Blood transfusions are associated with urinary biomarkers of kidney injury in cardiac surgery

Deleterious effects of plasma-derived cellular debris in a porcine model of hemorrhagic shock

BACKGROUND

Recent studies identify large quantities of inflammatory cellular debris within Fresh Frozen Plasma (FFP). As FFP is a mainstay of hemorrhagic shock resuscitation, we used a porcine model of hemorrhagic shock and ischemia/reperfusion to investigate the inflammatory potential of plasma-derived cellular debris administered during resuscitation.

METHODS

The porcine model of hemorrhagic shock included laparotomy with 35 % hemorrhage (Hem), 45 min of ischemia from supraceliac aortic occlusion with subsequent clamp release (IR), followed by protocolized resuscitation for 6 h. Cellular debris (Debris) was added to the resuscitation phase in three groups. The four groups consisted of Hem + IR (n = 4), Hem + IR + Debris (n = 3), Hem + Debris (n = 3), and IR + Debris (n = 3). A battery of laboratory, physiologic, cytokine, and outcome data were compared between groups.

RESULTS

As expected, the Hem + IR group showed severe time dependent decrements in organ function and physiologic parameters. All animals that included both IR and Debris (Hem + IR + Debris or IR + Debris) died prior to the six-hour end point, while all animals in the Hem + IR and Hem + Debris survived. Cytokines measured at 30-60 min after initiation of resuscitation revealed significant differences in IL-18 and IL-1β between all groups.

CONCLUSIONS

Ischemia and reperfusion appear to prime the immune system to the deleterious effects of plasma-derived cellular debris. In the presence of ischemia and reperfusion, this model showed the equivalency of 100 % lethality when resuscitation included quantities of cellular debris at levels routinely administered to trauma patients during transfusion of FFP. A deeper understanding of the immunobiology of FFP-derived cellular debris is critical to optimize resuscitation for hemorrhagic shock.

Adverse renal effects associated with cardiopulmonary bypass

Cardiac surgery on cardiopulmonary bypass (CPB) is associated with postoperative renal dysfunction, one of the most common complications of this surgical cohort. Acute kidney injury (AKI) is associated with increased short-term morbidity and mortality and has been the focus of much research. There is increasing recognition of the role of AKI as the key pathophysiological state leading to the disease entities acute and chronic kidney disease (AKD and CKD). In this narrative review, we will consider the epidemiology of renal dysfunction after cardiac surgery on CPB and the clinical manifestations across the spectrum of disease. We will discuss the transition between different states of injury and dysfunction, and, importantly, the relevance to clinicians. The specific facets of kidney injury on extracorporeal circulation will be described and the current evidence evaluated for the use of perfusion-based techniques to reduce the incidence and mitigate the complications of renal dysfunction after cardiac surgery.

Cardiac surgery-Associated acute kidney injury - A narrative review

Cardiac Surgery-Associated Acute Kidney Injury (CSA-AKI) is a serious complication seen in approximately 20-30% of cardiac surgery patients. The underlying pathophysiology is complex, often involving both patient- and procedure related risk factors. In contrast to AKI occurring after other types of major surgery, the use of cardiopulmonary bypass comprises both additional advantages and challenges, including non-pulsatile flow, targeted blood flow and pressure as well as the ability to manipulate central venous pressure (congestion). With an increasing focus on the impact of CSA-AKI on both short and long-term mortality, early identification and management of high-risk patients for CSA-AKI has evolved. The present narrative review gives an up-to-date summary on definition, diagnosis, underlying pathophysiology, monitoring and implications of CSA-AKI, including potential preventive interventions. The review will provide the reader with an in-depth understanding of how to identify, support and provide a more personalized and tailored perioperative management to avoid development of CSA-AKI.

Kidney Injury after Cardiac Surgery: Prevention-Associated Cost Reduction

INTRODUCTION

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSION

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

Pulmonary, circulatory and renal considerations in the early postoperative management of the lung transplant recipient

Lung transplantation volumes and survival rates continue to increase worldwide. Primary graft dysfunction (PGD) and acute kidney injury (AKI) are common early postoperative complications that significantly affect short-term mortality and long-term outcomes. These conditions share overlapping risk factors and are driven, in part, by circulatory derangements. The prevalence of severe PGD is up to 20% and is the leading cause of early death. Patients with pulmonary hypertension are at a higher risk. Prevention and management are based on principles learned from acute lung injury of other causes. Targeting the lowest effective cardiac filling pressure will reduce alveolar edema formation in the setting of increased pulmonary capillary permeability. AKI is reported in up to one-half of lung transplant recipients and is strongly associated with one-year mortality as well as long-term chronic kidney disease. Optimization of renal perfusion is critical to reduce the incidence and severity of AKI. In this review, we highlight key early post-transplant pulmonary, circulatory, and renal perturbations and our center's management approach.

Impact of postoperative acute kidney injury on short-term outcomes of patients with Bentall surgery for any reason

BACKGROUND

Acute kidney injury (AKI) after cardiac surgery is a well-known risk factor for increased postoperative mortality and morbidity. The effect of postoperative developed AKI on postoperative outcomes in patients after Bentall procedure has been incompletely investigated. The present study was dedicated to assessing the impact of postoperative AKI on morbidity and 30-day mortality in this specific cohort.

METHODS

In a retrospective observational study, we investigated 249 patients undergoing Bentall procedure from January 2014 to March 2018 at the University Hospital of Cologne, Germany. After excluding patients with preoperative renal impairment, patients were divided into an AKI group (n = 88) and a non-AKI group (n = 97). Postoperative outcomes and 30-day mortality were analyzed using univariate regression analysis. AKI was defined by AKIN criteria.

RESULTS

Mortality during ICU and hospital stay, as well as 30-day mortality, was significantly higher in the AKI group (all p < 0.001). Patients with postoperative developed AKI revealed 9.3-fold higher odds for ICU mortality and 6.7-fold higher odds for 30-day mortality in comparison to non-AKI group (all p < 0.004) as well as 4.5-fold higher odds for stroke. Coronary artery bypass time, as well as cross-clamp time, were similarly distributed between groups, whereas incidences of postoperative bleeding, myocardial infarction, and need for rethoracotomy occurred significantly more often in patients with postoperatively developed AKI (all p < 0.04).

CONCLUSION

Patients undergoing Bentall surgery who postoperatively developed AKI showed significantly higher morbidity and mortality. AKI points out to be an early predictor for poor outcomes. Thus, as a consequence, patients with postoperatively developed AKI should be highly monitored for immediate intervention.

Intraoperative hemodialysis during open-heart surgery in patients with severe chronic kidney disease: a retrospective cohort study

Background

Acute kidney injury and chronic kidney disease (CKD) after cardiac surgery are associated with poor renal prognosis and increased mortality. The impact of intraoperative hemodialysis (IHD) on postoperative renal function remains unknown. We aimed to evaluate the utility of IHD during open-heart surgery in patients with severe non-dialysis-dependent chronic kidney disease (CKD-NDD) and its association with clinical outcomes.

Methods

This was a single-center retrospective cohort study that employed IHD during non-emergency open-heart surgery in patients with CKD stage G4 or G5. Patients who underwent emergent surgery, chronic dialysis, and/or kidney transplantation were excluded. We retrospectively compared the clinical characteristics and outcomes between patients from the IHD and non-IHD groups. The primary outcomes were 90-day mortality and postoperative initiation of renal replacement therapy (RRT).

Results

Twenty-eight patients were categorized into the IHD group and 33 into the non-IHD group. When comparing the IHD and non-IHD groups, men accounted for 60.7 vs. 50.3% of patients, the mean patient age was 74.5 (standard deviation [SD] 7.0) vs. 72.9 (SD 9.4) years (p = 0.744), and the proportion of patients with CKD G4 was 67.9 vs. 84.9% (p = 0.138). Regarding clinical outcomes, no significant differences were observed in the 90-day mortality (7.1 vs. 3.0%; p = 0.482) and 30-day RRT (17.9 vs. 30.3%; p = 0.373) rates between the groups. Among the patients with CKD G4, the IHD group had significantly lower 30-day RRT rates than the non-IHD group (0 vs. 25.0%; p = 0.032). RRT initiation was less likely for patients with CKD G4 (odds ratio 0.07, 95% confidence interval [CI] 0.01–0.37; p = 0.002); however, IHD did not significantly decrease the incidence of poor clinical outcomes (odds ratio 0.20, 95% CI 0.04–1.07; p = 0.061).

Conclusions

IHD during open-heart surgery in patients with CKD-NDD did not improve their clinical outcomes with regards to postoperative dialysis. However, for patients with CKD G4, IHD may be useful for postoperative cardiac management.

Interaction of hemoglobin, transfusion, and acute kidney injury in patients undergoing cardiopulmonary bypass: a group-based trajectory analysis

Anemia is a risk factor for acute kidney injury (AKI) following cardiopulmonary bypass (CPB). Whether red blood cell (RBC) transfusion-enhanced hemoglobin levels contribute to low AKI rates remains unclear. We investigated the interaction between hemoglobin, RBC transfusion, and AKI after CPB. Hemoglobin trajectories within 72 h were analyzed using group-based trajectory analysis. Multivariable logistic analysis and inverse probability-weighted regression were adopted to evaluate the associations between hemoglobin and AKI in RBC and non-RBC transfusion subgroups. We analyzed 6226 patients’ data. In the transfusion subgroup, three hemoglobin trajectories were identified. The AKI incidence was lowest in the trajectory with the lowest hemoglobin level (trajectory 1, less transfusion), and it was comparable in trajectories 2 and 3 (20.7% vs. 32.7% vs. 29.4%, p < 0.001, respectively). In four logistic models, the odds ratio for AKI with trajectory 1 as the reference ranged from 1.44 to 1.85 for trajectory 2 (p < 0.001) and 1.45 to 1.66 for trajectory 3 (p < 0.050). The average treatment effect on AKI was 5.6% (p = 0.009) for trajectory 2 and 7.5% (p = 0.041) for trajectory 3, with trajectory 1 as the reference. In the non-RBC transfusion subgroup, three approximately linear hemoglobin trajectories (9, 10, and 12 g/dL) were observed; however, both the crude and adjusted AKI incidence were similar within the three trajectories. In patients undergoing CPB, hemoglobin level >9 g/dL was not associated with decreased AKI incidence in the subgroup without RBC transfusion. However, in patients with RBC transfusion, maintaining hemoglobin level >9 g/dL by RBC transfusion was associated with increased AKI incidence.

Perioperative Management of the Patient at High-Risk for Cardiac Surgery-Associated Acute Kidney Injury

Acute kidney injury (AKI) is one of the most common major complications of cardiac surgery, and is associated with increased morbidity and mortality. Cardiac surgery-associated AKI has a complex, multifactorial etiology, including numerous factors such as primary cardiac dysfunction, hemodynamic derangements of cardiac surgery and cardiopulmonary bypass, and the possibility of a large volume of blood transfusion. There are no truly effective pharmacologic therapies for the management of AKI, and, therefore, anesthesiologists, intensivists, and cardiac surgeons must remain vigilant and attempt to minimize the risk of developing renal dysfunction. This narrative review describes the current state of the scientific literature concerning the specific aspects of cardiac surgery-associated AKI, and presents it in a chronological fashion to aid the perioperative clinician in their approach to this high-risk patient group. The evidence was considered for risk prediction models, preoperative optimization, and the intraoperative and postoperative management of cardiac surgery patients to improve renal outcomes.

Furosemide does not reduce the incidence of postoperative acute kidney injury in adult patients undergoing cardiac surgery: A PRISMA-compliant systematic review and meta-analysis

OBJECTIVE

Acute kidney injury (AKI) is a common complication of cardiac surgical patients, the occurrence of which is multifactorial. Furosemide is the most common loop diuretic and widely used in cardiac surgery to reduce fluid overload, increase tubular flow and urine output. It remains unknown whether furosemide affects the incidence or prognosis of cardiac surgery-induced acute kidney injury (CS-AKI). Therefore, the current study was performed to address this question.

METHODS

PubMed, Embase, Scopus, Cochrane Library, and Web of Science databases were searched for relevant studies. Primary outcomes of interest included postoperative CS-AKI incidence, need for renal replacement therapy (RRT) rate. Secondary outcomes of interest included postoperative serum creatinine (Scr) and blood urea nitrogen (BUN) levels, postoperative mechanical ventilation duration (MVD), length of stay (LOS) in intensive care unit (ICU) and in hospital, and mortality. The odds ratio (OR) and/or the weighted mean difference (WMD) with 95% confidence interval (CI) were used to pool the data.

RESULTS

Database search yielded six studies including 566 adult patients, and 283 patients were allocated into Group Furosemide and 283 into Group Control (Placebo). Heterogeneity between studies was deemed acceptable, and the publication bias was low. Meta-analysis suggested that furosemide administration in adult cardiac surgical patients had no effect on CS-AKI incidence (n = 4 trials; OR = 0.92; 95% CI: 0.37-2.30; p = .86; I²  = 57%) and need for RRT rate (n = 2 trials; OR = 4.13; 95% CI: 0.44-38.51; p = .21; I²  = 0%). Diversely, furosemide administration in adult cardiac surgical patients significantly decreased postoperative BUN level (n = 3 trials; WMD = 0.71; 95% CI: 0.10-1.33; p = .02; I²  = 0%), postoperative MVD (n = 2 trials; WMD = -3.13; 95% CI: -3.78 to -2.49; p < .00001; I²  = 0%) and postoperative LOS in ICU (n = 3 trials; WMD = -0.47; 95% CI: -0.76 to -0.18; p = .001; I²  = 0%). However, it had no significant impact on postoperative Scr level, postoperative LOS in hospital, and postoperative mortality.

CONCLUSION

This meta-analysis suggested that furosemide administration in adult cardiac surgical patients had no significant effect on CS-AKI incidence, need for RRT rate, postoperative Scr level, LOS in hospital and mortality, but could reduce postoperative BUN level, MVD, and LOS in ICU. As only a limited number of studies were included, these results should be interpreted carefully and cautiously. Future high-quality randomized controlled trials are needed to define the role of furosemide in CS-AKI prevention and management.

Urinary proteome analysis of acute kidney injury in post-cardiac surgery patients using enrichment materials with high-resolution mass spectrometry

Background: Cardiac surgery-associated acute kidney injury (CSA-AKI) may increase the mortality and incidence rates of chronic kidney disease in critically ill patients. This study aimed to investigate the underlying correlations between urinary proteomic changes and CSA-AKI.

Methods: Nontargeted proteomics was performed using nano liquid chromatography coupled with Orbitrap Exploris mass spectrometry (MS) on urinary samples preoperatively and postoperatively collected from patients with CSA-AKI. Gemini C18 silica microspheres were used to separate and enrich trypsin-hydrolysed peptides under basic mobile phase conditions. Differential analysis was conducted to screen out urinary differential expressed proteins (DEPs) among patients with CSA-AKI for bioinformatics. Kyoto Encyclopedia of Genes and Genomes (KEGG) database analysis was adopted to identify the altered signal pathways associated with CSA-AKI.

Results: Approximately 2000 urinary proteins were identified and quantified through data-independent acquisition MS, and 324 DEPs associated with AKI were screened by univariate statistics. According to KEGG enrichment analysis, the signal pathway of protein processing in the endoplasmic reticulum was enriched as the most up-regulated DEPs, and cell adhesion molecules were enriched as the most down-regulated DEPs. In protein–protein interaction analysis, the three hub targets in the up-regulated DEPs were α-1-antitrypsin, β-2-microglobulin and angiotensinogen, and the three key down-regulated DEPs were growth arrest-specific protein 6, matrix metalloproteinase-9 and urokinase-type plasminogen activator.

Conclusion: Urinary protein disorder was observed in CSA-AKI due to ischaemia and reperfusion. The application of Gemini C18 silica microspheres can improve the protein identification rate to obtain highly valuable resources for the urinary DEPs of AKI. This work provides valuable knowledge about urinary proteome biomarkers and essential resources for further research on AKI.

Transfusion-Related Renal Dysfunction After Cardiac Surgery

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Following cardiac surgery, 20% of patients will present with AKI, which is associated with increased mortality, and transfusion increases the risk of AKI.

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The main objective was to determine whether the composition of transfusion was associated with AKI.

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In this study, AKI patients received higher amount of MRP_14 through transfusion vs non-AKI.

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MRP_14 has been reported to activate and enhance neutrophil transmigration into damaged tissues. In a murine model of ischemia-reperfusion, MRP_14 increased renal damage and enhanced neutrophil influx into the kidney. MRP_14 also increased neutrophilic-trogocytosis toward tubular cells.

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The sex of the donor and the method of preparation of the blood determined the concentration of MRP_14 in packed red blood cells.

Transfusion is a specific cause of acute kidney injury (AKI) after cardiac surgery. Whether there is an association between the composition of blood products and the onset of AKI is unknown. The present study suggests that the transfusion of packed red blood cells containing a high amount of myeloid-related protein 14 (MRP_14) could increase the incidence of AKI after cardiac surgery. In a mouse model, MRP_14 increased the influx of neutrophils in the kidney after ischemia-reperfusion and their ability to damage tubular cells. Higher concentrations of MRP_14 were found in packed red blood cells from female donors or prepared by whole blood filtration.

Intraoperative venous congestion rather than hypotension is associated with acute adverse kidney events after cardiac surgery: a retrospective cohort study

BACKGROUND

The pathophysiological mechanisms by which venous congestion and hypotension lead to acute adverse kidney events after cardiac surgery with cardiopulmonary bypass have not been elucidated. We tested the hypothesis that intraoperative hypotension and venous congestion are associated with acute kidney injury and acute kidney disease.

METHODS

Primary exposures were venous congestion and intraoperative hypotension defined by central venous pressure ≥12, 16, or 20 mm Hg or mean arterial pressure ≤55, 65, or 75 mm Hg. The primary outcomes were acute kidney injury and acute kidney disease. Multivariable logistic regression and Cox proportional hazard models were used, adjusted for relevant confounding factors and multiple comparisons.

RESULTS

Of 5127 eligible subjects, 1070 (20.9%) and 327 (7.2%) developed acute kidney injury and acute kidney disease, respectively. The occurrence of acute kidney injury was statistically associated with both venous congestion and intraoperative hypotension. The cumulative incidence rate for new onset acute kidney disease was 1.34 (95% confidence interval [CI], 1.21-1.60) per 100 person-days. Acute kidney disease was significantly associated with each 10 min epoch of central venous pressure ≥12 mm Hg (hazard ratio [HR]=1.03; 99% CI, 1.01-1.06; P<0.001), ≥16 mm Hg (HR=1.04; 99% CI, 1.01-1.07; P<0.001), and ≥20 mm Hg (HR=1.07; 99% CI, 1.02-1.13; P<0.001). Venous congestion was associated with an 8-17% increased risk for de novo renal replacement therapy. In contrast, intraoperative hypotension was not associated with development of acute kidney disease.

CONCLUSION

Although both venous congestion and intraoperative hypotension are associated with acute kidney injury, only venous congestion correlates with acute kidney disease among patients undergoing cardiac surgery requiring cardiopulmonary bypass. The reported associations are suggestive of a pathophysiological role of venous congestion in acute kidney disease.

An Early Warning System for the Differential Diagnosis of In-Hospital Acute Kidney Injury for Better Patient Outcome: Study of a Quality Improvement Initiative

Background: Acute kidney injury (AKI) is a syndrome with heterogeneous causes and mechanisms. An early warning system (EWS) for AKI was created to reduce the incidence and improve outcomes. However, the benefits of AKI-EWS remain debatable. Methods: We launched a project to design and create AKI-EWS for inpatients in our institute. Incidence of AKI and its outcome before and after the implementation of AKI-EWS were collected for analysis. Results: We enlisted a stakeholder map before creating AKI-EWS. We then started an action plan for this initiative. The diagnosis was automatic and based on the definition of Kidney Disease: Improving Global Outcomes (KDIGO). The differential diagnosis of causes of AKI was also automatic. Users are to adjust the threshold of detection. After the implementation of this AKI-EWS, the incidence of AKI fell. The proportion of AKI > 4% was reduced significantly (47.7% and 41.6%, p = 0.010) in patients with serum creatinine measured. The proportion of AKI > 0.9% also dropped significantly (51.67% and 35.94%, p = 0.024) in all inpatients. Trends of AKI outcomes also showed improvement. The loading of consultation of nephrologists decreased by 15.5%. Conclusions: Through well-designed AKI-EWS, the incidence of AKI dropped, showing improved outcomes. The factors affecting benefits from AKI-EWS included high-risk identification (individual threshold detection), timely and automatic diagnosis, real-time alerting on electronic health information systems, fast self-diagnosing of the cause of AKI, and coverage of all inpatients.

Effects of perioperative erythropoietin administration on acute kidney injury and red blood cell transfusion in patients undergoing cardiac surgery: A systematic review and meta-analysis

BACKGROUND

The renoprotective effects of erythropoietin (EPO) are well-known; however, the optimal timing of EPO administration remains controversial. Red blood cell (RBC) transfusion is an independent risk factor for cardiac surgery-associated acute kidney injury (CSA-AKI). We aimed to evaluate the efficacy of EPO on CSA-AKI and RBC transfusion according to the timing of administration.

METHODS

We searched the Cochrane Library, EMBASE, and MEDLINE databases for randomized controlled trials. The primary outcome was the incidence of CSA-AKI following perioperative EPO administration, and the secondary outcomes were changes in serum creatinine, S-cystatin C, S-neutrophil gelatinase-associated lipocalin, urinary neutrophil gelatinase-associated lipocalin, length of hospital and intensive care unit (ICU) stay, volume of RBC transfusion, and mortality. The subgroup analysis was stratified according to the timing of EPO administration in relation to surgery.

RESULTS

Eight randomized controlled trials with 610 patients were included in the study. EPO administration significantly decreased the incidence of CSA-AKI (odds ratio: 0.60, 95% confidence interval [CI]: 0.43-0.85, P = .004; I2 = 52%; P for heterogeneity = .04), intra-operative RBC transfusion (standardized mean difference: -0.30, 95% CI: -0.55 to -0.05, P = .02; I2 = 15%, P for heterogeneity = .31), and hospital length of stay (mean difference: -1.54 days, 95% CI: -2.70 to -0.39, P = .009; I2 = 75%, P for heterogeneity = .001) compared with control groups. Subgroup analyses revealed that pre-operative EPO treatment significantly reduced the incidence of CSA-AKI, intra-operative RBC transfusion, serum creatinine, and length of hospital and ICU stay.

CONCLUSION

Pre-operative administration of EPO may reduce the incidence of CSA-AKI and RBC transfusion, but not in patients administered EPO during the intra-operative or postoperative period. Therefore, pre-operative EPO treatment can be considered to improve postoperative outcomes by decreasing the length of hospital and ICU stay in patients undergoing cardiac surgery.

Use of Ultra High Performance Liquid Chromatography with High Resolution Mass Spectrometry to Analyze Urinary Metabolome Alterations Following Acute Kidney Injury in Post-Cardiac Surgery Patients

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Cardiac surgery-associated AKI results in dramatic changes in urinary metabolome.

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Urinary metabolite disorder observed in patients with cardiac surgery-associated AKI.

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When metaboloite disorder was due to ischaemia and medical treatment, kidneys could return to normal.

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This work provides data about urinary metabolic profiles and resources for further research on AKI.

Background

Cardiac surgery-associated acute kidney injury (AKI) can increase the mortality and morbidity, and the incidence of chronic kidney disease, in critically ill survivors. The purpose of this research was to investigate possible links between urinary metabolic changes and cardiac surgery-associated AKI.

Methods

Using ultra-high-performance liquid chromatography coupled with Q-Exactive Orbitrap mass spectrometry, non-targeted metabolomics was performed on urinary samples collected from groups of patients with cardiac surgery-associated AKI at different time points, including Before_AKI (uninjured kidney), AKI_Day1 (injured kidney) and AKI_Day14 (recovered kidney) groups. The data among the three groups were analyzed by combining multivariate and univariate statistical methods, and urine metabolites related to AKI in patients after cardiac surgery were screened. Altered metabolic pathways associated with cardiac surgery-induced AKI were identified by examining the Kyoto Encyclopedia of Genes and Genomes database.

Results

The secreted urinary metabolome of the injured kidney can be well separated from the urine metabolomes of uninjured or recovered patients using multivariate and univariate statistical analyses. However, urine samples from the AKI_Day14 and Before_AKI groups cannot be distinguished using either of the two statistical analyses. Nearly 4000 urinary metabolites were identified through bioinformatics methods at Annotation Levels 1–4. Several of these differential metabolites may also perform essential biological functions. Differential analysis of the urinary metabolome among groups was also performed to provide potential prognostic indicators and changes in signalling pathways. Compared with the uninjured kidney group, the patients with cardiac surgery-associated AKI displayed dramatic changes in renal metabolism, including sulphur metabolism and amino acid metabolism.

Conclusions

Urinary metabolite disorder was observed in patients with cardiac surgery-associated AKI due to ischaemia and medical treatment, and the recovered patients’ kidneys were able to return to normal. This work provides data on urine metabolite markers and essential resources for further research on AKI.

Machine Learning Prediction Model for Acute Renal Failure After Acute Aortic Syndrome Surgery

Background

Acute renal failure (ARF) is the most common major complication following cardiac surgery for acute aortic syndrome (AAS) and worsens the postoperative prognosis. Our aim was to establish a machine learning prediction model for ARF occurrence in AAS patients.

Methods

We included AAS patient data from nine medical centers (n = 1,637) and analyzed the incidence of ARF and the risk factors for postoperative ARF. We used data from six medical centers to compare the performance of four machine learning models and performed internal validation to identify AAS patients who developed postoperative ARF. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve was used to compare the performance of the predictive models. We compared the performance of the optimal machine learning prediction model with that of traditional prediction models. Data from three medical centers were used for external validation.

Results

The eXtreme Gradient Boosting (XGBoost) algorithm performed best in the internal validation process (AUC = 0.82), which was better than both the logistic regression (LR) prediction model (AUC = 0.77, p < 0.001) and the traditional scoring systems. Upon external validation, the XGBoost prediction model (AUC =0.81) also performed better than both the LR prediction model (AUC = 0.75, p = 0.03) and the traditional scoring systems. We created an online application based on the XGBoost prediction model.

Conclusions

We have developed a machine learning model that has better predictive performance than traditional LR prediction models as well as other existing risk scoring systems for postoperative ARF. This model can be utilized to provide early warnings when high-risk patients are found, enabling clinicians to take prompt measures.

The impact of relative hypotension on acute kidney injury progression after cardiac surgery: a multicenter retrospective cohort study

BACKGROUND

Cardiac surgery is performed worldwide, and acute kidney injury (AKI) following cardiac surgery is a risk factor for mortality. However, the optimal blood pressure target to prevent AKI after cardiac surgery remains unclear. We aimed to investigate whether relative hypotension and other hemodynamic parameters after cardiac surgery are associated with subsequent AKI progression.

METHODS

We retrospectively enrolled adult patients admitted to 14 intensive care units after elective cardiac surgery between January and December 2018. We defined mean perfusion pressure (MPP) as the difference between mean arterial pressure (MAP) and central venous pressure (CVP). The main exposure variables were time-weighted-average MPP-deficit (i.e., the percentage difference between preoperative and postoperative MPP) and time spent with MPP-deficit > 20% within the first 24 h. We defined other pressure-related hemodynamic parameters during the initial 24 h as exploratory exposure variables. The primary outcome was AKI progression, defined as one or more AKI stages using Kidney Disease: Improving Global Outcomes' creatinine and urine output criteria between 24 and 72 h. We used multivariable logistic regression analyses to assess the association between the exposure variables and AKI progression.

RESULTS

Among the 746 patients enrolled, the median time-weighted-average MPP-deficit was 20% [interquartile range (IQR): 10-27%], and the median duration with MPP-deficit > 20% was 12 h (IQR: 3-20 h). One-hundred-and-twenty patients (16.1%) experienced AKI progression. In the multivariable analyses, time-weighted-average MPP-deficit or time spent with MPP-deficit > 20% was not associated with AKI progression [odds ratio (OR): 1.01, 95% confidence interval (95% CI): 0.99-1.03]. Likewise, time spent with MPP-deficit > 20% was not associated with AKI progression (OR: 1.01, 95% CI 0.99-1.04). Among exploratory exposure variables, time-weighted-average CVP, time-weighted-average MPP, and time spent with MPP < 60 mmHg were associated with AKI progression (OR: 1.12, 95% CI 1.05-1.20; OR: 0.97, 95% CI 0.94-0.99; OR: 1.03, 95% CI 1.00-1.06, respectively).

CONCLUSIONS

Although higher CVP and lower MPP were associated with AKI progression, relative hypotension was not associated with AKI progression in patients after cardiac surgery. However, these findings were based on exploratory investigation, and further studies for validating them are required. Trial Registration UMIN-CTR, https://www.umin.ac.jp/ctr/index-j.htm , UMIN000037074.

Cardiac Surgery Associated AKI Prevention Strategies and Medical Treatment for CSA-AKI

Acute kidney injury (AKI) is common after cardiac surgery. To date, there are no specific pharmacological therapies. In this review, we summarise the existing evidence for prevention and management of cardiac surgery-associated AKI and outline areas for future research. Preoperatively, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers should be withheld and nephrotoxins should be avoided to reduce the risk. Intraoperative strategies include goal-directed therapy with individualised blood pressure management and administration of balanced fluids, the use of circuits with biocompatible coatings, application of minimally invasive extracorporeal circulation, and lung protective ventilation. Postoperative management should be in accordance with current KDIGO AKI recommendations.

Derivation and validation of a model to predict acute kidney injury following cardiac surgery in patients with normal renal function

BACKGROUND

The study aimed to construct a clinical model based on preoperative data for predicting acute kidney injury (AKI) following cardiac surgery in patients with normal renal function.

METHODS

A total of 22,348 consecutive patients with normal renal function undergoing cardiac surgery were enrolled. Among them, 15,701 were randomly selected for the training group and the remaining for the validation group. To develop a model visualized as a nomogram for predicting AKI, logistic regression was performed with variables selected using least absolute shrinkage and selection operator regression. The discrimination, calibration, and clinical value of the model were evaluated.

RESULTS

The incidence of AKI was 25.2% in the training group. The new model consisted of nine preoperative variables, including age, male gender, left ventricular ejection fraction, hypertension, hemoglobin, uric acid, hypomagnesemia, and oral renin-angiotensin system inhibitor and non-steroidal anti-inflammatory drug within 1 week before surgery. The model had a good performance in the validation group. The discrimination was good with an area under the receiver operating characteristic curve of 0.740 (95% confidence interval, 0.726-0.753). The calibration plot indicated excellent agreement between the model prediction and actual observations. Decision curve analysis also showed that the model was clinically useful.

CONCLUSIONS

The new model was constructed based on nine easily available preoperative clinical data characteristics for predicting AKI following cardiac surgery in patients with normal kidney function, which may help treatment decision-making, and rational utilization of medical resources.

Improved creatinine-based early detection of acute kidney injury after cardiac surgery

 

OBJECTIVES

This study aims to improve early detection of cardiac surgery-associated acute kidney injury (CSA-AKI) compared to classical clinical scores.

METHODS

Data from 7633 patients who underwent cardiac surgery between 2008 and 2018 in our institution were analysed. CSA-AKI was defined according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria. Cleveland Clinical Score served as the reference with an area under the curve (AUC) 0.65 in our cohort. Based on that, stepwise logistic regression modelling was performed on the training data set including creatinine (Cr), estimated glomerular filtration rate (eGFR) levels and deltas (ΔCr, ΔeGFR) at different time points and clinical parameters as preoperative haemoglobin, intraoperative packed red blood cells (units) and cardiopulmonary bypass time (min) to predict CSA-AKI in the early postoperative course. The AUC was determined on the validation data set for each model respectively.

RESULTS

Incidence of CSA-AKI in the early postoperative course was 22.4% (n = 1712). The 30-day mortality was 12.5% in the CSA-AKI group (n = 214) and in the no-CSA-AKI group 0.9% (n = 53) (P < 0.001). Logistic regression models based on Cr and its delta gained an AUC of 0.69; 'Model eGFRCKD-EPI' an AUC of 0.73. Finally, 'Model DynaLab' including dynamic laboratory parameters and clinical parameters as haemoglobin, packed red blood cells and cardiopulmonary bypass time improved AUC to 0.84.

CONCLUSIONS

Model DynaLab' improves early detection of CSA-AKI within 12 h after surgery. This simple Cr-based framework poses a fundament for further endeavours towards reduction of CSA-AKI incidence and severity.

ACUTE KIDNEY INJURY AFTER OPEN-HEART SURGERY PROCEDURES

Cardiac surgery-associated acute kidney injury (CS-AKI) is a major complication associated with increased morbidity and mortality. There are multiple diagnostic criteria for CS-AKI. Despite many new investigations available for improved AKI diagnostics, creatinine and urea remain the cornerstone of diagnostics in everyday clinical practice. There are three major pathophysiological mechanisms that contribute to kidney injury, i.e. renal hypoperfusion, inflammation with oxidative stress, and use of nephrotoxic agents. Some risk factors have been identified that can be modified during the course of treatment (use of nephrotoxic agents, duration of cardiopulmonary bypass, type of extracorporeal circulation, postoperative low cardiac output or hypotension). The aim of AKI prevention should always be to prevent aggravation of renal failure and, if possible, to avoid progression to renal replacement therapy, which in turn brings worse long-term outcomes.

Acute Kidney Injury in Cardiac Surgery

Acute kidney injury (AKI) occurs frequently after cardiac surgery and is associated with high morbidity and mortality. Although the number of cardiac surgical procedures is constantly growing worldwide, incidence of cardiac surgery-associated AKI is still around 40% and has a significant impact on global health care costs. Numerous trials attempted to identify strategies to prevent AKI and attenuate its detrimental consequences. Effective options remained elusive. Current evidence supports a multimodal risk-stratification approach with biomarker-guided management of high-risk patients, perioperative administration of dexmedetomidine, and implementation of a care bundle as recommended by the Kidney Disease: Improving Global Outcomes group.

Association between transfusion of blood products and acute kidney injury following cardiac surgery

BACKGROUND

Acute kidney injury (AKI) is a serious complication following cardiac surgery associated with increased mortality. Red blood cell transfusion enhances the risk of developing AKI. However, the impact of other blood products on AKI is virtually unexplored. The aim of this study was to explore if transfusion of red blood cells, fresh frozen plasma and platelets alone or in combination were associated with postoperative AKI.

METHODS

Patients undergoing elective on-pump cardiac surgery were included (n = 1960) between 2012 to 2014. Transfusion data were collected intraoperatively and until the first postoperative day. AKI was classified according to the KDIGO criteria. Data were analysed using univariate and stepwise multiple logistic regression with adjustment for clinical risk factors and complementary blood products.

RESULTS

AKI was observed in 542 patients (27.7%). In univariate analysis and following adjustment for clinical risk factors, administration of red blood cells, freshfrozen plasma and platelets were all independently associated with KDIGO stage 2-3. Following additional adjustment for complementary blood products, only red blood cell transfusion remained significantly associated with AKI. A dose-dependent association between volume of red blood cells and degree of AKI severity was observed.

CONCLUSION

Transfusion of all blood products in a dose-dependent manner increased the risk for AKI. However, in multivariate analysis combining all blood products, only red blood cell transfusion remained significantly associated with AKI development.

Hematocrit as a predictor of preoperative transfusion-associated complications in spine surgery: A NSQIP study

BACKGROUND CONTEXT

Preoperative optimization of medical comorbidities prior to spinal surgery is becoming an increasingly important intervention in decreasing postoperative complications and ensuring a satisfactory postoperative course. The treatment of preoperative anemia is based on guidelines made by the American College of Cardiology (ACC), which recommends packed red blood cell transfusion when hematocrit is less than 21% in patients without cardiovascular disease and 24% in patients with cardiovascular disease. The literature has yet to quantify the risk profile associated with preoperative pRBC transfusion.

PURPOSE

To determine the incidence of complications following preoperative pRBC transfusion in a cohort of patients undergoing spine surgery.

STUDY DESIGN

Retrospective review of a national surgical database.

PATIENT SAMPLE

The national surgical quality improvement program database OUTCOME NEASURES: Postoperative physiologic complications after a preoperative transfusion. Complications were defined as the occurrence of any DVT, PE, stroke, cardiac arrest, myocardial infarction, longer length of stay, need for mechanical ventilation greater than 48 h, surgical site infections, sepsis, urinary tract infections, pneumonia, or higher 30-day mortality.

METHODS

The national surgical quality improvement program database was queried, and patients were included if they had any type of spine surgery and had a preoperative transfusion.

RESULTS

Preoperative pRBC transfusion was found to be protective against complications when the hematocrit was less than 20% and associated with more complications when the hematocrit was higher than 20%. In patients with a hematocrit higher than 20%, pRBC transfusion was associated with longer lengths of stay, and higher rates of ventilator dependency greater than 48 h, pneumonia, and 30-day mortality.

CONCLUSION

This is the first study to identify an inflection point in determining when a preoperative pRBC transfusion may be protective or may contribute to complications. Further studies are needed to be conducted to stratify by the prevalence of cardiovascular disease.

Clinical and Operative Determinants of Acute Kidney Injury after Cardiac Surgery

INTRODUCTION

Cardiac surgery-associated acute kidney injury (CSA-AKI) is associated with increased morbidity and mortality.

OBJECTIVES

We aimed to identify potentially modifiable risk factors for CSA-AKI.

METHODS

This was asingle-center retrospective cohort study of 495 adult patients undergoing cardiac surgery. AKI was diagnosed and staged using full KDIGO criteria incorporating baseline serum creatinine (SC) levels and correction of postoperative SC levels for fluid balance. We examined the association of routinely available clinical and laboratory data with AKI using multivariate logistic regression modeling.

RESULTS

A total of 103 (20.8%) patients developed AKI: 16 (15.5%) patients were diagnosed with AKI upon hospital admission, and 87 (84.5%) patients were diagnosed with CSA-AKI. Correction of SC levels for fluid balance increased the number of AKI cases to 104 (21.0%), with 6 patients categorized to different AKI stages. Univariate logistic regression analysis identified five preoperative (age, sex, diabetes mellitus, preoperative systolic pulmonary arterial pressure [PSPAP], acute decompensated heart failure) and five intraoperative predictors of AKI (age, sex, red blood cell [RBC] volume transfused, use of minimally invasive surgery, duration of cardiopulmonary bypass). When all preoperative and intraoperative variables were incorporated into one model, six predictors remained significant (age, sex, use of minimally invasive surgery, RBC volume transfused, PSPAP, duration of cardiopulmonary bypass). Model discrimination performance showed an area under the curve of 0.69 for the model including only preoperative variables, 0.76 for the model including only intraoperative variables, and 0.77 for the model including all preoperative and intraoperative variables.

CONCLUSIONS

Use of minimally invasive surgery and therapies mitigating PSPAP and intraoperative blood loss may offer protection against CSA-AKI.

Acute Kidney Injury Associated with Cardiac Surgery: a Comprehensive Literature Review

Objective

To comprehensively understand cardiac surgeryassociated acute kidney injury (CSA-AKI) and methods of prevention of such complication in cardiac surgery patients.

Methods

A comprehensive literature search was performed using the electronic database to identify articles describing acute kidney injury (AKI) in patients that undergone cardiac surgery. There was neither time limit nor language limit on the search. The results were narratively summarized.

Results

All the relevant articles have been extracted; results have been summarized in each related section. CSA-AKI is a serious postoperative complication and it can contribute to a significant increase in perioperative morbidity and mortality rates. Optimization of factors that can reduce CSA-AKI, therefore, contributes to a better postoperative outcome.

Conclusion

Several factors can significantly increase the rate of AKI; identification and minimization of such factors can lead to lower rates of CSA-AKI and lower perioperative morbidity and mortality rates.

Prevention of Cardiac Surgery-Associated Acute Kidney Injury: A Review of Current Strategies

Acute kidney injury is a common and often severe postoperative complication after cardiac surgery, and is associated with poor short-term and long-term outcomes. Numerous randomized controlled trials have been conducted to investigate various strategies for prevention of cardiac surgery-associated acute kidney injury. Unfortunately, most trials that have been conducted to date have been negative. However, encouraging results have been demonstrated with preoperative administration of corticosteroids, leukocyte filtration, and administration of inhaled nitric oxide intraoperatively, and implementation of a Kidney Disease: Improving Global Outcomes bundle of care approach postoperatively. These findings require validation in large, multicenter trials.

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.

Acute kidney injury following left ventricular assist device implantation: Contemporary insights and future perspectives

Currently, an increasing number of patients with end-stage heart failure are being treated with left ventricular assist device (LVAD) therapy as bridge-to-transplantation, bridge-to-candidacy, or destination therapy (DT). Potential life-threatening complications may occur, specifically in the early post-operative phase, which positions LVAD implantation as a high-risk surgical procedure. Acute kidney injury (AKI) is a frequently observed complication after LVAD implantation and is associated with high morbidity and mortality. The rapidly growing number of LVAD implantations necessitates better approaches of identifying high-risk patients, optimizing peri-operative management, and preventing severe complications such as AKI. This holds especially true for those patients receiving an LVAD as DT, who are typically older (with higher burden of comorbidities) with impaired renal function and at increased post-operative risk. Herein we outline the definition, diagnosis, frequency, pathophysiology, and risk factors for AKI in patients with an LVAD. We also review possible strategies to prevent and manage AKI in this patient population.

Development of a practical prediction score for chronic kidney disease after cardiac surgery

BACKGROUND

Chronic kidney disease (CKD) is a frequent and serious complication of cardiac surgery. This study was designed to establish a scoring system, calculated in the immediate postoperative period, to assess the risk of CKD at 1 yr in patients undergoing cardiac surgery with cardiopulmonary bypass.

METHODS

We conducted a cohort study including patients with preoperative estimated glomerular filtration rate above 60 ml min^-1 (1.73 m)^-2 who underwent cardiac surgery with cardiopulmonary bypass. We identified risk factors for de novo CKD at 1 yr using logistic regression. We derived a risk score for CKD, and externally validated this score in a second cohort.

RESULTS

The incidence of CKD was 18% and 23% in the derivation and validation cohorts, respectively. We developed a scoring system that included (i) the occurrence of postoperative acute kidney injury according to the Kidney Disease: Improving Global Outcomes criteria, (ii) age older than 65 yr, (iii) preoperative glomerular filtration rate <80 ml min^-1 (1.73 m)^-2, (iv) aortic cross-clamping time longer than 50 min, and (v) the type of surgery (aortic or cardiac transplantation). This score predicted CKD with good accuracy (area under the receiver operating characteristic curve: 0.81; 95% confidence interval: 0.77-0.86 in the derivation cohort), and with fair accuracy in the validation cohort (area under the receiver operating characteristic curve: 0.78; 95% confidence interval: 0.72-0.83).

CONCLUSIONS

We provide an easy-to-calculate scoring system to identify patients at high risk of developing CKD after cardiac surgery with cardiopulmonary bypass. This system might help clinicians to target more accurately patients requiring monitoring of renal function after cardiac surgery, and to design appropriate interventional trials aimed at preventing CKD or mitigating its consequences.

Prevention of Acute Kidney Injury in Children Undergoing Cardiac Surgery: A Narrative Review

Children undergoing cardiac surgery are at risk of developing acute kidney injury (AKI). Preventing cardiac surgery-associated AKI (CS-AKI) is important as it is associated with increased early- and long-term mortality and morbidity. Targeting modifiable risk factors (eg, avoiding poor renal perfusion, nephrotoxic drugs, and fluid overload) reduces the risk of CS-AKI. There is currently no strong evidence for the routine use of pharmacological approaches (eg, aminophylline, dexmedetomidine, fenoldopam, and steroids) to prevent CS-AKI. There is robust evidence to support the role of early peritoneal dialysis as a nonpharmacologic approach to prevent CS-AKI.

Impact of major bleeding on the risk of acute kidney injury in patients undergoing off-pump coronary artery bypass grafting

Background

Patients with perioperative bleeding during cardiac surgery are susceptible to acute kidney injury (AKI) which is proposed to be associated with short-term and long-term risk of adverse events. The relationship between perioperative bleeding in off-pump coronary artery bypass grafting (OPCAB) and AKI remains unknown. The purpose of this study is to evaluate the impact of perioperative bleeding on the risk of postoperative AKI in patient undergoing OPCAB.

Methods

Perioperative major bleeding was defined by the universal definition of perioperative bleeding (UDPB) class 3 to 4. The primary endpoint was postoperative AKI which was diagnosed using criteria of stage 1 of AKI proposed by Acute Kidney Injury Network (AKIN). The secondary endpoints included in-hospital mortality and the incidence of postoperative myocardial infarction (MI). Baseline characteristics were compared between patients with and without major bleeding. Multivariable logistic regression analysis was performed to identify potential predictive factors for AKI after OPCAB.

Results

A total of 4,030 ACS (acute coronary syndrome) patients who underwent OPCAB were included in this study. Major bleeding rate was 9.8% (n =394). AKI was found in 995 (24.7%) patients. Multivariable regression analysis showed that perioperative major bleeding conferred a significantly higher risk of AKI after OPCAB with an odds ratio of 1.67 (95% confidence interval 1.32-2.10, P<0.001). When a decrease in hemoglobin, transfusion and chest tube output were included in the same logistic model separately to replace major bleeding, transfusion was the most strongly risk factor associated with AKI after surgery (OR =2.08, 95% CI: 1.38-3.16, P<0.001).

Conclusions

Perioperative bleeding is associated with a higher risk of postoperative AKI in ACS patients who underwent OPCAB. Moreover, blood and blood products transfusion most correlated with AKI after surgery. Prevention of severe bleeding and reducing blood transfusion requirement may improve the outcomes of OPCAB.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

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

A model-based cost-effectiveness analysis of Patient Blood Management

BACKGROUND

Patient blood management (PBM) is a multidisciplinary concept focused on the management of anaemia, minimisation of iatrogenic blood loss and rational use of allogeneic blood products. The aims of this study were: (i) to analyse post-operative outcome in patients with liberal vs restrictive exposure to allogeneic blood products and (ii) to evaluate the cost-effectiveness of PBM in patients undergoing surgery.

MATERIALS AND METHODS

A systematic literature review and meta-analysis were performed to compare post-operative complications in predominantly non-transfused patients (restrictive transfusion group) and patients who received one to three units of red blood cells (liberal transfusion group). Outcome measures included sepsis with/without pneumonia, acute renal failure, acute myocardial infarction and acute stroke. In a second step, a health economic model was developed to calculate cost-effectiveness of PBM (PBM-arm vs control-arm) for simulated cohorts of 10,000 cardiac and non-cardiac surgical patients based on the results of the meta-analysis and costs.

RESULTS

Out of 478 search results, 22 studies were analysed in the meta-analysis. The pooled relative risk of any complication in the restrictive transfusion group was 0.43 for non-cardiac and 0.34 for cardiac surgical patients. In the simulation model, PBM was related to reduced complications (1,768 vs 1,245) and complication-related deaths (411 vs 304) compared to standard care. PBM-related costs of therapy exceeded costs of the control arm by € 150 per patient. However, total costs, including hospitalisation, were higher in the control-arm for both non-cardiac (€ 2,885.11) and cardiac surgery patients (€ 1,760.69). The incremental cost-effectiveness ratio including hospitalisation showed savings of € 30,458 (non-cardiac and cardiac surgery patients) for preventing one complication and € 128,023 (non-cardiac and cardiac surgery patients) for prevention of one complication-related death in the PBM-arm.

DISCUSSION

Our results indicate that PBM may be associated with fewer adverse clinical outcomes compared to control management and may, thereby, be cost-effective.

Risk model for deaths and renal replacement therapy dependence in patients with acute kidney injury after cardiac surgery

OBJECTIVES

Acute kidney injury (AKI) is a serious complication after cardiac surgery and is associated with increased in-hospital deaths. Renal replacement therapy (RRT) is becoming a routine strategy for severe AKI. Our goal was to evaluate the risk factors for death and RRT dependence in patients with AKI after cardiac surgery.

METHODS

We included 190 eligible adult patients who had AKI following cardiac surgery and who required RRT at our centre from November 2010 to March 2015. We collected preoperative, intraoperative, postoperative and RRT data for all patients.

RESULTS

In this cohort, 87 patients had successful RRT in the hospital, whereas 103 patients had RRT that failed (70 deaths and 33 cases of RRT dependence). The multivariable logistic analysis identified old age [odds ratio (OR): 1.042, 95% confidence interval (CI): 1.012-1.074; P = 0.011], serum uric acid (OR: 1.015, 95% CI: 1.003-1.031; P = 0.024), intraoperative concentrated red blood cell transfusions (OR: 1.144, 95% CI: 1.006-1.312; P = 0.041), postoperative low cardiac output syndrome (OR: 3.107, 95% CI: 1.179-8.190; P = 0.022) and multiple organ failure (OR: 5.786, 95% CI: 2.115-15.832; P = 0.001) as factors associated with a higher risk for RRT failure. The prediction model (-4.3 + 0.002 × preuric acid + 0.10 × concentrated red blood cells + 0.04 × age + 1.12 × [low cardiac output syndrome = 1] + 1.67 × [multiple organ failure = 1]) based on the multivariate analysis had statistically significant different incriminatory power with an area under the curve of 0.786.

CONCLUSIONS

The prediction model may serve as a simple, accurate tool for predicting in-hospital RRT failure for patients with AKI following cardiac surgery.

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

Introduction:

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

Methods:

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

Results:

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

Conclusions:

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

Cardiac surgery-associated acute kidney injury

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a well-recognized complication resulting with the higher morbid-mortality after cardiac surgery. In its most severe form, it increases the odds ratio of operative mortality 3-8-fold, length of stay in the Intensive Care Unit and hospital, and costs of care. Early diagnosis is critical for an optimal treatment of this complication. Just as the identification and correction of preoperative risk factors, the use of prophylactic measures during and after surgery to optimize renal function is essential to improve postoperative morbidity and mortality of these patients. Cardiopulmonary bypass produces an increased in tubular damage markers. Their measurement may be the most sensitive means of early detection of AKI because serum creatinine changes occur 48 h to 7 days after the original insult. Tissue inhibitor of metalloproteinase-2 and insulin-like growth factor-binding protein 7 are most promising as an early diagnostic tool. However, the ideal noninvasive, specific, sensitive, reproducible biomarker for the detection of AKI within 24 h is still not found. This article provides a review of the different perspectives of the CSA-AKI, including pathogenesis, risk factors, diagnosis, biomarkers, classification, postoperative management, and treatment. We searched the electronic databases, MEDLINE, PubMed, EMBASE using search terms relevant including pathogenesis, risk factors, diagnosis, biomarkers, classification, postoperative management, and treatment, in order to provide an exhaustive review of the different perspectives of the CSA-AKI.

Reassessment of Acute Kidney Injury after Cardiac Surgery: A Retrospective Study

Objective To evaluate the incidence, risk, or protective factors of acute kidney injury (AKI) in patients after cardiac surgery based on the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Methods A retrospective analysis of 2,575 patients undergoing their first documented cardiac surgery with cardiopulmonary bypass (CPB) was conducted. Perioperative variables were collected and analyzed. Univariate and multiple logistic regression models were used for determining the association between the development of AKI and risk factors. Multiple Cox-proportional hazards modeling was performed to evaluate the impact of AKI on the mortality in the intensive care unit and hospital length of stay. Results Of 2,575 patients, 931 (36%) developed AKI. A total of 30 (1.2%) patients required renal replacement therapy. In the multivariate analysis, mechanical ventilation duration (OR1.446, 95% CI 1.195-1.749, p<0.001), CPB duration of ≥110 min (OR 1.314, 95% CI 1.072-1.611, p=0.009), erythrocytes transfusion (OR 1.078, 95% CI 1.050-1.106, p<0.001), and postoperative body temperature greater than 38°C within 3 days (OR 1.234, 95% CI 1.018-1.496, p=0.032) were independent risk factors for CSA-AKI, while ulinastatin use was associated with a reduced incidence of CSA-AKI (OR 0.694, 95% CI 0.557-0.881, p=0.006). CSA-AKI was significantly associated with in-hospital mortality (adjusted HR: 2.218, 95% CI 1.161-4.238, p=0.016), especially in patients needing renal replacement therapy (adjusted HR: 18.683, 95% CI 8.579-40.684, p<0.001). Conclusion Mechanical ventilation duration, erythrocytes transfusion, and postoperative body temperature above 38°C within 3 days were considered independent risk factors for CSA-AKI. The use of ulinastatin was associated with a reduced incidence of CSA-AKI.