Role of adenosine in contrast media-induced acute renal failure in diabetes mellitus

Prevention of post-contrast kidney injury in patients with cancer

Post-contrast acute kidney injury is defined as a nephropathy with an increase in serum creatinine of >0.3 mg/dL (or >26.5 μmol/L) or >1.5-times the baseline within 48-72 h of intravascular administration of a contrast medium. Patients with cancer have an increased risk of post-contrast acute kidney injury not only related to the frequent use of contrast medium for computed tomography scans but also to other factors, including the type of tumour, age, oncological therapies, use of other nephrotoxic agents and dehydration. Preventive strategies were developed and may be applied to different risk profiles. Patients at risk may be detected by recently published risk scores.

Probucol Protects Against Contrast-Induced Acute Kidney Injury via the Extracellular Signal-Regulated Kinases 1 and 2 (ERK1/2)/JNK-Caspase 3 Pathway in Diabetic Rats

Background

Contrast-induced acute kidney injury is an important clinical problem, yet its pathogenic mechanisms are incompletely understood. In this study we explored the potential beneficial effects of probucol as treatment of contrast-induced acute kidney injury in diabetic rats.

Material/Methods

Rats were divided into 3 groups: i) diabetic control, ii) diabetic with contrast, and iii) probucol treatment groups. Probucol was administered by gavage and the contrast diatrizoate (60%) was injected via femoral vein. After 24 h, the rats were sacrificed and samples were taken to measure biochemical indicators. Pathological damage of renal tubules was evaluated by HE staining. Expression of Bcl-2, Bax, p-ERKs, and p-JNK proteins in the kidneys was examined by Western blotting, whereas expression level of caspase-3 in kidneys was detected by immunohistochemistry.

Results

Compared to the probucol treatment group, the diabetes with contrast group showed higher serum creatinine and lower creatinine clearance. The pathological changes of kidneys in the probucol treatment group were improved compared with the contrast group. Moreover, Western blot analyses revealed that use of contrast agent led to lower p-ERK1/2, higher p-JNK, lower Bcl-2, and higher Bax levels, which were reversed by probucol. Finally, immunohistochemical findings revealed higher caspase-3 after contrast use, which was partially reversed by probucol.

Conclusions

Probucol exerts protective effects on contrast-induced acute kidney injury in diabetic rats by inhibition of renal cell apoptosis. This is achieved by reducing mitochondrial caspase-3 expression through increasing and decreasing the expression of the upstream mediators p-ERK1/2 and p-JNK, respectively.

Contrast-Induced Acute Kidney Injury: Pathophysiology, Manifestations, Prevention, and Management

Contrast-induced acute kidney injury is a phenomenon that has been extensively studied throughout the years. There is a large volume of literature documenting this risk, and most radiology departments and radiologists use this information when making decisions regarding contrast administration. A review of the current information on the topic of contrast-induced acute kidney injury is necessary to ensure that the risks of intravenous contrast are properly weighed against the benefits of a contrast-enhanced computed tomography scan.

Issues related to renal artery angioplasty and stenting

Renal artery stenosis may play a significant role in the pathogenesis of secondary hypertension, renal dysfunction, and flash pulmonary edema. Currently correction of renal arterial inflow stenosis is reserved for resistant hypertension patients who have failed maximal medical therapy, have worsening renal function and/or unexplained proximal congestive failure. With the recent advances in minimally invasive percutaneous stent placement techniques, open surgical revascularization has been largely replaced by renal artery stenting. The potential benefit of revascularization seemed intuitive; however, the initial enthusiasm and rise in the number of percutaneous interventions have been tempered by many subsequent negative randomized clinical trials that failed to prove the proposed benefits of the percutaneous intervention. The negative randomized trial results have fallen under scrutiny due to trial design concerns and inconsistent outcomes of these studies compared to pivotal trials undertaken under US Food and Drug Administration scrutiny. Treatment of atherosclerotic renal artery occlusive disease has become one of the most debatable topics in the field of vascular disease. The results from recent randomized clinical trials of renal artery stenting have basically limited the utilization of the procedure in many centers, but not every clinical scenario was covered in those trials. There are potential areas for improvement focusing mainly on procedural details and patient selection with respect to catheter based treatment of atherosclerotic renal artery stenosis. We believe, limiting patient selection, enrollment criteria and outcomes measured functioned to reduce the benefit of renal artery stenosis stenting by not enrolling patients likely to benefit. Future studies incorporating potential procedural improvements and that include patients more likely to benefit from renal stenting than were included in ASTRAL and CORAL are needed to more carefully examine specific patient subgroups so that “the baby is not thrown out with the bath water.” We also discuss several other concerns related to renal artery stenting which include diagnostic, procedure, indication, and reimbursement issues.

Issues related to renal artery angioplasty and stenting

Renal artery stenosis may play a significant role in the pathogenesis of secondary hypertension, renal dysfunction, and flash pulmonary edema. Currently correction of renal arterial inflow stenosis is reserved for resistant hypertension patients who have failed maximal medical therapy, have worsening renal function and/or unexplained proximal congestive failure. With the recent advances in minimally invasive percutaneous stent placement techniques, open surgical revascularization has been largely replaced by renal artery stenting. The potential benefit of revascularization seemed intuitive; however, the initial enthusiasm and rise in the number of percutaneous interventions have been tempered by many subsequent negative randomized clinical trials that failed to prove the proposed benefits of the percutaneous intervention. The negative randomized trial results have fallen under scrutiny due to trial design concerns and inconsistent outcomes of these studies compared to pivotal trials undertaken under US Food and Drug Administration scrutiny. Treatment of atherosclerotic renal artery occlusive disease has become one of the most debatable topics in the field of vascular disease. The results from recent randomized clinical trials of renal artery stenting have basically limited the utilization of the procedure in many centers, but not every clinical scenario was covered in those trials. There are potential areas for improvement focusing mainly on procedural details and patient selection with respect to catheter based treatment of atherosclerotic renal artery stenosis. We believe, limiting patient selection, enrollment criteria and outcomes measured functioned to reduce the benefit of renal artery stenosis stenting by not enrolling patients likely to benefit. Future studies incorporating potential procedural improvements and that include patients more likely to benefit from renal stenting than were included in ASTRAL and CORAL are needed to more carefully examine specific patient subgroups so that "the baby is not thrown out with the bath water." We also discuss several other concerns related to renal artery stenting which include diagnostic, procedure, indication, and reimbursement issues.

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

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

Biomarker response to contrast administration in diabetic and nondiabetic patients following coronary angiography

Neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C represent early renal injury markers for contrast-induced nephropathy (CIN). Baseline parameters such as type and quantity of contrast, patient preparation, renal function status, and diabetes mellitus (DM) are known to affect the response of the kidney to contrast-induced injury. This study was taken up to know the biomarker response to contrast administration in 58 diabetic and 59 nondiabetic male patients with same baseline parameters and baseline serum creatinine <1.2 mg/dl undergoing coronary angiography and their role in predicting the development of CIN. Serum creatinine, serum cystatin C, and urinary-NGAL (u-NGAL) were analyzed at baseline (0 h), 4 h, and 24 h after the administration of contrast medium. CIN was defined as a 25% increase in serum creatinine concentration from the baseline value or an absolute increase of at least 0.5 mg/dl within 48 h after the administration of contrast media. Serum creatinine rose 24 h after contrast administration in the diabetic group compared to 48 h in the nondiabetic group. Serum cystatin C levels rose 24 h after contrast administration in both the groups. The earliest marker to rise in both the groups was u-NGAL at 4 h. Diabetic patients had significantly higher u-NGAL (P = 0.005), and serum creatinine levels (P = 0.008) 4 h, and 24 h after contrast administration, respectively. Serum creatinine and u-NGAL/creatinine at 4 h were found to be the best predictors of CIN in the DM and non-DM patients, respectively. Biomarker response to contrast administration is different in diabetic and nondiabetic patients following contrast administration. Diabetic patients exhibit early and greater degree of renal impairment compared to the nondiabetic patients irrespective of the outcome. We propose the use of serum creatinine in patients with DM and u-NGAL/creatinine in non-DM patients to identify CIN as early as 4 h after contrast administration.

Hemodialysis immediately after cardiac catheterization is a risk factor for intradialytic hypotension

Many hemodialysis clinicians have noticed that patients frequently develop intradialytic hypotension (IDH) immediately after cardiac catheterization (CC). However, precise data about the incidence of IDH immediately after CC are scarce. This study involved a single-center, retrospective, cross-sectional design. We reviewed the medical records of all HD patients who underwent CC between January 2009 and March 2012 at Hiroshima Prefectural Hospital. IDH was defined as a fall of systolic blood pressure of more than 20 mm Hg or a fall of mean blood pressure of more than 10 mm Hg, with symptoms according to the K/DOQI criteria. Data on a total of 112 patients were obtained: 64 patients commenced HD immediately after CC (IA group) and 48 patients underwent HD on the day after CC (ND group). The overall incidence of IDH was 34% (38/112). The incidence of IDH was significantly higher in the IA group than in the ND group (27/64, 42% vs. 11/48, 23%; P < 0.05). Multivariate logistic regression analysis showed that IA (odds ratio, 5.39; 95% confidence interval, 1.76 to 16.49; P < 0.01), coronary stenosis (odds ratio, 4.16; 95% confidence interval, 1.49 to 11.64; P < 0.05) were independently associated with IDH. This study revealed that HD immediately after CC is associated with a higher incidence of IDH. Clinicians should consider that HD following CC be scheduled for the next day, especially in patients with coronary stenosis.

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.

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.

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.

Role of intracellular Ca2+ and Na+/Ca2+ exchanger in the pathogenesis of contrast-induced acute kidney injury

The precise mechanisms underlying contrast-induced acute kidney injury (CI-AKI) are not well understood. Intracellular Ca²⁺ overload is considered to be a key factor in CI-AKI. Voltage-dependent Ca²⁺ channel (VDC) and Na⁺/Ca²⁺ exchanger (NCX) system are the main pathways of intracellular Ca²⁺ overload in pathological conditions. Here, we review the potential underlying mechanisms involved in CI-AKI and discuss the role of NCX-mediated intracellular Ca²⁺ overload in the contrast media-induced renal tubular cell injury and renal hemodynamic disorder.

Early renal dysfunction after contrast media administration despite prophylactic hydration

The actual incidence of renal dysfunction after contrast media administration seems to be underestimated, especially in the context of epidemiological data. There are only few data concerning the monitoring of impaired kidney function within a few hours after iodine contrast medium application. Hence, the purpose of this study is to observe the incidence of early renal function deterioration within 12–18 h after administration of iodine contrast media in patients scheduled for elective coronary angiography, who were intravenously and orally hydrated. In addition, the project aims to reclassify the contrast induced nephropathy phenomenon, by identification of early markers of renal dysfunction. Morphology, electrolytes, blood urea nitrogen (BUN), creatinine, low-density lipoprotein cholesterol, triglycerides, high-density lipoprotein, and total cholesterol levels were assessed with the use of typical laboratory techniques in 319 patients referred for coronary angiography. We demonstrated that early deterioration of renal function in patients 12–18 h after administration of contrast during imaging tests (even when appropriate prophylactic hydration was used), may occurred just as an increase (or no change) of serum creatinine level and BUN level and a decrease of creatinine clearance and glomerular filtration rate. Depending on the parameter, the phenomenon can be found in 13–28 % of all respondents. Early renal function impairment defined as above was almost 2 and 2.22 × 10³ times (respectively) more frequently observed in our study than contrast induced nephropathy defined by current definitions.

Cardiological Society of India practice guidelines for angiography in patients with renal dysfunction

PREAMBLE: The potential risk of contrast-induced acute kidney injury (CI-AKI) has made utilization of coronary angiography in the work-up for the diagnosis of coronary artery disease in CKD quite low.(1) This is in contrast to increasing prevalence and severity of CAD as the serum creatinine rises.(2) In fact most CKD patients will succumb to CAD and not to ESRD.(3) Thus the judicious use of CAG/PCI in this setting is of prime importance but underused. The CSI began to develop guidelines for Indian context as most guidelines are those developed by ACC/AHA or ESC. The aim was to assist the physicians in selecting the best management strategy for an individual patient under his care based on an expert committee who would review the current data and write the guidelines with relevance to the Indian context. The guidelines were developed initially in June 2010 as an initiative of Delhi CSI. Three interventional cardiologist (SB, AS, KKS), one nephrologist (SCT) and two clinical cardiologists (ST, RG) along with Dr. Roxana Mehran (New York) and Dr. Peter McCullough (Missouri), U.S.A.; were involved in a three-way teleconference to discuss/debate the data. This was presented by SB, and over the next two hours each data subset was debated/agreed/deleted and this resulted in the "Guidelines for CAG in Renal Dysfunction Patients". These were then written and re- circulated to all for final comments. Further, these guidelines were updated and additional Task Force Members nominated by Central CSI were involved in the formation of the final CSI Guidelines. Both (Roxana Mehran and Peter McCullough) reviewed these updated Guidelines in October 2012 and after incorporating the views of all the Task Force members-the final format is as it is presented in this final document.

Kidneys in chronic liver diseases

Acute kidney injury (AKI), defined as an abrupt increase in the serum creatinine level by at least 0.3 mg/dL, occurs in about 20% of patients hospitalized for decompensating liver cirrhosis. Patients with cirrhosis are susceptible to developing AKI because of the progressive vasodilatory state, reduced effective blood volume and stimulation of vasoconstrictor hormones. The most common causes of AKI in cirrhosis are pre-renal azotemia, hepatorenal syndrome and acute tubular necrosis. Differential diagnosis is based on analysis of circumstances of AKI development, natriuresis, urine osmolality, response to withdrawal of diuretics and volume repletion, and rarely on renal biopsy. Chronic glomerulonephritis and obstructive uropathy are rare causes of azotemia in cirrhotic patients. AKI is one of the last events in the natural history of chronic liver disease, therefore, such patients should have an expedited referral for liver transplantation. Hepatorenal syndrome (HRS) is initiated by progressive portal hypertension, and may be prematurely triggered by bacterial infections, nonbacterial systemic inflammatory reactions, excessive diuresis, gastrointestinal hemorrhage, diarrhea or nephrotoxic agents. Each type of renal disease has a specific treatment approach ranging from repletion of the vascular system to renal replacement therapy. The treatment of choice in type 1 hepatorenal syndrome is a combination of vasoconstrictor with albumin infusion, which is effective in about 50% of patients. The second-line treatment of HRS involves a transjugular intrahepatic portosystemic shunt, renal vasoprotection or systems of artificial liver support.

Prevention of contrast-induced acute kidney injury by theophylline in elderly patients with chronic kidney disease

Although the optimal strategy for preventing contrast-induced acute kidney injury (CI-AKI) has not yet been established, the current strategy focuses on adequate periprocedural hydration, the use of a low amount of low or iso-osmolar contrast medium, and the application of adjunctive therapies, including hemofiltration, hemodialysis and drugs. Previous trials and meta-analyses concerning the use of the adenosine antagonist theophylline have revealed contradictory results. We sought to evaluate the effect of theophylline in CI-AKI prevention in well-hydrated elderly patients with chronic kidney disease. We therefore conducted a randomized, double-blind, placebo-controlled trial involving 56 patients who had been referred for cardiac coronary angiography and/or angioplasty. 31 of these patients were randomly assigned to 200 mg theophylline IV before the procedure, and 25 to a placebo. The iso-osmolar contrast medium iodixanol was used. The primary endpoint was an increase in serum creatinine at study termination 48 h after contrast medium administration. Baseline characteristics in the placebo and theophylline groups were similar in terms of median age (75 years), estimated glomerular filtration rate (33 ± 10 vs. 33 ± 10 ml/min/1.73 m²; p = 0.87), diabetes mellitus (80 vs. 71%; p = 0.54), and amount of contrast used (94 ± 35 vs. 95 ± 38 ml; p = 0.89). There was no difference in serum creatinine at baseline (2.06 ± 0.59 vs. 2.02 ± 0.45 mg/dl; p = 0.62) or study termination (2.06 ± 0.68 vs. 2.10 ± 0.53; p = 0.79). A prophylactic effect of theophylline was not observed. The incidence of renal impairment following exposure to the contrast medium was low. This fact can be attributed to adequate parenteral hydratation and the use of the minimum amount of contrast medium necessary.

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.

Direct coronary stenting in reducing radiation and radiocontrast consumption

Introduction

Coronary stenting is the primary means of coronary revascularization. There are two basic techniques of stent implantation: stenting with balloon predilatation of stenosis and stenting without predilatation (direct stenting). Limiting the time that a fluoroscope is activated and by appropriately managing the intensity of the applied radiation, the operator limits radiation in the environment, and this saves the exposure to the patient and all personnel in the room. Nephrotoxicity is one of the most important properties of radiocontrast. The smaller amount of radiocontrast used also provides multiple positive effects, primarily regarding the periprocedural risk for the patients with the reduced renal function. The goal of the study was to compare fluoroscopy time, the amount of radiocontrast, and expenses of material used in direct stenting and in stenting with predilatation.

Patients and methods

In a prospective study, 70 patients with coronary disease were randomized to direct stenting, or stenting with predilatation.

Results

Fluoroscopy time and radiocontrast use were significantly reduced in the directly stented patients in comparison to the patients stented with balloon-predilatation. The study showed a significant reduction of expenses when using a direct stenting method in comparison to stenting with predilatation.

Conslusions

If the operator predicts that the procedure can be performed using direct stenting, he is encouraged to do so. Direct stenting is recommended for all percutaneous coronary interventions when appropriate conditions have been met. If direct stenting has been unsuccessful, the procedure can be converted to predilatation.

Expeditious synthesis and biological evaluation of new C-6 1,2,3-triazole adenosine derivatives A1 receptor antagonists or agonists

The synthesis of new C-6 1,2,3-triazole adenosine derivatives via microwave assisted 1,3-dipolar cycloaddition as key step is described. The binding on membranes of cells that over express A(1) adenosine receptors (A(1)AR) was also evaluated. Among them, four compounds increased cAMP production, in a dose-dependent manner acting as antagonists of the A(1)AR, while two compounds act as agonists.

Contrast-induced nephropathy in patients undergoing emergency percutaneous coronary intervention for acute coronary syndrome

Contrast-induced nephropathy (CIN) is associated with significantly increased morbidity and mortality after coronary angiography and percutaneous coronary intervention (PCI). The aim of the present study was to assess the clinical features and in-hospital outcomes of CIN after emergency PCI. The serum creatinine (SCr) concentration was measured from days 0 to 30 in 338 consecutive patients with acute coronary syndrome undergoing emergency PCI. CIN was defined as an increase in SCr of >25% or >0.5 mg/dl within 2 days after PCI. Overall, 94 patients (28%) developed CIN. The mean SCr on admission was not significantly different between patients with CIN and those without CIN. The CIN group had significantly greater SCr at days 1, 2, and 30 than did the no CIN group. Multivariate analysis showed female gender (odds ratio [OR] 2.38, 95% confidence interval [CI] 1.12 to 5.07, p = 0.025), a culprit lesion in the left anterior descending artery (OR 2.37, 95% CI 1.31 to 4.27, p = 0.0042), contrast agent volume >200 ml (OR 3.60, 95% CI 1.96 to 6.62, p <0.001) and end-diastolic pulmonary arterial pressure >15 mm Hg (OR 2.03, 95% CI 1.02 to 4.04, p <0.01) to all correlate independently with CIN. The in-hospital mortality rate was greater in the CIN group than in the no CIN group (9.6% vs 3.3%, respectively; p = 0.025). In conclusion, CIN is a frequent complication of emergency PCI for acute coronary syndrome and is associated with a greater mortality rate and persistent renal dysfunction.

A comparison of sodium bicarbonate infusion versus normal saline infusion and its combination with oral acetazolamide for prevention of contrast-induced nephropathy: a randomized, double-blind trial

BACKGROUND

Contrast-induced nephropathy (CIN) is commonly encountered. Because the therapy of choice for prevention of CIN is controversial, in this study we compared the preventive efficacy of bicarbonate (Bi) infusion in dextrose water versus normal saline (NLS) infusion alone or in combination with oral acetazolamide (AZ).

METHODS

In a double-blind and randomized clinical trial, all patients undergoing coronary angiography or percutaneous coronary intervention received NLS (NLS group), its combination with AZ (AZ group) or infusion of Bi (Bi group) before the procedures. RIFLE (risk of renal failure, injury to the kidney, failure of kidney function, loss of kidney function, and end-stage renal disease) criteria were used to define CIN-associated acute kidney injury (AKI).

RESULTS

The risk of AKI in CIN was significantly lower in the Bi and AZ groups than in the NLS group (P <or= 0.04). Comparing pre-treatment and post-treatment values in each group the following results were obtained: serum creatinine (Scr) increased and eGFR decreased significantly in the NLS group (P = 0.04) and in all patients (P = 0.001, P = 0.02, respectively). In addition, serum potassium decreased significantly in the Bi and NLS groups (P <or= 0.02). Also, serum Bi increased significantly in the Bi group (P = 0.001) whereas it decreased significantly in the AZ group (P = 0.001). Urinary pH also increased in all groups (P <or= 0.04) except the NLS group (P > 0.05).

CONCLUSIONS

It seems that both Bi and AZ reduce the risk of CIN-related AKI, and close monitoring of serum potassium is needed during bicarbonate infusion.

Clinical significance and preventive strategies for contrast-induced nephropathy

PURPOSE OF REVIEW

Contrast-induced nephropathy continues to be a common cause of in-hospital acute kidney injury. Published studies on pathogenesis, clinical significance, diagnosis, and preventive measures have dramatically increased significantly in the past several years. This review will focus on new developments in contrast-induced nephropathy.

RECENT FINDINGS

Studies on the clinical significance of contrast-induced nephropathy are reviewed along with initial reports of biomarkers in diagnosing this complication of iodinated contrast administration. Emerging literature on the relative nephrotoxicity of iso-osmolar versus low-osmolar contrast media and the value of bicarbonate hydration are discussed. More recent preventive measures using prostacyclin, 'statins', and erythropoietin are also reviewed.

SUMMARY

Contrast-induced nephropathy is an increasing cause of acute kidney injury and is associated with significant mortality and morbidity. Future developments in this field will focus on refining the clinical significance of this complication, earlier diagnosis with biomarkers, clarifying the role for bicarbonate and iso-osmolar contrast agents as preventive strategies, and the introduction of new prophylactic techniques on the basis of an improved understanding of pathogenesis at the cellular level.

Renal effects of contrast media in diabetic patients undergoing diagnostic or interventional coronary angiography

BACKGROUND

The use of safe iodinated contrast media (CM) to prevent contrast-induced nephropathy (CIN) is an important consideration among renally impaired diabetic patients during coronary angiography.

HYPOTHESIS

Diabetic patients with normal or mild renal dysfunction are less likely to receive renal protective measures during angiography, yet they may also be at risk for CIN. We compared the renal effects of iopamidol and iodixanol in diabetic patients who were referred for angiography.

METHODS

Diabetic patients (N=122) with a serum creatinine (SCr) level of < or = 2 mg/dl were double-blind randomized to receive nonionic CM: iopamidol-370 (low osmolar, monomeric) or iodixanol-320 (iso-osmolar, dimeric). Renal stability was evaluated at baseline and at Days 1, 3, and 7 post-angiography. The primary endpoint was a > or = 25% increase in SCr.

RESULTS

Seventeen (10 iopamidol, 7 iodixanol; P=NS) patients had an increase in SCr > or = 25% over baseline. Over all days, analysis revealed nonsignificant differences in the incidence of CIN between the two study groups regardless of how CIN was defined.

CONCLUSIONS

Diabetic patients with normal or mild renal dysfunction are at risk for CIN. No significant difference in renal response was observed for these CM in this at-risk population.

Renal parenchymal hypoxia, hypoxia adaptation, and the pathogenesis of radiocontrast nephropathy

BACKGROUND AND OBJECTIVES

Renal parenchymal Po(2) declines after the administration of iodinated radiocontrast agents, reaching critically low levels of approximately 10 mmHg in medullary structures.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this review, the causes of renal parenchymal hypoxia and its potential role in the pathogenesis of contrast nephropathy are appraised.

RESULTS

Commonly associated predisposing factors are associated with a propensity to enhance renal hypoxia. Indeed, animal models of radiocontrast nephropathy require the induction of such predisposing factors, mimicking clinical scenarios that lead to contrast nephropathy in high-risk individuals. In these models, in association with medullary hypoxic damage, a transient local cellular hypoxia response is noted, initiated at least in part by hypoxia-inducible factors. Some predisposing conditions that are distinguished by chronically aggravated medullary hypoxia, such as tubulointerstitial disease and diabetes, are characterized by a priori upregulation of hypoxia-inducible factors, which seems to confer tolerance against radiocontrast-related hypoxic tubular damage. Renal dysfunction under such circumstances likely reflects to some extent altered intrarenal hemodynamics, rather than acute tubular injury.

CONCLUSIONS

Real-time, noninvasive novel methods may help to differentiate between evolving tubular damage and altered hemodynamics and in the design of appropriate preventive interventions.

Contrast-induced nephropathy

Interventional radiological procedures involving anaesthesia are generally increasing. Contrast-induced nephropathy (CIN), usually defined as an increase in serum creatinine of 44 micromol litre(-1) (0.5 mg dl(-1)) or a 25% increase from the baseline value 48 h after intravascular injection of contrast media, is a common and potentially serious complication of the use of iodinated contrast media in patients at risk of acute renal injury. It is an important cause of hospital-acquired renal failure, may be a difficult differential diagnosis and the incidence does not appear to have changed over the last few decades. In the general population, the incidence of CIN is estimated to be 1-2%. However, the risk for developing CIN may be as high as 50% in some patient subgroups, such as those with diabetes mellitus and pre-existing renal impairment. The impact of CIN on clinical outcomes has been evaluated most extensively in patients undergoing percutaneous coronary intervention where it is associated with increased mortality both in hospital and at 1 yr. As treatment is limited to supportive measures while awaiting the resolution of the renal impairment, emphasis needs to be directed at prevention.

Prevention and Treatment of Contrast-Induced Nephropathy

Contrast-induced nephropathy (CIN) is a well-known complication of therapeutic and diagnostic procedures requiring contrast administration and accounts for 10 to 12% of acute renal failure in hospitalized patients. Although the incidence of this complication is relatively low, its consequences can be catastrophic. The development of CIN is associated with increased hospital length of stay, an increased requirement for acute dialysis, and an increased risk of death. Preexisting renal dysfunction, age, diabetes, congestive heart failure, and volume of administered contrast are all associated with a risk of developing CIN. Despite a large number of clinical trials that have evaluated prophylaxis strategies for CIN, only the use of hemofiltration and N-acetylcysteine (NAC) in specific subgroups of patients have been shown to reduce dialysis requirement and mortality in patients undergoing angiographic procedures. In this review we will discuss the epidemiology and the risk factors for CIN and the evidence for commonly employed prophylaxis strategies, and we will provide general recommendations with respect to CIN prevention and management.

A1adenosine receptor knockout mice are protected against acute radiocontrast nephropathy in vivo

The role of renal A1adenosine receptors (A1AR) in the pathogenesis of radiocontrast nephropathy is controversial. We aimed to further elucidate the role of A1AR in the pathogenesis of radiocontrast nephropathy and determine whether renal proximal tubule A1AR contribute to the radiocontrast nephropathy. To induce radiocontrast nephropathy, A1AR wild-type (WT) or knockout (KO) mice were injected with a nonionic radiocontrast (iohexol, 1.5–3 g iodine/kg). Some A1WT mice were pretreated with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; a selective A1AR antagonist) before iohexol injection. A1AR contribute to the pathogenesis of radiocontrast nephropathy in vivo as the A1WT mice developed significantly worse acute renal failure, more renal cortex vacuolization, and had lower survival 24 h after iohexol treatment compared with the A1KO mice. DPCPX pretreatment also protected the A1WT mice against radiocontrast-induced acute renal failure. No differences in renal cortical apoptosis or inflammation were observed between A1WT and A1KO mice. To determine whether the proximal tubular A1AR mediate the direct renal cytotoxicity of radiocontrast, we treated proximal tubules in culture with iohexol with or without 2-chloro- N6-cyclopentyladenosine (a selective A1AR agonist) or DPCPX pretreatment. We also subjected cultured proximal tubule cells overexpressing A1AR or lacking A1AR to radiocontrast injury. Iohexol caused a direct dose-dependent reduction in proximal tubule cell viability as well as proliferation. Neither the A1AR agonist nor the antagonist treatment affected proximal tubule viability or proliferation. Moreover, overexpression or lack of A1AR failed to impact the iohexol toxicity on proximal tubule cells. Therefore, we conclude that radiocontrast causes acute renal failure via mechanisms dependent on A1AR; however, renal proximal tubule A1AR do not contribute to the direct tubular toxicity of radiocontrast.

Region-specific alterations of adenosine receptors expression level in kidney of diabetic rat

Pathological alterations of renal function in insulin-dependent diabetes have been attributed to numerous factors, including adenosine. This study examined the expression levels of adenosine receptors (ARs) in the kidney of the streptozotocin-induced diabetic rat. In the diabetic kidney A1-AR mRNA levels increased 1.7- and 2.8-fold in cortex and medulla, respectively. This was accompanied by increased A1-AR protein levels in membranes of kidney cortex (1.5-fold) and medulla (threefold). A1-AR immunoreactivity increased strongly along medullar tubules especially in the collecting duct. The levels of A2a-AR mRNA increased twofold in diabetic kidney cortex but remained unchanged in medulla; however, A2a-AR protein levels increased more than threefold in cortex. Immunohistochemistry showed increased A2a-AR immunoreactivity in luminal membranes of cortical collecting ducts and in epithelial cells of preglomerular vessels. There were no significant changes in A2b-AR expression in diabetic kidney except in medullar membranes, where the receptor protein content decreased by 60%. A3-AR mRNA levels in diabetic kidney remained unchanged, but membrane-associated A3-AR protein levels increased by 70% in diabetic kidney cortex and decreased by 80% in medulla. These changes in ARs genes expression, receptor protein content, and cellular and tissue distribution, correspond to abnormalities characteristic of the diabetic kidney, suggesting involvement in pathogenesis of diabetic nephropathy.

Pathophysiology of contrast medium-induced nephropathy

BACKGROUND

Contrast medium-induced nephropathy (CIN) is a well-known cause of acute renal failure, but the development of CIN remains poorly understood. A number of studies have been performed with the one aim, to shed some light onto the pathophysiology of CIN. These have led to manifold interpretations and sometimes contradicting conclusions.

METHODS

This review critically surveys mechanisms believed to mediate CIN by highlighting the complex pathophysiologic entity, including altered rheologic properties, perturbation of renal hemodynamics, regional hypoxia, auto- and paracrine factors [adenosine, endothelin, and reactive oxygen species (ROS)], and direct cytotoxic effects. Moreover, the importance of physicochemical properties of contrast media are made clear.

RESULTS

The more recently developed iso-osmolar contrast media are dimers, not monomers as the widely used nonionic low osmolar contrast media. The dimers have physicochemical features different from other contrast media which may be of clinical importance, not only with respect to osmolality. The viscosity of the commercially available dimers is considerably higher than blood.

CONCLUSION

Many experimental studies provide evidence for a greater perturbation in renal functions by dimeric contrast media in comparison to nonionic monomeric contrast media. Clinical trials have yielded conflicting results.

Perioperative diabetic and hyperglycemic management issues

OBJECTIVE AND DESIGN

To review and discuss selected literature, expert opinion, and conventional care of the hyperglycemic perioperative or critically ill patient.

MAIN POINTS

Diabetes mellitus, the most commonly encountered perioperative endocrinopathy, continues to increase dramatically in prevalence. Diabetes is the sixth most common cause of death in the United States and significantly affects other more common causes of death such as cardiac disease and stroke. Diabetic patients commonly have microvascular and macrovascular pathology that influences their perioperative course and critical illness and increases morbidity and mortality rates during hospitalization. Since diabetics require more surgeries and receive critical care more frequently than their nondiabetic counterparts, preemptive identification and anticipation of diabetic complications and comorbidities, along with an optimized treatment plan, are the foundation for the proper intensive care of this growing patient population. Hyperglycemia occurs commonly in critically ill diabetic patients but also is frequent in those who have a history of normal glucose homeostasis. The new onset of hyperglycemia in critically ill patients is driven by excessive counterregulatory stress hormone release and high tissue and circulating concentrations of inflammatory cytokines. Aggressive glycemic management improves short- and long-term outcomes in diabetic patients with acute myocardial infarction and cardiac surgical patients. Most recently, "tight" glycemic control in both diabetic and nondiabetic hyperglycemic intensive care unit patients resulted in improved survival in selected surgical patients without excessive consequences related to hypoglycemia. The mechanisms of benefit of euglycemia appear to be multifactorial.

CONCLUSIONS

Up to 25% of patients admitted to the intensive care unit have previously diagnosed diabetes. Diabetics are most commonly admitted for treatment of complications of comorbid diseases. New-onset hyperglycemia also is common in critically ill patients, and it affects patient morbidity and mortality rates. A growing body of literature supports the benefits of tight glycemic control in certain patient populations. However, further data are needed about the optimal concentration of blood glucose, the role of maintaining euglycemia in a broader group of patients (including the medically critically ill), and the mechanisms of benefit of infused glucose and insulin.

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.

Contrast agent--associated nephrotoxicity

Radiocontrast media can lead to a reversible form of acute renal failure that begins soon after the contrast dye administration and generally is benign. Contrast media accounts for 10% of all causes of hospital-acquired acute renal failure and represents the third leading cause of in-hospital renal function deterioration after decreased renal perfusion and postoperative renal insufficiency. The in-hospital mortality rate in patients developing renal insufficiency is related directly to the magnitude increase of serum creatinine concentration. The mortality rate ranges from 3.8% with an increase in serum creatinine level of 0.5 to 0.9 mg/dL to 64% with an increase of greater than 3.0 mg/dL. The mechanism by which contrast-induced renal failure occurs is not well understood. Contrast agent-associated nephrotoxicity appears to be a result of direct contrast-induced renal tubular epithelial cell toxicity and renal medullary ischemia. Furthermore, a key mechanism seems to be alteration in renal dynamics, probably caused by imbalances between vasodilator and vasoconstrictor factors, including the activities of nitric oxide, prostaglandins, endothelin, and reactive oxygen species. The optimal strategy to prevent contrast-associated nephrotoxicity remains uncertain. At present, recommendations are as follows: (1) periprocedural hydration, (2) use of a low-osmolality contrast, and (3) limiting the amount of contrast agent. Recently, considerable interest has resulted from the preliminary positive data on the effectiveness of prophylactic administration of acetylcysteine and fenoldopam. The former may prevent the direct oxidative tissue damage, whereas the latter is a selective intrarenal vasodilator.

A randomized trial of prophylactic acetylcysteine and theophylline compared with placebo for the prevention of renal tubular vacuolization in rats after iohexol administration

RATIONALE AND OBJECTIVES

Renal tubular vacuolization (RTV), which has been shown to occur after the use of iodinated contrast material, may be one of the earliest signs of contrast medium-induced renal injury. In this study, the authors tested a method for preventing RTV with the administration of acetylcysteine, theophylline, or both, prior to contrast medium administration.

MATERIALS AND METHODS

Eighty rats were randomly selected for inclusion in the study. The treatment group consisted of three subgroups, each of which received prophylactic acetylcysteine, theophylline, or both before injection of iohexol. The control group comprised five subgroups, each of which received acetylcysteine, theophylline, both, normal saline injection, or orally administered normal saline prior to iohexol injection.

RESULTS

The occurrence of RTV in the treatment groups was compared with that in the control subgroup that received normal saline and iohexol. All of the rats in that control subgroup (n = 10) and 97% of the rats in the treatment group (n = 30) developed RTV.

CONCLUSION

The administration of acetylcysteine, theophylline, or both prior to iohexol injection did not prevent RTV from occurring in rats.

Radiocontrast induced nephropathy

In spite of improvements in chemical structure, contrast media assisted X-ray examination is still the third leading cause of hospital-acquired acute renal failure. An increase >50% or >88 micro mol/L in S-creatinine is a clinically important acute renal failure. The peak in S-creatinine occurs within 2-5 days after exposure. The frequency of oliguria, transient or permanent haemodialysis is unknown. The cause is a hypoxic tubular injury due to vasoconstriction with release of free oxygen radicals. Major risk factors are prior renal insufficiency and diabetes mellitus. Minor risk factors are congestive heart disease, dehydration, hypotension, hypoxia, amount of contrast, ionic and high osmolar contrast, repeated examinations at short intervals, abdominal examination, and perhaps age, smoking, hypercholesterolaemia, and use of Non-Steroidal Anti inflammatory Drug. Prevention seems possible by omission or reduction of contrast, ameliorating predisposing factors, saline hydration 24h before and after exposure, and 600 mg acetylcysteine orally twice daily 24h before and after exposure. A three-day treatment with 20mg nitrendipine daily, starting 1 day before examination may also be preventive. The present research is unfortunately characterised by small numbers, lack of clinical important renal failure, and lack of long term results. The latter may be important after new data indicate that radiation may trigger a chronic oxidative process through a similar pathway.

Contrast nephropathy : an evidence-based approach to prevention

Contrast-induced nephropathy occurs in 2-10% of patients exposed to intravascular radiographic contrast agents and results in significant morbidity and mortality. Although the exact mechanism of this disorder has not been fully elucidated, contrast nephropathy is probably due to a combination of decreased renal medullary blood flow, resulting in medullary ischemia, and direct toxicity to renal tubules. Contrast nephropathy is most commonly defined as either a >25% increase or a >0.5 mg/dL rise in serum creatinine level within 48 hours of contrast medium exposure. Baseline characteristics associated with an increased risk for development of contrast nephropathy include the presence of baseline renal dysfunction, diabetes mellitus, congestive heart failure, volume depletion, and concomitant administration of nephrotoxic drugs. Many strategies have been investigated in an effort to prevent the occurrence of renal dysfunction following contrast media exposure. Intravenous hydration has been shown to significantly decrease the incidence of nephropathy in high-risk patients. However, trials of several prophylactic pharmacologic interventions have been mostly disappointing, including the administration of calcium channel antagonists, diuretics, dopamine, endothelin receptor antagonists and fenoldopam. The use of N-acetylcysteine has been shown in some trials to decrease the incidence of contrast nephropathy in patients with a baseline renal dysfunction, and should currently be strongly considered in this high-risk patient subgroup in addition to hydration. Our purpose is to review the contemporary literature regarding contrast-induced renal dysfunction and present an evidence-based approach for prevention of this complication.

Incidence and prognostic importance of acute renal failure after percutaneous coronary intervention

BACKGROUND

In patients undergoing percutaneous coronary intervention (PCI) in the modern era, the incidence and prognostic implications of acute renal failure (ARF) are unknown.

METHODS AND RESULTS

With a retrospective analysis of the Mayo Clinic PCI registry, we determined the incidence of, risk factors for, and prognostic implications of ARF (defined as an increase in serum creatinine [Cr] >0.5 mg/dL from baseline) after PCI. Of 7586 patients, 254 (3.3%) experienced ARF. Among patients with baseline Cr <2.0, the risk of ARF was higher among diabetic than nondiabetic patients, whereas among those with a baseline Cr >2.0, all had a significant risk of ARF. In multivariate analysis, ARF was associated with baseline serum Cr, acute myocardial infarction, shock, and volume of contrast medium administered. Twenty-two percent of patients with ARF died during the index hospitalization compared with only 1.4% of patients without ARF (P<0.0001). After adjustment, ARF remained strongly associated with death. Among hospital survivors with ARF, 1- and 5-year estimated mortality rates were 12.1% and 44.6%, respectively, much greater than the 3.7% and 14.5% mortality rates in patients without ARF (P<0.0001).

CONCLUSIONS

The overall incidence of ARF after PCI is low. Diabetic patients with baseline Cr values <2.0 mg/dL are at higher risk than nondiabetic patients, whereas all patients with a serum Cr >2.0 are at high risk for ARF. ARF was highly correlated with death during the index hospitalization and after dismissal.