AKI associated with cardiac surgery

Developing Biomarker Panels to Predict Progression of Acute Kidney Injury After Cardiac Surgery

Introduction

Acute kidney injury (AKI) is a frequent complication of cardiac surgery, but only a fraction of cardiac surgery patients that experience postoperative AKI have progression to more severe stages. Biomarkers that can distinguish patients that will experience progression of AKI are potentially useful for clinical care and/or the development of therapies.

Methods

Data come from a prospective cohort study of cardiac surgery patients; the analytic dataset contained data from 354 cardiac surgery patients meeting criteria for AKI following surgery. Candidate predictors were 38 biomarkers of kidney function, insult, or injury measured at the time of AKI diagnosis. The outcome was AKI progression, defined as worsening of AKI Network stage. We investigated combining biomarkers with Bayesian model averaging (BMA) and random forests of classification trees, with and without center transformation. For both approaches, we used resampling-based methods to avoid optimistic bias in our assessment of model performance.

Results

BMA yielded a combination of 3 biomarkers and an optimism-corrected estimated area under the receiver operating characteristic curve (AUC) of 0.75 (95% confidence interval [CI]: 0.68, 0.82). The random forests approach, which nominally uses all biomarkers, had an estimated AUC of 0.74 (95% CI: 0.66, 0.82). A second application of random forests applied to biomarker values after a center-specific transformation had an estimated AUC of 0.80 (95% CI: 0.72, 0.88).

Conclusion

These findings suggest that the application of advanced statistical techniques to combine biomarkers offers only modest improvements over use of single biomarkers alone. This exemplifies a common experience in biomarker research: combinations of modestly performing biomarkers often also have modest performance.

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.

Heterogeneity of Cause, Care, and Prognosis in Severe Acute Kidney Injury in Hospitalized Patients: A Prospective Observational Study

Background:

KDIGO (Kidney Disease: Improving Global Outcomes) defines acute kidney injury (AKI) solely by serum creatinine (SCr) and urine output variation. Severe AKI is a syndrome covering various clinical situations.

Objective:

To describe severe AKI heterogeneity by department of hospitalization.

Design:

This is a prospective observational single-center study.

Setting:

Adult patients hospitalized in a French tertiary hospital from August 2016 to December 2017.

Patients:

All adults with severe AKI, defined by dialysis for AKI or an increase in SCr above 354 μmol/L.

Measurements:

Patient characteristics, clinical and laboratory presentation, AKI cause, medical indication for renal replacement therapy (RRT), planned palliative care, and vital status 30 days after severe AKI.

Methods:

A global description of patient characteristics, care, and prognosis and comparison by department of hospitalization: intensive care unit (ICU), nephrology, and others.

Results:

The study included 480 patients (73% men, median age: 72 years, range: 64-83), with medical histories including cardiovascular disease, diabetes, cancer, and chronic kidney disease. Principal causes were sepsis (104; 22%), hypovolemia (98; 20%), obstructive AKI (84; 18%), acute tubular necrosis (ATN; 74; 15%), and cardiorenal syndrome (51; 11%). Severe AKI was diagnosed in the ICU for 188 (39%) patients, the nephrology department for 130 (27%), and in other wards for 162 (34%). Patient characteristics differed by department for age, comorbidity, cause, and RRT use and indications. Palliative care was planned for 72 (15%) patients, most frequently in other wards.

Limitations:

We studied a subgroup of stage 3 KDIGO AKI patients in a single center without cardiac surgery.

Conclusion:

Patients hospitalized for severe AKI have frequent and various comorbidities, different clinical presentations, care, hospitalization in various departments, and different prognosis. The heterogeneity of this severe AKI implies the need for personalized care, which requires prognostic tools that include information besides SCr and diuresis.

Predictors for acute and chronic renal failure and survival in patients supported with veno-arterial extracorporeal membrane oxygenation

BACKGROUND

Renal failure is a common occurrence in patients with refractory cardiogenic shock including those supported with veno-arterial extracorporeal membrane oxygenation. Prevalence and outcome of acute and chronic kidney failure in extracorporeal membrane oxygenation patients have not been well documented. In this study, we investigated the occurrence of acute and chronic kidney failure in veno-arterial extracorporeal membrane oxygenation patients as well as predictors for survival.

METHODS

This is a single center retrospective clinical study. We included adult patients with refractory cardiogenic shock who were supported by veno-arterial extracorporeal membrane oxygenation between 2008 and 2015. The primary endpoint of the study was acute kidney injury (KDIGO Stage 3) during extracorporeal membrane oxygenation and chronic kidney failure requiring renal replacement therapy, 30 and 90 days after extracorporeal membrane oxygenation. The secondary endpoint was in-hospital survival and 90-day survival.

RESULTS

A total of 196 veno-arterial extracorporeal membrane oxygenation patients were investigated. In total, 41.8% (82/196) patients had acute renal failure requiring continuous renal replacement therapy during extracorporeal membrane oxygenation. The 30- and 90-day survival was 55.1% (108/196) and 48.5% (95/196), respectively; 21.3% (23/108) and 11.6% (11/95) patients needed renal replacement therapy after 30 and 90 days, respectively. Predictors for KDIGO Stage 3 renal failure during extracorporeal membrane oxygenation were lactate (p = 0.026) and the number of blood units transfused during extracorporeal membrane oxygenation support (p = 0.000). A predictor for renal replacement therapy after 30 and 90 days was an elevated plasma-free hemoglobin level. The in-hospital survival was 54.6% (107/196). Serum lactate of less than 4.3 mmol/L, lower age, plasma-free hemoglobin of ⩽62 mg/dL, low number of blood units transfused during extracorporeal membrane oxygenation, and the use of an intra-aortic balloon pump were predictors for in-hospital and 90-day survival.

Amniotic fluid stem cells ameliorate cisplatin-induced acute renal failure through induction of autophagy and inhibition of apoptosis

Background

We have recently demonstrated that amniotic fluid stem cells (AFSC) express renal progenitor markers and can be differentiated in vitro into renal lineage cell types, viz, juxtaglomerular and renal proximal tubular epithelial-like cells. Here, we have evaluated the therapeutic efficacy of AFSC in a cisplatin-induced rat model of acute renal failure (ARF) and investigated the underlying mechanisms responsible for their renoprotective effects.

Methods

ARF was induced in Wistar rats by intra-peritoneal injection of cisplatin (7 mg/kg). Five days after cisplatin injection, rats were randomized into two groups and injected with either AFSC or normal saline intravenously. On days 8 and 12 after cisplatin injection, the blood biochemical parameters, histopathological changes, apoptosis and expression of pro-apoptotic, anti-apoptotic, and autophagy-related proteins in renal tissues were studied in both groups of rats. To further confirm whether the protective effects of AFSC on cisplatin-induced apoptosis were dependent on autophagy, chloroquine, an autophagy inhibitor, was administered by the intra-peritoneal route.

Results

Administration of AFSC in ARF rats resulted in improvement of renal function and attenuation of renal damage as reflected by significant decrease in blood urea nitrogen, serum creatinine levels, tubular cell apoptosis as assessed by Bax/Bcl2 ratio, and expression of the pro-apoptotic proteins, viz, PUMA, Bax, cleaved caspase-3, and cleaved caspase-9, as compared to the saline-treated group. Furthermore, in the AFSC-treated group as compared to the saline-treated group, there was a significant increase in the activation of autophagy as evident by increased expression of LC3-II, ATG5, ATG7, Beclin1, and phospho-AMPK levels with a concomitant decrease in phospho-p70S6K and p62 expression levels. Chloroquine administration led to significant reduction in the anti-apoptotic effects of the AFSC therapy and further deterioration in the renal structure and function caused by cisplatin.

Conclusion

AFSC led to amelioration of cisplatin-induced ARF which was mediated by inhibition of apoptosis and activation of autophagy. The protective effects of AFSC were blunted by chloroquine, an inhibitor of autophagy, highlighting that activation of autophagy is an important mechanism of action for the protective role of AFSC in cisplatin-induced renal injury.

Secretory Leukocyte Protease Inhibitor (SLPI)-A Novel Predictive Biomarker of Acute Kidney Injury after Cardiac Surgery: A Prospective Observational Study

Acute kidney injury (AKI) is one of the most frequent complications after cardiac surgery and is associated with poor outcomes. Biomarkers of AKI are crucial for the early diagnosis of this condition. Secretory leukocyte protease inhibitor (SLPI) is an alarm anti-protease that has been implicated in the pathogenesis of AKI but has not yet been studied as a diagnostic biomarker of AKI. Using two independent cohorts (development cohort (DC), n = 60; validation cohort (VC), n = 148), we investigated the performance of SLPI as a diagnostic marker of AKI after cardiac surgery. Serum and urinary levels of SLPI were quantified by ELISA. SLPI was significantly elevated in AKI patients compared with non-AKI patients (6 h, DC: 102.1 vs. 64.9 ng/mL, p < 0.001). The area under the receiver operating characteristic curve of serum SLPI 6 h after surgery was 0.87 ((0.76–0.97); DC). The addition of SLPI to standard clinical predictors significantly improved the predictive accuracy of AKI (24 h, VC: odds ratio (OR) = 3.91 (1.44–12.13)). In a subgroup, the increase in serum SLPI was evident before AKI was diagnosed on the basis of serum creatinine or urine output (24 h, VC: OR = 4.89 (1.54–19.92)). In this study, SLPI was identified as a novel candidate biomarker for the early diagnosis of AKI after cardiac surgery.

The impact of mild renal dysfunction on isolated cardiopulmonary coronary artery bypass grafting: a retrospective propensity score matching analysis

BACKGROUND

Mild preoperative renal dysfunction (RD) is not rare in patients receiving isolated cardiopulmonary coronary artery bypass grafting (CCABG). However, there are not too many studies about the impact of mild preoperative RD on in-hospital and follow-up outcomes after isolated CCABG. This single-centre, retrospective propensity score matching study designed to study the impact of mild preoperative RD on in-hospital and long-term outcomes after first isolated CCABG.

METHODS

After propensity score matching, 1144 patients with preoperative estimated glomerular filtration rate (eGFR) of more than 60 ml/min/1.73 m² receiving first isolated CCABG surgery from January 2012 to December 2015 entered the study, who were divided into 2 groups: A group (eGFR ≥90 ml/min/1.73 m2, n = 572) and B group (eGFR of 60-89 ml/min/1.73 m2, n = 572). The in-hospital and long-term outcomes were recorded and analyzed. The mean follow-up time was 54.4 ± 10.7 months. Acute kidney injury (AKI) was defined and classified according to the Acute Kidney Injury Network (AKIN) criteria.

RESULTS

The 2 propensity score-matched groups had similar baseline and procedure except the baseline eGFR. There were 8 patients died in A group (mortality is 1.4%) and 14 died in B group (mortality is 2.5%) during the in hospital and 30-day postoperatively(χ² = 1.159, p = 0.282). There were totally 38 patients lost to follow-up, 18 in group A and 20 in group B. 21 patients died in group A and 37 died in group B during the follow-up, and long-term survival in group A was higher than in group B (96.2% vs 93.1%, χ² = 4.336, p = 0.037). Comparing with group A, group B was associated with an increased rates and severity of AKI postoperatively (total AKI: 62 vs 144. AKIN stageI: 54 vs 113; AKIN stageII: 6 vs 22; AKIN stageIII: 2 vs 9, p<0.0001). During follow-up, group B also had a higher rate of new onset of dialysis (0 vs 6, χ² = 4.432, p = 0.039). Multivariable logistic regression showed that comparing with A group, the HR for long-term mortality and new onset of dialysis in B group was 1.67 and 1.52 respectively (95%CI 1.09-2.90, p = 0.035; 95%CI 1.14-2.49, p = 0.027).

CONCLUSIONS

Comparing with normal preoperative renal function, patients with mild preoperative RD had a similar in-hosptial mortality, but with an increased in-hosptial rates and severity of AKI, and with a decreased long-term survival and increased long-term new onset of dialysis.

Acute kidney injury is independently associated with mortality and resource use after emergency general surgery operations

INTRODUCTION

The incidence of severe perioperative renal dysfunction in high-acuity patients has not been well-explored at the national level. The present study aimed to evaluate the trends in the incidence of perioperative acute kidney injury and renal replacement therapy as well as associated mortality among patients undergoing an emergency general surgery operation.

METHODS

This was a retrospective cohort study using the National Inpatient Sample to identify all adult patients (>18 y) without chronic kidney disease who underwent an emergency general surgery procedure from 2008 to 2016. The study cohort was stratified based on presence of acute kidney injury and need for renal replacement therapy postoperatively. A multivariable logistic regression model was developed to predict the odds of mortality and composite morbidity. Nonparametric trend analyses of acute kidney injury and renal replacement therapy incidence and associated mortality were performed.

RESULTS

Of an estimated 5,862,657 patients who underwent an emergency general surgery procedure during the study period, 7.4% patients developed an acute kidney injury and 0.48% patients required renal replacement therapy. Overall, the incidence of acute kidney injury (5.3%-19.4%) and renal replacement therapy (0.43%-0.93%) increased (P < .0001) over the study period. Even without need for renal replacement therapy, acute kidney injury was associated with greater odds of mortality and composite morbidity (adjusted odds ratio 5.2, 95% confidence interval [CI] 5.1-5.3) and mortality (adjusted odds ratio = 2.20, 95% CI 2.3-2.4), as well as greater costs of hospitalization and duration of stay.

CONCLUSION

In this national study, we found that the incidence of acute kidney injury and renal replacement therapy after an emergency general surgery operation has increased. Both acute renal failure and hemodialysis were associated with much greater odds of morbidity and mortality. The apparent increase in the rate of acute kidney injury and renal replacement therapy warrant further investigation of mechanisms for monitoring and limiting the impact of organ malperfusion associated with emergency general surgery operations.

Emerging Role of Ferroptosis in Acute Kidney Injury

Acute kidney injury (AKI) is a heterogeneous group of critical disease conditions with high incidence and mortality. Vasoconstriction, oxidative stress, apoptosis, and inflammation are generally thought to be the main pathogenic mechanisms of AKI. Ferroptosis is a type of iron-dependent nonapoptotic cell death characterized by membrane lipid peroxide accumulation and polyunsaturated fatty acid consumption, and it plays essential roles in many diseases, including cancers and neurologic diseases. Recent studies have revealed an emerging role of ferroptosis in the pathophysiological processes of AKI. Here, in the present review, we summarized the most recent discoveries on the role of ferroptosis in the pathogenesis of AKI as well as its therapeutic potential in AKI.

Associations between preoperative continuation of renin-angiotensin system inhibitor and cardiac surgery-associated acute kidney injury: a propensity score-matching analysis

BACKGROUND

Cardiac surgery-associated acute kidney injury (CSA-AKI) is associated with high risk for complications and mortality. Whether renin-angiotensin system (RAS) inhibitor should be continued or withdrawn in patients with long-term use before cardiac surgery has been lack of consensus.

METHODS

We performed this prospective observational cohort study and recruited cardiac surgery patients in the surgical intensive care units between 2000 and 2011. These patients were divided into users and non-users of RAS inhibitor. Propensity score matching and multivariable models were performed to investigate the association between renal outcome, mortality, and preoperative use of RAS inhibitor.

RESULTS

Preoperative use of RAS inhibitor was identified as the independent protective factor for AKI development (OR 0.41, 95% CI 0.23, 0.63), AKI severity (stage 3 vs. stage 1, OR 0.35, 95% CI 0.18, 0.69), and renal recovery (OR 3.41, 95% CI 1.84, 5.36). Nevertheless, there was no significant protective effect of RAS inhibitor on in-hospital dialysis, in-hospital mortality, and ensuing development of chronic kidney disease (CKD) after AKI. We created a prediction model of CSA-AKI and indicated that preoperative use of RAS inhibitor provided more protective effect in low-risk than high-risk population.

CONCLUSION

Preoperative use of RAS inhibitor was associated with less AKI development and severity, and higher renal recovery. Although more risk reduction of AKI development was shown in low-risk group by our prediction model, continued use of RAS inhibitor before cardiac surgery could provide protective effect in all patients.

Remote ischaemic preconditioning for renal and cardiac protection in adult patients undergoing cardiac surgery with cardiopulmonary bypass: systematic review and meta-analysis of randomized controlled trials

Background

The main aim of this systematic review was to assess whether remote ischaemic preconditioning (RIPC) protects kidneys and the heart in cardiac surgery with cardiopulmonary bypass (CPB) and to investigate a possible role of anaesthetic agents.

Methods

Randomized clinical trials (RCTs) on the effects of RIPC through limb ischaemia in adult patients undergoing cardiac surgery with CPB were searched (1965-October 2016) in PubMed, Cochrane Library and article reference lists. A random effects model on standardized mean difference (SMD) for continuous outcomes and the Peto odds ratio (OR) for dichotomous outcomes were used to meta-analyse data. Subgroup analyses to evaluate the effects of different anaesthetic regimens were pre-planned.

Results

Thirty-three RCTs (5999 participants) were included. In the whole group, RIPC did not significantly reduce the incidence of acute kidney injury (AKI), acute myocardial infarction, atrial fibrillation, mortality or length of intensive care unit (ICU) and hospital stays. On the contrary, RIPC significantly reduced the area under the curve for myocardial injury biomarkers (MIBs) {SMD -0.37 [95% confidence interval (CI) -0.53 to - 0.21]} and the composite endpoint incidence [OR 0.85 (95% CI 0.74-0.97)]. In the volatile anaesthetic group, RIPC significantly reduced AKI incidence [OR 0.57 (95% CI 0.41-0.79)] and marginally reduced ICU stay. Conversely, except for MIBs, RIPC had fewer non-significant effects under propofol with or without volatile anaesthetics.

Conclusions

RIPC did not consistently reduce morbidity and mortality in adults undergoing cardiac surgery with CPB. In the subgroup on volatile anaesthetics only, RIPC markedly and significantly reduced the incidence of AKI and composite endpoint as well as myocardial injury.

Influence of preoperative serum creatinine level and intraoperative volume of contrast medium on the risk of acute kidney injury after transfemoral transcatheter aortic valve implantation: a retrospective observational study

Objective

This study aimed to determine if contrast medium volume (CMV) is a risk factor for acute kidney injury (AKI) during transcatheter aortic valve implantation (TAVI) via a transfemoral approach performed without major complications. All TAVI procedures performed at our institution between March 2014 and March 2018 were retrospectively reviewed. AKI was diagnosed using the Acute Kidney Injury Network classification based on the Valve Academic Research Consortium-2 definition. Procedures performed via a transapical approach and those in which circulatory dynamics failed intraoperatively were excluded.

Results

Eighty-one (96.4%) of 100 patients scheduled for TAVI were enrolled; seven (8.6%) developed AKI and 74 (91.4%) did not. The serum creatinine (SCr) level was significantly higher (p < 0.05) and the estimated glomerular filtration rate was significantly lower in the AKI group (p < 0.05). The CMV was significantly higher in the AKI group (103 ml vs 84 ml, p < 0.05), as was the CMV × SCr/BW value (3.34 vs 1.49, p < 0.01). The area under the curve for CMV × SCr/BW was 0.9228 and the cut-off value was 2.99. The CMV, SCr, and estimated glomerular filtration rate affect the likelihood of AKI after transfemoral TAVI and a CMV × SCr/BW value > 2.99 accurately predicts AKI.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4527-2) contains supplementary material, which is available to authorized users.

Biomarkers of Acute Kidney Injury after Cardiac Surgery: A Narrative Review

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a major and serious complication in patients undergoing cardiac surgery and is independently associated with perioperative mortality and mortality. Therapeutic intervention aiming at reversing kidney dysfunction seems disappointing across multiple settings. Consequently, attention has shifted from treatment to prevention and early detection. The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines have unified diagnostic standards mainly based on the serum creatinine (Scr) level or urine output, but neither marker is kidney specific. Efforts have been made to identify novel biomarkers with high sensitivity and specificity. The diagnostic capabilities of neutrophil gelatinase-associated lipocalin (NGAL) and G1 cell cycle arrest biomarker as biomarkers have been confirmed in a large number of clinical trials. The utility of biomarkers of cardiac function and inflammation has been validated in clinical studies. Aiming to offer valuable information for further research, we summarize the progress in defining current markers relevant to CSA-AKI in the last three years.

Risk factors of cardiac surgery-associated acute kidney injury: development and validation of a perioperative predictive nomogram

OBJECTIVE

Cardiac surgery-associated acute kidney injury (CSA-AKI), one of the most severe complications in patients with cardiac surgery, is associated with considerable morbidity, mortality and high costs thus placing a heavy burden to society. Therefore, we aimed to build a predictive model based on preoperative features in order to early recognize and intervene for patients with high risk of CSA-AKI.

METHODS

In this retrospective cohort study, baseline perioperative hospitalization information of patients who underwent cardiac surgery from October 2012 to October 2017 were screened. After multivariate logistic regression, identified independent predictive factors associated with CSA-AKI were incorporated into the nomogram and the discriminative ability and predictive accuracy of the model was assessed by concordance index (C-Index). Additionally, internal validation was performed by using bootstrapping technology with 1000 resamples to reduce the over-fit bias.

RESULTS

In all 4395 patients with cardiac surgery October 2012-October 2017, no patients were excluded for the continuous renal replacement therapy (CRRT) before surgery while 2495 patients were excluded due to only one or less than one Scr assay post-surgery. In the end, a total of 1900 patients were enrolled in the study, of which 698 patients (74.89%) developed AKI stage 1, 158 (16.96%) AKI stage 2 and 76 (8.15%) AKI stage 3. After multivariate logistic regression, age, perioperative estimated glomerular filtration rate (eGFR), lactate dehydrogenase (LDH), prothrombin time (PT), with a history of surgery, transfusion, cardiac arrhythmia, coronary heart disease (CHD), or chronic kidney disease (CKD), using calcium channel blocker (CCB), proton pump inhibitors (PPI), non-steroidal anti-inflammatory drugs (NSAID), antibiotic or statin before surgery were predictive factors of CSA-AKI. In addition, the nomogram demonstrated a good accuracy in estimating CSA-AKI, with an C-Index and a bootstrap-corrected one of 0.796 (SD = 0.018, 95% CI 0.795-0.797) and 0.789 (SD = 0.015, 95% CI 0.788-0.790), respectively. Moreover, calibration plots showed an optimal consistency with the actual presence of CSA-AKI.

CONCLUSION

The novel predictive nomogram achieved a good preoperative prediction of CSA-AKI within the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Though the model, the risk of an individual patient with "subclinical AKI" undergoing cardiac surgery could be determined earlier and such application was helpful for timely intervention in order to improve patient's prognosis.

Safety of a Restrictive versus Liberal Approach to Red Blood Cell Transfusion on the Outcome of AKI in Patients Undergoing Cardiac Surgery: A Randomized Clinical Trial

BACKGROUND

Safely reducing red blood cell transfusions can prevent transfusion-related adverse effects, conserve the blood supply, and reduce health care costs. Both anemia and red blood cell transfusion are independently associated with AKI, but observational data are insufficient to determine whether a restrictive approach to transfusion can be used without increasing AKI risk.

METHODS

In a prespecified kidney substudy of a randomized noninferiority trial, we compared a restrictive threshold for red blood cell transfusion (transfuse if hemoglobin<7.5 g/dl, intraoperatively and postoperatively) with a liberal threshold (transfuse if hemoglobin<9.5 g/dl in the operating room or intensive care unit, or if hemoglobin<8.5 g/dl on the nonintensive care ward). We studied 4531 patients undergoing cardiac surgery with cardiopulmonary bypass who had a moderate-to-high risk of perioperative death. The substudy's primary outcome was AKI, defined as a postoperative increase in serum creatinine of ≥0.3 mg/dl within 48 hours of surgery, or ≥50% within 7 days of surgery.

RESULTS

Patients in the restrictive-threshold group received significantly fewer transfusions than patients in the liberal-threshold group (1.8 versus 2.9 on average, or 38% fewer transfusions in the restricted-threshold group compared with the liberal-threshold group; P<0.001). AKI occurred in 27.7% of patients in the restrictive-threshold group (624 of 2251) and in 27.9% of patients in the liberal-threshold group (636 of 2280). Similarly, among patients with preoperative CKD, AKI occurred in 33.6% of patients in the restrictive-threshold group (258 of 767) and in 32.5% of patients in the liberal-threshold group (252 of 775).

CONCLUSIONS

Among patients undergoing cardiac surgery, a restrictive transfusion approach resulted in fewer red blood cell transfusions without increasing the risk of AKI.

External aortic clamping versus endoaortic balloon occlusion in minimally invasive cardiac surgery: a systematic review and meta-analysis

OBJECTIVES

Minimally invasive cardiac valve surgery is safe, effective and increasingly popular. It is performed worldwide with the use of either external aortic clamping or endoaortic balloon occlusion.

METHODS

We conducted a literature search using MEDLINE, EMBASE, Scopus and Web of Science. Primary outcomes included aortic dissection, conversion to sternotomy, mortality, stroke and cross-clamp time. Secondary outcomes included atrial fibrillation, acute kidney injury, reoperation for bleeding, cardiopulmonary bypass times, myocardial infarction, use of intra-aortic balloon pump and length of hospital stay. The random effects model was used to calculate the outcomes of both binary and continuous data.

RESULTS

Thirty retrospective studies were included in the meta-analysis. The incidence of aortic dissection (pooled odds ratio = 3.88, 95% confidence interval = 1.06-14.18; P =0.04) and conversion to sternotomy (pooled odds ratio = 3.07, 95% confidence interval = 1.33-7.10; P = 0.009) was higher in the endoaortic balloon occlusion group than in the external aortic clamping group, in whom a direct comparison was possible. The remaining observational studies did not show any significant differences in either group. There was no significant difference in 30-day mortality (P = 0.37), stroke (P = 0.26), cross-clamp time (P = 0.20), atrial fibrillation (P = 0.18), acute kidney injury (P = 0.49), reoperation for bleeding (P = 0.24), cardiopulmonary bypass time (P = 0.06), myocardial infarction (P = 0.74), use of intra-aortic balloon pump (P = 0.11) or length of hospital stay (P = 0.47).

CONCLUSIONS

External aortic clamping may be safer than endoaortic balloon occlusion with respect to aortic dissection and conversion to sternotomy. However, mortality, length of stay, stroke, cross-clamp time and other cardiovascular complication rates were similar between the 2 techniques.

Adjusting cardiopulmonary bypass flow or arterial pressure to maintain renal medullary oxygen

Cardiopulmonary bypass leads to renal hypoperfusion, resulting in medullary hypoxia and acute kidney injury. In instrumented sheep subjected to cardiopulmonary bypass, Lankadeva et al. found that medullary perfusion and tissue oxygen tension (PO₂) was maintained at low-dose metaraminol, an α₁-adrenoceptor agonist, because low-dose metaraminol increased perfusion pressure without affecting renal vascular resistance. Lankadeva et al. developed a fiber-optic catheter to measure bladder urine PO₂. Urine PO₂ tracks medullary PO₂, and low urine PO₂ predicts acute kidney injury. Adjusting cardiopulmonary bypass to maintain urine PO₂ may help avoid acute kidney injury.

A randomized double-blind, placebo-controlled clinical phase IIa trial on safety, immunomodulatory effects and pharmacokinetics of EA-230 during experimental human endotoxaemia

AIMS

EA-230 is a human chorionic gonadotropin hormone-derived linear tetrapeptide, developed for the treatment of systemic inflammation-related disorders. EA-230 has shown promising immunomodulatory and tissue-protective effects in animals and an excellent safety profile in human phase I studies that we performed. The present phase IIa study follows-up on these results by investigating the safety, efficacy and pharmacokinetics of EA-230 under systemic inflammatory conditions induced by experimental human endotoxaemia.

METHODS

In this randomized, double blind, placebo-controlled phase IIa study, systemic inflammation was induced by intravenous administration of Escherichia coli-derived lipopolysaccharide (LPS). At t = 0 hours, 36 healthy male volunteers received 2 ng/kg LPS, followed by a 2-hour continuous infusion of EA-230 (15, 45 and 90 mg/kg/h, n = 8 per group) or placebo (n = 12).

RESULTS

EA-230 was well tolerated and showed a favourable safety profile. Treatment with the highest dose of EA-230 resulted in a significant attenuation of the LPS-induced increase in plasma levels of inflammatory mediators interleukin (IL)-6, IL-8, IL-1 receptor antagonist, monocyte chemoattractant protein-1, macrophage inflammatory proteins-1α and -1β, and vascular cell adhesion protein-1 (% reduction of 48, 28, 33, 28, 14, 16 and 19 respectively, p < .01), and reduced fever (peak decrease from 1.8 ± 0.1°C to 1.3 ± 0.2°C, P < .05) and symptom scores (peak decrease from 7.4 ± 1.0 to 4.0 ± 1.2 points, P < .05). EA-230 exhibited a very short elimination half-life and a large volume of distribution in the highest dosage group (geometric mean and 95% confidence interval: 0.17 [0.12-0.24] hours and 2.2 [1.3-3.8] L/kg, respectively).

CONCLUSION

Administration of EA-230 is safe and results in attenuation of the systemic inflammatory response in humans.

Goal-directed resuscitation following cardiac surgery reduces acute kidney injury: A quality initiative pre-post analysis

OBJECTIVE

Acute kidney injury (AKI) occurs in 20% of patients following cardiac surgery. To reduce AKI in our institution, we instituted a quality improvement (QI) initiative using a goal-directed volume resuscitation protocol. Our protocol was designed to achieve quantifiable physiologic goals (eg, cardiac index > 2.5 L/min/m², mean arterial pressure > 65 mm Hg) using fluid and vasoactive agents. The objective of this study was to evaluate AKI in the pre- and post-QI eras, hypothesizing that AKI incidence would decrease in the post-QI era.

METHODS

In this observational retrospective cohort study, we identified patients who underwent cardiac operations from July 2011 to July 2015 with a risk score available. Kidney injury was determined using the lowest postoperative GFR within 7 days of surgery and standard Risk, Injury, Failure, Loss of Kidney Function, and End-Stage Kidney Disease (RIFLE) classification criteria. The primary outcome was the rate of AKI, as defined by glomerular filtration rate-based RIFLE classification criteria injury, in the post- versus pre-QI eras.

RESULTS

A total of 1979 patients were included, of whom 725 were in the pre-QI cohort, and 1254 in the post-QI cohort. Overall, rates of RIFLE classification criteria risk, injury and failure were 27.5%, 5.9%, and 3.6%, respectively. RIFLE classification criteria injury saw the largest decrease in the post-QI cohort (8.1% vs 4.6%; P = .001). Multivariable analysis demonstrated a 37% reduction in the odds of AKI in the post-QI cohort (adjusted odds ratio, 0.63; 95% confidence interval, 0.43-0.90).

CONCLUSIONS

A goal-directed volume resuscitation protocol centered on patient fluid responsiveness is associated with significantly reduced risk for AKI after cardiac surgery. Protocol-driven approaches should be employed in intensive care units to improve outcomes.

Association of genetic polymorphisms with acute kidney injury after cardiac surgery in a Southeast Asian population

Introduction

Genetic polymorphisms are important in explaining the wide interpatient variability that exists in the development of acute kidney injury (AKI) post cardiac surgery. We hypothesised that polymorphisms in 4 candidate genes, namely angiotensin-converting enzyme (ACE), apolipoprotein-E (ApoE), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-α) are associated with AKI.

Methods

870 patients who underwent cardiac surgery in Singapore were analysed. All patients who fulfilled stage 1 KDIGO criteria and above were considered to have AKI. This was investigated against various demographic, clinical and genetic factors.

Results

Increased age, history of hypertension, anaemia and renal impairment remained important preoperative risk factors for AKI. Intraoperatively, longer cardiopulmonary bypass (CPB) time and the use of intra-aortic balloon pump (IABP) were shown to be associated with AKI. Among the genetic factors, ACE-D allele was associated with an increased risk of AKI while IL6-572C allele was associated with a decreased risk of AKI.

Conclusion

ACE-D allele was associated with the development of AKI similar to other studies. On the other hand, IL6-572C was shown to have a protective role against the development of AKI, contradictory to studies done in the Caucasian population. This contradictory effect of IL6-572C is a result of a complex interplay between the gene and population specific modulating factors. Our findings further underscored the necessity of taking into account population specific differences when developing prediction models for AKI.

Intraoperative hypotension is a risk factor for postoperative acute kidney injury after femoral neck fracture surgery: a retrospective study

Background

Hip fracture in elderly patients is a serious health concern due to the associated morbidity and mortality. Although acute kidney injury after hip fracture is known to be a significantly poor prognostic factor for morbidity and mortality, the literature regarding the risk factors for acute kidney injury after hip fracture is insufficient. This study aimed to investigate the incidence and associated risk factors for acute kidney injury in patients with femoral neck fracture.

Methods

A total of 248 patients who underwent an operation for femoral neck fracture between January 2011 and January 2015 were retrospectively analyzed. Acute kidney injury was defined according to the Kidney Disease: Improving Global Outcomes guidelines.

Results

The incidence of acute kidney injury was 17.7% (n = 44). Risk factors for acute kidney injury included diabetes mellitus, pre-existing renal disease, preoperative blood urea nitrogen (BUN), preoperative estimated glomerular filtration rate (eGFR), preoperative haemoglobin (Hb) level, type of operation, postoperative creatinine level and intraoperative hypotension (P <  0.05). After controlling for confounding variables, intraoperative hypotension was only the independent risk factor for acute kidney injury (P = 0.012).

Conclusions

Acute kidney injury was found to occur frequently after surgery for femur neck fracture. Surgeons should be aware of acute kidney injury when planning the management of patients with femoral neck fracture and consider that the duration of intraoperative hypotension is a risk factor for acute kidney injury.

Mitochondrial Haplogroup and the Risk of Acute Kidney Injury Following Cardiac Bypass Surgery

Although mitochondrial dysfunction plays a key role in the pathophysiology of acute kidney injury (AKI), the influence of mitochondrial genetic variability in this process remains unclear. We explored the association between the risk of post-cardiac bypass AKI and mitochondrial haplotype - inherited mitochondrial genomic variations of potentially functional significance. Our single-centre study recruited consecutive patients prior to surgery. Exclusions included stage 5 CKD, non-Caucasian race and subsequent off-pump surgery. Haplogroup analysis allowed characterisation of the study population using the common mutations and by phylogenetic supergroup (WXI and HV). Chi-square tests for association allowed the identification of potential predictors of AKI for use in logistic regression analysis. AKI occurred in 12.8% of the study population (n = 881; male 69.6%, non-diabetic 78.5%, median (interquartile range) age 68.0 (61.0-75.0) years). The haplogroup profile comprised H (42.7%), J (12.1%), T (10.9%), U (14.4%) and K (7.6%). Although the regression model was statistically significant (χ² = 95.483, p < 0.0005), neither the phylogenetic supergroups nor any individual haplogroup was a significant contributor. We found no significant association between common European haplogroups and the risk of post-cardiac bypass AKI. However, given the major role of mitochondrial dysfunction in AKI, there is a need to replicate our findings in other cohorts and with other aetiologies of AKI.

The Safety, Tolerability, and Effects on the Systemic Inflammatory Response and Renal Function of the Human Chorionic Gonadotropin Hormone-Derivative EA-230 Following On-Pump Cardiac Surgery (The EASI Study): Protocol for a Randomized, Double-Blind, Placebo-Controlled Phase 2 Study

Background

The cardiac surgery–induced systemic inflammatory response may induce postoperative hemodynamic instability and impairment of renal function. EA-230, a linear tetrapeptide (A-Q-G-V), is derived from the beta chain of the human chorionic gonadotropin pregnancy hormone. It has shown immunomodulatory and renoprotective effects in several animal models of systemic inflammation. In phase 1 and phase 2a studies, these immunomodulatory effects were confirmed during human experimental endotoxemia, and EA-230 was found to have an excellent safety profile.

Objective

The objective of this first in-patient study is to test the safety and tolerability as well as the immunomodulatory and renoprotective effects of EA-230 in a proof-of-principle design in patients with systemic inflammation following on-pump cardiac surgery.

Methods

We describe a prospective, randomized, double-blind, placebo-controlled study in which 180 elective patients undergoing on-pump coronary artery bypass grafting, with or without concomitant valve surgery, are enrolled. Patients will be randomized in a 1:1 ratio and will receive either EA-230 (90 mg/kg/hour) or a placebo. These will be infused at the start of the surgical procedure until the end of the use of the cardiopulmonary bypass. The primary focus of this first-in-patient study will be on safety and tolerability of EA-230. The primary efficacy end point is the modulation of the inflammatory response by EA-230 quantified as the change in interleukin-6 plasma concentrations after surgery. The key secondary end point is the effect of EA-230 on renal function. The study will be conducted in 2 parts to enable an interim safety analysis by an independent data monitoring committee at a sample size of 60. An adaptive design is used to reassess statistical power halfway through the study.

Results

This study has been approved by the independent competent authority and ethics committee and will be conducted in accordance with the ethical principles of the Declaration of Helsinki, guidelines of Good Clinical Practice, and European Directive 2001/20/CE regarding the conduct of clinical trials. Results of this study will be submitted for publication in a peer-reviewed scientific journal. Enrollment of this study commenced in July 2016, and results are expected at the end of 2018.

Conclusions

This adaptive phase 2 clinical study is designed to test the safety and tolerability of EA-230 in patients undergoing cardiac surgery. In addition, efficacy end points focused on the effect of the systemic inflammatory response and renal function are investigated.

Trial Registration

ClinicalTrials.gov NCT03145220; https://clinicaltrials.gov/ct2/show/NCT03145220 (Archived by WebCite at http://www.webcitation.org/74JPh8GNN)

International Registered Report Identifier (IRRID)

DERR1-10.2196/11441

Utility of Novel Cardiorenal Biomarkers in the Prediction and Early Detection of Congestive Kidney Injury Following Cardiac Surgery

Acute Kidney Injury (AKI) in the context of right ventricular failure (RVF) is thought to be largely congestive in nature. This study assessed the utility of biomarkers high sensitivity cardiac troponin T (hs-cTnT), N-Terminal Pro-B-Type Natriuretic Peptide (NT-proBNP), and neutrophil gelatinase-associated lipocalin (NGAL) for prediction and early detection of congestive AKI (c-AKI) following cardiac surgery. This prospective nested case-control study recruited 350 consecutive patients undergoing elective cardiac surgery requiring cardiopulmonary bypass. Cases were patients who developed (1) AKI (2) new or worsening RVF, or (3) c-AKI. Controls were patients free of these complications. Biomarker levels were measured at baseline after anesthesia induction and immediately postoperatively. Patients with c-AKI had increased mean duration of mechanical ventilation and length of stay in hospital and in the intensive care unit (p < 0.01). For prediction of c-AKI, baseline NT-proBNP yielded an area under the curve (AUC) of 0.74 (95% CI, 0.60–0.89). For early detection of c-AKI, postoperative NT-proBNP yielded an AUC of 0.78 (0.66–0.91), postoperative hs-cTnT yielded an AUC of 0.75 (0.58–0.92), and ∆hs-cTnT yielded an AUC of 0.80 (0.64–0.96). The addition of baseline creatinine to ∆hs-cTnT improved the AUC to 0.87 (0.76–0.99), and addition of diabetes improved the AUC to 0.93 (0.88–0.99). Δhs-cTnT alone, or in combination with baseline creatinine or diabetes, detects c-AKI with high accuracy following cardiac surgery.

Differential Signature of Obesity in the Relationship with Acute Kidney Injury and Mortality after Coronary Artery Bypass Grafting

BACKGROUND

Obesity is related to several comorbidities and mortality, but its relationship with acute kidney injury (AKI) and long-term mortality remain undetermined in patients undergoing coronary artery bypass grafting.

METHODS

Data from 3,018 patients (age ≥ 18 years) who underwent coronary artery bypass graft surgery from two tertiary referral centers were retrospectively reviewed between 2004 and 2015. Obesity was defined using the body mass index, according to the World Health Organization's recommendation. The odds and hazard ratios in post-surgical, AKI, and all-cause mortality were calculated after adjustment for multiple covariates. Patients were followed for 90 ± 40.9 months (maximum: 13 years).

RESULTS

Among the cohort, 37.4%, 2.4%, 21.1%, 35.1%, and 4.0% of patients were classified as normal weight, underweight, overweight-at-risk, obese I, and obese II, respectively. Post-surgical AKI developed in 799 patients (26.5%). Patients in the obese groups (overweight-at-risk to obese II) had a higher risk of AKI than did those in the normal-weight group. During the follow-up period, 787 patients (26.1%) died. Underweight patients had a higher risk of mortality than did normal-weight patients, whereas overweight-at-risk, obese I, and obese II patients showed better survival rates.

CONCLUSION

After coronary artery bypass graft surgery, obese patients encountered a high risk of AKI, and underweight patients exhibited a low chance of survival. Awareness of both obese and underweight statuses should be raised in these patients.

The Role of Point-of-Care Ultrasound Monitoring in Cardiac Surgical Patients With Acute Kidney Injury

The approach to the patient with acute kidney injury (AKI) after cardiac surgery involves multiple aspects. These include the rapid recognition of reversible causes, the accurate identification of patients who will progress to severe stages of AKI, and the subsequent management of complications resulting from severe renal dysfunction. Unfortunately, the inherent limitations of physical examination and laboratory parameter results are often responsible for suboptimal clinical management. In this review article, the authors explore how point-of-care ultrasound, including renal and extrarenal ultrasound, can be used to complement all aspects of the care of cardiac surgery patients with AKI, from the initial approach of early AKI to fluid balance management during renal replacement therapy. The current evidence is reviewed, including knowledge gaps and future areas of research.

Resveratrol improves human umbilical cord-derived mesenchymal stem cells repair for cisplatin-induced acute kidney injury

Human umbilical cord-derived mesenchymal stem cells (hucMSCs) are a promising tool for damaged tissues repair, especially for the kidney. However, their efficacy requires improvement. In order to optimize the clinical utility of hucMSCs, we adopted a strategy of treating hucMSCs with 20 μmol/L of resveratrol (Res-hucMSCs), applying it in a cisplatin-induced acute kidney injury model. Interestingly, we found that Res-hucMSCs exhibited a more efficient repairing effect than did hucMSCs. Resveratrol-promoted hucMSCs secreted platelet-derived growth factor-DD (PDGF-DD) into renal tubular cells resulting in downstream phosphorylation of extracellular signal-regulated kinase (ERK), which inhibited renal tubular cells apoptosis. In contrast, PDGF-DD knockdown impaired the renal protection of Res-hucMSCs. In addition, angiogenesis induced by PDGF-DD in endothelial cells was also involved in the renal protection of Res-hucMSCs. The conditioned medium of Res-hucMSCs accelerated proliferation and migration of vascular endothelial cells in vitro and CD31 was in a high-level expression in Res-hucMSCs group in vivo. Nevertheless, the angiogenesis was abrogated when Res-hucMSCs were treated with PDGF-DD siRNA. In conclusion, our findings showed that resveratrol-modified hucMSCs activated ERK pathway in renal tubular cells and promoted angiogenesis in endothelial cells via paracrine PDGF-DD, which could be a novel strategy for enhancing the therapy efficacy of hucMSCs in cisplatin-induced kidney injury.

Impact of preoperative elevated serum creatinine on long-term outcome of patients undergoing aortic repair with Stanford A dissection: a retrospective matched pair analysis

BACKGROUND

The aim of the present study was to determine whether raised preoperative serum creatinine affected the long-term outcome in patients undergoing surgical aortic repair for Stanford A acute aortic dissection (AAD).

METHODS

A total of 240 patients diagnosed with Stanford A AAD underwent surgical repair from January 2006 to April 2015. A propensity score matching was applied, resulting in 73 pairs consisting of one group with normal and one group with preoperative elevated creatinine levels. The cohorts were well balanced for baseline and preoperative clinical characteristics. Both groups were compared regarding their early postoperative variables, as well as estimated survival with up to 9-year follow up. Also, the impact of acute postoperative kidney injury and its severity on long-term survival was analyzed.

RESULTS

The proportion of patients suffering Stanford A AAD with raised creatinine levels was 31.3% ( n = 75). After propensity matching, there were no statistically significant differences regarding demographics, comorbidities, preoperative baseline and clinical characteristics. Postoperatively matched patients with elevated creatinine had longer intensive care unit ( p < 0.001) and total hospital stay ( p = 0.002), prolonged intubation times ( p = 0.014), higher need for hemofiltration ( p < 0.001), higher incidence of temporary neurological disorders ( p = 0.16), infection ( p = 0.005), and trend toward higher incidence of sepsis ( p = 0.097). However, there were no significant differences regarding 30-day mortality (20.5% versus 20.5%, p = 1.000) and long-term overall survival. Further, neither the incidence nor the different stages of acute kidney injury according to the Acute Kidney Injury Network showed any statistically significant differences in terms of long-term survival for both groups [log rank p = 0.636, Breslow (generalized Wilcoxon) p = 0.470, Tarone-Ware p = 0.558].

CONCLUSIONS

Patients with elevated creatinine levels undergoing surgical repair for Stanford A AAD demonstrate higher rate of early postoperative complications. However, 30-day mortality and long-term survival in this patient cohort is not significantly impaired.

Early postoperative change in serum creatinine predicts acute kidney injury after cardiothoracic surgery: a retrospective cohort study

BACKGROUND

Acute kidney injury (AKI) is one of the most severe complications after cardiothoracic surgery (CTS). However, diagnosis of AKI by elevation of serum creatinine (SCr) misses a critical time period for prevention and treatment of AKI. We have observed that patients who develop AKI show a smaller SCr decrease after CTS than those without AKI. Hence, we hypothesized that the magnitude of the SCr change (ΔSCr) measured early after CTS can predict subsequent AKI.

METHODS

We conducted a retrospective analysis from January 2014 to December 2016 to examine the association of ΔSCr with AKI. ΔSCr was calculated as follows: (early postoperative SCr on intensive care unit [ICU] admission) - (preoperative SCr). Established risk factors and demographics were included in the multivariate-adjusted logistic regression model. AKI was defined by SCr criteria of the Kidney Disease: Improving Global Outcomes group.

RESULTS

Among 252 patients who underwent CTS, 69 developed AKI. The median ΔSCr was - 0.14 mg/dL (range - 0.96-0.45). Patients were divided into three groups based on ΔSCr: Group 1, ≤ - 0.2 mg/dL (n = 84); Group 2, > - 0.2 to < - 0.1 mg/dL (n = 76); and Group 3, ≥ - 0.1 mg/dL (n = 92). In the multivariate analysis, Group 3 had a significantly higher incidence of AKI than Group 1 (odds ratio, 7.34; 95% confidence interval 2.55-23.3). ΔSCr was an independent risk factor for AKI (odds ratio for every 0.1-mg/dL increase in ΔSCr, 1.55; 95% confidence interval 1.23-1.97).

CONCLUSIONS

A minor change in the SCr level early after CTS can predict subsequent AKI just after ICU admission.

Early postoperative hypoalbuminemia is a risk factor for postoperative acute kidney injury following hip fracture surgery

INTRODUCTION

Acute kidney injury (AKI) is a common and serious complication after hip fracture surgery in older adults. Hypoalbuminemia is a known independent risk factor for AKI. However, few studies have investigated the relationship between early postoperative hypoalbuminemia and AKI after hip fracture surgery. Therefore, we sought to determine the incidence of and risk factors for AKI and the effects of early postoperative hypoalbuminemia on AKI incidence after surgery for hip fractures, especially intertrochanteric fractures of the proximal femur.

PATIENTS AND METHODS

In this retrospective cohort study from a single center, we reviewed the medical records of 481 consecutive patients (>60 years) who underwent surgery for intertrochanteric fracture of the proximal femur. Multiple logistic regression was performed to identify independent risk factors for AKI. After determining the cut-off value of the minimal level of postoperative serum albumin during the first two postoperative days, we divided the patients into two groups: group 1 included 251 patients whose minimal early postoperative serum albumin level was <2.9 g/dL during the first two postoperative days; and group 2 included 230 patients whose minimal early postoperative serum albumin level was ≥2.9 g/dL. The incidence of AKI was analyzed using inverse probability of treatment weighting (IPTW), propensity score matching (PSM), and propensity score matching weighting (PSMW) analyses.

RESULTS

The incidence of AKI, defined based on the Kidney Disease Improving Global Outcomes criteria, was 11.8% (n = 57). Chronic kidney disease and the minimal early postoperative serum albumin level <2.9 g/dL at any point during the first two postoperative days were independent risk factors for AKI. The IPTW, PSM, and PSMW analyses comparing the incidence of AKI between the two groups revealed that the minimal early postoperative serum albumin level <2.9 g/dL was significantly associated with AKI development (P < 0.001, P = 0.025, and P = 0.011, respectively).

CONCLUSION

The incidence of postoperative AKI was 11.8%. Our findings demonstrate that early postoperative hypoalbuminemia is an independent risk factor for AKI in patients undergoing surgery for intertrochanteric fracture of the proximal femur.

Awareness, incidence and clinical significance of acute kidney injury after non-general anesthesia: A retrospective cohort study

Postoperative acute kidney injury is associated with high mortality and poor prognosis. Additional investigations into the risk factors for this condition and the outcomes of patients who undergo surgeries under non-general anesthesia (GA) are necessary.This retrospective cohort study included data on all surgeries performed in adult patients from January 2006 to December 2015 at a tertiary hospital in Korea. Patients were divided into those undergoing surgeries with non-GA and those undergoing surgeries with GA. We analyzed the nephrological evaluation patterns, the risk factors for acute kidney injury, and prognoses after acute kidney injury by reviewing mortality, progression to end-stage renal disease, and serum creatinine doubling/estimated glomerular filtration rate halving from baseline.Of 74,524 patients, 20,332 underwent surgery with non-GA. These patients had baseline (adjusted odds ratio [OR], .68, 95% confidence interval [CI], .63-.72; P < .01] and follow-up serum creatinine levels (adjusted OR, .34; 95% CI, .33-.36; P < .01) less frequently measured than those undergoing GA. However, the incidence of acute kidney injury did not differ significantly between the 2 groups. Moreover, postoperative acute kidney injury after non-GA surgery showed a worse clinical prognosis which was similar with that of GA operations.Patients undergoing surgeries under non-GA did not receive sufficient evaluation for their risks of acute kidney injury. As an acute kidney injury in non-GA was associated a worse prognosis as in GA surgeries, more clinical attention should be considered.

Losartan does not decrease renal oxygenation and norepinephrine effects in rats after resuscitated hemorrhage

Renin-angiotensin-system blockers are thought to increase the risk of acute kidney injury after surgery and hemorrhage. We found that losartan does not cause renal cortical hypoxia after hemorrhage in rats because of decreased renal vascular resistance, but we did not evaluate resuscitation. We aimed to study losartan's effect on renal cortical and medullary oxygenation, as well as norepinephrine's vasopressor effect in a model of resuscitated hemorrhage. After 7 days of losartan (60 mg·kg^-1·day^-1) or control treatment, male Wistar rats were hemorrhaged 20% of their blood volume and resuscitated with Ringer's acetate. Mean arterial pressure, renal blood flow, and kidney tissue oxygenation were measured at baseline and after resuscitation. Finally, the effect of norepinephrine on mean arterial pressure and renal blood flow was investigated. As expected, losartan lowered mean arterial pressure but not renal blood flow. Losartan did not affect renal oxygen consumption and oxygen tension. Mean arterial pressure and renal blood flow were lower after resuscitated hemorrhage. A smaller increase of renal vascular resistance in the losartan group translated to a smaller decrease in cortical oxygen tension, but no significant difference was seen in medullary oxygen tension, either between groups or after hemorrhage. The effect of norepinephrine on mean arterial pressure and renal blood flow was similar in control- and losartan-treated rats. Losartan does not decrease renal oxygenation after resuscitated hemorrhage because of a smaller increase in renal vascular resistance. Further, losartan does not decrease the efficiency of norepinephrine as a vasopressor, indicating that blood pressure may be managed effectively during losartan treatment.

Effect of Acute Kidney Injury After Percutaneous Mitral Valve Repair on Outcome

Limited data exist on the occurrence of acute kidney injury (AKI) associated with percutaneous mitral valve repair (PMVR). The objectives of the present study were (1) to assess the prevalence of AKI after MitraClip (Abbott Vascular, Santa Clara, California) implantation, (2) to analyze the predictive factors of AKI, and (3) to evaluate the prognostic value of AKI after PMVR with a view to optimizing the management of high-risk patients. A total of 206 patients (serum creatinine [SCr] 1.3 ± 0.6 mg/dl, estimated glomerular filtration rate 55 ± 24 ml/min) who underwent PMVR were included. AKI was defined as an increase in SCr by ≥0.3 mg/dl within 48 hours or an increase in SCr by ≥1.5 times baseline. AKI was assessed during the first 5 days after MitraClip implantation. The incidence of AKI after MitraClip was 18% and none of the patients required dialysis. Age, logistic EuroSCORE, baseline renal function, N-terminal pro-B-type natriuretic peptide levels, serum glycated hemoglobin A1c, serum C-reactive protein, diuretic usage, and elevated right atrial pressure were the risk factors of AKI. Incidence of AKI was associated with poor outcome. Short-term mortality was increased (30-day mortality rate AKI vs no AKI: 18% vs 1%; p <0.001). Likewise, Kaplan-Meier analysis and log-rank test confirmed reduced long-term survival of patients with AKI (1-year all-cause mortality of patients with AKI vs patients with no AKI: 34% vs 13 %; p <0.001). In conclusion, every fifth patient experienced AKI after MitraClip implantation, which was associated with increased short-term mortality and a more than threefold increase in the risk of death 1 year after PMVR.

Preoperative blood morphology and incidence of acute kidney injury after on-pump coronary artery bypass grafting - a single-center preliminary report

Introduction

Acute kidney injury (AKI) after coronary artery bypass grafting (CABG) performed in cardiopulmonary bypass (CPB) may complicate the postoperative course and has a negative impact on outcome. In some cases, postoperative AKI develops in spite of normal baseline creatinine concentration and estimated glomerular filtration rate (eGFR).

Aim

To examine whether there is any association between the preoperative blood morphology and incidence of post-operative AKI.

Material and methods

The study involved 62 consecutive patients with the mean age of 64.0 ±7.4 years who underwent CABG in CPB. Before surgery, blood morphology and biochemistry were analyzed. Patients with eGFR below 60 ml/min/1.73 m² were excluded. After the operation, parameters of renal function were checked systematically. Acute kidney injury was defined according to the Acute Kidney Injury Network (AKIN) classification.

Results

Twenty-one (33.9%) patients presented AKI (group AKI), although in the majority of them (n = 16) it was temporary and medical management was enough to cure AKI. Only in 1 (1.6%) case was renal replacement therapy necessary. In group AKI, patients’ preoperative hemoglobin concentration (8.46 ±0.72 mM/l), red blood cell count (4.51 ±0.39 × 10¹²/l) and hematocrit (0.40 ±0.04) were significantly lower (p < 0.05) than in group C (9.07 ±0.57 mM/l; 4.78 ±0.36 × 10¹²/l; 0.43 ±0.03, respectively). Interestingly, the baseline parameters of renal function were comparable between groups.

Conclusions

Hemoglobin concentration and red blood cell counts close to the lower limit of the normal range may enable identification of patients at risk of AKI early after CABG in CPB among individuals with normal preoperative biochemical parameters of renal function.

Pre-operative anaemia, intra-operative hepcidin concentration and acute kidney injury after cardiac surgery: a retrospective observational study

Acute kidney after cardiac surgery is more common in anaemic patients, whereas haemolysis during cardiopulmonary bypass may lead to iron-induced renal injury. Hepcidin promotes iron sequestration by macrophages: hepcidin concentration is reduced by anaemia and increased by inflammation. We analysed the associations in 525 patients between pre-operative anaemia (haemoglobin < 130 g.l^-1 in men and < 120 g.l^-1 in women), intra-operative hepcidin concentration and acute kidney injury (dialysis or > 26.4 μmol.l^-1 or > 50% creatinine increase during the first two days after cardiac surgery. Rates of pre-operative anaemia and postoperative kidney injury were 109/525 (21%) and 36/525 (7%), respectively. The median (IQR [range]) intra-operative hepcidin concentration was 20 (10-33 [0-125]) μg.l^-1 and was lower in anaemic patients than those who were not: 15 (4-28 [0-125]) μg.l^-1 vs. 21 (12-33 [0-125]) μg.l^-1 , respectively, p = 0.002. Four variables were independently associated with postoperative kidney injury, for which the beta-coefficients (SE) were: minutes on cardiopulmonary bypass, 0.016 (0.004), p < 0.001; intra-operative hepcidin concentration, 0.032 (0.008), p < 0.001; pre-operative anaemia, 1.97 (0.56), p < 0.001; and Cleveland clinic risk score, 0.88 (0.35), p = 0.005. Contrary to generally increased rates of kidney injury in patients with higher hepcidin concentrations, rates of kidney injury in anaemic patients were lower in patients with higher hepcidin concentrations, beta-coefficient (SE) -0.037 (0.01), p = 0.007. In cardiac surgical patients the rate of postoperative acute kidney injury predicted by the Cleveland risk score might be adjusted for pre-operative anaemia and intra-operative cardiopulmonary bypass time and hepcidin concentration. Pre-operative correction of anaemia, reduction in intra-operative bypass time and modification of iron homeostasis and hepcidin concentration might reduce acute kidney injury.

Role of statins in preventing cardiac surgery-associated acute kidney injury: an updated meta-analysis of randomized controlled trials

Background

The prevention of cardiac surgery-associated acute kidney injury (CSA-AKI) by statins remains controversial. Therefore, the present meta-analysis including randomized controlled trials (RCTs) was performed to assess the effect of perioperative statin on CSA-AKI.

Methods

Two reviewers independently searched for RCTs about perioperative statin for prevention of CSA-AKI. The primary endpoint was CSA-AKI. Relative risk was calculated between statin and placebo for preventing CSA-AKI using the random-effect model or fixed-effect model according to different heterogeneity.

Results

Eight RCTs met inclusion criteria, including five studies with atorvastatin, two with rosuvastatin, and one with simvastatin. There were 1,603 patients receiving statin treatment and 1,601 with placebo. Perioperative statin therapy did not reduce the incidence of CSA-AKI (relative risk =1.17, 95% CI: 0.98–1.39, p=0.076). Furthermore, perioperative statin increased the risk of CSA-AKI in the subgroup analysis with clear definition of CSA-AKI and those with JADAD score >3. Perioperative rosuvastatin produced slightly significantly higher risk of AKI than atorvastatin therapy (p=0.070). Statin intervention both pre and post surgery slightly increased the risk of CSA-AKI versus preoperative statin therapy alone (p=0.040).

Conclusions

Perioperative statin therapy might increase the risk of CSA-AKI after cardiac surgery.

Epidemiological characteristics of and risk factors for patients with postoperative acute kidney injury: a multicenter prospective study in 30 Chinese intensive care units

BACKGROUND

Although there were studies to investigate the risk factors for acute kidney injury (AKI) after surgery, most of them focused on one specific type of surgeries. The risk factors for postoperative AKI in patients undergoing all surgeries in intensive care units (ICU) have not been reported.

METHODS

Data from 1731 patients undergoing surgery in 30 ICUs of 28 tertiary hospitals in Beijing from March to August 2012 were prospectively collected. AKI was defined and staged by the KDIGO criteria. Multivariate logistic regression analysis was performed to assess independent risk factors for postoperative AKI.

RESULTS

Postoperative AKI occurred in 44.8% of patients (stage 1 54.8%; stage 2 21.9%, stage 3 23.3%). Cardiovascular surgery was identified as an independent factor for postoperative AKI as well as emergency surgery [odds ratio (OR) 1.403], nephrotoxic drugs (OR 1.303), APACHE II score (OR 1.055), SOFA score (OR 1.115), duration for positive fluid balance (OR 1.165), use of diuretics (OR 2.293), sepsis (OR 1.501), and CKD (OR 4.517). AKI stage 3 versus stages 1-2 was associated with higher mortality in ICU, hospital, and 28-day follow-up after cardiovascular, abdominal, limb, and chest surgeries, while this was not observed after neurosurgery or other surgeries.

CONCLUSION

Risk factors for AKI in ICU patients after different types of surgery were identified. This might be the first step to reduce the high incidence of AKI after surgery. The presence of AKI in ICU patients was associated with higher mortality after most types of surgery, but not after neurosurgery.

TRIAL REGISTRATION

ChiCTR-ONC-11001875.

Comparative Efficacy of Drugs for Preventing Acute Kidney Injury after Cardiac Surgery: A Network Meta-Analysis

BACKGROUND

Acute kidney injury (AKI) occurs frequently after cardiac surgery and has been associated with increased hospital length of stay, mortality, and costs.

OBJECTIVE

We aimed to evaluate the efficacy of pharmacologic strategies for preventing AKI after cardiac surgery.

METHODS

We searched PubMed, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL) up to 6 May 2017 and the reference lists of relevant articles about trials. The outcome was the occurrence of AKI. This is the first network meta-analysis of the different prevention strategies using Bayesian methodology.

RESULTS

The study included 63 articles with 19,520 participants and evaluated the effect of ten pharmacologic strategies to prevent AKI in patients undergoing cardiac surgery. Compared with placebo, the odds ratio (OR) for the occurrence of AKI was 0.24 [95% confidence interval (CI) 0.16-0.34] with natriuretic peptide, 0.33 (95% CI 0.14-0.70) with fenoldopam, 0.54 (95% CI 0.31-0.84) with dexmedetomidine, 0.56 (95% CI 0.29-0.95) with low-dose erythropoietin, 0.63 (95% CI 0.43-0.88) with levosimendan, 0.76 (95% CI 0.52-1.10) with steroids, 0.83 (95% CI 0.48-1.40) with high-dose erythropoietin, 0.85 (95% CI 0.64-1.14) with N-acetylcysteine, 0.96 (95% CI 0.69-1.29) with sodium bicarbonate, and 1.05 (95% CI 0.70-1.41) with statins. The surface under the cumulative ranking curve probabilities indicated that natriuretic peptide was the best treatment therapy and that fenoldopam ranked second.

CONCLUSIONS

Natriuretic peptide is probably the preferred pharmacologic strategy to prevent AKI in adult patients undergoing cardiac surgery, especially in those at high risk of AKI.

Development of biomarker combinations for postoperative acute kidney injury via Bayesian model selection in a multicenter cohort study

Background

Acute kidney injury (AKI) is a frequent complication of cardiac surgery. We sought prognostic combinations of postoperative biomarkers measured within 6 h of surgery, potentially in combination with cardiopulmonary bypass time (to account for the degree of insult to the kidney). We used data from a large cohort of patients and adapted methods for developing biomarker combinations to account for the multicenter design of the study.

Methods

The primary endpoint was sustained mild AKI, defined as an increase of 50% or more in serum creatinine over preoperative levels lasting at least 2 days during the hospital stay. Severe AKI (secondary endpoint) was defined as a serum creatinine increase of 100% or more or dialysis during hospitalization. Data were from a cohort of 1219 adults undergoing cardiac surgery at 6 medical centers; among these, 117 developed sustained mild AKI and 60 developed severe AKI. We considered cardiopulmonary bypass time and 22 biomarkers as candidate predictors. We adapted Bayesian model averaging methods to develop center-adjusted combinations for sustained mild AKI by (1) maximizing the posterior model probability and (2) retaining predictors with posterior variable probabilities above 0.5. We used resampling-based methods to avoid optimistic bias in evaluating the biomarker combinations.

Results

The maximum posterior model probability combination included plasma N-terminal-pro-B-type natriuretic peptide, plasma heart-type fatty acid binding protein, and change in serum creatinine from before to 0-6 h after surgery; the median probability combination additionally included plasma interleukin-6. The center-adjusted, optimism-corrected AUCs for these combinations were 0.80 (95% CI: 0.78, 0.87) and 0.81 (0.78, 0.87), respectively, for predicting sustained mild AKI, and 0.81 (0.76, 0.90) and 0.83 (0.76, 0.90), respectively, for predicting severe AKI. For these data, the Bayesian model averaging methods yielded combinations with prognostic capacity comparable to that achieved by standard frequentist methods but with more parsimonious models.

Conclusions

Pending external validation, the identified combinations could be used to identify individuals at high risk of AKI immediately after cardiac surgery and could facilitate clinical trials of renoprotective agents.

Risk of Acute Kidney Injury in Patients Randomized to a Restrictive Versus Liberal Approach to Red Blood Cell Transfusion in Cardiac Surgery: A Substudy Protocol of the Transfusion Requirements in Cardiac Surgery III Noninferiority Trial

Background:

When safe to do so, avoiding blood transfusions in cardiac surgery can avoid the risk of transfusion-related infections and other complications while protecting a scarce resource and reducing costs. This protocol describes a kidney substudy of the Transfusion Requirements in Cardiac Surgery III (TRICS-III) trial, a multinational noninferiority randomized controlled trial to determine whether the risk of major clinical outcomes in patients undergoing planned cardiac surgery with cardiopulmonary bypass is no greater with a restrictive versus liberal approach to red blood cell transfusion.

Objective:

The objective of this substudy is to determine whether the risk of acute kidney injury is no greater with a restrictive versus liberal approach to red blood cell transfusion, and whether this holds true in patients with and without preexisting chronic kidney disease.

Design and Setting:

Multinational noninferiority randomized controlled trial conducted in 73 centers in 19 countries (2014-2017).

Patients:

Patients (~4800) undergoing planned cardiac surgery with cardiopulmonary bypass.

Measurements:

The primary outcome of this substudy is perioperative acute kidney injury, defined as an acute rise in serum creatinine from the preoperative value (obtained in the 30-day period before surgery), where an acute rise is defined as ≥26.5 μmol/L in the first 48 hours after surgery or ≥50% in the first 7 days after surgery.

Methods:

We will report the absolute risk difference in acute kidney injury and the 95% confidence interval. We will repeat the primary analysis using alternative definitions of acute kidney injury, including staging definitions, and will examine effect modification by preexisting chronic kidney disease (defined as a preoperative estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m²).

Limitations:

It is not possible to blind patients or providers to the intervention; however, objective measures will be used to assess outcomes, and outcome assessors will be blinded to the intervention assignment.

Results:

Substudy results will be reported by the year 2018.

Conclusions:

This substudy will provide generalizable estimates of the risk of acute kidney injury of a restrictive versus liberal approach to red blood cell transfusion in the presence of anemia during cardiac surgery done with cardiopulmonary bypass.

Trial Registration:

www.clinicaltrials.gov; clinical trial registration number NCT 02042898.