Nephrotoxicity from contrast media: attenuation with theophylline

Prevention and Management of AKI in ACS Patients Undergoing Invasive Treatments

PURPOSE OF REVIEW

Management of patients presenting with acute coronary syndrome (ACS) includes invasive procedures that may increase the risk of acute kidney injury (AKI). AKI adversely affects the outcomes of such procedures and complicates the management of ACS. We have summarized several strategies for the prevention and management of AKI in this critical patient group including in the pre-procedural, intraprocedural, and post-procedural settings.

RECENT FINDINGS

Definitive prevention and management strategies for AKI in patients presenting with ACS requiring invasive management can be confounded by the variation in data outcomes. Pre-procedural hydration with normal saline when accounting for time to catheterization, radial artery access, contrast stewardship, and close monitoring of renal function after catheterization should be implemented.

Contrast-Associated Acute Kidney Injury

Contrast-associated acute kidney injury (CA-AKI) is an impairment of renal function, which occurs within days of intravascular administration of iodinated contrast media. Taking into account that minimally invasive cardiac interventions are becoming increasingly popular, compared to traditional surgery, given their impact on prognosis and costs, CA-AKI remains a subject of increasing interest for patients and physicians. This review summarizes the epidemiology and risk stratification, diagnostic criteria, pathophysiology and clinical implications of CA-AKI, providing evidence for the most studied preventive strategies.

High Channel Temperature Mapping Electronics in a Thin, Soft, Wireless Format for Non-Invasive Body Thermal Analysis

Hemodynamic status has been perceived as an important diagnostic value as fundamental physiological health conditions, including decisive signs of fatal diseases like arteriosclerosis, can be diagnosed by monitoring it. Currently, the conventional hemodynamic monitoring methods highly rely on imaging techniques requiring inconveniently large numbers of operation procedures and equipment for mapping and with a high risk of radiation exposure. Herein, an ultra-thin, noninvasive, and flexible electronic skin (e-skin) hemodynamic monitoring system based on the thermal properties of blood vessels underneath the epidermis that can be portably attached to the skin for operation is introduced. Through a series of thermal sensors, the temperatures of each subsection of the arrayed sensors are observed in real-time, and the measurements are transmitted and displayed on the screen of an external device wirelessly through a Bluetooth module using a graphical user interface (GUI). The degrees of the thermal property of subsections are indicated with a spectrum of colors that specify the hemodynamic status of the target vessel. In addition, as the sensors are installed on a soft substrate, they can operate under twisting and bending without any malfunction. These characteristics of e-skin sensors exhibit great potential in wearable and portable diagnostics including point-of-care (POC) devices.

Current comments on contrast media administration in patients with renal insufficiency

Contrast media administration has been associated with complications such as nephropathy, cardiovascular morbidity, and neurovascular events, particularly in patients with renal insufficiency. This association has been questioned in recent studies. This review was performed to summarize the most current evidence on contrast induced nephropathy (CIN), contributing factors, and considerations in patients with renal insufficiency. The risk of CIN was over-estimated by the previous studies, due to a lack of control groups or presence of non-randomized control groups, which led to a selection bias. However, the thresholds associated with an increased risk of CIN are controversial and require risk-benefit analysis on an individual basis. Regarding the administration of contrast media (CM) in the emergency setting, the majority of studies suggested that CM exposure does not meaningfully increase the risk of acute kidney injury in critically ill patients (including trauma patients). Several strategies have been suggested to reduce the risk of CIN, including volume expansion to increase renal blood flow, sodium bicarbonate or N-acetylcysteine administration, and use of low-osmolal contrast media in end-stage renal disease.

A risk scoring model to predict renal progression associated with postcontrast acute kidney injury in chronic kidney disease patients

Postcontrast acute kidney injury (AKI) occurs more frequently in patients with lower estimated glomerular filtration rate. We hypothesized that postcontrast AKI in chronic kidney disease (CKD) patients with distinct risk factors might be associated with accelerated renal progression.We undertook this retrospective cohort study to develop and validate a risk scoring model for predicting renal progression. In a development dataset, 18,278 contrast-enhanced CT scans were performed in 9097 patients with CKD (estimated glomerular filtration rate [eGFR] < 60 mL/min/1.73 m) who were not undergoing dialysis. Postcontrast AKI was observed in 5.8% (1051/18,278) of all contrast-enhanced CTs with 7.6% (689/9097) of the total CKD patients. We investigated the 1-year renal outcome in 224 eligible patients. A risk scoring model was developed with multivariate regression analysis and was assessed in external validation (independent 154 patients).Among 224 patients, 70 (31.3%) patients had progression of renal dysfunction at 1 year (defined as reduction in estimated GFR ≥25% at 1 year). A risk score of 4, 4, 6, 6, 7, or 6 was assigned to diabetes, baseline estimated GFR < 45 mL/min/1.73 m, hypertension, repeated contrast exposure, congestive heart failure, and persistent renal injury (defined as an elevation of serum creatinine ≥25% at 3 months), respectively. An increasing risk score was associated with renal progression. Of note, persistent renal injury was more prevalent in the progression group than in the non-progression group. The AUROC of the model in the development population was 0.765. In the validation dataset, however, the discriminative power decreased (AUROC = 0.653).Our suggested model provided the risk of renal progression, aiding in predicting prognosis, counseling, and improving outcomes in CKD patients complicated by postcontrast AKI.

Effectiveness of contrast-associated acute kidney injury prevention methods; a systematic review and network meta-analysis

BACKGROUND

Different methods to prevent contrast-associated acute kidney injury (CA-AKI) have been proposed in recent years. We performed a mixed treatment comparison to evaluate and rank suggested interventions.

METHODS

A comprehensive Systematic review and a Bayesian network meta-analysis of randomised controlled trials was completed. Results were tabulated and graphically represented using a network diagram; forest plots and league tables were shown to rank treatments by the surface under the cumulative ranking curve (SUCRA). A stacked bar chart rankogram was generated. We performed main analysis with 200 RCTs and three analyses according to contrast media and high or normal baseline renal profile that includes 173, 112 & 60 RCTs respectively.

RESULTS

We have included 200 trials with 42,273 patients and 44 interventions. The primary outcome was CI-AKI, defined as ≥25% relative increase or ≥ 0.5 mg/dl increase from baseline creatinine one to 5 days post contrast exposure. The top ranked interventions through different analyses were Allopurinol, Prostaglandin E1 (PGE1) & Oxygen (0.9647, 0.7809 & 0.7527 in the main analysis). Comparatively, reference treatment intravenous hydration was ranked lower but better than Placebo (0.3124 VS 0.2694 in the main analysis).

CONCLUSION

Multiple CA-AKI preventive interventions have been tested in RCTs. This network evaluates data for all the explored options. The results suggest that some options (particularly allopurinol, PGE1 & Oxygen) deserve further evaluation in a larger well-designed RCTs.

Prevention of Contrast Nephropathy in Critically Ill Patients Using Acetylcysteine and Theophylline

Compared with periprocedural hydration alone, acetylcysteine with hydration significantly reduces the risk of contrast nephropathy in patients with chronic renal insufficiency by 50%. For elective contrast procedures, acetylcysteine should be given in a dose of 600 mg twice daily the day before and on the procedure day. For emergency procedures, a high dose intravenous regimen (150 mg/kg in 500 mL normal saline over 30 minutes immediately before contrast followed by 50 mg/kg in 500 mL normal saline over 4h) is effective. Given the low cost and good side-effect profile of acetylcysteine, it would seem prudent to give this drug with intravenous fluids to all critically ill patients scheduled for intravenous or intraarterial contrast procedures. Theophylline in a dose of 200 mg or 2.5 mg/kg IV 30 minutes before contrast may be an effective alternative for emergency procedures. Although its benefit compared with periprocedural hydration alone seems less well established, theophylline is a particularly attractive option for emergency procedures.

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.

Coadministration of Liposomal Amphotericin B and Contrast Medium Does Not Increase Risk of Kidney Injury

Intravenous radiographic contrast medium and amphotericin B are commonly required in the care of patients with fungal infections. Both interventions have proposed nephrotoxicity through similar mechanisms. We systematically examined patients who received coadministration of liposomal amphotericin B (AmBisome; GE Healthcare) and intravenous contrast medium within a 24-h period and compared the results for those patients with the results for patients who underwent non-contrast medium studies. We found 114 cases and 85 controls during our study period. Overall, no increased risk of renal injury was seen with coadministration of these 2 agents. Adjustment for age, baseline kidney function, and other clinical factors through propensity score adjustment did not change this result. Our observations suggest that, when clinically indicated, coadministration of contrast medium and liposomal amphotericin B does not present excess risk compared with that from the administration of liposomal amphotericin B alone.

Contrast-induced acute kidney injury in interventional cardiology: Emerging evidence and unifying mechanisms of protection by remote ischemic conditioning

Contrast-induced acute kidney injury (CI-AKI) is a common complication of many diagnostic and therapeutic cardiovascular procedures. It is associated with longer in-hospital stay, more complicated hospitalization course, and higher in-hospital morbidity and mortality. With increasing use of contrast media in various diagnostic and interventional procedures, the prevalence of CI-AKI is expected to rise. Although pre-hydration with intravenous normal saline is recommended in patients with elevated risk of CI-AKI, this approach is often not feasible in many clinical settings. Remote ischemic conditioning (RIC), elicited by application of one or more, brief, non-injurious episodes of ischemia and reperfusion of a limb, is a promising therapy for preventing or attenuating the deleterious effects of contrast media on the kidney. Although the mechanisms of protection by RIC have not been completely defined, complex humoral, neural, and inflammatory pathways have been hypothesized to be in play. Given that RIC is non-invasive and cheap, it is attractive from clinical and economic perspective as a therapy to protect the kidney from CI-AKI. In this succinct review, we highlight the unifying mechanisms of CI-AKI and provide an overview of proposed biological mechanisms of renal protection by RIC. Emerging pre-clinical and clinical evidence in interventional cardiology is also discussed.

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.

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.

Contrast-Induced Acute Kidney Injury: An Update

Contrast-induced acute kidney injury (CI-AKI) is defined as an abrupt deterioration in renal function associated with the administration of iodinated contrast media. This type of acute kidney injury is frequently encountered as a complication of percutaneous coronary intervention (PCI) and is associated with adverse short- and long-term outcomes including mainly mortality, cardiovascular morbidity and prolongation of hospitalization. The incidence of CI-AKI after PCI ranges from 2 to 20 % according to baseline kidney function. It may also range according to the clinical setting, being higher after emergency PCI. The primary manifestation is a small decline in kidney function, occurring 1 to 3 days after the procedure. Kidney function usually returns to preexisting levels within 7 days. Incidence of acute renal failure requiring dialysis following PCI is rare (<1 %). The present article aims to review up-to-date published data concerning diagnosis, definition, epidemiology and prognosis of this novel in-hospital epidemic.

Comparative Effectiveness of 12 Treatment Strategies for Preventing Contrast-Induced Acute Kidney Injury: A Systematic Review and Bayesian Network Meta-analysis

BACKGROUND

To simultaneously evaluate the relative efficacy of multiple pharmacologic strategies for preventing contrast-induced acute kidney injury (AKI).

STUDY DESIGN

Systematic review containing a Bayesian network meta-analysis of randomized controlled trials.

SETTING & POPULATION

Participants undergoing diagnostic and/or interventional procedures with contrast media.

SELECTION CRITERIA FOR STUDIES

Randomized controlled trials comparing the active drug treatments with each other or with hydration alone.

INTERVENTION

Any of the following drugs in combination with hydration: N-acetylcysteine (NAC), theophylline (aminophylline), fenoldopam, iloprost, alprostadil, prostaglandin E₁, statins, statins plus NAC, bicarbonate sodium, bicarbonate sodium plus NAC, ascorbic acid (vitamin C), tocopherol (vitamin E), α-lipoic acid, atrial natriuretic peptide, B-type natriuretic peptide, and carperitide.

OUTCOMES

The occurrence of contrast-induced AKI.

RESULTS

The trial network included 150 trials with 31,631 participants and 4,182 contrast-induced AKI events assessing 12 different interventions. Compared to hydration, ORs (95% credible intervals) for contrast-induced AKI were 0.31 (0.14-0.60) for high-dose statin plus NAC, 0.37 (0.19-0.64) for high-dose statin alone, 0.37 (0.17-0.72) for prostaglandins, 0.48 (0.26-0.82) for theophylline, 0.62 (0.40-0.88) for bicarbonate sodium plus NAC, 0.67 (0.54-0.81) for NAC alone, 0.64 (0.41-0.95) for vitamins and analogues, 0.70 (0.29-1.37) for natriuretic peptides, 0.69 (0.31-1.37) for fenoldopam, 0.78 (0.59-1.01) for bicarbonate sodium, and 0.98 (0.41-2.07) for low-dose statin. High-dose statin plus NAC or high-dose statin alone were likely to be ranked the best or the second best for preventing contrast-induced AKI. The overall results were not materially changed in metaregressions or subgroup and sensitivity analyses.

LIMITATIONS

Patient-level data were unavailable; unable to include some treatment agents; low event rates; imbalanced distribution of participants among treatment strategies.

CONCLUSIONS

High-dose statins plus hydration with or without NAC might be the preferred treatment strategy to prevent contrast-induced AKI in patients undergoing diagnostic and/or interventional procedures requiring contrast media.

Radiocontrast-Induced Acute Renal Failure

The intravascular administration of iodinated radiocontrast media can lead to acute renal dysfunction. Even small changes in renal function have been associated with increased morbidity and mortality, making the prevention of radiocontrast nephropathy of paramount importance. This review summarizes the principal risk factors for radiocontrast nephropathy and evidence-based preventive strategies that should be used to limit its occurrence. Risk factors for radiocontrast nephropathy include preexistent kidney disease, diabetes mellitus, dose of radiocontrast used, advanced congestive heart failure, and intravascular volume depletion. Proven preventive measures include volume expansion with intravenous saline or sodium bicarbonate and the use of low-osmolar or iso-osmolar radiocontrast media. Studies evaluating N-acetylcysteine have been conflicting, with meta-analyses suggesting a small beneficial effect. Studies of other pharmacologic agents have not demonstrated clinical benefit.

The efficacy of theophylline in preventing cisplatin-related nephrotoxicity in patients with cancer

OBJECTIVE

Cisplatin is a potent antineoplastic agent used and its major limiting side effect is nephrotoxicity. The aims of the study are early detection of acute kidney injury (AKI) with biomarkers and investigation of the potential nephron-protective effects of theophylline.

METHODS

Glomerular filtration rates (GFR), neutrophil gelatinase-associated lipocalin (NGAL), cystatin C were measured at 5th day of treatment in all of the patients. In addition, these parameters were measured repeatedly after the administration of cisplatin, at 2nd hour, 5th and 20th days.

PATIENTS

Sixty patients who are planned to receive cisplatin for the first time were included in the study. Patients were divided into two groups as Group 1 (n = 30) (standard treatment arm) and Group II (n = 30) (theophylline arm).

RESULTS

In both groups after the administration of cisplatin, GFR showed a significant decrease within time (p = 0.006). Urine NGAL levels were significantly high after 2 h of cisplatin administration (p < 0.001), no significant difference was observed between groups. However, when the time*group effects were considered together, higher NGAL levels were detected in the group not receiving theophylline (p = 0.025). After 5 days of cisplatin administration, urine protein levels were significantly higher in both groups (p < 0.001).

CONCLUSION

Results showed that urine NGAL level is a superior biomarker compared to serum creatinine and serum cystatin C in the detection of early AKI. Theophylline was found not to bring a complete protection for the kidneys, but less nephrotoxicity was developed when compared to the group not receiving theophylline.

Contrast Medium Exposure During Computed Tomography and Risk of Development of End-Stage Renal Disease in Patients With Chronic Kidney Disease: A Nationwide Population-Based, Propensity Score-Matched, Longitudinal Follow-Up Study

The aim of the study was to investigate the long-term association between contrast medium exposure during computed tomography (CT) and the subsequent development of end-stage renal disease (ESRD) in patients with chronic kidney disease (CKD). We conducted a population-based cohort study using Taiwan's National Health Insurance Research Database. A total of 7100 patients with nonadvanced CKD who underwent contrast medium-enhanced CT were identified and served as the study cohort. To avoid selection bias, we used the propensity score to match 7100 nonadvanced CKD patients, who underwent noncontrast medium-enhanced CT to serve as the comparison cohort. The age, sex, index year, and frequency of undergoing CTs were also matched between the study and comparison cohorts. Participants were followed until a new diagnosis of ESRD or December 31, 2011. Hazard ratios (HRs) with 95% confidence interval (95% CI) were calculated using the Cox proportional hazards regression. Contrast medium exposure was not identified as a risk factor for developing ESRD in nonadvanced CKD patients after confounders adjustment (adjusted HR = 0.91; 95% CI, 0.66-1.26; P = 0.580). We further divided the patients who underwent CTs with contrast medium use into ≤1 exposure per year on average, >1 and <2 exposure per year on average, and ≥2 exposure per year on average. After adjusting for confounders, we identified a much higher risk for developing ESRD in the 2 groups of >1 and <2 exposure per year on average and ≥2 exposure per year on average (adjusted HR = 8.13; 95% CI, 5.57-11.87 and adjusted HR = 12.08; 95% CI, 7.39-19.75, respectively) compared with the patients who underwent CTs without contrast medium use. This long-term follow-up study demonstrated that contrast medium exposure was not associated with an increased risk of ESRD development in nonadvanced CKD patients.

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.

The role of inflammation in contrast-induced nephropathy

Objective:

Global incidence of contrast-induced nephropathy (CIN) is 2–5%, but a recent Kenyan study highlighted a local incidence of 12–14% without offering an explanation for the higher incidence. This study proposes that inflammatory states confer a higher relative risk for development of CIN. Our objective was to determine the risk of developing CIN given the presence of an inflammatory state in patients in Kenya.

Methods:

Prospective cohort study of patients undergoing a contrast-enhanced CT (CECT) scan in a private university teaching hospital in Kenya and having no known risk factors for CIN. 423 patients were recruited and grouped into those without inflammation (unexposed) having serum C-reactive protein (CRP) levels ≤5 mg dl⁻¹ and those with evidence of inflammation having CRP levels >5 mg dl⁻¹. Serum creatinine (SCr) was measured before the CECT and 48 h following the CECT with CIN diagnosed by an increase of >25% in the SCr from the baseline. Relative risk was determined and multiple logistic regression analysis performed on biophysical variables and contrast volume to assess their effect on development of CIN.

Results:

Patients with high CRP levels had a relative risk of developing CIN of 2.16 compared with those with normal levels of CRP (p = 0.016). No statistically significant association was seen between biophysical variables or volume of contrast and development of CIN.

Conclusion:

Ongoing inflammation doubles the likelihood of development of CIN.

Advances in knowledge:

This study highlights the importance of inflammation as a risk factor in the development of CIN.

Renal Complications in Patients Undergoing Peripheral Artery Interventions

Surgical or endovascular revascularization procedures for severe peripheral artery disease (PAD) are typically performed in patients with lifestyle-limiting symptoms or evidence of end-organ ischemia secondary to PAD. The role of endovascular therapy in the treatment of PAD is expanding. Contrast-induced nephropathy is the most important and most frequent renal complication of endovascular interventional procedures. Knowledge about complications and their prevention and management is essential for successful outcomes. This article focuses on renal complications during peripheral artery interventions.

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.

Molecular mechanisms of renal cellular nephrotoxicity due to radiocontrast media

Modern iodinated radiocontrast media are all based on the triiodinated benzene ring with various chemical modifications having been made over the last few decades in order to reduce their toxicity. However, CIN remains a problem especially in patients with pre-existing renal failure. In vitro studies have demonstrated that all RCM are cytotoxic. RCM administration in vivo may lead to a decrease in renal medullary oxygenation leading to the generation of reactive oxygen species that may cause harmful effects to renal tissue. In addition, endothelin and adenosine release and decreased nitric oxide levels may worsen the hypoxic milieu. In vitro cell culture studies together with sparse in vivo rat model data have shown that important cell signalling pathways are affected by RCM. In particular, the prosurvival and proproliferative kinases Akt and ERK1/2 have been shown to be dephosphorylated (deactivated), whilst proinflammatory/cell death molecules such as the p38 and JNK kinases and the transcription factor NF- κ B may be activated by RCM, accompanied by activation of apoptotic mediators such as caspases. Increasing our knowledge of the mechanisms of RCM action may help to develop future therapies for CIN.

The use of nitrates in the prevention of contrast-induced nephropathy in patients hospitalized after undergoing percutaneous coronary intervention

Contrast-induced nephropathy (CIN) is a significant cause of morbidity and mortality and effective strategies for its prevention are greatly needed. The purpose of this retrospective, single-center study was to investigate whether nitrate use during percutaneous coronary artery intervention reduces the incidence of CIN. Chart review of all individuals who underwent percutaneous coronary intervention (PCI) from April 2010 to March 2011 was done. Included in the study were patients who were admitted to the hospital after percutaneous coronary artery intervention and had baseline and follow-up creatinine measured. Patients with end-stage renal disease requiring dialysis and those patients with insufficient information to calculate Mehran score were excluded. There were 199 patients who met the eligibility criteria for inclusion in this study. In the identified population, postprocedure renal function was compared between 112 patients who received nitrates prior to coronary intervention and 87 who did not. Baseline characteristics were similar between the 2 groups. Contrast-induced nephropathy was defined as either a 25% or a 0.5 mg/dL, or greater, increase in serum creatinine during the first 48 to 72 hours after contrast exposure. Overall, 43 (21.6%) patients developed CIN post-PCI. Of the patients who received nitrates, 15.2% developed renal impairment when compared to 29.9% in those who did not (odds ratio [OR] = 0.42, 95% confidence interval [CI] 0.21-0.84, P = .014). Multivariate logistic regression analysis demonstrated that nitrate use was independently correlated with a reduction in the development of contrast nephropathy (OR = 0.334, 95% CI 0.157-0.709, P = .004). Additionally, of the various methods of nitrate administration, intravenous infusion was shown to be the most efficacious route in preventing renal impairment (OR = 0.42, 95% CI 0.20-0.90, P = .03). In conclusion, the use of nitrates prior to PCI, particularly intravenous nitroglycerin infusion, may be associated with a decreased incidence of CIN.

Why is diabetes mellitus a risk factor for contrast-induced nephropathy?

Contrast-induced nephropathy (CIN) remains a leading cause of iatrogenic acute kidney injury, as the usage of contrast media for imaging and intravascular intervention keeps expanding. Diabetes is an important predisposing factor for CIN, particularly in patients with renal functional impairment. Renal hypoxia, combined with the generation of reactive oxygen species, plays a central role in the pathogenesis of CIN, and the diabetic kidney is particularly susceptible to intensified hypoxic and oxidative stress following the administration of contrast media. The pathophysiology of this vulnerability is complex and involves various mechanisms, including a priori enhanced tubular transport activity, oxygen consumption, and the generation of reactive oxygen species. The regulation of vascular tone and peritubular blood flow may also be altered, particularly due to defective nitrovasodilation, enhanced endothelin production, and a particular hyperresponsiveness to adenosine-related vasoconstriction. In addition, micro- and macrovascular diseases and chronic tubulointerstitial changes further compromise regional oxygen delivery, and renal antioxidant capacity might be hampered. A better understanding of these mechanisms and their control in the diabetic patient may initiate novel strategies in the prevention of contrast nephropathy in these susceptible patients.

Radiographic contrast-media-induced acute kidney injury: pathophysiology and prophylactic strategies

Contrast-induced acute kidney injury (CI-AKI) is one of the most widely discussed and debated topics in cardiovascular medicine. With increasing number of contrast-media- (CM-) enhanced imaging studies being performed and growing octogenarian population with significant comorbidities, incidence of CI-AKI remains high. In this review, pathophysiology of CI-AKI, its relationship with different types of CM, role of serum and urinary biomarkers for diagnosing CI-AKI, and various prophylactic strategies used for nephroprotection against CI-AKI are discussed in detail.

Measures used to treat contrast-induced nephropathy: overview of reviews

OBJECTIVES

Despite many interventions that have been tried, controversy remains regarding the efficacy of interventions for contrast-induced nephropathy (CIN), so we aimed to evaluate the best evidence from recent meta-analyses.

METHODS

We searched MEDLINE, EMBASE and the Cochrane library for interventions which have been used for CIN. We included only the most recent meta-analysis of each intervention. We extracted data on the methodology, quality and results of each meta-analysis. We performed narrative synthesis and adjusted indirect comparison of interventions that were shown to be statistically significant compared with a placebo.

RESULTS

We included 7 systematic reviews and meta-analyses involving 9 different interventions for CIN, with a total of 15 976 participants. A significantly decreased risk of CIN was reported in meta-analysis of the following interventions: N-acetylcysteine [odds ratio (OR) 0.65, 95% confidence interval (CI) 0.48-0.88, I(2)=64%], theophylline [relative risk (RR) 0.48, 95% CI 0.26-0.89, I(2)=44%], statins (RR 0.51, 95% CI 0.34-0.77, I(2)=0%) and sodium bicarbonate (RR 0.62, 95% CI 0.45-0.86, I(2)=49%). Furosemide was shown to increase the risk of CIN (RR 3.27, 95% CI 1.48-7.26, I(2)=0%). Other interventions such as renal replacement therapy, angiotensin-converting enzyme inhibitors, dopamine and fenoldapam failed to show any significant difference from the control group.

CONCLUSION

Although there is some evidence to suggest that N-acetylcysteine, theophylline, sodium bicarbonate and statins may reduce incidence of CIN, limitations in the study quality and heterogeneity preclude any firm recommendations.

ADVANCES IN KNOWLEDGE

N-acetylcysteine, theophylline, sodium bicarbonate and statins show some promise as potentially efficacious agents for preventing CIN, but more high-quality studies are needed before they can be recommended for use in routine practice.

An uninvestigated risk factor for contrast-induced nephropathy in chronic kidney disease: proteinuria

BACKGROUND

Contrast-induced nephropathy (CIN) is one of the most frequent causes of acute renal failure in hospitalized patients with the incremental use of contrast media. We aimed to investigate whether proteinuria may act as a risk factor for CIN in patients with chronic kidney disease.

METHODS

Seventy hospitalized patients (37 men, 33 women) with chronic kidney disease, proteinuria, and/or estimated glomerular filtration rate (eGFR) of <60 mL/min/1.73 m2, who were exposed to contrast media were investigated prospectively. Thirty patients were diabetic. All patients received prophylaxis against CIN with acetylcysteine and 0.9% intravenous saline. CIN is defined as either a 25% higher increase in serum creatinine (sCr) from the baseline levels or a 0.5 mg/dL increase in sCr at 72 h after contrast media exposure.

RESULTS

CIN was detected in 26 (37.1%) patients. Advanced age, diabetes, heart failure, anemia, baseline sCr of >1.5 mg/dL, baseline eGFR of <60 mL/min/1.73 m(2), proteinuria of ≥1 g/day, hypoalbuminemia, and the volume of contrast media of ≥100 mL correlated significantly with CIN. The frequency of CIN was significantly higher in patients with proteinuria of ≥1 g/day compared to patients with proteinuria of <1 g/day (p = 0.009).

CONCLUSION

Proteinuria may be a new risk factor for the development of CIN in patients with chronic kidney disease.

Effectiveness of theophylline in preventing contrast-induced nephropathy after coronary angiographic procedures

BACKGROUND

Contrast-induced nephropathy (CIN) is the third most common cause of hospital acquired acute renal failure and is associated with increased morbidity and mortality. The use of theophylline for prevention of CIN has yielded conflicting results. This study aimed at examining the effectiveness of theophylline in prevention of CIN when added to IV hydration and N-acetylcysteine (NAC).

METHODS

Patients with stable serum creatinine and at least moderate risk for CIN according to Mehran's risk score were included in this parallel group, 1:1, single-blind, randomized controlled trial. All patients received IV hydration (1 mL/kg per hour for 24 hours) and NAC (600 mg bid for 2 days). Patients were randomized to placebo (group P) or theophylline (200 mg in 100 mL 0.9% saline, as IV infusion 30 minutes before contrast medium (CM) administration; group T). Patients underwent standard coronary angiography ± angioplasty. Serum creatinine (SCr) was assessed just before and 72 hours after contrast administration and estimated glomerular filtration rate (eGFR) was calculated.

RESULTS

This study included 60 patients with mean SCr 1.44 ± 0.7 mg/dL and eGFR 60.2 ± 29.2 mL/min. Mean SCr among group T was 1.54 ± 0.7 mg/dL with eGFR 58.6 ± 28.6 mL/min, while group P showed mean SCr of 1.34 ± 0.7 mg/dL and eGFR of 61.8 ± 30.1 mL/min. Among group P, 6 (20%) patients developed CIN while none of the patients in group T developed CIN. In comparison to placebo, theophylline significantly decreased SCr (P = 0.0001) and increased eGFR (P = 0.001) at 72 hours. Multivariate regression analysis showed that receiving placebo instead of theophylline, anemia, congestive heart failure, chronic renal impairment, and high-contrast load are all independent predictors for deteriorating renal function after CM administration.

CONCLUSION

Theophylline seems to be an effective prophylaxis against CIN for moderate- and high-risk patients undergoing coronary angiography or angioplasty. It offers additive protection when added to IV hydration and NAC.

Efficacy of allopurinol pretreatment for prevention of contrast-induced nephropathy: a randomized controlled trial

BACKGROUND

Contrast-induced nephropathy (CIN) remains a common complication of radiographic procedures. Radiocontrast agents can cause a reduction in renal function that may be due to reactive oxygen species. Conflicting evidence suggests that administration of antioxidants prevents CIN.

METHODS

We assessed the efficacy of allopurinol in preventing CIN. We prospectively randomized 159 patients with a serum creatinine concentration >1.1mg/dL undergoing cardiac catheterization/interventions to receive allopurinol (300 mg, p.o.) 24h before administration of radiocontrast agent and hydration (1mg/kg/hN/saline for 12h pre- and post-contrast, n=79), or hydration alone (1mg/kg/hN/saline for 12h pre- and post-contrast, n=80).

RESULTS

CIN occurred in 6 of 80 patients (7.5%) in the control group and no subjects in the allopurinol group (p=0.013). In the allopurinol group, median serum creatinine concentration decreased significantly from 1.43 mg/dL [1.1-4.15 mg/dL] to 1.35 mg/dL [0.7-4.15 mg/dl] at 48 h and to 1.27 mg/dL [0.66-4.37 mg/dL] at 4 days after radiocontrast administration (p<0.0001 and p<0.0001 compared with baseline, respectively). In the control group, median serum creatinine concentration decreased non-significantly from 1.48 mg/dL [1.1-2.96 mg/dL] to 1.43 mg/dL [0.73-3.02 mg/dL] and to 1.45 mg/dL [0.86-3.71 mg/dL] (p=0.045 and p=0.57, respectively) 48 h and 4 days after radiocontrast administration.

CONCLUSIONS

Prophylactic oral administration of allopurinol, along with hydration, may protect against CIN in high-risk patients undergoing coronary procedures.

Effect of theophylline on prevention of contrast-induced acute kidney injury: a meta-analysis of randomized controlled trials

BACKGROUND

Whether treatment with adenosine receptor antagonists such as theophylline can prevent contrast-induced acute kidney injury (AKI) remains controversial.

STUDY DESIGN

We conducted a meta-analysis of randomized controlled trials using MEDLINE (1966 to July 2011), EMBASE (1980 to July 2011), Web of Science (1986 to July 2011), and the Cochrane Central Register of Controlled Trials (1996 to July 2011), without language restriction.

SETTING & POPULATION

Patients undergoing contrast procedures.

SELECTION CRITERIA FOR STUDIES

Randomized controlled trials assessing adenosine antagonists versus control for prevention of contrast-induced AKI.

INTERVENTION

Adenosine antagonists with or without N-acetylcysteine versus control with or without N-acetylcysteine.

OUTCOMES

Contrast-induced AKI, change in serum creatinine level, requirement of dialysis, and in-hospital mortality.

RESULTS

16 trials (1,412 participants) were included. Theophylline significantly decreased the risk of contrast-induced AKI (13 trials, 1,222 patients; risk ratio, 0.48; 95% CI, 0.26-0.89; P = 0.02; I(2) = 45%) and had a protective effect on the absolute change in serum creatinine concentration (13 trials, 1,170 patients; standardized mean difference, -0.31 mg/dL; 95% CI, -0.50 to -0.11; P = 0.002; I(2) = 60%). Meta-regression showed a significant relation between the relative risk of contrast nephropathy and baseline serum creatinine level or Jadad score. No clear effects of treatment on risk of dialysis and in-hospital mortality were identified.

LIMITATIONS

Power to assess clinical end points was limited.

CONCLUSIONS

Theophylline treatment significantly reduced the incidence of contrast-induced AKI and had a modest improvement on kidney function after contrast exposure in the general population. However, beneficial effects of theophylline were not observed in patients with high baseline creatinine values (serum creatinine ≥1.5 mg/dL). In addition, the long-term effect of this agent on more clinically important outcomes was not established. Future large-scale high-quality multicenter trials in participants with different underlying risks of contrast-induced AKI and that incorporate the evaluation of clinically relevant outcomes are required.

Contrast induced nephropathy in urology

Intravenous contrast agents have a distinct role in urological imaging: to study precise anatomical delineation, vascularity, and to assess the function of the renal unit. Contrast induced nephropathy (CIN) is a known adverse effect of intravenous contrast administration. The literature on incidence, pathophysiology, clinical features, and current preventive strategies available for CIN relevant to urologists was reviewed. A search of the PubMed database was done using the keywords nephropathy and media, prevention and control or prevention Contrast media (explode), all adverse effects, and kidney diseases (explode). An online search of the EMBASE database for the time ranging from 1977 to February 2009 was performed using the keywords ionic contrast medium, adverse drug reaction, major or controlled clinical study, human, nephrotoxicity, and kidney disease. Current publications and data most relevant to urologists were examined. CIN was the third most common cause of hospital-acquired renal failure. The incidence is less common with intravenous contrast administration as compared with intra-arterial administration. The pathogenesis of contrast mediated nephropathy is due to a combination of toxic injury to renal tubules and medullary ischemic injury mediated by reactive oxygen species. CIN most commonly manifests as a nonoliguric and asymptomatic transient decline in renal function. Patients who developed CIN were found to have increased mortality, longer hospital stay, and complicated clinical course. An overview of risk factors and risk prediction score for prognostication of CIN are elaborated. Preventive strategies including choice of contrast agents, maximum tolerated dose, role of hydration, hydration regime, etc. are discussed. The role of N- acetyl cysteine, Theophylline, Fenoldapam, Endothelin receptor antagonists, iloprost, atrial natriuretic peptide, and newer therapies such as targeted renal therapy (TRT) are discussed. A working algorithm based on current evidence is proposed. No current treatment can reverse or ameliorate CIN once it occurs, but prophylaxis is possible.

How to reduce the incidence of contrast induced acute kidney injury after cardiac invasive procedures, a review and practical recommendations

BACKGROUND

Contrast induced acute kidney injury is an important complication after cardiac (invasive) procedures and is associated with substantial morbidity and mortality. The aim of the current article is to provide a comprehensive overview of the current knowledge regarding contrast induced acute kidney injury.

METHODS

Current literature was reviewed and relevant articles were selected. Articles were identified through MEDLINE and Pubmed selecting articles, limited between 1980 and 2010.

RESULTS

The pathophysiological process resulting in contrast induced acute kidney injury is not completely understood, nevertheless several mechanisms involved have been proposed. However, the risk factors for contrast induced acute kidney injury and its timing are well known, making it amenable for preventive strategies. In the past decade various preventive strategies have been investigated with different results.

CONCLUSIONS

Currently, only adequate hydration, with saline, is uniformly accepted as a beneficial prophylactic strategy. Furthermore promising results have also been reported for several other prophylactic strategies. These results, however, need to be confirmed in future trials.

Renal nerves in the maintenance of hypertension: a potential therapeutic target

Renal sympathetic efferent and afferent nerves, which lie within and immediately adjacent to the wall of the renal arteries, contribute to the maintenance of hypertension. Because the causative factors of hypertension change over time, denervation of both efferent and afferent renal nerves should result in long-term attenuation of hypertension. The importance of the renal nerves in hypertensive patients can now be defined with the novel development of percutaneous, minimally invasive renal denervation from within the renal artery using radiofrequency energy as a therapeutic strategy. Studies thus far show that catheter-based renal denervation in patients with resistant essential hypertension lowers systolic blood pressure 27 mm Hg by 12 months, with the estimated glomerular filtration rate remaining stable. The decrease in arterial pressure after renal denervation is associated with decreased peripheral sympathetic nervous system activity, suggesting that the kidney is a source of significant central sympathetic outflow via afferent renal nerve activity.

Methylxanthines and the kidney

This chapter describes the effects of the natural methylxanthines caffeine and theophylline on kidney function. Theophylline in particular was used traditionally to increase urine out put until more potent diuretics became available in the middle of the last century. The mildly diuretic actions of both methylxanthines are mainly the result of inhibition of tubular fluid reabsorption along the renal proximal tubule. Based upon the use of specific adenosine receptor antagonists and the observation of a complete loss of diuresis in mice with targeted deletion of the A1AR gene, transport inhibition by methylxanthines is mediated mainly by antagonism of adenosine A1 receptors (A1AR) in the proximal tubule. Methylxanthines are weak renal vasodilators, and they act as competitive antagonists against adenosine-induced preglomerular vasoconstriction. Caffeine and theophylline stimulate the secretion of renin by inhibition of adenosine receptors and removal of the general inhibitory brake function of endogenous adenosine. Since enhanced intrarenal adenosine levels lead to reduced glomerular filtration rate in several pathological conditions theophylline has been tested for its therapeutic potential in the renal impairment following administration of nephrotoxic substances such as radiocontrast media, cisplatin, calcineurin inhibitors or following ischemia-reperfusion injury. In experimental animals functional improvements have been observed in all of these conditions, but available clinical data in humans are insufficient to affirm a definite therapeutic efficacy of methylxanthines in the prevention of nephrotoxic or postischemic renal injury.

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 renal sympathetic nerves in hypertension: has percutaneous renal denervation refocused attention on their clinical significance?

Renal sympathetic efferent and afferent nerves, which lie within and immediately adjacent to the wall of the renal artery, contribute to the pathogenesis of hypertension. Because the causative factors of hypertension change over time, denervation of both efferent and afferent nerves should result in long-term attenuation of the hypertension. The importance of the renal nerves in patients with hypertension can now be defined with the novel development of percutaneous minimally invasive renal denervation from within the renal artery using radiofrequency energy as a therapeutic strategy. Studies thus far show that catheter-based renal denervation in patients with refractory hypertension lowers systolic blood pressure 27 mm Hg by 12 months with estimated glomerular filtration rate remaining stable. An attenuation of hypertension of this magnitude by catheter-based renal sympathetic denervation in combination with pharmacologic therapy is likely to be valuable in decreasing the risks of stroke, left ventricular hypertrophy, heart failure, and chronic renal failure.

Efficacy of N-acetylcysteine and aminophylline in preventing contrast-induced nephropathy

BACKGROUND

Contrast-induced nephropathy (CIN) is one of the important complications of coronary angiography (CAG) and percutaneous coronary intervention (PCI), especially in patients with chronic kidney disease (CKD). Prophylactic administration of N-acetylcysteine (NAC) and aminophylline has been reported to be effective in some trials, but the results still remain controversial. We investigated the efficacy of NAC or aminophylline in preventing CIN.

METHODS AND RESULTS

Forty-five consecutive patients undergoing CAG and/or PCI were randomly assigned to receive hydration and NAC (704 mg orally twice daily; NAC group, n=15), hydration and aminophylline (250 mg intraveneously 30 min before CAG and/or PCI; aminophylline group, n=15), or hydration alone (control group, n=15). We compared serum creatinine (SCr), creatinine clearance (Ccr), blood beta-2 microglobulin, and urinary beta-2 microglobulin levels at baseline and 48h after CAG and/or PCI. In the NAC group, SCr decreased from 1.00 + or - 0.36 to 0.67 + or - 0.16 mg/dl (p<0.01), and Ccr significantly increased from 62.4 + or - 15.6 to 80.4 + or - 8.39 ml/min (p<0.01). In the aminophylline group, SCr and Ccr were unchanged. In the control group, SCr significantly increased from 0.94 + or - 0.21 to 1.28 + or - 0.21 mg/dl (p<0.01), and Ccr significantly decreased from 63.7 + or - 16.1 to 46.1 + or - 10.6 ml/min (p<0.01) after CAG and/or PCI. In the NAC group, mean blood beta-2 microglobulin significantly decreased from 2.38 + or - 0.58 to 1.71 + or - 0.38 mg/dl (p<0.01), and in the aminophylline group, mean urinary beta-2 microglobulin concentration significantly decreased from 337 + or - 31.0 to 239 + or - 34 microg/ml (p<0.01).

CONCLUSIONS

These results suggest that both prophylactic NAC and aminophylline administration are effective in preventing CIN, but not with hydration alone. It appears that the two compounds work in different ways against CIN.

N-acetylcysteine versus N-acetylcysteine + theophylline for the prevention of contrast nephropathy

BACKGROUND

The use of N-acetylcysteine or theophylline in specific subgroups of patients has been suggested to reduce the incidence of contrast-induced nephropathy (CIN) in patients undergoing angiographic procedures. Our purpose was to compare the use of N-acetylcysteine versus N-acetylcysteine + theophylline for the prevention of CIN.

MATERIALS AND METHODS

We randomized 217 patients with estimated glomerular filtration rate (eGFR) (calculated by Modification of Diet in Renal Disease formula) between 30 and 60 mL min(-1) 1.73 m(-2) who were undergoing coronary angiography to three prophylactic treatment groups: Group 1: Intravenous hydration with isotonic saline (1 mL kg(-1) h(-1) for 12 h before and after contrast, n = 72). Group 2: Intravenous hydration with isotonic saline (1 mL kg(-1) h(-1) for 12 h before and after contrast)+ N-acetylcysteine (600 mg p.o. twice daily the preceding day and the day of angiography, n = 73). Group 3: Intravenous hydration with isotonic saline (1 mL kg(-1) h(-1) for 12 h before and after contrast)+ N-acetylcysteine + theophylline (600 mg N-acetylcysteine p.o. and 200 mg theophylline p.o. twice daily for the preceding day and the day of angiography, n = 72). The incidence of CIN (0.5 mg dL(-1) increase in serum creatinine from the baseline value 48 h after intravascular injection of contrast) was compared in three groups.

RESULTS

Of the 217 patients, 12 patients (5.5%) experienced CIN. Five patients (6.9%) in group 1, seven patients (9.6%) in group 2 and zero (0%) patients in group 3 experienced CIN (P < 0.033).

CONCLUSION

Among patients with eGFR between 30 and 60 mL min(-1) 1.73 m(-2) undergoing coronary angiography, oral administration of N-acetylcysteine + theophylline in addition to saline hydration has a beneficial effect in the prevention of CIN.

N-acetylcysteine to reduce renal failure after cardiac surgery: a systematic review and meta-analysis

PURPOSE

To assess the effect of N-acetylcysteine (NAC) on acute renal failure and important clinical outcomes after cardiac surgery.

METHODS

Two reviewers performed literature searches, using EMBASE and PubMed, of randomized controlled trials investigating the renoprotective effect of N-acetylcysteine in cardiac surgery. Treatment effects were calculated as relative risks (RR) with 95% confidence intervals (CI). Heterogeneity and publication bias were assessed using the I(2) test and funnel plots, respectively. Meta regression was performed to assess the effect of baseline renal function and the use of aprotinin on renal function.

RESULTS

Seven randomized controlled trials (RCTs) (n = 1000) were identified. No study could demonstrate, either independently or meta-analytically, an improvement in the postoperative increase in creatinine, mortality (RR 0.93, 95% CI 0.4 to 2.07), renal failure requiring renal replacement therapy (RR 1.01, 95% CI 0.49 to 2.12), myocardial infarction (RR 0.88, 95% CI 0.36 to 1.88), atrial fibrillation (RR 0.88, 95% CI 0.70 to 1.10), or stroke (RR 0.69, 95% CI 0.27 to 1.69). There was a small, though significant increase in postoperative blood loss among patients treated with NAC (weighted mean difference 119 mL 95% CI 51, 187). After meta regression neither increase in postoperative creatinine (r(2) = 0.33) nor renal replacement therapy (r(2) = 0.04) was associated with the baseline creatinine or with NAC dose (r(2) =0.04).

CONCLUSION

This analysis did not find that treatment with NAC was associated with clinical renal protection during cardiac surgery, or improvement in other clinical outcomes.