Impact of N-acetylcysteine on contrast-induced nephropathy defined by cystatin C in patients with ST-elevation myocardial infarction undergoing primary angioplasty

Biomarkers in Contrast-Induced Acute Kidney Injury: Towards A New Perspective

Contrast-Induced Acute Kidney Injury (CI-AKI) remains a frequent iatrogenic condition since radiological procedures using intra-vascular iodinated contrast media (CM) are being widely administered for diagnostic and therapeutic purposes. Despite the improvement of the medical healthcare system worldwide, CI-AKI is still associated with direct short-term and indirect long-term outcomes including increased morbidity and mortality, especially in patients with underlying pre-existing renal function impairment, cardiovascular disease, or diabetes that could rapidly progress into Chronic Kidney Disease. Although the RIFLE (Risk, Injury, Failure, Loss, End-Stage Kidney Disease), AKIN (Acute Kidney Injury Network), and KDIGO (Kidney Disease Improving Global Outcomes) clinical criteria and recommendation guidelines are based on traditional "gold standard" biomarkers known as serum creatinine, glomerular filtration rate, and urinary output, new reliable serum and urinary biomarkers are still needed for an effective unified diagnostic strategy for AKI. Starting from previous and recent publications on the benefits and limitations of validated biomarkers responding to kidney injury, glomerular filtration, and inflammation among others, this review unravels the role of new emerging biomarkers used alone or in combination as reliable tools for early diagnosis and prognosis of CI-AKI, taking into account patients and procedures-risk factors towards a new clinical perspective.

The Association of Intraindividual Difference Between Cystatin- and Creatinine-Based Estimated GFR and Contrast-Associated Acute Kidney Injury

Purpose

The estimated glomerular filtration rate (eGFR) based on creatinine is crucial for the risk assessment of contrast-associated acute kidney injury (CA-AKI). In recent, the difference between cystatin C-based eGFR (eGFRcys) and creatinine-based eGFR (eGFRcr) has been widely documented. We aimed to explore whether intraindividual differences between eGFRcys and eGFRcr had potential value for CA-AKI risk assessment in patients undergoing elective percutaneous coronary intervention (PCI).

Patients and Methods

From January 2012 to December 2018, we retrospectively observed 5049 patients receiving elective PCI. To determine eGFR, serum creatinine and cystatin C levels were measured. CA-AKI was defined as serum creatinine being increased ≥ 50% or 0.3 mg/dL within 48 h after contrast agents exposure. Chronic kidney disease (CKD) was defined as the eGFR < 60 mL/min/1.73 m2.

Results

Approximately half of the participants (2479, 49.1%) had a baseline eGFRdiff (eGFRcys-eGFRcr) between -15 and 15 mL/min/1.73 m2. Restricted cubic splines analysis revealed a nonlinear relationship between eGFRdiff and CA-AKI. Multivariable logistic regression analysis indicated that compared with the reference group (-15 to 15 mL/min/1.73 m2), the negative-eGFRdiff group (less than -15 mL/min/1.73 m2) had a higher risk of CA-AKI (OR, 3.44; 95% CI, 2.57-4.64). Furthermore, patients were divided into four groups based on CKD identified by eGFRcys or eGFRcr. Multivariable logistic analysis revealed that patients with either CKDcys (OR, 2.94; 95% CI, 2.19-3.95, P < 0.001) or CKDcr (OR, 2.44; 95% CI, 1.19-4.63, P < 0.001) had an elevated risk of CA-AKI compared to those without CKDcys and CKDcr.

Conclusion

There are frequent intraindividual differences between eGFRcys and eGFRcr, and these differences can be used to forecast the risk of CA-AKI.

Meta-analytic Techniques to Assess the Association Between N-acetylcysteine and Acute Kidney Injury After Contrast Administration: A Systematic Review and Meta-analysis

IMPORTANCE

The most suitable analytic method to systematically analyze numerous trials with contradictory results is unclear. Multiple trials assessing the use of N-acetylcysteine (NAC) for prevention of contrast-induced acute kidney injury (CI-AKI) have had contradictory results with recent trials confirming a lack of benefit.

OBJECTIVE

To systematically review the literature on NAC for the prevention of CI-AKI, and to explore the heterogeneity, publication bias, and small-study effect to determine the most suitable analytic method in a setting where the literature is contradictory.

DATA SOURCES

Medline, Embase, and Cochrane Central Register of Controlled Trials databases were used to find randomized clinical trials (RCTs) comparing NAC with any other prophylactic agent or placebo in adults.

STUDY SELECTION

The search included studies published in English from database inception to January 2020. Two independent reviewers screened the studies, extracted data, and performed the risk of bias assessment.

DATA EXTRACTION AND SYNTHESIS

A meta-analysis was conducted about the effect of NAC on CI-AKI, the need for dialysis, and mortality. Fixed and random effects analyses were also performed. Funnel plots and the trim and fill method were used for assessment of publication bias. Metaregression was performed to explore the heterogeneity and subgroup analysis to examine the association between NAC and CI-AKI when studies were categorized according to sample size and number of events.

RESULTS

A total of 101 trials were included in this meta-analysis. The median sample size was 112 (range, 20 to 4993). Twenty-nine trials had a sample size of 200 or more, and only 3 trials had a sample size of 500 or more. Forty-five trials reported the need for kidney replacement therapy, and 41 trials reported mortality as an outcome. NAC seemed to show a benefit, with a pooled OR of 0.72 (95% CI, 0.63-0.82) using random effects model and a pooled OR of 0.82 (95% CI 0.76-0.90) using a fixed effects model. However, there was significant heterogeneity (I2 = 37.6; P < .001) and significant publication bias, which was reduced only when restricting to large RCTs (N ≥ 500). The clinical outcomes (ie, the need for kidney replacement therapy and mortality) revealed little heterogeneity and no publication bias, and each provided a robust neutral summary result.

CONCLUSIONS AND RELEVANCE

In this meta-analysis, NAC was associated with a benefit in the prevention of CI-AKI. However, because of substantial publication bias and other biases, standard meta-analytic techniques resulted in significant heterogeneity and a spurious, or factitious, association, even when using a random effects model. When the analysis was restricted to RCTs with a large sample size to account for publication bias or restricted to trials with clinical outcomes, this issue was reduced and resulted in more robust and neutral effect sizes.

High cystatin C levels predict long-term mortality in patients with ST-segment elevation myocardial infarction undergoing late percutaneous coronary intervention: A retrospective study

Objectives

Late percutaneous coronary intervention (PCI) in patients with ST‐segment elevation myocardial infarction (STEMI), defined as time of PCI > 7 days from symptom onset, is a common practice with clinical benefits. This study aimed to evaluate the predictive value of admission cystatin C (cys C) level on long‐term mortality in STEMI patients receiving late PCI.

Methods

Medical records of STEMI patients who were hospitalized between 2009 and 2011 from eight PCI‐capable hospitals in Northwest China were retrospectively analyzed. Cys C level ≥ 1.105 mg/L was considered as the best predictor of long‐term mortality based on the receiver‐operating characteristic analysis. Patients were followed up by phone or face‐to‐face interviews, and the long‐term mortality was obtained by reviewing medical records.

Results

The final analysis included 716 STEMI patients who received late PCI and had available cys C levels prior to PCI, and 524 were assigned into the high cys C group and 192 the low cys C group. Patients were followed up for an average length of 40.37 months. Compared with the low cys C group, the high cys C group had a higher long‐term all‐cause mortality (10.4% vs 2.9%, P < 0.001) and a higher cardiac mortality (6.8% vs 2.1%, P = 0.004). Multivariate Cox regression analysis showed that high cys C level was an independent predictor for both long‐term all‐cause mortality and cardiac mortality.

Conclusions

High cys C level at admission is an independent predictor of long‐term mortality in STEMI patients undergoing late PCI.

Periprocedural Concerns in the Patient with Renal Disease

Treating patients with kidney disease can be both a difficult and a complex process. Understanding how to care for patients who have kidney disease is essential for lowering perioperative as well as periprocedural morbidity and mortality. The primary aim in renal evaluation and care is to control and mitigate factors that may result in acute kidney injury (AKI) and/or cause further decline in renal function. It is essential for the foot and ankle specialist to recognize patients who are predisposed to developing or already have impairment of renal function.

Effectiveness of contrast-associated acute kidney injury prevention methods; a systematic review and network meta-analysis

BACKGROUND

Different methods to prevent contrast-associated acute kidney injury (CA-AKI) have been proposed in recent years. We performed a mixed treatment comparison to evaluate and rank suggested interventions.

METHODS

A comprehensive Systematic review and a Bayesian network meta-analysis of randomised controlled trials was completed. Results were tabulated and graphically represented using a network diagram; forest plots and league tables were shown to rank treatments by the surface under the cumulative ranking curve (SUCRA). A stacked bar chart rankogram was generated. We performed main analysis with 200 RCTs and three analyses according to contrast media and high or normal baseline renal profile that includes 173, 112 & 60 RCTs respectively.

RESULTS

We have included 200 trials with 42,273 patients and 44 interventions. The primary outcome was CI-AKI, defined as ≥25% relative increase or ≥ 0.5 mg/dl increase from baseline creatinine one to 5 days post contrast exposure. The top ranked interventions through different analyses were Allopurinol, Prostaglandin E1 (PGE1) & Oxygen (0.9647, 0.7809 & 0.7527 in the main analysis). Comparatively, reference treatment intravenous hydration was ranked lower but better than Placebo (0.3124 VS 0.2694 in the main analysis).

CONCLUSION

Multiple CA-AKI preventive interventions have been tested in RCTs. This network evaluates data for all the explored options. The results suggest that some options (particularly allopurinol, PGE1 & Oxygen) deserve further evaluation in a larger well-designed RCTs.

The Effect of Spironolactone on the Incidence of Contrast-Induced Nephropathy in Patients Undergoing Cardiac Catheterization: Study Design and Rationale

Introduction

Patients undergoing coronary catheterization are at high risk of developing contrast-induced nephropathy (CIN) acute kidney injury (AKI). Several approaches have been supposed to limit such an effect but with mixed results or non-practical methods. Spironolactone is supposed to be effective as a nephroprotective agent in animal studies. This study will try to measure the effect of spironolactone on the incidence of CIN-AKI in patients undergoing coronary catheterization (angiography angioplasty).

Methods

This study is a single-center, investigator-driven, double-blinded randomized controlled study in Iraq-Basra. More than 400 patients admitted for coronary angio unit in our center will be allocated in a 1:1 ratio to receive either spironolactone 200 mg single dose or placebo in addition to their usual premedication.

Planned Outcomes

Primary end point will be CIN defined as more than 25% or 0.3 mg/dl elevation in serum creatinine (S.Cr.) from baseline during the first 2–3 days after the procedure. We hope to identify or answer an important question regarding CIN in such high-risk patients.

Trial Registration

ClinicalTrials.gov Identifier, NCT03329443.

Predictive value of post-procedural early (within 24 h) increase in cystatin C for contrast-induced acute kidney injury and mortality following coronary angiography or intervention

Objective

To investigate the predictive value of post-procedural early (within 24 h) increase in cystatin C for contrast-induced acute kidney injury (CI-AKI) and all-cause mortality following coronary angiography or intervention.

Methods

We prospectively investigated 1042 consecutive patients with both baseline and early post-procedural cystatin C measurement undergoing coronary angiography or intervention. CI-AKI was defined as an increase ≥0.3 mg/dL or >50% in serum creatinine from baseline within 48 h post-procedure. Mean follow-up was 2.26 years.

Results

Overall, the patients had a CI-AKI incidence was 3.6% (38/1042), mean serum creatinine of 87 µmol/L. Compared with Mehran risk score, post-procedural early absolute increase (AUC: 0.584 vs. 0.706, P = 0.060) and relative increase (AUC: 0.585 vs. 0.706, P = 0.058) in cystatin C had poorer predictive value for CI-AKI. According to multivariate analysis, post-procedural significant early increase (≥0.3 mg/dL or ≥10%) in cystatin C developed in 231 patients (22.2%), was not independent predictor of CI-AKI (adjusted OR: 1.23, 95% CI, 0.56-2.69, P = 0.612), and long-term mortality (adjusted HR: 0.90; P = 0.838).

Conclusions

Our data suggested post-procedural early increase (within 24 h) in cystatin C was not effective for predicting CI-AKI or all-cause mortality following coronary angiography or intervention among patients at relative low risk of CI-AKI, the negative finding of poor predictive value should be further evaluated in larger multicenter trials.

Effectiveness of N-Acetylcysteine for the Prevention of Contrast-Induced Nephropathy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background

Conflicting results have been obtained in trials that have evaluated the prophylactic efficacy of N‐acetylcysteine (NAC) pretreatment in the prevention of contrast‐induced nephropathy (CIN). In this meta‐analysis of randomized controlled trials, we aimed to assess the effectiveness of NAC treatment for the prevention of CIN.

Methods and Results

PubMed, EMBASE, and the Cochrane Library were electronically searched from inception to January 2016 for all relevant studies. The weighted relative risk (RR) and corresponding 95% CI for incident CIN were estimated using random effects models. Standard methods for assessing statistical heterogeneity and publication bias were used. The study included 11 480 participants and 1653 cases of CIN. The incidence of CIN was 12.8% in the NAC group versus 16.0% in the control group (RR: 0.76, 95% CI: 0.66–0.88, P=0.0002). In the patients undergoing coronary angiography, the incidence of CIN in the NAC group versus the control group was 13.7% versus 17.2% (RR: 0.74, 95% CI: 0.63–0.87, P=0.0002); in those undergoing peripheral angiography, the incidence was 6.4% versus 5.8% (RR: 1.00, 95% CI: 0.42–2.40, P=1.00); in those undergoing computed tomography, the incidence was 7.7% versus 14.8% (RR: 0.51, 95% CI: 0.29–0.89, P=0.02).

Conclusions

Our meta‐analysis showed an inverse and significant association between NAC supplementation and risk of CIN in patients undergoing coronary angiography and computed tomography, while a protective role for NAC in patients undergoing peripheral angiography was not obvious.

Aggressive hydraTion in patients with ST-Elevation Myocardial infarction undergoing Primary percutaneous coronary intervention to prevenT contrast-induced nephropathy (ATTEMPT): Study design and protocol for the randomized, controlled trial, the ATTEMPT, RESCIND 1 (First study for REduction of contraSt-induCed nephropathy followINg carDiac catheterization) trial

Adequate hydration is recommended for acute ST-elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI) to prevent contrast-induced nephropathy (CIN). However, the optimal hydration regimen has not been well established in these high-risk patients. The objective of this study is to evaluate the efficacy of a preprocedural loading dose plus postprocedural aggressive hydration with normal saline guided by the left ventricular end-diastolic pressure (LVEDP) compared with general hydration for CIN prevention. The ATTEMPT study is a multicenter, open-label, investigator-driven, randomized controlled trial in China. Approximately 560 patients with STEMI undergoing primary PCI will be randomized (1:1) to receive either periprocedural general hydration (control group) or aggressive hydration (treatment group). Patients in the control group receive periprocedural general hydration with ≤500 mL normal saline (within 6 hours) at a normal rate (0.5 or 1 mL/kg · h). Patients in the treatment group receive a preprocedural loading dose (125/250 mL) of normal saline within 30 minutes and intravenous hydration at a normal rate until LVEDP is available, followed by postprocedural aggressive hydration guided by LVEDP for 4 hours and then continuous intravascular hydration at the normal rate until 24 hours after PCI. The primary end point is CIN, defined as a >25% or 0.5-mg/dL increase in serum creatinine from baseline during the first 48 to 72 hours after procedure. The ATTEMPT study has the potential to identify optimal hydration regimens for STEMI patients undergoing PCI.

Do intravenous N-acetylcysteine and sodium bicarbonate prevent high osmolal contrast-induced acute kidney injury? A randomized controlled trial

BACKGROUND

N-acetylcysteine (NAC) or sodium bicarbonate (NaHCO3), singly or combined, inconsistently prevent patients exposed to radiographic contrast media from developing contrast-induced acute kidney injury (CI-AKI).

OBJECTIVE

We asked whether intravenous isotonic saline and either NaHCO3 in 5% dextrose or else a high dose of NAC in 5% dextrose prevent CI-AKI in outpatients exposed to high-osmolal iodinated contrast medium more than does saline alone.

METHODS

This completed prospective, parallel, superiority, open-label, controlled, computer-randomized, single-center, Brazilian trial (NCT01612013) hydrated 500 adult outpatients (214 at high risk of developing CI-AKI) exposed to ioxitalamate during elective coronary angiography and ventriculography. From 1 hour before through 6 hours after exposure, 126 patients (group 1) received a high dose of NAC and saline, 125 (group 2) received NaHCO3 and saline, 124 (group 3) received both treatments, and 125 (group 4) received only saline.

RESULTS

Groups were similar with respect to age, gender, weight, pre-existing renal dysfunction, hypertension, medication, and baseline serum creatinine and serum cystatin C, but diabetes mellitus was significantly less prevalent in group 1. CI-AKI incidence 72 hours after exposure to contrast medium was 51.4% (257/500), measured as serum creatinine > (baseline+0.3 mg/dL) and/or serum cystatin C > (1.1 · baseline), and 7.6% (38/500), measured as both serum creatinine and serum cystatin C > (baseline+0.3 mg/dL) or > (1.25 · baseline). CI-AKI incidence measured less sensitively was similar among groups. Measured more sensitively, incidence in group 1 was significantly (p<0.05) lower than in groups 2 and 3 but not group 4; adjustment for confounding by infused volume equalized incidence in groups 1 and 3.

CONCLUSION

We found no evidence that intravenous isotonic saline and either NaHCO3 or else a high dose of NAC prevent CI-AKI in outpatients exposed to high osmolal iodinated contrast medium more than does saline alone.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01612013.

Pharmacologic Prophylaxis for Contrast-Induced Acute Kidney Injury

In the effort to prevent contrast-induced acute kidney injury (CI-AKI), several pharmacologic agents have been tested for their single or combined nephroprotective properties. To date, however, no drug has been officially approved for this aim. This article focuses on the three agents that have been most extensively studied: statins, N-acetylcysteine, and ascorbic acid. Particular attention is paid to the impact of these drugs on the CI-AKI prevention and improved prognosis.

Short-term outcome of patients with ST-segment elevation myocardial infarction (STEMI) treated with an everolimus-eluting bioresorbable vascular scaffold

OBJECTIVES

To evaluate safety and efficacy of the everolimus-eluting bioresorbable scaffold (BVS) in patients with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

According to the current guidelines, drug-eluting stents are the treatment of choice in patients with STEMI. BVS represents a new technology capable to restore the native vessel vasomotion and potentially avoiding long-term limitations such as stent thrombosis.

METHODS

From October 2012 to May 2013, patients with evidence of STEMI eligible for BVS implantation were included in this study. Exclusion criteria were not defined.

RESULTS

A total of 25 patients, respectively 31 lesions, were treated. Procedural success was achieved in 97%. Two major adverse cardiac events occurred during hospitalization and follow-up: one patient with cardiogenic shock at the index procedure subsequently died. One patient suffered from instable angina with need for interventional revascularization of a previously untreated vessel. One target vessel failure as a consequence of an intra-procedural dissection was seen. However, no target lesion failure was noted. During 132.7 ± 68.7 days of follow-up none of the patients died.

CONCLUSION

Our findings suggest that implantation of BVS in STEMI patients is feasible in this small cohort of highly selected patients. Further evaluation in randomized-controlled trials is needed.

Alprostadil plays a protective role in contrast-induced nephropathy in the elderly

PURPOSE

To evaluate the protective effects of alprostadil on contrast-induced nephropathy (CIN) in elderly patients.

METHODS

We randomized 370 patients into the control or alprostadil group. The patients in the control group were injected with 100 ml sterile saline and the patients in the alprostadil group with alprostadil (0.4 μg/kg/day) in 100 ml sterile saline before and after iohexol-enhanced (100 ml) computed tomography (CT). Serum creatinine (Scr), blood urea nitrogen (BUN), cystatin C (CysC), and creatinine clearance (Ccr) were analyzed or calculated. ΔScr and ΔCysC were determined by the changes between baseline and highest Scr and CysC levels. The standard for CIN was a postdose Scr increase >44.2 μmol/l or >25 % over baseline.

RESULTS

In the control group, peak Scr (P < 0.05) and ΔScr (P < 0.01) were higher than those in the alprostadil group. The postdose CysC at 24 h (P < 0.05), 48 h (P < 0.05), and 72 h (P < 0.05), peak CysC (P < 0.01), and ΔCysC (P < 0.05) in the control group were higher than those in the alprostadil group. The incidence of CIN in the control group was 22.2 %, which was higher than in the alprostadil group (9.1 %, P < 0.01). Subgroup analyses in patients with advanced age (≥ 80 years), concomitant hypertension or diabetes, and abnormal baseline renal function (Ccr ≤ 60 ml/min) showed that the alprostadil group had lower ΔScr and ΔCysC than the control group after contrast-enhanced CT examination in all four subgroups (P < 0.05 or P < 0.01).

CONCLUSIONS

In this cohort of older patients undergoing contrast CT, the use of alprostadil reduced the incidence of CIN.

N-acetylcysteine plus intravenous fluids versus intravenous fluids alone to prevent contrast-induced nephropathy in emergency computed tomography

STUDY OBJECTIVE

We test the hypothesis that N-acetylcysteine plus normal saline solution is more effective than normal saline solution alone in the prevention of contrast-induced nephropathy.

METHODS

The design was a randomized, double blind, 2-center, placebo-controlled interventional trial. Inclusion criteria were patients undergoing chest, abdominal, or pelvic computed tomography (CT) scan with intravenous contrast, older than 18 years, and at least one contrast-induced nephropathy risk factor. Exclusion criteria were end-stage renal disease, pregnancy, N-acetylcysteine allergy, or clinical instability. Intervention for the treatment group was N-acetylcysteine 3 g in 500 mL normal saline solution as an intravenous bolus and then 200 mg/hour (67 mL/hour) for up to 24 hours; and for the placebo group was 500 mL normal saline solution and then 67 mL/hour for up to 24 hours. The primary outcome was contrast-induced nephropathy, defined as an increase in creatinine level of 25% or 0.5 mg/dL, measured 48 to 72 hours after CT.

RESULTS

The data safety and monitoring board terminated the study early for futility. Of 399 patients enrolled, 357 (89%) completed follow-up and were included. The N-acetylcysteine plus saline solution group contrast-induced nephropathy rate was 14 of 185 (7.6%) versus 12 of 172 (7.0%) in the normal saline solution only group (absolute risk difference 0.6%; 95% confidence interval -4.8% to 6.0%). The contrast-induced nephropathy rate in patients receiving less than 1 L intravenous fluids in the emergency department (ED) was 19 of 147 (12.9%) versus 7 of 210 (3.3%) for greater than 1 L intravenous fluids (difference 9.6%; 95% confidence interval 3.7% to 15.5%), a 69% risk reduction (odds ratio 0.41; 95% confidence interval 0.21 to 0.80) per liter of intravenous fluids.

CONCLUSION

We did not find evidence of a benefit for N-acetylcysteine administration to our ED patients undergoing contrast-enhanced CT. However, we did find a significant association between volume of intravenous fluids administered and reduction in contrast-induced nephropathy.

Prevention of contrast-induced AKI: a review of published trials and the design of the prevention of serious adverse events following angiography (PRESERVE) trial

Contrast-induced AKI (CI-AKI) is a common condition associated with serious, adverse outcomes. CI-AKI may be preventable because its risk factors are well characterized and the timing of renal insult is commonly known in advance. Intravenous (IV) fluids and N-acetylcysteine (NAC) are two of the most widely studied preventive measures for CI-AKI. Despite a multitude of clinical trials and meta-analyses, the most effective type of IV fluid (sodium bicarbonate versus sodium chloride) and the benefit of NAC remain unclear. Careful review of published trials of these interventions reveals design limitations that contributed to their inconclusive findings. Such design limitations include the enrollment of small numbers of patients, increasing the risk for type I and type II statistical errors; the use of surrogate primary endpoints defined by small increments in serum creatinine, which are associated with, but not necessarily causally related to serious, adverse, patient-centered outcomes; and the inclusion of low-risk patients with intact baseline kidney function, yielding low event rates and reduced generalizability to a higher-risk population. The Prevention of Serious Adverse Events following Angiography (PRESERVE) trial is a randomized, double-blind, multicenter trial that will enroll 8680 high-risk patients undergoing coronary or noncoronary angiography to compare the effectiveness of IV isotonic sodium bicarbonate versus IV isotonic sodium chloride and oral NAC versus oral placebo for the prevention of serious, adverse outcomes associated with CI-AKI. This article discusses key methodological issues of past trials investigating IV fluids and NAC and how they informed the design of the PRESERVE trial.