Acetylcysteine for prevention of contrast nephropathy: meta-analysis

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.

Alpha-lipoic acid for the prevention of contrast-induced nephropathy in patients undergoing coronary angiography: the ALIVE study - a prospective randomized trial

OBJECTIVES

α-Lipoic acid (ALA) is widely used for diabetic neuropathy due to its antioxidant properties. We evaluated its potential for preventing contrast-induced nephropathy (CIN).

METHODS

We conducted a prospective randomized controlled trial to evaluate the efficacy of ALA in CIN prevention. Two hundred and two patients with basal renal insufficiency who received elective coronary angiography were randomized to the ALA group [ALA treatment for 2 days (600 mg orally three times a day before and after coronary catheterization, n = 100)] or the control group (n = 102). The primary end point was the maximum increase in serum creatinine (sCr) and the secondary end point was the incidence of CIN defined as an increase in sCr of either ≥ 25% or ≥ 44.2 µmol/l.

RESULTS

Mean maximum increase in sCr was not different between the ALA and the control group (-1.32 ± 30.5 vs. -1.19 ± 30.1 µmol/l, respectively; p = 0.977). sCr did not significantly change from baseline (120.8 ± 69.8 vs. 122 ± 88.1 µmol/l) in the ALA group and the simple saline hydration group (108.2 ± 37.5 vs. 110 ± 49 µmol/l). There was a lower rate of CIN in the ALA group than in the control group, but the difference was not statistically significant (3.0 vs. 6.9%, respectively; p = 0.332).

CONCLUSION

ALA showed no benefit in CIN prevention.

[Incidence and clinical outcome of contrast-induced nephropathy in the elderly patients]

BACKGROUND

Aging is an established risk factor for contrast-induced nephropathy (CIN). However, little information is available on the incidence and clinical outcome of CIN for the elderly patients in Japan.

OBJECTIVES

We determined the incidence and clinical outcome of CIN in the Japanese elderly patient.

METHODS

We studied 292 patients who had mild renal dysfunction (estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2)) at baseline and underwent coronary angiography. Patients were divided into two groups base on their age: the elderly group (age ≥ 75, n=108) and the control group (age<75, n=184). CIN was defined as a 25% increase in serum creatinine or an increase in serum creatinine by>0.5 mg/dl above the baseline value at or within 2 days post procedure.

RESULTS

Patients in the elderly group had a higher incidence of CIN (14%) than those in the control group (9%). In patients who developed CIN, there was no significant difference between the two groups in baseline GFR and GFR on days 1, 2, 7 and 30 after the procedure. However, the relative increase in GFR above baseline on day 7 (-4.0 ± 6.1 vs -8.3 ± 8.0 ml/min P=0.096) and day 30 (1.5 ± 9.4 vs -10.1 ± 9.6 ml/min P=0.0017) in the elderly group was higher than that in the control group. Furthermore, death occurred in 3 patients in the elderly group (20%) whereas no patient died in the control group (P=0.092).

CONCLUSION

Aging (age ≥ 75) is a risk factor for CIN in Japanese. CIN in the elderly patients may be associated with prolonged renal dysfunction and poor prognosis.

Prevention of contrast-induced AKI: a review of published trials and the design of the prevention of serious adverse events following angiography (PRESERVE) trial

Contrast-induced AKI (CI-AKI) is a common condition associated with serious, adverse outcomes. CI-AKI may be preventable because its risk factors are well characterized and the timing of renal insult is commonly known in advance. Intravenous (IV) fluids and N-acetylcysteine (NAC) are two of the most widely studied preventive measures for CI-AKI. Despite a multitude of clinical trials and meta-analyses, the most effective type of IV fluid (sodium bicarbonate versus sodium chloride) and the benefit of NAC remain unclear. Careful review of published trials of these interventions reveals design limitations that contributed to their inconclusive findings. Such design limitations include the enrollment of small numbers of patients, increasing the risk for type I and type II statistical errors; the use of surrogate primary endpoints defined by small increments in serum creatinine, which are associated with, but not necessarily causally related to serious, adverse, patient-centered outcomes; and the inclusion of low-risk patients with intact baseline kidney function, yielding low event rates and reduced generalizability to a higher-risk population. The Prevention of Serious Adverse Events following Angiography (PRESERVE) trial is a randomized, double-blind, multicenter trial that will enroll 8680 high-risk patients undergoing coronary or noncoronary angiography to compare the effectiveness of IV isotonic sodium bicarbonate versus IV isotonic sodium chloride and oral NAC versus oral placebo for the prevention of serious, adverse outcomes associated with CI-AKI. This article discusses key methodological issues of past trials investigating IV fluids and NAC and how they informed the design of the PRESERVE trial.

Serum neutrophil gelatinase-associated lipocalin and cystatin C are early biomarkers of contrast-induced nephropathy after coronary angiography in patients with chronic kidney disease

We had previously reported on serum neutrophil gelatinase-associated lipocalin (NGAL) as an earlier biomarker of contrast-induced nephropathy (CIN) than serum creatinine (SCr) in 100 patients with chronic kidney disease undergoing coronary angiography.(1) We then compared serum NGAL to serum cystatin C (CysC) in the same group of patients. The SCr, estimated glomerular filtration rate, serum NGAL, and serum CysC were measured at baseline and various time points as appropriate postprocedure. The frequency of CIN was 11% (n = 11). Serum NGAL increased ≥25% from baseline at 24 hours in 7 patients with CIN (P = .04). Serum CysC increased ≥25% from baseline at 24 hours in 4 patients with CIN (P = .008). Changes in serum NGAL and serum CysC from baseline at 24 hours (▵ values) could diagnose CIN 24 hours earlier than SCr with serum NGAL showing a superior performance.

Dopamine-1 Receptor Agonist: Renal Effects and Its Potential Role in the Management of Radiocontrast-Induced Nephropathy

Radiocontrast-induced nephropathy remains the third leading cause of hospital-acquired acute renal failure. Once established, this syndrome is associated with increased morbidity and mortality as well as increased health care costs. Recently, studies have been initiated to evaluate the potential of a selective dopamine-1 receptor agonist (fenoldopam) in ameliorating radiocontrast-induced renal failure. Selective dopamine-1 receptor agonists exhibit many desirable renal effects that support their use for the prophylaxis of radiocontrast-induced nephropathy, including decreases in renal vascular resistance and increases in renal blood flow, glomerular filtration, and sodium and water excretion. Several reports have documented a beneficial effect of fenoldopam administration in attenuating radiocontrast-induced nephropathy. In contrast, a recent multicenter, randomized study did not demonstrate a renoprotective effect of fenoldopam against radiocontrast-induced nephropathy. The presence of multiple confounders, however, precludes a definitive conclusion regarding the ability of fenoldopam to protect against radiocontrast-induced nephropathy. Additional studies are needed to properly evaluate the role of fenoldopam in radiocontrast-induced nephropathy prophylaxis.

Neutrophil Gelatinase-Associated Lipocalin as an Early Marker of Contrast-Induced Nephropathy After Coronary Angiography

We investigated whether serum neutrophil gelatinase-associated lipocalin (NGAL) was an early predictive biomarker of contrast-induced nephropathy (CIN) in patients with chronic kidney disease (n = 100) undergoing coronary catheterization. Serum creatinine (SCr) levels were measured at baseline, 24 hours, and 48 hours post procedure. Serum NGAL was measured preprocedure, 4 hours, and 24 hours post procedure. The frequency of CIN was 11%. In patients with CIN, SCr achieved significance only at 48 hours ( P = .006), whereas serum NGAL increased ≥25% from baseline at 24 hours in 7 of 11 patients with CIN ( P = .04) but did not change in the other 4. However, serum NGAL also rose ≥25% in 12 of 89 non-CIN patients. This subgroup could have had “incipient CIN.” Serum NGAL delta value at baseline, 24 hours was superior to SCr for early diagnosis of CIN. In conclusion, serum NGAL is an early predictive biomarker for CIN.

A human serum albumin-thioredoxin fusion protein prevents experimental contrast-induced nephropathy

Contrast-induced nephropathy (CIN), caused by a combination of the direct tubular toxicity of contrast media, a reduction in medullary blood flow, and the generation of reactive oxygen species, is a serious clinical problem. A need exists for effective strategies for its prevention. Thioredoxin-1 (Trx) is a low-molecular-weight endogenous redox-active protein with a short half-life in the blood due to renal excretion. We produced a long-acting form of Trx as a recombinant human albumin-Trx fusion protein (HSA-Trx) and examined its effectiveness in preventing renal injury in a rat model of ioversol-induced CIN. Compared with saline, a mixture of HSA and Trx, or Trx alone, intravenous HSA-Trx pretreatment significantly attenuated elevations in serum creatinine, blood urea nitrogen, and urinary N-acetyl-β-D-glucosaminidase along with the decrease in creatinine clearance. HSA-Trx also caused a substantial reduction in the histological features of renal tubular injuries and in the number of apoptosis-positive tubular cells. Changes in the markers 8-hydroxy deoxyguanosine and malondialdehyde indicated that HSA-Trx significantly suppressed renal oxidative stress. In HK-2 cells, HSA-Trx decreased the level of reactive oxygen species induced by hydrogen peroxide, and subsequently improved cell viability. Thus, our results suggest that due to its long-acting properties, HSA-Trx has the potential to effectively prevent CIN.

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.

The Role of N--Acetylcysteine in the Prevention of Contrast-Induced Nephropathy in Patients Undergoing Peripheral Angiography

Contrast-induced nephropathy (CIN) is a leading cause of hospital-acquired acute kidney injury (AKI). N-acetylcysteine (NAC) was proposed as an effective preventative measure. As data in relation to the use of NAC for the prevention of CIN in peripheral angiography are lacking, a systematic review and meta-analysis were undertaken. A comprehensive search for the published and unpublished data was performed. Data were extracted from the eligible studies. Pooled odds ratios (ORs) were used to calculate the effect of NAC on CIN incidence. Pooled effect size estimates were used to calculate the effect of NAC on serum creatinine (SCr) postcontrast. Our results showed that NAC did not reduce CIN incidence (pooled OR 1.05; 95% confidence interval [CI] 0.38-2.88; P = .92) or the mean SCr levels (pooled weighted mean difference, 4.38; 95% CI 10.4-1.65; P = .15). In conclusion, insufficient evidence exists to recommend NAC for the prevention of CIN in patients undergoing peripheral angiography.

Protective effect of N-acetylcysteine on kidney as a remote organ after skeletal muscle ischemia-reperfusion

PURPOSE: To investigate whether N-acetylcysteine has a protective effect against renal injury as a remote organ after skeletal muscle ischemia-reperfusion in rats. METHODS: Twenty Wistar male rats were divided randomly into two experimental groups: group ischemia-reperfusion (group I) and group ischemia-reperfusion + N-acetylcysteine (group II). After ketamine and xylazine anesthesia, femoral artery was exposed. All animals were undergone 2h of ischemia by occlusion femoral artery and 24h of reperfusion. Rats that were treated with N-acetylcysteine given IV at a dose of 150 mg/kg-¹, immediately before reperfusion. After 24h of reperfusion, the blood samples were collected and submitted for evaluation of plasmatic urea, creatinine values and then rats were euthanized and left kidney harvested for histopathological analysis under light microscopy. RESULTS: The urea (35±7.84 mg.dL-1), creatinine (1.46±0.47 mg.dL-1) values were significantly lower in group II (P=0.000). Renal histopathologic study in group I showed extensive distal and proximal tubular cells necrosis and sloughing of epithelial cells into the tubular lumen, cast formation in tubule and glomerul, glomerul fibrosis and hemorrhage. Histopathologically, there was a significant difference (p=0.037) between two groups. CONCLUSION: The N-acetylcysteine was able to decrease renal injury induced by skeletal muscle ischemia reperfusion in rats.

Prevention of contrast-induced nephropathy: A randomized controlled trial of sodium bicarbonate and N-acetylcysteine

BACKGROUND

Contrast-induced nephropathy (CIN) continues to be a common cause of acute renal failure in high-risk patients undergoing radiocontrast studies. However, there is still a lack of consensus regarding the most effective measures to prevent CIN.

METHODS

ONE HUNDRED EIGHTEEN PATIENTS WITH DIABETES MELLITUS AND/OR RENAL INSUFFICIENCY, SCHEDULED FOR CORONARY ANGIOGRAPHY OR INTERVENTION, WERE RANDOMLY ASSIGNED TO ONE OF FOUR TREATMENT GROUPS: intravenous (IV) 0.9% NaCl alone, IV 0.9% NaCl plus N-acetylcysteine (NAC), IV 0.9% sodium bicarbonate (NaHCO(3)) alone or IV 0.9% NaHCO(3) plus NAC. All patients received IV hydration as a preprocedure bolus and as maintenance. Iso-osmolar contrast was used in all patients. CIN was defined as an increase of greater than 25% in the serum creatinine concentration from baseline to 72 h.

RESULTS

The overall incidence of CIN was 6%. There was no statistically significant difference in the incidence of CIN among the groups. There was a CIN incidence of 7% in the NaCl only group, 5% in the NaCl/NAC group, 11% in the NaHCO(3) only group and 4% in the NaHCO(3)/NAC group (P=0.86). The maximum increase in serum creatinine was 14.14±12.38 μmol/L in the NaHCO(3) group, 10.60±29.14 μmol/L in the NaCl only group, 9.72±13.26 μmol/L in the NaCl/NAC group and 0.177±15.91 μmol/L for the NaHCO(3)/NAC group (P=0.0792).

CONCLUSION

CIN in high-risk patients may be effectively minimized solely through the use of an aggressive hydration protocol and an iso-osmolar contrast agent. The addition of NaHCO(3) and/or NAC did not have an effect on the incidence of CIN.

Acute kidney injury and the critically ill patient

Acute kidney injury (AKI) is a serious complication for the critically ill patient. The term has been increasingly adopted over recent years as efforts have been made to capture and better define mild to severe renal dysfunction. Persistent AKI can lead to the subsequent development of renal failure recognized as an important determinant of morbidity and mortality in the critically ill patient. This article explores the clinical implications of AKI for the critically ill patient and how this can have a profound influence on the principal presenting disease and expected outcome.

Peri-operative renal protection: The strategies revisited

Postoperative acute renal failure (ARF) is a serious complication which can result in a prolonged hospital stay and a high mortality and morbidity. Underlying renal disease, cardiac diseases, nephrotoxin exposure and renal hypoperfusion are the possible predisposing risk factors which can create a high probability for the development of ARF. The incidence of ARF is highest after major vascular, cardiac and high-risk thoraco-abdominal surgery. Among the various renal protection strategies, adequate peri-operative volume expansion and avoidance of hypovolemia is the most accepted and practiced strategy. Numerous bio-markers of renal injury are used to estimate the presence and extent of renal insult and various new are currently under trial. Traditional pharmacological interventions like dopamine, diuretics and calcium antagonists are not currently the first line of reno-protective agents. The new non-pharmacological and pharmacological methods may improve outcome in renal transplantation, contrast-induced nephropathy and in various other settings of ARF. The current review is an attempt to refresh the knowledge and put forth the various renal protection strategies during the peri-operative period.

Preventing radiocontrast-induced nephropathy in chronic kidney disease patients undergoing coronary angiography

Radiocontrast-induced nephropathy (RCIN) is an acute and severe complication after coronary angiography, particularly for patients with pre-existing chronic kidney disease (CKD). It has been associated with both short- and long-term adverse outcomes, including the need for renal replacement therapy, increased length of hospital stay, major cardiac adverse events, and mortality. RCIN is generally defined as an increase in serum creatinine concentration of 0.5 mg/dL or 25% above baseline within 48 h after contrast administration. There is no effective therapy once injury has occurred, therefore, prevention is the cornerstone for all patients at risk for acute kidney injury (AKI). There is a small but growing body of evidence that prevention of AKI is associated with a reduction in later adverse outcomes. The optimal strategy for preventing RCIN has not yet been established. This review discusses the principal risk factors for RCIN, evaluates and summarizes the evidence for RCIN prophylaxis, and proposes recommendations for preventing RCIN in CKD patients undergoing coronary angiography.

Prevention of renal ischemia/reperfusion injury in rats using acetylcysteine after anesthesia with isoflurane

PURPOSE: To evaluate the effect of N-acetylcysteine, as a renoprotective agent, when administered early after anesthesia induction, against ischemia/reperfusion injury in rats anesthetized with isoflurane. METHODS: Eighteen male Wistar rats weighing > 300g were anesthetized with isoflurane. The internal jugular vein and the left carotid artery were dissected and cannulated. The animals were randomly divided into GAcetyl, receiving intravenous N-acetylcysteine, 300mg/kg, and GIsot, isotonic saline. After 30 minutes, right nephrectomy was performed and the left renal artery was clamped during 45 minutes. The animals were sacrificed after 48 hours and blood samples were taken after anesthetic induction and upon sacrificing of the animals to evaluate blood creatinine. The kidneys were sent for histological analysis. RESULTS: The variation in serum creatinine was 2.33mg/dL ± 2.21 in GAcetyl and 4.38mg/dL ± 2.13 in GIsot (p=0.074). Two animals presented intense tubular necrosis in GAcetyl, compared to 5 in GIsot. Only GAcetyl presented animals free of tubular necrosis (two) and tubular degeneration (one). CONCLUSION: After renal ischemia/reperfusion, the rats which were given N-acetylcysteine presented less variation in serum creatinine and milder kidney injuries than the control group.

Sodium chloride vs. sodium bicarbonate for the prevention of contrast medium-induced nephropathy: a randomized controlled trial

AIMS

The most effective regimen for the prevention of contrast-induced nephropathy (CIN) remains uncertain. Our purpose was to compare two regimens of sodium bicarbonate with 24 h sodium chloride 0.9% infusion in the prevention of CIN.

METHODS AND RESULTS

We performed a prospective, randomized trial between March 2005 and December 2009, including 258 consecutive patients with renal insufficiency undergoing intravascular contrast procedures. Patients were randomized to receive intravenous volume supplementation with either (A) sodium chloride 0.9% 1 mL/kg/h for at least 12h prior and after the procedure or (B) sodium bicarbonate (166 mEq/L) 3 mL/kg for 1 h before and 1 mL/kg/h for 6 h after the procedure or (C) sodium bicarbonate (166 mEq/L) 3 mL/kg over 20 min before the procedure plus sodium bicarbonate orally (500 mg per 10 kg). The primary endpoint was the change in estimated glomerular filtration rate (eGFR) within 48 h after contrast. Secondary endpoints included the development of CIN. The maximum change in eGFR was significantly greater in Group B compared with Group A {mean difference -3.9 [95% confidence interval (CI), -6.8 to -1] mL/min/1.73 m2, P = 0.009} and similar between groups C and B [mean difference 1.3 (95% CI, -1.7-4.3) mL/min/1.73 m(2), P = 0.39]. The incidence of CIN was significantly lower in Group A (1%) vs. Group B (9%, P = 0.02) and similar between Groups B and C (10%, P = 0.9).

CONCLUSION

Volume supplementation with 24 h sodium chloride 0.9% is superior to sodium bicarbonate for the prevention of CIN. A short-term regimen with sodium bicarbonate is non-inferior to a 7 h regimen. ClinicalTrials.gov Identifier: NCT00130598.

Risks and complications of coronary angiography: a comprehensive review

Coronary angiography and heart catheterization are invaluable tests for the detection and quantification of coronary artery disease, identification of valvular and other structural abnormalities, and measurement of hemodynamic parameters. The risks and complications associated with these procedures relate to the patient’s concomitant conditions and to the skill and judgment of the operator. In this review, we examine in detail the major complications associated with invasive cardiac procedures and provide the reader with a comprehensive bibliography for advanced reading.

N-acetylcysteine for Prevention of Contrast-Induced Nephropathy: A Narrative Review

Contrast-induced nephropathy (CIN) affects in-hospital, short- and long-term morbidity and mortality. It also leads to prolonged hospital stay and increased medical cost. Given the potential clinical severity of CIN, there has been considerable interest in the development of preventative strategies to reduce the risk of contrast-induced renal deterioration in at-risk populations. A number of pharmacologic and mechanical preventive measures have been attempted, but no method other than adequate periprocedural hydration has been conclusively successful. Since its introduction in 2000, N-acetylcysteine (NAC) has been widely investigated, albeit with conflicting findings for its nephroprotection capability in patients receiving contrast media procedures. However, there is still virtually no definitive evidence of effectiveness of NAC. Although the exact mechanism responsible for the protective action of NAC from renal function deterioration remains unclear, the antioxidant and vasodilatory properties of NAC have been suggested as the main mechanisms. This review summarizes the current status of NAC as a potential agent to prevent renal functional deterioration and its limitations.

Prognostic value of renal dysfunction for the prediction of outcome versus results of computed tomographic coronary angiography

Chronic kidney disease (CKD) is associated with cardiovascular (CV) events caused by advanced atherosclerosis. Computed tomographic coronary angiography (CTA) can accurately diagnose coronary artery disease (CAD) and predict CV outcomes. The aim of the present study was to evaluate whether moderate CKD provides prognostic information for CV events in patients undergoing CTA. In total 885 patients with suspected CAD underwent CTA and were stratified to moderate CKD (85 patients) or no CKD (770 patients) based on a cut-off estimated glomerular filtration rate of 60 ml/min/1.73 m(2). After 896 days of follow-up, 42 patients developed CV events. Annualized CV event rates were 1.2% in patients with no CKD and no CAD, 2.5% in patients with moderate CKD alone, 2.5% in patients with obstructive CAD alone, and 3.7% in those with moderate CKD and obstructive CAD. Multivariate models demonstrated that moderate CKD (hazard ratio 2.39, confidence interval 1.09 to 5.21, p = 0.03) and obstructive CAD (hazard ratio 2.76, confidence interval 1.40 to 5.44, p <0.01) were independent predictors of CV events. Importantly, moderate CKD provided incremental prognostic information in addition to clinical characteristics and obstructive CAD (chi-square 49.4, p = 0.04). In conclusion, moderate CKD was associated with CV events and provided incremental prognostic information.

Improved renal recovery with postresuscitation N-acetylcysteine treatment in asphyxiated newborn pigs

Renal injury is one of the severe and common complications that occurs early in neonates with asphyxia, and reactive oxygen species have been implicated to play an important role on its pathogenesis. Improved renal recovery has been shown previously with N-acetyl-l-cysteine (NAC) in various acute kidney injuries. Using a subacute swine model of neonatal hypoxia-reoxygenation (H/R), we examined whether NAC can sustain its beneficial effect on renal recovery for 48 h. Newborn piglets were randomly assigned into a sham-operated group (without H/R, n = 6) and two H/R experimental groups (n = 8 each) with 2 h normocapnic alveolar hypoxia and 1 h 100% oxygen of reoxygenation followed by 21% oxygen for 47 h. Five minutes after reoxygenation, piglets received either normal saline (H/R control) or NAC (150-mg/kg bolus and 20 mg/kg per hour i.v. for 24 h) in a blinded, randomized fashion. All piglets were acidotic and in cardiogenic shock after hypoxia. Treating the piglets with NAC significantly increased both renal blood flow and oxygen delivery throughout the reoxygenation period. N-acetyl-l-cysteine treatment also improved the renal function with the attenuation of elevated urinary N-acetyl-β-d-glucosaminidase activity and plasma creatinine concentration observed in H/R controls (both P < 0.05). The tissue levels of lipid hydroperoxides and caspase 3 in the kidney of NAC-treated animals were significantly lower than those of H/R controls. Conclusively, postresuscitation administration of NAC elicits a prolonged beneficial effect in improving renal functional recovery and reducing oxidative stress in newborn piglets with H/R insults for 48 h.

Renal failure: emergency evaluation and management

Patients with altered renal function are frequently encountered in the emergency department (ED) and emergency physicians often play an important role in the evaluation and management of renal disease. Early recognition, diagnosis, prevention of further iatrogenic injury, and management of renal disease have important implications for long-term morbidity and mortality. This article reviews basic renal physiology, discusses the differential diagnosis and approach to therapy, as well as strategies to prevent further renal injury, for adult patients who present to the ED with renal injury or failure.

Contrast-induced nephropathy: what we know, what we think we know, and what we don't know

Contrast-induced nephropathy is a common but poorly understood problem. A large body of literature devoted to the subject is replete with contradictions and conflicting reports. The purpose of this article is to summarize our current understanding of the problem by reviewing some of the best studies done to date. Recommendations based on the current literature are also provided.

Contrast-induced nephropathy in interventional cardiology

Development of contrast-induced nephropathy (CIN), ie, a rise in serum creatinine by either ≥0.5 mg/dL or by ≥25% from baseline within the first 2-3 days after contrast administration, is strongly associated with both increased inhospital and late morbidity and mortality after invasive cardiac procedures. The prevention of CIN is critical if long-term outcomes are to be optimized after percutaneous coronary intervention. The prevalence of CIN in patients receiving contrast varies markedly (from <1% to 50%), depending on the presence of well characterized risk factors, the most important of which are baseline chronic renal insufficiency and diabetes mellitus. Other risk factors include advanced age, anemia, left ventricular dysfunction, dehydration, hypotension, renal transplant, low serum albumin, concomitant use of nephrotoxins, and the volume of contrast agent. The pathophysiology of CIN is likely to be multifactorial, including direct cytotoxicity, apoptosis, disturbances in intrarenal hemodynamics, and immune mechanisms. Few strategies have been shown to be effective to prevent CIN beyond hydration, the goal of which is to establish brisk diuresis prior to contrast administration, and to avoid hypotension. New strategies of controlled hydration and diuresis are promising. Studies are mixed on whether prophylactic oral N-acetylcysteine reduces the incidence of CIN, although its use is generally recommended, given its low cost and favorable side effect profile. Agents which have been shown to be ineffective or harmful, or for which data supporting routine use do not exist, include fenoldopam, theophylline, dopamine, calcium channel blockers, prostaglandin E(1), atrial natriuretic peptide, statins, and angiotensin-converting enzyme inhibitors.

[Contrast-induced nephropathy]

Contrast-induced nephropathy is a major complication resulting from percutaneous coronary interventional procedures characterized by acute or subacute deterioration of renal function due to exposure to iodinated contrast medium that is associated with increased morbidity and mortality. Promoting factors for the development of nephropathy have been widely described in literature as well as hydration and pharmacological measures to prevent its development; However, few of them have shown evidence level A so far, hence a major research front remains open, not only in the prevention but also in the treatment of this pathology. In this article we review epidemiological and pathophysiological aspects of this complication, and various preventive and therapeutic modalities currently available.

Contrast-induced acute kidney injury: short- and long-term implications

The intravascular administration of iodine-based contrast media remains a common cause of acute kidney injury and a leading cause of iatrogenic renal disease. Past research has elucidated the principal risk factors for contrast-induced acute kidney injury (CIAKI) and helped to establish the efficacy of various interventions for the prevention of this condition. The importance of preventing CIAKI has been underscored by a growing number of studies showing strong associations of CIAKI with serious adverse short- and long-term outcomes. However, it remains unclear whether these associations are causal. This is important because considerable health care resources are used to prevent CIAKI. If CIAKI is a marker, but not a mediator, of serious adverse downstream outcomes, more judicious and selective use of preventive care may be appropriate. Moreover, with an increasing number of studies reporting the underuse of coronary angiography in patients with acute coronary syndrome and underlying chronic kidney disease, presumably in part because of a fear of CIAKI, a clear understanding of whether this condition directly results in adverse downstream outcomes is essential. Careful inspection of past studies that investigated the association of CIAKI with adverse short- and long-term events sheds light on their strengths and weaknesses and provides insight into how future research may be better able to characterize the short- and long-term implications of this iatrogenic condition.

Impact of contrast-induced acute kidney injury definition on clinical outcomes

BACKGROUND

Contrast-induced acute kidney injury (CIAKI) is a frequent complication after infusion of contrast media in patients undergoing percutaneous coronary intervention. A wide range of CIAKI rates occurs after intervention between 3% and 30%, depending on the definition. The aim of this study was to identify which methodology was more effective at recognizing patients at high risk for in-hospital and out-of-hospital adverse events.

METHODS AND RESULTS

Serum creatinine increases, after contrast agent infusion, were evaluated in 755 consecutive and unselected patients. Incidences of CIAKI diagnosed by 2 common definitions varied from 6.9% (creatinine increase of ≥0.5 mg/dL, CIAKI-0.5) to 15.9% (creatinine increase of ≥25%, CIAKI-25%). Significant differences appeared between the 2 definitions of sensitivity to predict renal failure according to receiver operating characteristic curve analysis (98% for CIAKI-0.5 and 62% for CIAKI-25%), using a cutoff value of postprocedural glomerular filtration rate of 60 mL/min. Both definitions of CIAKI were related to composite adverse events, but CIAKI-0.5 showed a stronger predicting value (odds ratio 2.875 vs 1.802, P = .036). In multivariate linear regression, only CIAKI-0.5 was a predictive variable of death (odds ratio 3.174, 95% CI 1.368-7.361).

CONCLUSIONS

An increase in serum creatinine of ≥0.5 mg/dL is more sensitive because it recognizes more selectively those patients with a higher risk of mortality and morbidity. Serum creatinine increases of ≥25% overestimate CIAKI by including many patients without postprocedural relevant deterioration of renal function and affected by a lower risk of adverse events at follow-up.

Does N-acetylcysteine reduce the incidence of contrast-induced nephropathy and clinical events in patients undergoing primary angioplasty for acute myocardial infarction?

OBJECTIVES

We examined oral N-acetylcysteine effects on contrast-induced nephropathy (CIN) and clinical events in patients undergoing primary angioplasty for acute myocardial infarction.

BACKGROUND

Recent studies have reported that N-acetylcysteine reduces CIN and improves the clinical outcome in patients undergoing primary angioplasty. However, additional investigations are warranted to further support these findings.

METHODS

We randomly assigned 76 patients undergoing primary angioplasty into two groups: 38 patients were assigned to N-acetylcysteine (NAC, 705 mg orally administration before and 12, 24, 36 hours after primary angioplasty), and 38 patients to placebo. CIN was defined as an increase in the serum creatinine concentration of 25 percent or more from baseline value within the 72-hour period after primary angioplasty.

RESULTS

CIN occurred in 7 patients (9.2%). In the NAC group, the incidence of CIN tended to be lower than in the placebo group (NAC; 2/38; 5.3% vs. Placebo; 5/38; 13.2%, p=0.21). The composite endpoints such as death, acute renal failure requiring temporary renal replacement therapy, or need for mechanical ventilation did not occur in either group.

CONCLUSION

While N-acetylcysteine might have the possibility to reduce the incidence of contrast-induced nephropathy in patients undergoing primary angioplasty for acute myocardial infarction, the in-hospital mortality and morbidity were not significantly different between the two groups.

Evaluating the impact of MEDLINE filters on evidence retrieval: study protocol

Background

Rather than searching the entire MEDLINE database, clinicians can perform searches on a filtered set of articles where relevant information is more likely to be found. Members of our team previously developed two types of MEDLINE filters. The 'methods' filters help identify clinical research of high methodological merit. The 'content' filters help identify articles in the discipline of renal medicine. We will now test the utility of these filters for physician MEDLINE searching.

Hypothesis

When a physician searches MEDLINE, we hypothesize the use of filters will increase the number of relevant articles retrieved (increase 'recall,' also called sensitivity) and decrease the number of non-relevant articles retrieved (increase 'precision,' also called positive predictive value), compared to the performance of a physician's search unaided by filters.

Methods

We will survey a random sample of 100 nephrologists in Canada to obtain the MEDLINE search that they would first perform themselves for a focused clinical question. Each question we provide to a nephrologist will be based on the topic of a recently published, well-conducted systematic review. We will examine the performance of a physician's unaided MEDLINE search. We will then apply a total of eight filter combinations to the search (filters used in isolation or in combination). We will calculate the recall and precision of each search. The filter combinations that most improve on unaided physician searches will be identified and characterized.

Discussion

If these filters improve search performance, physicians will be able to search MEDLINE for renal evidence more effectively, in less time, and with less frustration. Additionally, our methodology can be used as a proof of concept for the evaluation of search filters in other disciplines.

Reactive oxygen species and the pathogenesis of radiocontrast-induced nephropathy

Experimental findings in vitro and in vivo illustrate enhanced hypoxia and the formation of reactive oxygen species (ROS) within the kidney following the administration of iodinated contrast media, which may play a role in the development of contrast media-induced nephropathy. Clinical studies indeed support this possibility, suggesting a protective effect of ROS scavenging or reduced ROS formation with the administration of N-acetyl cysteine and bicarbonate infusion, respectively. Furthermore, most risk factors, predisposing to contrast-induced nephropathy are prone to enhanced renal parenchymal hypoxia and ROS formation. In this review, the association of renal hypoxia and ROS-mediated injury is outlined. Generated during contrast-induced renal parenchymal hypoxia, ROS may exert direct tubular and vascular endothelial injury and might further intensify renal parenchymal hypoxia by virtue of endothelial dysfunction and dysregulation of tubular transport. Preventive strategies conceivably should include inhibition of ROS generation or ROS scavenging.