Contrast-Induced Nephropathy

Diagnostic and therapeutic angiographic procedures are increasingly performed. Many complex interventions are lengthy and require large dosages of contrast medium (CM). Radiological procedures such as coronary angiography require intravascular administra‐ tion of iodinated CM is becoming a great source of an iatrogenic disease known as con‐ trast-induced nephropathy (CIN). The pathogenesis of CIN is unclear. The proposed mechanisms are outer-medullary hypoxia due to decreased renal blood flow secondary to renal artery vasoconstriction. Tubular obstruction, apoptosis and oxidative damage, endo‐ thelial dysfunction, defective prostaglandin synthesis, and autonomic dysfunction are oth‐ er proposed mechanisms.


dney Related
isk Factors Pre-existing renal failure Preprocedural creatinine 2.0-2.9 mg/dl 7.37 (4.78-11.39)<0.0001 Preprocedural creatinine ≥ 3mg/d 12.82 (8.01-20.54)<0.0001 Diabetes mellitus-Diabetic nephropathy Contrast-Induced Nephropathy

Introduction

Diagnostic and therapeutic angiographic procedures are increasingly performed.Many complex interventions are lengthy and require large dosages of contrast medium (CM).Radiological procedures such as coronary angiography require intravascular administration of iodinated CM is becoming a great source of an iatrogenic disease known as contrast-induced nephropathy (CIN).The pathogenesis of CIN is unclear.The proposed mechanisms are outer-medullary hypoxia due to ecreased renal blood flow secondary to renal artery vasoconstriction.Tubular obstruction, apoptosis and oxidative damage, endothelial dysfunction, defective prostaglandin synthesis, and autonomic dysfunction are other proposed mechanisms.

Patients who develop CIN have higher complication rates, longer hospital stays, and higher mortality than patients who not develop CIN.Nearly one-third of the patients who require in-hospital dialysis because of CIN die prior to discharge.No current treatment can reverse or ameliorate CIN once it occurs.The occurrence of CIN is directly related to the number of pre-existing patient risk markers.After the high-risk patient population has been identified and risk markers addressed, the next step in preventing CIN is the use of different prophylactic therapies.The strongly associated r sk markers for CIN are pre-existing renal failure, diabetes mellitus, age greater than 70 years, concurrent use of nephrotoxic drugs, hypovolemia, use of a large amount of CM or

n ionic hyperosmol
r CM, and congestive heart failure.

Aim of the present chapter is to summarize the knowledge about the risk factors and prophylactic treatments of CIN according to the ultimate clinical research and developments.


Definition of CIN

A universally accepted definition of CIN does not exist.The most commonly used definition for CIN is the elevation of serum creatinine by ≥0.5mg/dl or ≥25% occurring within 48 hours after administration of CM, and the absence of an alternative etiology.Using the Cockcroft-Gault and the Modification of Diet in Renal Disease equations are useful in estimation of the GFR.Serum cystatin C has been proposed as an alternative endogenous marker of GFR showing higher correlation to standard clearance methods such as inulin or iohexol clearance.Serum cystatin C may detect CIN one to two days earlier than creatinine.Recent studies documented that serum and urine neutrophil gelatinase-associated lipocalin is an early predictive biomarker of CIN (Shaker et al., 2010).Urinary interleukin 18 and urinary livertype fatty acid-binding protein are new potential biomarkers of CIN (Perrin et al., 2012).Cholesterol atheroemboli, volume depletion, and interstitial nephritis should consider in diffe

ntial diagnosis of CIN.
he incidence of CIN is reported to be 0.6-2.3% in general population who do not have any risk factor for CIN, but the incidence can be increased to 90% in patients at high risk for CIN (Toprak, 2007).


Pathophysiology of CIN

The potential pathophysiologic mechanisms of CIN were summarized in Figure 1.Medullary hypoxia due to decreased renal blood flow secondary to rena

artery vasoconstriction, tubu
ar obstruction, direct tubular toxicity of the CM due to apoptosis, oxidative damage, endothelial dysfunction, and renal microcirculatory alterations may play a role in the pathogenesis of CIN.


Clinical course and outcomes

CIN may range in severity from asymptomatic, nonoliguric transient renal dysfunction to oliguric severe renal failure that necessitates permanent dialysis.CIN is reported to be the third leading cause of in-hospital acute renal failure after hypotension and surgery.Approximately $180 million is spent annually to manage CIN in the US.Dangas et al. showed that in-hospital outcomes such as death (6.3% vs 0.8%), cardiac death (4.0% vs 0.5%), coronary artery bypass grafting (5.8% vs 0.5%), major adverse cardiac event (9.3% vs 1.1%), packed red cell transfusion (28% vs 6%), vascular surgery of access site (5.6% vs 2.6%), post-procedure length of stay (6.8±7.1 vs 2.3±2.5)were significantly higher in CIN developed patients compare with control (p<0.0001).In cumulative one-year outcome death, out-of-hospital death and major adverse cardiac events were significantly higher in CIN developed patients (p<0.0001)(Dangas et al., 2005).In a study of acute myocardial infarction patients undergoing primary angioplasty, it was found that CIN developed patients have significantly higher incidence of high-rate atrial fibrillation (p=0.01),high-degree conduction disturbances requiring permanent pacemaker (p=0.04),acute pulmonary ed

a (p=0.008),respirato
y failure requiring mechanical ventilation (p<0.0001),cardiogenic shock requiring intra-aortic balloon (p<0.0001), and acute renal failure requiring renal replacement therapy (p<0.0001)(Marenzi et al., 2004).


Risk Factors for CIN

Specific factors that increase the risks for development of CIN are related to the patient, the contrast media, and the procedure (Table 1).The major risk factor for CIN is a GFR<60 ml/min/1.73m 2 .Chronic kidney disease is associated with decreased vasodilatory response, which is important in developing CIN, and in patients with renal insufficiency, the clearance of CM is slower than in normal subjects.In a study of 7586 patients who underwent coronary intervention, CIN developed in 22.4% of the patients who had serum creatinine levels of 2.0 to 2.9 mg/dl and in 30.6% of those with serum creatinine levels of 3.0 mg/dl or higher, compared with 2.4% of patients with serum creatinine levels <1.1 mg/dl ( Rihal et al., 2002).Two other studies (Moore et al., 1992;Barrett et al., 1992) reported that the incidence of CIN increased from 4% to 20% as the baseline serum creatinine increased from 1.2 to 2.9 mg/dl.In another study, the incidence of CIN increased from 8

to 92% as the seru
creatinine increased from 1.5 to 6.8 mg/dl.Furthermore, the probability of CIN requiring dialysis increases from 0.04% to 48% as the baseline GFR decreases from 50 to 10 ml/min (McCullough et al., 1997).


Diabetes mellitus

Nitric oxide-dependent renal vasodilatation is characteristically altered and renal outer medullary pO 2 is significantly reduced in diabetes mellitus.Chronic kidney disease and DM are associated with endothelial dysfunction and decreased vasodilatory responses.Diabetic nephropathy has been identified as a powerful and independent risk factor for CIN.Patients with diabetic nephropathy and a mean serum creatinine of 6.8 mg/dl had a 92% incidence of CIN after coronary angiography (Weinrauch et al., 1977).Patients with diabetes who have advanced chronic renal failure because of causes other than diabetic nephropathy are at significantly higher risk of developing CIN like diabetic nephropathy.On the other hand, studies have shown that when pre-existing renal disease is present, patients with and without diabetes are similarly at risk of CIN, which correlates with the degree of renal disease.Some authors have suggested that DM in the absence of nephropathy, particularly in insulin-dependent patients with diabetes, is associated with an increased risk of CIN (McCullough et al., 1997;Toprak 2007).In a study, it was found that the incidence of CIN was rather low (2%) in patients with neither diabetes nor azotemia, significantly higher (16%) in individuals with diabetes but preserved renal function, and much higher (38%) in patients who had both diabetes and azotemia (Lautin et al., 1991).In another study, the incidence of CIN was found to be 2% in patients without diabetes and 3.7% in patients with diabetes with a baseline creatinine of 1.1 mg/dl or less (OR=1.86,p=0.005).When renal function is mildly impaired (serum creatinine level 1.2 to 1.9 mg/dl), the risk of CIN in patients with diabetes mellitus increases to 4.5% (OR=2.42,p<0.001) (Rihal et al

2002).Other
tudies have failed to corroborate this connection (Parfrey et al., 1989).However, given that, those with diabetes alone were found to be at slightl

higher risk of
CIN than the general population.


Pre-diabetes

In a study of 421 patients who underwent coronary angiography with renal insufficiency, we presented that pre-DM increase the incidence of CIN


Hyperuricemia

Contrast agents have a uricosuric effect, which appears to be caused by enhanced renal tubular secretion of uric acid.Furthermore, hyperuricemia is accompanied by enhanced synthesis of reactive oxygen species, tubular obstruction by uric acid, an activated reninangiotensin-aldosterone system, increased endothelin-1, and an inhibited nitric oxide system which plays a role in the pathogenesis of CIN.In a prospective cohort study we evaluated 266 patients who undergoing elective coronary angiography and we found that patients with hyperuricemia are at risk of developing CIN (OR=4.71,p=0.019).CIN occurred in 15.1% of the hyperuricemic group and 2.9% of the normouricemic group (p<0.001).Length of hospital stay (p<0.001) and CIN requiring r

al replacement therap
(p=0.017) were significantly higher in hyperuricemic group.Serum uric acid ≥7 mg/dl in males and ≥5.9 mg/dl in females were found the best cut-off value for prediction of CIN (Toprak et al., 20

).


Hypercholesterolemia

Altered nitric oxide-dependent renal vasodilatation is prevale
t in hypercholesterolemia. Hypercholesterolemia aggravates CIN through the reduced production of nitric oxide (Yang et al., 2004).


Multivessel Coronary involvement, peripheral vascular disease, and renal artery stenosis

If a patient has multivessel coronary involvement, the other vessels in the body, such as the renal artery, can be involved.If the renal artery is involved, the renal blood supply may decrease and the kidneys may be more susceptible to CIN.Factors related to accelerated or diffuse atherosclerosis are linked to the development of CIN.The treatment of multivessel disease, challenging chronic total occlusions and extensively diseased coronary segments, may require high doses of CM for providing an optimal image quality, thus enhancing the potential toxic effects on the renal function.In a study of 177 patients who underwent cardiac catheterization, subjects were also evaluated for renal artery stenosis.Coronary artery disease was detected in 110 patients (62%

and signi
icant renal artery stenosis was detected in 19 patients (11%).Using multivariate analysis, it was found that the extent of coronary artery disease was an independent predictor of renal artery stenosis (Weber- Mzell et al., 2002).In a study a total of 5571 patients who underwent PCI were evaluated for CIN risk factors, and it was found that multivessel coronary involvement was only a univariate predictor of CIN (p=0.003)(Mehran et al., 2004).In two other cohort studies it was found that peripheral vascular disease is a risk for CIN in patients who underwent PCI (OR=1.9,p<0.0001 and OR=1.71, p=0.001, respectively) (Bartholomew et al., 2004; Rihal et al., 2002).In a study a total of 219 non-diabetic patients who underwent coronary angiography we have found that multivessel coronary involvement is a risk for CIN (OR=3.24,p=0.038) (

prak et
al., 2006).


Older age

In a prospective study in which elderly patients (≥70 years) were subjected to cardiac catheterization, 11% developed CIN (Rich & Crecelius, 1990).In another study, CIN incidence was 17% in elderly patients (>60 years) as compared with 4% in younger patients (Kohli et al., 2000).In 208 patients with acute myocardial infarction who underwent coronary intervention, it was found that an age of ≥75 years was an independent risk for CIN (OR=5.28,p=0.0009) (Marenzi et al., 2004).The possible reasons of the high incidence of CIN in elderly were age-related changes in renal func

on, more dif
icult vascular access following tortuosity, calcification of the vessels requiring greater amount of CM, defective prostaglandin synthesis, and the presence of renovascular disease.Furthermore, hypovolemia is very common in elderly patients.


Gender

Ovarian hormones can affect the renin-angiotensin system and renal blood flow.In a retrospective study of 8628 patients who underwent PCI, female sex was an independent predictor of CIN (OR=1.4,p<0.0001).One-year outcome analyses by gender showed a higher mortality among females than among males in a cohort of CIN patients (14% vs 10%, p=0.05) (Iakovou et al., 2003).The findings of this study contradict those of a previous randomized controlled trial of ionic vs nonionic CM, in which a multivariate analysis identified male gender as an independent risk factor for CIN (Rudnick et al., 1995).


Hypovolemia

Hypovolemia leads to active sodium reabsorbtion, which is an oxygen-d

anding process, and increases neurohumoral vasoconstrictive stimuli that
might compromise medullary oxygenation.The toxic effects of CM on the renal tubular lumen may be exacerbated in hypovolemia.Decreased effective circulating volume and reduced renal perfusion potentiate renal vasoconstriction after administration of intravascular CM.Volume expansion reduces the activity of the renin-angiotensin system, minimizes increases in blood viscosity and osmolality, and increases medullary perfusion.At present the most convincing preventive procedure of CIN is adequate hydration with isotonic saline or sodium bicarbonate.Before coronary angiography, the volume status of patients can be assessed through the inferior vena cava index, mean atrial pressure, noninvasive pulmonary-capillary wedge pressure or bioimpedance spectroscopy (Toprak & Cirit, 2005).


Congestive heart failure and reduced left ventricular ejection fraction

Advanced heart failure and reduced LVEF are characterized by effective volume depletion caused by low cardiac output and increased n

rohumoral vas
constrictive stimuli and impaired nitric oxide-dependent renal vasodilatation that might compromise medullary oxygenation.Studies have shown that reduced left ventricular ejection fraction (LVEF) (≤49%) and advanced congestive heart failure (New York Heart Association class III or IV) are independent risk factors for CIN.In a study, Dangas et al. showed that LVEF below 40% is an independent predictor of CIN (Dangas et al., 2005).We have previously reported that if the LVEF is greater than 30%, this condition does not show any significant effect on the development of CIN (To

ak et al., 2003).In a study it was shown that con
estive heart failure was an independent risk for CIN (OR=1.53,p=0.007) (Rihal et al., 2002).In a cohort study it was found that congestive heart failure is a risk for CIN in patients who underwent PCI (OR=2.2,p<0.0001) (Bartholomew et al., 2004).


Hypertension

An explanation for hypertension as a risk factor for CIN is: alterations in the intrarenal expression of vasoactive mediators, such as the renin-angiotensin system or nitric oxide, may be contributing factors.Impaired nitric oxide-dependent renal vasodilatation is prevalent in individuals who are hypertensive.Finally, a reduced number of nephrons could predispose hypertensive patients to CIN.In a study of 8628 patients who underwent percutaneous interventions, hypertension was found to be an independent predictor of CIN (OR=1.2,p=0.0035).In a cohort study Bartholomew et


ACE inhibitors and angiotensin receptor blockers

ACE inhibitors have been identified as a risk factor for CIN because of their potential to reduce renal function.On the other hand, some small studies have shown that the nephrotoxicity of CM may be reduced because of decreased renal vasoconstriction by inhibition of angioten

n II.Renal vasoco
striction occurs after the CM administration and the renin-angiotensin system is responsible for this vasoconstriction.In a randomized controlled study with 71 patients with diabetes who underwent coronary angiography randomized to captopril or control, 25-mg captopril was given three times daily.There was a significant decrease in CIN in the patients who received captopril compared with the control group (6% vs 29%, respectively, p<0.02) (Gupta et al., 1999)


Renal transplantation

Patients with renal transplantation may be at a higher risk of CIN due to concomitant use of cyclosporine and higher prevalence of diabetes and renal insufficiency.In a study, 33 patients with a functioning renal allograft who underwent different contrast studies, the incidence of CIN was 21.2% (Ahuja et al., 2000).


Acute myocardial infarction

A study by Rihal et al. showed that acute myocardial infarction within 24 h before administrati

of the CM is a risk f
ctor for CIN (OR=1.85,p=0.0006).This study demonstrates that CIN is a frequent complication in acute myocardial infarction, even in patients with a normal baseline renal function.(Rihal et al., 2002).In a study of 208 acute myocardial infarction patients who underwent primary PCI, anterior acute myocardial infarction

s significantly higher in pa
ients who developed CIN (p=0.0015).However, in multivariate analysis, anterior acute myocardial infarction (OR=2.17,p=0.09) was not a risk for CIN (Marenzi et al., 2004).In 2082 percutaneous interventions for acute myocardial infarction, it was reported a more than seven-fold (3.2% vs 23.3%) increase in 1-year mortality in patients who developed CIN (Sadeghi et al., 2003).


Anemia

Anemia-induced deterioration of renal ischemia may be one plausible explanation for the higher incidence of CIN in patients with a low hematocrit level.A baseline hematocrit value of less than 39% for men and less than 36% for women is a risk for CIN.The relationship between low hematocrit levels and CIN has been investigated in a prospective study of 6773 patients who underwent PCI (Nikolsky et al., 2005).A lower baseline hematocrit was an independent predictor

CIN; a
d each 3% decrease in baseline hematocrit resulted in a significant increase in the odds of CIN in patients with and without chronic kidney disease (11% and 23%, respectively).Dangas et al. showed that the baseline hematocrit level is an independent predictor of CIN in patients with chronic kidney disease (OR=0.95,p<0.00001) (Dangas et al., 2005).


Low serum albumin

Hypoalbuminemia impairs endothelial function, enhances renal vasoconstriction, impairs the synthesis and release of nitric oxide, and decreases antioxidant enzyme activity.In a study, low serum albumin (<3.5 g/dl) was identified as a risk factor for CIN in patients 70 ye

s of age or older who underwent cardiac catheterization (Rich, et al., 1990).Also we have found that in 230 patients who
nderwent coronary angiography with renal insufficiency, serum albumin level ≤3.5 g/dl was a risk factor for CIN (OR=5.79,p=0.005) (Cirit et al., 2006).


Hypotension, sepsis, cirrhosis, and pulmonary edema

A systolic blood pressure of less than 80 mm Hg for at least 1 h that requires inotropic support with medications is a risk factor for CIN.A study by Dangas et al showed that periprocedural hypotension and pulmonary edema are independent predictors of CIN in patients with chronic kidney disease

OR=2.50,p<0.00001 and OR=2.56, p=
.001, respectively) (Dangas et al., 2005) Sepsis, through direct damage by bacterial toxins to renal tubules and impairment of circulation, has also been reported as a risk factor.Reduction of effective intravascular volume caused by liver cirrhosis has been reported as contributing to pre-renal reduction in renal perfusion, thus enh

cing the ischemic insult of CM (Toprak, 2007).


P
ocedure-related risk factors 2.3.2.1. Short duration of the two contrast administration and urgent/emergency procedure

In those who have no risk factors for CIN, angiography should be delayed more than 48 hours after a pr

ious exposure to intravasc
lar contrast media.In patients with diabetes or preexisting renal disease, this time interval should be increased to more than 72 hours.In a cohort study, urgent/emergency procedure was found as a predictor of CIN (OR=4, p<0.0001) (Bartholomew et al., 2004).The higher risk of developing CIN in patients with urgent status was irrespective of baseline renal function.


Use of intra-aortic balloon pump

Using intra-aortic balloon pump may signify a very high-risk population due to very severe coronary atherosclerosis and/or indicate a role of atheroembolism.In 208 consecu-tive acute myocardial infarction patients undergoing percutaneous coronary intervention, use of intra-aortic balloon pump was a risk predictor of CIN (OR=15.51,p<0.0001) (Marenzi et al., 2004).In a study, it has demonstrated that, intra-aortic balloon pump use is an independent predictor of CIN in patients with chronic kidney disease (OR=2.27,p=0.004) (Dangas et al., 2005).In another study, it was found that the use of intra-aortic balloon pump was a risk factor for CIN requiring dialysis after PCI (OR=1.94)(Gruberg et al., 2001).In another derivation and validation cohort study, intra-aortic balloon pump use was a risk for CIN in patients undergoing coronary intervention (OR=5.1,p<0.0001) (Bartholomew et al., 2004).


Bypass graft intervention and delayed reperfusion

Procedures ith bypass angiography and intervention may be associated with higher complexity, longer duration, and limited success, thus indicating an unstable post-procedural period with impaired cardiac output.


Contrast medium-related risk factors 2.3.3.1. Increased dose of contrast medium

According to different sources, the relatively safe cutoff point of contrast amount varies from 70 ml up to 220ml.However, doses as low as 20 to 30 ml are capable of inducing CIN.In a study that patients undergoing coronary angiography, each 100 ml of contrast medium administered was associated with a significant increase of 12% in the risk of CIN (OR=1.12,p=0.02) (Rihal et al., 2002).Marenzi et al. showed that contrast volume >300 ml is an independent risk for CIN (OR=2.80,p=0.02) (Marenzi et al., 2004).In another study patients with preexisting renal ailure revealed a 10-fold risk of CIN when more than 125 ml of contrast media was administered (Taliercio et al.

1986).


High-osmolar and ionic CM

Most side effect
attributable to contrast medias are related to hypertonicity.Currently, four main types of contrast media are used in routine practice today, including nonionic low-osmolar, ionic low-osmolar, nonionic iso-osmolar, and i

ic high-osmolar contrast media.In a large study which
comparing the non-ionic low-osmolality agent iohexol to the ionic high-osmolality agent meglumine/sodium diatrizoate in patients with pre-existing renal dysfunction undergoing angiography, patients with renal insufficiency receiving diatrizoate were 3.3 times as likely to develop CIN compared to those receiving iohexol (Rudnick et al., 1995).NEPHRIC trial is a randomized, prospective study comparing the nonionic iso-osmolar CM iodixanol with the nonionic low-osmolar CM iohexol in 129 renal impairment patients with diabetes undergoing coronary or aorto-femoral angiography.The

cidence of CIN was 3% in the i
dixanol group and 26% in the iohexol group (p=0.002)(Aspelin et al., 2003).In another randomized study, the renal tolerance of iodixanol and iohexol was compared in 124 patients with creatinine >1.7 mg/dl.The incidence of CIN was 3.7% in iodixanol group and 10% in iohexol group (p>0.05)(Chalmers et al., 1999).The available data do not provide clear evidence that the whole iso-osmolar CM class offers an improvement over the low-osmolar CM class.

Other s

dies with iodixan
l in renal failure patients have shown a higher incidence of CIN than that observed in the NEPHRIC study (21% in the RAPPID trial, 30% in the CONTRAST trial) (Baker et al., 2003: Stone et al., 2003).In addition to their osmolarity, contrast medias are characterized as ionic versus non-ionic.Small clinical trials of lowrisk patients undergoing coronary angiography have shown little difference in the risk of CIN between the 2 types of CM.However, a randomized trial of 1196 patients undergoing coronary angiography showed that non-ionic CM reduced the incidence of CIN in patients with preexisting renal disease with or without diabetes (Rudnick et al., 1995).In addition, symptomatic or hemodynamic adverse drug events have been shown to occur less often with non-ionic, low-osmolality CM compared with ionic, high-osmolality CM.

In high-risk patients, it is reasonable to don't use the high-osmolar and ionic CM to minimize the risk of CIN.


Intra-arterial administration of the contrast media

Intra-arterial contrast administration is a risk for CIN.This effect is thought to be due to the fact that the acute intra renal concentration of CM is much higher after intra arterial rather than intravenous injection.


Scoring method to predict high risk patients for CIN

Mehran et al. developed a simple scoring method that integrates eight baseline clinical variables to assess the risk of CIN after percutaneous coronary intervention (PCI).These are hypotension (score 5), use of intra-aortic balloon pump (score 5), congestive heart failure (score 5), serum creatinine>1.5mg/dl (score 4), age>75 years (score 4), anemia (score 3), diabetes mellitus (score 3), and volume of CM (score 1 per 100 ml).If the total score is 5 or less, the risk category is low; if the total score is 16 or higher, the risk category is very high (Mehran et al., 2004).


Prevention Strategies for CIN

Extracellular volume expansion with intravenous saline or sodium bicarbonate, minimizing the dose of CM, using low-osmolar non-ionic CM instead of high osmolar ionic CM, stopping the intake of nephrotoxic drugs and avoiding short intervals between procedures requiring CM have all been shown to be effective in reducing CIN.Alternatives to ordinary CM, such as carbon dioxide or gadolinium chelates, can be used in patients at high risk of CIN (Table 2).


Volume expansion

Volume expansion is the single most important measure that has been documented to be beneficial in preventing CIN.A standardized saline hydration protocol has been proven effective in reducing the risk of CIN and should be used routinely.The most widely accepted protocol is administering isotonic saline at 1 to 1.5 ml/k

h beginning 6 to
2 hours prior to the procedure and continuing for up to 12 hours following contrast administration.In a randomized trial, two different hydration regimens were compared in 1620 patients undergoing coronary interventions.They showed that the incidence of CIN was significantly lower among patients given an isotonic saline solution than among those given a hypotonic saline solution (0.7% vs. 2.0% respectively, p=0.04) (Mueller et al., 2002).In another trial, a total of 119 patients with serum creatinine exceeding 1.1 mg/dl were randomized to receive isotonic solution of sodium bicarbonate (n=59) or isotonic saline (n=60) at a rate of 3 ml/kg/h for 1 hour before and 1 ml/kg/h for 6 hours after contrast administration.CIN developed in only 1 patient (1.7%) compared with 8 patients (13.6%) in the saline group (p=0.02)(Merten et al., 2004).The authors postulated that a reduction in oxidative injury may have conferred protection against CIN.However, further studies are required to clarify the role of hydration with sodium bicarbonate in preventing CIN.In a prospective study, the effect of combi-nation intravenous and oral volume supplementation on the development of CIN was studied in 425 patients undergoing percutaneous coronary intervention.Patients were randomly assigned to receive hydration with either isotonic or half-isotonic.In addition patients were encouraged to drink plenty of fluids (at least 1500 ml).They found that applying the combination of intravenous and oral volume supplementation results in a very low incidence of CIN (1.4%) (Mueller et al., 2005).Most studies have found that hydration alone is better than hydration combined with a diuretic.In a study, 78 patients with serum creatinine >1.6 mg/dl were randomized to three groups: hydration alone, hydration with mannitol and hydration with furosemide.Half-isotonic saline was used for hydration.CIN occurred in 11%, 28% and 40% of patients in the three groups, respectively (p=0.02), thus showing that forced diuresis is of no benefit in preventing CIN.In a meta-analysis it was found that the administration of sodium bicarbonate is superior to the administration of saline alone in the prevention of CIN (Solomon et al., 1994).The effectiveness of sodium bicarbonate treatment to prevent CIN in high-risk patients remains uncertain.


N-acetylcysteine

Antioxidant N-acetylcysteine (NAC) might scavenge oxygen free radicals, thus attenuate the cytotoxic effects of CM.NAC may also have direct vasodilating effects on the kidneys through an increase in the biologic effects of nitric oxide.Tepel et al. were evaluated the effects of NAC (600 mg orally twice daily), at first time, in 83 patients undergoing computed tomography.Two percent of the patients in the NAC group had CIN versus 21% in the placebo group (p=0.01)(Tepel et al., 2000).Since then, a number of trials have been published.Results from these trials have been inconsistent.In a randomized, placebo-controlled study it was found that NAC is protective against CIN Fifty-four patients were randomized to receive either 600 mg of NAC twice daily for 4 doses or placebo.The incidence of CIN was 8% in the NAC group versus 45% in the placebo group (p=0.005)(Diaz-Sandoval et al., 2002).In addition to oral administration, intravenous administration of NAC to protect against CIN has also been evaluated.In a study, Baker et al. randomly assigned 80 patients to receive either NAC infusion (n=41) versus saline infusion (n=39).CIN developed in only 2 (5%) of patients in the NAC group compared with 8 (21%) in the saline group (p=0.04)(Baker et al., 2003).The authors concluded that NAC infusion protects against CIN.In a meta-analysis, evaluating more than 800 patients at high risk of developing CIN also documented a positive impact of NAC prophylaxis on CIN (Birck et al., 2003).In another meta-analysis, nine randomized controlled trials were included and the difference in mean change in creatinine between the NAC treated group and controls was -0.27 mg/dl.The relative risk of developing CIN was 0.43 in subjects randomized to NAC.They suggest that NAC helps prevent declining renal function and CIN (Liu et al., 2005).In contrast to these reports, some studies failed to find a significant effect of NAC on the occurrence of CINA total of 183 patients with preexisting renal insufficiency undergoing contrast study were randomly assigned to receive NAC at a dose of 600 mg twice daily on the day before and the day of the contrast study plus saline infusion or saline alone.The incidence of CIN was 6.5% in the NA

group versus 1
% in the control group (p=0.22)(Briguori et al., 2002).In a multi centric double blind clinical trial 156 patients undergoing coronary angiography or percutaneous coronary intervention with creatinine clearance <50 ml/min were randomly assigned to receive N-acetylcysteine 600 mg orally twice daily for two days or placebo.Sixteen patients developed CIN.Eight of 77 patients (10.4%) in the NAC group and eight of 79 patients (10.1%) in the placebo group (p=1.00).No difference was observed in the change in endogenous creatinine clearance, p=0.28).They

oncluded th
t oral NAC did not prevent CIN in patients at low to moderate risk undergoing cardiac catheterisation with ionic low osmolality CM (Gomes et al., 2005).In another study, 50 patients undergoing elective diagnostic coronary angiography with serum creatinine values above 1.3 mg/dl were included and CIN was detected in 3 of 25 patients (12%) in the NAC group and 2 of 25 patients (8%) in the control group (p>0.05).It was detected that in patients planned to undergo elective diagnostic coronary angiography with renal dysfunction, oral NAC and hydration before the procedure was not more effective than hydration alone in the prevention of CIN (Gulel et al., 2005).A direct renoprotective effect of NAC remains questionable.To date, only a few trials described the effects of NAC not only on serum creatinine but also on clinical end points.The serum creatinine can be decrease in administration of NAC without renoprotective effect.In a prospective stud

NAC was given at a do
e of 600 mg every 12 h for a total of four doses to the volunteers with a normal renal function who did not receive contrast agent.There was a significant decrease of the mean serum creatinine (p<0.05) and a significant increase of the GFR (p<0.02),whereas the cystatin C concentration did not change significantly (Hoffmann et al., 2004).In patients undergoing emergency diagnostic procedures, in which a full hydration protocol is not possible, an abbreviated hydration regimen plus oral or intravenous administration of NAC can be recommended.NAC may be of benefit mostly in high-risk patients.If NAC is to be used as a preventative measure, it should be given at a dose of 600 mg orally twice da

y on the day before and d
y of the procedure.


Ascorbic acid

Prophylactic oral administration of ascorbic acid may protect against CIN.In a randomized, placebo-controlled trial in 231 patients with serum creatinine ≥1.2 mg/dl who undergoing coronary angiography showed that the use of ascorbic acid was associated with a significant reduction in the rate of CIN.CIN occurred in 11 of the 118 patients (9%) in the ascorbic acid group and in 23 of the 113 patients (20%) in the placebo group (OR=0.38;p=0.02) (Spargias et al., 2004).Further prospective studies are needed to validate these preliminary results.


Fenoldopam

Fenoldopam mesylate is a selective dopamine-1 receptor agonist that produces systemic, peripheral and renal arterial vasodilatation.Several investigators have reported a positive impact of fenoldopam against CIN in small studies.In a placebo-controlled, double-blind, multicenter trial, 315 patients with creatinine clearance of less than 60 ml/min were randomized to receive fenoldopam infusion [0.05 µg/kg/min titrated to 0.1 µg/kg/min (n=157)] or matching placebo (n=158).CIN occurred in 33.6% of patients in the fenoldo-pam group compared with 30.1% of patients in the placebo group (p=0.61)(Stone et al., 2003).The authors concluded that fenoldopam did not protect against CIN.In 2 other large studies comparing fenoldopam with NAC treatment with fenoldopam either had a similar, non significant effect as that of NAC or was inferior to it (Allaqa

nd et al., 2002;Br
guori et al., 2004).The routine use of fenoldopam cannot be recommended at the present time.


Adenosine antagonists

CM stimulate the intrarenal secretion of adenosine, which binds to the renal adenosine receptor and acts as a potent vasoconstrictor, reducing renal blood flow and increasing the generation of oxygen free radicals as it is metabolized to xanthine and hypoxanthine.Theophylline and aminophylline, adenosine antagonists, have also been studied in the prevention of CIN in a number of trials.Studies with these agents ha

used varying doses and dosage fo
ms and yielded conflicting results (Erley et al., 1999;Kapoor et al., 2001).Based on the conflicting information found in clinical studies, adenosine antagonists should not be routinely used in patients as a preventative measure at this time.


Calcium channel blockers

The calcium channel antagonists verapamil and diltiazem have been found to attenuate the renal vasoconstrictor response after exposure to CM.However, when the efficacy of the felodipine, nitrendipine and nifedipine was evaluated, results were inconsistent.Two small studies performed the use of sublingual nifedipine given prior to

ntrast administration.P
tients (n=20) who received sublingual nifedipine did not have a significant increase in serum creatinine, while those in the placebo group did (Rodicio et al., 1990).In another study, patients (n=30) who received nifedipine had an increase in renal plasma flow following administration of contrast, while patients in the placebo group had a decrease in renal flow (Russo et al., 1990).One other study showed that nitrendipine use cause a significant reduction in the GFR in the placebo group compared to little or no change in GFR in the n

rendipine group (Neum
yer et al., 1989).In another study, 27 patients with normal to moderately reduced renal function underwent femoral angiography randomized to receive either oral felodipine or placebo.Patients in the felodipine group had a significant increase in serum creatinine from baseline, while patients in the placebo group did not demonstrate a simil

increas
(Spangberg-Viklund et al., 1996).More large-scale trials are needed before calcium channel blockers can be routinely recommended in patients prior to CM administration.


Prostaglandin E 1

PGE 1 has vasodilatory effects that may be beneficial in preventing CIN.In one study, 130 patients were randomly assigned to receive either placebo or one of three doses of PGE 1 .The increase in serum creatinine level was smaller in all of the three PGE 1 groups than in the placebo group, but the difference was significant only in the medium-dose (20 ng/kg/min) of PGE 1 group (

ch et al.,
2000).More studies need to be done to better understand the role of prostaglandin E1, but results from this pilot study appear promising.


Atrial Natriuretic Peptide (ANP)

ANP may prevent CIN by increasing renal blood flow.In a study, ANP was included in one of the four arms.In which dopamine, mannitol, and ANP caused an increase in CIN in diabetic patients as compared to saline alone (Weisberg et al., 1994).In another trial patients were randomized to one of four treatment arms: fluid alone or one of three doses of ANP.

Results showed no statistically significant differences in the incidence of CIN between any of the four treatment arms (Kurnik et al., 1998) Based on these results and the limited clinical data, ANP cannot be advocated in the prevention of CIN.


Endothelin antagonists

Endothelin-1 is a potent endogenous vasoconstrictor, is thought to play a role in the development of CIN.Endothelin-1 has two primary receptors.In animal studies, endothelin-A antagonists were shown to reduce the incidence of CIN (Li

et al., 2003).However, in a ran
omized study of 158 patients, the use of a mixed endothelin-A and B antagonist was associated with a significantly higher incidence of CIN than was placebo (56% vs. 29%, p=0.002) (Wang et al., 2000).Endothelin antagonists currently have no role in prevention of CIN.


Low-dose of dopamine

At low doses (1-3 mcg/kg/min), dopamine activates two types of dopamine (DA) receptors, DA-1 and DA-2.Activation of the DA-1 receptor results in an increase in natriuresis and renal blood flow.Since dopamine, at low doses, is believed to be more selective for the DA-1 receptors, it has been investigated in the prevention of CIN. to continue with the saline, receive aminophylline in addition to the saline, or receive dopamine plus saline.In the dopamine plus saline group, 50% of patients developed CIN, while only 30% of the patients in the saline-alone group developed CIN.This difference did not reach statistical

ignificance, but it appeared
hat use of dopamine might worsen outcomes (Abizaid et al., 1999).Low-dose dopamine use cannot be supported at this time.


Statins

Whether additional benefits can be achieved with the use of statin in decreasing the risk of CIN remains undetermined.In a recent meta analysis of randomised controlled trials comparing statin pretreatment with non-statin pretreatment for the prevention of CIN, it was found that, the incidence of CIN was not significantly lower in statin pretreatment group as compared with control group (RR=0.76,p=0.30) (Zhang et al., 2011).The current cumulative evidence suggests that statin pretreatment may neither prevent CIN nor reduce the need for renal replacement therapy.


Nebivolol

In an experimental study we demonstrated that nebivolol have a protective role against CIN.Nebivolol leads to a decrease in the systemic and renal oxidative stres (p=0.001) and an increase in renal nitrite production (p=0.027).In addition, contrast-induced proteinuria, proteinaceous cast (p< 0.001), and tubular necrosis (p=0.001) are restored by nebivolol (Toprak et al., 2008).Two recent human studies demonstrated the protective effect of nebivolol on CIN.One of the study showed that the use of oral nebivolol for one week at a dose of 5 mg per day decrease the incidence of CIN in patients who underwent coronary angiography with renal dysfunction (p=0.03)(Avci et al., 2011).Another more recent study showed that the use of oral nebivolol for 4 days at a dose of 5 mg per day is protective against nephrotoxic effects of CM in patients who underwent coronary angiography or ventriculography (Gunebakmaz et al., 2012).More large-scale trials are needed before nebivolol can be routinely recommended in prevention of CIN.


Hemofiltration and hemodialysis

Currently available d

a do not su
port use of prophylactic hemodialysis for prevention of CIN.In a trial of 113 patients, reported that CIN occurred in 24% of the hemodialysis group as compared with 16% of non-hemodialysis group (Vogt et al., 2001).Clinically relevant events also were not different in two groups.Only continuous venovenous hemofiltration has been shown to protect against CIN.In a study, 114 patients with chronic renal failure undergoing percutaneous coronary intervention were divided in two groups: 56 patients received normal saline and 58 patients underwent hemofiltration at a rate of 1000 ml/h (Marenzi et al., 2003).Hemofiltration seems to have a protective effect, including significant reduction in in-hospital and 1-year mortality compared with routine hydration.The mechanisms of this benefit are not clear.Further studies are needed to confirm the results of this tr