Influence of contrast media on the response of rat renal arteries to endothelin and nitric oxide: influence of contrast media

Pathophysiology of renal tissue damage by iodinated contrast media

1. The present review focuses on the cytotoxic effects of iodinated contrast media (CM) that are shared by all types of CM. 2. Although the clinical nephrotoxicity of CM has been progressively improved, all currently available CM still possess a level of cytotoxicity, which is probably caused by iodine. 3. The toxicity caused by specific CM properties, such as osmolarity, viscosity and ionic strength, can be differentiated from the cytotoxicity common to all CM in studies using cell culture, isolated blood vessels and isolated tubules. 4. The cytotoxicity induced by CM leads to apoptosis and cell death of endothelial and tubular cells and may be initiated by cell membrane damage, together with oxidative stress. 5. Cell damage may be aggravated by factors such as tissue hypoperfusion and hypoxia, properties of individual CM, such as ionic strength, high osmolarity and/or viscosity, and clinically unfavourable conditions. 6. Clinically detectable renal failure may result from the summation of all these factors.

Toxic effects of a high dose of non-ionic iodinated contrast media on renal glomerular and aortic endothelial cells in aged rats in vivo

Iodinated contrast media (CM) can induce apoptosis and necrosis of renal tubular cells. The injuries of endothelial cells induced by CM on the systemic condition have not been fully understood. To assess the toxic effects of non-ionic CM on the glomerular and aortic endothelial cells, iopromide and iodixanol, two kinds of representative non-ionic CM, were used for the in vivo study. Sixty aged rats were respectively received the agents or normal sodium intravascularly. No obvious apoptosis and morphological change was detected in the glomerular and aortic endothelial cells apart from renal tubules after CM administration. However, expressions of the nitric oxide synthase (eNOS) in glomerular endothelium were decreased at 12h after CM injection. Furthermore, plasma creatinine and endothelin-1 were increased and plasma nitric oxide (NO) was decreased significantly after CM administration. However, we failed to observe the significant increase of plasma von Willebrand Factor. These results suggest that non-ionic iodinated CM do not induce apoptosis and necrosis of glomerular and aortic endothelial cells in vivo. Decreased eNOS expression and increased plasma endothelin-1 may be involved in non-ionic iodinated CM-induced endothelial dysfunction and kidney injury.

Contrast nephropathy may be partly mediated by autonomic dysfunction: renal failure considered as a modern maladaptation of the prehistoric trauma response

The mechanism behind iodinated radiocontrast nephropathy remains elusive. Direct oxidative damage is the prevailing hypothesis, but the apparent protective effect of iodine against oxidation contradicts this view. We propose that autonomic dysfunction participates in the pathogenesis of radiocontrast nephropathy and may account for other contrast-associated reactions previously attributed to allergy. Iodine, through its effects on thyroid function and chemoreceptor response to metabolic acidosis, may induce hyperadrenergia and consequently diminish renovascular flow and urine output. The renal response to adrenergia likely served an adaptive function during prehistoric evolution when trauma was a dominant source of hypovolemia and adrenergia, but the response may behave maladaptively today as evolutionarily nai ve triggers for adrenergia have emerged. Autonomic dysfunction can further impair renal function by deranging renovascular autoregulation and inducing oxidative reperfusion injury as a secondary phenomenon. Many other causes of acute renal failure such as drug toxicity, surgery, hospitalization, and diabetes may operate through hyperadrenergia, impaired renovascular autoregulation, and oxidative reperfusion injury. Dialysis, a volume reduction therapy for renal failure, can counterintuitively worsen renal dysfunction by exacerbating adrenergia, which may explain its association with accelerated atherosclerosis, inflammation, and cancer. Other examples of vicious cycles that perpetuate renal dysfunction may include renal artery stenosis, carotid stenosis, and atherosclerosis as well as the cardio-renal, hepato-renal, and pulmonary-renal syndromes. The benefits of hydration and bicarbonate in protecting renal function may operate in part through baroreceptor- and chemoreceptor-mediated reduction of sympathovagal ratio, respectively. New treatment paradigms for renal failure including pharmacologic and electro-mechanical therapies are envisioned based on autonomic remodeling, reduced sympathovagal ratio, and neuromodulation of pathways typically associated with trauma such as renin, angiotensin, vasopressin, and aldosterone.

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.

N-acetylcysteine for the prevention of contrast-induced nephropathy. A systematic review and meta-analysis

OBJECTIVE

Contrast-induced nephropathy is a common cause of acute renal failure in hospitalized patients. Although patients are often given N-acetylcysteine to prevent renal injury from contrast agents, there are no clear guidelines supporting its use. We conducted a systematic review to determine whether administering N-acetylcysteine around the time of contrast administration reduces the risk of contrast-induced nephropathy.

DESIGN

We searched MEDLINE, EMBASE, the Cochrane Collaboration Database, bibliographies of retrieved articles, and abstracts of conference proceedings, and consulted with experts to identify relevant studies. Randomized controlled trials of N-acetylcysteine in hospitalized patients receiving contrast were included. Studies were excluded if they did not report change in creatinine or incidence of contrast-induced nephropathy at 48 hours.

MEASUREMENTS AND MAIN RESULTS

Nine randomized controlled trials satisfied all inclusion criteria and were included in the analysis. The difference in mean change in creatinine between the N-acetylcysteine-treated group and controls was -0.27 mg/dl (95% confidence interval [CI], -0.43 to -0.11). The relative risk of developing contrast-induced nephropathy was 0.43 (95% CI, 0.24 to 0.75) in subjects randomized to N-acetylcysteine. Significant heterogeneity existed among studies, suggesting differences in patient populations or study methodology not identified by sensitivity analyses. The incidence of dialysis was rare (0.2%).

CONCLUSIONS

Our findings suggest that N-acetylcysteine helps prevent declining renal function and contrast-induced nephropathy. While N-acetylcysteine is inexpensive and nontoxic, undeviating insistence for dosing at least 12 hours in advance of contrast exposure may delay diagnostic and therapeutic procedures. Future studies are needed to address the longer-term clinical outcomes and cost-effectiveness of this agent.

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.

Contrast media research

This selective review highlights research in contrast media development and application in the field of diagnostic radiology in 1998 and 1999. The focus is on research published in Investigative Radiology, supplemented with work from other publications in the few areas not extensively covered by the journal. Studies continue to be performed, although at a low level, examining safety issues. Most preclinical investigations have focused on MR and ultrasound agents. In MR, the research effort is concentrated on the development of targeted agents; in ultrasound, work is focused on the characterization of basic contrast mechanisms. The demonstration of clinical applications is still dominated by work with MR, both in disease models and human investigations. The use of extracellular gadolinium chelates to enhance visualization of blood vessels (the field of contrast-enhanced MR angiography) is the largest single new clinical application of contrast media to emerge in several years. New clinical applications continue to be pursued with contrast media in CT, ultrasound, and x-ray angiography. As intravenously injected ultrasound contrast agents come to market, trials demonstrating clinical applications and subsequent scientific publications will increase in number.