Predicting and preventing acute kidney injury after cardiac surgery

Risk factors and prognosis assessment for acute kidney injury: The 2020 consensus of the Taiwan AKI Task Force

Risk and prognostic factors for acute kidney injury (AKI) have been published in various studies across various populations. We aimed to explore recent advancements in and provide updated recommendations on AKI risk stratification and information about local AKI risk factors. The Taiwan Acute Kidney Injury Task Force reviewed relevant recently published literature and reached a consensus after group meetings. Systemic review and group discussion were performed. We conducted a meta-analysis according to the PRISMA statement for evaluating the diagnostic performance of the furosemide stress test. Several risk and susceptibility factors were identified through literature review. Contrast-associated AKI prediction models after coronary angiography were one of the most discussed prediction models we found. The basic approach and evaluation of patients with AKI was also discussed. Our meta-analysis found that the furosemide stress test can be used as a prognostic tool for AKI progression and to identify patients with AKI who are at low risk of renal replacement therapy. Factors associated with de novo chronic kidney injury or renal non-recovery after AKI were identified and summarized. Our review provided practical information about early identification of patients at high risk of AKI or disease progression for Taiwan local clinics.

Proinflammatory P2Y14 receptor inhibition protects against ischemic acute kidney injury in mice

Ischemic acute kidney injury (AKI), a complication that frequently occurs in hospital settings, is often associated with hemodynamic compromise, sepsis, cardiac surgery, or exposure to nephrotoxins. Here, using a murine renal ischemia/reperfusion injury (IRI) model, we show that intercalated cells (ICs) rapidly adopted a proinflammatory phenotype after IRI. Wwe demonstrate that during the early phase of AKI either blockade of the proinflammatory P2Y14 receptor located on the apical membrane of ICs or ablation of the gene encoding the P2Y14 receptor in ICs (a) inhibited IRI-induced increase of chemokine expression in ICs, (b) reduced neutrophil and monocyte renal infiltration, (c) reduced the extent of kidney dysfunction, and (d) attenuated proximal tubule damage. These observations indicate that the P2Y14 receptor participates in the very first inflammatory steps associated with ischemic AKI. In addition, we show that the concentration of the P2Y14 receptor ligand UDP-glucose (UDP-Glc) was higher in urine samples from intensive care unit patients who developed AKI compared with patients without AKI. In particular, we observed a strong correlation between UDP-Glc concentration and the development of AKI in cardiac surgery patients. Our study identifies the UDP-Glc/P2Y14 receptor axis as a potential target for the prevention and/or attenuation of ischemic AKI.

Renal replacement therapy: a practical update

Acute kidney injury (AKI) is defined as an abrupt decrease in kidney function, with the most severe form requiring some method of renal replacement therapy (RRT). The use of RRT is required in 5-10% of critically ill patients who develop severe AKI. Renal replacement therapy can be provided as either intermittent hemodialysis or one of the various modes of continuous renal replacement therapy (CRRT), with CRRT potentially conferring an advantage with respect to renal recovery and dialysis independence. There is no difference in mortality when comparing low (< 25 mL·kg^-1·hr^-1) vs high (> 40 mL·kg^-1·hr^-1) RRT dosing. Continuous renal replacement therapy may be run in different modes of increasing complexity depending on a given patient's clinical needs. Regional citrate anticoagulation is recommended as the therapy of choice for the majority of critically ill patients requiring CRRT.

Evaluation of the Effect of Aminophylline in Reducing the Incidence of Acute Kidney Injury After Cardiac Surgery

Objectives

Acute renal failure is a common complication of major cardiovascular surgeries (One-third of patients). Adenosine release as a vascular vasodilator increases after cardiac surgery, which reduces renal and glomerular blood flow and subsequently causes kidney ischemic damage. The present study aimed at evaluating the impact of aminophylline as an adenosine receptor antagonist on renal function after cardiac surgery hoping to find an appropriate method to reduce acute kidney injury.

Methods

The patients in the intervention group received 5 mg/kg aminophylline bolus after induction of anesthesia; then, 0.25 mg/kg/hr of the drug was administered intraoperatively and up to 48 hours after surgery in the ICU cardiac surgery. Similar volume of normal saline was injected to the patients of the second group. Serum BUN, Cr, and GFR were measured pre- and postoperatively and 3 days postsurgery. Patients’ 24- hour urine output and RIFLE were also calculated.

Results

Those patients who received medication were extubated earlier (P = 0.018) and received lower amount of inotropic drugs (P < 0001). According to the RIFLE criteria, most of the patients experienced no change or even improved GFR and Cr amounts compared to the control group (p < 0.05). GFR and Cr value of all the patients with Cleveland score, less and more than 6, showed a significant difference between the 2 groups (P = 0.001 and P = 0.01, respectively). According to the RIFLE criteria, most of the patients experienced no change or even improved GFR.

Conclusions

Aminophylline in cardiac surgery can reduce the frequency of acute kidney injury according to RIFLE criteria and could be used in the prevention of AKI as a safe and efficient modality in high-risk patients. Also, the use of this drug may reduce the need for inotropic medication at the time of surgery, intensive care unit stay length, and extubation time.

Latent variable modeling improves AKI risk factor identification and AKI prediction compared to traditional methods

Background

Acute kidney injury (AKI) is diagnosed based on postoperative serum creatinine change, but AKI models have not consistently performed well, in part due to the omission of clinically important but practically unmeasurable variables that affect creatinine. We hypothesized that a latent variable mixture model of postoperative serum creatinine change would partially account for these unmeasured factors and therefore increase power to identify risk factors of AKI and improve predictive accuracy.

Methods

We constructed a two-component latent variable mixture model and a linear model using data from a prospective, 653-subject randomized clinical trial of AKI following cardiac surgery (NCT00791648) and included established AKI risk factors and covariates known to affect serum creatinine. We compared model fit, discrimination, power to detect AKI risk factors, and ability to predict AKI between the latent variable mixture model and the linear model.

Results

The latent variable mixture model demonstrated superior fit (likelihood ratio of 6.68 × 10⁷¹) and enhanced discrimination (permutation test of Spearman’s correlation coefficients, p < 0.001) compared to the linear model. The latent variable mixture model was 94% (−13 to 1132%) more powerful (median [range]) at identifying risk factors than the linear model, and demonstrated increased ability to predict change in serum creatinine (relative mean square error reduction of 6.8%).

Conclusions

A latent variable mixture model better fit a clinical cohort of cardiac surgery patients than a linear model, thus providing better assessment of the associations between risk factors of AKI and serum creatinine change and more accurate prediction of AKI. Incorporation of latent variable mixture modeling into AKI research will allow clinicians and investigators to account for clinically meaningful patient heterogeneity resulting from unmeasured variables, and therefore provide improved ability to examine risk factors, measure mechanisms and mediators of kidney injury, and more accurately predict AKI in clinical cohorts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0465-1) contains supplementary material, which is available to authorized users.

Effects of N-acetyl cysteine on renal functions evaluated by blood neutrophil gelatinase-associated lipocalin levels in geriatric patients undergoing coronary artery bypass grafting

Objective:

Recent conflicting studies on the renal effects of N-acetyl cysteine (NAC) after cardiac surgery have been published. The aim of this study was to evaluate the renal effects of NAC using neutrophil gelatinase-associated lipocalin (NGAL) blood levels in elderly patients undergoing coronary artery bypass grafting (CABG).

Methods:

This randomized, double-blinded, placebo-controlled study was conducted among geriatric patients (>65 years) scheduled to undergo CABG. A total of 60 consecutive patients were randomly assigned to 2 groups. The first group received I.V. NAC (n=30) and the second group received placebo (n=30) at induction of anesthesia and then for 20 h. NGAL values were determined and conventional renal function tests were performed. Statistical analysis was performed using SPSS 17.0 (IL, Chicago, USA). A p value of <0.05 was considered statistically significant

Results:

Plasma creatinine levels at 24 h postoperatively were significantly higher in the placebo group than in the NAC group (1.41±0.63 vs. 1.13±0.35; p<0.05). The mean serum NGAL levels at 3 h postoperatively were higher in the placebo group than in the NAC group (104.94±30.51 vs. 87.82±25.18; p<0.05). NGAL levels were similar between the groups at all other measurement time points. Plasma creatinine levels of ≥1.5 mg/dL or >25% of the baseline value at any time during the study period were observed in 27% of patients in the NAC group and 37% of patients in the placebo group; the difference was statistically significant (p<0.05).

Conclusion:

In the present study, we found that I.V. NAC infusion in elderly patients undergoing CABG reduced the incidence of acute kidney injury as determined by blood NGAL and creatinine levels.

Clinical prediction scores for type 1 cardiorenal syndrome derived and validated in chinese cohorts

Type 1 cardiorenal syndrome is one of the major diseases threatening human life in China. The incidence of acute kidney injury (AKI) associated with acute heart failure (AHF), acute myocardial infarction (AMI), cardiac surgery, and coronary angiography has been reported to be 32.2, 14.7, 40.2, and 4.5%, respectively. In the past 2 years, we derived and validated 4 risk scores for the prediction of AKI associated with the above acute heart diseases as well as for examination and treatment in Chinese cohorts. A univariable comparison and a subsequent multivariate logistic regression analysis of the potential predictive variables of AKI in the derivation set were conducted and used to establish the prediction scores, which were then verified in the validation set. The area under the receiver operating characteristic (ROC) curve and the Hosmer-Lemeshow goodness-of-fit statistic test were performed to assess the discrimination and calibration of the prediction scores, respectively. These 4 prediction scores all showed adequate discrimination (area under the ROC curve, ≥0.70) and good calibration (p > 0.05). Both Forman's risk score (for AKI associated with AHF) and Mehran's risk score (for AKI associated with coronary angiography) are widely applied around the world. The external validation of these 2 risk scores was performed in our patients, but their discriminative power was quite low (area under the ROC curve, 0.65 and 0.57, respectively). Therefore, these prediction scores derived from Chinese cohorts might be more accurate than those derived from different races when they are applied in Chinese patients.

Intravascular administration of mannitol for acute kidney injury prevention: a systematic review and meta-analysis

BACKGROUND

The effects of mannitol administration on acute kidney injury (AKI) prevention remain uncertain, as the results from clinical studies were conflicting. Due to the lack of strong evidence, the KDIGO Guideline for AKI did not propose completely evidence-based recommendations on this issue.

METHODS

We searched PubMed, EMBASE, clinicaltrials.gov and Cochrane Controlled Trials Register. Randomized controlled trials on adult patients at increased risk of AKI were considered on the condition that they compared the effects of intravascular administration of mannitol plus expansion of intravascular volume with expansion of intravascular volume alone. We calculated pooled risk ratios, numbers needed to treat and mean differences with 95% confidence intervals for dichotomous data and continuous data, respectively.

RESULTS

Nine trials involving 626 patients were identified. Compared with expansion of intravascular volume alone, mannitol infusion for AKI prevention in high-risk patients can not reduce the serum creatinine level (MD 1.63, 95% CI -6.02 to 9.28). Subgroup analyses demonstrated that serum creatinine level is negatively affected by the use of mannitol in patients undergoing an injection of radiocontrast agents (MD 17.90, 95% CI 8.56 to 27.24). Mannitol administration may reduce the incidence of acute renal failure or the need of dialysis in recipients of renal transplantation (RR 0.34, 95% CI 0.21 to 0.57, NNT 3.03, 95% CI 2.17 to 5.00). But similar effects were not found in patients at high AKI risk, without receiving renal transplantation (RR 0.29, 95% CI 0.01 to 6.60).

CONCLUSIONS

Intravascular administration of mannitol does not convey additional beneficial effects beyond adequate hydration in the patients at increased risk of AKI. For contrast-induced nephropathy, the use of mannitol is even detrimental. Further research evaluating the efficiency of mannitol infusions in the recipients of renal allograft should be undertaken.

Predicting acute kidney injury after cardiac surgery: a systematic review

Acute kidney injury (AKI) after cardiac surgery confers a significant increased risk of death. Several risk models have been developed to predict postoperative kidney failure after cardiac surgery. This systematic review evaluated the available risk models for AKI after cardiac surgery. Literature searches were performed in the Web of Science/Knowledge, Scopus, and MEDLINE databases for articles reporting the primary development of a risk model and articles reporting validation of existing risk models for AKI after cardiac surgery. Data on model variables, internal or external validation (or both), measures of discrimination, and measures of calibration were extracted. The systematic review included 7 articles with a primary development of a prediction score for AKI after cardiac surgery and 8 articles with external validation of established models. The models for AKI requiring dialysis are the most robust and externally validated. Among the prediction rules for AKI requiring dialysis after cardiac surgery, the Cleveland Clinic model has been the most widely tested thus far and has shown high discrimination in most of the tested populations. A validated score to predict AKI not requiring dialysis is lacking. Further studies are required to develop risk models to predict milder AKI not requiring dialysis after cardiac surgery. Standardizing risk factor and AKI definitions will facilitate the development and validation of risk models predicting AKI.

Pathophysiology of ischemic acute kidney injury

Acute kidney injury (AKI) as a consequence of ischemia is a common clinical event leading to unacceptably high morbidity and mortality, development of chronic kidney disease (CKD), and transition from pre-existing CKD to end-stage renal disease. Data indicate a close interaction between the many cell types involved in the pathophysiology of ischemic AKI, which has critical implications for the treatment of this condition. Inflammation seems to be the common factor that links the various cell types involved in this process. In this Review, we describe the interactions between these cells and their response to injury following ischemia. We relate these events to patients who are at high risk of AKI, and highlight the characteristics that might predispose these patients to injury. We also discuss how therapy targeting specific cell types can minimize the initial and subsequent injury following ischemia, thereby limiting the extent of acute changes and, hopefully, long-term structural and functional alterations to the kidney.

Preoperative renin-angiotensin system inhibitors protect renal function in aging patients undergoing cardiac surgery

BACKGROUND

Renal failure (RF) represents a major postoperative complication for elderly patients undergoing cardiac surgery. This observational cohort study examines effects of preoperative use of renin-angiotensin system (RAS) inhibitors on postoperative renal failure in aging patients undergoing cardiac surgery.

METHODS AND RESULTS

We retrospectively analyzed a cohort of 1287 patients who underwent cardiac surgery at this institution (2003-2007). The patients included were ≥65 years old, scheduled for elective cardiac surgery, and without preexisting RF (defined by the criteria of the Society of Thoracic Surgeons as described in Method). Of all patients evaluated, 346 patients met the inclusion criteria and were divided into two groups: using (n = 122) or not using (n = 224) preoperative RAS inhibitors. A comparison of the two groups showed no significant differences in baseline parameters, including creatinine clearance, body mass index, history of diabetes and smoking, preoperative medicines (except that more patients with RAS inhibitors had a history of hypertension or congestive heart failure, fewer RAS inhibitor patients had chronic lung disease), in intraoperative perfusion and aortic cross-clamp time, and in postoperative complications and 30-d mortality. Multivariate logistic regression analysis demonstrated, however, that preoperative RAS inhibitors significantly and independently reduced the incidence of postoperative RF in the patients undergoing cardiac surgery compared with those not taking RAS inhibitors: 1.6% versus 7.6%, yielding an odds ratio of 0.19 (95 % CI 0.04-0.84, P = 0.029).

CONCLUSIONS

Preoperative RAS inhibitors may have significant renoprotective effects for aging patients undergoing elective cardiac surgery.