Contrast-associated nephropathy

The place of hydration using intravenous fluid in patients at risk of developing contrast-associated nephropathy

There has been a significant rise in the incidence of contrast-associated nephropathy caused by administration of contrast media during cardiac interventions. This is one of the major complications of percutaneous coronary interventions, which may proceed to acute renal failure. Risk factors, including pre-existing renal dysfunction, older age and use of high osmolar contrast media, predispose patients to the development of contrast-associated nephropathy. Different risk-reduction strategies have been used to prevent contrast-associated nephropathy, including use of low osmolar contrast media, N-acetylcysteine, alkalisation of tubular fluid with intravenous sodium bicarbonate, and oral and intravenous hydration with isotonic solution. Hydration using intravenous saline is one of the main treatments used to prevent the development of nephropathy in patients receiving contrast media during cardiac interventions. Prehydration, before administering contrast media, seems to be crucial. The results of studies of the relative efficacy of sodium bicarbonate and/or N-acetylcysteine in reducing the development of contrast-associated nephropathy are not consistent and any beneficial effects may depend on the pre-existing state of the kidney. This review discusses hydration of patients who are at risk of developing contrast-associated nephropathy using intravenous fluid.

An evaluation of the antioxidant properties of iodinated radiographic contrast media: An in vitro study

This study reveals the antioxidant properties of iodinated radiographic contrast media to be used in diagnostic radiology. Di(phenyl)-(2,4,6-trinitrophenyl) iminoazanium (DPPH), ferric reducing ability of plasma (FRAP), and 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) assays were used for determining in vitro the antioxidant properties of five iodinated radiographic contrast media such as iobitridol (xenetix), iodixanol (visipaque), iohexol (omnipaque), ioxaglate (hexabrix), and isovue (iopamiro). An ascorbic acid and Trolox solution served as a positive control. The absorbance intensity of the colored product was recorded using a spectrophotometer. For DPPH and ABTS assay, the absorbance intensity at 533 and 752 nm, respectively was decreased when compared to control; it indicated an increase in antioxidant activity. For FRAP assay, the absorbance intensity at 593 nm was increased when compared to control; it indicated an increase in antioxidant activity. The results showed that five iodinated radiographic contrast media did not differ in DPPH^• radical-scavenging activity when compared to a corresponding control. The ferric reducing ability of all of these iodinated radiographic contrast media also did not differ when compared to a corresponding control, except for iobitridol at 200 mgI/mL and ioxaglate at 50-200 mgI/mL. All iodinated radiographic contrast media showed ABTS^•+ radical-scavenging activity. This finding suggested that iobitridol, iodixanol, iohexol, ioxaglate, and isovue exhibited weak in vitro antioxidant properties. The antioxidant ability depended on the type of free radical production and the concentration of iodinated radiographic contrast media.

Nephroprotective potential of carnitine against glycerol and contrast-induced kidney injury in rats through modulation of oxidative stress, proinflammatory cytokines, and apoptosis

OBJECTIVE

Contrast media (CM) are a major cause of nephropathy in high-risk patients. The aim of this study was to examine the effects of carnitine (CAR) in advanced nephrotoxicity due to CM administration in rats with glycerol-induced renal functional disorder.

METHODS

40 rats were divided randomly into five groups (n = 8): (1) healthy group; (2) glycerol only (GLY); (3) glycerol and CM (GLY + CM); (4) glycerol, CM and 200 mg kg(-1) carnitine (CAR200, Carnitene(®); Sigma-tau/Santa Farma, Istanbul, Turkey); and (5) glycerol, CM and 400 mg kg(-1) carnitine (CAR400). Kidney injury was induced with a single-dose, intramuscular injection of 10 ml kg(-1) body weight (b.w.) of GLY. CAR was administered intraperitoneally. CM (8 ml kg(-1) b.w. iohexol, Omnipaque™; Opakim Medical Products, Istanbul, Turkey) was infused via the tail vein to the rats in Groups 3-5.

RESULTS

l-carnitine administration significantly decreased serum creatinine and blood urea nitrogen levels. Superoxide dismutase and glutathione activity increased significantly in the treatment groups compared with the nephrotoxic groups. CAR400 significantly reduced malondialdehyde levels to healthy levels. In the treatment groups, tumour necrosis factor (TNF)-α, transforming growth factor 1β, interleukin 1β and caspase-3 gene expression decreased compared with the nephrotoxic groups. TNF-α and nuclear factor kappa-beta (NF-κB) protein expression increased after CM and CAR administration reduced both TNF-α and NF-κB expressions. Histopathologically, hyaline and haemorrhagic casts and necrosis in proximal tubules increased in the nephrotoxicity groups and decreased in the CAR groups.

CONCLUSION

The results reveal that l-carnitine protects the oxidant/antioxidant balance and decreases proinflammatory cytokines and apoptosis in CM-induced nephrotoxicity in rats with underlying pathology.

ADVANCES IN KNOWLEDGE

Depending on the underlying kidney pathologies, the incidence of CM-induced nephropathy (CIN) increases. Therefore, this is the best model to represent clinically observed CIN.

Ionic high-osmolar contrast medium causes oxidant stress in kidney tissue: partial protective role of ascorbic acid

It has been known that contrast medium may cause contrast-induced nephropathy in risk groups. This study sought to establish possible effects of ionic high-osmolar contrast medium administration with or without antecedent cisplatin treatment on oxidant/antioxidant status in rat kidney tissues, as well as to investigate a possible protective role of antioxidant ascorbic acid in this regard. Thirty-five female, 14-week-old Wistar-albino rats were used in this study. They were divided into five groups of seven rats (sham, contrast, contrast + ascorbic acid, contrast + cisplatin, and contrast + cisplatin + ascorbic acid). Ascorbic acid was given in a dose of 250 mg/kg/day orally throughout the study period, and cisplatin (10 mg/kg) as a single i.v. dose on the fourth day. Ionic high-osmolar contrast medium (3 gr/kg iodine as a single dose) was administered by i.v. route on the fifth day. After the animals were sacrificed on the sixth day, their kidney tissues were removed surgically to be used in the analyses. Malondialdehyde (MDA) level and activities of antioxidant (superoxide dismutase [SOD], glutathione peroxidase [GSH-Px] and catalase [CAT]) and oxidant (xanthine oxidase [XO]) enzymes were measured in these samples. Serum urea and creatinine levels were measured to evaluate kidney functions. Histopathological investigation of the tissues was also performed. It was observed that contrast medium administration caused increases in MDA levels in the kidney tissues, either alone or together with antecedent cisplatin treatment. However, ascorbic acid prevented the increases in MDA levels in the kidney tissues. Histopathological findings revealed that ionic high-osmolar contrast medium administration alone led to mild acute structural damage, but contrast medium administration together with antecedent cisplatin usage caused severe tubular necrosis. Ascorbic acid supplementation prevented these changes, to a great extent. The results suggest that ionic high-osmolar contrast medium administration, either alone or together with antecedent cisplatin treatment, leads to accelerated oxidative reactions in rat kidney tissues, and ascorbic acid protects in part the kidney tissues against this oxidant stress.

Evaluation of the nephrotoxicity of iodixanol in patients with predisposing factors to contrast medium induced nephropathy referred for contrast enhanced computed tomography

To determine the risk of developing contrast induced nephropathy (CIN) in intermediate-risk patients receiving iodixanol, an iso-osmolar, dimeric non-ionic contrast agent, for CT in a clinical setting. Hundred consecutive patients referred for a contrast enhanced CT with a serum creatinine concentration>1.1mg/dl and/or a glomerular filtration rate (GFR)<90ml/min were included. Exclusion criteria were a serum creatinine>2.0mg/dl and a GFR<30ml/min or concurrent nephrotoxic agents. Between 60 and 140ml (mean 97+/-42ml) iodixanol (320mgI/ml) were administered at a flow of 2.5-3ml/s. Hydration with 500ml NaCl i.v. was performed before and after contrast injection. Follow-up was completed in 99 patients (age, 64+/-13 years, 68 men). CIN was defined as increase in serum creatinine concentration +0.5mg/dl or >25% above baseline within 72h after contrast administration. Serum creatinine concentration and GFR were 1.40+/-0.22, 1.29+/-0.29, and 1.26+/-0.29mg/dl and 52.2+/-13.9, 51.3+/-21.1, and 51.5+/-15.1ml/min on days 0, 3, and 7, respectively. Three out of 99 (3%) patients who received 90-110ml iodixanol revealed a CIN on day 3 without persistence on day 7. No specific therapy was needed. One out of 99 patients reported an exanthema on days 3 and 7. With the use of iodixanol in intermediate-risk patients, 3% of the patients develop CIN on day 3 without need for a specific therapy or persistence on day 7.

Use of iso-osmolar nonionic dimeric contrast media in multidetector row computed tomography angiography for patients with renal impairment

OBJECTIVES

We wanted to determine the rate of contrast-induced nephropathy (CIN) caused in patients with renal impairment undergoing multidetector row computed tomography (MDCT) angiography with intravenous administration of iso-osmolar dimeric contrast media (iodixanol).

MATERIALS AND METHODS

The first consecutive 100 patients referred to CT with a serum creatinine level (SCr) between 1.5 and 6 mg/dL were enrolled in the study. Serum creatinine also was determined on days 3 and 7 after the intravenous administration of 100 mL of iodixanol 270 with 5 mL/s. A CIN was considered if variation of SCr on day 3 was >0.5 mg/dl above baseline.

RESULTS

Nine patients developed a CIN after MDCT angiography; 7 of them recovered completely by day 7, and the remaining 2 showed elevated SCr on day 7 but did not develop renal failure during their hospital stay.

CONCLUSIONS

MDCT angiography performed in patients with impaired renal function with iodixanol may result in CIN but complete recovery is probable.

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.

Bench-to-bedside review: preventive measures for contrast-induced nephropathy in critically ill patients

An increasing number of diagnostic imaging procedures requires the use of intravenous radiographic contrast agents, which has led to a parallel increase in the incidence of contrast-induced nephropathy. Risk factors for development of contrast-induced nephropathy include pre-existing renal dysfunction (especially diabetic nephropathy and multiple myeloma-associated nephropathy), dehydration, congestive heart failure and use of concurrent nephrotoxic medication (including aminoglycosides and amphotericin B). Because contrast-induced nephropathy accounts for a significant increase in hospital-acquired renal failure, several strategies to prevent contrast-induced nephropathy are currently advocated, including use of alternative imaging techniques (for which contrast media are not needed), use of (the lowest possible amount of) iso-osmolar or low-osmolar contrast agents (instead of high-osmolar contrast agents), hyperhydration and forced diuresis. Administration of N-acetylcysteine, theophylline, or fenoldopam, sodium bicarbonate infusion, and periprocedural haemofiltration/haemodialysis have been investigated as preventive measures in recent years. This review addresses the literature on these newer strategies. Since only one (nonrandomized) study has been performed in intensive care unit patients, at present it is difficult to draw firm conclusions about preventive measures for contrast-induced nephropathy in the critically ill. Further studies are needed to determine the true role of these preventive measures in this group of patients who are at risk for contrast-induced nephropathy. Based on the available evidence, we advise administration of N-acetylcysteine, preferentially orally, or theophylline intravenously, next to hydration with bicarbonate solutions.