Prevention of radiographic-contrast-agent-induced reductions in renal function by acetylcysteine

N-acetyl-l-cysteine exacerbates kidney dysfunction caused by a chronic high-sodium diet in renal ischemia and reperfusion rats

AIMS

To investigate the effect of long-term N-acetyl-l-cysteine (NAC) treatment in Wistar rats subjected to renal ischemia and reperfusion (IR) and a chronic high‑sodium diet (HSD).

MAIN METHODS

Adult male Wistar rats received an HSD (8.0% NaCl) or a normal‑sodium diet (NSD; 1.3% NaCl) and NAC (600 mg/L) or normal drinking water starting at 8 weeks of age. At 11 weeks of age, the rats from both diet and NAC or water treatment groups underwent renal IR or Sham surgery and were followed for 10 weeks. The study consisted of six animal groups: NSD + Sham + water; NSD + IR + water; NSD + IR + NAC; HSD + Sham + water; HSD + IR + water; and HSD + IR + NAC.

KEY FINDINGS

Tail blood pressure (tBP) increased with IR and NAC treatment in the NSD group but not in the HSD group. The serum creatinine level was higher after NAC treatment in both diet groups, and creatinine clearance was decreased in only the HSD + IR + NAC group. Albuminuria increased in the HSD + IR + water group and decreased in the HSD + IR + NAC group. Kidney mass was increased in the HSD + IR group and decreased with NAC treatment. Renal fibrosis was prevented with NAC treatment and cardiac fibrosis was decreased with NAC treatment in the HSD + IR group.

SIGNIFICANCE

NAC treatment promoted structural improvements, such as decreased albuminuria and fibrosis, in the kidney and heart. However, NAC could not recover kidney function or blood pressure from the effects of IR associated with an HSD. Therefore, in general, long-term NAC treatment is not effective and is deleterious to recovery of function after kidney injury.

[Contrast media - Guidelines for practical use]

Contrast agents have become an indispensable part of everyday life in diagnostic radiology. In multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI), they provide essential diagnostic information, especially for vascular, inflammatory or oncologic diseases, which otherwise could not be answered. The two most important groups are iodine- and gadolinium-containing contrast agents. Rare side effects include PC-AKI (post-contrast acute kidney injury); more common are allergic and chemotoxic reactions. Since the introduction of guidelines, nephrogenic fibrosis has not been reported anymore, whereas gadolinium deposition in the central nervous system (CNS) has become a new topic. Concerning contrast media use in patients with reduced renal function, at a eGFR threshold of <45 ml/min or <30 ml/min, hydration and a review of indication for enhanced MDCT, depending on the application, is recommended. Low kV and DE-scan protocols with MDCT can help to reduce the amount of iodinated contrast agents. In MRI examinations, only macrocyclic contrast agents should be used for enhanced MRI exams. There has to be a careful risk-benefit analysis with enhanced studies in pregnancy, during lactation and in the pediatric population. Patient information and legal aspects with nonapproved indications are indispensable parts of daily clinical routine. The continuous updating and broadening of knowledge regarding the appropriate use of the various contrast agents has to be an integral part of clinical diagnostic radiology.

Contrast Nephropathy Associated with Percutaneous Coronary Angiography and Intervention

Contrast nephropathy (CN) is acute kidney injury (AKI) that occurs within 24 to 72 hours of iodinated contrast medium (ICM) administration. Mechanisms of CN include hyperviscosity, free radical formation, and renal medullary oxygen supply/demand mismatch. Although risk factors for CN have been identified, it remains uncertain whether ICM causes or is simply associated with AKI. The cornerstones of CN prevention are using low-osmolal ICM, intravenous hydration, and statins, especially in patients with chronic kidney disease. With appropriate CN risk mitigation, coronary angiography and intervention should not be routinely withheld from patients with acute coronary syndromes.

Contrast-associated acute kidney injury: does it really exist, and if so, what to do about it?

For decades, when contrast agents are administrated, physicians have been concerned because of the risk of inducing acute kidney injury (AKI). Recent literature questions the existence of AKI induced by contrast, but animal studies clearly showed harmful effects. The occurrence of contrast-associated AKI was likely overestimated in the past because of confounders for AKI. Several strategies have been investigated to reduce contrast-associated AKI but even for the most important one, hydration, there are conflicting data. Even if the occurrence rate of contrast-associated AKI is low, AKI is related to worse outcomes. Therefore, besides limiting contrast agent usage, general AKI preventive measurements should be applied in at-risk patients.

Contrast Induced Acute Kidney Injury and Direct Cytotoxicity of Iodinated Radiocontrast Media on Renal Proximal Tubule Cells

The administration of intravenous iodinated radiocontrast media (RCM) to visualize internal structures during diagnostic procedures has increased exponentially since their first use in 1928. A serious side effect of RCM exposure is contrast-induced acute kidney injury (CI-AKI), which is defined as an abrupt and prolonged decline in renal function occurring 48-72 hours after injection. Multiple attempts have been made to decrease the toxicity of RCM by altering ionic strength and osmolarity, yet there is little evidence to substantiate that a specific RCM is superior in avoiding CI-AKI. RCM-associated kidney dysfunction is largely attributed to alterations in renal hemodynamics, specifically renal vasoconstriction; however, numerous studies indicate direct cytotoxicity as a source of epithelial damage. Exposure of in vitro renal proximal tubule cells to RCM has been shown to affect proximal tubule epithelium in the following manner: 1) changes to cellular morphology in the form of vacuolization; 2) increased production of reactive oxygen species, resulting in oxidative stress; 3) mitochondrial dysfunction, resulting in decreased efficiency of the electron transport chain and ATP production; 4) perturbation of the protein folding capacity of the endoplasmic reticulum (ER) (activating the unfolded protein response and inducing ER stress); and 5) decreased activity of cell survival kinases. The present review focuses on the direct cytotoxicity of RCM on proximal tubule cells in the absence of in vivo complications, such as alterations in renal hemodynamics or cytokine influence.

Anaesthetic Management of Planned or Emergency Endovascular Stent Graft Surgery for Thoracic Aneurysms and Dissections

We reviewed the intraoperative anaesthetic management and outcome of seven consecutive cases of endovascular stent graft surgery for thoracic aortic aneurysms or dissections over a period of 20 months in our institution. Seven males (median age 63) underwent endovascular stent graft surgery of the thoracic aorta under general anaesthesia. Four were emergency procedures for acute dissection or leaks of thoracic aneurysms. The duration of the procedures ranged from 120 to 300 minutes. Intraoperative stent migration occurred in one patient. Induced hypotension and immobilization were critical during stent deployment. Six out of the seven patients were discharged home between three to 20 days postoperatively. There was no 30-day mortality. One patient died sixty days postoperatively. Anaemia and respiratory complications were the most common postoperative problems encountered. None of the patients sustained spinal cord ischaemia, acute myocardial infarction or renal impairment. Endovascular stent graft surgery of the thoracic aorta is a relatively new alternative to conventional open surgery. Our experience suggests satisfactory short-term outcome even for patients with acute dissection. However, long-term survival and results require further evaluation.

Cysteine/Glutathione Deficiency: A Significant and Treatable Corollary of Disease

Glutathione (GSH) deficiency may play a pivotal role in a variety of apparently unrelated clinical conditions and diseases. Orally administered N-acetylcysteine (NAC), which replenishes the cysteine required for GSH synthesis, has been tested in a large number of randomized placebo-controlled trials involving these diseases and conditions. This chapter focused on developing a base of evidence suggesting that NAC administration improves disease by increasing cysteine and/or GSH in a variety of diseases, thereby implying a significant role for GSH deficiency in the clinical basis of many diseases. To develop this base of evidence, we systematically selected studies which considered the hypothesis that the therapeutic efficacy for NAC is an indication that cysteine and/or GSH deficiency is a pathophysiological part of the diseases studied. In this manner we focus this chapter on explaining the biological mechanisms of NAC therapy in a wide variety of disorders and demonstrate its ubiquitous role in improving disease that involves disrupted GSH and/or cysteine metabolism.

Molybdenum-based nanoclusters act as antioxidants and ameliorate acute kidney injury in mice

Acute kidney injury (AKI) is a common reactive oxygen species (ROS)-related renal disease that causes numerous deaths annually, yet only supportive treatment is currently available in the clinics. Development of antioxidants with high accumulation rates in kidneys is highly desired to help prevent AKI. Here we report molybdenum-based polyoxometalate (POM) nanoclusters with preferential renal uptake as novel nano-antioxidants for kidney protection. These POM nanoclusters, with a readily variable valence state of molybdenum ions, possess the capability to scavenge detrimental ROS. Our results demonstrate that POM nanoclusters can efficiently alleviate clinical symptoms in mice subjected to AKI, as verified by dynamic PET imaging with ⁶⁸Ga-EDTA, serum tests, kidney tissue staining, and biomarkers detection in the kidneys. The protective effect of POM nanoclusters against AKI in living animals suggests exploring their use for the treatment of AKI patients, as well as patients with other ROS-related diseases.

There are currently no effective therapies available for acute kidney injury (AKI). Here the authors generate molybdenum-based polyoxometalate nanoclusters and show that these have preferential renal uptake and can ameliorate AKI pathology in mice by scavenging reactive oxygen species.

Predicting acute kidney injury at hospital re-entry using high-dimensional electronic health record data

Acute Kidney Injury (AKI), a sudden decline in kidney function, is associated with increased mortality, morbidity, length of stay, and hospital cost. Since AKI is sometimes preventable, there is great interest in prediction. Most existing studies consider all patients and therefore restrict to features available in the first hours of hospitalization. Here, the focus is instead on rehospitalized patients, a cohort in which rich longitudinal features from prior hospitalizations can be analyzed. Our objective is to provide a risk score directly at hospital re-entry. Gradient boosting, penalized logistic regression (with and without stability selection), and a recurrent neural network are trained on two years of adult inpatient EHR data (3,387 attributes for 34,505 patients who generated 90,013 training samples with 5,618 cases and 84,395 controls). Predictions are internally evaluated with 50 iterations of 5-fold grouped cross-validation with special emphasis on calibration, an analysis of which is performed at the patient as well as hospitalization level. Error is assessed with respect to diagnosis, race, age, gender, AKI identification method, and hospital utilization. In an additional experiment, the regularization penalty is severely increased to induce parsimony and interpretability. Predictors identified for rehospitalized patients are also reported with a special analysis of medications that might be modifiable risk factors. Insights from this study might be used to construct a predictive tool for AKI in rehospitalized patients. An accurate estimate of AKI risk at hospital entry might serve as a prior for an admitting provider or another predictive algorithm.

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.

DNA origami nanostructures can exhibit preferential renal uptake and alleviate acute kidney injury

Patients with acute kidney injury (AKI) frequently require kidney transplantation and supportive therapies, such as rehydration and dialysis. Here, we show that radiolabelled DNA origami nanostructures (DONs) with rectangular, triangular and tubular shapes accumulate preferentially in the kidneys of healthy mice and mice with rhabdomyolysis-induced AKI, and that rectangular DONs have renal-protective properties, with efficacy similar to the antioxidant N-acetylcysteine-a clinically used drug that ameliorates contrast-induced AKI and protects kidney function from nephrotoxic agents. We evaluated the biodistribution of DONs non-invasively via positron emission tomography, and the efficacy of rectangular DONs in the treatment of AKI via dynamic positron emission tomography imaging with 68Ga-EDTA, blood tests and kidney tissue staining. DNA-based nanostructures could become a source of therapeutic agents for the treatment of AKI and other renal diseases.

N-acetylcysteine ethyl ester as GSH enhancer in human primary endothelial cells: A comparative study with other drugs

Several drugs are currently in use as glutathione (GSH) enhancers in clinical, pre-clinical and experimental research. Here we compare the ability of N-acetylcysteine (NAC), 2-oxothiazolidine-4-carboxylic acid (OTC), glutathione ethyl ester (GSH-EE) and N-acetylcysteine ethyl ester (NACET) to increase the intracellular concentration of GSH using primary human umbilical vein endothelial cells (HUVEC) as in vitro model. Our experiments highlighted that NACET is largely the most efficient molecule in increasing the intracellular levels of GSH, cysteine, and γ-glutamylcysteine. This is because NACET is lipophilic and can freely cross plasma membrane but, inside the cell, it is de-esterified to the more hydrophilic NAC, which, in turn, is trapped into the cell and slowly transformed into cysteine. The higher availability of cysteine is matched by an increase in GSH synthesis, cysteine availability being the rate limiting step for this reaction. Surprisingly, the increase in GSH concentration was not linear but peaked at 0.5 mM NACET and gradually decreased when cells were treated with higher concentrations of NACET. We demonstrated that this puzzling ceiling effect was due to the fact that NAC released from NACET turned out to be a competitive inhibitor of the enzyme glutamate-cysteine ligase, with a Ki value of 3.2 mM. By using a cell culture medium lacking of cysteine and methionine, we could demonstrate that the slight increase in intracellular levels of cysteine and GSH induced by NAC in HUVEC grown in standard medium was due to the reduction of the cystine present in the medium itself there rather than to the action of NAC as Cys pro-drug. This fact may explain why NAC works well as GSH enhancer at very high concentrations in pre-clinical and in vitro studies, whereas it failed in most clinical trials.

Contrast Media-Induced Nephropathy in Patients with Unruptured Cerebral Aneurysm After Coiling Endovascular Treatment

BACKGROUND

The endovascular coiling procedure to treat cerebral aneurysms using contrast media has become more popular. However, studies of the incidence of, and risk factors for, contrast media-induced nephropathy (CIN) after coiling procedures have been limited. Thus, we evaluated the incidence and risk factors for CIN in patients who had undergone cerebral aneurysmal coiling procedures.

METHODS

We retrospectively reviewed the electric medical records of 380 patients who had undergone cerebral aneurysmal coiling treatment under general anesthesia. CIN was defined as an absolute increase in serum creatinine (≥0.5 mg/dL) or a relative increase (≥25%) in the baseline serum creatinine value at 48-72 hours after exposure to a contrast agent.

RESULTS

Elective cerebral aneurysmal coiling procedures were performed in 230 patients. Of the 230 patients, CIN developed in 13 (5.6%). The presence of diabetes mellitus (30.8% vs. 9.7%; P = 0.040) and patient age >75 years (30.8% vs. 6.5%; P = 0.012) were risk factors for CIN.

CONCLUSIONS

Our study has demonstrated that the incidence of CIN in patients undergoing elective cerebral aneurysmal coiling procedures is ∼6.0%. We also identified underlying diabetes mellitus and advanced age (≥75 years) as potential risk factors.

Lessons learned from the PRESERVE trial

The recently published Prevention of Serious Adverse Events Following Angiography (PRESERVE) trial is presently the largest and most comprehensive clinical trial comparing commonly applied strategies for prevention of iodinated contrast-induced acute kidney injury in high-risk patients. The fundamental conclusion of the PRESERVE trial is that oral acetylcysteine and i.v. sodium bicarbonate are not superior to simple i.v. hydration with isotonic saline for the prevention of contrast-induced renal sequelae. In this commentary, we discuss the results in the context of selected past major trials, and provide insights into the strengths and potential weaknesses of the PRESERVE trial. In the future, developing individualized preventive approaches to avoid contrast-induced acute kidney injury for different patient populations is recommended.

Clinical Implications of Contrast-Induced Nephropathy in Patients Without Baseline Renal Dysfunction Undergoing Coronary Angiography

BACKGROUND

The clinical implications of different definitions of contrast-induced nephropathy (CIN) in patients without baseline renal dysfunction are not well defined.

METHODS

Consecutive patients at a single centre without baseline renal dysfunction (estimated glomerular filtration rate, eGFR≥60ml/min/1.73m²) undergoing coronary angiography or percutaneous coronary intervention (PCI), were systematically evaluated for long-term risk of mortality following CIN using two broad definitions: an absolute increase from baseline in serum creatinine (SCr) ≥0.3mg/dl (mild to severe absolute CIN) and a relative increase from baseline of 25% (mild to severe relative CIN) within 72hours.

RESULT

Of 2,823 subjects alive before discharge following coronary angiography there were 320 episodes of mild to severe relative CIN (11.3%) and 125 of mild to severe absolute CIN (4.4%). During a median follow-up of 2.3years, 73 patients (3.2%) died. After adjustment for confounders, mild to severe absolute CIN was associated with an adjusted hazard ratio (HR) (95% confidence interval) for all-cause mortality of 3.31 (1.74-6.30) (p<0.0001) and relative CIN with an adjusted HR of 1.92 (1.09, 3.38) (p=0.024). The risk of mortality rose with severity of CIN. Two commonly used definitions of CIN combining absolute and relative terms (increase ≥ 0.3mg/dl or 50%, and ≥ 0.5mg/dl or 25% from the baseline) confirmed these results.

CONCLUSION

Among patients without baseline renal dysfunction undergoing coronary angiography, the incidence of CIN can range widely depending on definition. Absolute CIN is less common than relative CIN. Regardless of definition, CIN is associated with a markedly increased risk of long-term mortality. This finding requires confirmation in multicentre studies.

Contrast-Induced Nephropathy: Update on the Use of Crystalloids and Pharmacological Measures

Contrast-induced nephropathy (CIN) is a frequent and severe complication in subjects receiving iodinated contrast media for diagnostic or therapeutic purposes. Several preventive strategies were evaluated in the past. Recent clinical studies and meta-analyses delivered some new aspects on preventive measures used in the past and present. We will discuss all pharmacological and nonpharmacological procedures. Finally, we will suggest individualized recommendations for CIN prevention.

Acute Kidney Injury and Progression of Diabetic Kidney Disease

Diabetic kidney disease, commonly termed diabetic nephropathy (DN), is the most common cause of end-stage kidney disease (ESKD) worldwide. The characteristic histopathology of DN includes glomerular basement membrane thickening, mesangial expansion, nodular glomerular sclerosis, and tubulointerstitial fibrosis. Diabetes is associated with a number of metabolic derangements, such as reactive oxygen species overproduction, hypoxic state, mitochondrial dysfunction, and inflammation. In the past few decades, our knowledge of DN has advanced considerably although much needs to be learned. The traditional paradigm of glomerulus-centered pathophysiology has expanded to the tubule-interstitium, the immune response and inflammation. Biomarkers of proximal tubule injury have been shown to correlate with DN progression, independent of traditional glomerular injury biomarkers such as albuminuria. In this review, we summarize mechanisms of increased susceptibility to acute kidney injury in diabetes mellitus and the roles played by many kidney cell types to facilitate maladaptive responses leading to chronic and end-stage kidney disease.

Outcomes after Angiography with Sodium Bicarbonate and Acetylcysteine

BACKGROUND

Intravenous sodium bicarbonate and oral acetylcysteine are widely used to prevent acute kidney injury and associated adverse outcomes after angiography without definitive evidence of their efficacy.

METHODS

Using a 2-by-2 factorial design, we randomly assigned 5177 patients at high risk for renal complications who were scheduled for angiography to receive intravenous 1.26% sodium bicarbonate or intravenous 0.9% sodium chloride and 5 days of oral acetylcysteine or oral placebo; of these patients, 4993 were included in the modified intention-to-treat analysis. The primary end point was a composite of death, the need for dialysis, or a persistent increase of at least 50% from baseline in the serum creatinine level at 90 days. Contrast-associated acute kidney injury was a secondary end point.

RESULTS

The sponsor stopped the trial after a prespecified interim analysis. There was no interaction between sodium bicarbonate and acetylcysteine with respect to the primary end point (P=0.33). The primary end point occurred in 110 of 2511 patients (4.4%) in the sodium bicarbonate group as compared with 116 of 2482 (4.7%) in the sodium chloride group (odds ratio, 0.93; 95% confidence interval [CI], 0.72 to 1.22; P=0.62) and in 114 of 2495 patients (4.6%) in the acetylcysteine group as compared with 112 of 2498 (4.5%) in the placebo group (odds ratio, 1.02; 95% CI, 0.78 to 1.33; P=0.88). There were no significant between-group differences in the rates of contrast-associated acute kidney injury.

CONCLUSIONS

Among patients at high risk for renal complications who were undergoing angiography, there was no benefit of intravenous sodium bicarbonate over intravenous sodium chloride or of oral acetylcysteine over placebo for the prevention of death, need for dialysis, or persistent decline in kidney function at 90 days or for the prevention of contrast-associated acute kidney injury. (Funded by the U.S. Department of Veterans Affairs Office of Research and Development and the National Health and Medical Research Council of Australia; PRESERVE ClinicalTrials.gov number, NCT01467466 .).

Prevention of Contrast Nephropathy in Critically Ill Patients Using Acetylcysteine and Theophylline

Compared with periprocedural hydration alone, acetylcysteine with hydration significantly reduces the risk of contrast nephropathy in patients with chronic renal insufficiency by 50%. For elective contrast procedures, acetylcysteine should be given in a dose of 600 mg twice daily the day before and on the procedure day. For emergency procedures, a high dose intravenous regimen (150 mg/kg in 500 mL normal saline over 30 minutes immediately before contrast followed by 50 mg/kg in 500 mL normal saline over 4h) is effective. Given the low cost and good side-effect profile of acetylcysteine, it would seem prudent to give this drug with intravenous fluids to all critically ill patients scheduled for intravenous or intraarterial contrast procedures. Theophylline in a dose of 200 mg or 2.5 mg/kg IV 30 minutes before contrast may be an effective alternative for emergency procedures. Although its benefit compared with periprocedural hydration alone seems less well established, theophylline is a particularly attractive option for emergency procedures.

Oxidative stress caused by activation of NADPH oxidase 4 promotes contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CIAKI) is a leading cause of acute kidney injury following radiographic procedures. Intrarenal oxidative stress plays a critical role in CIAKI. Nicotinamide adenine dinucleotide 3-phosphate (NADPH) oxidases (Noxs) are important sources of reactive oxygen species (ROS). Among the various types of Noxs, Nox4 is expressed predominantly in the kidney in rodents. Here, we evaluated the role of Nox4 and benefit of Nox4 inhibition on CIAKI using in vivo and in vitro models. HK-2 cells were treated with iohexol, with or without Nox4 knockdown, or the most specific Nox1/4 inhibitor (GKT137831). Effects of Nox4 inhibition on CIAKI mice were examined. Expression of Nox4 in HK-2 cells was significantly increased following iohexol exposure. Silencing of Nox4 rescued the production of ROS, downregulated pro-inflammatory markers (particularly phospho-p38) implicated in CIAKI, and reduced Bax and caspase 3/7 activity, which resulted in increased cellular survival in iohexol-treated HK-2 cells. Pretreatment with GKT137831 replicated these effects by decreasing levels of phospho-p38. In a CIAKI mouse model, even though the improvement of plasma blood urea nitrogen was unclear, pretreatment with GKT137831 resulted in preserved structure, reduced expression of 8-hydroxy-2'-deoxyguanosine (8OHdG) and kidney injury molecule-1 (KIM-1), and reduced number of TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling)-positive cells. These results suggest Nox4 as a key source of reactive oxygen species responsible for CIAKI and provide a novel potential option for prevention of CIAKI.

Acute Kidney Injury (AKI)

Kidneys perform a multitude of essential functions within the human body. Of these the most important are (1) maintaining pH through regulation of acid/base levels and (2) excreting end products of metabolism. As for most organ-systems, these functions are especially important for healing following trauma and/or surgery and decline with age. Acute Kidney Injury (AKI) is one of the common forms of organ failures seen in the ICU and elderly patients are more prone to it. The causes maybe classified as Prerenal (inadequate perfusion), renal (inherent kidney disease) and post-renal (urinary obstruction). Preventing AKI should be an important concern in all critically ill patients but especially important in the elderly patients since the development of AKI can significantly increase in-hospital mortality. Once AKI has set in a systematic and step-wise approach of diagnosis and management is key to avoiding adverse outcomes.

Oxidative Stress in Patients Undergoing Peritoneal Dialysis: A Current Review of the Literature

Peritoneal dialysis (PD) patients manifest excessive oxidative stress (OS) compared to the general population and predialysis chronic kidney disease patients, mainly due to the composition of the PD solution (high-glucose content, low pH, elevated osmolality, increased lactate concentration and glucose degradation products). However, PD could be considered a more biocompatible form of dialysis compared to hemodialysis (HD), since several studies showed that the latter results in an excess accumulation of oxidative products and loss of antioxidants. OS in PD is tightly linked with chronic inflammation, atherogenesis, peritoneal fibrosis, and loss of residual renal function. Although exogenous supplementation of antioxidants, such as vitamins E and C, N-acetylcysteine, and carotenoids, in some cases showed potential beneficial effects in PD patients, relevant recommendations have not been yet adopted in everyday clinical practice.

Impact of Transient or Persistent Contrast-induced Nephropathy on Long-term Mortality After Elective Percutaneous Coronary Intervention

Contrast-induced nephropathy (CIN) is associated with increased long-term mortality. However, it is still controversial whether CIN is the cause of increased mortality or merely a marker of high-risk patients. The current study population included 5,516 patients who underwent their first elective percutaneous coronary intervention (PCI) in the Coronary REvascularization Demonstrating Outcome Study in Kyoto registry cohort-2. CIN was defined as an elevation in the peak serum creatinine (SCr) of ≥0.5 mg/dl from the baseline within 5 days after PCI. CIN, seen in 218 patients (4.0%), was independently associated with an increased long-term mortality risk (hazard ratio [HR] 1.43, 95% confidence interval [CI],1.11 to 1.83; p = 0.005). SCr data at 1 year (180 to 550 days) after PCI were available in 3,986 patients, who were subdivided into persistent CIN (follow-up SCr elevation ≥0.5 mg/dl: n = 50 [1.3%]), transient CIN (follow-up SCr elevation <0.5 mg/dl: n = 90 [2.3%]), and non-CIN (n = 3,846 [96.5%]). In the landmark analysis at 1 year after PCI, 524 patients (13.1%) died during a median follow-up of 1,521 days. After adjustment for the 37 confounders, persistent CIN, but not transient CIN, was significantly correlated with a higher long-term mortality risk compared with non-CIN (HR 1.84, 95% CI 1.12 to 3.03; p = 0.02, and HR 1.11, 95% CI 0.71 to 1.76; p = 0.6, respectively). In conclusion, only persistent CIN was independently associated with increased long-term mortality.

N-acetylcysteine ameliorates contrast‑induced kidney injury in rats with unilateral hydronephrosis

The aim of the present study was to investigate the protective effects of N-acetylcysteine (NAC) on contrast-induced acute kidney injury in rats with unilateral hyronephrosis. Eighty-two male Sprague Dawley rats were randomized to undergo sham operation (n=14) or unilateral ureteral obstruction (UUO) (n=68). After 3 weeks, the UUO animals were randomized to three groups: NAC gastric perfusion, UUO+iohexol+NAC (n=24); normal saline perfusion, UUO+iohexol (n=24); and controls, UUO (n=20). After 3 days, UUO+iohexol+NAC and UUO+iohexol rats were injected with iohexol. One day after contrast, half of the rats were sacrificed to assess the pathological changes to the kidneys, serum creatinine, serum neutrophil gelatinase-associated lipocalin (NGAL), renal cell apoptosis rate and expression of apoptosis regulators Bcl-2/Bax. The remaining rats underwent obstruction relief and were analyzed 3 weeks later. Compared with the controls, serum NGAL levels were high in UUO+iohexol rats 1 day following injection and 3 weeks after obstruction relief, but UUO+iohexol+NAC rats exhibited lower serum NGAL levels compared with UUO+iohexol rats (all P<0.05). Following modeling, UUO+iohexol rats exhibited a significantly higher apoptosis rate of renal tubular cells, higher expression of Bax mRNA, and lower ratio of Bcl-2/Bax (all P<0.05). Three weeks after obstruction relief, UUO+iohexol+NAC rats exhibited a lower apoptosis rate, lower Bax mRNA expression, higher expression of Bcl-2 mRNA and higher ratio of Bcl-2/Bax (all P<0.05) compared with day 1 following drug administration. The prophylactic use of NAC reduced the apoptotic rate of renal tubular cells following contrast exposition, which was accompanied by changes in the expression of Bcl-2/Bax mRNA.

Dose escalation study of intravenous and intra-arterial N-acetylcysteine for the prevention of oto- and nephrotoxicity of cisplatin with a contrast-induced nephropathy model in patients with renal insufficiency

Background

Cisplatin neuro-, oto-, and nephrotoxicity are major problems in children with malignant tumors, including medulloblastoma, negatively impacting educational achievement, socioemotional development, and overall quality of life. The blood-labyrinth barrier is somewhat permeable to cisplatin, and sensory hair cells and cochlear supporting cells are highly sensitive to this toxic drug. Several chemoprotective agents such as N-acetylcysteine (NAC) were utilized experimentally to avoid these potentially serious and life-long side effects, although no clinical phase I trial was performed before. The purpose of this study was to establish the maximum tolerated dose (MTD) and pharmacokinetics of both intravenous (IV) and intra-arterial (IA) NAC in adults with chronic kidney disease to be used in further trials on oto- and nephroprotection in pediatric patients receiving platinum therapy.

Methods

Due to ethical considerations in pediatric tumor patients, we used a clinical population of adults with non-neoplastic disease. Subjects with stage three or worse renal failure who had any endovascular procedure were enrolled in a prospective, non-randomized, single center trial to determine the MTD for NAC. We initially aimed to evaluate three patients each at 150, 300, 600, 900, and 1200 mg/kg NAC. The MTD was defined as one dose level below the dose producing grade 3 or 4 toxicity. Serum NAC levels were assessed before, 5 and 15 min post NAC. Twenty-eight subjects (15 men; mean age 72.2 ± 6.8 years) received NAC IV (N = 13) or IA (N = 15).

Results

The first participant to experience grade 4 toxicity was at the 600 mg/kg IV dose, at which time the protocol was modified to add an additional dose level of 450 mg/kg NAC. Subsequently, no severe NAC-related toxicity arose and 450 mg/kg NAC was found to be the MTD in both IV and IA groups. Blood levels of NAC showed a linear dose response (p < 0.01). Five min after either IV or IA NAC MTD dose administration, serum NAC levels reached the 2–3 mM concentration which seemed to be nephroprotective in previous preclinical studies.

Conclusions

In adults with kidney impairment, NAC can be safely given both IV and IA at a dose of 450 mg/kg. Additional studies are needed to confirm oto- and nephroprotective properties in the setting of cisplatin treatment.

Clinical Trial Registration URL: https://eudract.ema.europa.eu. Unique identifier: 2011-000887-92

Oxidative Stress in Hemodialysis Patients: A Review of the Literature

Hemodialysis (HD) patients are at high risk for all-cause mortality and cardiovascular events. In addition to traditional risk factors, excessive oxidative stress (OS) and chronic inflammation emerge as novel and major contributors to accelerated atherosclerosis and elevated mortality. OS is defined as the imbalance between antioxidant defense mechanisms and oxidant products, the latter overwhelming the former. OS appears in early stages of chronic kidney disease (CKD), advances along with worsening of renal failure, and is further exacerbated by the HD process per se. HD patients manifest excessive OS status due to retention of a plethora of toxins, subsidized under uremia, nutrition lacking antioxidants and turn-over of antioxidants, loss of antioxidants during renal replacement therapy, and leukocyte activation that leads to accumulation of oxidative products. Duration of dialysis therapy, iron infusion, anemia, presence of central venous catheter, and bioincompatible dialyzers are several factors triggering the development of OS. Antioxidant supplementation may take an overall protective role, even at early stages of CKD, to halt the deterioration of kidney function and antagonize systemic inflammation. Unfortunately, clinical studies have not yielded unequivocal positive outcomes when antioxidants have been administered to hemodialysis patients, likely due to their heterogeneous clinical conditions and underlying risk profile.

Could Vitamin E Prevent Contrast-Induced Acute Kidney Injury? A Systematic Review and Meta-Analysis

Several clinical studies have proposed a protective role for vitamin E (α-tocopherol) against contrast-induced acute kidney injury (CIAKI). The aim of study was to assess the effects of vitamin E for the prevention of CIAKI. A systematic review and meta-analysis was conducted using MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials. Randomized controlled trials (RCTs) reporting the effects of vitamin E on CIAKI development and measurements of renal function were included. Four trials including 623 participants were analyzed in the meta-analysis. All participants received intravenous hydration in addition to vitamin E or placebo. The incidence of the vitamin E group (5.8%) was lower than that of the control group (15.4%). Compared with the control, vitamin E significantly reduced the risk ratio (RR) of CIAKI by 62% (0.38; 95% confidence interval [CI], 0.22, 0.63; P < 0.010). In addition, vitamin E reduced serum creatinine (SCr) increase after contrast administration (standardized mean difference [SMD], -0.27; 95% CI, -0.49, -0.06; P = 0.010). However, changes in glomerular filtration rate (GFR) after contrast administration were not significantly different between vitamin E and the control group (SMD, 0.21; 95% CI, -0.01, 0.43; P = 0.060). Heterogeneity within the available trials was not observed. Our meta-analysis provides evidence that vitamin E plus hydration significantly reduced the risk of CIAKI in patients with renal impairment compared with hydration alone.

Oral N-acetylcysteine for prophylaxis of contrast-induced nephropathy in patients following coronary angioplasty: A meta-analysis

It is acknowledged that contrast-induced nephropathy (CIN) is a common cause of acute renal insufficiency after cardiac catheterization and affects mortality and morbidity. To date, it is unknown whether oral N-acetylcysteine (NAC) is able to prevent contrast-induced nephropathy (CIN) in patients undergoing coronary angioplasty. A meta-analysis of randomized controlled trials was performed to assess the effects of NAC in the prevention of CIN in patients following coronary angioplasty. A total of 19 studies published prior to January 2015 that investigated the efficacy of oral NAC for the prevention of CIN were collected from Medline, Cochrane and Embase databases and conference proceedings from cardiology and nephrology meetings. The primary point of investigation was CIN, and the secondary points were renal failure requiring dialysis, mortality and length of hospitalization. The meta-analysis was performed using fixed- or random-effect models according to heterogeneity. Up to January 2015, 19 randomized placebo-controlled clinical trials met the inclusion criteria for the meta-analysis, including 4,514 patients. The pooled data showed that oral NAC did not reduce the CIN incidence [relative risk 0.84, 95% confidence interval (CI) 0.65-1.10; P=0.20], without heterogeneity among trials (I2=29%). Thus, the present meta-analysis suggests that oral NAC therapy is not effective as an alternative treatment to prevent CIN in patients following angioplasty. Further high quality randomized clinical controlled trials are required to confirm the usage and availability of this treatment.

Incidence, Risk Factors, and Mortality of Reintubation in Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective study of an administrative database.

OBJECTIVE

The objective was to investigate the incidence, risk factors, and mortality rate of reintubation after adult spinal deformity (ASD) surgery.

BACKGROUND DATA

There are limited data regarding the occurrence of reintubation after ASD surgery.

MATERIALS AND METHODS

The Nationwide Inpatient Sample database from 2002 to 2011 was used to identify adult patients who underwent elective surgery for scoliosis. Patients who required reintubation were identified and compared with controls (no reintubation). A multivariable logistic regression analysis was performed to identify independent factors associated with reintubation.

RESULTS

A total of 9734 patients who underwent surgery for ASD were identified, and 182 required reintubation [1.8%; 95% confidence interval (CI), 1.6%-2.1%] on average 2 days after surgery (range, 0-28 d). After multivariable analysis, the strongest independent risk factors associated with reintubation included postoperative acute respiratory failure [odds ratio (OR), 12.0; 95% CI, 8.6-16.6], sepsis (OR, 6.9; 95% CI, 3.5-13.6), and deep vein thrombosis (OR, 5.7; 95% CI, 3.0-10.9); history of chronic lung disease (OR, 1.6; 95% CI, 1.1-2.3) and fusion of 8 or more segments (OR, 1.5; 95% CI, 1.1-2.2) were also independent risk factors. Mortality rates were significantly higher in reintubated patients (7.3%) compared with that in nonreintubated patients (0.2%, P<0.001). More importantly, reintubation was an independent risk factor for inpatient mortality (OR, 9.8; 95% CI, 4.1-23.5; P<0.001).

CONCLUSIONS

The reintubation rate after ASD surgery is approximately 1.8%. Patients with a history of chronic lung disease and patients undergoing fusion of 8 or more segments may be at an increased risk for reintubation; other associated factors included acute respiratory failure, sepsis, and deep vein thrombosis. Patients who required postoperative airway management after ASD surgery were 9.8 times more likely to die during their hospital stay compared with controls.

Safe and Appropriate Use of lodinated Radiographic Contrast Agents: Is There a Reason to Use High-Osmolality lodinated Contrast Agents?

The improved safety profile of low-osmolality compared with high-osmolality iodinated radiographic contrast agents supports the use of low-osmolality iodinated contrast agents in patients with a high risk for adverse reactions to contrast agents. Current pressures in the health care industry to minimize costs may warrant the continued use of high-osmolality agents in patients with relatively low risk for contrast reactions. Health-system management and pharmacists should continue to review the clinical and pharmacoeconomic issues surrounding the use of high-osmolality agents, because market factors have caused the prices of high-osmolality agents and second-generation low-osmolality agents to fluctuate. Moreover, the introduction of new agents will continue to change the risk—benefit–cost relationship.

Administration guidelines and appropriate patient monitoring are important, because both low-osmolality and high-osmolality agents carry the risk of adverse reactions. Pharmacologic pretreatment to alleviate adverse reactions to contrast agents when high-osmolality agents are used should be encouraged. Pharmacists—in cooperation with diagnostic imaging departments—should ensure that the use of iodinated radiographic contrast agents conforms to accepted guidelines.

Prospective evaluation of the development of contrast-induced nephropathy in patients with acute coronary syndrome undergoing rotational coronary angiography vs. conventional coronary angiography: CINERAMA study

INTRODUCTION AND OBJECTIVES

Rotational coronary angiography (RCA) requires less contrast to be administered and can prevent the onset of contrast-induced nephropathy (CIN) during invasive coronary procedures. The aim of the study is to evaluate the impact of RCA on CIN (increase in serum creatinine ≥0.5mg/dl or ≥25%) after an acute coronary syndrome.

METHODS

From April to September 2016, patients suffering acute coronary syndromes who underwent diagnostic coronary angiography, with the possibility of ad hoc coronary angioplasty, were prospectively enrolled. At the operator's discretion, patients underwent RCA or conventional coronary angiography (CCA). CIN (primary endpoint), as well as analytical, angiographic and clinical endpoints, were compared between groups.

RESULTS

Of the 235 patients enrolled, 116 patients received RCA and 119 patients received CCA. The RCA group was composed of older patients (64.0±11.8 years vs. 59.7±12.1 years; p=0.006), a higher proportion of women (44.8 vs. 17.6%; p<0.001), patients with a lower estimated glomerular filtration rate (76±25 vs. 86±27ml/min/1.73 m²; p=0.001), and patients who underwent fewer coronary angioplasties (p<0.001) compared with the CCA group. Furthermore, the RCA group, received less contrast (113±92 vs. 169±103ml; p<0.001), including in diagnostic procedures (54±24 vs. 85±56ml; p<0.001) and diagnostic-therapeutic procedures (174±64 vs. 205±98ml; p=0.049) compared with the CCA group. The RCA group presented less CIN (4.3 vs. 22.7%; p<0.001) compared to the CCA group, and this finding was maintained in the regression analysis (Adjusted relative risk: 0.868; 95% CI: 0.794-0.949; p=0.002). There were no differences in clinical endpoints between the groups.

CONCLUSIONS

RCA was associated with lower administration of contrast during invasive coronary procedures in acute coronary syndrome patients, resulting in lower incidence of CIN, in comparison with CCA.

Evaluation of the inhibitory effect of N-acetyl-L-cysteine on Babesia and Theileria parasites

N-acetyl-L-cysteine is known to have antibacterial, antiviral, antimalarial, and antioxidant activities. Therefore, the in vitro inhibitory effect of this hit was evaluated in the present study on the growth of Babesia and Theileria parasites. The in vitro growth of Babesia bovis, Babesia bigemina, Babesia divergens, Theileria equi, and Babesia caballi that were tested was significantly inhibited (P < 0.05) by micromolar concentrations of N-acetyl-L-cysteine. The inhibitory effect of N-acetyl-L-cysteine was synergistically potentiated when used in combination with diminazene aceturate on B. bovis and B. caballi cultures. These results indicate that N-acetyl-L-cysteine might be used as a drug for the treatment of babesiosis, especially when used in combination with diminazene aceturate.

Contrast-induced nephropathy: Basic concepts, pathophysiological implications and prevention strategies

Contrast-induced nephropathy (CIN) is reversible acute renal failure observed following administration of iodinated contrast media (CM) during angiographic or other medical procedures such as urography. There are various mechanisms through which CM develop their nephrotoxic effects, including oxidative stress and apoptosis. CIN is a real-life, albeit not very rare, entity. Exact pathophysiology remains obscure and no standard diagnostic criteria apply. The Acute Kidney Injury Network criteria was recently employed but its incidence/clinical significance warrants further clarification based on recent methodological advancements, because most published studies to date were contaminated by bias. The current study is a comprehensive review conducted to provide an overview of the basic concepts of CIN and summarize recent knowledge on its pathophysiology and the evidence supporting potential prevention strategies. CIN is expected to increase morbidity, hospital stay and mortality, while all patients scheduled to receive CM should undergo risk assessment for CIN and high-risk patients may be considered candidates for prevention strategies. The value of using compounds with antioxidant properties other than sodium bicarbonate, remains controversial, warranting further clinical investigation.

Contrast-Induced Nephropathy in Renal Transplant Recipients: A Single Center Experience

BACKGROUND

Contrast-induced nephropathy (CIN) in native kidneys is associated with a significant increase in mortality and morbidity. Data regarding CIN in renal allografts are limited, however. We retrospectively studied CIN in renal allografts at our institution: its incidence, risk factors, and effect on long-term outcomes including allograft loss and death.

METHODS

One hundred thirty-five renal transplant recipients undergoing 161 contrast-enhanced computed tomography (CT) scans or coronary angiograms (Cath) between years 2000 and 2014 were identified. Contrast agents were iso- or low osmolar. CIN was defined as a rise in serum creatinine (SCr) by >0.3 mg/dl or 25% from baseline within 4 days of contrast exposure. After excluding 85 contrast exposures where patients had no SCr within 4 days of contrast administration, 76 exposures (CT: n = 45; Cath: n = 31) in 50 eligible patients were analyzed. Risk factors assessed included demographics, comorbid conditions, type/volume of contrast agent used, IV fluids, N-acetylcysteine administration, and calcineurin inhibitor use. Bivariate and multivariable analyses were used to assess the risk of CIN.

RESULTS

Incidence of CIN was 13% following both, CT (6 out of 45) and Cath (4 out of 31). Significant bivariate predictors of CIN were IV fluid administration (p = 0.05), lower hemoglobin (p = 0.03), and lower albumin (p = 0.02). In a multivariable model, CIN was predicted by N-acetylcysteine (p = 0.03) and lower hemoglobin (p = 0.01). Calcineurin inhibitor use was not associated with CIN. At last follow-up, CIN did not affect allograft or patient survival.

CONCLUSION

CIN is common in kidney transplant recipients, and there is room for quality improvement with regards to careful renal function monitoring post-contrast exposure. In our study, N-acetylcysteine exposure and lower hemoglobin were associated with CIN. Calcineurin inhibitor use was not associated with CIN. Our sample size is small, however, and larger prospective studies of CIN in renal allografts are needed.

Contrast-induced acute kidney injury: A review of practical points

Contrast-induced acute kidney injury (CI-AKI) is one of the most common causes of AKI in clinical practice. CI-AKI has been found to be strongly associated with morbidity and mortality of the patients. Furthermore, CI-AKI may not be always reversible and it may be associated with the development of chronic kidney disease. Pathophysiology of CI-AKI is not exactly understood and there is no consensus on the preventive strategies. CI-AKI is an active research area thus clinicians should be updated periodically about this topic. In this review, we aimed to discuss the indications of contrast-enhanced imaging, types of contrast media and their impact on nephrotoxicity, major pathophysiological mechanisms, risk factors and preventive strategies of CI-AKI and alternative non-contrast-enhanced imaging methods.