Radiographic contrast media induced nephropathy: experimental observations and the protective effect of calcium channel blockers

Molecular basis of the counteraction by calcium channel blockers of cyclosporine nephrotoxicity

Nephrotoxicity is a serious side effect for the immunosuppressant drug cyclosporine A(CSA). In this study, we tested the hypothesis that administration of calcium channel blockers such as verapamil or nifedipine ameliorates renal CSA-induced renal dysfunction. Furthermore, our study investigates the roles of inflammatory, oxidative, and fibrotic pathways in CSA-induced renal dysfunction. Six groups of male rats ( n = 6/group) were used and received one of the following treatments for seven consecutive days: vehicle (Cremophor EL ip), CSA (25 mg·kg^-1·day^-1 ip), verapamil (2 mg·kg^-1·day^-1 ip), nifedipine (3 mg·kg^-1·day^-1 ip), CSA in the presence or absence of either verapamil, or nifedipine. Biochemical and histomorphometric analyses showed that rats treated with CSA exhibited clear signs of nephrotoxicity that included 1) proteinuria and elevations in serum creatinine and blood urea nitrogen, 2) mesangial expansion, 3) increases in glomerular and tubular type IV collagen expression, and 4) increases in the glomerulosclerosis and tubulointerstitial fibrosis indices. Although the single administration of nifedipine or verapamil had no significant effect on renal pathology, or its biochemical and physiological function, the concurrent use of either calcium channel blockers significantly and equipotently ameliorated the biochemical, morphological, and functional derangements caused by CSA. More importantly, we report that the oxidative (reactive oxygen species production, NADPH-oxidase activity, and dual oxidase 1/2 levels), fibrotic (transforming growth factor-β1 expression), and inflammatory (NF-κB expression) manifestations of renal toxicity induced by CSA were significantly reversed upon administration of nifedipine or verapamil. Together, these results highlight the efficacy of calcium channel-blocking agents in attenuating CSA-induced nephrotoxicity and predisposing biochemical and molecular machineries.

Urine metabolomic analysis to detect metabolites associated with the development of contrast induced nephropathy

Objective

Contrast induced nephropathy (CIN) is a result of injury to the proximal tubules. The incidence of CIN is around 11% for imaging done in the acute care setting. We aim to analyze the metabolic patterns in the urine, before and after dosing with intravenous contrast for computed tomography (CT) imaging of the chest, to determine if metabolomic changes exist in patients who develop CIN.

Methods

A convenience sample of high risk patients undergoing a chest CT with intravenous contrast were eligible for enrollment. Urine samples were collected prior to imaging and 4 to 6 hours post imaging. Samples underwent gas chromatography/mass spectrometry profiling. Peak metabolite values were measured and data was log transformed. Significance analysis of microarrays and partial least squares was used to determine the most significant metabolites prior to CT imaging and within subject. Analysis of variance was used to rank metabolites associated with temporal change and CIN. CIN was defined as an increase in serum creatinine level of ≥ 0.5 mg/dL or ≥ 25% above baseline within 48 hours after contrast administration.

Results

We sampled paired urine samples from 63 subjects. The incidence of CIN was 6/63 (9.5%). Patients without CIN had elevated urinary citric acid and taurine concentrations in the pre-CT urine. Xylulose increased in the post CT sample in patients who developed CIN.

Conclusion

Differences in metabolomics patterns in patients who do and do not develop CIN exist. Metabolites may be potential early identifiers of CIN and identify patients at high-risk for developing this condition prior to imaging.

Exposure to Radiocontrast Agents Induces Pancreatic Inflammation by Activation of Nuclear Factor-κB, Calcium Signaling, and Calcineurin

BACKGROUND & AIMS

Radiocontrast agents are required for radiographic procedures, but these agents can injure tissues by unknown mechanisms. We investigated whether exposure of pancreatic tissues to radiocontrast agents during endoscopic retrograde cholangiopancreatography (ERCP) causes pancreatic inflammation, and studied the effects of these agents on human cell lines and in mice.

METHODS

We exposed mouse and human acinar cells to the radiocontrast agent iohexol (Omnipaque; GE Healthcare, Princeton, NJ) and measured intracellular release of Ca(2+), calcineurin activation (using a luciferase reporter), activation of nuclear factor-κB (NF-κB, using a luciferase reporter), and cell necrosis (via propidium iodide uptake). We infused the radiocontrast agent into the pancreatic ducts of wild-type mice (C57BL/6) to create a mouse model of post-ERCP pancreatitis; some mice were given intraperitoneal injections of the calcineurin inhibitor FK506 before and after infusion of the radiocontrast agent. CnAβ(-/-) mice also were used. This experiment also was performed in mice given infusions of adeno-associated virus 6-NF-κB-luciferase, to assess activation of this transcription factor in vivo.

RESULTS

Incubation of mouse and human acinar cells, but not HEK293 or COS7 cells, with iohexol led to a peak and then plateau in Ca(2+) signaling, along with activation of the transcription factors NF-κB and nuclear factor of activated T cells. Suppressing Ca(2+) signaling or calcineurin with BAPTA, cyclosporine A, or FK506 prevented activation of NF-κB and acinar cell injury. Calcineurin Aβ-deficient mice were protected against induction of pancreatic inflammation by iohexol. The calcineurin inhibitor FK506 prevented contrast-induced activation of NF-κB in pancreata of mice, this was observed by live imaging of mice given infusions of adeno-associated virus 6-NF-κB-luciferase.

CONCLUSIONS

Radiocontrast agents cause pancreatic inflammation in mice, via activation of NF-κB, Ca(2+) signaling, and calcineurin. Calcineurin inhibitors might be developed to prevent post-ERCP pancreatitis in patients.

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.

Antioxidant effect of Phyllanthus emblica extract prevents contrast-induced acute kidney injury

Background

Contrast-induced acute kidney injury (CI-AKI) occurs after the administration of intravenous iodinated contrast agents. Oxidative stress has been proposed as one of the most important mechanisms in the pathogenesis of CI-AKI. The objective of this study was to investigate the antioxidant effect of the extract from Phyllanthus emblica (PE) in preventing CI-AKI.

Methods

Male Sprague Dawley rats were subjected into eight groups, were given water (control) or PE extract (125 or 250 or 500 mg/kg/day) for 5 days before the induction of CI-AKI. Renal function and oxidative stress markers; malondialdehyde (MDA), total antioxidant capacity (TAC), superoxide dismutase (SOD) and catalase (CAT) activity were determined in plasma and renal tissue. Kidney sections were performed for histopathological examination.

Results

In the contrast media (CM) group, increases in blood urea nitrogen and serum creatinine were demonstrated which correlated with severity of tubular necrosis, peritubular capillary congestion and interstitial edema. Moreover, an increase in MDA and a decrease in TAC SOD and CAT activity in CM group were significantly changed when compared with the control (P < 0.05). In contrast, CI-AKI-induced rats administrated with PE extract 250 and 500 mg/kg/day significantly preserved renal function and attenuated the severity of pathological damage (P < 0.05) as well as significantly lower MDA and higher TAC, SOD and CAT than the CM group (P < 0.05).

Conclusions

This study demonstrated the protective role of PE extract against CI-AKI.

Comparison of effects of isotonic sodium chloride with diltiazem in prevention of contrast-induced nephropathy

INTRODUCTION AND OBJECTIVE

Contrast-induced nephropathy (CIN) significantly increases the morbidity and mortality of patients. The aim of this study is to investigate and compare the protective effects of isotonic sodium chloride with sodium bicarbonate infusion and isotonic sodium chloride infusion with diltiazem, a calcium channel blocker, in preventing CIN.

MATERIALS AND METHODS

Our study included patients who were administered 30-60 mL of iodinated contrast agent for percutaneous coronary angiography (PCAG), all with creatinine values between 1.1 and 3.1 mg/dL. Patients were divided into three groups and each group had 20 patients. The first group of patients was administered isotonic sodium chloride; the second group was administered a solution that of 5% dextrose and sodium bicarbonate, while the third group was administered isotonic sodium chloride before and after the contrast injection. The third group received an additional injection of diltiazem the day before and first 2 days after the contrast injection. All of the patients' plasma blood urea nitrogen (BUN) and creatinine levels were measured on the second and seventh day after the administration of intravenous contrast material.

RESULTS

The basal creatinine levels were similar for all three groups (p > 0.05). Among a total of 60 patients included in the study, 16 patients developed acute renal failure (ARF) on the second day after contrast material was injected (26.6%). The number of patients who developed ARF on the second day after the injection in the first group was five (25%), in the second group was six (30%) and the third group was five (25%) (p > 0.05).

CONCLUSION

There was no significant difference between isotonic sodium chloride, sodium bicarbonate and isotonic sodium chloride with diltiazem application in prevention of CIN.

Selective inhibition of the reverse mode of Na(+)/Ca(2+) exchanger attenuates contrast-induced cell injury

BACKGROUND

The precise mechanisms underlying radiocontrast nephropathy (RCN) are not well understood. Intracellular Ca(2+) overload is considered to be a key factor in RCN. The Na(+)/Ca(2+) exchanger (NCX) system is one of the main pathways of intracellular Ca(2+) overload. We investigated whether intracellular Ca(2+) overload via the NCX system was involved in contrast-induced renal tubular cytotoxicity.

METHODS

NRK-52E cells were exposed to ioversol (100 mg iodine/ml) for 4 h. KB-R7943 (inhibitor of reverse mode of NCX, 4 × 10(-5), 4 × 10(-6)M) was added 1 h before incubation with ioversol. Cell viability and permeability were determined by 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide and lactate dehydrogenase assay. Apoptosis was determined by flow cytometry. Intracellular Ca(2+) concentration ([Ca(2+)](i)] and reactive oxygen species (ROS) were detected by confocal microscopy. The expression of NCX1 mRNA and caspase-3 protein was evaluated by reverse transcription-polymerase chain reaction and Western blot, respectively.

RESULTS

Ioversol exposure induced significantly increased lactate dehydrogenase release and decreased 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide conversion in NRK-52E cells. Significantly increased apoptosis and caspase-3 protein expression were observed in the NRK-52E cells exposed to ioversol for 4 h. Ioversol treatment induced a significant increase in [Ca(2+)](i) and intracellular ROS. KB-R7943 dose-dependently and significantly suppressed the increase in [Ca(2+)](i), intracellular ROS and caspase-3 overexpression induced by ioversol and attenuated the contrast-induced NRK-52E cell apoptosis. No significant changes in NCX1 mRNA expression were observed following contrast exposure.

CONCLUSION

Intracellular Ca(2+) overload via the reverse mode of NCX, followed by ROS overproduction and caspase-3 overexpression played an important role in the contrast-induced renal tubular cytotoxicity. The reverse mode of the NCX inhibitor KB-R7943 attenuated contrast-induced renal tubular cytotoxicity.

Radiographic assessment of splenic injury without contrast: is contrast truly needed?

INTRODUCTION

Computed tomography (CT) has become an essential tool in the assessment of the stable trauma patient. Intravenous (i.v.) contrast is commonly relied upon to provide superior image quality, particularly for solid-organ injury. However, a substantial proportion of injured patients have contraindications to i.v. contrast. Little information exists concerning the repercussions of CT imaging without i.v. contrast, specifically for splenic injury.

METHODS

We performed a retrospective analysis using data from our trauma registry and chart review as part of a quality improvement project at our institution. All patients with splenic injury, during a 3-year period (2008-2010), where a CT of the abdomen without i.v. contrast (DRY) early during their admission were selected. All splenic injuries had to have been verified with abdominal CT imaging with i.v. contrast (CONTRAST) or via intraoperative findings. DRY images were independently read by a single, blinded, radiologist and assessed for parenchymal injury or "suspicious" splenic injury findings and compared with CONTRAST imaging results or intraoperative findings.

RESULTS

During the time period of the study, 319 patients had documented splenic injury with 44 (14%) patients undergoing DRY imaging, which was also verified by CONTRAST imaging or operative findings. Splenic parenchymal injury was only visualized in 38% of patients DRY patients. "Suspicious" splenic injury radiographic findings were common. When these less-specific findings for splenic injury were incorporated in the radiographic assessment, DRY imaging had more than 93% sensitivity for detecting splenic injury.

CONCLUSION

DRY imaging is increasingly being performed after injury and has a low sensitivity in detecting splenic parenchymal injury. However, less-specific radiographic findings suspicious for splenic injury in combination provide high sensitivity for the detection of splenic injury. These results suggest CONTRAST imaging is preferred to detect splenic injury; however, in those patients who have contraindications to i.v. contrast, DRY imagining may be able to select those who require close monitoring or intervention.

Beneficial effects of high-dose atorvastatin pretreatment on renal function in patients with acute ST-segment elevation myocardial infarction undergoing emergency percutaneous coronary intervention

OBJECTIVES

To investigate whether preprocedural high-dose atorvastatin decreases the incidence of contrast-induced nephropathy (CIN) and protects the renal function after emergency percutaneous coronary intervention (PCI).

METHODS

Statin-naive patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing emergency PCI (n = 161) randomly received atorvastatin (80 mg, n = 78, ATOR group) or placebo [n = 83, control (CON) group] followed by long-term atorvastatin (40 mg/day). The primary end point was incidence of CIN.

RESULTS

In the ATOR group, 2.6% of the patients developed CIN versus 15.7% in the CON group (p = 0.01). In the ATOR group, postprocedural serum creatinine was significantly lower (93.4 ± 17.1 vs. 112.6 ± 23.3 µmol/l at 48 h and 84.2 ± 14.2 vs. 95.3 ± 17.7 µmol/l at 72 h, both p < 0.0001) and in the CON group, peak serum cystatin C was lower (0.51 ± 0.14 vs. 0.61 ± 0.13 mg/l, p < 0.0001). Atorvastatin pretreatment was independently associated with a decreased risk of CIN (OR 0.084, 95% CI 0.015-0.462, p = 0.004). The proportion of alanine aminotransferase > 3 × upper limit of the normal value within 1 month was 3.85 versus 1.20% (ATOR vs. CON group, p = 0.57).

CONCLUSION

Preprocedural high-dose atorvastatin prevents CIN and protects the renal function in patients with acute STEMI undergoing emergency PCI.

Acetylcysteine and non-ionic isosmolar contrast-induced nephropathy--a randomized controlled study

INTRODUCTION

Intravenous administration of saline and non-ionic isosmolar contrast media significantly reduces the incidence of contrast-induced nephropathy, one of the most common causes of acute renal failure. Results with oral N-acetylcysteine are conflicting. The aim of our study was to evaluate the prophylactic role of N-acetylcysteine in patients with stable chronic renal failure undergoing coronary and/or peripheral angiography and/or angioplasty.

METHODS

We randomized 200 elective, consecutive patients (mean age 74.9 +/- 7.3 years; 65% male, 25% diabetics) with basal creatinine clearance <or=55 ml/min to receive oral N-acetylcysteine (600 mg bid the day before and the day of the procedure plus saline i.v. 0.9% 1 ml/kg/h 12-24 h before and 24 h after the procedure, n = 99) or placebo and saline at the same time intervals, n = 101. The contrast medium was non-ionic isosmolar (Iodixanol, Visipaque Amersham Health). Contrast-induced nephropathy was defined as an increase in serum creatinine >0.5 mg/dl or >25% within 3 days after the procedure. Serum creatinine was measured at baseline, 24, 48 and 72 h after the procedure.

RESULTS

Contrast-induced nephropathy was 8/99 (8.1%) in the N-acetylcysteine group versus 6/101 (5.9%) in the placebo group, P = 0.6. No difference was noted in high-risk subgroups such as diabetics (4/25 versus 2/25 P = 0.4) and those with serum creatinine clearance <42.3 ml/min (5/54 versus 4/48; P = 0.9).

CONCLUSION

In our experience, N-acetylcysteine did not prevent contrast-induced nephropathy in patients receiving isosmolar (iodixanol) contrast media and adequate hydration.

Biomedical imaging in the safety evaluation of new drugs

Toxicology accounts for approximately one-third of attrition in new drug development and is a major concern in the pharmaceutical industry. This paper reviews the role of biomedical imaging in the safety evaluation of new candidate drugs. Ex vivo high-resolution three-dimensional imaging of specimens can provide a quick overview of the specimens. Volumetric measurements of tissue structures and lesions can be made with higher precision and reproducibility than histology approaches. As opposed to histology, in vivo animal imaging permits longitudinal studies of the same animals over an extended period of time, with individual animals serving as their own control. Therefore, the number of animals required for a study can be significantly reduced and the intra-subject variability is minimized. Repeated in vivo imaging allows monitoring of the occurrence and progression, or regression, of various structural and functional abnormalities. Compared with other biological assays, imaging can provide anatomically specific information about tissue abnormality. Imaging offers the opportunity to carry forward the same methodology in animal experiments into human studies and has an important role in clinical trials when other safety biomarkers for early toxicities are not available.

Pathophysiology of contrast-induced nephropathy

Contrast-induced nephropathy (CIN) is the third leading cause of acute kidney injury in hospitalized patients and is associated with significant patient morbidity. The pathogenesis of CIN is complex and not fully understood, but iodinated contrast agents induce intense and prolonged vasoconstriction at the corticomedullary junction of the kidney. Moreover, high-osmolar dyes directly impair the autoregulatory capacity of the kidney through a loss of nitric oxide production. These effects, coupled with direct tubular toxicity of contrast media, lead to overt acute tubular necrosis and the syndrome of CIN.

Contrast-induced nephropathy: preventive and protective effects of melatonin

Infusion of contrast agents increases osmotic load, viscosity, hypoxemia of the renal medulla and renal free radical production through post-ischemic oxidative stress. The present experimental study sought to determine whether melatonin, because of its anti-oxidant properties might have a preventive and protective role against the development of contrast-induced nephropathy (CIN). Twenty-four adult male rats were divided into four experimental groups: healthy control rats (CR), rats with CIN (CINR), rats with CIN pretreated with melatonin (CINR1M), and rats with CIN pre- and post-treated with melatonin (CINR2M). In CINR, both serum creatinine (Cr) level and fractional excretion of sodium (FE-Na) significantly increased, whereas Cr clearance decreased at post-CIN compared with pre-CIN period. Rats in CINR1M did not show any improvement in renal function. Cr clearance decreased, whereas both serum Cr level and FE-Na increased in rats pretreated with melatonin. In contrast, significant improvements were observed in CINR2M. Serum Cr and Cr clearance did not change, whereas FE-Na significantly reduced in rats pre- and post-treated with melatonin. In conclusion, the present experimental study clearly demonstrated the preventive and protective role of melatonin against the development of CIN.

Contrast-induced nephropathy: Pharmacological prophylaxis

Contrast media-associated acute renal failure represents the third most common cause of in-hospital renal function deterioration after decreased renal perfusion and post-operative renal insufficiency. Although generally benign, this complication is associated with a mortality rate ranging from 3.8 to 64%, depending on the increase of creatinine concentration. Multiple drugs have been tested in an attempt to prevent this complication. Central to the pathophysiology of contrast-induced nephrotoxicity (CIN) is an alteration in renal hemodynamics. In an effort to reverse these hemodynamic changes, vasodilators and diuretics have been tested as prophylactic drugs. However, their effectiveness has not been confirmed. Recently, considerable interest has resulted from the initial positive data on the effectiveness of prophylactic administration of antioxidant compounds, such as acetylcysteine and ascorbic acid. In this review, we focus on the effectiveness of pharmacologic therapies for preventing CIN.

A prostacyclin analog prevents radiocontrast nephropathy via phosphorylation of cyclic AMP response element binding protein

We reported previously that radiocontrast medium induces caspase-dependent apoptosis and that cAMP analogs inhibit cell injury in cultured renal tubular cells. In the present study, cellular mechanisms underlying the protective effects of cAMP were determined. Ioversol, a radiocontrast medium, caused cell injury accompanied by decreases in Bcl-2, increases in Bax, and caspase activation in LLC-PK1 cells. Both cell injury and cellular events induced by ioversol were inhibited by dibutyryl cAMP and the prostacyclin analog beraprost. Dibutyryl cAMP increased phosphorylation of Akt and CREB, both of which were reversed by H89, wortmannin and the Akt inhibitor SH-6. The protective effect of dibutyryl cAMP was also reversed by these kinase inhibitors. In dominant-negative CREB-transfected cells, dibutyryl cAMP no longer prevented cell injury or inhibited changes in mRNA expression of Bcl-2 and Bax. In mice with unilateral renal occlusion, ioversol increased urinary excretion of N-acetyl-beta-d-glucosaminidase with concomitant decreases in Bcl-2 mRNA, increases in Bax mRNA, activation of caspase-3, and induction of apoptosis in tubular and interstitial cells. Beraprost completely reversed these in vivo effects of ioversol. These findings suggest that elevation of endogenous cAMP effectively prevents radiocontrast nephropathy through activation of A kinase/PI 3-kinase/Akt followed by CREB phosphorylation and enhanced expression of Bcl-2.

Contrast nephropathy, pathophysiology and prevention

Contrast nephropathy is a common cause of iatrogenic acute renal failure. Its incidence rises with the growing use of intra-arterial contrast in diagnostic and interventional procedures. Aim of the present review is to summarize the knowledge about pathophysiology and prevention. Nephrotoxicity is related to osmolality, dose and route of the contrast and only occurs in synergy with other factors, such as previous renal impairment and cardiovascular disease. With an interplay of these factors, contrast nephropathy has an impact on morbidity and mortality. Pathophysiological mechanisms are intrarenal vasoconstriction, leading to medullary ischemia, direct cytotoxicity, oxidative tissue damage and apoptosis. Several measures are of proven benefit in patients at risk. Among them are discontinuation of potentially nephrotoxic drugs, hydration, preferably with isotonic sodium bicarbonate, use of low osmolal contrast, oral or intravenous N-acetylcysteine and intravenous theophylline. In patients with severe cardiac and renal dysfunction undergoing cardiac interventions, periprocedural hemofiltration may be considered.

Prevention of Contrast Media–induced Nephrotoxicity after Angiographic Procedures

Contrast medium-induced nephrotoxicity (ie, contrast nephrotoxicity [CN]) remains an important complication of angiographic procedures. If administration of iodinated contrast medium is deemed necessary in patients at high risk of CN, volume expansion should be offered and the lowest possible dose of nonionic isosmolar dimeric or nonionic low-osmolar monomeric contrast medium should be used. Prophylactic administration of fenoldopam or acetylcysteine has not offered consistent protection against CN. Intravenous acetylcysteine could be considered in emergency situations. Recently, sodium bicarbonate infusion has been shown to reduce the risk of CN. Hemofiltration for several hours before and after contrast medium injection may offer good protection against CN in patients with advanced renal disease. Prophylactic hemodialysis does not offer any protection against CN.

Clinical and Experimental Evidence for Prevention of Acute Renal Failure Induced by Radiographic Contrast Media

Acute renal failure still occurs as a complication after radiographic examination using iodinated radiocontrast medium. The incidence rate of radiocontrast medium-induced nephropathy (radiocontrast nephropathy) is low (2 - 3%) in general. However, the rate is remarkably elevated in patients with pre-existing renal insufficiency. Radiocontrast nephropathy is associated with increased morbidity and mortality, particularly in patients with percutaneous coronary interventions. Although the reduction in renal blood flow and direct toxic action on renal tubular cells are considered to be involved, little is known about the etiology of radiocontrast nephropathy. A number of agents that improve renal circulation have been clinically tested for prevention of radiocontrast nephropathy, but none of them has succeeded. Protection of renal tubular cells against oxidative stress is another approach to avoid radiocontrast nephropathy. Prophylactic effects of antioxidants such as N-acetylcysteine and ascorbic acid have been reported by several investigators, although the effectiveness of these compounds is still a matter of debate. At present, hydration is regarded as the only effective, though incomplete, prophylactic regimen for radiocontrast nephropathy. Recently, we have shown that caspase-dependent apoptosis is an important factor in the pathogenesis of radiocontrast nephropathy and clarified cellular mechanisms underlying the radiocontrast media-induced apoptosis. This review summarizes clinical and experimental evidence for the etiology and prevention of radiocontrast nephropathy.

Preventing contrast nephropathy: what is the best strategy? A review of the literature

Patients receiving radiocontrast for diagnostic and interventional procedures are at risk for developing contrast nephropathy (CN). In fact, radiocontrast nephropathy is currently the third leading cause of hospital-acquired renal failure. Understanding that CN has been associated with increased length of hospitalization and mortality, determining the best prevention strategy is of utmost importance. Patients at the greatest risk for developing acute renal failure are patients with diabetes and underlying renal insufficiency. Several therapies have been investigated for the prevention of CN; unfortunately, very few have shown a consistent benefit. Therapies that have been studied include saline hydration, N-acetylcysteine (NAC), theophylline, calcium channel blockers, diuretics, dopamine, endothelin receptor antagonists, atrial natriuretic peptide, angiotensin-converting enzyme inhibitors, and prostaglandin E-1. Using adequate hydration, using low-osmolar dyes, and minimizing the dose of contrast have all been shown to be effective in reducing CN and are considered the standard of care. While trials with many pharmacologic agents have produced conflicting results, intervention with NAC has also been promising. This article reviews the pathophysiology, risk factors, and therapies that are currently available for the prevention of CN.

Prevention of contrast media nephrotoxicity--the story so far

Contrast media nephrotoxicity (CMN) in patients with pre-existing renal impairment remains a clinically significant problem. The first step to reduce the chance of CMN is to identify patients at risk through the use of screening questionnaires and renal function measurement. Patients at risk requiring injection of contrast medium (CM) because of important clinical indications should receive a small dose of either non-ionic iso-osmolar dimeric or non-ionic low osmolar monomeric CM and hydration. Intravenous infusion (1 ml/kg body weight/h) of 0.9% saline starting 4 h before CM injection and continuing for at least 12 h afterwards is effective in reducing the incidence of CMN. Prophylactic haemodialysis does not lower the risk of this complication. The value of pharmacological manipulation with renal vasodilators (calcium channel blockers, dopamine, atrial natriuretic peptide, fenoldopam (selective dopamine-1 receptor agonist), prostaglandin E(1), non-selective adenosine receptors antagonist (theophylline), non-selective endothelin receptor antagonist or the antioxidant acetylcysteine has not been fully proven. However, haemofiltration for several hours before and after contrast medium injection offers good protection against CMN in patients with advanced renal disease.

Prophylaxis of Iodinated Contrast Media-Induced Nephropathy

Iodinated contrast media are a frequent cause of acute renal failure, especially in patients whose renal function is already impaired. In addition to hydration, which remains the most commonly acknowledged means of protection, numerous pharmacological approaches for the prophylaxis of contrast nephropathy have been tested so far. They include diuretics, calcium channel blockers, adenosine receptor antagonists, N-acetylcysteine, low-dose dopamine and the dopamine D1 receptor agonist fenoldopam, endothelin receptor antagonists, and even captopril. The present review of the literature critically discusses the drugs used to prevent contrast nephropathy from a pharmacological point of view.

Ionic radiocontrast inhibits endothelium-dependent vasodilation of the canine renal artery in vitro: possible mechanism of renal failure following contrast medium infusion

To determine if radiocontrast impairs vascular relaxation of the renal artery, segments (4-5 mm in length) of canine renal artery were suspended in vitro in organ chambers to measure isometric force (95% O2/5% CO2, at 37 C). Arterial segments with and without endothelium were placed at the optimal point of their length-tension relation and incubated with 10 microM indomethacin to prevent synthesis of endogenous prostanoids. The presence of nonionic radiocontrast (iohexol, Omnipaque 350, 1 ml in 25 ml control solution, 4% (v/v)) did not alter endothelium-dependent relaxation to acetylcholine in rings precontracted with both norepinephrine and prostaglandin F2alpha (N = 6). When the rings were precontracted with prostaglandin F2alpha, the presence of ionic contrast did not inhibit the relaxation of the arteries. However, in canine renal arteries contracted with norepinephrine, the presence of ionic radiocontrast (diatrizoate meglumine and diatrizoate sodium, MD-76, 1 ml in 25 ml control solution, 4% (v/v)) inhibited relaxation in response to acetylcholine, sodium nitroprusside (N = 6 in each group), and isoproterenol (N = 5; P < 0.05). Rings were relaxed less than 50% of norepinephrine contraction. Following removal of the contrast, vascular relaxation in response to the agonists returned to normal. These results indicate that ionic radiocontrast nonspecifically inhibits vasodilation (both cAMP-mediated and cGMP-mediated) of canine renal arteries contracted with norepinephrine. This reversible impairment of vasodilation could inhibit normal renal perfusion and act as a mechanism of renal failure following radiocontrast infusion. In the adopted experimental protocol the isoproterenol-induced relaxation of renal arteries precontracted with norepinephrine was more affected, suggesting a pivotal role of the cAMP system.

Radiocontrast-induced nephropathy and percutaneous coronary intervention: a review of preventive measures

Injectable and absorbable contrast media for the use in radiology, all of which contains iodine as an essential component, has been, and continues to be, one of the main sources of agents which cause hospital-acquired renal failure. Although numerous methods have been explored to prevent renal contrast damage, radiocontrast-induced nephropathy continues to be a concern in patients with existing renal insufficiency, who undergo contrast-enhanced radiographic examinations. Patients who develop contrast-induced nephropathy (CIN) have a worse prognosis and an increased risk of complications and mortality. Prevention of CIN during radiocontrast procedures continues to elude clinicians and is a chief concern during percutaneous coronary intervention, as these patients often have multiple comorbidities. A wide variety of animal and clinical investigations, and substances have been tried in order to prevent this complication, including: dialysis, contrast volume and type; adenosine antagonists; acetylcysteine; fenoldopam; and various others. The purpose of this review is to appraise all the past and current strategies employed to prevent CIN, especially during percutaneous coronary intervention.

Nephrotoxic effects in high-risk patients undergoing angiography

BACKGROUND

The use of iodinated contrast medium can result in nephropathy. Whether iso-osmolar contrast medium is less nephrotoxic than low-osmolar contrast medium in high-risk patients is uncertain.

METHODS

We conducted a randomized, double-blind, prospective, multicenter study comparing the nephrotoxic effects of an iso-osmolar, dimeric, nonionic contrast medium, iodixanol, with those of a low-osmolar, nonionic, monomeric contrast medium, iohexol. The study involved 129 patients with diabetes with serum creatinine concentrations of 1.5 to 3.5 mg per deciliter who underwent coronary or aortofemoral angiography. The primary end point was the peak increase from base line in the creatinine concentration during the three days after angiography. Other end points were an increase in the creatinine concentration of 0.5 mg per deciliter or more, an increase of 1.0 mg per deciliter or more, and a change in the creatinine concentration from day 0 to day 7.

RESULTS

The creatinine concentration increased significantly less in patients who received iodixanol. From day 0 to day 3, the mean peak increase in creatinine was 0.13 mg per deciliter in the iodixanol group and 0.55 mg per deciliter in the iohexol group (P=0.001; the increase with iodixanol minus the increase with iohexol, -0.42 mg per deciliter [95 percent confidence interval, -0.73 to -0.22]). Two of the 64 patients in the iodixanol group (3 percent) had an increase in the creatinine concentration of 0.5 mg per deciliter or more, as compared with 17 of the 65 patients in the iohexol group (26 percent) (P=0.002; odds ratio for such an increase in the iodixanol group, 0.09 [95 percent confidence interval, 0.02 to 0.41]). No patient receiving iodixanol had an increase of 1.0 mg per deciliter or more, but 10 patients in the iohexol group (15 percent) did. The mean change in the creatinine concentration from day 0 to day 7 was 0.07 mg per deciliter in the iodixanol group and 0.24 mg per deciliter in the iohexol group (P=0.003; value in the iodixanol group minus the value in the iohexol group, -0.17 mg per deciliter [95 percent confidence interval, -0.34 to -0.07]).

CONCLUSIONS

Nephropathy induced by contrast medium may be less likely to develop in high-risk patients when iodixanol is used rather than a low-osmolar, nonionic contrast medium.