperative acute kidney injury (AKI) across inpatient settings.

Materials and Methods

Data for adult postoperative admissions to the Loyola University Medical Center (2009-2017) were used for model development and admissions to the University of Wisconsin-Madison (2009-2020) were used for validation. Structured features included demographics, vital signs, laboratory results, and nurse-documented scores. Unstructured text from clinical notes were converted into concept unique identifiers (CUIs) using the clinical Text Analysis and Knowledge Extraction System. The primary outcome was the development of Kidney Disease Improvement Global Outcomes stage 2 AKI within 7 days after leaving the operating room. We derived unimodal extreme gradient boosting machines (XGBoost) and elastic net logistic regression (GLMNET) models using structured-only data and multimodal models combining structured data with CUI features. Model comparison was performed using the receiver operating characteristic curve (AUROC), with Delong's test for statistical differences.

Results

The study cohort included 138 389 adult patient admissions (mean [SD] age 58 [16] years; 11 506 [8%] African-American; and 70 826 [51%] female) across the 2 sites. Of those, 2959 (2.1%) developed stage 2 AKI or higher. Across all data types, XGBoost outperformed GLMNET (mean AUROC 0.81 [95% confidence interval (CI), 0.80-0.82] vs 0.78 [95% CI, 0.77-0.79]). The multimodal XGBoost model incorporating CUIs parameterized as term frequency-inverse document frequency (TF-IDF) showed the highest discrimination performance (AUROC 0.82 [95% CI, 0.81-0.83]) over unimodal models (AUROC 0.79 [95% CI, 0.78-0.80]).

Discussion

A multimodality approach with structured data and TF-IDF weighting of CUIs increased model performance over structured data-only models.

Conclusion

These findings highlight the predictive power of CUIs when merged with structured data for clinical prediction models, which may improve the detection of postoperative AKI.

Risk of chronic kidney disease in patients with acute kidney injury following a major surgery: a US claims database analysis

Background

Acute kidney injury (AKI) is a common complication after major surgery. This study assessed the risk of developing or worsening of chronic kidney disease (CKD) and other clinical outcomes in patients experiencing AKI after major surgery.

Methods

This retrospective observational study used Optum's de-identified Clinformatics Data Mart Database to investigate cardiorenal outcomes in adult patients at the first AKI event following major surgery. The primary outcome was CKD stage ≥3; secondary outcomes included myocardial infarction (MI), stroke, heart failure, all-cause hospitalization, end-stage kidney disease, need for dialysis or kidney transplant and composite measures. Follow-up was up to 3 years. Additionally, the effect of intercurrent events on the risk of clinical outcomes was assessed.

Results

Of the included patients (N = 31 252), most were male (61.9%) and White (68.9%), with a median age of 72 years (interquartile range 64-79). The event rates were 25.5 events/100 patient-years (PY) for CKD stage ≥3, 3.1 events/100 PY for end-stage kidney disease, 3.0 events/100 PY for dialysis and 0.1 events/100 PY for kidney transplants. Additionally, there were 6.9 events/100 PY for MI, 8.7 events/100 PY for stroke and 49.8 events/100 PY for all-cause hospitalization during follow-up. Patients with AKI relapses as intercurrent events were more likely to develop CKD stage ≥3 than those with just one AKI event after major surgery.

Conclusion

This analysis demonstrated that patients experiencing AKI following major surgery are at high risk of developing severe CKD or worsening of pre-existing CKD and other cardiorenal clinical outcomes such as MI and stroke.

Bilateral renal artery stenosis impacts postoperative complications after major vascular surgery

Background

Incidental atherosclerotic renal artery stenosis (RAS) is common in patients undergoing vascular surgery and has been shown to be associated with postoperative AKI among patients undergoing major non-vascular surgeries. We hypothesized that patients with RAS undergoing major vascular procedures would have a higher incidence of AKI and postoperative complications than those without RAS.

Methods

A single-center retrospective cohort study of 200 patients who underwent elective open aortic or visceral bypass surgery (100 with postoperative AKI; 100 without AKI) were identified. RAS was then evaluated by review of pre-surgery CTAs with readers blinded to AKI status. RAS was defined as ≥50 % stenosis. Univariate and multivariable logistic regression was used to assess association of unilateral and bilateral RAS with postoperative outcomes.

Results

17.4 % (n = 28) of patients had unilateral RAS while 6.2 % (n = 10) of patients had bilateral RAS. Patients with bilateral RAS had similar preadmission creatinine and GFR as compared to unilateral RAS or no RAS. 100 % (n = 10) of patients with bilateral RAS had postoperative AKI compared with 45 % (n = 68) of patients with unilateral or no RAS (p < 0.05). In adjusted logistic regression models, bilateral RAS predicted severe AKI (OR 5.82; CI 1.33, 25.53; p = 0.02), in-hospital mortality (OR 5.71; CI 1.03, 31.53; p = 0.05), 30-day mortality (OR 10.56; CI 2.03, 54.05; p = 0.005) and 90-day mortality (OR 6.88; CI 1.40, 33.87; p = 0.02).

Conclusions

Bilateral RAS is associated with increased incidence of AKI as well as in-hospital, 30-day, and 90-day mortality suggesting it is a marker of poor outcomes and should be considered in preoperative risk stratification.

The NephroCheck bedside system for detecting stage 3 acute kidney injury after open thoracoabdominal aortic repair

Acute kidney injury (AKI) is a common complication after complex aortic procedures and it is associated with relevant mortality and morbidity. Biomarkers for early and specific AKI detection are lacking. The aim of this work is to investigate the reliability of the NephroCheck bedside system for diagnosing stage 3 AKI following open aortic surgery. In this prospective, multicenter, observational study,- https://clinicaltrials.gov/ct2/show/NCT04087161 -we included 45 patients undergoing open thoracoabdominal aortic repair. AKI risk (AKIRisk-Index) was calculated from urine samples at 5 timepoints: baseline, immediately postoperatively and at 12, 24, 48, and 72 h post-surgery. AKIs were classified according to the KDIGO criteria. Contributing factors were identified in univariable and multivariable logistic regression. Predictive ability was assessed with the area under the receiver operator curve (ROCAUC). Among 31 patients (68.8%) that developed AKIs, 21 (44.9%) developed stage-3 AKIs, which required dialysis. AKIs were correlated with increased in-hospital mortality (p = .006), respiratory complications (p < .001), sepsis (p < .001), and multi-organ dysfunction syndrome (p < .001). The AKIRisk-Index showed reliable diagnostic accuracy starting at 24 h post-surgery (ROCAUC: .8056, p = .001). In conclusion, starting at 24 h after open aortic repair, the NephroCheck system showed adequate diagnostic accuracy for detecting the patients at risk for stage 3 AKIs.

Determination of Risk Factors for Postoperative Acute Kidney Injury in Patients With Gynecologic Malignancies

Background Postoperative acute kidney injury (AKI) is an important cause of mortality and morbidity among surgical patients. There is little information on the occurrence of AKI after operations for gynecologic malignancies. This study aimed to determine the incidence of AKI in patients who underwent surgery for gynecological malignancies and determine the risk factors in those who developed postoperative AKI. Methodology A total of 1,000 patients were enrolled retrospectively from January 2007 to March 2013. AKI was defined according to the Kidney Disease Improving Global Outcomes 2012 Clinical Practice Guideline for Acute Kidney Injury. Perioperative variables of patients were collected from medical charts. Results The incidence of postoperative AKI was 8.8%, with stage 1 occurring in 5.9%, stage 2 in 2.4%, and stage 3 in 0.5% of the patients. Patients who had AKI were significantly older, had higher body mass index (BMI) higher preoperative C-reactive protein (CRP) levels, and more frequently had a history of distant organ metastasis when compared with those who did not have AKI. When compared with patients who did not develop AKI postoperatively, longer operation times and intraoperative usage of higher amounts of erythrocyte suspension and fresh frozen plasma were seen in those who developed AKI. Conclusions Patients who had AKI were older, had higher BMI with higher preoperative CRP levels, more frequent distant organ metastasis, longer operation times, and higher amounts of blood transfused intraoperatively. Defining preoperative, intraoperative, and postoperative risk factors for postoperative AKI and taking necessary precautions are important for the early detection and intervention of AKI.

Association of Preoperative Prognostic Nutritional Index with Risk of Postoperative Acute Kidney Injury: A Meta-Analysis of Observational Studies

This meta-analysis aimed to assess the clinical association of the preoperative prognostic nutritional index (pre-PNI) with the risk of postoperative acute kidney injury. Four databases (e.g., Medline) were searched from inception to December 2022 to investigate the association between pre-PNI (i.e., low vs. high) and PO-PNI as well as the correlation between pre-PNI and other postoperative prognostic indices. Overall, 13 observational studies, including 9185 patients, were eligible for analysis. A low PNI was related to increased risks of PO-AKI [odd ratio (OR) = 1.65, p = 0.001, 3811 patients], postoperative infection (OR = 2.1, p < 0.00001, 2291 patients), and mortality (OR = 1.93, p < 0.0001, 2159 patients). Albeit statistically nonsignificant, a trend was noted, linking a low PNI to higher risks of postoperative bleeding (OR = 2.5, p = 0.12, 1157 patients) and stroke (OR = 1.62, p = 0.07, 2036 patients). Pooled results revealed a prolonged intensive care unit (ICU) stay in patients with low PNIs compared to those with high PNIs (MD: 0.98 days, p = 0.02, 2209 patients) without a difference in hospital stay between the two groups (MD: 1.58 days, p = 0.35, 2249 patients). This meta-analysis demonstrated an inverse correlation between PNI and the risks of PO-AKI, postoperative infection, and mortality, as well as the length of ICU stay, which warrants further investigations for verification.

Secreted Cytokines within the Urine of AKI Patients Modulate TP53 and SIRT1 Levels in a Human Podocyte Cell Model

Acute kidney injury (AKI) is a major kidney disease with a poor clinical outcome. It is a common complication, with an incidence of 10-15% of patients admitted to hospital. This rate even increases for patients who are admitted to the intensive care unit, with an incidence of >50%. AKI is characterized by a rapid increase in serum creatinine, decrease in urine output, or both. The associated symptoms include feeling sick or being sick, diarrhoea, dehydration, decreased urine output (although occasionally the urine output remains normal), fluid retention causing swelling in the legs or ankles, shortness of breath, fatigue and nausea. However, sometimes acute kidney injury causes no signs or symptoms and is detected by lab tests. Therefore, the identification of cytokines for the early detection and diagnosis of AKI is highly desirable, as their application might enable the prevention of the progression from AKI to chronic kidney disease (CKD). In this study, we analysed the secretome of the urine of an AKI patient cohort by employing a kidney-biomarker cytokine assay. Based on these results, we suggest ADIPOQ, EGF and SERPIN3A as potential cytokines that might be able to detect AKI as early as 24 h post-surgery. For the later stages, as common cytokines for the detection of AKI in both male and female patients, we suggest VEGF, SERPIN3A, TNFSF12, ANPEP, CXCL1, REN, CLU and PLAU. These cytokines in combination might present a robust strategy for identifying the development of AKI as early as 24 h or 72 h post-surgery. Furthermore, we evaluated the effect of patient and healthy urine on human podocyte cells. We conclude that cytokines abundant in the urine of AKI patients trigger processes that are needed to repair the damaged nephron and activate TP53 and SIRT1 to maintain the balance between proliferation, angiogenesis, and cell cycle arrest.

Incidence, risk factors and outcomes of acute kidney injury in surgical intensive care unit octogenarians at the Jordan University Hospital

BACKGROUND

Acute kidney damage (AKI) is among the most severe consequences observed in surgical intensive care units (SICUs). We aim to observe the incidence, risk factors, and outcomes of acute kidney injury in SICU octogenarians.

METHODS

A cross-sectional retrospective study was conducted at the SICU of Jordan University Hospital (JUH), a tertiary teaching hospital in a developing country, between January 2018 and December 2019. Patients who were 80 years or older at the time of data collection were included. The definition of AKI was based on Kidney Disease Improving Global Outcomes (KDIGO) criteria. Demographic, clinical, and laboratory data were reviewed.

RESULTS

A total number of 168 patients were included. The mean age was 84.0 ± 3.8 years, and 54.8% of the participants were women. Of those, 115 (68.5%) had surgery before or during ICU stay, and 28.7% of the patients' surgeries were an emergency surgery. Also, 47.8% of surgeries were considered by anesthesia to be high-risk surgeries. A total of 55 patients (32.7%) developed AKI during their SICU stay. The factors that were significantly associated with AKI in the ICU patients included use of beta blocker [AOR: 3.7; 95% CI: 1.2-11.8; p = 0.025], and inotropes [AOR:4.0; 95% CI: 1.2-13.3; p = 0.03]. The factors that were significantly associated with mortality in the ICU included using mechanical ventilation [AOR:18.7; 95% CI: 2.4-141.9; p = 0.005] and inotropes use [AOR: 12.3; 95% CI: 1.2-120.7; p = 0.031].

CONCLUSIONS

The incidence of AKI during SICU stay in this study was 32.7% and it was significantly associated with the use of beta blockers, mechanical ventilation, and inotropes. The mortality rate among octogenarians who developed AKI during SICU stay was 36.4%. Further studies are needed globally to assess the incidence of AKI in octogenarian surgical patients and identify risk factors to provide preventative measurements and strategies.

Optimization strategies of mesenchymal stem cell-based therapy for acute kidney injury

Considering the high prevalence and the lack of targeted pharmacological management of acute kidney injury (AKI), the search for new therapeutic approaches for it is in urgent demand. Mesenchymal stem cells (MSCs) have been increasingly recognized as a promising candidate for the treatment of AKI. However, clinical translation of MSCs-based therapies is hindered due to the poor retention and survival rates as well as the impaired paracrine ability of MSCs post-delivery. To address these issues, a series of strategies including local administration, three-dimensional culture, and preconditioning have been applied. Owing to the emergence and development of these novel biotechnologies, the effectiveness of MSCs in experimental AKI models is greatly improved. Here, we summarize the different approaches suggested to optimize the efficacy of MSCs therapy, aiming at promoting the therapeutic effects of MSCs on AKI patients.

Electrocardiographic Time-Intervals Waveforms as Potential Predictors for Severe Acute Kidney Injury in Critically Ill Patients

Background: Acute kidney injury (AKI) is common in critically ill patients admitted to intensive care units (ICU) and is frequently associated with poorer outcomes. Hence, if an indicator is available for predicting severe AKI within the first few hours of admission, management strategies can be put into place to improve outcomes. Materials and methods: This was a prospective, observational study, involving 63 critically ill patients, that aimed to explore the diagnostic accuracy of different Doppler parameters in predicting AKI in critically ill patients from a mixed ICU. Participants were enrolled at ICU admission. All underwent ultrasonographic examinations and hemodynamic assessment. Renal Doppler resistive index (RDRI), venous impedance index (VII), arterial systolic time intervals (a-STI), and venous systolic time intervals (v-STI) were measured within 2 h from ICU admission. Results: Cox proportional hazards models, including a-STI, v-STI, VII, and RDRI as independent variables, returned a-STI as the only putative predictor for the development of AKI or severe AKI. An overall statistically significant difference (p < 0.001) was observed in the Kaplan−Meier plots for cumulative AKI events between patients with a-STI higher or equal than 0.37 and for cumulative severe AKI-3 between patients with a-STI higher or equal than 0.63. As assessed by the area under the receiver operating curves (ROC) curves, a-STI performed best in diagnosing any AKI and/or severe AKI-3. Positive correlations were found between a-STI and the N-terminal brain natriuretic peptide precursor (NT-pro BNP) (ρ = 0.442, p < 0.001), the sequential organ failure assessment (SOFA) score (ρ: 0.361, p = 0.004), and baseline serum creatinine (ρ: 0.529, p < 0.001). Conclusions: Critically ill patients who developed AKI had statistically significant different a-STI (on admission to ICU), v-STI, and VII than those who did not. Moreover, a-STI was associated with the development of AKI at day 5 and provided the best diagnostic accuracy for the diagnosis of any AKI or severe AKI compared with RDRI, VII, and v-STI.

Implementation of a new definition for acute kidney injury in the National Surgical Quality Improvement Project: What is the impact?

BACKGROUND

The National Surgical Quality Improvement Project is the preeminent surgical quality database, but it undercaptures acute kidney injury. Recently, the National Surgical Quality Improvement Project lowered the thresholds for acute kidney injury for the first time, so we assessed the impact of implementing the definition change on the rate of acute kidney injuries.

METHODS

For this interrupted time series analysis, we assembled 2 institutional National Surgical Quality Improvement Project files to identify adults undergoing inpatient noncardiac nonvascular surgery. The acute kidney injury definition changed on July 1, 2021, so patients were stratified by their operative date into 12-month pre and post groups. Weighted covariate propensity score matching and logistic regression were used to balance the periods and compare outcomes.

RESULTS

In total, 4,784 adults were eligible (55% pre and 45% post change). The overall rate of postoperative outcomes was similar, aside for acute kidney injury (pre 0.3%, post 5.6%, P < .0001). Regardless of the period, patients with acute kidney injuries had significantly longer lengths of stay and morbidity and mortality rates compared to those without an acute kidney injury. After the definition change, 81% of acute kidney injuries were stage I, and none were identified by urine output alone. After matching, surgery after the definition change was associated with an increased weighted odds of an acute kidney injury compared to surgery before the change (odds ratio 26.2; 95% confidence interval, 12.1-56.8).

CONCLUSION

In the year after the definition change, there was a 1,700% relative increase in the rate of reported acute kidney injuries. Newly identified acute kidney injuries are associated with high complication rates, and this definition change has implications for patient counseling, research, and quality reporting.

The Beneficial Effects of Bariatric-Surgery-Induced Weight Loss on Renal Function

Obesity represents an independent risk factor for the development of chronic kidney disease (CKD), leading to specific histopathological alterations, known as obesity-related glomerulopathy. Bariatric surgery is the most effective means of inducing and maintaining sustained weight loss. Furthermore, in the context of bariatric-surgery-induced weight loss, a reduction in the proinflammatory state and an improvement in the adipokine profile occur, which may also contribute to the improvement of renal function following bariatric surgery. However, the assessment of renal function in the context of obesity and following marked weight loss is difficult, since the formulas adopted to estimate glomerular function use biomarkers whose production is dependent on muscle mass (creatinine) or adipose tissue mass and inflammation (cystatin-c). Thus, following bariatric surgery, the extent to which reductions in plasma concentrations reflect the actual improvement in renal function is not clear. Despite this limitation, the available literature suggests that in patients with hyperfiltration at baseline, GFR is reduced following bariatric surgery, whereas GFR is increased in patients with decreased GFR at baseline. These findings are also confirmed in the few studies that have used measured rather than estimated GFR. Albuminuria is also decreased following bariatric surgery. Moreover, bariatric surgery seems superior in achieving the remission of albuminuria and early CKD than the best medical treatment. In this article, we discuss the pathophysiology of renal complications in obesity, review the mechanisms through which weight loss induces improvements in renal function, and provide an overview of the renal outcomes following bariatric surgery.

Postoperative acute kidney injury requiring continuous renal replacement therapy and outcomes after coronary artery bypass grafting: a nationwide cohort study

BACKGROUND

Previous studies reported that patients with acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT) after cardiac surgery were at a higher risk of postoperative mortality. However, the impact of AKI and CRRT on long-term mortality has not yet been identified. Therefore, we investigated whether postoperative AKI requiring CRRT was associated with one-year all-cause mortality after coronary artery bypass grafting (CABG).

METHODS

For this population-based cohort study, we analyzed data from the National Health Insurance Service database in South Korea. The cohort included all adult patients diagnosed with ischemic heart disease who underwent isolated CABG between January 2012 and December 2017.

RESULTS

A total of 15,115 patients were included in the analysis, and 214 patients (1.4%) required CRRT for AKI after CABG during hospitalization. They received CRRT at 3.1 ± 8.5 days after CABG, for 3.1 ± 7.8 days. On multivariable Cox regression, the risk of 1-year all-cause mortality in patients who underwent CRRT was 7.69-fold higher. Additionally, on multivariable Cox regression, the 30-day and 90-day mortality after CABG in patients who underwent CRRT were 18.20-fold and 20.21-fold higher than the normal value, respectively. Newly diagnosed chronic kidney disease (CKD) requiring renal replacement therapy (RRT) 1 year after CABG in patients who underwent CRRT was 2.50-fold higher. In the generalized log-linear Poisson model, the length of hospital stay (LOS) in patients who underwent CRRT was 5% longer.

CONCLUSIONS

This population-based cohort study showed that postoperative AKI requiring CRRT was associated with a higher 1-year all-cause mortality after CABG. Furthermore, it was associated with a higher rate of 30-day and 90-day mortality, longer LOS, and higher rate of CKD requiring RRT 1 year after CABG. Our results suggest that CRRT-associated AKI after CABG may be associated with an increased risk of mortality; hence, there should be interventions in these patients after hospital discharge.

Evaluation of Serum Cyclooxygenase, Hepcidin Levels in Acute Renal Injury (AKI) Patients Following Cardiac Catheterization

Background

Acute kidney damage is a severe condition common in patients who have undergone heart surgery (catheterization) and secondary injury is also referred to as being synonymous with surgery. The goal of this research is to determine the rate of cyclooxygenase and hepcidin levels in patients with acute renal injury (AKI) following cardiac catheterization.

Methods

The study is performed on (81) patients (64 males and 17 females) aged 40-75 years. Data from most patients are reported in the form of age, gender, and smoking background questionnaire.

Results

The results indicate a significant increase in serum levels of cyclooxygenase and hepcidin levels in patients with severe renal insufficiency after cardiac catheterization by (79%) males versus (21%) females.

Conclusion

In this study, improved risk prediction could enhance patient monitoring and treatment after surgery, direct patient treatment and decision making, and enhance participation in AKI interventional trials.

The effects of acute kidney injury in a multicenter cohort of high-risk surgical patients

BACKGROUND AND OBJECTIVES

Patients who develop post-operative acute kidney injury (AKI) have a poor prognosis, especially when undergoing high-risk surgery. Therefore, the objective of this study was to evaluate the outcome of patients with AKI acquired after non-cardiac surgery and the possible risk factors for this complication.

METHODS

A multicenter, prospective cohort study with patients admitted to intensive care units (ICUs) after non-cardiac surgery was conducted to assess whether they developed AKI. The patients who developed AKI were then compared to non-AKI patients.

RESULTS

A total of 29 ICUs participated, of which 904 high-risk surgical patients were involved in the study. The occurrence of AKI in the post-operative period was 15.8%, and the mortality rate of post-operative AKI patients at 28 days was 27.6%. AKI was strongly associated with 28-day mortality (OR = 2.91; 95% CI 1.51-5.62; p = 0.001), and a higher length of ICU and hospital stay (p < 0.001). Independent factors for the risk of developing AKI were pre-operative anemia (OR = 7.01; 95% CI 1.69-29.07), elective surgery (OR = 0.45; 95% CI 0.21-0.97), SAPS 3 (OR = 1.04; 95% CI 1.02-1.06), post-operative vasopressor use (OR = 2.47; 95% CI 1.34-4.55), post-operative infection (OR = 8.82; 95% CI 2.43-32.05) and the need for reoperation (OR= 7.15; 95% CI 2.58-19.79).

CONCLUSION

AKI was associated with the risk of death in surgical patients and those with anemia before surgery, who had a higher SAPS 3, needed a post-operative vasopressor, or had a post-operative infection or needed reoperation were more likely to develop AKI post-operatively.

Renal outcomes of laparoscopic versus open surgery in patients with rectal cancer: a propensity score analysis

Background

A laparoscopic approach is widely used in abdominal surgery. Although several studies have compared surgical and oncological outcomes between laparoscopic surgery (LS) and open surgery (OS) in rectal cancer patients, there have been few studies on postoperative renal outcomes.

Methods

We conducted a retrospective cohort study involving 1,633 patients who underwent rectal cancer surgery between 2003 and 2017. Postoperative acute kidney injury (AKI) was diagnosed according to the serum creatinine criteria of the Kidney Disease: Improving Global Outcomes classification.

Results

Among the 1,633 patients, 1,072 (65.6%) underwent LS. After matching propensity scores, 395 patients were included in each group. The incidence of postoperative AKI in the LS group was significantly lower than in the OS group (9.9% vs. 15.9%; p = 0.01). Operation time, estimated blood loss, and incidence of transfusion in the LS group were significantly lower than those in the OS group. Cox proportional hazard models revealed that LS was associated with decreased risk of postoperative AKI (hazard ratio [HR], 0.599; 95% confidence interval [CI], 0.402–0.893; p = 0.01) and postoperative transfusion was associated with increased risk of AKI (HR, 2.495; 95% CI, 1.529–4.072; p < 0.001). In the subgroup analysis, the incidence of postoperative AKI in patients with middle or high rectal cancer who underwent LS was much lower than in those who underwent OS (HR, 0.373; 95% CI, 0.197–0.705; p = 0.002).

Conclusion

This study showed that LS may have a favorable effect on the development of postoperative AKI in patients with rectal cancer.

Perioperative Serum Free Hemoglobin and Haptoglobin Levels in Valvular and Aortic Surgery With Cardiopulmonary Bypass: Their Associations With Postoperative Kidney Injury

OBJECTIVE

To observe the perioperative free hemoglobin and haptoglobin levels and to assess their associations with the risk of postoperative acute kidney injury (pAKI) in adult patients undergoing valvular and aortic surgery requiring cardiopulmonary bypass (CPB).

DESIGN

A single-center, prospective, observational study.

SETTING

Public teaching hospital.

PARTICIPANTS

The study comprised 74 adult patients without chronic renal failure who underwent cardiovascular surgery requiring CPB from 2014 to 2020.

MEASUREMENTS AND MAIN RESULTS

Perioperative free hemoglobin and haptoglobin levels during the study period were obtained from study participants. The primary outcome was pAKI defined by the Kidney Disease: Improving Global Outcomes criteria. Of the 74 patients in this study, pAKI occurred in 25 patients (33.8%). The free hemoglobin level began to increase after the initiation of CPB and reached a peak level at 30 minutes after weaning from CPB. It returned to the baseline level on postoperative day one. Haptoglobin levels were the highest after anesthesia induction and decreased continuously until postoperative day one. In the multivariate analysis, maximum free hemoglobin and minimum haptoglobin were associated independently with increased risk of pAKI (adjusted odds ratio 1.33 [95% confidence interval 1.12-1.58; p = 0.001] and 0.95 [95% confidence interval 0.91-1.00; p = 0.03], respectively). The free hemoglobin level began to have an independent association with pAKI at one hour after commencement of CPB, and the independent association disappeared at postoperative day one.

CONCLUSIONS

This study found that the perioperative increase of the free hemoglobin level and the decrease of the haptoglobin level had independent associations with the risk of pAKI.

Application of mesenchymal stem cell-derived exosomes in kidney diseases

Kidney injury (KI) has high morbidity and mortality; there has been no ideal practical treatment available in clinical practice until now. Exosomes are formed from fusing multisubunit body membranes and are secreted into the extracellular matrix, intercellular communication membracusses. As a cell-free treatment, it offers a new approach to the treatment of KI. Exosomes are spherical vesicles with or no separator cup that shapes proteins, and RNA acts on the target cells through various means to promote tissue damage and mitigate apoptosis, both inflammation and oxidative stress. Exosomes derived from mesenchymal stem cells (MSC) have a paracrine function in promoting tissue repair and immune regulation. The MSC-Exos provide specific benefits over the MSCs. The urinary exosomes closely follow the functions and diseases of the kidneys. Though much of the research in this field is only at the preliminary stages, previous research has demonstrated that MSC-Exos damaged tissues to offer proteins, mRNAs, and microRNAs as remedies for kidney injury. Although exosomes' role in tissue repair is currently is greatly debated, several key issues remain unaddressed. This is a summarization of the work done concerning MSC in the treatment of KI.

Comprehensive Comparisons among Inotropic Agents on Mortality and Risk of Renal Dysfunction in Patients Who Underwent Cardiac Surgery: A Network Meta-Analysis of Randomized Controlled Trials

Several kinds of inotropes have been used in critically ill patients to improve hemodynamics and renal dysfunction after cardiac surgery; however, the treatment strategies for reducing mortality and increasing renal protection in patients who underwent cardiac surgery remain controversial. Therefore, we performed a comprehensive network meta-analysis to overcome the lack of head-to-head comparisons. A systematic database was searched up to 31 December 2020, for randomized controlled trials that compared different inotropes on mortality outcomes and renal protective effects after cardiac surgery. A total of 29 trials were included and a frequentist network meta-analysis was performed. Inconsistency analyses, publication bias, and subgroup analyses were also conducted. Compared with placebo, use of levosimendan significantly decreased the risks of mortality (odds ratio (OR): 0.74; 95% confidence interval (CI): 0.56–0.97) and risk of acute renal injury (OR: 0.61; 95% CI: 0.45–0.82), especially in low systolic function patients. Use of levosimendan also ranked the best treatment based on the P-score (90.1%), followed by placebo (64.5%), milrinone (49.6%), dopamine (49.5%), dobutamine (29.1%), and fenoldopam (17.0%). Taking all the available data into consideration, levosimendan was a safe renal-protective choice for the treatment of patients undergoing cardiac surgery, especially for those with low systolic function.

Intraoperative oliguria does not predict postoperative acute kidney injury in major abdominal surgery: a cohort analysis

BACKGROUND

Acute kidney injury (AKI) is a common complication in patients undergoing major abdominal surgery and is associated with considerable morbidity and mortality. Several studies investigating the association between intraoperative urine output and postoperative AKI have shown conflicting results. Here, we investigated the association of intraoperative oliguria with postoperative AKI in a cohort of patients submitted to elective major abdominal surgery.

METHODS

This was a single-center retrospective analysis of adult patients who underwent elective major abdominal surgery from January 2016 to December 2018. AKI was defined according to the serum creatinine criteria of the KDIGO classification. Intraoperative oliguria was defined as urine output of less than 0.5 mL/kg/h. Risk factors were evaluated using multivariate logistic regression analysis.

RESULTS

A total of 165 patients were analyzed. In the first 48 h after surgery the incidence of AKI was 19.4%. Postoperative AKI was associated with hospital mortality (p=0.011). Twenty percent of patients developed intraoperative oliguria. There was no association between preexisting comorbidities and development of intraoperative oliguria. There was no correlation between the type of anesthesia used and occurrence of intraoperative oliguria, but longer anesthesia time was associated with intraoperative oliguria (p=0.007). Higher baseline SCr (p=0.001), need of vasoactive drugs (p=0.007), and NSAIDs use (p=0.022) were associated with development of intraoperative oliguria. Intraoperative oliguria was not associated with development of postoperative AKI (p=0.772), prolonged hospital stays (p=0.176) or in-hospital mortality (p=0.820).

CONCLUSION

In this cohort of patients we demonstrated that intraoperative oliguria does not predict postoperative AKI in major abdominal surgery.

A visual risk assessment tool for acute kidney injury after intracranial aneurysm clipping surgery

Objective

The aim of the study was to establish a predictive postoperative nomogram for acute kidney injury (AKI) after intracranial aneurysm clipping surgery, in order to early identify patients with high postoperative AKI risk.

Methods

This is a retrospective study, which included patients who underwent intracranial aneurysm clipping surgery. Multivariate logistic regression was employed to select confound factors that associated with AKI, then incorporated into the nomogram. The predictive accuracy of the model was assessed by concordance index (C-Index).

Results

A total of 365 patients after intracranial aneurysm clipping surgery were enrolled in the study eventually, of which 68 (18.63%) suffered postoperative AKI, and the incidence of stage 1, stage 2 and stage 3 were 92.65% (63/68), 5.88% (4/68), and 1.47% (1/68), respectively. Univariate logistic regression revealed that high density lipoprotein (HDL), prothrombin time (PT), estimated glomerular filtration rate (eGFR), size of aneurysm ≥10 mm, and aneurysm ruptured before surgery were associated with AKI after surgery, while multivariate logistic regression showed same results as the size of aneurysm ≥10 mm and aneurysm ruptured were independent AKI risk factors. In addition, the nomogram demonstrated a good accuracy in estimating intracranial aneurysm clipping associated AKI, as a C-Index and a bootstrap-corrected one of 0.772 and 0.737, respectively. Moreover, calibration plots showed consistency with the actual presence of AKI.

Conclusion

The novel nomogram model can serve as a promising predictive tool to improve the identification of AKI among those who underwent intracranial aneurysm clipping surgery.

Analysis of the risk factors of acute kidney injury after total hip or knee replacement surgery

Background

Postoperative acute kidney injury (AKI), which increases the risk of postoperative morbidity and mortality, poses a major concern to surgeons. We conducted this study to analyze the risk factors associated with the occurrence of AKI after orthopedic surgery.

Methods

This was a retrospective study that included 351 patients who underwent total hip or knee replacement surgery at Inje University Haeundae Paik Hospital between January 2012 and December 2016.

Results

AKI occurred in 13 (3.7%) of the 351 patients. The patients’ preoperative estimated glomerular filtration rate (eGFR) was 66.66±34.02 mL/min/1.73 m² in the AKI group and 78.07±21.23 mL/min/1.73 m² in the non-AKI group. The hemoglobin levels were 11.21±1.65 g/dL in the AKI group and 12.39±1.52 g/dL in the non-AKI group. Hemoglobin level was related to increased risk of AKI (odds ratio [OR], 0.13; 95% confidence interval [CI], 0.02–0.68; p=0.016). Administration of crystalloid or colloid fluid alone and the perioperative amount of fluid did not show any significant relationship with AKI. Further analysis of the changes in eGFR was performed using a cutoff value of 7.54. The changes in eGFR were significantly related to decreased risk of AKI (OR, 0.74; 95% CI, 0.61–0.89; p=0.002).

Conclusion

Renal function should be monitored closely after orthopedic surgery if patients have chronic kidney disease and low hemoglobin level. Predicting the likelihood of AKI occurrence, early treatment of high-risk patients, and monitoring perioperative laboratory test results, including eGFR, will help improve patient prognosis.

Renal functional reserve: from physiological phenomenon to clinical biomarker and beyond

Glomerular filtration rate (GFR) is acutely increased following a high-protein meal or systemic infusion of amino acids. The mechanisms underlying this renal functional response remain to be fully elucidated. Nevertheless, they appear to culminate in preglomerular vasodilation. Inhibition of the tubuloglomerular feedback signal appears critical. However, nitric oxide, vasodilator prostaglandins, and glucagon also appear important. The increase in GFR during amino acid infusion reveals a "renal reserve," which can be utilized when the physiological demand for single nephron GFR increases. This has led to the concept that in subclinical renal disease, before basal GFR begins to reduce, renal functional reserve can be recruited in a manner that preserves renal function. The extension of this concept is that once a decline in basal GFR can be detected, renal disease is already well progressed. This concept likely applies both in the contexts of chronic kidney disease and acute kidney injury. Critically, its corollary is that deficits in renal functional reserve have the potential to provide early detection of renal dysfunction before basal GFR is reduced. There is growing evidence that the renal response to infusion of amino acids can be used to identify patients at risk of developing either chronic kidney disease or acute kidney injury and as a treatment target for acute kidney injury. However, large multicenter clinical trials are required to test these propositions. A renewed effort to understand the renal physiology underlying the response to amino acid infusion is also warranted.

The Role of Ribonuclease 1 and Ribonuclease Inhibitor 1 in Acute Kidney Injury after Open and Endovascular Thoracoabdominal Aortic Aneurysm Repair

Acute kidney injury (AKI) is one of the most common post-operative complications and is closely associated with increased mortality after open and endovascular thoracoabdominal aortic aneurysm (TAAA) repair. Ribonuclease (RNase) 1 belongs to the group of antimicrobial peptides elevated in septic patients and indicates the prediction of two or more organ failures. The role of RNase 1 and its antagonist RNase inhibitor 1 (RNH1) after TAAA repair is unknown. In this study, we analyzed RNase 1 and RNH1 serum levels in patients undergoing open (n = 14) or endovascular (n = 19) TAAA repair to determine their association with post-operative AKI and in-hospital mortality. Increased RNH1 serum levels after open TAAA repair as compared with endovascular TAAA repair immediately after surgery and 12, 48, and 72 h after surgery (all p < 0.05) were observed. Additionally, elevated RNase 1 and RNH1 serum levels 12, 24, and 48 h after surgery were shown to be significantly associated with AKI (all p < 0.05). RNH1 serum levels before and RNase 1 serum levels 12 h after TAAA repair were significantly correlated with in-hospital mortality (both p < 0.05). On the basis of these findings, RNase 1 and RNH1 may be therapeutically relevant and may represent biomarkers for post-operative AKI and in-hospital mortality.

Management of Acute Kidney Injury Following Major Abdominal Surgery: A Contemporary Review

Acute kidney injury (AKI) is a frequent occurrence following major abdominal surgery and is independently associated with both in-hospital and long-term mortality, as well as with a higher risk of progressing to chronic kidney disease (CKD) and cardiovascular events. Postoperative AKI can account for up to 40% of in-hospital AKI cases. Given the differences in patient characteristics and the pathophysiology of postoperative AKI, it is inappropriate to assume that the management after noncardiac and nonvascular surgery are the same as those after cardiac and vascular surgery. This article provides a comprehensive review on the available evidence on the management of postoperative AKI in the setting of major abdominal surgery.

Acute Kidney Injury: A Frequently Underestimated Problem in Perioperative Medicine

BACKGROUND

Surgical patients are getting older with increasing comorbidity. Acute kidney injury (AKI) is a commonly underesti- mated perioperative complication. 2-18% of hospitalized patients and 22-57% of patients in the intensive care unit develop AKI. Even though it has a major impact on patients' outcomes, it goes unrecognized in 57-75.6% of cases.

METHODS

This review is based on pertinent papers retrieved by a selective search in PubMed and the Cochrane Library employ- ing the searching terms "acute kidney injury," "biomarker," "perioperative," "renal function," and "KDIGO."

RESULTS

The pathophysiology of AKI is complex. Conventional biomarkers are either not specific enough (urine output) or not sensitive enough (serum creatinine) for timely diagnosis. In view of the pathophysiology of the condition and the limited treat- ment options for it, the early detection of subclinical AKI (kidney damage without functional impairment) would seem to be a reasonable first step toward the prevention of worsening or permanent renal injury. New biomarkers of damage enable the early initiation of nephroprotective interventions. According to the "Kidney Disease: Improving Global Outcomes" (KDIGO) statement, a multimodal treatment approach is needed, including, among other things, optimization of hemodynamics and the discontinu- ation of nephrotoxic drugs.

CONCLUSION

It is essential to identify patients at risk and sensitize the treating personnel to the implementation of the guidelines. The incorporation of new biomarkers into routine clinical practice is also reasonable and necessary. Future clinical trials must show in what form these biomarkers should be used (singly or collectively).

Prerenal acute kidney injury—still a relevant term in modern clinical practice?

The traditional taxonomy of acute kidney injury (AKI) has remained pervasive in clinical nephrology. While the terms ‘prerenal’, ‘intrarenal’ and ‘postrenal’ highlight the diverse pathophysiology underlying AKI, they also imply discrete disease pathways and de-emphasize the nature of AKI as an evolving clinical syndrome with multiple, often simultaneous and overlapping, causes. In a similar vein, prerenal AKI comprises a diverse spectrum of kidney disorders, albeit one that is often managed by using a standardized clinical algorithm. We contend that the term ‘prerenal’ is too vague to adequately convey our current understanding of hypoperfusion-related AKI and that it should thus be avoided in the clinical setting. Practice patterns among nephrologists indicate that AKI-related terminology plays a significant role in the approaches that clinicians take to patients that have this complex disease. Thus, it appears that precise terminology does impact the treatment that patients receive. We will outline differences in the diagnosis and management of clinical conditions lying on the so-called prerenal disease spectrum to advocate caution when administering intravenous fluids to these clinically decompensated patients. An understanding of the underlying pathophysiology may, thus, avert clinical missteps such as fluid and vasopressor mismanagement in tenuous or critically ill patients.

Preoperative Risk and the Association between Hypotension and Postoperative Acute Kidney Injury

BACKGROUND

Despite the significant healthcare impact of acute kidney injury, little is known regarding prevention. Single-center data have implicated hypotension in developing postoperative acute kidney injury. The generalizability of this finding and the interaction between hypotension and baseline patient disease burden remain unknown. The authors sought to determine whether the association between intraoperative hypotension and acute kidney injury varies by preoperative risk.

METHODS

Major noncardiac surgical procedures performed on adult patients across eight hospitals between 2008 and 2015 were reviewed. Derivation and validation cohorts were used, and cases were stratified into preoperative risk quartiles based upon comorbidities and surgical procedure. After preoperative risk stratification, associations between intraoperative hypotension and acute kidney injury were analyzed. Hypotension was defined as the lowest mean arterial pressure range achieved for more than 10 min; ranges were defined as absolute (mmHg) or relative (percentage of decrease from baseline).

RESULTS

Among 138,021 cases reviewed, 12,431 (9.0%) developed postoperative acute kidney injury. Major risk factors included anemia, estimated glomerular filtration rate, surgery type, American Society of Anesthesiologists Physical Status, and expected anesthesia duration. Using such factors and others for risk stratification, patients with low baseline risk demonstrated no associations between intraoperative hypotension and acute kidney injury. Patients with medium risk demonstrated associations between severe-range intraoperative hypotension (mean arterial pressure less than 50 mmHg) and acute kidney injury (adjusted odds ratio, 2.62; 95% CI, 1.65 to 4.16 in validation cohort). In patients with the highest risk, mild hypotension ranges (mean arterial pressure 55 to 59 mmHg) were associated with acute kidney injury (adjusted odds ratio, 1.34; 95% CI, 1.16 to 1.56). Compared with absolute hypotension, relative hypotension demonstrated weak associations with acute kidney injury not replicable in the validation cohort.

CONCLUSIONS

Adult patients undergoing noncardiac surgery demonstrate varying associations with distinct levels of hypotension when stratified by preoperative risk factors. Specific levels of absolute hypotension, but not relative hypotension, are an important independent risk factor for acute kidney injury.

Agency for Healthcare Research and Quality Patient Safety Indicators and Mortality in Surgical Patients

Patient safety indicators (PSI), developed by the Agency for Healthcare Research and Quality, use administrative billing data to measure and compare patient safety events at medical centers. We retrospectively examined whether PSIs accurately reflect patients’ risk of mortality, hospital length of stay, and intensive care unit (ICU) requirements at an academic medical center. Surgical patient records with PSIs were reviewed between October 2011 and September 2012 at our urban academic medical center. Primary outcomes studied included mortality, hospital length of stay, and ICU requirements. Subset analysis was performed for each PSI and its association with the outcome measures. PSIs were more common among surgical patients who died as compared with those alive at discharge (35.3 vs 2.7 PSIs/100 patients, P < 0.01). Although patients who died with PSIs had shorter hospital courses, they had a significantly greater ICU requirement than those without a PSI (96.0 vs 61.1%, P < 0.01) and patients who were alive at discharge (96.0 vs 48.0%, P < 0.01). The most frequently associated PSIs with mortality were postoperative metabolic derangements (41.7%), postoperative sepsis (38.5%), and pressure ulcers (33.3%). PSIs occur at a higher frequency in surgical patients who die and are associated with increased ICU requirements.

Metabolic reprogramming associated with progression of renal ischemia reperfusion injury assessed with hyperpolarized [1-13C]pyruvate

Acute kidney injury is a major clinical challenge affecting as many as 1 percent of all hospitalized patients. Currently it is not possible to accurately stratify and predict the outcome of the individual patient. Increasing evidence supports metabolic reprogramming as a potential target for new biomarkers. Hyperpolarized [1-¹³C]pyruvate imaging is a promising new tool for evaluating the metabolic status directly in the kidneys. We here investigate the prognostic potential of hyperpolarized [1-¹³C]pyruvate in the setting of acute kidney injury in a rodent model of ischemia reperfusion. A significant correlation was found between the intra-renal metabolic profile 24 hours after reperfusion and 7 days after injury induction, as well as a correlation with the conventional plasma creatinine biomarker of renal function and markers of renal injury. This leads to a possible outcome prediction of renal function and injury development from a metabolic profile measured in vivo. The results support human translation of this new technology to renal patients as all experiements have been performed using clinical MRI equipment.

Transient and Persistent AKI and Outcomes in Patients Undergoing Major Abdominal Surgery

INTRODUCTION

Acute kidney injury (AKI) is a frequent diagnosis in surgical patients which has a detrimental effect on short-term and long-term outcomes. The purpose of this study was to evaluate the incidence and predictive factors of transient and persistent postoperative AKI in patients submitted to major abdominal surgery and to characterize the impact of AKI on in-hospital mortality.

METHODS

This study was a cross-examination of a retrospective analysis of clinical data of 450 patients who underwent major abdominal surgery from January 2010 to February 2011. Only AKI developing in the first 48 h after surgery was considered. AKI was diagnosed using the Kidney Disease: Improving Global Outcome (KDIGO) classification based on both serum creatinine (SCr) and urine output criteria. Persistent and transient AKI were defined according to the Acute Disease Quality Initiative (ADQI) workgroup definitions.

RESULTS

In our study, 22.4% of patients developed AKI in the first 48 h post-surgery (n = 101), and 48% of patients had persistent AKI (n = 49), defined as postoperative AKI, with a duration of more than 48 h. Older age (adjusted odds ratio [OR] 1.06 [1.00-1.11], p = 0.039), hypertension (adjusted OR 4.60 [1.17-18.11], p = 0.029), and higher preoperative SCr (adjusted OR 22.67 [4.00-128.46], p < 0.001) were independent predictors of persistent AKI. The overall in-hospital mortality was 6.4% (n = 29). Persistent AKI was associated with higher mortality than transient AKI (51.9 vs. 20.7%; unadjusted OR 13.03 [5.78-29.36], p < 0.001; adjusted OR 4.20 [1.02-17.27], p = 0.047).

CONCLUSION

In this cohort of patients submitted to major abdominal surgery, persistent AKI was an independent predictor of in-hospital mortality in contrast to transient AKI.

Acute kidney injury is associated with increased healthcare utilization, complications, and mortality after primary total knee arthroplasty

Background:

The objective of this study was to assess healthcare utilization and complications associated with acute kidney injury (AKI) in patients undergoing primary total knee arthroplasty (TKA).

Methods:

We used the 1998–2014 US National Inpatient Sample to assess whether AKI is associated with healthcare utilization or in-hospital postoperative complications post-TKA using multivariable-adjusted logistic regression analyses. We calculated odds ratios (ORs) and a 95% confidence intervals (CIs). Sensitivity analyses additionally adjusted for hospital characteristics (location/teaching status, bed size, and region).

Results:

Of the 8,127,282 people who underwent primary TKA from 1998 to 2014, 104,366 (1.3%) had a diagnosis of AKI. People with AKI had longer unadjusted mean hospital stay, 6.1 versus 3.5 days, higher mean hospital charges, US$71,385 versus US$42,067, and higher rates of all in-hospital postoperative complications, including mortality. Adjusted for age, sex, race, underlying diagnosis, medical comorbidity, income, and insurance payer, AKI was associated with a significantly higher OR (95% CI) of total hospital charges above the median, 2.76 (2.68, 2.85); length of hospital stay > 3 days, 2.21 (2.14, 2.28); and discharge to a rehabilitation facility, 4.68 (4.54, 4.83). AKI was associated with significantly higher OR (95% CI) of in-hospital complications, including infection, 2.60 (1.97, 3.43); transfusion, 2.94 (2.85, 3.03); revision, 2.13 (1.72, 2.64); and mortality, 19.75 (17.39, 22.42). Sensitivity analyses replicated the main study findings, without any attenuation of ORs.

Conclusions:

AKI is associated with a significantly higher risk of increased healthcare utilization, complications, and mortality after primary TKA. Future studies should assess significant factors associated and interventions that can prevent AKI.

SLPI - a Biomarker of Acute Kidney Injury after Open and Endovascular Thoracoabdominal Aortic Aneurysm (TAAA) Repair

Acute kidney injury (AKI) is a relevant complication following thoracoabdominal aortic aneurysm repair (TAAA). Biomarkers, such as secretory leucocyte peptidase inhibitor (SLPI), may enable a more accurate diagnosis. In this study, we tested if SLPI measured in serum is an appropriate biomarker of AKI after TAAA repair. In a prospective observational single-center study including 33 patients (51.5% women, mean age 63.0 ± 16.2 years) undergoing open and endovascular aortic aneurysm repair in 2017, SLPI was measured peri-operatively (until 72 h after surgery). After surgery, the postoperative complications AKI, as defined according to the KDIGO diagnostic criteria, sepsis, death, MACE (major cardiovascular events) and, pneumonia were assessed. In a subgroup analysis, patients with preexisting kidney disease were excluded. Of 33 patients, 51.5% (n = 17) of patients developed AKI. Twelve hours after admission to the intensive care unit (ICU), SLPI serum levels were significantly increased in patients who developed AKI. Multivariable logistic regression revealed a significant association between SLPI 12 hours after admission to ICU and AKI (P = 0.0181, OR = 1.055, 95% CI = 1.009-1.103). The sensitivity of SLPI for AKI prediction was 76.47% (95% CI = 50.1-93.2) and the specificity was 87.5% (95% CI = 61.7-98.4) with an AUC = 0.838 (95% CI = 0.7-0.976) for an optimal cut-off 70.03 ng/ml 12 hours after surgery. In patients without pre-existing impaired renal function, an improved diagnostic quality of SLPI for AKI was observed (Sensitivities of 45.45-91.67%, Specificities of 77.7-100%, AUC = 0.716-0.932). There was no association between perioperative SLPI and the incidence of sepsis, death, MACE (major cardiovascular events), pneumonia. This study suggests that SLPI might be a post-operative biomarker of AKI after TAAA repair, with a superior diagnostic accuracy for patients without preexisting impaired renal function.

Perioperative care of geriatric patients

The older population is expected to nearly double across the globe by 2050, and the baby boom cohort is expected to represent at least 20% of the US population by 2030. Geriatric patients will increasingly utilize the health-care system, and therefore surgical and perioperative care must be tailored to this sensitive group given the increased risk for perioperative complications. The literature was reviewed to highlight fundamental components of the preoperative evaluation as well as cardiac, pulmonary, and renal complications. Frailty is a multidimensional process that can lead to the physiologic effects of aging and estimates the risk of perioperative morbidity and mortality better than chronologic age alone. Health-care providers should assess a geriatric patient's cognitive status, decision-making capacity, frailty, advance care planning, medications, and anesthetic approach in a multidisciplinary fashion to ensure optimal care. The risks of postoperative cardiac, pulmonary, and renal complications should be evaluated and optimized preoperatively to reduce the potential for adverse outcomes.

Diffusion-weighted Renal MRI at 9.4 Tesla Using RARE to Improve Anatomical Integrity

Diffusion-weighted magnetic resonance imaging (DWI) is a non-invasive imaging technique sensitive to tissue water movement. By enabling a discrimination between tissue properties without the need of contrast agent administration, DWI is invaluable for probing tissue microstructure in kidney diseases. DWI studies commonly make use of single-shot Echo-Planar Imaging (ss-EPI) techniques that are prone to suffering from geometric distortion. The goal of the present study was to develop a robust DWI technique tailored for preclinical magnetic resonance imaging (MRI) studies that is free of distortion and sensitive to detect microstructural changes. Since fast spin-echo imaging techniques are less susceptible to B₀ inhomogeneity related image distortions, we introduced a diffusion sensitization to a split-echo Rapid Acquisition with Relaxation Enhancement (RARE) technique for high field preclinical DWI at 9.4 T. Validation studies in standard liquids provided diffusion coefficients consistent with reported values from the literature. Split-echo RARE outperformed conventional ss-EPI, with ss-EPI showing a 3.5-times larger border displacement (2.60 vs. 0.75) and a 60% higher intra-subject variability (cortex = 74%, outer medulla = 62% and inner medulla = 44%). The anatomical integrity provided by the split-echo RARE DWI technique is an essential component of parametric imaging on the way towards robust renal tissue characterization, especially during kidney disease.

Cardiovascular death and progression to end-stage renal disease after major surgery in elderly patients

BACKGROUND

Reliable estimates for risk of cardiovascular-specific mortality and progression to end-stage renal disease (ESRD) among elderly patients undergoing major surgery are not available. This study aimed to develop simple risk scores to predict these events.

METHODS

In a single-centre cohort of elderly patients undergoing major surgery requiring hospital stay longer than 24 h, progression to ESRD and long-term cardiovascular-specific mortality were modelled using multivariable subdistribution hazard models, adjusting for co-morbidity, frailty and type of surgery.

RESULTS

Before surgery, 2·9 and 11·9 per cent of 16 655 patients had ESRD and chronic kidney disease (CKD) respectively. During the hospital stay, 46·9 per cent of patients developed acute kidney injury (AKI). Patients with kidney disease had a significantly higher risk of cardiovascular-specific (CV) mortality compared with patients without kidney disease (adjusted hazard ratio (HR) for CKD without AKI 1·60, 95 per cent c.i. 1·25 to 2·01; AKI without CKD 1·70, 1·52 to 1·87; AKI with CKD 2·80, 2·50 to 3·20; ESRD 5·21, 4·32 to 6·27), as well as increased progression to ESRD (AKI without CKD 5·40, 3·44 to 8·35; CKD without AKI 8·80, 4·60 to 17·00; AKI with CKD 31·60, 19·90 to 49·90). CV Death and ESRD Risk scores were developed to predict CV mortality and progression to ESRD. Calculated CV Death and ESRD Risk scores performed well with c-statistics: 0·77 (95 per cent c.i. 0·76 to 0·78) and 0·82 (0·78 to 0·86) respectively at 1 year.

CONCLUSION

Kidney disease in elderly patients undergoing major surgery is associated with a high risk of CV mortality and progression to ESRD. Risk scores can augment the shared decision-making process of informed consent and identify patients requiring postoperative renal-protective strategies.

Melatonin preconditioning is an effective strategy for mesenchymal stem cell-based therapy for kidney disease

Based on multiple studies in animal models, mesenchymal stem cell (MSC)‐based therapy appears to be an innovative intervention approach with tremendous potential for the management of kidney disease. However, the clinical therapeutic effects of MSCs in either acute kidney injury (AKI) or chronic kidney disease (CKD) are still under debate. Hurdles originate from the harsh microenvironment in vivo that decreases the cell survival rate, paracrine activity and migratory capacity of MSCs after transplantation, which are believed to be the main reasons for their limited effects in clinical applications. Melatonin is traditionally regarded as a circadian rhythm‐regulated neurohormone but in recent years has been found to exhibit antioxidant and anti‐inflammatory properties. Because inflammation, oxidative stress, thermal injury, and hypoxia are abnormally activated in kidney disease, application of melatonin preconditioning to optimize the MSC response to the hostile in vivo microenvironment before transplantation is of great importance. In this review, we discuss current knowledge concerning the beneficial effects of melatonin preconditioning in MSC‐based therapy for kidney disease. By summarizing the available information and discussing the underlying mechanisms, we aim to improve the therapeutic effects of MSC‐based therapy for kidney disease and accelerate translation to clinical application.

Comparison of risk factors for postoperative complications across age groups in patients undergoing ORIF of the ankle

INTRODUCTION

Risk factors associated with various adverse outcomes for patients undergoing open reduction and internal fixation (ORIF) of the ankle, and how these risks differ between younger and older patient populations, has not been clearly established. Objective quantitative data may aid physicians in surgical decision making, individualizing postoperative management, and targeting interventions for reducing postoperative comorbidity. The purpose of this study is to compare the incidence of and risk factors for adverse postoperative outcomes following ORIF of ankle fractures across patient age groups.

MATERIALS AND METHODS

Charts of patients age 18 years and older who underwent open reduction and internal fixation (ORIF) for any closed, non-polytraumatic, non-pilon ankle fracture at a single institution between the years 2008 and 2018 were reviewed. Demographic information, comorbidities, and postoperative outcomes were collected. Relative risks for adverse outcomes were calculated and compared between patients younger than 50 and patients 50 years and older.

RESULTS

A total of 886 patients were included, 375 (42.3%) of which were over age 50. In both age groups, risk of infection was significantly increased among patients with hypertension, although risk among older patients (RR = 3.52, p = 0.004) was greater than that among younger patients (RR = 2.46, p = 0.017). In patients younger than 50, significant risk of wound dehiscence was associated with tobacco use (RR = 3.39, p = 0.022), substance use (RR = 3.07, p = 0.020), and CHF (RR = 12.77, p < 0.001). Risk of implant failure was significantly increased among younger patients with HIV (RR = 4.33, p = 0.026), CHF (RR = 10.54, p < 0.001), and CKD (RR = 10.54, p < 0.001), and among older patients with HTN (RR = 4.51, p = 0.006), CHF (RR = 5.83, p < 0.001), and tobacco use (RR = 3.82, P = 0.001).

CONCLUSION

Patients undergoing ORIF of the ankle should be well-informed of the potential risks of surgery as they pertain to specific comorbidities. Multidisciplinary approaches are warranted for appropriate management of patients with multiple comorbidities.

Opioids Preconditioning Upon Renal Function and Ischemia-Reperfusion Injury: A Narrative Review

Kidneys have an important role in regulating water volume, blood pressure, secretion of hormones and acid-base and electrolyte balance. Kidney dysfunction derived from acute injury can, under certain conditions, progress to chronic kidney disease. In the late stages of kidney disease, treatment is limited to replacement therapy: Dialysis and transplantation. After renal transplant, grafts suffer from activation of immune cells and generation of oxidant molecules. Anesthetic preconditioning has emerged as a promising strategy to ameliorate ischemia reperfusion injury. This review compiles some significant aspects of renal physiology and discusses current understanding of the effects of anesthetic preconditioning upon renal function and ischemia reperfusion injury, focusing on opioids and its properties ameliorating renal injury. According to the available evidence, opioid preconditioning appears to reduce inflammation and reactive oxygen species generation after ischemia reperfusion. Therefore, opioid preconditioning represents a promising strategy to reduce renal ischemia reperfusion injury and, its application on current clinical practice could be beneficial in events such as acute renal injury and kidney transplantation.

Association between the recurrence period of acute kidney injury and mortality: a single-centre retrospective observational study in Japan

OBJECTIVES

Recurrent acute kidney injury (AKI) is a recognised risk factor for mortality. However, it is unclear whether the period until AKI recurrence may have a major factor on patient outcome or not. To explore this issue, we (1) framed the hypothesis that early recurrence increases the risk of mortality and (2) evaluated the prognosis of recurrent AKI cases by setting 21 days as the cut-off period.

METHODS

All studied cases were admitted and followed up at the Kanazawa University Hospital (Kanazawa, Japan) between 1 November 2006 and 31 October 2007. In total, 21 939 patients were retrospectively evaluated in their recurrences of AKI for 2 years and followed up until 31 October 2016. Risks for death were evaluated by the recurrences of AKI (Analysis 1). Patients who developed AKI recurrence before 21 days were defined as the early-recurrence group and the remaining cases as the late-recurrence group. Risks for death were evaluated by the two groups (Analysis 2).

RESULTS

510 patients (2.3%) developed the first AKI. Of these, 151 developed recurrent AKI within 2 years. The number of early-recurrence cases was 44 and that of non-recurrence or late-recurrence was 357. A total of 196 cases (38.4%) died, and higher risk for death was observed in the recurrent AKI group (Analysis 1; p=0.015, log-rank test). We found that the rate of all-cause mortality was higher in the early-recurrence group involving 33.8 deaths per 100 person-years, whereas the non-recurrence or late-recurrence group included only 6.2 deaths per 100 person-years (Analysis 2; p<0.001, log-rank test).

CONCLUSIONS

Patients experiencing recurrent AKI before 21 days from the first AKI clearly showed a relatively poor prognosis. Evidently, careful follow-up for at least 21 days after AKI would be highly useful to detect a recurrence event, possibly leading to a better prognosis after AKI.

Evaluation of urinary γ-glutamyl transferase and serum creatinine in non-azotaemic hospitalised dogs

Urinary and blood biomarkers for diagnosis of acute kidney injury (AKI) in hospitalised dogs were evalueted. This prospective study included 97 dogs, classified according to the International Renal Interest Society classification into no AKI and AKI grade 1 (48-hour increase in serum creatinine≥0.3 mg/dl and/or urinary production <1 ml/kg/hour for at least six hours). A total of 62 of 97 dogs (64 per cent) were classified as AKI 1. A statistically significant difference was found between no AKI and AKI 1 in urine protein to creatinine ratio, urinary γ-glutamyl transferase (uGGT) and uGGT/cu (P<0.0001). Thirteen of 97 dogs (13.4 per cent) that developed increased creatinine and change in AKI grade showed high mortality (n=9/13; 69.2 per cent). The receiver operating characteristic (ROC) curve analysis of uGGT/cu index as a marker for AKI grade 1 had an area under the ROC curve of 0.78; optimal cut-off point was 57.50 u/g, with sensitivity and specificity of 75.4 per cent and 75.6 per cent, respectively. Overall intensive care unit mortality was 23.7 per cent (23/97), 13.4 per cent (13/97) of which died during hospitalisation and 10.3 per cent (10/97) within 28 days after discharge. uGGT is an acceptable marker for distinguishing between AKI 1 and no AKI.

Mesenchymal stem cell therapy targeting mitochondrial dysfunction in acute kidney injury

Mitochondria take part in a network of cellular processes that regulate cell homeostasis. Defects in mitochondrial function are key pathophysiological changes during acute kidney injury (AKI). Mesenchymal stem cells (MSCs) have shown promising regenerative effects in experimental AKI models, but the specific mechanism is still unclear. Some studies have demonstrated that MSCs are able to target mitochondrial dysfunction during AKI. In this review, we summarize these articles, providing an integral and updated view of MSC therapy targeting mitochondrial dysfunction during AKI, which is aimed at promoting the therapeutic effect of MSCs in AKI patients.