Removal of contrast media by different extracorporeal treatments

Contrast-Induced Encephalopathy: A Rare Complication in a Patient on Peritoneal Dialysis with Several Risk Factors

Major adverse renal and cardiovascular events are reported for high-risk patients undergoing intra-arterial procedures, even if performed with iso-osmolar contrast media (CM). We report a case of contrast-induced encephalopathy (CIE) in a peritoneal dialysis (PD) patient, affected by diabetes, hypertension, and chronic heart failure. A 78-year-old PD patient (diuresis 1,000 mL) underwent a percutaneous angioplasty of the carotid. Immediately after the exam, he developed mental confusion and aphasia. Encephalic computed tomography scan and magnetic resonance imaging excluded ischemia or hemorrhage, but both showed cerebral edema; EEG showed right hemisphere abnormalities, sequelae of recent ischemia. Mannitol and steroids were administered to reduce edema, and additional PD exchange was performed with depurative aim. Within 2 days the patient completely recovered. CIE mimics severe neurological diseases, and it should be considered as differential diagnosis if symptoms come out soon after intra-arterial administration of CM, especially in high-risk patients. Our patient suffered from diabetes, chronic kidney disease, hypertension, chronic heart failure, which are possible contributing factors to the development of CIE. Moreover, this clinical scenario is noteworthy because the development in a patient who underwent PD had never been described before.

Update on the renal toxicity of iodinated contrast drugs used in clinical medicine

An important side effect of diagnostic contrast drugs is contrast-induced acute kidney injury (CI-AKI; a sudden decrease in renal function) occurring 48-72 hours after injection of a contrast drug that cannot be attributed to other causes. Its existence has recently been challenged, because of some retrospective studies in which the incidence of AKI was not different between subjects who received a contrast drug and those who did not, even using propensity score matching to prevent selection bias. For some authors, only patients with estimated glomerular filtration rate <30 mL/min/1.73 m2 are at significant risk of CI-AKI. Most agree that when renal function is normal, there is no CI-AKI risk. Many experimental studies, however, are in favor of the existence of CI-AKI. Contrast drugs have been shown to cause the following changes: renal vasoconstriction, resulting in a rise in intrarenal resistance (decrease in renal blood flow and glomerular filtration rate and medullary hypoxia); epithelial vacuolization and dilatation and necrosis of proximal tubules; potentiation of angiotensin II effects, reducing nitric oxide (NO) and causing direct constriction of descending vasa recta, leading to formation of reactive oxygen species in isolated descending vasa recta of rats microperfused with a solution of iodixanol; increasing active sodium reabsorption in the thick ascending limbs of Henle's loop (increasing O2 demand and consequently medullary hypoxia); direct cytotoxic effects on endothelial and tubular epithelial cells (decrease in release of NO in vasa recta); and reducing cell survival, due to decreased activation of Akt and ERK1/2, kinases involved in cell survival/proliferation. Prevention is mainly based on extracellular volume expansion, statins, and N-acetylcysteine; conflicting results have been obtained with nebivolol, furosemide, calcium-channel blockers, theophylline, and hemodialysis.

The role of statins in the prevention of contrast induced nephropathy: a meta-analysis of 8 randomized trials

Contrast induced nephropathy (CIN) is a common complication of coronary angiography/angioplasty. Prevention is the key to reduce the incidence of CIN and it begins with appropriate pre-procedural management. Statins have been shown to possess pleiotropic effects (anti-oxidant, anti-inflammatory and anti-thrombotic properties) and their effects on CIN were assessed in several studies with conflicting results. Aim of this meta-analysis is to evaluate the efficacy of short-term statins for the prevention of CIN in patients undergoing coronary angiography/percutaneous interventions. We performed formal searches of PubMed, EMBASE, Cochrane central register of controlled trials and major international scientific session abstracts from January 1990 to January 2014 of trials which compares short-term statins versus Placebo for the prevention of CIN in patients undergoing coronary angiography/angioplasty. Data regarding study design, statin dose, inclusion/exclusion criteria, number of patients, and clinical outcome was extracted by 2 investigators. Eight trials were included, with a total of 4734 patients. CIN occurred in 79/2,358 patients (3.3%) treated with statins versus 153/2,376 patients (6.4%) of the placebo group [OR 95% CI 0.50 (0.38-0.66), p < 0.00001; p het = 0.39]. Benefits were both observed with high-dose short-term statins [OR 95% CI 0.44 (0.30-0.65), p < 0.0001; p het = 0.16] and low-dose statins, [OR 95% CI 0.58 (0.39-0.88), p = 0.010; p het = 0.90]. By meta-regression analysis, no significant relationship was observed between benefits from statin therapy and patient's risk profile (p = 0.26), LDL cholesterol (p = 0.4), contrast volume (p = 0.94) or diabetes rate (p = 0.38). This meta-analysis showed that among patients undergoing coronary angiography/percutaneous intervention the use of short-term statins reduces the incidence of CIN, and therefore is highly recommended even in patients with low LDL-cholesterol levels.

Prevention of contrast-induced nephropathy through a knowledge of its pathogenesis and risk factors

Contrast-induced nephropathy (CIN) is an iatrogenic acute renal failure (ARF) occurring after the intravascular injection of iodinated radiographic contrast media. During the past several years, in many patients undergoing computed tomography, iodinated contrast media have not been used for the fear of ARF, thereby compromising the diagnostic procedure. But recent studies have demonstrated that CIN is rarely occurring in patients with normal renal function and that preexisting chronic renal failure and/or diabetes mellitus represent(s) predisposing condition(s) for its occurrence. After the description of CIN and its epidemiology and pathophysiology, underlying the important role played by dehydration and salt depletion, precautions for prevention of CIN are listed, suggested, and discussed. Maximum priority has to be given to adequate hydration and volume expansion prior to radiographic procedures. Other important precautions include the need for monitoring renal function before, during, and after contrast media injection, discontinuation of potentially nephrotoxic drugs, use of either iodixanol or iopamidol at the lowest dosage possible, and administration of antioxidants. A long list of references is provided that will enable readers a deep evaluation of the topic.

The prevention of contrast-induced nephropathy by simultaneous hemofiltration during coronary angiographic procedures: a comparison with periprocedural hemofiltration

BACKGROUND

Periprocedural (6 h pre- and 24 h post-angiography) hemofiltration appears to effectively prevent contrast-induced nephropathy (CIN) in chronic kidney disease (CKD) patients undergoing coronary angiography. However, this procedure over-uses medical resources, and the cessation of hemofiltration during coronary angiography results in persistent renal injury. In comparison, simultaneous hemofiltration performed only during coronary angiography requires fewer medical resources and can provide instantaneous protection against CIN.

METHODS

Sixty-eight CKD patients (serum creatinine, 2.51±1.15 mg/dL) undergoing coronary angiography were randomized in a 1:2 ratio to receive either periprocedural (n=23) or simultaneous (n=45) hemofiltration. The expected CIN rate was similar for the two groups (41.3% versus 40.0%, p=0.769).

RESULTS

On day 3 after contrast exposure, four and seven patients in the periprocedural and simultaneous groups, respectively experienced CIN (17.4% versus 15.6%, p=0.846). On days 5-30, seven and three patients in the periprocedural and simultaneous groups, respectively experienced CIN (30.4% versus 6.7%, p=0.009). The serum creatinine levels of patients in the periprocedural group transiently decreased on day 1 and persistently increased during days 5-30 compared with the simultaneous group. This difference between the two groups in terms of creatinine levels over time was statistically significant (F statistic=6.830; p=0.001, by ANCOVA). The cost of hemofiltration was doubled in the periprocedural group ($1066±83 versus $504±40, p<0.001).

CONCLUSIONS

Simultaneous hemofiltration provide equal early (day 3) and better late-stage (days 5-30) renal protection against CIN at a significantly lower cost compared with periprocedural hemofiltration.

Acute kidney injury by radiographic contrast media: pathogenesis and prevention

It is well known that iodinated radiographic contrast media may cause kidney dysfunction, particularly in patients with preexisting renal impairment associated with diabetes. This dysfunction, when severe, will cause acute renal failure (ARF). We may define contrast-induced Acute Kidney Injury (AKI) as ARF occurring within 24-72 hrs after the intravascular injection of iodinated radiographic contrast media that cannot be attributed to other causes. The mechanisms underlying contrast media nephrotoxicity have not been fully elucidated and may be due to several factors, including renal ischaemia, particularly in the renal medulla, the formation of reactive oxygen species (ROS), reduction of nitric oxide (NO) production, and tubular epithelial and vascular endothelial injury. However, contrast-induced AKI can be prevented, but in order to do so, we need to know the risk factors. We have reviewed the risk factors for contrast-induced AKI and measures for its prevention, providing a long list of references enabling readers to deeply evaluate them both.

The use of iodinated contrast media in patients with end-stage renal disease

Iodinated contrast agents are well tolerated in ESRD patients. Certain types of ICM, i.e., LOCM and the nonionic agents are associated with better safety profiles. Current available evidence, although not optimal, does not support the need for additional hemodialysis for ICM removal to preserve residual renal function or to treat other potential toxicities of ICM. However, limiting exposure to ICM is a prudent measure in ESRD patients given ICM’s potential toxicity; close monitoring of patients with poor cardiac function is also recommended in subjects receiving higher doses of ICM, especially those receiving HOCM.

Contrast-induced Nephropathy

Contrast-induced nephropathy (CIN) is a serious complication of angiographic procedures resulting from the administration of contrast media (CM). It is the third most common cause of hospital acquired acute renal injury and represents about 12% of the cases. CIN is defined as an elevation of serum creatinine (Scr) of more than 25% or ≥0.5 mg/dl (44 μmol/l) from baseline within 48 h. More sensitive markers of renal injury are desired, therefore, several biomarkers of tubular injury are under evaluation. Multiple risk factors may contribute to the development of CIN; these factors are divided into patient- and procedure-related factors. Treatment of CIN is mainly supportive, consisting mainly of careful fluid and electrolyte management, although dialysis may be required in some cases. The available treatment option makes prevention the corner stone of management. This article will review the recent evidence concerning CIN incidence, diagnosis, and prevention strategies as well as its treatment and prognostic implications.

Side effects of radiographic contrast media: pathogenesis, risk factors, and prevention

Radiocontrast media (RCM) are medical drugs used to improve the visibility of internal organs and structures in X-ray based imaging techniques. They may have side effects ranging from itching to a life-threatening emergency, known as contrast-induced nephropathy (CIN). We define CIN as acute renal failure occurring within 24-72 hrs of exposure to RCM that cannot be attributed to other causes. It usually occurs in patients with preexisting renal impairment and diabetes. The mechanisms underlying CIN include reduction in medullary blood flow leading to hypoxia and direct tubule cell damage and the formation of reactive oxygen species. Identification of patients at high risk for CIN is important. We have reviewed the risk factors and procedures for prevention, providing a long list of references enabling readers a deep evaluation of them both. The first rule to follow in patients at risk of CIN undergoing radiographic procedure is monitoring renal function by measuring serum creatinine and calculating the eGFR before and once daily for 5 days after the procedure. It is advised to discontinue potentially nephrotoxic medications, to choose radiocontrast media at lowest dosage, and to encourage oral or intravenous hydration. In high-risk patients N-acetylcysteine may also be given.

Elevation of urinary liver-type fatty acid-binding protein as predicting factor for occurrence of contrast-induced acute kidney injury and its reduction by hemodiafiltration with blood suction from right atrium

Although contrast-induced acute kidney injury (CI-AKI) has a great impact on patients' prognosis, few data exist regarding predictors of CI-AKI in patients with severe renal dysfunction who have undergone contrast angiography. Therefore, we prospectively studied 25 patients with renal dysfunction, which was defined as the estimated glomerular filtration rate (eGFR) level <45 ml/min/1.73 m(2), undergoing coronary angiography (CAG) or percutaneous coronary intervention (PCI). We performed hemodiafiltration with blood suction from the right atrium (RA-HDF). The mean level of urinary liver-type fatty acid-binding protein (L-FABP) at baseline was significantly higher in the CI-AKI group than in the non-CI-AKI group (59.8 ± 45.6 vs 13.4 ± 11.9 μg/gCr, P = 0.0003). Multivariate regression analysis demonstrated that baseline urinary L-FABP was an independent significant predictor of CI-AKI (β = 0.741, P = 0.013). Receiver-operating characteristic analysis showed that baseline urinary L-FABP exhibited 100 % sensitivity and 81.8 % specificity for predicting CI-AKI when the cutoff value was defined as 19.0 μg/gCr. Interestingly, the incidence of CI-AKI after CAG or PCI was reduced in the RA-HDF group in a comparison with 41 control patients (12 % vs 27 %) with eGFR level <45 ml/min/1.73 m(2) who underwent PCI before the introduction of RA-HDF. In conclusion, baseline L-FABP levels can be a predictor for occurrence of CI-AKI. We suggest that RA-HDF may prevent the development of CI-AKI in patients with severe renal dysfunction undergoing coronary procedures, although further large-scale prospective study is necessary to confirm our conclusions.

Iodinated contrast media and the role of renal replacement therapy

Iodinated contrast media are among the most commonly used pharmacologic agents in medicine. Although generally highly safe, iodinated contrast media are associated with several adverse effects, most significantly the risk of acute kidney injury, particularly in patients with underlying renal dysfunction. By virtue of their pharmacokinetic characteristics, these contrast agents are efficiently cleared by hemodialysis and to a lesser extent, hemofiltration. This has led to research into the capacity for renal replacement therapies to prevent certain adverse effects of iodinated contrast. This review examines the molecular and pharmacokinetic characteristics of iodinated contrast media and critically analyzes data from past studies on the role of renal replacement therapy to prevent adverse effects of these diagnostic agents.

Contrast-induced acute kidney injury and diabetic nephropathy

Contrast-induced acute kidney injury (CIAKI) is a leading cause of iatrogenic renal failure. Multiple studies have shown that patients with diabetic nephropathy are at high risk of CIAKI. This Review presents an overview of the pathogenesis of CIAKI in patients with diabetic nephropathy and discusses the currently available and potential future strategies for CIAKI prevention.

Prevention of acute kidney injury and protection of renal function in the intensive care unit. Expert opinion of the Working Group for Nephrology, ESICM

BACKGROUND

Acute renal failure on the intensive care unit is associated with significant mortality and morbidity.

OBJECTIVES

To determine recommendations for the prevention of acute kidney injury (AKI), focusing on the role of potential preventative maneuvers including volume expansion, diuretics, use of inotropes, vasopressors/vasodilators, hormonal interventions, nutrition, and extracorporeal techniques.

METHOD

A systematic search of the literature was performed for studies using these potential protective agents in adult patients at risk for acute renal failure/kidney injury between 1966 and 2009. The following clinical conditions were considered: major surgery, critical illness, sepsis, shock, and use of potentially nephrotoxic drugs and radiocontrast media. Where possible the following endpoints were extracted: creatinine clearance, glomerular filtration rate, increase in serum creatinine, urine output, and markers of tubular injury. Clinical endpoints included the need for renal replacement therapy, length of stay, and mortality. Studies are graded according to the international Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) group system.

CONCLUSIONS AND RECOMMENDATIONS

Several measures are recommended, though none carries grade 1A. We recommend prompt resuscitation of the circulation with special attention to providing adequate hydration whilst avoiding high-molecular-weight hydroxy-ethyl starch (HES) preparations, maintaining adequate blood pressure using vasopressors in vasodilatory shock. We suggest specific vasodilators [corrected] under strict hemodynamic control, sodium bicarbonate for emergency procedures administering contrast media, and periprocedural hemofiltration in severe chronic renal insufficiency undergoing coronary intervention.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s00134-009-1678-y) contains supplementary material, which is available to authorized users.

Contrast-induced nephropathy: pathogenesis and prevention

Contrast-induced nephropathy (CIN) is the third most common cause of acute kidney injury in hospitalized patients. Diagnostic and interventional cardiovascular procedures generate nearly half the cases. Elderly patients and those with chronic kidney disease, diabetes, and cardiovascular disease are at greatest risk. Procedure-related risk factors include large volumes of contrast and agents with a high osmolality. Renal medullary ischemia arising from an imbalance of local vasoconstrictive and vasodilatory influences coupled with increased demand for oxygen-driven sodium transport may be the key to its pathogenesis. Contrast agents may also have a direct cytotoxic effect that operates through the generation of reactive oxygen species. Pre- and post-procedure administration of normal saline, isotonic sodium bicarbonate, N-acetylcysteine, and a variety of other pharmacologic agents have been used to prevent or mitigate CIN. While normal saline is generally accepted as protective against CIN, uncertainty still surrounds the role of sodium bicarbonate and N-acetylcysteine. Dialytic therapies before, during, and after exposure to contrast have been tested with mixed results. Logistical and economic disincentives argue against these modalities.

The role of extracorporeal blood purification therapies in the prevention of radiocontrast-induced nephropathy

Radiocontrast-induced nephropathy (RCIN) is a common and potentially serious complication following diagnostic and therapeutic cardiology procedures using radiocontrast media. The first and most important step in reducing the likelihood of RCIN is to identify patients at risk, by medical history and measurement of serum creatinine concentration to allow calculation of estimated glomerular filtration rate (GFR). Extracorporeal blood purification effectively removes radiocontrast media from the circulation. Periprocedural extracorporeal blood purification (hemodialysis or continuous renal replacement therapy) does not reduce the incidence of RCIN compared with standard medical therapy, and cannot be recommended at this time. The potential benefit of continuous venovenous hemofiltration published by a single center should be confirmed with further studies before it can be recommended or disregarded, and higher doses of continuous renal replacement therapy may also merit further investigation.

The role of dialysis in contrast-induced nephropathy: doubts and certainties

Over past years, there has been a progressive increase in percutaneous endovascular procedures in patients with chronic renal disease, owing to the high incidence of vascular disease, particularly coronary artery disease, in this population. The use of contrast media may further worsen renal function in such patients, in some cases even accelerating the progression towards end-stage renal failure, and may increase patient morbidity and mortality. In this review, we discuss the role of dialysis in preventing contrast-induced nephropathy as well as present indications to its use in patients already on dialysis treatment undergoing diagnostic or therapeutic procedures with contrast medium injection.

Strategies to reduce the risk of contrast-induced nephropathy

In view of the clinical importance of contrast-induced nephropathy (CIN), numerous potential risk-reduction strategies have been evaluated. Adequate intravenous volume expansion with isotonic crystalloid (1.0-1.5 mL/kg per hr) for 3-12 hours before the procedure and continued for 6-24 hours afterward can lessen the probability of CIN in patients at risk. There are insufficient data on oral fluids (as opposed to intravenous volume expansion) as a CIN-prevention strategy. No adjunctive medical or mechanical treatment has been proved to be efficacious in reducing risk for CIN. Prophylactic hemodialysis and hemofiltration have not been validated as effective strategies. The CIN Consensus Working Panel considered that, of the pharmacologic agents that have been evaluated, theophylline, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), ascorbic acid, and prostaglandin E(1) deserve further evaluation. N-acetylcysteine is not consistently effective in reducing the risk for CIN. Fenoldopam, dopamine, calcium channel blockers, atrial natriuretic peptide, and l-arginine have not been shown to be effective. Use of furosemide, mannitol, or an endothelin receptor antagonist is potentially detrimental. Nephrotoxic drugs should be withdrawn before contrast administration in patients at risk for CIN.

Extracorporeal blood purification therapies for prevention of radiocontrast-induced nephropathy: a systematic review

BACKGROUND

Radiocontrast-induced nephropathy (RCIN) causes acute kidney injury and increases mortality. Studies have examined the capacity of various forms of extracorporeal blood purification therapies for the prevention of RCIN, with conflicting results. We conducted a systematic review of published trials to determine whether periprocedural extracorporeal blood purification prevents RCIN.

METHODS

We searched PubMed, the Cochrane Collaboration Database, EMBASE, and CINAHL through January 2006 and bibliographies of retrieved articles and consulted with experts to identify relevant studies. Published studies of extracorporeal blood purification for the prevention of RCIN in patients receiving radiocontrast were included. Two authors reviewed all citations. The primary end point is the incidence of RCIN, defined as an increase in serum creatinine concentration (>or=0.5 mg/dL [>or=44 micromol/L]). Results were combined on the risk ratio scale. Random-effects models were used. Sensitivity analyses were performed to evaluate the effects of extracorporeal blood purification modality, study design, and sample size.

RESULTS

Eight trials (6 randomized controlled trials, 2 nonrandomized trials) were included in the analysis (pooled sample size, 412). Six trials assessed hemodialysis, whereas 1 trial each assessed continuous venovenous hemofiltration and continuous venovenous hemodiafiltration. The incidence of RCIN was 35.2% in the standard-medical-therapy group and 27.8% in the extracorporeal-blood-purification group. Extracorporeal blood purification did not decrease the incidence of RCIN significantly compared with standard medical therapy (risk ratio, 0.97; 95% confidence interval, 0.44 to 2.14); however, intertrial heterogeneity was high. Limiting analysis to only randomized trials did not eliminate heterogeneity, but limiting analysis to only hemodialysis trials did. Periprocedural hemodialysis did not decrease the incidence of RCIN.

CONCLUSION

This critical analysis of the published literature suggests that periprocedural extracorporeal blood purification does not decrease the incidence of RCIN compared with standard medical therapy.

Dialysis and iodinated contrast media

Contrast media are excreted mainly by glomerular filtration. There is thus, a significant correlation between both body and renal clearances of contrast media and glomerular filtration rate, and their renal excretion will be delayed in patients with renal insufficiency. Contrast media can be efficiently removed from blood by hemodialysis (HD). Since most contrast media are middle-sized molecules, the main factors potentially influencing their removal by HD are blood flow, membrane surface area, molecular size, transmembrane pressure, and dialysis time. Peritoneal dialysis is also effective in removing contrast agents from the body but takes longer than HD. Dialysis immediately after radiographic contrast studies has been suggested for two groups of patients. Those on chronic HD and those at very high risk for contrast nephropathy. Three studies have examined the necessity of immediate dialysis after intravascular injection of contrast media in chronic HD patients; the authors found no evidence that it is effective at preventing contrast nephropathy. The reasons why HD treatment was not beneficial in those three studies are not known. Perhaps, the rapid onset of renal injury after administration of contrast media is one answer. It is also possible that HD per se was nephrotoxic and might have offset the beneficial effect of the removal of contrast media. Marenzi et al. randomized 114 consecutive patients with chronic renal failure undergoing coronary interventions to either hemofiltration in an intensive care unit or isotonic saline hydration. The authors concluded that periprocedural hemofiltration given in an intensive care unit setting appears to be effective in preventing the deterioration of renal function due to contrast agent induced nephropathy and is associated with improved in-hospital and long term outcomes. The concentration of contrast media can effectively be reduced by HD and peritoneal dialysis. HD does not offer any protection against contrast media induced nephrotoxicity. Hemofiltration may decrease the risk of contrast induced nephropathy and have some long-term benefits, but additional studies are needed to better define the appropriate population for this treatment.

Prophylactic hemodialysis does not prevent contrast-induced nephropathy after cardiac catheterization in patients with chronic renal insufficiency

BACKGROUND

In Japan, prophylactic hemodialysis has been considered useful for preventing contrast-induced nephropathy (CIN).

METHOD AND RESULTS

To assess whether hemodialysis prevented CIN, 391 patients (age: 69 +/- 8 years, 63 females) with chronic renal insufficiency (CRI, serum creatinine level (Scr) > or = 1.3 mg/dl) who underwent cardiac catheterization, were retrospectively analyzed. Patients were divided into 3 categories based on Scr: L (1.3 > or = Scr < 2.0 mg/dl, n = 332); M (2.0 > or = Scr < 3.0 mg/dl, n = 49); and H (Scr > or = 3.0 mg/dl, n = 10). To prevent CIN, 35 category M patients and all category L patients received hydration alone, whereas 14 category M patients and all category H patients received hemodialysis. CIN developed in 48 patients. The incidence of CIN in category H was significantly higher than that in category L or M (H, 40% vs L, 11% or M, 16% (p < 0.05)). In category M patients treated with hemodialysis, Scr increased from 2.4 +/- 0.3 to 3.0 +/- 0.5 mg/dl (p < 0.05) within 7 days, and 29% of patients developed CIN. However, in category M patients who did not receive hemodialysis, the Scr did not change (pre, 2.3 +/- 0.2 mg/dl to post, 2.2 +/- 0.4 mg/dl), and the incidence of CIN was 11%.

CONCLUSION

Prophylactic hemodialysis for CRI patients undergoing cardiac catheterization does not prevent CIN.

Is radiocontrast-induced nephropathy avoidable? The scientific evidence in 2006

Due to the wide use of radiocontrast agents (RCA) in modern radiology and interventional cardiology, the incidence of radiocontrast-induced nephropathy (RCIN) is increasing. The risk factors for RCIN are primarily pre-existing (even mild) renal dysfunction, diabetes mellitus, absolute or relative hypovolemia, nephrotoxic drugs, etc., particularly in elderly patients. The presence of these risk factors seems to be more important than the type of contrast agent used. To date, there are several certainties and controversies in the prevention of RCIN. Hydration with normal saline and/or bicarbonate administration pre-and post-intervention is certainly useful. Though controversial, N-Acetylcysteine administration may be still advisable. Recent investigations showed the benefits of aminophylline/theophylline administration in RCA-induced renal tubular toxicity. Conventional hemodialysis cannot prevent RCIN, but may potentially aggravate renal dysfunction through hemodynamic instability. “High-flux” hemodialysis and hemodiafiltration may contribute efficiently to RCIN prevention, but systematic use of these modern dialysis techniques is limited by high costs and availability. The authors review — in a systematic manner, and in the perspective of evidence-based medicine — the most important data from literature concerning the prevention of RCIN.

Comparison of two hemofiltration protocols for prevention of contrast-induced nephropathy in high-risk patients

PURPOSE

Contrast-induced nephropathy is a complication of contrast medium administration during diagnostic and interventional procedures, with important prognostic relevance. Patients with chronic kidney disease have a higher risk for contrast-induced nephropathy and poorer outcome. In patients with chronic kidney disease, hemofiltration reduces contrast-induced nephropathy incidence and improves long-term survival. We assessed the mechanisms involved in the prophylactic effect of hemofiltration and of the most effective hemofiltration protocol to prevent contrast-induced nephropathy in patients with chronic kidney disease.

SUBJECTS AND METHODS

We randomized 92 patients with chronic kidney disease (creatinine clearance < or =30 mL/min) to three different prophylactic treatments: intravenous hydration with isotonic saline (1 mL x kg x h for 12 hours before and after contrast exposure, control group; n = 30); intravenous hydration for 12 hours before contrast exposure, followed by hemofiltration for 18 to 24 hours after contrast exposure (post-hemofiltration group; n = 31), and hemofiltration performed for 6 hours before and for 18 to 24 hours after contrast exposure (pre/post-hemofiltration group; n = 31). The incidence of contrast-induced nephropathy (>25% increase in creatinine) and the in-hospital clinical course were compared in the three groups.

RESULTS

Twelve patients (40%) in the control group, 8 patients (26%) in the post-hemofiltration group, and 1 patient (3%) in the pre/post-hemofiltration group experienced contrast-induced nephropathy (P = .0013); hemodialysis was required in 9 (30%), three (10%), and zero (0%) patients, respectively (P = .002). In-hospital mortality was 20%, 10%, and 0%, respectively (P = .03).

CONCLUSIONS

Hemofiltration is an effective strategy for contrast-induced nephropathy prevention in patients with chronic kidney disease who are undergoing cardiovascular procedures. Pre-hemofiltration is required to obtain the full clinical benefit, suggesting that, among different mechanisms possibly involved, high-volume controlled hydration before contrast media exposure plays a major role.

Contrast-induced nephropathy

Contrast-induced nephropathy (CIN) is a leading cause of in-hospital acute renal failure in critically ill patients who undergo radiographic procedures. Critical care patients are at particular risk, often because of baseline renal dysfunction, older age, and the presence of diabetes. In addition, there are superimposed risks, including volume depletion, sepsis, and use of nephrotoxic drugs. The rates of CIN (defined as an increase in serum creatinine by >25% or 0.5 mg/dL) can be predicted by using multivariate tools. Prevention measures include adequate hydration, use of N-acetylcysteine and iso-osmolar contrast, and for patients who are at the highest risk, prophylactic hemofiltration.

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.

Recent advances in the prevention of radiocontrast-induced nephropathy

PURPOSE OF REVIEW

Radiocontrast nephropathy is a serious clinical problem associated with increased morbidity and mortality, particularly in patients with chronic renal failure. The optimal strategy to prevent radiocontrast nephropathy has not been established. This article reviews recent clinical researches concerning new developments in the prevention of radiocontrast nephropathy and analyzes unresolved issues.

RECENT FINDINGS

Among all prophylactic measures that have been proposed, periprocedural hydration with isotonic saline has demonstrated effectiveness in the prevention of radiocontrast nephropathy. Thus, it remains the most frequently applied measure in clinical practice. Recently, additional benefit has been shown to derive from the infusion of isotonic alkalizing (sodium bicarbonate), instead of isotonic (sodium chloride) solutions. The use of nonionic low-osmolar and, more recently, nonionic iso-osmolar contrast agents has been demonstrated to significantly reduce the risk of radiocontrast nephropathy in patients with renal impairment, in comparison with hyperosmolar contrast media. Recently, periprocedural hemofiltration has emerged as a safe and very effective strategy to prevent radiocontrast nephropathy and to reduce its associated poor outcome in patients with severe chronic renal failure. In the past few years, several trials with acetylcysteine have shown conflicting results. Nevertheless, most of them indicated that acetylcysteine, particularly when associated with adequate hydration, might be useful in preventing radiocontrast nephropathy in patients with renal impairment. A possible dose-dependent protective effect has been suggested by more recent trials that included patients undergoing coronary interventional procedures requiring large contrast volume.

SUMMARY

Adequate prophylaxis is needed to reduce the high morbidity and mortality associated with radiocontrast nephropathy in high-risk patients. By reviewing the available evidence from clinical trials, this article provides an overview of current strategies and unresolved issues concerning the prevention of radiocontrast nephropathy.

Prediction of iopromide reduction rates during haemodialysis using an in vitro dialysis system

BACKGROUND

In clinical studies, it has been difficult to evaluate the influence of haemodialysis (HD) parameters on HD clearance (CL(HD)) and reduction rate (RR) of non-ionic contrast medium during HD sessions. We therefore predicted clinical values of CL(HD) and RR of iopromide, a non-ionic contrast medium, from findings obtained from in vitro experiments, and confirmed that these predictive values were comparable with the actual values in clinical cases.

METHODS

We developed a correlation equation for predicting CL(HD) on the basis of in vitro HD experiments by varying blood flow rates between 100 and 200 ml/min with a cuprammonium rayon dialyser (AM-SD-10H). Total body clearance of iopromide (CL(PT)) was estimated by the Cockroft-Gault equation. The volume of distribution (V(d)) was obtained from the reported value. By using the HD and three pharmacokinetic parameters (CL(HD), CL(PT) and V(d)), we predicted CL(HD) and RR for seven patients undergoing HD after the administration of iopromide.

RESULTS

In the in vitro study, the mean values (+/-SD) of iopromide clearance at blood flow rates of 100, 150 and 200 ml/min were 45.35 (2.54), 53.88 (6.46) and 57.61 (4.72) ml/min, respectively. There were highly significant correlations between clearance and blood flow rate (r = 0.975). Although the predicted CL(HD) showed a tendency towards underestimation, a good correlation was found. Predicted RR values were similar to observed values except for one case.

CONCLUSION

The in vitro model used in the present study provides pertinent information about CL(HD) and is helpful for predicting RR during HD in individual patients undergoing HD.

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.

Acute toxic renal failure

Acute renal failure (ARF) is a common problem in intensive care medicine. Even modest degrees of ARF not requiring dialysis treatment increase the risk of death approximately fivefold. Despite the widespread appreciation of the role of nephrotoxic drugs in their contribution to ARF, these drugs continue to have an ongoing aetiological role. Potentially nephrotoxic drugs include non-steroidal anti-inflammatory drugs, radiocontrast agents, antimicrobial and anaesthetic agents. Endogenous compounds such as myoglobin and haemoglobin may furthermore cause toxic nephropathy. Tubular injury initiated by toxins often results from a combination of acute renal vasoconstriction and direct cellular toxicity due to intracellular accumulation of the toxin, or, alternatively, may be mediated immunologically in case of interstitial nephritis. Patients with reduced renal functional reserve, cardiovascular co-morbidity, diabetes mellitus, and advanced age are at increased risk. Awareness of the range of toxins on the one hand and simple measures such as adequate pre-hydration of the patient and drug monitoring on the other hand may be sufficient to avoid drug-induced ARF or minimize its clinical severity in susceptible patients.

The prevention of radiocontrast-agent-induced nephropathy by hemofiltration

BACKGROUND

Nephropathy induced by exposure to radiocontrast agents, a possible complication of percutaneous coronary interventions, is associated with significant in-hospital and long-term morbidity and mortality. Patients with preexisting renal failure are at particularly high risk. We investigated the role of hemofiltration, as compared with isotonic-saline hydration, in preventing contrast-agent-induced nephropathy in patients with renal failure.

METHODS

We studied 114 consecutive patients with chronic renal failure (serum creatinine concentration, >2 mg per deciliter [176.8 micromol per liter]) who were undergoing coronary interventions. We randomly assigned them to either hemofiltration in an intensive care unit (ICU) (58 patients, with a mean [+/-SD] serum creatinine concentration of 3.0+/-1.0 mg per deciliter [265.2+/-88.4 micromol per liter]) or isotonic-saline hydration at a rate of 1 ml per kilogram of body weight per hour given in a step-down unit (56 patients, with a mean serum creatinine concentration of 3.1+/-1.0 mg per deciliter [274.0+/-88.4 micromol per liter]). Hemofiltration (fluid replacement rate, 1000 ml per hour without weight loss) and saline hydration were initiated 4 to 8 hours before the coronary intervention and were continued for 18 to 24 hours after the procedure was completed.

RESULTS

An increase in the serum creatinine concentration of more than 25 percent from the base-line value after the coronary intervention occurred less frequently among the patients in the hemofiltration group than among the control patients (5 percent vs. 50 percent, P<0.001). Temporary renal-replacement therapy (hemodialysis or hemofiltration) was required in 25 percent of the control patients and in 3 percent of the patients in the hemofiltration group. The rate of in-hospital events was 9 percent in the hemofiltration group and 52 percent in the control group (P<0.001). In-hospital mortality was 2 percent in the hemofiltration group and 14 percent in the control group (P=0.02), and the cumulative one-year mortality was 10 percent and 30 percent, respectively (P=0.01).

CONCLUSIONS

In patients with chronic renal failure who are undergoing percutaneous coronary interventions, periprocedural hemofiltration given in an ICU setting appears to be effective in preventing the deterioration of renal function due to contrast-agent-induced nephropathy and is associated with improved in-hospital and long-term outcomes.

Contrast nephropathy

Contrast nephropathy will increase mortality up to 30% following angiographic procedures. Before performing such procedures a careful reassessment of the risk/benefit ratio should be performed. Mannitol and diuretics play no role in prevention. Hydration and correction of abnormal electrolyte levels should be done in all patients. Pre-treatment with acetylcysteine and theophylline is a well-accepted strategy and should always be utilized. If creatinine levels are above 2.5 to 3 mg/dl, fenoldopam may provide additional protection, particularly in diabetic patients. However, the role of fenoldopam is controversial. Prophylactic hemodialysis may prove to be an additional tool in the fight against this disease in selected patients.

Effect of the surface potential of the hemodialysis membrane and the electrical charge of the gadolinium contrast medium on dialyzability

PURPOSE

To search for methods of improving the excretion of injected gadolinium contrast medium (GdCM) in hemodialysis (HD) patients, we investigated the effect of the surface potential of HD membranes and the electrical charge of GdCM on the dialyzability of GdCM.

MATERIALS AND METHODS

Ionic (Gd-DTPA) or non-ionic (Gd-DO3A) GdCM solutions were dialyzed using a clinical HD unit. Two types of HD membranes, AN69 with a surface potential and PMMA without, were used. GdCM clearance was then calculated.

RESULTS

Gd-DTPA clearance was significantly higher for PMMA membranes than for AN69 membranes. Gd-DO3A clearance was slightly higher for AN69 membranes than for PMMA membranes. The difference in Gd-DTPA and Gd-DO3A clearance values was not significant when PMMA membranes were used.

CONCLUSION

These data indicate that non-ionic GdCM is preferable to ionic GdCM in patients receiving dialysis through an electrically positive membrane. Either ionic or non-ionic GdCM can be used when a normal dialysis membrane is being used.

Continuous veno-venous hemofiltration for the treatment of contrast-induced acute renal failure after percutaneous coronary interventions

Acute renal failure (ARF) requiring hemodialysis after percutaneous coronary interventions (PCI) is a serious complication with poor prognosis. Hemodialysis-induced hypotension may have deleterious cardiovascular effects, especially in high-risk patients. Ultrafiltrate removal and simultaneous fluid replacement with a solution similar to plasma for high-volume controlled hydration can be obtained with hemodynamic stability by continuous veno-venous hemofiltration (CVVH). We prospectively assessed the safety and effectiveness of percutaneous CVVH (Y-shaped double-lumen catheter, circuit originating from and terminating in the femoral vein) in 33 consecutive patients (23 men and 10 women; mean age, 69 +/- 9 years) who, after PCI, developed oligo-anuric ARF, associated in 20 of them with congestive heart failure. All patients received a concomitant infusion of furosemide (500-1000 mg/day) and dopamine (2 microg/kg/min). During CVVH, the average fluid volume replacement and body fluid net reduction were 1000 +/- 247 and 75 +/- 48 ml/hr, respectively. Treatment with CVVH continued for 4.7 +/- 2.7 days and corrected fluid overload in all cases. No patient experienced systemic hypotension or hypovolemia. Diuresis recovered in 32 (97%) patients, who showed a parallel improvement of renal function parameters. One patient required chronic dialysis. In-hospital and 1-year mortality was 9.1% and 27.3%, respectively. In conclusion, our data indicate that CVVH is a safe and effective therapy of radiocontrast-induced ARF following PCI. It temporarily replaces renal function without deleterious cardiovascular effects, allowing the kidney to recover from the nephrotoxic injury. However, despite promising early results, large randomized trials are required to define the role of CVVH in ARF after PCI.