Prevention and treatment of acute kidney injury in patients undergoing cardiac surgery: a systematic review

Evaluation of acute kidney injury with oxidative stress biomarkers and Renal Resistive Index after cardiac surgery

BACKGROUND

We investigated whether cardiopulmonary bypass (CPB) related oxidative stress mediated glycocalyx degradation can cause an increase in renal resistive index (RRI) or postoperative AKI. Additionally, to evaluate whether RRI and early postoperative serum cystatin C levels could improve the prediction sensitivity of acute kidney injury (AKI).

METHODS

Forty-two patients undergoing cardiac surgery were included in this prospective observational study. RRI was measured pre-operatively and in the cardiac intensive care unit. Blood samples were collected for analyzing of cellular injury biomarkers at preoperative and postoperative second hours. We determined areas under the receiver operating characteristic curve (AUC) and odds ratios for postoperative biomarkers and RRI to predict AKI.

RESULTS

While postoperative cystatin C level (AUC: 0.902, 95% CI = 0.79-1.00, p < .001) and RRI (AUC: 0.748, 95% CI = 0.56-0.93, p = .023) have diagnostic and predictive value in the prediction of AKI, we could not identify any relation between products of oxidative stress and the glycocalyx degradation and AKI.

CONCLUSION

These data suggest that CPB leads to structural and oxidative changes at the protein level and the integrity of glycocalyx is disturbing, but these changes are not specific to kidney injury. Our data suggest that serum cystatin C level and RRI could be used as an early biomarker for postoperative AKI after cardiac surgery.

Systematic Review and Meta-Analysis of Preventative Strategies for Acute Kidney Injury in Patients Undergoing Abdominal Aortic Aneurysm Repair

BACKGOUND

To assess the effect of various preventative interventions for reducing the incidence of postoperative acute kidney injury (AKI) in patients undergoing elective abdominal aortic aneurysm (AAA) repair.

METHODS

We included randomized controlled trials of 10 patients or more which tested a preventative intervention versus standard therapy or placebo in patients undergoing elective AAA repair using the open or endovascular approach. Studies including mixed patient populations such as those with aortic occlusive disease, thoracoabdominal aneurysms or ruptured aneurysms were ineligible for review. We searched Medline (1966-2019), EMBASE (1947-2019), CINAHL (1961-2019), Web of Science (1945-2019), Scopus (1966-2019), and The Cochrane Library (1996-2019) for trials available as published manuscripts in English. Study quality was assessed using the Cochrane Collaboration risk of bias tool. Where possible we pooled the results of similar interventions using random effects meta-analysis.

RESULTS

We included 17 trials involving 1443 participants. Most trials were small, single-center studies, with varying definitions of AKI and a high or moderate risk of bias. The preventative strategies with possible protective effects were mannitol, a composite of antioxidant supplements, an open extraperitoneal approach, and human atrial natriuretic peptide (hANP). Curcumin, methylprednisolone, carbon dioxide contrast medium, hemodynamic monitoring and N-acetylcysteine were found to be ineffective. Six trials with a total of 355 participants reported on remote ischemic preconditioning (RIPC) and our meta-analysis showed no statistically significant difference between RIPC and standard treatment (OR 1.20, 95% CI 0.37, 3.89); although the results should be interpreted with caution due to considerable statistical heterogeneity (I² = 70%). None of the interventions studied significantly reduced receipt of renal replacement therapy (RRT).

CONCLUSIONS

Interventions that have shown some potential to reduce AKI after AAA repair include mannitol, a composite of antioxidant supplements, an open extraperitoneal approach and hANP. These conclusions are limited by the small size, high risk of bias and inconsistency of the included trials. Large, high quality, multi-center randomized trials will help determine which interventions are effective in reducing the incidence of postoperative AKI among patients undergoing elective AAA repair.

High-Sensitivity Cardiac Troponin, Natriuretic Peptide, and Long-Term Risk of Acute Kidney Injury: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Cardiac markers such as high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-B natriuretic peptide (NTproBNP) are predictors of developing acute kidney injury (AKI) during hospitalization for surgery or revascularization. However, their associations with the long-term risk of AKI in the general population are uncharacterized.

METHODS

We conducted a prospective cohort study in 10 669 participants of the Atherosclerosis Risk in Communities Study (visit 4, 1996-1998, mean age, 63 years, 56% female, 22% black race) to examine the association of plasma concentrations of hs-cTnT and NTproBNP with the incident hospitalization with AKI. We used multivariable Cox regression analysis to estimate hazard ratios (HRs).

RESULTS

During follow-up, 1907 participants had an incident hospitalization with AKI. Participants with higher concentrations of hs-cTnT had a higher risk of hospitalization with AKI in a graded fashion (adjusted HR, 1.88 [95%CI , 1.59-2.21] for ≥14 ng/L, 1.36 [1.18-1.57] for 9-13 ng/L, and 1.16 [1.03-1.30] for 5-8 ng/L compared to <5 ng/L). The graded association was also observed for NTproBNP (HR, 2.27 [1.93-2.68] for ≥272.7 pg/mL, 1.67 [1.45-1.93] for 142.4-272.6 pg/mL, and 1.31 [1.17-1.47] for 64.0-142.3 pg/mL compared to <64.0 pg/mL). The addition of hs-cTnT and NTproBNP to a model with established predictors significantly improved 10-year risk prediction for hospitalization with AKI (Δc-statistic, 0.015 [95%CI, 0.006-0.024]).

CONCLUSIONS

In middle-aged to older black and white adults in the community, higher concentrations of hs-cTnT and NTproBNP were robustly associated with an increased risk of hospitalization with AKI. These results suggest the usefulness of hs-cTnT and NT-proBNP to identify people at risk of AKI in the general population.

Effect of anti-C5 antibody on recuperation from ischemia/reperfusion-induced acute kidney injury

Aim: The complement system is activated in acute kidney injury (AKI). Anti-C5 antibody targets the common terminal portion of the complement cascade that generate the terminal complex C5b-9 and has a renal-protective effect in paroxysmal nocturnal hemoglobinuria. However, the anti-C5 antibody’s role in ischemia/reperfusion (I/R)-induced AKI has not been fully investigated. We therefore evaluated its effect on the pathophysiological cascade of I/R-induced AKI.

Methods: Sprague–Dawley rats underwent unilateral right kidney nephrectomies with simultaneous clamping of the contralateral hilum for 60 min (ischemia), followed by reperfusion. In addition to a placebo, two treatment groups received either high or low doses of anti-C5 monoclonal antibody. After 48 h, the rats were euthanized, blood was drawn to evaluate systemic inflammation and to estimate glomerular filtration rate (GFR). The remaining kidney was removed for pathological evaluation and intra-renal complement activation.

Results: I/R induced significant intra-renal complement activation and systemic inflammation compared with unilateral nephrectomy group. The anti-C5 antibody ameliorated the intra-renal complement activation (intra-renal C3 and C6), reduced systemic inflammation (C-reactive protein, and systemic C3), decreased intra-renal acute tubular necrosis damage and improved GFR (seen by the sensitive marker, serum cystatin C; 1.63 mg/L (I/R + placebo), 1.36 mg/L (I/R + low dose) and 1.21 mg/L (I/R + high dose), p = .08 and .03 compared with I/R + placebo).

Conclusion: In I/R-induced AKI, the monoclonal anti-C5 complement factor ameliorates intra renal complement activation, decreases local and systemic inflammation and may improve GFR.

Acute kidney injury after pediatric cardiac surgery

Acute kidney injury (AKI) is a common complication of pediatric cardiac surgery and is associated with increased morbidity and mortality. Literature of AKI after pediatric cardiac surgery is comprehensively reviewed in terms of incidence, risk factors, biomarkers, treatment and prognosis. The novel RIFLE (pediatric RIFLE for pediatrics), Acute Kidney Injury Network (AKIN) and Kidney Disease Improving Global Outcomes (KDIGO) criteria have brought about unified diagnostic standards and comparable results for AKI after cardiac surgery. Numerous risk factors, either renal or extrarenal, can be responsible for the development of AKI after cardiac surgery, with low cardiac output syndrome being the most pronounced predictor. Early fluid overload is also crucial for the occurrence of AKI and prognosis in pediatric patients. Three sensitive biomarkers, neutrophil gelatinase-associated lipocalin, cystatin C (CysC) and liver fatty acid-binding protein, are regarded as the earliest (increase at 2-4 h), and another two, kidney injury molecule-1 and interleukin-18 represent the intermediate respondents (increase at 6-12 h after surgery). To ameliorate the cardiopulmonary bypass techniques, improve renal perfusion and eradicate the causative risk factors are imperative for the prevention of AKI in pediatric patients. The early and intermediate biomarkers are helpful for an early judgment of occurrence of postoperative AKI. Improved survival has been achieved by prevention, renal support and modifications of hemofiltration techniques. Further development is anticipated in small children.

Cardiopulmonary Bypass and AKI: AKI Is Bad, So Let's Get Beyond the Diagnosis

It is now well-established that AKI is a serious and common complication following cardiopulmonary bypass (CPB) in both children and adults, adverse outcomes may occur in the short term as well as long term, with higher incidence of chronic kidney disease, increased healthcare utilization and higher frequency of cardiovascular events in patients who develop post-CPB AKI. Despite the advances in our understanding of the pathogenesis of the disease and the improvement in diagnostic tools, our therapeutic options have remained suboptimal. There are multiple challenges in designing a clinical therapeutic AKI trial, including a multi-factorial etiology, difficulties with accurate diagnosis of AKI, achievement of adequate study power, and determination of appropriate outcomes. We are often left with "supportive" care. Studies have shown some benefit to AKI bundles, but adherence to bundle guidelines may be suboptimal. Current best practices should include maintenance of adequate renal perfusion pressure and avoidance of fluid overload, with consideration of early renal replacement therapy. Finally, multi-center trials of AKI therapies are crucial to finding treatment for this devastating complication of CPB.

Preoperative Short-Term Calorie Restriction for Prevention of Acute Kidney Injury After Cardiac Surgery: A Randomized, Controlled, Open-Label, Pilot Trial

BACKGROUND

Acute kidney injury is a frequent complication after cardiac surgery and is associated with adverse outcomes. Although short-term calorie restriction (CR) has proven protective in rodent models of acute kidney injury, similar effects have not yet been demonstrated in humans.

METHODS AND RESULTS

CR_KCH (Effect of a Preoperative Calorie Restriction on Renal Function After Cardiac Surgery) is a randomized controlled trial in patients scheduled for cardiac surgery. Patients were randomly assigned to receive either a formula diet containing 60% of the daily energy requirement (CR group) or ad libitum food (control group) for 7 days before surgery. In total, 82 patients were enrolled between April 16, 2012, and February 5, 2015. There was no between-group difference in the primary end point of median serum creatinine increment after 24 hours (control group: 0.0 mg/dL [-0.1 - (+0.2) mg/dL]; CR group: 0.0 mg/dL [-0.2 - (+0.2) mg/dL]; P=0.39). CR prevented a rise in median creatinine at 48 hours (control group: +0.1 mg/dL [0.0 - 0.3 mg/dL]; CR group: -0.1 mg/dL [-0.2 - (+0.1) mg/dL]; P=0.03), with most pronounced effects observed in male patients and patients with a body mass index >25. This benefit persisted until discharge: Median creatinine decreased by 0.1 mg/dL (-0.2 - 0.0 mg/dL) in the CR group, whereas it increased by 0.1 mg/dL (0.0 - 0.3 mg/dL; P=0.0006) in the control group. Incidence of acute kidney injury was reduced by 5.8% (41.7% in the CR group compared with 47.5% in the control group). Safety-related events did not differ between groups.

CONCLUSIONS

Despite disappointing results with respect to creatinine rise within the first 24 hours, the benefits observed at later time points and the subgroup analyses suggest the protective potential of short-term CR in patients at risk for acute kidney injury, warranting further investigation.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01534364.

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.

Incidence, risk factors, and outcomes of acute kidney injury in adults undergoing surgery for congenital heart disease

BACKGROUND

Acute kidney injury after cardiac surgery is a frequent and serious complication among children with congenital heart disease (CHD) and adults with acquired heart disease; however, the significance of kidney injury in adults after congenital heart surgery is unknown. The primary objective of this study was to determine the incidence of acute kidney injury after surgery for adult CHD. Secondary objectives included determination of risk factors and associations with clinical outcomes.

METHODS

This single-centre, retrospective cohort study was performed in a quaternary cardiovascular ICU in a paediatric hospital including all consecutive patients ⩾18 years between 2010 and 2013.

RESULTS

Data from 118 patients with a median age of 29 years undergoing cardiac surgery were analysed. Using Kidney Disease: Improving Global Outcome creatinine criteria, 36% of patients developed kidney injury, with 5% being moderate to severe (stage 2/3). Among higher-complexity surgeries, incidence was 59%. Age ⩾35 years, preoperative left ventricular dysfunction, preoperative arrhythmia, longer bypass time, higher Risk Adjustment for Congenital Heart Surgery-1 category, and perioperative vancomycin use were significant risk factors for kidney injury development. In multivariable analysis, age ⩾35 years and vancomycin use were significant predictors. Those with kidney injury were more likely to have prolonged duration of mechanical ventilation and cardiovascular ICU stay in the univariable regression analysis.

CONCLUSIONS

We demonstrated that acute kidney injury is a frequent complication in adults after surgery for CHD and is associated with poor outcomes. Risk factors for development were identified but largely not modifiable. Further investigation within this cohort is necessary to better understand the problem of kidney injury.

Urinary Matrix Metalloproteinase-7 Predicts Severe AKI and Poor Outcomes after Cardiac Surgery

Urinary matrix metalloproteinase-7 (uMMP-7) levels consistently reflect the activity of intrarenal Wnt/β-catenin, which is activated in AKI models. To test the hypothesis that uMMP-7 is a predictor for severe AKI in patients after cardiac surgery, we performed a prospective, multicenter, two-stage cohort study in 721 patients undergoing cardiac surgery. In stage 1, we enrolled 323 children from three academic medical centers. In stage 2, we enrolled 398 adults at six centers. We analyzed levels of uMMP-7 and other injury biomarkers during the perioperative period. Severe AKI was defined as Kidney Disease Improving Global Outcomes stage 2 or 3. uMMP-7 level peaked within 6 hours after surgery in patients who subsequently developed severe AKI. After multivariate adjustment, the highest quintile of postoperative uMMP-7 level, compared with the lowest quintile, associated with 17-fold (in adults) and 36-fold (in children) higher odds of severe AKI. Elevated uMMP-7 level associated with increased risk of composite events (severe AKI, acute dialysis, and in-hospital death) and longer stay in the intensive care unit and hospital. For predicting severe AKI, uMMP-7 had an area under the receiver operating characteristic curve of 0.81 (in children) and 0.76 (in adults), outperforming urinary IL-18, angiotensinogen, neutrophil gelatinase-associated lipocalin, albumin-to-creatinine ratio, and tissue inhibitor of metalloproteinase-2·IGF-binding protein-7 and the clinical model. uMMP-7 significantly improved risk reclassification over the clinical model alone, as measured by net reclassification improvement and integrated discrimination improvement. In conclusion, uMMP-7 is a promising predictor for severe AKI and poor in-hospital outcomes in patients after cardiac surgery.

AKIpredictor, an online prognostic calculator for acute kidney injury in adult critically ill patients: development, validation and comparison to serum neutrophil gelatinase-associated lipocalin

PURPOSE

Early diagnosis of acute kidney injury (AKI) remains a major challenge. We developed and validated AKI prediction models in adult ICU patients and made these models available via an online prognostic calculator. We compared predictive performance against serum neutrophil gelatinase-associated lipocalin (NGAL) levels at ICU admission.

METHODS

Analysis of the large multicenter EPaNIC database. Model development (n = 2123) and validation (n = 2367) were based on clinical information available (1) before and (2) upon ICU admission, (3) after 1 day in ICU and (4) including additional monitoring data from the first 24 h. The primary outcome was a comparison of the predictive performance between models and NGAL for the development of any AKI (AKI-123) and AKI stages 2 or 3 (AKI-23) during the first week of ICU stay.

RESULTS

Validation cohort prevalence was 29% for AKI-123 and 15% for AKI-23. The AKI-123 model before ICU admission included age, baseline serum creatinine, diabetes and type of admission (medical/surgical, emergency/planned) and had an AUC of 0.75 (95% CI 0.75-0.75). The AKI-23 model additionally included height and weight (AUC 0.77 (95% CI 0.77-0.77)). Performance consistently improved with progressive data availability to AUCs of 0.82 (95% CI 0.82-0.82) for AKI-123 and 0.84 (95% CI 0.83-0.84) for AKI-23 after 24 h. NGAL was less discriminant with AUCs of 0.74 (95% CI 0.74-0.74) for AKI-123 and 0.79 (95% CI 0.79-0.79) for AKI-23.

CONCLUSIONS

AKI can be predicted early with models that only use routinely collected clinical information and outperform NGAL measured at ICU admission. The AKI-123 models are available at http://akipredictor.com/ . Trial registration Clinical Trials.gov NCT00512122.

Efficacy of N-Acetylcysteine in Preventing Acute Kidney Injury After Cardiac Surgery: A Meta-Analysis Study

PURPOSE

To evaluate whether perioperative N-acetylcysteine (NAC) administration reduces the risk of cardiac surgery associated acute kidney injury (CSA-AKI).

MATERIALS AND METHODS

A systematic literature review (Medline, PubMed, Cochrane, Biomedical central, Google Scholar) identified 10 studies (1391 patients; 695 NAC and 696 placebo) that compared the efficacy and adverse effects of perioperative NAC administration for CSA-AKI prevention in adults undergoing elective cardiac surgery. Meta-analysis was performed using Comprehensive Meta-Analysis statistical software.

RESULTS

Patients in the NAC-treated and placebo groups had similar rate of CSA-AKI occurrence, change in creatinine levels, as well as the in-hospital mortality rate (RR = 0.841, 95% CI = 0.691 to 1.023, p = 0.083; pooled difference in means = -0.328, 95% CI = -0.712 to 0.056, p = 0.094; RR = 0.741, 95% CI = 0.388 to 1.418, p = 0.366, respectively).

CONCLUSIONS

Our study does not support perioperative NAC administration as a mean to reduce the risk of CSA-AKI.

[Acute kidney injury after pediatric cardiac surgery: risk factors and outcomes. Proposal for a predictive model]

OBJECTIVES

To characterize the epidemiology and risk factors for acute kidney injury (AKI) after pediatric cardiac surgery in our center, to determine its association with poor short-term outcomes, and to develop a logistic regression model that will predict the risk of AKI for the study population.

METHODS

This single-center, retrospective study included consecutive pediatric patients with congenital heart disease who underwent cardiac surgery between January 2010 and December 2012. Exclusion criteria were a history of renal disease, dialysis or renal transplantation.

RESULTS

Of the 325 patients included, median age three years (1 day-18 years), AKI occurred in 40 (12.3%) on the first postoperative day. Overall mortality was 13 (4%), nine of whom were in the AKI group. AKI was significantly associated with length of intensive care unit stay, length of mechanical ventilation and in-hospital death (p<0.01). Patients' age and postoperative serum creatinine, blood urea nitrogen and lactate levels were included in the logistic regression model as predictor variables. The model accurately predicted AKI in this population, with a maximum combined sensitivity of 82.1% and specificity of 75.4%.

CONCLUSIONS

AKI is common and is associated with poor short-term outcomes in this setting. Younger age and higher postoperative serum creatinine, blood urea nitrogen and lactate levels were powerful predictors of renal injury in this population. The proposed model could be a useful tool for risk stratification of these patients.

Aspirin in the perioperative period: a review of the recent literature

PURPOSE OF REVIEW

The indications for aspirin (ASA) for both primary and secondary prevention of thrombotic events continue to evolve. We review some of these indications and the recent literature regarding the perioperative administration of ASA.

RECENT FINDINGS

ASA for primary prevention of cardiac ischemia, stroke, cancer, and death remains controversial. When used for primary prevention, ASA may be safely discontinued perioperatively. Patients with coronary or carotid artery stents should continue to receive ASA perioperatively. For patients with ischemic heart disease currently receiving ASA for secondary prevention of cardiac ischemia and stroke undergoing general surgery, orthopedic surgery, ophthalmological surgery, cardiovascular surgery, major vascular surgery, or a urological procedure, continuation of ASA is probably well tolerated, but further study is required. There is no indication to initiate ASA perioperatively in patients with stable ischemic heart disease as the risks outweigh the benefits. Until further data become available, decisions regarding the perioperative continuation of ASA should be made on a case-by-case risk-benefit analysis.

SUMMARY

The continuation or discontinuation of ASA perioperatively remains a complicated issue. Further, well designed trials are needed for additional clarification.

Prevention and Treatment of Cardiac Surgery Associated Acute Kidney Injury

AIM OF REVIEW

Acute kidney injury (AKI) after cardiac surgery is a relatively common postoperative complication and is independently related to increased mortality and morbidity.

METHOD

In this review, we will focus on risk factors of developing AKI, early detection by biomarkers and preventive strategies for AKI after adult cardiac surgery.

RECENT FINDINGS

Many perioperative factors affect renal function and acute AKI following cardiac surgery. Novel biomarkers of kidney injury such as neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), cystatin C (CysC), have the potential to facilitate the early diagnosis of cardiac surgery associated AKI (CSA-AKI). Pharmacological interventions have been inconsistent to their efficacy, and to date, there is no compelling pharmacologic agent known to reduce the risk of AKI or treat established AKI.

SUMMARY

Preventive strategies of AKI focus on optimal perioperative management.

Validating a scoring tool to predict acute kidney injury (AKI) following cardiac surgery

Background

Acute kidney injury (AKI) after cardiac surgery is associated with an increased risk of mortality. Preoperative risk scores can identify patients at risk for AKI and facilitate preventive strategies. Currently, validated risk scores are used to predict AKI requiring dialysis (AKI-D); less is known about whether these tools predict less severe forms of AKI.

Objective

To evaluate the Cleveland Clinic scoring tool in predicting both AKI-D and less severe stages of AKI in patients after cardiac surgery in a Canadian tertiary care center.

Design

Retrospective case–control study.

Setting

Regina Qu’Appelle Health Region (RQHR) from 2007 to 2011.

Patients

Patients who underwent cardiac surgery and developed postoperative kidney injury (n = 2316).

Measurements

Data on risk factors for AKI and outcomes of cardiac surgery were collected from a retrospective chart review.

Methods

The primary outcome was AKI, defined as Stage 1 (increase in serum creatinine 1.5-1.9 X baseline within 5 days), Stage 2 (increase 2.0-2.9 X baseline), or Stage 3 (increase 3.0 X baseline or more OR initiation of dialysis during hospital stay). We assessed the performance of a modified version of the Cleveland Clinic tool using receiver operating curve analyses.

Results

The incidence of AKI was 6.1% (Stage 1), 2.6% (Stage 2), and 5.8% (Stage 3). The area under the curve (AUC) for the Cleveland score was 0.61 (95% CI: 0.56 to 0.65; p < 0.001) for Stage 1, 0.61 (95% CI: 0.54 to 0.68; p < 0.01) for Stage 2, and 0.78 (95% CI: 0.74 to 0.82; p < 0.001) for Stage 3. Greater level of risk on the Cleveland tool was associated with a higher risk of Stage 3 AKI.

Limitations

Lack of prospective validation.

Conclusions

The modified Cleveland Clinic tool was valid in identifying patients with severe stages of AKI but did not have strong discrimination for early AKI stages.

Electronic supplementary material

The online version of this article (doi:10.1186/s40697-015-0037-x) contains supplementary material, which is available to authorized users.

Fluid management in the cardiothoracic intensive care unit: diuresis--diuretics and hemofiltration

PURPOSE OF REVIEW

The present review discusses the current concepts of fluid management in cardiothoracic surgery, and its clinical implications with special reference to organ-related complications and their prevention.

RECENT FINDINGS

Current strategies in fluid management for cardiothoracic patients, various fluid formulation, and the preventive strategies for minimizing fluid-related complications are described, with particular reference to new discoveries and controversies that have arisen from recent literature.

SUMMARY

The optimal fluid management in cardiothoracic patients has not been settled. Results of recent clinical published trials highlight the need for minimizing fluid administration and attempting to use diuretics to achieve a negative fluid, although hypovolemia and hypoperfusion should be carefully considered. An individualized optimization of fluid status, using goal-directed therapy, has emerged as a possible preferable approach. The old debate between crystalloid and colloid solutions has been partially solved, as some colloids have demonstrated deleterious effect on renal function and coagulation system. Various preventive strategies have also emerged for minimizing fluid-related complications.

Effect of preoperative statin therapy on postoperative acute kidney injury in patients undergoing major surgery: systemic review and meta-analysis

We aimed to examine the association between preoperative use of statins and postoperative acute kidney injury (AKI) in patients undergoing major surgery by performing a systemic review and meta-analysis. MEDLINE and EMBASE, from inception to April 2013, and the reference lists of related articles were searched for relevant studies. Trials comparing preoperative statin therapy with no preoperative statin in patients undergoing major surgery were included. Outcome measures of interest were the risk of cumulative postoperative AKI and postoperative AKI requiring renal replacement therapy (RRT). Fixed or random effect meta-analysis was performed to derive summary effect estimates. In five randomized controlled trials (RCTs) and 19 observational studies, comprising a total of 989 173 patients undergoing major surgery, 112 840 patients (11.41%) received preoperative statin therapy. The specific type, dosage, and duration of statin therapy were not available in most studies. Preoperative statin therapy was associated with a significant risk reduction for cumulative postoperative AKI (weighted summary odds ratio (OR) 0.87, 95% CI 0.79 to 0.95). The effect of risk reduction was also significant when considering postoperative AKI requiring RRT (OR 0.80, 95% CI 0.72 to 0.90). When restricting the analysis to the five RCTs, preoperative statin therapy did not show significant protective effect on postoperative AKI (OR 0.49, 95% CI 0.22 to 1.09). In patients undergoing major surgery, preoperative statin therapy could associate with a reduced risk for postoperative AKI. However, considerable heterogeneity existed among included studies. Future randomized trials were warranted for this critical clinical question.

Predictive models for kidney disease: improving global outcomes (KDIGO) defined acute kidney injury in UK cardiac surgery

Introduction

Acute kidney injury (AKI) risk prediction scores are an objective and transparent means to enable cohort enrichment in clinical trials or to risk stratify patients preoperatively. Existing scores are limited in that they have been designed to predict only severe, or non-consensus AKI definitions and not less severe stages of AKI, which also have prognostic significance. The aim of this study was to develop and validate novel risk scores that could identify all patients at risk of AKI.

Methods

Prospective routinely collected clinical data (n = 30,854) were obtained from 3 UK cardiac surgical centres (Bristol, Birmingham and Wolverhampton). AKI was defined as per the Kidney Disease: Improving Global Outcomes (KDIGO) Guidelines. The model was developed using the Bristol and Birmingham datasets, and externally validated using the Wolverhampton data. Model discrimination was estimated using the area under the ROC curve (AUC). Model calibration was assessed using the Hosmer–Lemeshow test and calibration plots. Diagnostic utility was also compared to existing scores.

Results

The risk prediction score for any stage AKI (AUC = 0.74 (95% confidence intervals (CI) 0.72, 0.76)) demonstrated better discrimination compared to the Euroscore and the Cleveland Clinic Score, and equivalent discrimination to the Mehta and Ng scores. The any stage AKI score demonstrated better calibration than the four comparison scores. A stage 3 AKI risk prediction score also demonstrated good discrimination (AUC = 0.78 (95% CI 0.75, 0.80)) as did the four comparison risk scores, but stage 3 AKI scores were less well calibrated.

Conclusions

This is the first risk score that accurately identifies patients at risk of any stage AKI. This score will be useful in the perioperative management of high risk patients as well as in clinical trial design.

Validation of cell-cycle arrest biomarkers for acute kidney injury after pediatric cardiac surgery

Background

The lack of early biomarkers for acute kidney injury (AKI) seriously inhibits the initiation of preventive and therapeutic measures for this syndrome in a timely manner. We tested the hypothesis that insulin-like growth factor-binding protein 7 (IGFBP7) and tissue inhibitor of metalloproteinases-2 (TIMP-2), both inducers of G1 cell cycle arrest, function as early biomarkers for AKI after congenital heart surgery with cardiopulmonary bypass (CPB).

Methods

We prospectively studied 51 children undergoing cardiac surgery with CPB. Serial urine samples were analyzed for [TIMP-2]•[IGFBP7]. The primary outcome measure was AKI defined by the pRIFLE criteria within 72 hours after surgery.

Results

12 children (24%) developed AKI within 1.67 (SE 0.3) days after surgery. Children who developed AKI after cardiac surgery had a significant higher urinary [TIMP-2]•[IGFBP7] as early as 4 h after the procedure, compared to children who did not develop AKI (mean of 1.93 ((ng/ml)²/1000) (SE 0.4) vs 0.47 ((ng/ml)²/1000) (SE 0.1), respectively; p<0.05). Urinary [TIMP-2]•[IGFBP7] 4 hours following surgery demonstrated an area under the receiver-operating characteristic curve of 0.85. Sensitivity was 0.83, and specificity was 0.77 for a cutoff value of 0.70 ((ng/ml)²/1000).

Conclusions

Urinary [TIMP-2]•[IGFBP7] represent sensitive, specific, and highly predictive early biomarkers for AKI after surgery for congenital heart disease.

Trial Registration

www.germanctr.de/, DRKS00005062

Addition of N-acetyl cysteine to carvedilol decreases the incidence of acute renal injury after cardiac surgery

BACKGROUND

Oxidative stress and inflammation during cardiac surgery may be associated with acute renal injury (ARI). N-acetyl cysteine (NAC) and carvedilol have antioxidant and anti-inflammatory properties.

HYPOTHESIS

A combination of carvedilol and NAC should decrease the incidence of ARI more than metoprolol or carvedilol.

METHODS

Patients undergoing cardiac surgery were randomized to metoprolol, carvedilol, or carvedilol plus NAC. End points were occurrence of ARI and change in preoperative to postoperative peak creatinine levels.

RESULTS

ARI incidence was lower in the carvedilol plus NAC group compared with the metoprolol (21.0% vs 42.1%; P = 0.002) or carvedilol (21.0% vs 38.6%; P = 0.006) groups, but was similar between the metoprolol and carvedilol groups (P = 0.62). Preoperative and postoperative day 1 creatinine levels were similar among the metoprolol (1.02 [0.9-1.2] and 1.2 [0.92-1.45]) the carvedilol (1.0 [0.88-1.08] and 1.2 [0.9-1.5]) and the carvedilol plus NAC groups (1.06 [0.9-1.18] and 1.1 [1.0-1.21] mg/dL; all P values >0.05). Postoperative day 3, day 5, and peak creatinine levels were lower in the carvedilol plus NAC group (1.11 [1.0-1.23], 1.14 [1.0-1.25] and 1.15 [1.0-1.25]) as compared with the metoprolol (1.4 [1.3-1.49], 1.3 [1.0-1.54] and 1.3 [1.0-1.54]) or carvedilol groups (1.2 [1.0-1.52], 1.25 [1.0-1.52] and 1.25 [1.0-1.55] mg/dL; all P values <0.05), but were similar between the metoprolol and carvedilol groups (all P values >0.05).

CONCLUSIONS

Combined carvedilol and NAC decreased ARI incidence as compared with carvedilol or metoprolol. No difference was detected between carvedilol and metoprolol.

Perfusionist techniques of reducing acute kidney injury following cardiopulmonary bypass: an evidence-based review

Cardiac surgery utilizing cardiopulmonary bypass has come a long way since its introduction nearly 60 years ago. In the early days, end-organ damage was linked to contact of the blood with the extracorporeal circuit. One potential cardiac surgery complication known to result in significant morbidity and mortality is acute kidney injury (AKI). Causes of AKI are multifaceted, but most of them are associated with techniques that perfusionists employ during extracorporeal circuit management. These can cause patients to either go on dialysis or renal replacement therapy. Patients with AKI have longer lengths of stay and consume significant resources beyond those with normal kidney function. Few current evidence-based markers determine if the kidneys are adequately protected during surgery. Most relevant literature does not address perfusion-specific techniques that reduce the incidence of AKI. This paper reviews the pathophysiology of the kidney and focuses on perfusion techniques that may reduce the incidence of AKI.

Association between preoperative statin use and acute kidney injury biomarkers in cardiac surgical procedures

BACKGROUND

Acute kidney injury (AKI) is a serious complication of cardiac operations for which there remains no specific therapy. Animal data and several observational studies suggest that statins prevent AKI, but the results are not conclusive, and many studies are retrospective in nature.

METHODS

We conducted a multicenter prospective cohort study of 625 adult patients undergoing elective cardiac operations. All patients were taking statins and were grouped according to whether statins were continued or held in the 24 hours before operation. The primary outcome was AKI as defined by a doubling of serum creatinine or dialysis. The secondary outcome was the peak level of several kidney injury biomarkers. The results were adjusted for demographic and clinical factors.

RESULTS

Continuing (vs holding) a statin before operation was not associated with a lower risk of AKI, as defined by a doubling of serum creatinine or dialysis (adjusted relative risk [RR] 1.09; 95% confidence interval [CI] 0.44, 2.70). However, continuing a statin was associated with a lower risk of elevation of the following AKI biomarkers: urine interleukin-18, urine neutrophil gelatinase-associated lipocalin, urine kidney injury molecule-1, and plasma neutrophil gelatinase-associated lipocalin (adjusted RR 0.34; 95% CI 0.18, 0.62), (adjusted RR 0.41; 95% CI 0.22, 0.76), (adjusted RR 0.37; 95% CI 0.20, 0.76), (adjusted RR 0.62; 95% CI 0.39, 0.98), respectively.

CONCLUSIONS

Statins may prevent kidney injury after cardiac operations, as evidenced by lower levels of kidney injury biomarkers.

Steroids In caRdiac Surgery (SIRS) trial: acute kidney injury substudy protocol of an international randomised controlled trial

INTRODUCTION

Steroids In caRdiac Surgery trial (SIRS) is a large international randomised controlled trial of methylprednisolone or placebo in patients undergoing cardiac surgery with the use of a cardiopulmonary bypass pump. At the time of surgery, compared with placebo, methylprednisolone divided into two intravenous doses of 250 mg each may reduce the risk of postoperative acute kidney injury (AKI).

METHODS AND ANALYSIS

With respect to the study schedule, over 7000 substudy eligible patients from 81 centres in 18 countries were randomised in December 2013. The authors will use a logistic regression to estimate the adjusted OR of methylprednisolone versus placebo on the primary outcome of AKI in the 14 days following surgery (a postoperative increase in serum creatinine of ≥50%, or ≥26.5 μmol/L, from the preoperative value). The stage of AKI will also be considered, as will the outcome of AKI in those with and without preoperative chronic kidney disease. After receipt of grant funding, the authors began to record additional perioperative serum creatinine measurements in consecutive patients enrolled at substudy participating centres, and patients were invited to enroll in a 6-month serum creatinine collection. In these trial subpopulations, the authors will consider the outcome of AKI defined in alternate ways, and the outcome of a 6-month change in kidney function from the preoperative value.

ETHICS AND DISSEMINATION

The authors were competitively awarded a grant from the Canadian Institutes of Health Research for this SIRS AKI substudy. Ethics approval was obtained for additional serum creatinine recordings in consecutive patients enrolled at participating centres. The additional kidney data collection first began for patients enrolled after 1 March 2012. In patients who provided consent, the last 6-month kidney outcome data will be collected in 2014. The results will be reported no later than 2015.

CLINICAL TRIAL REGISTRATION

Number NCT00427388.

Risk factors for endotracheal re-intubation following coronary artery bypass grafting

BACKGROUND

Endotracheal re-intubation following coronary artery bypass grafting (CABG) is often associated with significant morbidity and mortality. However, few reports have focused on the independent risk factors for re-intubation following CABG. This study aimed to evaluate the independent risk factors for re-intubation following CABG.

METHODS

The pre-, intra-, and post-operative materials in patients who had selective and isolated CABG performed on them from January 2004 to July 2012 in our hospital were analyzed retrospectively. Unvariate analysis and logistic regression were used to analyze the risk factor of postoperative re-intubation following CABG.

RESULTS

Among the 1,244 patients investigated, 97 cases suffered from postoperative re-intubation, and the incidence rate of postoperative re-intubation was 7.8%. The in-hospital mortality in the re-intubation group was significantly higher than that in the non-re-intubation group (9.3% versus 1.4%, P = 0.004). Re-intubation also correlated with many negative outcomes such as pneumonia, tracheotomy, acute renal failure, infection of incision, prolonged mechanical ventilation time, prolonged intensive care unit (ICU) stay and prolonged hospital stay. The most commonly cause of re-intubation after CABG was hypoxemia due to cardiogenic and noncardiogenic disease, which accounted for 72.2%. The relative factors of postoperative re-intubation were tested through unvariate analysis and logistic regression, and the associated factors were obtained. The associated factors for re-intubation following CABG included preoperative chronic obstructive pulmonary disease (COPD) (OR = 2.134, 95% CI = 1.472-2.967), preoperative congestive heart failure (CHF) (OR = 2.325, 95% CI = 1.512-3.121), postoperative relative hypoxemia (OR = 2.743, 95% CI = 1.657-3.326), postoperative acute kidney injury (AKI) (OR = 2.976, 95% CI = 2.127-4.023), postoperative total mechanical ventilation time (OR = 1.976, 95% CI = 1.347-2.645).

CONCLUSION

Preoperative COPD, preoperative CHF, postoperative relative hypoxemia, postoperative AKI and postoperative total mechanical ventilation time were five independent risk factors for re-intubation following CABG.

Perioperative intravascular volume replacement and kidney insufficiency

Perioperative acute kidney injury (AKI) occurrence is probably increased in recent years due to the increased level of complexity of surgical procedures and severity of illness of surgical patients. Perioperative AKI has a multifactorial aetiology (preoperative co-morbidities such as diabetes, heart failure and chronic kidney disease, emergent surgery, exposure to nephrotoxic drugs, haemodynamic instability, hypothermia, inflammatory response to surgery, hospital-acquired infections and abdominal compartment syndrome). However, fluid choice for perioperative volume replacement might have a major role in perioperative AKI, as administration of crystalloid solutions, colloids or haemoderivates has the potential for kidney injury. This review focusses on the issue of fluid replacement quality and quantity and their association with renal dysfunction.

Prophylaxis with erythropoietin versus placebo reduces acute kidney injury and neutrophil gelatinase-associated lipocalin in patients undergoing cardiac surgery: a randomized, double-blind controlled trial

BACKGROUND

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common complication following coronary bypass graft (CABG) surgery. Multi-factorial causes of CSA-AKI involve oxidative stress and inflammation. Erythropoietin (EPO) has been shown from many studies to have a reno-protective effect. The present study was conducted to examine the role of EPO in preventing CSA-AKI.

METHODS

This prospective, randomized, double-blind, placebo-controlled trial was conducted in the Cardiovascular and Thoracic Unit. One hundred patients randomly received either 200 U/kg of rHuEPO (n = 50) or saline (n = 50) intravenously three days before operation, and rHuEPO 100 U/kg or saline at operation time. The serum creatinine (SCr), estimated glomerular filtration rate (eGFR) and urine neutrophil gelatinase-associated lipocaline (NGAL) were measured in order to evaluate renal injury following CABG.

RESULTS

The incidence of CSA-AKI was significantly lower in rHuEPO group (14%) when compared with the placebo group (38%; p < 0.01). The mean intensive care unit (ICU) and hospital stays of the rHuEPO group were significantly shorter than the placebo group (p < 0.01). Postoperative increases in SCr and decreases in eGFR were significantly lower in the rHuEPO group than the placebo group (p < 0.05). The mean urine NGAL in rHuEPO group was significantly lower than the placebo group at 3 hr, 6 hr, 12 hr and 18 hr after CABG (p < 0.05), respectively.

CONCLUSIONS

Prophylaxis administration with intravenous rHuEPO before cardiac surgery decreased the incidence of CSA-AKI and urine NGAL with reduced days in ICU and hospital in elective CABG patients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01066351.

The effects of VARC-defined acute kidney injury after transcatheter aortic valve implantation (TAVI) using the Edwards bioprosthesis

AIMS

The aim of this study was to identify the incidence and risk factors for acute kidney injury (AKI) after TAVI, a potentially serious complication of transcatheter aortic valve implantation (TAVI) that has been redefined by the Valve Academic Research Consortium (VARC).

METHODS AND RESULTS

We performed a retrospective analysis of 248 patients undergoing TAVI. AKI was defined as a VARC-modified Risk, Injury, Failure, Loss, and End-stage (RIFLE) kidney disease score ≥ 2. Eighty-nine patients suffered AKI (35.9%) and demonstrated increased mortality at 30 days (13.5% vs. 3.8%) and one year (31.5% vs. 15.0%) (p<0.001). Multivariate regression analysis identified diabetes mellitus (p<0.001), peripheral vascular disease (p=0.007), chronic kidney disease stage (p=0.010) as independently associated risk factors for AKI.

CONCLUSIONS

More than one third of patients sustain AKI after TAVI using the Edwards bioprosthesis, as defined by the VARC-modified RIFLE score. AKI increased the mortality at both 30 days and at one year. A history of diabetes mellitus, peripheral vascular disease and higher chronic kidney disease stage had the strongest independent associations with post-TAVI AKI.

Clinical utility of biomarkers of AKI in cardiac surgery and critical illness

AKI is a common and serious complication that is associated with several adverse outcomes in hospitalized patients. The past several years have seen a large number of multicenter investigations of biomarkers of AKI in the setting of cardiac surgery and critical illness. This review summarizes these biomarker results to identify applications for clinical use. The Translational Research Investigating Biomarker Endpoints in AKI (TRIBE-AKI) study showed that blood and urine biomarkers measured preoperatively, immediately postoperatively, and at the time of the clinical increase in serum creatinine in the setting of cardiac surgery all had the ability to improve patient risk stratification for a variety of important clinical end points. Analyses of biomarkers concentrations from the Acute Respiratory Distress Syndrome Network, EARLY ARF, and other studies of critically ill subjects have similarly shown that biomarkers measured early in the clinical course can forecast the development of AKI and need for renal replacement therapy as well as inpatient mortality. Although biomarkers have informed the diagnosis, prognosis, and treatment of AKI and are inching closer to clinical application, large multicenter interventional clinical trials to prevent AKI using biomarkers should continue to be an active area of clinical investigation.

Update on clinical trials for the prevention of acute kidney injury in patients undergoing cardiac surgery

BACKGROUND

Effective therapeutic agents for the prevention and treatment of acute kidney injury (AKI) after cardiac surgery remain elusive despite the tremendous advances in surgical techniques, technology, and understanding of disease processes. Recent developments and their effect on the incidence of AKI after cardiac surgery are discussed.

DATA SOURCES

Published clinical trials in PubMed, strength of evidence assessed by the guidelines of the American Family Physicians.

CONCLUSIONS

The definition of AKI has changed, and the focus of interventions has shifted from treatment to prevention to recovery from AKI. Antioxidants and biological agents have been added to classic armaments of hydration and diuretics in addition to tighter metabolic control to prevent AKI. Although the treatment options remain unsatisfactory, a lot of progress nevertheless continues to be made in the prevention and treatment of AKI.

Implementation of an intraoperative glycemic control protocol for cardiac surgery in a high-acuity academic medical center: an observational study

STUDY OBJECTIVE

To examine the effect on morbidity and mortality of an established intraoperative insulin protocol in cardiac surgical patients.

DESIGN

Retrospective observational study.

SETTING

Single-center, 782 bed, metropolitan academic hospital.

PATIENTS

1,616 adult patients undergoing cardiac surgical procedures with cardiopulmonary bypass (CPB).

INTERVENTIONS

An intraoperative, intravenous (IV) insulin protocol designed to maintain blood glucose values less than 150 mg/dL was implemented.

MEASUREMENTS

Blood glucose was evaluated on entry to the operating room, every 30 minutes during CPB, and at least once after discontinuation of CPB. Blood glucose values were followed postoperatively, as dictated by institutional policy.

MAIN RESULTS

Intraoperative predictors of 30-day mortality using multivariate logistic regression included hyperglycemia on initiation of CPB (OR 1.0, P = 0.05). The strongest predictor of 30-day mortality was the development of postoperative renal failure requiring hemodialysis (OR 3.26, P = 0.001).

CONCLUSIONS

Implementation of an intraoperative IV insulin protocol, while associated with improved glycemic control, was not associated with improved outcomes. While improved glycemic control on initiating CPB was associated with decreased 30-day mortality, the effect was small. Implementation of our insulin protocol was highly associated with decreased renal failure postoperatively. Further prospective studies are warranted to better establish causality.

Epoetin administrated after cardiac surgery: effects on renal function and inflammation in a randomized controlled study

Background

Experimentally, erythropoietin (EPO) has nephroprotective as well as immunomodulatory properties when administered after ischemic renal injury. We tested the hypothesis that different doses of recombinant human EPO administered to patients after cardiac surgery would minimize kidney lesions and the systemic inflammatory response, thereby decreasing acute kidney injury (AKI) incidence.

Methods

In this double-blinded randomized control study, 80 patients admitted to the ICU post-cardiac surgery were randomized by computer to receive intravenously isotonic saline (n = 40) versus α-Epoetin (n = 40): either 40000 IU (n = 20) or 20000 IU (n = 20). The study lasted one year. The primary outcome was the change in urinary NGAL concentration from baseline and 48 h after EPO injection. Creatinine, cystatine C and urinary NGAL levels were measured on the day of randomization and 2–4 days after EPO injection. To assess acute inflammatory response, serum cytokines (IL6 and IL8) were measured at randomization and four days after r-HuEPO injection. Patients and care-takers were blinded for the assignment.

Results

No patient was excluded after randomization. Patient groups did not differ in terms of age, gender, comorbidities and renal function at randomization. The rate of AKI assessed by AKIN criteria was 22.5% in our population. EPO treatment did not significantly modify the difference in uNGAl between 48 hours and randomization compared to placebo [2.5 ng/ml (−17.3; 22.5) vs 0.7 ng/ml (−31.77; 25.15), p = 0.77] and the incidence of AKI was similar. Inflammatory cytokines levels were not influenced by EPO treatment. Mortality and hospital stays were similar between the groups and no adverse event was recorded.

Conclusion

In this randomized-controlled trial, α-Epoetin administrated after cardiac surgery, although safe, demonstrated neither nephroprotective nor anti-inflammatory properties.

Trial registration number

NCT00676234

Association of postoperative proteinuria with AKI after cardiac surgery among patients at high risk

BACKGROUND AND OBJECTIVES

Preoperative proteinuria is associated with a higher incidence of postoperative AKI. Whether the same is true for postoperative proteinuria is uncertain. This study tested the hypothesis that increased proteinuria after cardiac surgery is associated with an increased risk for AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This prospective cohort study included 1198 adults undergoing cardiac surgery at six hospitals between July 2007 and December 2009. Albuminuria, urine albumin-to-creatinine ratio (ACR), and dipstick proteinuria were measured 0-6 hours after surgery. The primary outcome was AKI, defined as a doubling in serum creatinine or receipt of acute dialysis during the hospital stay. Analyses were adjusted for patient characteristics, including preoperative albuminuria.

RESULTS

Compared with the lowest quintile, the highest quintile of albuminuria and highest grouping of dipstick proteinuria were associated with greatest risk for AKI (adjusted relative risks [RRs], 2.97 [95% confidence interval (CI), 1.20-6.91] and 2.46 [95% CI, 1.16-4.97], respectively). Higher ACR was not associated with AKI risk (highest quintile RR, 1.66 [95% CI, 0.68-3.90]). Of the three proteinuria measures, early postoperative albuminuria improved the prediction of AKI to the greatest degree (clinical model area under the curve, 0.75; 0.81 with albuminuria). Similar improvements with albuminuria were seen for net reclassification index (0.55; P<0.001) and integrated discrimination index (0.036; P<0.001).

CONCLUSIONS

Higher levels of proteinuria after cardiac surgery identify patients at increased risk for AKI during their hospital stay.

Secular trends in acute dialysis after elective major surgery--1995 to 2009

BACKGROUND

Acute kidney injury is a serious complication of elective major surgery. Acute dialysis is used to support life in the most severe cases. We examined whether rates and outcomes of acute dialysis after elective major surgery have changed over time.

METHODS

We used data from Ontario's universal health care databases to study all consecutive patients who had elective major surgery at 118 hospitals between 1995 and 2009. Our primary outcomes were acute dialysis within 14 days of surgery, death within 90 days of surgery and chronic dialysis for patients who did not recover kidney function.

RESULTS

A total of 552,672 patients underwent elective major surgery during the study period, 2231 of whom received acute dialysis. The incidence of acute dialysis increased steadily from 0.2% in 1995 (95% confidence interval [CI] 0.15-0.2) to 0.6% in 2009 (95% CI 0.6-0.7). This increase was primarily in cardiac and vascular surgeries. Among patients who received acute dialysis, 937 died within 90 days of surgery (42.0%, 95% CI 40.0-44.1), with no change in 90-day survival over time. Among the 1294 patients who received acute dialysis and survived beyond 90 days, 352 required chronic dialysis (27.2%, 95% CI 24.8-29.7), with no change over time.

INTERPRETATION

The use of acute dialysis after cardiac and vascular surgery has increased substantially since 1995. Studies focusing on interventions to better prevent and treat perioperative acute kidney injury are needed.

Coronary Artery Bypass Grafting Surgery Off- or On-pump Revascularisation Study (CORONARY): kidney substudy analytic protocol of an international randomised controlled trial

INTRODUCTION

CORONARY is a large international randomised controlled trial comparing coronary artery bypass graft (CABG) surgery done with and without a bypass pump. Compared with on-pump, off-pump surgery may prevent acute kidney injury (AKI) in the short term and may better preserve kidney function 1 year following surgery. Secondary analyses may also clarify whether effects are similar in patients with and without pre-operative chronic kidney disease and whether AKI avoidance mediates preserved 1-year kidney function.

METHODS AND ANALYSIS

With respect to the study schedule, the last of 4752 patients from 79 sites in 19 countries were randomised in November 2011 to cardiac surgery performed with an on-pump or off-pump procedure. The authors will use regression models to compare the groups in the outcome of peri-operative AKI (per cent change in serum creatinine, ≥50% increase in serum creatinine) and 1-year kidney function (per cent change in estimated glomerular filtration rate (eGFR), ≥20% eGFR loss 1 year after surgery). The authors will use interaction terms in regression models to determine if there is a differential impact of the intervention in those with and without pre-existing chronic kidney disease. The authors will use regression-based tests to determine the proportion of the total effect of surgery type (off-pump vs on-pump CABG) on 1-year eGFR that is mediated by peri-operative AKI.

ETHICS AND DISSEMINATION

In the year 2009, the authors were competitively awarded a grant from the Canadian Institutes of Health Research to answer these kidney questions in CORONARY. Ethics approval was obtained for additional renal data collection in centres that agreed to study participation (>90% of participating centres). This collection began for patients enrolled after 1 January 2010. Remaining 1-year renal outcome data will be collected throughout 2012. Results will be reported in 2013.

CLINICAL TRIAL REGISTRATION NUMBER

NCT 00463294.

Postoperative biomarkers predict acute kidney injury and poor outcomes after pediatric cardiac surgery

Acute kidney injury (AKI) occurs commonly after pediatric cardiac surgery and associates with poor outcomes. Biomarkers may help the prediction or early identification of AKI, potentially increasing opportunities for therapeutic interventions. Here, we conducted a prospective, multicenter cohort study involving 311 children undergoing surgery for congenital cardiac lesions to evaluate whether early postoperative measures of urine IL-18, urine neutrophil gelatinase-associated lipocalin (NGAL), or plasma NGAL could identify which patients would develop AKI and other adverse outcomes. Urine IL-18 and urine and plasma NGAL levels peaked within 6 hours after surgery. Severe AKI, defined by dialysis or doubling in serum creatinine during hospital stay, occurred in 53 participants at a median of 2 days after surgery. The first postoperative urine IL-18 and urine NGAL levels strongly associated with severe AKI. After multivariable adjustment, the highest quintiles of urine IL-18 and urine NGAL associated with 6.9- and 4.1-fold higher odds of AKI, respectively, compared with the lowest quintiles. Elevated urine IL-18 and urine NGAL levels associated with longer hospital stay, longer intensive care unit stay, and duration of mechanical ventilation. The accuracy of urine IL-18 and urine NGAL for diagnosis of severe AKI was moderate, with areas under the curve of 0.72 and 0.71, respectively. The addition of these urine biomarkers improved risk prediction over clinical models alone as measured by net reclassification improvement and integrated discrimination improvement. In conclusion, urine IL-18 and urine NGAL, but not plasma NGAL, associate with subsequent AKI and poor outcomes among children undergoing cardiac surgery.

Postoperative biomarkers predict acute kidney injury and poor outcomes after adult cardiac surgery

Acute kidney injury (AKI) is a frequent complication of cardiac surgery and increases morbidity and mortality. The identification of reliable biomarkers that allow earlier diagnosis of AKI in the postoperative period may increase the success of therapeutic interventions. Here, we conducted a prospective, multicenter cohort study involving 1219 adults undergoing cardiac surgery to evaluate whether early postoperative measures of urine IL-18, urine neutrophil gelatinase-associated lipocalin (NGAL), or plasma NGAL could identify which patients would develop AKI and other adverse patient outcomes. Urine IL-18 and urine and plasma NGAL levels peaked within 6 hours after surgery. After multivariable adjustment, the highest quintiles of urine IL-18 and plasma NGAL associated with 6.8-fold and 5-fold higher odds of AKI, respectively, compared with the lowest quintiles. Elevated urine IL-18 and urine and plasma NGAL levels associated with longer length of hospital stay, longer intensive care unit stay, and higher risk for dialysis or death. The clinical prediction model for AKI had an area under the receiver-operating characteristic curve (AUC) of 0.69. Urine IL-18 and plasma NGAL significantly improved the AUC to 0.76 and 0.75, respectively. Urine IL-18 and plasma NGAL significantly improved risk prediction over the clinical models alone as measured by net reclassification improvement (NRI) and integrated discrimination improvement (IDI). In conclusion, urine IL-18, urine NGAL, and plasma NGAL associate with subsequent AKI and poor outcomes among adults undergoing cardiac surgery.