Trends in acute kidney injury, associated use of dialysis, and mortality after cardiac surgery, 1999 to 2008

Predictors of renal replacement therapy following isolated coronary artery surgery: a retrospective case-controlled study

OBJECTIVES

Severe acute kidney injury (AKI) requiring postoperative renal replacement therapy (RRT) is associated with increased morbidity and mortality rates following cardiac surgery. Our study aimed to analyze patients requiring postoperative RRT in a population undergoing isolated coronary artery surgery.

METHODS

Following exclusions, we analyzed 124 944 consecutive patients in the Polish National Registry of Cardiac Surgical Procedures (KROK Registry), scheduled for isolated coronary artery surgery between January 2010 and December 2019. Patients who underwent preoperative chronic dialysis were excluded from the study. Data of patients requiring postoperative RRT and patients without postoperative RRT were compared.

RESULTS

In the analyzed population, 1668 patients (1.3%) developed AKI requiring RRT. In-hospital mortality among patients with and without postoperative RRT was 40.1 and 1.6%, respectively ( P <0.001). Patients requiring postoperative RRT had significantly more preoperative co-morbidities and more frequent postoperative complications. Preoperative chronic renal failure and cardiogenic shock were the two most prominent independent risk factors for postoperative RRT in these patients (OR: 5.0, 95% CI: 3.9-6.4, P <0.001 and OR: 3.9, 95% CI: 2.8-5.6, P <0.001, respectively).

CONCLUSION

Severe AKI requiring postoperative RRT dramatically increases in-hospital mortality and is associated with the development of serious postoperative complications. The need for postoperative RRT is clearly associated with the presence of preoperative co-morbidities. Preoperative chronic renal failure and cardiogenic shock were particularly related to the development of this complication.

Acute Kidney Injury Receiving Dialysis and Dialysis Care after Hospital Discharge

The number of patients with AKI receiving outpatient hemodialysis (AKI-D) is increasing. At present, on the basis of limited data, approximately one third of patients with AKI-D who receive outpatient dialysis after hospital discharge survive and regain sufficient kidney function to discontinue dialysis. Data to inform dialysis management strategies that promote kidney function recovery and processes of care among patients with AKI-D receiving outpatient dialysis are lacking. In this article, we detail current trends in the incidence, risk factors, clinical outcomes, proposed management, and health policy landscape for patients with AKI-D receiving outpatient dialysis and identify areas for further research.

The epidemiology and outcomes of acute kidney injury following orthopaedic procedures: A retrospective cohort study

BACKGROUND

Acute kidney injury (AKI) is a serious complication following major surgery. This study examined the incidence and risk factors of AKI following orthopaedic surgeries in an Icelandic cohort, as well as the association between AKI and patient- and surgery-related factors.

METHODS

This retrospective cohort study comprised all patients 18 years and older who underwent orthopaedic surgeries at Landspitali - The National University Hospital in the years 2006-2018 with available serum creatinine (SCr) measurements adjacent to the surgery to stage AKI. AKI was defined according to SCr portion of the KDIGO criteria. Logistic regression was used to identify patient- and surgical factors related to progression of AKI and Poisson-regression was used to explore changes in incidence.

RESULTS

A total of 222 cases of AKI following 3208 surgeries (6.9%) were identified in the study period with a rise in the incidence by about 17% per year. Higher age (odds ratio (OR), 1.02, 95% confidence interval (CI), 1.01-1.04 per year) and underlying reduction in kidney function (OR 1.93 (1.30-2.81), 3.24 (2.08-4.96) and 4.08 (2.35-6.96) for estimated glomerular filtration rate (eGFR) of 30-59, 15-29 and <15 mL/min/1.73 m2 compared with eGFR >60 mL/min/1.73 m2 ) were associated with higher risk of AKI, but female sex was associated with decreased odds (OR = 0.73; 95% CI, 0.54-0.98). After correcting for age, sex, preoperative kidney function, emergency surgery and underlying comorbidities and frailty, there was an increased risk of long-term mortality in patients with AKI (HR 1.41, 95% CI 1.08-1.85), and patients who developed AKI also had accelerated progression of chronic kidney disease compared with patients who did not develop AKI.

CONCLUSIONS

The incidence of AKI following orthopaedic surgeries is increasing and is associated with adverse outcomes. It is important that elderly individuals and patients who have reduced kidney function receive adequate monitoring and surveillance in the perioperative period.

Study protocol of a phase 2, randomised, placebo-controlled, double-blind, adaptive, parallel group clinical study to evaluate the efficacy and safety of recombinant alpha-1-microglobulin in subjects at high risk for acute kidney injury following open-chest cardiac surgery (AKITA trial)

INTRODUCTION

Acute kidney injury (AKI) is a common complication after cardiac surgery (CS) and is associated with adverse short-term and long-term outcomes. Alpha-1-microglobulin (A1M) is a circulating glycoprotein with antioxidant, heme binding and mitochondrial-protective mechanisms. RMC-035 is a modified, more soluble, variant of A1M and has been proposed as a novel targeted therapeutic protein to prevent CS-associated AKI (CS-AKI). RMC-035 was considered safe and generally well tolerated when evaluated in four clinical phase 1 studies.

METHODS AND ANALYSIS

This is a phase 2, randomised, double-blind, adaptive design, parallel group clinical study that evaluates RMC-035 compared with placebo in approximately 268 cardiac surgical patients at high risk for CS-AKI. RMC-035 is administered as an intravenous infusion. In total, five doses will be given. Dosing is based on presurgery estimated glomerular filtration rate (eGFR), and will be either 1.3 or 0.65 mg/kg.The primary study objective is to evaluate whether RMC-035 reduces the incidence of postoperative AKI, and key secondary objectives are to evaluate whether RMC-035 improves postoperative renal function compared with placebo. A blinded interim analysis with potential sample size reassessment is planned once 134 randomised subjects have completed dosing. An independent data monitoring committee will evaluate safety and efficacy data at prespecified intervals throughout the trial. The study is a global multicentre study at approximately 30 sites.

ETHICS AND DISSEMINATION

The trial was approved by the joint ethics committee of the physician chamber Westfalen-Lippe and the University of Münster (code '2021-778 f-A') and subsequently approved by the responsible ethics committees/relevant institutional review boards for the participating sites. The study is conducted in accordance with Good Clinical Practice, the Declaration of Helsinki and other applicable regulations. Results of this study will be published in a peer-reviewed scientific journal.

TRIAL REGISTRATION NUMBER

NCT05126303.

Perioperative parameters-based prediction model for acute kidney injury in Chinese population following valvular surgery

Background

Acute kidney injury (AKI) is a relevant complication after cardiac surgery and is associated with significant morbidity and mortality. Existing risk prediction tools have certain limitations and perform poorly in the Chinese population. We aimed to develop prediction models for AKI after valvular cardiac surgery in the Chinese population.

Methods

Models were developed from a retrospective cohort of patients undergoing valve surgery from December 2013 to November 2018. Three models were developed to predict all-stage, or moderate to severe AKI, as diagnosed according to Kidney Disease: Improving Global Outcomes (KDIGO) based on patient characteristics and perioperative variables. Models were developed based on lasso logistics regression (LLR), random forest (RF), and extreme gradient boosting (XGboost). The accuracy was compared among three models and against the previously published reference AKICS score.

Results

A total of 3,392 patients (mean [SD] age, 50.1 [11.3] years; 1787 [52.7%] male) were identified during the study period. The development of AKI was recorded in 50.5% of patients undergoing valve surgery. In the internal validation testing set, the LLR model marginally improved discrimination (C statistic, 0.7; 95% CI, 0.66-0.73) compared with two machine learning models, RF (C statistic, 0.69; 95% CI, 0.65-0.72) and XGBoost (C statistic, 0.66; 95% CI, 0.63-0.70). A better calibration was also found in the LLR, with a greater net benefit, especially for the higher probabilities as indicated in the decision curve analysis. All three newly developed models outperformed the reference AKICS score.

Conclusion

Among the Chinese population undergoing CPB-assisted valvular cardiac surgery, prediction models based on perioperative variables were developed. The LLR model demonstrated the best predictive performance was selected for predicting all-stage AKI after surgery.

Clinical trial registration

Trial registration: Clinicaltrials.gov, NCT04237636.

Characteristics of and Outcomes After Dialysis-Treated Acute Kidney Injury, 2009-2018: A Taiwanese Multicenter Study

RATIONALE & OBJECTIVE

Dialysis-treated acute kidney injury (AKI) is increasingly common in intensive care units (ICUs) and is associated with poor outcomes. Few studies have explored the temporal trends in severity of acute illness at dialysis initiation, indications for dialysis, and their association with patient outcomes.

STUDY DESIGN

Multicenter retrospective cohort study.

SETTING & PARTICIPANTS

9,535 adult patients admitted to the ICU who received their first dialysis treatment from Chang Gung Memorial Hospital system in Taiwan from 2009 through 2018.

EXPOSURE

Calendar year.

OUTCOMES

ICU mortality and dialysis treatment at discharge among hospital survivors.

ANALYTICAL APPROACH

The temporal trends during the study period were investigated using test statistics suited for continuous or categorical data. The association between the study year and the risk of mortality was analyzed using multivariable Cox regression with adjustment for relevant clinical variables, including the severity of acute illness, defined by Sequential Organ Failure Assessment (SOFA) score.

RESULTS

The mean SOFA score at dialysis initiation decreased slightly from 14.0 in 2009 to 13.6 in 2018. There was no significant trend in the number of indications for dialysis initiation that were fulfilled over time. Observed ICU mortality decreased over time, and the curve appeared to be reverse J-shaped, with a substantial decrease from 56.1% in 2009 to 46.3% in 2015 and a slight increase afterward. The risk of mortality was significantly reduced from 2013 to 2018 compared with 2009 in adjusted models. The decreasing trend in ICU mortality over time remained significant. There was an increase in dialysis treatment at discharge among survivors, mainly in patients with estimated glomerular filtration rate<60mL/min/1.73m², from 36.8% in 2009 to 43.9% in 2018.

LIMITATIONS

Residual confounding from unmeasured factors over time such as severity of comorbidities, detailed medication interventions, and delivered dialysis dose.

CONCLUSIONS

We observed reductions in mortality among ICU patients with dialysis-treated acute kidney injury between 2009 and 2018, even after adjusting for dialysis indication and severity of illness at dialysis initiation. However, dialysis treatment at discharge among survivors has increased over time, mainly in patients with preexisting kidney disease.

Large-scale evidence generation and evaluation across a network of databases for type 2 diabetes mellitus (LEGEND-T2DM): a protocol for a series of multinational, real-world comparative cardiovascular effectiveness and safety studies

INTRODUCTION

Therapeutic options for type 2 diabetes mellitus (T2DM) have expanded over the last decade with the emergence of cardioprotective novel agents, but without such data for older drugs, leaving a critical gap in our understanding of the relative effects of T2DM agents on cardiovascular risk.

METHODS AND ANALYSIS

The large-scale evidence generations across a network of databases for T2DM (LEGEND-T2DM) initiative is a series of systematic, large-scale, multinational, real-world comparative cardiovascular effectiveness and safety studies of all four major second-line anti-hyperglycaemic agents, including sodium-glucose co-transporter-2 inhibitor, glucagon-like peptide-1 receptor agonist, dipeptidyl peptidase-4 inhibitor and sulfonylureas. LEGEND-T2DM will leverage the Observational Health Data Sciences and Informatics (OHDSI) community that provides access to a global network of administrative claims and electronic health record data sources, representing 190 million patients in the USA and about 50 million internationally. LEGEND-T2DM will identify all adult, patients with T2DM who newly initiate a traditionally second-line T2DM agent. Using an active comparator, new-user cohort design, LEGEND-T2DM will execute all pairwise class-versus-class and drug-versus-drug comparisons in each data source, producing extensive study diagnostics that assess reliability and generalisability through cohort balance and equipoise to examine the relative risk of cardiovascular and safety outcomes. The primary cardiovascular outcomes include a composite of major adverse cardiovascular events and a series of safety outcomes. The study will pursue data-driven, large-scale propensity adjustment for measured confounding, a large set of negative control outcome experiments to address unmeasured and systematic bias.

ETHICS AND DISSEMINATION

The study ensures data safety through a federated analytic approach and follows research best practices, including prespecification and full disclosure of results. LEGEND-T2DM is dedicated to open science and transparency and will publicly share all analytic code from reproducible cohort definitions through turn-key software, enabling other research groups to leverage our methods, data and results to verify and extend our findings.

Machine learning for the prediction of acute kidney injury in critical care patients with acute cerebrovascular disease

Purpose

Acute kidney injury (AKI) is a common complication and associated with a poor clinical outcome. In this study, we developed and validated a model for predicting the risk of AKI through machine learning methods in critical care patients with acute cerebrovascular disease.

Methods

This study was a retrospective study based on two different cohorts. Five machine learning methods were used to develop AKI risk prediction models. We used six popular metrics (AUROC, F2-Score, accuracy, sensitivity, specificity and precision) to evaluate the performance of these models.

Results

We identified 2935 patients in the MIMIC-III database and 499 patients in our local database to develop and validate the AKI risk prediction model. The incidence of AKI in these two different cohorts was 18.3% and 61.7%, respectively. Analysis showed that several laboratory parameters (serum creatinine, hemoglobin, white blood cell count, bicarbonate, blood urea nitrogen, sodium, albumin, and platelet count), age, and length of hospital stay, were the top ten important factors associated with AKI. The analysis demonstrated that the XGBoost had higher AUROC (0.880, 95%CI: 0.831–0.929), indicating that the XGBoost model was better at predicting AKI risk in patients with acute cerebrovascular disease than other models.

Conclusions

This study developed machine learning methods to identify critically ill patients with acute cerebrovascular disease who are at a high risk of developing AKI. This result suggested that machine learning techniques had the potential to improve the prediction of AKI risk models in critical care.

Renal and Cerebral Hypoxia and Inflammation During Cardiopulmonary Bypass

Cardiac surgery-associated acute kidney injury and brain injury remain common despite ongoing efforts to improve both the equipment and procedures deployed during cardiopulmonary bypass (CPB). The pathophysiology of injury of the kidney and brain during CPB is not completely understood. Nevertheless, renal (particularly in the medulla) and cerebral hypoxia and inflammation likely play critical roles. Multiple practical factors, including depth and mode of anesthesia, hemodilution, pump flow, and arterial pressure can influence oxygenation of the brain and kidney during CPB. Critically, these factors may have differential effects on these two vital organs. Systemic inflammatory pathways are activated during CPB through activation of the complement system, coagulation pathways, leukocytes, and the release of inflammatory cytokines. Local inflammation in the brain and kidney may be aggravated by ischemia (and thus hypoxia) and reperfusion (and thus oxidative stress) and activation of resident and infiltrating inflammatory cells. Various strategies, including manipulating perfusion conditions and administration of pharmacotherapies, could potentially be deployed to avoid or attenuate hypoxia and inflammation during CPB. Regarding manipulating perfusion conditions, based on experimental and clinical data, increasing standard pump flow and arterial pressure during CPB appears to offer the best hope to avoid hypoxia and injury, at least in the kidney. Pharmacological approaches, including use of anti-inflammatory agents such as dexmedetomidine and erythropoietin, have shown promise in preclinical models but have not been adequately tested in human trials. However, evidence for beneficial effects of corticosteroids on renal and neurological outcomes is lacking. © 2021 American Physiological Society. Compr Physiol 11:1-36, 2021.

Incidence- and In-hospital Mortality-Related Risk Factors of Acute Kidney Injury Requiring Continuous Renal Replacement Therapy in Patients Undergoing Surgery for Acute Type a Aortic Dissection

Background: Few studies on the risk factors for postoperative continuous renal replacement therapy (CRRT) in a homogeneous population of patients with acute type A aortic dissection (AAAD). This retrospective analysis aimed to investigate the risk factors for CRRT and in-hospital mortality in the patients undergoing AAAD surgery and to discuss the perioperative comorbidities and short-term outcomes. Methods: The study collected electronic medical records and laboratory data from 432 patients undergoing surgery for AAAD between March 2009 and June 2021. All the patients were divided into CRRT and non-CRRT groups; those in the CRRT group were divided into the survivor and non-survivor groups. The univariable and multivariable analyses were used to identify the independent risk factors for CRRT and in-hospital mortality. Results: The proportion of requiring CRRT and in-hospital mortality in the patients with CRRT was 14.6 and 46.0%, respectively. Baseline serum creatinine (SCr) [odds ratio (OR), 1.006], cystatin C (OR, 1.438), lung infection (OR, 2.292), second thoracotomy (OR, 5.185), diabetes mellitus (OR, 6.868), AKI stage 2-3 (OR, 22.901) were the independent risk factors for receiving CRRT. In-hospital mortality in the CRRT group (46%) was 4.6 times higher than in the non-CRRT group (10%). In the non-survivor (n = 29) and survivor (n = 34) groups, New York Heart Association (NYHA) class III-IV (OR, 10.272, P = 0.019), lactic acidosis (OR, 10.224, P = 0.019) were the independent risk factors for in-hospital mortality in patients receiving CRRT. Conclusion: There was a high rate of CRRT requirement and high in-hospital mortality after AAAD surgery. The risk factors for CRRT and in-hospital mortality in the patients undergoing AAAD surgery were determined to help identify the high-risk patients and make appropriate clinical decisions. Further randomized controlled studies are urgently needed to establish the risk factors for CRRT and in-hospital mortality.

Intra-operative and early post-operative prediction of cardiac surgery-associated acute kidney injury: Urinary oxygen tension compared with plasma and urinary biomarkers

Acute kidney injury (AKI) is a common and serious post-operative complication of cardiac surgery. The value of a predictive biomarker is determined not only by its predictive efficacy, but also by how early this prediction can be made. For a biomarker of cardiac surgery-associated AKI, this is ideally during the intra-operative period. Therefore, in 82 adult patients undergoing cardiac surgery requiring cardiopulmonary bypass (CPB), we prospectively compared the predictive efficacy of various blood and urinary biomarkers with that of continuous measurement of urinary oxygen tension (UPO₂ ) at pre-determined intra- and post-operative time-points. None of the blood or urine biomarkers we studied showed predictive efficacy for post-operative AKI when measured intra-operatively. When treated as a binary variable (≤ or > median for the whole cohort), the earliest excess risk of AKI was predicted by an increase in urinary neutrophil gelatinase-associated lipocalin (NGAL) at 3 h after entry into the intensive care unit (odds ratio [95% confidence limits], 2.86 [1.14-7.21], p = 0.03). Corresponding time-points were 6 h for serum creatinine (3.59 [1.40-9.20], p = 0.008), and 24 h for plasma NGAL (4.54 [1.73-11.90], p = 0.002) and serum cystatin C (6.38 [2.35-17.27], p = 0.001). In contrast, indices of intra-operative urinary hypoxia predicted AKI after weaning from CPB, and in the case of a fall in UPO₂ to ≤10 mmHg, during the rewarming phase of CPB (3.00 [1.19-7.56], p = 0.02). We conclude that continuous measurement of UPO₂ predicts AKI earlier than plasma or urinary NGAL, serum cystatin C, or early post-operative changes in serum creatinine.

Incidence and Outcomes of Laryngeal Complications Following Adult Cardiac Surgery: A National Analysis

Laryngeal complications (LCs) following cardiac operations contribute to increased morbidity and resource utilization. Using a nationally representative cohort of cardiac surgical patients, we characterized the incidence of LC as well as its associated clinical and financial outcomes. All adults undergoing coronary artery bypass grafting and/or valvular operations were identified using the 2010–2017 Nationwide Readmissions Database. International Classification of Diseases 9th and 10th Revision diagnosis codes were used to identify LC. Trends were analyzed using a rank-based, non-parametric test (nptrend). Multivariable linear and logistic regressions were used to evaluate risk factors for LC, and its impact on mortality, complications, resource use and 30-day non-elective readmissions. Of an estimated 2,319,628 patients, 1.7% were diagnosed with perioperative LC, with rising incidence from 1.5% in 2010 to 1.8% in 2017 (nptrend < 0.001). After adjustment, female sex [adjusted odds ratio 1.08, 95% confidence interval (CI) 1.04–1.12], advancing age, and multi-valve procedures (1.51, 95% CI 1.36–1.67, reference: isolated CABG) were associated with increased odds of LC. Despite no risk-adjusted effect on mortality, LC was associated with increased odds of pneumonia (2.88, 95% CI 2.72–3.04), tracheostomy (4.84, 95% CI 4.44–5.26), and readmission (1.32, 95% CI 1.26–1.39). In addition, LC was associated with a 7.7-day increment (95% CI 7.4–8.0) in hospitalization duration and $24,200 (95% CI 23,000–25,400) in attributable costs. The present study found LC to be associated with increased perioperative sequelae and resource utilization. The development and application of active screening protocols for post-surgical LC are warranted to increase early detection and reduce associated morbidity.

Critical oxygen delivery threshold during cardiopulmonary bypass in older cardiac surgery patients with increased frailty risk

OBJECTIVES

Older patients have a higher cardiac surgery-associated acute kidney injury (CSA-AKI) related mortality. Low oxygen delivery (DO2) during cardiopulmonary bypass (CPB) is a risk factor for CSA-AKI, but critical DO2 thresholds for older patients are unknown. This study investigated critical DO2 thresholds for CSA-AKI in patients ≥70 years undergoing on-pump cardiac surgery.

METHODS

Patients were enrolled from July 2015 until August 2017. CPB data from 432 patients were collected, and DO2 values were calculated per minute. The primary outcome was CSA-AKI. The association between DO2 and CSA-AKI was analysed with multivariable regression analysis. Multiple DO2 thresholds were analysed. The association between CSA-AKI and the area below the DO2 thresholds (DO2 deficit) was evaluated, as was the association between frailty and CSA-AKI.

RESULTS

CSA-AKI occurred in 63 (14.6%) patients. Mean and nadir (lowest) DO2 values were lower in patients with CSA-AKI (283 vs 312 ml/min/m2; P-value <0.001 and 238 vs 270 ml/min/m2; P-value <0.001, respectively). The adjusted relative risk for CSA-AKI was 1.006 [99% confidence interval (CI) 1.001-1.012] per ml/min/m2 nadir DO2 decrease. The critical DO2 threshold was 270 ml/min/m2 [adjusted relative risk 2.06 (99% CI 1.33-2.80)]. The DO2 deficit below 270 ml/min/m2 was associated with CSA-AKI [adjusted relative risk 2.84 (99% CI 1.87-3.81)]. No association between frailty and CSA-AKI was found (P = 0.82).

CONCLUSIONS

Low DO2 increased the risk for CSA-AKI in older patients who had cardiac surgery. A critical DO2 threshold of 270 ml/min/m2 was applicable for frail and non-frail patients. The efficacy of a DO2 >270 ml/min/m2 to reduce CSA-AKI in older patients needs further evaluation.

Artificial Intelligence in Acute Kidney Injury: From Static to Dynamic Models

Artificial intelligence (AI) is the development of computer systems that normally require human intelligence. In the field of acute kidney injury (AKI) AI has led to an evolution of risk prediction models. In the past, static prediction models were developed using baseline (eg, preoperative) data to evaluate AKI risk. Newer models which incorporated baseline as well as evolving data collected during a hospital admission have shown improved predicative abilities. In this review, we will summarize the advances made in AKI risk prediction over the last several years, including a shift toward more dynamic, real-time, electronic medical record-based models. In addition, we will be discussing the role of electronic AKI alerts and decision support tools. Recent studies have demonstrated improved patient outcomes through the use of these tools which monitor for nephrotoxin medication exposures as well as provide kidney focused care bundles for patients at high risk for severe AKI. Finally, we will briefly discuss the pitfalls and implications of implementing these scores, alerts, and support tools.

Inpatient Mortality Benefit with Transjugular Intrahepatic Portosystemic Shunt for Hospitalized Hepatorenal Syndrome Patients

BACKGROUND

It has been reported that transjugular intrahepatic portosystemic shunting (TIPS) might be utilized as a salvage option for hepatorenal syndrome (HRS), while randomized controlled trials are pending and real-world contemporary data on inpatient mortality is lacking.

METHODS

We conducted an observational retrospective cohort study from the National Inpatient Sample from 2005 to 2014. We included all adult patients admitted with HRS and cirrhosis, using ICD 9-CM codes. We excluded cases with variceal bleeding, Budd-Chiari, end-stage renal disease, liver transplant and transfers to acute-care facilities. TIPS' association with inpatient mortality was assessed using multivariable mixed-effects logistic regression, as well as exact-matching, thus mitigating for TIPS selection bias. The exact-matched analysis was repeated among TIPS-only versus dialysis-only patients.

RESULTS

A total of 79,354 patients were included. Nine hundred eighteen (1.2%) underwent TIPS. Between TIPS and non-TIPS groups, mean age (58 years) and gender (65% males) were similar. Overall mortality was 18% in TIPS and 48% in dialysis-only cases (n = 10,379; 13.1%). Ninety six (10.5%) TIPS patients underwent dialysis. In-hospital mortality in TIPS patients was twice less likely than in non-TIPS patients (adjusted odds ratio [aOR] = 0.43, 95% CI 0.30-0.62; p < 0.001), with similar results in matched analysis [exact-matched (em) OR = 0.39, 95% CI 0.17-0.89; p < 0.024; groups = 96; unweighted n = 463]. Head-to-head comparison showed that TIPS-only patients were 3.3 times less likely to succumb inpatient versus dialysis-only patients (contrast aOR = 0.31, 95% CI 0.20-0.46; p < 0.001), with similar findings post-matching (emOR = 0.22, 95% CI 0.15-0.33; p < 0.001; groups = 54, unweighted n = 1457).

CONCLUSIONS

Contemporary, real-world data reveal that TIPS on its own, and when compared to dialysis, is associated with decreased inpatient mortality when utilized in non-bleeders-HRS patients. Further randomized studies are needed to establish the long-term benefit of TIPS in these patients.

Association of dialysis-requiring acute kidney injury with 90-day prognosis in patients with coronary artery disease and advanced kidney disease after coronary angiography

BACKGROUND

Dialysis-requiring acute kidney injury (AKI-D) is a potentially serious complication associated with high in-hospital mortality among patients with coronary artery disease (CAD) after coronary angiography (CAG). Patients with existing advanced kidney disease (AKD) have an increased risk of developing AKI-D. However, few studies have investigated the prognosis of AKI-D in patients with both CAD and AKD.

METHODS

In this observational study, 603 CAD patients with AKD (estimated glomerular filtration rate, eGFR <30 mL/min/1.73 m2) were enrolled. AKI-D was defined as acute or worsening renal failure requiring the initiation of renal dialysis. The primary endpoint was 90-day all-cause mortality. Kaplan-Meier and Cox regression analyses were used to assess the association of AKI-D and 90-day all-cause mortality among CAD patients complicated with AKD.

RESULTS

Overall, among 603 CAD patients complicated with AKD, 83 patients (13.8%) required AKI-D. Patients underwent AKI-D had a significantly higher rate of 90-day mortality than those who did not (13.3% vs. 6.5%, log rank P=0.028), with an unadjusted hazard ratio (HR) of 1.28 [95% confidence interval (CI): 1.02-1.61, P=0.032]. After adjustment for cardiac and renal impairment, however, AKI-D was no longer associated with 90-day mortality (HR: 1.08, 95% CI: 0.84-1.39, P=0.559). The attenuation analysis showed that after adjustment for cardiac and renal function, the residual effect of 90-day mortality was as low as 30% of the unadjusted effect.

CONCLUSIONS

The incidence of AKI-D is high among patients with CAD complicated by AKD. The high 90-day mortality rate of patients undergoing AKI-D is mainly attributable to cardio-renal impairment.

Carbon monoxide: An emerging therapy for acute kidney injury

Treating acute kidney injury (AKI) represents an important unmet medical need both in terms of the seriousness of this medical problem and the number of patients. There is also a large untapped market opportunity in treating AKI. Over the years, there has been much effort in search of therapeutics with minimal success. However, over the same time period, new understanding of the underlying pathobiology and molecular mechanisms of kidney injury have undoubtedly helped the search for new therapeutics. Along this line, carbon monoxide (CO) has emerged as a promising therapeutic agent because of its demonstrated cytoprotective, and immunomodulatory effects. CO has also been shown to sensitize cancer, but not normal cells, to chemotherapy. This is particularly important in treating cisplatin-induced AKI, a common clinical problem that develops in patients receiving cisplatin therapies for a number of different solid organ malignancies. This review will examine and make the case that CO be developed into a therapeutic agent against AKI.

US Trends in Hospitalizations for Dialysis-Requiring Acute Kidney Injury in People With Versus Without Diabetes

RATIONALE & OBJECTIVE

Dialysis-requiring acute kidney injury (AKI-D) has increased substantially in the United States. We examined trends in and comorbid conditions associated with hospitalizations and in-hospital mortality in the setting of AKI-D among people with versus without diabetes.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

Nationally representative data from the National Inpatient Sample and National Health Interview Survey were used to generate 16 cross-sectional samples of US adults (aged ≥18 years) between 2000 and 2015.

EXPOSURE

Diabetes, defined using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes.

OUTCOME

AKI-D, defined using ICD-9-CM diagnosis and procedure codes.

ANALYTICAL APPROACH

Annual age-standardized rates of AKI-D and AKI-D mortality were calculated for adults with and without diabetes, by age and sex. Data were weighted to be representative of the US noninstitutionalized population. Trends were assessed using join point regression with annual percent change (Δ/y) reported.

RESULTS

In adults with diabetes, AKI-D increased between 2000 and 2015 (from 26.4 to 41.1 per 100,000 persons; Δ/y, 3.3%; P < 0.001), with relative increases greater in younger versus older adults. In adults without diabetes, AKI-D increased between 2000 and 2009 (from 4.8 to 8.7; Δ/y, 6.5%; P < 0.001) and then plateaued. AKI-D mortality significantly declined in people with and without diabetes. In adults with and without diabetes, the proportion of AKI-D hospitalizations with liver, rheumatic, and kidney disease comorbid conditions increased between 2000 and 2015, while the proportion of most cardiovascular comorbid conditions decreased.

LIMITATIONS

Lack of laboratory data to corroborate AKI diagnosis; National Inpatient Sample data are hospital-level rather than person-level data; no data for type of diabetes; residual unmeasured confounding.

CONCLUSIONS

Hospitalization rates for AKI-D have increased considerably while mortality has decreased in adults with and without diabetes. Hospitalization rates for AKI-D remain substantially higher in adults with diabetes. Greater AKI risk-factor mitigation is needed, especially in young adults with diabetes.

Current Status of Novel Biomarkers for the Diagnosis of Acute Kidney Injury: A Historical Perspective

Acute kidney injury (AKI) is a common and serious medical condition associated with significant increases in morbidity, mortality, and cost of care. Because of the high incidence and poor outcomes associated with AKI, there has been significant interest in the development of new therapies for the prevention and treatment of the disease. A lack of efficacy in drug trials led to the concern that AKI was not being diagnosed early enough for an effective intervention and that a rise in serum creatinine itself is not a sensitive-enough marker. Researchers have been searching for novel biomarkers that can not only assess a decline in kidney function but also demonstrate structural damage to the kidney and at time points earlier than increases in serum creatinine measurements allow. Over the past 10 years, there have been 3300 new publications and hundreds of new biomarkers investigated, yet concern still remains regarding AKI biomarker performance. The AKI biomarkers are yet to be widely utilized in clinical practice, leading some to question whether AKI biomarkers will ever reach their initial promise. However, we believe that biomarkers are an important part of current and future AKI research and clinical management. In this review, we compare the historical contexts of acute myocardial ischemia and AKI biomarker development to illustrate the progress that has been made within AKI biomarker research in a relatively short period of time and also to point out key differences between the disease processes that have been barriers to widespread AKI biomarker adoption. Finally, we discuss potential paths by which biomarkers can lead to appropriate AKI treatment responses that lower morbidity and mortality.

A cardiovascular model for renal perfusion during cardiopulmonary bypass surgery

Acute kidney injury (AKI) is a major complication following cardiac surgery requiring cardiopulmonary bypass (CPB). It is likely that poor renal perfusion contributes to the occurrence of AKI, via renal hypoxia, so it is imperative to maintain optimal renal perfusion during CPB. We have developed a straightforward cardiovascular perfusion model with parameter values calibrated against experimental and/or clinical data from several independent studies of CPB in humans and animals. Following model development and calibration, we performed a one-at-a-time parametric study to investigate the response of renal perfusion to several variables during CPB, namely pump flow (denoted CO for 'cardiac output'), renal vascular resistance, and non-renal vascular resistance. From the parametric study, we have found that all three parameters had a similarly strong influence on renal perfusion. We simulated three potential strategies for maintaining optimum renal perfusion during CPB and tested their effectiveness. The strategies were: (1) increasing the pump flow; (2) administrating noradrenaline (vasopressor); and (3) administrating fenoldopam (renal vasodilator). Simulations have revealed that administration of fenoldopam is likely to be the most effective of the three strategies. Other findings from our simulations are that increasing pump flow is less effective when central venous pressure is elevated. Further, renal autoregulation is likely inoperative during CPB, as evidenced by an unchanging renal vascular resistance with increasing CO and blood pressure. The cardiac-renal perfusion model developed in this study can be linked with other kidney models to simulate the changes in renal oxygenation during CPB.

Costs and consequences of acute kidney injury after cardiac surgery: A cohort study

OBJECTIVES

Acute kidney injury (AKI) is common after cardiac surgery. We quantified the mortality and costs of varying degrees of AKI using a population-based cohort in Alberta, Canada.

METHODS

A cohort of patients undergoing cardiac surgery from 2004 to 2009 was assembled from linked Alberta administrative databases. AKI was classified by Kidney Disease Improving Global Outcomes stages of severity. Our outcomes were in-hospital mortality, length of stay, and costs; among survivors, we also examined mortality and costs at 365 days. Estimates were adjusted for demographic characteristics, comorbidities, and other covariates.

RESULTS

Ten thousand one hundred seventy participants were included, of whom 9771 patients were discharged to community. Overall in-hospital mortality, costs, and length of stay were 4%, 7 days, and Can $34,000, respectively. Postcardiac surgery, AKI occurred in 25%. Compared with those without AKI, AKI was independently associated with increased in-hospital mortality across severity categories, with the highest risk (adjusted odds ratio, 37.1; 95% confidence interval, 26.3-52.1; P < .001) in patients who required acute dialysis. AKI severity was associated with increased hospital days and costs, with costs ranging from 1.21 for stage 1 AKI (95% confidence interval, 1.17-1.23) to 2.74 for acute dialysis (95% confidence interval, 2.49-3.00) (P < .001) times higher than in patients without AKI, after covariate adjustment. Postdischarge to 365 days, patients with AKI continued to experience increased costs up to 1.35-fold, and patients who required dialysis acutely continued to experience a 2.86-fold increased mortality.

CONCLUSIONS

AKI remains an important indicator of mortality and health care costs postcardiac surgery.

Carbon monoxide: An emerging therapy for acute kidney injury

Treating acute kidney injury (AKI) represents an important unmet medical need both in terms of the seriousness of this medical problem and the number of patients. There is also a large untapped market opportunity in treating AKI. Over the years, there has been much effort in search of therapeutics with minimal success. However, over the same time period, new understanding of the underlying pathobiology and molecular mechanisms of kidney injury have undoubtedly helped the search for new therapeutics. Along this line, carbon monoxide (CO) has emerged as a promising therapeutic agent because of its demonstrated cytoprotective, and immunomodulatory effects. CO has also been shown to sensitize cancer, but not normal cells, to chemotherapy. This is particularly important in treating cisplatin-induced AKI, a common clinical problem that develops in patients receiving cisplatin therapies for a number of different solid organ malignancies. This review will examine and make the case that CO be developed into a therapeutic agent against AKI.

Schmidt-Ott K. The Incidence of Acute Kidney Injury and Associated Hospital Mortality

BACKGROUND

Studies from multiple countries have shown that acute kidney injury (AKI) in hospitalized patients is associated with mortality and morbidity. There are no reliable data at present on the incidence and mortality of AKI episodes among hospitalized patients in Germany. The utility of administrative codings of AKI for the identification of AKI episodes is also unclear.

METHODS

In an exploratory approach, we retrospectively analyzed all episodes of AKI over a period of 3.5 years (2014-2017) on the basis of routinely obtained serum creatinine measurements in 103 161 patients whose creatinine had been measured at least twice and who had been in the hospital for at least two days. We used the "Kidney Disease: Improving Global Outcomes" (KDIGO) criteria for AKI. In parallel, we assessed the administrative coding of discharge diagnoses of the same patients with codes from the International Classification of Diseases (ICD-10-GM).

RESULTS

Among 185 760 hospitalizations, stage 1 AKI occurred in 25 417 cases (13.7%), stage 2 in 8503 cases (4.6%), and stage 3 in 5881 cases (3.1%). AKI cases were associated with length of hospital stay, renal morbidity, and overall mortality, and this association was stage-dependent. The in-hospital mortality was 5.1% for patients with stage 1 AKI, 13.7% for patients with stage 2 AKI, and 24.8% for patients with stage 3 AKI. An administrative coding for acute kidney injury (N17) was present in only 28.8% (11 481) of the AKI cases that were identified by creatinine criteria. Like the AKI cases overall, those that were identified by creatinine criteria but were not coded as AKI had significantly higher mortality, and this association was stage-dependent.

CONCLUSION

AKI episodes are common among hospitalized patients and are associated with considerable morbidity and mortality, yet they are inadequately documented and probably often escape the attention of the treating physicians.

Temporal change in characteristics and outcomes of acute kidney injury on renal replacement therapy in intensive care units: analysis of a nationwide administrative database in Japan, 2007-2016

Background

We aimed to examine recent trends in patient characteristics and mortality in patients with acute kidney injury (AKI) receiving renal replacement therapy (RRT), including continuous RRT (CRRT) and intermittent RRT (IRRT), in intensive care units (ICUs).

Methods

From the Diagnosis Procedure Combination database in Japan during 6 months (July–December) from 2007 to 2016, we identified patients with AKI who received RRT in ICUs. We restricted the study participants to those admitted to hospitals (in which both CRRT and IRRT were available) that participated in the Diagnosis Procedure Combination database for all 10 years. We examined the trends in patient characteristics and mortality overall, by RRT modality, and by main diagnosis category subgroup. Logistic regression was used to adjust for patient characteristics.

Results

We identified 51,758 patients starting RRT in 287 hospitals, including 39,471 (76.3%) and 12,287 (23.7%) patients starting CRRT and IRRT. The crude in-hospital mortality declined from 44.9 to 36.1% (P for trend < 0.001). Compared with 2007, the adjusted odds ratio (aOR) for in-hospital mortality was 0.66 (95% confidence interval (CI) 0.60–0.72) in 2016, and the decreasing trend was observed in both patients starting CRRT (aOR 0.67, 95% CI 0.61–0.75) and IRRT (0.58, 0.45–0.74), and in all subgroups except for coronary artery disease: sepsis aOR 0.68 (95% CI 0.57–0.81); cardiovascular surgery 0.58 (0.45–0.76); coronary artery disease 0.84 (0.60–1.19); non-coronary heart disease 0.78 (0.64–0.94); central nervous system disorders 0.42 (0.28–0.62); trauma 0.39 (0.21–0.72); and other 0.64 (0.50–0.82).

Conclusions

This nationwide study confirmed a consistent decline in mortality among patients with AKI on RRT in ICUs. The adjusted mortality also declined during the study period; however, physiological variables were not measured in this study and it is possible that RRT may have been indicated for patients with less severe AKI in more recent years.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2468-8) contains supplementary material, which is available to authorized users.

Outcomes after left ventricular assist device implantation in patients with acute kidney injury

OBJECTIVE

The study objective was to compare outcomes for patients with and without acute kidney injury during hospitalizations when left ventricular assist devices are implanted.

METHODS

By using the National Inpatient Sample from 2008 to 2013, we identified patients with an International Classification of Diseases, Ninth Revision procedure code for left ventricular assist device implantation (37.66). We ascertained the presence of acute kidney injury and acute kidney injury requiring dialysis using validated International Classification of Diseases, Ninth Revision codes. We used logistic regression to examine the association of nondialysis-requiring acute kidney injury and acute kidney injury requiring dialysis with mortality, procedural complications, and discharge destination.

RESULTS

We identified 8362 patients who underwent left ventricular assist device implantation, of whom 3760 (45.0%) experienced nondialysis-requiring acute kidney injury and 426 (5.1%) experienced acute kidney injury requiring dialysis. In-hospital mortality was 3.9% for patients without acute kidney injury, 12.2% for patients with nondialysis-requiring acute kidney injury, and 47.4% for patients with acute kidney injury requiring dialysis. Patients with nondialysis-requiring acute kidney injury and acute kidney injury requiring dialysis had higher adjusted odds of mortality (3.24, 95% confidence interval [CI], 2.04-5.13 and 20.8, 95% CI, 9.7-44.2), major bleeding (1.38, 95% CI, 1.08-1.77 and 2.44, 95% CI, 1.47-4.04), sepsis (2.69, 95% CI, 1.93-3.75 and 5.75, 95% CI, 3.46-9.56), and discharge to a nursing facility (2.15, 95% CI, 1.51-3.07 and 5.89, 95% CI, 2.67-12.99).

CONCLUSIONS

More than 1 in 10 patients with acute kidney injury and approximately 1 in 2 patients with acute kidney injury requiring dialysis died during their hospitalization, with only 30% of patients with acute kidney injury requiring dialysis discharged to home. This information is necessary to support shared decision-making for patients with advanced heart failure and acute kidney injury.

Relationship Between Level of Heart Type Fatty Acid Binding Protein (Before and after Procedures) with Acute Renal Failure after PCI in Patients Under PCI

BACKGROUND & OBJECTIVE

Acute renal failure (AKI) is one of the most important complications of PCI. Due to delay in creatinine increase, we need specific factors to detect AKI earlier. The aim of this study is to evaluate the valuable factors by focusing on HFAB-P that can be predictive for AKI after Percutaneous Coronary Intervention (PCI).

METHODS

This prospective study was performed on 95 patients (55 males and 44 females aged between 49-78 years) under PCI in Golestan and Imam Khomeini hospitals in Ahvaz. Patients were divided into three groups based on the development of AKI after the procedure: no AKI, severe AKI (doubling of serum creatinine or needing dialysis) and any type of AKI (increased creatinine ≥ 0/3 mg/dl or a 50% increase in the means of 1/5 times serum creatinine). The demographic and clinical characteristics of the patients, the medical history and the results of the HFABP marker, GFR, and creatinine before and after PCI were evaluated for all patients.

RESULTS

The progenies showed 6 patients with severe AKI, 17 patients with any type of AKI, and 72 patients without AKI. Diabetes (P = 0.003), hypertension (P = 0.027), gender of patients (P = 0.025) and hospital admission days (P <0.001) were significantly different among the groups. Patients' age and positive troponin were significantly higher in patients with AKI. HFABP was the only factor that had significant changes before and after PCI (P <0.001). The cut-off value of HFABP was 4.69 with 95.6% sensitivity and 84.7% specificity. It has a good negative predictive value of 98.39% which suggests it to be a good test for the AKI prediction. Glomerular Filtration Rate (GFR) and creatinine (Cr) were significantly different after PCI (P <0.001).

CONCLUSION

HFABP can be considered as a predictor for AKI after PCI. Moreover, our study suggests that evaluating several parameters such as Cr and GFR before and after PCI can predict the AKI development after PCI.

Increased incidence of acute kidney injury requiring dialysis in metropolitan France

Background

Acute kidney injury requiring dialysis (AKI-D) is associated with high mortality. Information about its epidemiology is nonetheless sparse in some countries. The objective of this study was to assess its epidemiology and prognosis in metropolitan France.

Methods

Using the French hospital discharge database, the study focused on adults hospitalized in metropolitan France between 2009 and 2014 and diagnosed with AKI-D according to the codes of the French common classification of medical procedures. Crude and standardized incidence rates (SIR) by gender and age were calculated. We explored the changes in patients’ characteristics, modalities of renal replacement therapy (RRT), in-hospital care, and mortality, along with their determinants. Trends over time in the SIR for AKI-D, its principal diagnoses, and comorbidities were analyzed with joinpoint models.

Results

Between 2009 and 2014, the AKI-D SIR increased from 475 (95% CI, 468 to 482) to 512 per million population (95% CI, 505 to 519). AKI-D was twice as high in men as women. Median age was 68 years. Over the study period, the AKI-D SIR steadily increased in all age groups, particularly in the elderly. The most common comorbidities were cardio-cerebrovascular diseases (64.8%), pulmonary disease (42.2%), CKD (33.8%), and diabetes (26.0%); all of these except CKD increased significantly over time. In 2009, heart failure (17.2%), sepsis (17.0%), AKI (13.0%), digestive diseases (10.7%), and shock (6.6%) were the most frequent principal diagnoses, with a significant increase in heart failure and digestive diseases. The proportion of patients with at least one ICU stay and continuous RRT increased from 80.3% to 83.9% and from 56.9% to 61.8% (p<0.001), respectively. In-hospital mortality was high but stable (47%) and higher in patients with an ICU stay.

Conclusions

This is the first exhaustive study in metropolitan France of the SIR for AKI-D. It shows this SIR has increased significantly over 6 years, together with ICU care and continuous RRT. In-hospital mortality is high but stable.

Short- and long-term outcomes after postsurgical acute kidney injury requiring dialysis

Objective

Prompt assessment of perioperative complications is critical for the comprehensive care of surgical patients. Acute kidney injury requiring dialysis (AKI-D) is associated with high mortality, yet little is known about how long-term outcomes of patients have evolved. The association of AKI-D with postsurgical outcomes has not been well studied.

Methods

We investigated patients from the National Health Insurance Research Database and validated by the multicenter Clinical Trial Consortium for Renal Diseases cohort. All patients with AKI-D 18 years or older undergoing four major surgeries (cardiothoracic, esophagus, intestine, and liver) were retrospectively investigated (N=106,573). Patient demographics, surgery type, comorbidities before admission, and postsurgical outcomes, including the in-hospital, 30-day, and long-term mortality together with dialysis dependence were collected.

Results

AKI-D is the top risk factor for 30-day and long-term mortality after major surgery. Of 1,664 individuals with AKI-D and 6,656 matched controls, AKI-D during the hospital stay was associated with in-hospital (adjusted hazard ratio [aHR]=3.04, 95% CI 2.79–3.31), 30-day (aHR=3.65, 95% CI 3.37–3.94), and long-term (aHR=3.22, 95% CI 3.01–3.44) mortality. Patients undergoing cardiothoracic surgery (CTS) showed less in-hospital (aHR=0.85, 95% CI 0.75–0.97), 30-day (aHR=0.79, 95% CI 0.70–0.89), and long-term (aHR=0.80, 95% CI 0.72–0.90) mortality compared with non-CTS patients with AKI-D. CTS patients had a high risk of 30-day dialysis dependence (subhazard ratio [sHR]=1.67, 95% CI 1.18–2.38), but the risk of long-term dialysis dependence was similar (sHR=1.38, 95% CI 0.96–2.00) after AKI-D by taking mortality as a competing risk. Non-CTS patients had more comorbidities of sepsis, azotemia, hypoalbuminemia, and metabolic acidosis compared with CTS patients.

Conclusion

AKI exhibits paramount effects on postsurgical outcomes that extend well beyond discharge from the hospital. The goal of the perioperative assessment should include the reassurance of enhancing renal function recovery among different surgeries, and optimized follow-up is warranted in attenuating the complications after postsurgical AKI has occurred.

Acute Kidney Injury Due to Diarrheal Illness Requiring Hospitalization: Data from the National Inpatient Sample

BACKGROUND

Diarrheal illness is a major reason for hospitalization, but data on consequent acute kidney injury (AKI) are sparse.

OBJECTIVE

To determine the incidence of AKI in infectious and non-infectious diarrheal illness requiring hospitalization and to identify correlates and outcomes of diarrhea-associated AKI.

DESIGN

Using data from the 2012 National Inpatient Sample (NIS), we created a cohort of patients with a primary diagnosis of diarrheal illness. Diarrheal illness, disease correlates, and AKI were defined by ICD-9 diagnosis codes. We used logistic regression with backward variable selection to determine factors independently associated with AKI in infectious and non-infectious diarrheal illness, as well as to determine the association of AKI with in-hospital mortality. We used generalized linear models to assess differences in length of stay and costs of hospitalization.

MAIN MEASURES

The primary outcome was AKI in hospitalized diarrheal illness. Secondary outcomes were in-hospital mortality, length of stay, and cost of hospitalization associated with AKI.

KEY RESULTS

One in ten adults hospitalized with diarrheal illness experienced AKI, with higher incidence rates in older adults. Chronic kidney disease (CKD) and hypertension were associated with increased odds of AKI (all diarrhea OR 4.81, 95% CI 4.52 to 5.12 and OR 1.33, 95% CI 1.27 to 1.40, respectively). AKI in diarrheal illness was associated with substantial increase in mortality (OR 5.05, 95% CI 4.47 to 5.72), length of stay (mean increase 1.7 days [95% CI 1.6 to 1.8]), and cost of hospitalization (mean increase $4411 [95% CI 4023 to 4800]).

CONCLUSION

Acute kidney injury is common and consequential among patients hospitalized for diarrheal illness. Persons with CKD and hypertension are the most susceptible, possibly due to diminished renal reserve and exacerbating effects of treatment with diuretics and renin-angiotensin-aldosterone system blockers. Proactive management of these unique pharmacologic and physiologic factors is necessary to prevent AKI in this vulnerable population.

Defining oliguria during cardiopulmonary bypass and its relationship with cardiac surgery-associated acute kidney injury

BACKGROUND

While urine flow rate ≤0.5 ml kg^-1 h^-1 is believed to define oliguria during cardiopulmonary bypass (CPB), it is unclear whether this definition identifies risk for acute kidney injury (AKI) . The purpose of this retrospective study was to evaluate if urine flow rate during CPB is associated with AKI.

METHODS

Urine flow rate was calculated in 503 patients during CPB. AKI in the first 48 h after surgery was defined by the Kidney Disease: Improving Global Outcomes classification. Adjusted risk factors associated with AKI and urine flow rate were assessed.

RESULTS

Patients with AKI [n=149 (29.5%)] had lower urine flow rate than those without AKI (P<0.001). The relationship between urine flow and AKI risk was non-linear, with an inflection point at 1.5 ml kg^-1 h^-1 Among patients with urine flow <1.5 ml kg^-1 h^-1, every 0.5 ml kg^-1 h^-1 higher urine flow reduced the adjusted risk of AKI by 26% (95% CI 13-37; P<0.001). Urine flow rate during CPB was independently associated with the risk for AKI. Age up to 80 years and preoperative diuretic use were inversely associated with urine flow rate; mean arterial pressure on CPB (when <87 mmHg) and CPB flow were positively associated with urine flow rate.

CONCLUSIONS

Urine flow rate during CPB <1.5 ml kg^-1 h^-1 identifies patients at risk for cardiac surgery-associated AKI. Careful monitoring of urine flow rate and optimizing mean arterial pressure and CPB flow might be a means to ensure renal perfusion during CPB.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT00769691 and NCT00981474.

Survival and Risk Factors Among Dialytic Acute Kidney Injury Patients After Cardiovascular Surgery

OBJECTIVE

Acute kidney injury (AKI) is a frequent postoperative complication after cardiovascular surgery. It has been described as a predictor of decreased survival rates, but how dialysis decreases survival when initiated on the postoperative period has yet to be determined. To analyze the survival of patients who presented postoperative AKI requiring dialysis up to 30 days after cardiovascular surgery and its risk factors is the aim of this study.

METHODS

Of the 5,189 cardiovascular surgeries performed in a 4-year period, 157 patients developed AKI requiring dialysis in the postoperative period. The Kaplan-Meier survival curve and log-rank test were used in the statistical analysis to compare the curves of categorical variables. P-value< 0.05 was considered significant.

RESULTS

Patient average survival was 546 days and mortality was 70.7%. The need for dialysis on the postoperative period decreased late survival. Risk factors for decreased survival included age (P<0.001) and postoperative complications (P<0.0003).

CONCLUSION

The average survival was approximately one year among dialytic patients. Age and postoperative complications were risk factors that determined decreased survival.

Renal haemodynamics and oxygenation during and after cardiac surgery and cardiopulmonary bypass

Acute kidney injury (AKI) is a common complication following cardiac surgery performed on cardiopulmonary bypass (CPB) and has important implications for prognosis. The aetiology of cardiac surgery-associated AKI is complex, but renal hypoxia, particularly in the medulla, is thought to play at least some role. There is strong evidence from studies in experimental animals, clinical observations and computational models that medullary ischaemia and hypoxia occur during CPB. There are no validated methods to monitor or improve renal oxygenation during CPB, and thus possibly decrease the risk of AKI. Attempts to reduce the incidence of AKI by early transfusion to ameliorate intra-operative anaemia, refinement of protocols for cooling and rewarming on bypass, optimization of pump flow and arterial pressure, or the use of pulsatile flow, have not been successful to date. This may in part reflect the complexity of renal oxygenation, which may limit the effectiveness of individual interventions. We propose a multi-disciplinary pathway for translation comprising three components. Firstly, large-animal models of CPB to continuously monitor both whole kidney and regional kidney perfusion and oxygenation. Secondly, computational models to obtain information that can be used to interpret the data and develop rational interventions. Thirdly, clinically feasible non-invasive methods to continuously monitor renal oxygenation in the operating theatre and to identify patients at risk of AKI. In this review, we outline the recent progress on each of these fronts.

Acute kidney injury among adult patients undergoing major surgery in a tertiary hospital in Nigeria

Background

Acute kidney injury (AKI) is an underreported but major cause of morbidity and mortality among patients undergoing major surgical interventions in sub-Saharan Africa (SSA). Whereas AKI is often seen following major cardiac surgery in high-income countries, a similar spectrum of surgical diseases and interventions is not seen in developing countries. The impacts on surgical outcomes have also not been well characterized in SSA. This study aimed at identifying risk factors, incidence and determinants and short-term outcomes of AKI among patients undergoing major surgery.

Methods

This was a cohort study of adult patients undergoing major surgery at the University College Hospital, Ibadan, Nigeria. Data obtained were sociodemographic details, risk factors for AKI, details of surgery, anaesthesia and intra-operative events and short-term outcomes. Blood samples were obtained for pre-operative (pre-op) full blood count, serum electrolytes, blood urea and creatinine (SCr). Post-operatively (Post-op) SCr was determined at 24 h, Day 7 post-op and weekly until each patient was discharged.

Results

A total of 219 subjects who had major surgery (86.3% elective) were enrolled. The median age of the patients was 46 (range 18-73) years and 72.6% were females. The surgeries performed were mostly simple mastectomies (37.4%), exploratory laparotomies (22.8%) and total thyroidectomies (16.4%). The incidences of AKI were 18.7% at 24 h and 17.4% at Day 7 post-op, while cumulative AKI incidence was 22.5% at 1-week post-op. Pre-op elevated SCr [odds ratio (OR) 3.86], sepsis (OR 2.69), anaemia (OR 2.91) and duration of surgery >120 min (OR 1.75) were independently associated with AKI. In-patient mortality was 20.4% in individuals with AKI and 5.3% in those without AKI (P < 0.01).

Conclusion

Peri-operative risk factors for AKI are common among patients undergoing major surgery in SSA hospitals. The cumulative incidence of AKI was high and independently associated with pre-op sepsis, anaemia, pre-existing kidney dysfunction and duration of surgery >120 min.

Infrequent Provision of Palliative Care to Patients with Dialysis-Requiring AKI

BACKGROUND AND OBJECTIVES

The use of palliative care in AKI is not well described. We sought to better understand palliative care practice patterns for hospitalized patients with AKI requiring dialysis in the United States.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using the 2012 National Inpatient Sample, we identified patients with AKI and palliative care encounters using validated International Classification of Diseases, Ninth Revision, Clinical Modification codes. We compared palliative care encounters in patients with AKI requiring dialysis, patients with AKI not requiring dialysis, and patients without AKI. We described the provision of palliative care in patients with AKI requiring dialysis and compared the frequency of palliative care encounters for patients with AKI requiring dialysis with that for patients with other illnesses with similarly poor prognoses. We used logistic regression to determine factors associated with the provision of palliative care, adjusting for demographics, hospital-level variables, and patient comorbidities.

RESULTS

We identified 3,031,036 patients with AKI, of whom 91,850 (3%) received dialysis. We observed significant patient- and hospital-level differences in the provision of palliative care for patients with AKI requiring dialysis; adjusted odds were 26% (95% confidence interval, 12% to 38%) lower in blacks and 23% (95% confidence interval, 3% to 39%) lower in Hispanics relative to whites. Lower provision of palliative care was observed for rural and urban nonteaching hospitals relative to urban teaching hospitals, small and medium hospitals relative to large hospitals, and hospitals in the Northeast compared with the South. After adjusting for age and sex, there was low utilization of palliative care services for patients with AKI requiring dialysis (8%)-comparable with rates of utilization by patients with other illnesses with poor prognosis, including cardiogenic shock (9%), intracranial hemorrhage (10%), and acute respiratory distress syndrome (10%).

CONCLUSIONS

The provision of palliative care varied widely by patient and facility characteristics. Palliative care was infrequently used in hospitalized patients with AKI requiring dialysis, despite its poor prognosis and the regular application of life-sustaining therapy.

Hospital procedure volume does not predict acute kidney injury after coronary artery bypass grafting-a nationwide study

Background

Acute kidney injury (AKI) is common after coronary artery bypass grafting (CABG) and is associated with poor outcome. Increased hospital procedure volume has been associated with better outcomes. However, the impact of hospital CABG volume on AKI needing dialysis (AKI-D) is less clear. We designed this study to examine (i) the impact of number of annual CABG procedures per hospital (CABG-vol) on AKI-D and inpatient mortality and (ii) if it modifies the relationship between AKI-D and mortality.

Methods

Using the Nationwide Inpatient Sample database from 2000 to 2010, we identified admissions with CABG and those with AKI-D using International Classification of Diseases, Ninth Revision, Clinical Modification codes. Multivariable logistic regressions were used to assess the impact of CABG-vol on AKI-D and mortality. We used restricted cubic splines to account for the nonlinear relationship between CABG-vol and mortality. We also evaluated the a priori interaction term between CABG-vol and AKI-D in the model for mortality.

Results

Of 4 002 730 hospitalizations for CABG, 0.7% (24 126) had AKI-D. On adjusted analysis, CABG-vol did not correlate with odds of developing AKI-D [odds ratio (OR) 0.99; 95% confidence interval (CI) 0.99–1.00] but was associated with mortality, though the association was nonlinear. AKI-D was a significant predictor of mortality with OR 7.58 (95% CI 6.81–8.44). The interaction of CABG-vol and AKI-D was not significant (P = 0.8).

Conclusions

Lower annual CABG hospital procedure volume is significantly associated with higher mortality but not with a higher incidence of AKI-D. AKI-D is associated with higher mortality in those undergoing CABG. However, there is no differential effect of hospital volume on odds of mortality due to AKI-D.

Epidemiology of AKI: Utilizing Large Databases to Determine the Burden of AKI

Large observational databases linking kidney function and other routine patient health data are increasingly being used to study acute kidney injury (AKI). Routine health care data show an apparent rise in the incidence of population AKI and an increase in acute dialysis. Studies also report an excess in mortality and adverse renal outcomes after AKI, although with variation depending on AKI severity, baseline, definition of renal recovery, and the time point during follow-up. However, differences in data capture, AKI awareness, monitoring, recognition, and clinical practice make comparisons between health care settings and periods difficult. In this review, we describe the growing role of large databases in determining the incidence and prognosis of AKI and evaluating initiatives to improve the quality of care in AKI. Using examples, we illustrate this use of routinely collected health data and discuss the strengths, limitations, and implications for researchers and clinicians.

Postoperative acute kidney injury following intraoperative blood product transfusions during cardiac surgery

Introduction:

This study explored the nature of the association between intraoperative usage of red blood cell, fresh frozen plasma, cryoprecipitate or platelet transfusions and acute kidney injury.

Methods:

A total of 1175 patients who underwent cardiac surgery between 2008 and 2013 were retrospectively analyzed. We assessed the association between: (1) preoperative patient characteristics and acute kidney injury, (2) intraoperative blood product usage and acute kidney injury, (3) acute kidney injury and 30-day mortality or re-hospitalization.

Results:

In our cohort of 1175 patients, 288 patients (24.5%) developed acute kidney injury. This included 162 (13.8%), 69 (5.9%) and 57 (4.9%) developing stage 1, stage 2 or stage 3 acute kidney injury, respectively. Increased red blood cell, fresh frozen plasma or platelet transfusions increased the odds of developing acute kidney injury. Specifically, every unit of red blood cells, fresh frozen plasma or platelets transfused was associated with an increase in the covariate-adjusted odds ratio of developing ⩾ stage 2 kidney injury of 1.18, 1.19 and 1.04, respectively.

Conclusions:

Intraoperative blood product transfusions were independently associated with an increased odds of developing acute kidney injury following cardiac surgery. Further randomized studies are needed to better define intraoperative transfusion criteria.

Acute kidney injury in octogenarians after heart valve replacement surgery: a study of two periods over the last decade

Background

Data on postoperative acute kidney injury (AKI) in octogenarians are limited. This study examines the AKI occurrence and clinical impact in octogenarians following open-heart valve replacement surgery in two periods over the last 15 years.

Methods

A total of 452 consecutive octogenarians (non–kidney transplant and non-dialysis) who underwent heart valve replacement at the Mayo Clinic during the years 2011–13 (contemporary cohort) were examined. The results were compared with a comparable 209 consecutive octogenarians in 2002–03 (past cohort). Pre-existing chronic kidney disease (CKD) was defined based on estimated glomerular filtration rate (Chronic Kidney Disease Epidemiology Collaboration formula). Outcomes included postoperative AKI defined by the Acute Kidney Injury Network (AKIN) criteria, length of hospital stay (LOS), discharge disposition and patient survival (hospital and 1 year).

Results

AKI occurrence in the contemporary cohort was lower than the past cohort (35% versus 47%, respectively, P < 0.003). Compared with the past cohort, the contemporary cohort had fewer known perioperative AKI risk factors (pre-existing CKD, comorbidity, heart failure, surgical duration, cross-clamp time, blood transfusion and large-volume intravenous fluids). In both periods, AKI adversely impacts mortality, LOS and discharge to a care facility.

Conclusions

Postoperative AKI in octogenarians following heart valve replacement surgery has declined over the last decade. As a result, the AKI-attributable percentage mortality has accordingly decreased. However, AKI continues to exert a heavy morbidity and mortality burden. These results are highly pertinent to practice since the octogenarian population is growing.

Improved long-term survival and renal recovery after acute kidney injury in hospitalized patients: A 20 year experience

AIM

Acute kidney injury (AKI) is a common complication of medical and surgical interventions in hospitalized patients and associates with high mortality. Our aim was to examine renal recovery and long-term survival and time trends in AKI survival.

METHODS

Changes in serum creatinine (SCr) were used to define AKI in patients at Landspitali University Hospital in Iceland from 1993 to 2013. Renal recovery was defined as SCr < 1.5× baseline.

RESULTS

Out of 25 274 individuals who had their highest measured SCr during hospitalization and an available baseline SCr, 10,419 (41%) had AKI during hospitalization (H-AKI), 19%, 11% and 12% with Stage 1, 2 and 3, respectively. The incidence of H-AKI increased from 18.6 (95% CI, 14.7-22.5) to 29.9 (95% CI, 26.7-33.1) per 1000 admissions/year over the study period. Survival after H-AKI was 61% at 90-days and 51% at one year. Comparing H-AKI patients to propensity score matched individuals the hazard ratio for death was 1.49 (1.36-1.62), 2.17 (1.95-2.41) and 2.95 (2.65-3.29) for Stage 1, 2 and 3, respectively. One-year survival of H-AKI patients improved from 47% in 1993-1997 to 57% in 2008-2013 and the adjusted hazard ratio for mortality improved, compared to the first 5-year period, 0.85 (0.81-0.89), 0.67 (0.64-0.71), and 0.57 (0.53-0.60) for each subsequent 5-year interval. Recovery of renal function was achieved in 88%, 58% and 44% of patients in Stages 1, 2 and 3, respectively, improving with time.

CONCLUSIONS

Acute kidney injury is an independent predictor of long-term mortality in hospitalized patients but there has been a marked improvement in survival and renal recovery over the past two decades.

Gastrointestinal Bleeding During the Index Hospitalization for Mechanical Circulatory Support Devices Implantation, a Nationwide Perspective

BACKGROUND

Gastrointestinal bleeding (GIB) is a common adverse event after mechanical circulatory support device implantation. However, the majority of the reported data were obtained from small single-center studies. Our aim was to study the prevalence and predictors of GIB during the index hospitalization of mechanical circulatory support devices implantation using a nationwide database.

METHODS

Nationwide inpatient sample (2009-2011) was used to perform a retrospective cross-sectional study. Adult patients with discharge diagnosis codes of congestive heart failure and procedure codes of left-ventricular assist device (LVAD) or intra-aortic balloon pump (IABP) implantation or orthotopic heart transplant (OHT, reference group) were identified. Our outcome was GIB during the index hospitalization when the device was implanted. Predictors that achieved statistical significance on the univariate analysis were included in a multivariable logistic-regression analysis.

RESULTS

A total of 87,462 patients were included, 87 % of the patients received an IABP, 6 % received LVAD, and 5 % underwent OHT. Prevalence of GIB was 8, 5, and 3 % among those who had LVAD, IABP implantation, and OHT recipients, respectively (p < 0.001). Patients who underwent LVAD implantation had twofold increase in the prevalence of GIB (OR 2.1, 1.7-2.5, p < 0.001) when using IABP or OHT groups as a reference. This increase in the prevalence was not demonstrated among IABP recipients on a multivariate level.

CONCLUSION

Prevalence of GIB was higher among LVAD compared to OHT and IABP recipients and could occur as early as the index admission of the device implantation.

Trends in One-Year Outcomes of Dialysis-Requiring Acute Kidney Injury in Denmark 2005-2012: A Population-Based Nationwide Study

BACKGROUND

Dialysis-requiring acute kidney injury (AKI) is associated with substantial mortality and risk of end-stage renal disease (ESRD). Despite considerable growth in incidence of severe AKI, information pertaining to trends in outcomes remains limited. We evaluated time trends in one year risks of ESRD and death in patients with dialysis-requiring AKI over an eight year period in Denmark.

METHODS

In a retrospective nationwide study based on national registers, all adults requiring acute renal replacement therapy between 2005 and 2012 were identified. Patients with preceding ESRD were excluded. Through individual-level cross-referencing of administrative registries, information pertaining to comorbidity, preceding surgical interventions, and concurrent other organ failure and sepsis was ascertained. Comparisons of period-specific one year odds ratios for ESRD and death were calculated in a multiple logistic regression model.

RESULTS

A total of 13,819 patients with dialysis-requiring AKI were included in the study. Within one year, 1,017 (7.4%) patients were registered with ESRD, and 7,908 (57.2%) patients died. The one-year rate of ESRD decreased from 9.0% between 2005 and 2006 to 6.1% between 2011 and 2012. Simultaneously, the one-year mortality rate decreased from 58.2% between 2005 and 2006 to 57.5% between 2011 and 2012. Consequently, the adjusted odds ratios for the period 2011-2012 (with the period 2005-2006 as reference) were 0.75 (0.60-0.95, p = 0.015) and 0.87 (95% CI 0.78-0.97, p = 0.010) for ESRD and death, respectively.

CONCLUSIONS

In a nationwide retrospective study on time trends in one year outcomes following dialysis-requiring AKI, risk of all-cause mortality and ESRD decreased over a period of 8 years.

Hospital Mortality in the United States following Acute Kidney Injury

Acute kidney injury (AKI) is a common reason for hospital admission and complication of many inpatient procedures. The temporal incidence of AKI and the association of AKI admissions with in-hospital mortality are a growing problem in the world today. In this review, we discuss the epidemiology of AKI and its association with in-hospital mortality in the United States. AKI has been growing at a rate of 14% per year since 2001. However, the in-hospital mortality associated with AKI has been on the decline starting with 21.9% in 2001 to 9.1 in 2011, even though the number of AKI-related in-hospital deaths increased almost twofold from 147,943 to 285,768 deaths. We discuss the importance of the 71% reduction in AKI-related mortality among hospitalized patients in the United States and draw on the discussion of whether or not this is a phenomenon of hospital billing (coding) or improvements to the management of AKI.