***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: BACKGROUND Nonionic , low-osmolality radiocontrast agents are used frequently because they are believed to be safer than ionic , high-osmolality agents , but they are also more expensive . We conducted a r and omized trial to compare the incidence of adverse events after the administration of ionic , high-osmolality and of non-ionic , low-osmolality radiocontrast agents during cardiac angiography . METHODS We compared the need to treat patients for adverse reactions and the frequency and severity of specific hemodynamic , systemic , and symptomatic side effects in two groups of patients r and omly assigned to receive either ionic , high-osmolality or nonionic , low-osmolality radiocontrast material , and also in 366 patients who could not be r and omized . RESULTS Treatment for adverse events was required in 213 of 737 patients who received high-osmolality contrast agents ( 29 percent ) but in only 69 of 753 patients who received nonionic agents ( 9 percent ) ( 95 percent confidence interval for the percent difference , 15.9 to 23.6 percent ) . Hemodynamic deterioration and symptoms also occurred more often in the high-osmolality group , as did severe or prolonged reactions ( 2.9 percent , as compared with 0.8 percent in the nonionic group ; P = 0.035 ) . The severe reactions were largely confined to patients with severe cardiac disease . Multivariate analysis showed that the presence of severe coronary disease and unstable angina were predictors of clinical ly important adverse reactions . If all the patients in our r and omized trial had been given nonionic contrast material , the incremental cost per procedure would have been $ 89 . CONCLUSIONS Nonionic , low-osmolality contrast material is better tolerated during cardiac angiography than ionic , high-osmolality contrast material . Since cost constraints may prevent the universal use of nonionic contrast material , its selective use in patients with severe cardiac disease could be considered Radiographic contrast media ( CM ) can induce renal failure and this may serve as an experimental model of acute renal failure ( ARF ) . One vasoactive factor likely to be involved in ARF is adenosine . In a double-blind , placebo-controlled study we investigated the effect of theophylline ( TP ) , an adenosine receptor antagonist , regarding changes in renal hemodynamics induced by CM . Thirty-nine patients who received 100 ml of a non-ionic low osmolar CM ( iopromide )  were studied for changes in GFR and RPF by continuous inulin and PAH clearance before and until four hours after CM application . Forty-five minutes before the application of CM , patients were r and omized and received either theophylline ( 5 mg/kg body wt ) or the vehicle and placebo ( saline ) intravenously in a blinded manner . We additionally measured the creatinine clearance on the day before and two days after CM application . Sodium excretion , N-acetyl-beta-glucosaminidase ( NAG ) excretion , plasma renin activity ( PRA ) and aldosterone levels were also measured before and after CM application . Theophylline levels were within the therapeutic range in patients of the theophylline group during and four hours after CM application ( 59.0 + /- 10.6 mumol/liter and 40.1 + /- 10.9 mumol/liter ) . GFR , measured by inulin clearance significantly declined under CM application in patients without TP application ( N = 19 ; 88 + /- 40 to 75 + /- 32 ml/min/1.72 m2 ; P < 0.01 ) . In the group of patients receiving theophylline ( N = 18 ) the GFR remained constant ( 75 + /- 26 vs. 78 + /- 33 ml/min/1.72 m2 ) . ( ABSTRACT TRUNCATED AT 250 WORDS BACKGROUND Radiographic contrast media ( CM ) application causes a decline in renal function , especially in patients with pre-existing renal dysfunction . In addition to hydration , several vasodilating substances have been evaluated for their ability to prevent renal damage after CM application . In a prospect i ve , double-blind , placebo-controlled study we investigated the effect of the oral administration of theophylline , an adenosine receptor antagonist , on changes in renal haemodynamics and tubular injury induced by CM in well-hydrated patients with mild-to-moderate renal insufficiency . METHODS We studied 80 patients with pre-existing chronic renal insufficiency ( creatinine > 1.5 mg/dl ) who received more than 100 ml iopromide .  Hydration ( either oral or intravenous ) started at least 24 h before and lasted until 24 h after CM application . In addition , patients were r and omly assigned to receive either theophylline ( 810 mg daily ) or placebo .  Serum creatinine and creatinine clearance were measured before and for 3 days after CM application . Urine was collected to measure N-acetyl-beta-glucosaminidase ( NAG ) enzymuria for the same period . Sixty-four patients completed the entire study protocol  ( theophylline , n = 35 and placebo , n = 29 ) . RESULTS During the study period serum creatinine concentration and creatinine clearance did not change significantly in either group . Acute renal failure ( increase of serum creatinine of at least 0.5 mg/dl ) could be observed in two patients from the theophylline group ( 5.7 % ) and one from the placebo group ( 3.4 % ) . The increase in NAG excretion reached statistical significance ( P < 0.05 ) in the placebo group on days 2 and 3 after CM application . CONCLUSIONS Our results indicate a role for adenosine in CM-induced tubulotoxicity . However , the glomerular filtration rate is preserved by hydration alone in these patients . The application of theophylline did not bring an additional benefit . The use of adenosine antagonists may be beneficial in patients where sufficient hydration may be impossible or in patients with a concomitant decrease in renal blood flow ( e.g. congestive heart failure ) Contrast media can lead to renal impairment that results in longer hospitalization and increased mortality . Adenosine is a crucial mediator of contrast-induced nephropathy ( CIN ; an increase in serum creatinine of > or=0.5 mg/dl within 48 hours ) . Therefore , it was the purpose of our study to investigate whether the adenosine antagonist theophylline reduces the incidence of CIN after coronary angiography . We also characterized risk factors for CIN after coronary angiography .  One hundred patients with serum creatinine concentrations of > or=1.3 mg/dl r and omly received 200 mg IV theophylline or placebo 30 minutes before coronary angiography ( amount of contrast medium > or=100 ml ) . Patients who received theophylline and the controls were comparable with regard to baseline creatinine levels ( means + /- SD ) ( 1.65 + /- 0.41 vs 1.72 + /- 0.69 mg/dl ) and the amount of contrast medium received ( 235 + /- 89 vs 261 + /- 139 ml ) . Theophylline significantly reduced the incidence of CIN ( 4 % vs 20 % , p = 0.0138 ) . With placebo , creatinine significantly increased at 12 ( 1.82 + /- 0.79 mg/dl , p = 0.0057 ) , 24 ( 1.90 + /- 0.86 mg/dl , p = 0.0001 ) , and 48 hours ( 1.90 + /- 0.89 mg/dl , p = 0.0007 ) after administration of contrast medium . With pretreatment with theophylline , mean creatinine only increased 24 hours after contrast medium administration ( 1.70 + /- 0.40 mg/dl , p = 0.029 ) , but was stable 12 hours ( 1.65 + /- 0.43 mg/dl , p = 0.99 ) and 48 hours after contrast medium administration ( 1.65 + /- 0.41 mg/dl , p = 0.99 ) . The following parameters were significantly associated with contrast-induced renal impairment : Cigarroa quotient > 5 ( contrast medium [ milliters ] x serum creatinine/body weight [ kg ] ) , elevated troponin T , > 300 ml of contrast medium , and emergency angiography . In conclusion , theophylline reduces the incidence of CIN in patients with chronic renal insufficiency undergoing coronary angiography . It should be used especially in patients receiving large amounts of contrast medium , and in patients with a Cigarroa quotient of > 5 and /or elevated troponin T levels BACKGROUND Various strategies for the prevention of contrast-induced nephropathy ( CN )  have been studied , with conflicting results . Adenosine may play an important role in the pathogenesis of CN . This study prospect ively assessed the role of oral theophylline in the prevention of CN . METHODS We r and omized into two groups 70 patients with diabetes mellitus who were undergoing coronary angiography ( CAG ) with high-osmolar contrast media .  Group I ( n=35 ) underwent routine CAG , and group II ( n=35 ) received oral theophylline 200 mg b.d . 24 h before and for 48 h after CAG .  Serum Na(+ ) , K(+ ) , blood urea nitrogen ( BUN ) , creatinine , osmolality , glomerular filtration rate ( GFR ) and urinalysis were performed before and after CAG . The (99m)Tc-DTPA-clearance method was used to assess GFR . RESULTS Following angiography , patients in the control group showed a significant rise in serum creatinine ( 1.19+/-0.23 vs 1.44+/-0.32 mg/dl , P=0.003 ) and BUN ( 13.95+/-2.61 vs 17.55+/-3.9 mg/dl , P=0.01 ) along with a fall in GFR ( 85.4+/-14.7 vs 66.85+/-14.8 ml/min , P=0.008 ) . The mean percentage fall in GFR was 35.8 % . There was no significant change in serum creatinine ( 1.16+/-0.18 vs 1.24+/-0.21 mg/dl ) , BUN ( 12.8+/-3.36 vs 14.8+/-2.5 mg/dl ) and GFR ( 86.8+/-15.8 vs 80.3+/-16.0 ml/min ) in those receiving theophylline . No patient in the theophylline group had a > 25 % rise in serum creatinine , compared with 7/35 in the control group ( P=0.017 ) . In the control group , 11/35 ( 31 % ) developed CN , as demonstrated by a > /=25 % fall in GFR , while only one patient in the theophylline group had a fall in GFR ( P=0.004 ) . None of the pre-angiographic variables could predict the development of CN . CONCLUSIONS Following the use of high-osmolar contrast media for routine CAG , CN may develop in 31 % of diabetic patients . Patients who received prophylactic oral theophylline had a significantly lower risk of CN than those who did not Abstract . Objective : To investigate whether the adenosine-antagonist theophylline reduces the incidence of contrast-induced nephropathy ( CIN ) . Design and setting : Prospect i ve , comparison to series of patients at similar risk of CIN in a university hospital medical ICU . Patients : 78 ICU patients with at least one risk factor for CIN undergoing 150 consecutive contrast examinations . Interventions : Administration of 200 mg theophylline/70 kg BW intravenously 30 min before that of 100 ml or more low-osmolarity contrast medium ( CM ) . Measurements and results : Concentrations of serum creatinine and blood urea nitrogen ( BUN ) , urine volume , fluid balance , and the incidence of CIN [ increase in creatinine ≥0.5 mg/dl ( = 44.2 µmol/l ) within 48 h ] were monitored for 48 h. Despite the large number of risk factors ( 6.8 per patient ) including a high dose of CM ( 169.4 ml ) , impaired renal function ( 51 % ) , diabetes ( 38 % ) , aminoglycosides ( 61 % ) , vancomycin ( 53 % ) , catecholamines ( 52 % ) , creatinine concentrations were not increased 24 h ( 1.40±0.92 mg/dl ) or 48 h ( 1.38±0.88 mg/dl ) after CM [ 1.47±1.0 mg/dl ( = 130±88 µmol/l ) ] vs. baseline . The fluid balance was not different before ( + 3 ml/h ) and after CM ( –9 ml/h ) . The urine volume slightly increased after CM and theophylline (  
    Output:
    
Theophylline may reduce the incidence of CIN with an efficacy that is perhaps comparable to that reported in studies of N-acetylcysteine .