***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVES Prophylactic acetylcysteine along with hydration seems to be better than hydration alone in preventing the reduction in renal function induced by a contrast dye . BACKGROUND Contrast media can lead to acute renal failure that may occasionally require hemodialysis . METHODS One hundred eighty-three consecutive patients with impairment of renal function , undergoing coronary and /or peripheral angiography and /or angioplasty , were r and omly assigned to receive 0.45 % saline intravenously and acetylcysteine ( 600 mg orally twice daily ; group A , n = 92 ) or 0.45 % saline intravenously alone ( group B , n = 91 ) before and after nonionic , low-osmolality contrast dye administration . RESULTS The baseline serum creatinine concentrations were similar ( 1.5 + /- 0.4 mg/dl in group A vs. 1.5 + /- 0.4 mg/dl in group B ; p = 0.37 ) . An increase of > or = 25 % in the baseline creatinine level 48 h after the procedure occurred in 6 ( 6.5 % ) of 92 patients in group A and in 10 ( 11 % ) of 91 patients in group B ( p = 0.22 ) . In the subgroup with a low ( < 140 ml ) contrast dose , renal function deterioration occurred in 5 ( 8.5 % ) of 60 patients in group B and in 0 of 60 patients in group A ( p = 0.02 ; odds ratio [ OR ] 0.44 , 95 % confidence interval [ CI ] 0.35 to 0.54 ) . In the subgroup with a high contrast dose , no difference was found ( 5/31 vs. 6/32 patients , p = 0.78 ) . By multivariate analysis , the amount of contrast agent , but not the treatment strategy , was a predictor of the occurrence of contrast dye-associated nephrotoxicity ( OR 2.58 , 95 % CI 1.1 to 4.9 ; p = 0.035 ) . CONCLUSIONS In patients with reduced renal function undergoing angiography and /or angioplasty , the amount of contrast agent , but not the administration of prophylactic acetylcysteine , was a predictor of renal function deterioration .  Prophylactic acetylcysteine might provide better protection than hydration alone , only when a small volume of contrast agent is used CONTEXT The antioxidant acetylcysteine prevents acute contrast nephrotoxicity in patients with impaired renal function who undergo computed tomography scanning . However , its role in coronary angiography is unclear . OBJECTIVE To determine whether oral acetylcysteine prevents acute deterioration in renal function in patients with moderate renal insufficiency who undergo elective coronary angiography . DESIGN AND SETTING Prospect i ve , r and omized , double-blind , placebo-controlled trial conducted from May 2000 to December 2001 at the Grantham Hospital at the University of Hong Kong . PARTICIPANTS Two hundred Chinese patients aged mean ( SD ) 68 ( 6.5 ) years with stable moderate renal insufficiency ( creatinine clearance < 60 mL/min [ 1.00 mL/s ] ) who were undergoing elective coronary angiography with or without intervention . INTERVENTION Participants were r and omly assigned to receive oral acetylcysteine(600 mg twice per day ; n = 102 ) or matching placebo tablets ( n = 98 ) on the day before and the day of angiography . All patients received low-osmolality contrast agent . MAIN OUTCOME MEASURES Occurrence of more than a 25 % increase in serum creatinine level within 48 hours after contrast administration ; change in creatinine clearance and serum creatinine level . RESULTS Twelve control patients ( 12 % ) and 4 acetylcysteine patients ( 4 % ) developed a more than 25 % increase in serum creatinine level within 48 hours after contrast administration ( relative risk , 0.32 ; 95 % confidence interval [ CI ] , 0.10 - 0.96 ; P = .03 ) . Serum creatinine was lower in the acetylcysteine group ( 1.22 mg/dL [ 107.8 micromol/L ] ; 95 % CI , 1.11 - 1.33 mg/dL vs 1.38 mg/dL [ 122.9 micromol/L ] ; 95 % CI , 1.27 - 1.49 mg/dL ; P = .006 ) during the first 48 hours after angiography . Acetylcysteine treatment significantly increased creatinine clearance from 44.8 mL/min ( 0.75 mL/s ) ( 95 % CI , 42.7 - 47.6 mL/min ) to 58.9 mL/min ( 0.98 mL/s ) ( 95 % CI , 55.6 - 62.3 mL/min ) 2 days after the contrast administration ( P<.001 ) . The increase was not significant in the control group ( from 42.1 to 44.1 mL/min [ 0.70 to 0.74 mL/s ] ; P = .15 ) . The benefit of acetylcysteine was consistent among various patient subgroups and persistent for at least 7 days . There were no major treatment-related adverse events . CONCLUSION Acetylcysteine protects patients with moderate chronic renal insufficiency from contrast-induced deterioration in renal function after coronary angiographic procedures , with minimal adverse effects and at a low cost STUDY OBJECTIVE To determine the incidence of cardiovascular and renal toxicity of a nonionic contrast agent when used for cardiac catheterization , and to assess the value of electrolytes and urinalysis results as predictors of nephropathy induced by a contrast agent . STUDY DESIGN Nonr and omized trial using a criterion st and ard and a cohort analytic study with a 48-hour follow-up . SETTING Referral-based university hospital . PATIENTS Convenience sample of patients having diagnostic cardiac catheterization .  Renal function and clinical status were evaluated at baseline in 1,144 patients ; at 24 hours in 1,077 ( 94 % ) ; and at 48 hours in 663 ( 57 % ) . INTERVENTIONS After patients received saline for hydration , coronary angiography and left ventriculography were done with iopamidol ( average dose , 203 + /- 56 cc ) . MEASUREMENTS AND MAIN RESULTS The definite and possible incidence of major acute cardiovascular complications from nonionic contrast media was 0.2 % and 0.7 % , respectively . The mean serum creatinine level increased 11.5 mumol/L from baseline at 24 hours ( P less than 0.0001 ) and 16.8 mumol/L from baseline at 48 hours ( P less than 0.0001 ) . Results in a r and omly selected training sample were studied to determine predictors of a rise in serum creatinine of 44.2 mumol/L or more . The baseline serum creatinine level and age were significant predictors of renal injury , but hypertension , diabetes mellitus , congestive heart failure , vascular disease , the volume of contrast agent injected or baseline values of urinary variables did not predict nephrotoxicity . In an independent validation sample , only the baseline serum creatinine level was confirmed as a predictor of nephrotoxicity , whereas age was not . A model that predicted contrast-induced nephropathy by the serum creatinine level showed an exponential increase in the risk for nephrotoxicity if the baseline level was 106.1 mumol/L or higher . CONCLUSIONS Patients have a small but significant rise in serum creatinine after cardiac catheterization with a nonionic contrast agent . Baseline renal insufficiency is the only confirmed predictor of nonionic contrast-induced nephrotoxicity BACKGROUND Injections of radiocontrast agents are a frequent cause of acute decreases in renal function , occurring most often in patients with chronic renal insufficiency and diabetes mellitus . METHODS We prospect ively studied 78 patients with chronic renal insufficiency ( mean [ + /- SD ] serum creatinine concentration , 2.1 + /- 0.6 mg per deciliter [ 186 + /- 53 mumol per liter ] ) who underwent cardiac angiography .  The patients were r and omly assigned to receive 0.45 percent saline alone for 12 hours before and 12 hours after angiography , saline plus mannitol , or saline plus furosemide . The mannitol and furosemide were given just before angiography . Serum creatinine was measured before and for 48 hours after angiography , and urine was collected for 24 hours after angiography . An acute radiocontrast-induced decrease in renal function was defined as an increase in the base-line serum creatinine concentration of at least 0.5 mg per deciliter ( 44 mumol per liter ) within 48 hours after the injection of radiocontrast agents . RESULTS Twenty of the 78 patients ( 26 percent ) had an increase in the serum creatinine concentration of at least 0.5 mg per deciliter after angiography . Among the 28 patients in the saline group , 3 ( 11 percent ) had such an increase in serum creatinine , as compared with 7 of 25 in the mannitol group ( 28 percent ) and 10 of 25 in the furosemide group ( 40 percent ) ( P = 0.05 ) . The mean increase in serum creatinine 48 hours after angiography was significantly greater in the furosemide group ( P = 0.01 ) than in the saline group . CONCLUSIONS In patients with chronic renal insufficiency who are undergoing cardiac angiography , hydration with 0.45 percent saline provides better protection against acute decreases in renal function induced by radiocontrast agents than does hydration with 0.45 percent saline plus mannitol or furosemide OBJECTIVES This study was design ed to test a rapid protocol of intravenous acetylcysteine for prevention of radiocontrast-induced nephropathy ( RCIN ) . BACKGROUND Oral acetylcysteine ( NAC ) may provide better prophylaxis against RCIN than intravenous ( i.v . ) hydration alone . Current protocol s preclude prophylaxis of same-day or emergency patients owing to the need for prolonged pretreatment . METHODS We prospect ively r and omized 80 patients with stable renal dysfunction undergoing cardiac catheterization/intervention to a rapid protocol of i.v . NAC ( 150 mg/kg in 500 ml N/saline over 30 min immediately before contrast followed by 50 mg/kg in 500 ml N/saline over 4 h , n = 41 , 67 + /- 10 years , 90 % men ) or  i.v . hydration ( 1 ml/kg/h N/saline for 12 h pre- and post-contrast , n = 39 , 71 + /- 8.8 years , 85 % men ) . RESULTS Radiocontrast-induced nephropathy occurred in 2 of the 41 patients in the NAC group ( 5 % ) and in 8 of the 39 patients in the hydration group ( 21 % ; p = 0.045 ; relative risk : 0.28 ; 95 % confidence interval 0.08 to 0.98 ) . In the NAC group , mean serum creatinine fell from 1.85 + /- 0.59 to 1.77 + /- 0.73 and 1.79 + /- 0.73 mg/dl 48 h and four days post-contrast ( p = 0.02 and 0.023 vs. baseline , respectively ) . In the hydration group , serum creatinine increased from 1.75 + /- 0.41 to 1.81 + /- 0.6 48 h and 1.80 + /- 0.50 mg/dl four days post-contrast ( p = 0.99 and 0.23 , respectively ) .  NAC infusion was ceased after the bolus in three patients ( 7 % ) due to flushing , itching , or a transient rash . CONCLUSIONS Administration of i.v . NAC should be considered in all patients at risk of RCIN before contrast exposure when time constraints preclude adequate oral prophylaxis , provided the patient is able to tolerate this degree of volume loading BACKGROUND Radiographic contrast agents can cause a reduction in renal function that may be due to reactive oxygen species . Whether the reduction can be prevented by the administration of antioxidants is unknown . METHODS We prospect ively studied 83 patients with chronic renal insufficiency ( mean [ + /-SD ] serum creatinine concentration , 2.4+/-1.3 mg per deciliter [ 216+/-116 micromol per liter ] ) who were undergoing computed tomography with a nonionic , low-osmolality contrast agent . Patients were r and omly assigned either to receive the antioxidant acetyl 
    Output:
    
: Our findings suggest that N-acetylcysteine helps prevent declining renal function and contrast-induced nephropathy .
While N-acetylcysteine is inexpensive and nontoxic , undeviating insistence for dosing at least 12 hours in advance of contrast exposure may delay diagnostic and therapeutic procedures .