Contrast medium-induced nephrotoxicity: pathophysiology and prevention

Comparative study of renal protective effects of allopurinol and N-acetyl-cysteine on contrast induced nephropathy in patients undergoing cardiac catheterization

Objectives : To evaluate the difference in the renal protective effects of allopurinol and n-acetyl cysteine along with saline hydration in patients of contrast induced nephropathy (CIN) post cardiac interventions.

BACKGROUND

CIN remains a common complication of cardiac procedures. Radio contrast agents can cause a reduction in renal function that may be related to oxidative stress underlining various patho- physiologies. Conflicting evidence suggests that administration of allopurinol, a xanthine oxidase inhibitor can prevent CIN.

MATERIALS AND METHODS

This is a study of 500 patients undergoing angiography and coronary revascularisation in patients showing significant coronary block. The angiography positive patients (275) were prospectively randomised to different treatment protocol to study for their reno-protective effect. The patients received either of the three drugs saline hydration (SH, 1ml/kg/hr), n-acetylcysteine (SH+NAC, 600 mg bd) or Allopurinol (SH+ALLP, 300 mg/day) 12 hours before and after administration of radio contrast agent. Levels of serum creatinine and blood urea of the 275 patients recorded at 24 hour interval were noted post angioplasty over a course of 5 days in patients receiving either omnipaque (125) or visipaque (150) contrast media. All the 500 patients were also assessed for development of any kind of adverse drug effects/reactions with the two contrast media.

RESULTS

CIN occurred in 56 of 500 the patients (10.6%) who underwent angiography and 49 of 275 patients (17.8%) who underwent angioplasty. In the omnipaque group CIN occurred in 16/40, 8/40, nil/45 in patients receiving SH, NAC plus SH and SH plus ALLP respectively. In the visipaque group CIN occurred in 15/50, 10/50, nil/50 in the three treatments groups respectively. Allopurinol maintained a consistent fall in the serum creatinine & blood urea levels from the baseline values from the end of the 1(st) day (p < .01 & .001) in both the category. Visipaque proved to be better dye than omnipaque with less adverse drug effects/ reactions.

CONCLUSION

Prophylactic oral administration of allopurinol (300 mg/day) along with hydration is better than n-acetylcysteine and saline hydration alone for protection against CIN in patients undergoing coronary procedures.

[Perioperative acute kidney injury and failure]

Perioperative period is very likely to lead to acute renal failure because of anesthesia (general or perimedullary) and/or surgery which can cause acute kidney injury. Characterization of acute renal failure is based on serum creatinine level which is imprecise during and following surgery. Studies are based on various definitions of acute renal failure with different thresholds which skewed their comparisons. The RIFLE classification (risk, injury, failure, loss, end stage kidney disease) allows clinicians to distinguish in a similar manner between different stages of acute kidney injury rather than using a unique definition of acute renal failure. Acute renal failure during the perioperative period can mainly be explained by iatrogenic, hemodynamic or surgical causes and can result in an increased morbi-mortality. Prevention of this complication requires hemodynamic optimization (venous return, cardiac output, vascular resistance), discontinuation of nephrotoxic drugs but also knowledge of the different steps of the surgery to avoid further degradation of renal perfusion. Diuretics do not prevent acute renal failure and may even push it forward especially during the perioperative period when venous retourn is already reduced. Edema or weight gain following surgery are not correlated with the vascular compartment volume, much less with renal perfusion. Treatment of perioperative acute renal failure is similar to other acute renal failure. Renal replacement therapy must be mastered to prevent any additional risk of hemodynamic instability or hydro-electrolytic imbalance.

Evaluating and managing neonatal acute renal failure in a resource-poor setting

Acute renal failure (ARF) is encountered in neonatal care where it may be associated with significant morbidities. Pre-renal failure, which is due to impaired renal tissue perfusion, is the commonest type of ARF. It is amenable to treatment with excellent prognosis following prompt diagnosis and timely institution of appropriate intervention. Unfortunately, ARF in the newborn is usually asymptomatic and it is only suspected when a newborn infant has not been observed to pass urine over several hours or when serum Creatinine is observed to be elevated or rising. In resource-poor settings, it is often difficult to conduct detailed evaluation of suspected cases of newborn ARF due to lack of appropriate equipments and infrastructure. Similarly, therapeutic facilities are sparse and there is heavy reliance on conservative management of cases. Such difficulties encountered in the evaluation and management of newborns with ARF in most parts of the developing world, like Nigeria, where diagnostic and therapeutic facilities are limited are highlighted.

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine and its analogues, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes that included renal failure and mortality as well as changes in renal function tests, such as urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1966 to June, 2007), and EMBASE (1988 to June, 2007); and handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 53 studies for inclusion in this review. As well as data analysis from all the studies, we performed subgroup analysis for type of intervention, type of surgical procedure, and pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high and moderately good methodological quality.

MAIN RESULTS

The review included data from 53 studies, comprising a total of 2327 participants. Of these, 1293 received some form of treatment and 1034 acted as controls. The interventions mostly consisted of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, or selected hydration fluids. The results indicated that certain interventions showed minimal benefits. All the results suffered from significant heterogeneity. Hence we cannot draw conclusions about the effectiveness of these interventions in protecting patients' kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from the available literature to suggest that interventions during surgery can protect the kidneys from damage. There is a need for more studies with high methodological quality. One particular area for further study may be patients with pre-existing renal dysfunction undergoing surgery.

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials, which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes such as renal failure and mortality, as well as changes in the renal function tests, including urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2004), MEDLINE (1966 to 2004) and EMBASE (1988 to 2004) and hand searched six journals (British Journal of Anaesthesia; Anesthesia and Analgesia; Anesthesiology; Annals of Surgery; Journal of Thoracic and Cardiovascular Surgery and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adult population undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 37 studies for inclusion in this review. As well as analysis of the data from all the studies, we also performed subgroup analysis for type of interventions, types of surgical procedures and those with pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high methodological quality.

MAIN RESULTS

The review included data from 37 studies, comprising a total of 1227 patients. Of these, 658 received some form of treatment and 569 acted as controls. The interventions were mostly employing different pharmaceutical agents such as dopamine, diuretics, calcium channel blockers. ACE inhibitors or selected hydration fluids. The results indicated that certain interventions showed some benefits, but all the results suffered from significant heterogeneity. Hence we can draw no conclusions about the effectiveness of these interventions in protecting the kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from available literature to suggest that interventions during surgery can protect the kidneys from damage. However, there is a need for more studies of high methodological quality. One particular area for further studies may be on patients with pre-existing renal dysfunction undergoing surgery.

Short- and long-term renal outcomes of immediate prophylactic hemodialysis after cardiovascular catheterizations in patients with severe renal insufficiency

BACKGROUND

The short- and long-term effects of prophylactic hemodialysis (HD) immediately after cardiovascular catheterizations on renal function in patients with severe baseline renal insufficiency remain unknown though previous studies reported non-beneficial very-short-term effect in less severe patients.

METHODS AND RESULTS

Patients who had pre-procedural serum creatinine (Scr) between 2.5 and 5.5 mg/dl were retrospectively studied. Twenty of them (14 M/6 F, aged 69 +/- 2 years) had received prophylactic HD after radiocontrast exposure and constituted the HD group. Another 20 patients were case-matched to the baseline demographics of the HD group and served as the non-HD group. The baseline Scr were 3.9 +/- 0.2 and 3.5 +/-0.2 mg/dl, respectively (p = NS). Although the Scr at 3 months was significantly higher in the HD group (4.3 +/- 0.3 vs. 3.4 +/- 0.2 mg/dl, p = 0.02), the absolute and percentage increments from baseline to 3 months (0.4 +/- 0.2 vs. 0.0 +/- 0.2 mg/dl, p = NS, and 11 +/- 5% vs. 1 +/- 7%, p = NS, respectively) and 6 months (0.6 +/- 0.3 vs. 0.4 +/- 0.4 mg/dl, p = NS, and 18 +/- 8% vs. 8 +/- 10%, p = NS, respectively) were not statistically different. Patients who developed end-stage renal disease requiring permanent HD at 1 year were also similar in both groups (four vs. three, respectively, p = NS).

CONCLUSIONS

Our study confirmed that prophylactic HD immediately after contrast media administration in catheterizations failed to affect the short- and long-term renal and clinical outcomes even in patients with severe baseline renal insufficiency.

Delicate Percutaneous Renal Artery Stenting Minimizes Postoperative Renal Injury and Protects Kidney in Patients With Severe Atherosclerotic Renal Artery Stenosis and Impaired Renal Function

Percutaneous transluminal renal artery stenting (PTRAS) is associated with declining renal function in a non-negligible portion of patients and is inflicted by different mechanisms, including atheroembolism. This study investigated whether delicate PTRAS to reduce atheroembolism might minimize postoperative renal injury and better preserve renal function. Patients undergoing PTRAS performed by experienced interventional cardiologists, applying coronary intervention concepts, techniques, devices and delicacy principles whenever possible, were prospectively studied. A total of 34 patients (29 M/5 F) with impaired renal function (group A, creatinine 2.4 +/- 0.1 mg/dL) and another 20 patients (16 M/4 F) with normal serum creatinine (group B, baseline creatinine 1.2 +/- 0.0 mg/dL) were studied. PTRAS was successfully performed in all but one group A patient. During a 6-month follow-up, systolic and diastolic blood pressure (130 +/- 2 versus 148 +/- 4 mmHg, P = 0.001 and 70 +/- 2 versus 78 +/- 3 mmHg, P = 0.006) and serum creatinine (2.1 +/- 0.1 versus 2.4 +/- 0.1 mg/dL, P < 0.001) were all significantly lowered in group A patients. Using a 20% change cut-off value, renal function improved in eight (24%), remained unchanged in 24 patients (73%), and deteriorated in only one patient (3%). The corresponding alterations in blood pressure and renal function were insignificant in group B patients. Patients with bilateral involvement (eleven patients) also had significantly lowered serum creatinine on follow-up. In conclusion, delicately practiced PTRAS can reduce the rate of postprocedural renal deterioration in patients with impaired renal function, and should be adopted in every renal intervention.

Evidence-based Practice for the Use of N-acetylcysteine

The use of N-acetylcysteine has increased in the prevention of radiographic contrast induced nephrotoxicity. Many nurses need to be aware of the proper administration and action of this prophylactic agent. This article discusses the research behind the use of N-acetylcysteine and the protocol for administration to prevent radiographic contrast-induced nephrotoxicity.

Renal ultrasound

Renal US is one of several imaging modalities available to the EP in the evaluation of patients with acute urologic disorders. It offers excellent anatomic detail without exposure to radiation or contrast agents but is limited in its assessment of renal function. It is an important alternative to helical CT scanning for evaluating renal colic, especially in children and pregnant women. It has an important role in excluding bilateral renal obstruction as the cause of acute renal failure. It is likely that Doppler renal US also will take on a prominent role in the evaluation of renal vascular disorders. It already has become the standard of care in the management of renal transplant patients. Bedside emergency renal US performed and interpreted by EPs with limited training and experience is increasing in use and gaining acceptance. At present, the primary role of renal US is to identify hydronephrosis in patients with renal colic or acute renal failure but, in the future, its role likely will expand as technology advances and its use increases. In many patients, bedside renal US may obviate the need for further diagnostic workup and speed the diagnosis and treatment of an emergency patient.

N-acetylcysteine for radiocontrast-induced nephropathy: Potential role in the emergency department?

Objective:

To systematically review the efficacy and safety of N-acetylcysteine (NAC) for the prevention of radiocontrast-induced nephropathy (RIN), and to discuss its potential role in the emergency department.

Methodology:

We conducted a search of MEDLINE (from 1966 to December 2003), PubMed (1966 to December 2003) and EMBASE (1988 to December 2003) for English-language, prospective, randomized, controlled trials in humans using the search terms N-acetylcysteine, acetylcysteine, radiopharmaceuticals, contrast media, and kidney failure (acute).

Results:

Five trials support and 4 trials refute the hypothesis that NAC helps prevent RIN. In 7 of 9 trials, oral NAC was administered twice daily for 2 days, on the day before and on the day of the radiocontrast study — a regime not feasible for emergent situations. More recent trials suggest that adequate hydration and lower volumes of radiocontrast, rather than NAC, are more effective ways to prevent RIN.

Conclusion:

Although further study may be indicated, current evidence does not suggest that NAC has a role in the emergency prevention of RIN.

Fenoldopam andN-acetylcysteine for the Prevention of Radiographic Contrast Material-Induced Nephropathy: A Review

Radiographic contrast material-induced nephropathy (RCIN) is the third most common cause of hospital-acquired renal insufficiency and has been associated with an increase in patient mortality. Many strategies to prevent RCIN have been explored unsuccessfully. The standard of care remains hydration with 0.45% sodium chloride before and after administration of contrast material. Recently, N-acetylcysteine and fenoldopam have been studied to determine their efficacy in preventing RCIN. Of seven prospective studies using various dosing regimens of N-acetylcysteine, four revealed beneficial results. Although some discrepancies exist, the data strongly suggest that N-acetylcysteine has a role in patients at risk for the development of RCIN. The data for fenoldopam are more limited, with only one retrospective study showing benefit. Additional prospective data are required to determine if fenoldopam has a role in the prevention of RCIN.

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

RATIONALE AND OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Nephrotoxic effects in high-risk patients undergoing angiography

BACKGROUND

The use of iodinated contrast medium can result in nephropathy. Whether iso-osmolar contrast medium is less nephrotoxic than low-osmolar contrast medium in high-risk patients is uncertain.

METHODS

We conducted a randomized, double-blind, prospective, multicenter study comparing the nephrotoxic effects of an iso-osmolar, dimeric, nonionic contrast medium, iodixanol, with those of a low-osmolar, nonionic, monomeric contrast medium, iohexol. The study involved 129 patients with diabetes with serum creatinine concentrations of 1.5 to 3.5 mg per deciliter who underwent coronary or aortofemoral angiography. The primary end point was the peak increase from base line in the creatinine concentration during the three days after angiography. Other end points were an increase in the creatinine concentration of 0.5 mg per deciliter or more, an increase of 1.0 mg per deciliter or more, and a change in the creatinine concentration from day 0 to day 7.

RESULTS

The creatinine concentration increased significantly less in patients who received iodixanol. From day 0 to day 3, the mean peak increase in creatinine was 0.13 mg per deciliter in the iodixanol group and 0.55 mg per deciliter in the iohexol group (P=0.001; the increase with iodixanol minus the increase with iohexol, -0.42 mg per deciliter [95 percent confidence interval, -0.73 to -0.22]). Two of the 64 patients in the iodixanol group (3 percent) had an increase in the creatinine concentration of 0.5 mg per deciliter or more, as compared with 17 of the 65 patients in the iohexol group (26 percent) (P=0.002; odds ratio for such an increase in the iodixanol group, 0.09 [95 percent confidence interval, 0.02 to 0.41]). No patient receiving iodixanol had an increase of 1.0 mg per deciliter or more, but 10 patients in the iohexol group (15 percent) did. The mean change in the creatinine concentration from day 0 to day 7 was 0.07 mg per deciliter in the iodixanol group and 0.24 mg per deciliter in the iohexol group (P=0.003; value in the iodixanol group minus the value in the iohexol group, -0.17 mg per deciliter [95 percent confidence interval, -0.34 to -0.07]).

CONCLUSIONS

Nephropathy induced by contrast medium may be less likely to develop in high-risk patients when iodixanol is used rather than a low-osmolar, nonionic contrast medium.

Acute renal failure in hospitalized patients: part II

BACKGROUND

Acute renal failure (ARF) is a common condition in hospitalized patients. Research has been unable to identify the optimal target for therapeutic intervention; hence, effective prevention of and/or treatment for ARF remain elusive.

OBJECTIVE

To examine the usefulness of current and potential pharmacologic treatments in seriously ill, hospitalized patients.

DATA SOURCES

A MEDLINE search (1996-June 2002) was conducted using the search terms kidney (drug effects) and acute kidney failure (drug therapy). Bibliographies of selected articles were also examined to include all relevant investigations.

STUDY SELECTION AND DATA EXTRACTION

Review articles, meta-analyses, and clinical trials describing prevention of and treatment for hospital-acquired ARF were identified. Results from prospective, controlled trials were given priority when available.

CONCLUSIONS

Appropriate management of ARF includes prospective identification of at-risk patients, fluid administration, and optimal hemodynamic support. Drug treatments, including low-dose dopamine and diuretics, have demonstrated extremely limited benefits and have not been shown to improve patient outcome. Experimental agents influence cellular processes of renal dysfunction and recovery; unfortunately, relatively few drugs show promise for the future.

Fenoldopam in the prevention of contrast media-induced acute renal failure

OBJECTIVE

To examine the role of fenoldopam in prevention of contrast media-induced acute renal failure (ARF).

DATA SOURCES

A literature search of MEDLINE (from 1966 to October 2000) was performed using the following title search terms: fenoldopam, contrast, and renal failure.

STUDY SELECTION

English-language human studies, abstracts, and pertinent animal data were reviewed.

DATA SYNTHESIS

Small trials using animals with artificially induced ARF receiving fenoldopam demonstrated improvement in renal function. Preliminary trials in healthy humans have also demonstrated similar results using doses not affecting systemic blood pressure.

CONCLUSIONS

Fenoldopam may have a role in the management of ARF induced by contrast dye. However, due to the lack of a large-scale study it cannot be routinely recommended.