Contrast nephrotoxicity: a randomized controlled trial of a nonionic and an ionic radiographic contrast agent

Suppression of renal vein renin profiles by mannitol prophylaxis: implications in the evaluation of renovascular hypertension

Renal arteriography with concomitant renal vein renin profiling remains the diagnostic standard for evaluating the anatomic and physiologic significance of stenotic renal artery lesions in hypertensive patients. False-negative renal vein renin profiles with failure of lateralization in patients with anatomically apparent high-grade stenosis complicate the diagnostic process. Mannitol is frequently administered prophylactically to minimize the risk of dye nephropathy in these patients. Yet, the potential effects of mannitol on renal vein renin profiling in man have not been previously reported. Seven patients with renovascular hypertension were studied prospectively to determine changes in renal vein renin profiles before and after mannitol prophylaxis. Despite captopril stimulation, all patients demonstrated significant renin suppression leading to the loss of renin lateralization in patients with unilateral renovascular hypertension. In 60% of the patients, renal vein renin ratios fell to below the standard 1.5 to 1 ratio after mannitol infusion. In patients with bilateral renovascular disease, the least stenotic side suppressed completely, while the more stenotic side suppressed partially. Percent suppression analysis showed a mean suppression of 56.8% on the stenotic side versus 8.2% on the noninvolved side (P less than 0.002). In every study, suppression equaled or exceeded 32% on the involved side and was less than this on the noninvolved side. Thus, the degree of renin suppression following mannitol infusion may prove to be an important tool in the diagnosis of clinically significant stenotic lesions. The mechanism of mannitol-induced suppression remains undefined, but appears independent of volume expansions or dilutional effects. The inhibitory effects of mannitol on renin profiles can obscure the diagnosis of underlying renovascular hypertension.

ACC/AHA guidelines for cardiac catheterization and cardiac catheterization laboratories. American College of Cardiology/American Heart Association Ad Hoc Task Force on Cardiac Catheterization

It is evident that the practice of cardiac catheterization has undergone, and continues to undergo, marked change. Most prominent are the recent very rapid proliferation of catheterization laboratories in general and the development of newer types of catheterization laboratory. No uniform definitions exist for these newer laboratories, so meaningful communication is difficult. The new settings are of particular concern because their location, mobility, organization, and ownership raise questions about the quality of patient care. Most difficult to address are the questions about patient safety and physician conflict of interest. There are no objective data in peer-reviewed literature to support the reported safety and cost savings of these newer settings. Through deliberations, surveys, interviews, and correspondence with the cardiology community embraced by the ACC and the AHA, the task force generally found that in freestanding catheterization laboratories, access to emergency hospitalization may be delayed, and appropriate oversight may be lacking. Additionally, opportunities for self-referral may be fostered and the perception of commercialism and entrepreneurial excess in practice created. All of these problems must be avoided. The growth and development of some freestanding facilities, particularly the mobile laboratories, do not seem to have been driven by an increased need in remote communities or for temporary support but rather almost exclusively by a desire to capture market share. Accordingly, a series of definitions, guidelines, and recommendations for the laboratories as well as for patient selection has been developed. The consensus was that a very restrictive and cautious attitude to the newer settings is appropriate at this time. The justification for development or expansion of cardiac catheterization services must be patient need. Documentation of this need must be based on objective estimates of the number of patients with known or suspected cardiac disease who meet generally accepted indications for laboratory study. Concerns about the lack of data from prospective clinical trials of patient safety in such a group necessitate a very cautious attitude toward any new catheterization services, in particular those without in-house cardiac surgical support. In view of the lack of appropriately controlled safety and need data for hospital-based, mobile, or freestanding laboratories operating without on-site (accessible by gurney) cardiac surgery facilities, the task force reaffirms the position that further development of these services cannot be endorsed at this time. In addition, there is reason for major concern that such proliferation in catheterization services may contribute to increasing costs and troubling ethical questions.

Contrast agents for cardiac catheterization: conceptions and misconceptions

Ionic and nonionic contrast materials are similarly efficacious in providing excellent images with minimal risk to the patient. In comparison with ionic media, the nonionic agents produce minor alterations in intracardiac and peripheral pressures as well as in electrocardiographic intervals and morphology. In addition, nonionic media are less often associated with undesirable symptoms, such as flushing and vomiting. At the same time, ionic and nonionic media are accompanied by a similar incidence of nephrotoxicity, serious arrhythmias, and death. Finally, nonionic contrast material is substantially more expensive than ionic media. In light of this marked difference in cost, one could argue that nonionic media should be reserved for "high-risk" patients, that is, those with a history of a serious adverse reaction to ionic contrast media and those in whom contrast-induced hypotension would be particularly deleterious.

Failure to demonstrate contrast nephrotoxicity

OBJECTIVE

We tested the hypothesis that there is no difference in the change in serum creatinine level following computed tomography (CT) between those given high osmolality contrast, low osmolality contrast and those not receiving contrast material.

DESIGN

Patients were assigned according to current radiological practice to receive one or other type of radiocontrast material or to have a scan without intravenous contrast (plain scan).

SETTING

The CT unit of Royal Newcastle Hospital, a tertiary referral institution.

PATIENTS

Of 3188 inpatients having a CT scan between June 1988 and December 1989, 1041 patients were eligible (having a first scan in "office hours" outside holiday periods, not due for imminent discharge, aged 18 years or more and not presenting to the Intensive Care Unit or with acute trauma). Twenty-five patients were excluded as baseline measures of renal function were missing and 132 subjects were lost to follow-up, leaving 884 study subjects.

INTERVENTIONS

CT scans using high osmolality, low osmolality or no contrast (plain scan).

MAIN OUTCOME MEASURE

Renal impairment as defined by a maximal increase in the serum creatinine level of greater than or equal to 50% or greater than 0.04 mmol/L from the baseline level on at least one of the subsequent four days.

RESULTS

Renal impairment was seen in 4% (12 of 292), 12% (23 of 187) and 4% (16 of 405) of patients given high osmolality, low osmolality or no contrast respectively. Age and the baseline level of serum creatinine were independent predictors of the development of renal impairment (P = 0.04 and 0.02 respectively) and those given low osmolality contrast were 3.2 times (95% confidence interval, 1.6-6.3) more likely to develop renal impairment than those given no contrast. There was no excess risk with the use of high osmolality contrast compared to no contrast (odds ratio, 1.06; 95% confidence interval, 0.5-2.3). Selection factors (sicker patients being given low osmolality contrast) are likely to have accounted for the excess risk in the low osmolality group as mortality in hospital was higher in this group than in the others. The 51 patients who developed renal impairment (cases) were matched for age, sex, type of contrast and pre-existing renal impairment with up to three controls (150 patients in total). Cases were more likely to have had a blood transfusion (odds ratio, 6.40; 95% confidence interval, 2.18-22.63) or surgery (odds ratio, 3.22; 95% confidence interval, 1.19-7.65) than controls.

CONCLUSIONS

Confounding by other factors which impair renal function is likely to explain previous suggestions of an effect of radio-contrast material on renal function. There does not appear to be a risk of renal impairment from the use of high osmolality radiocontrast material (although a small effect or an effect in particular subgroups cannot be excluded by our study). Fear of causing or exacerbating renal damage should not be a reason to use low osmolality contrast material, nor should it be a reason for with-holding contrast studies.

Drug-induced renal toxicity. Help in recognizing offending agents

Drug-induced kidney disease is common, especially in hospitalized patients, and prompt recognition of the various nephrotoxic syndromes is important because many are reversible. Risk factors should be assessed before patients are given an agent that may cause acute renal failure (eg, nonsteroidal anti-inflammatory drug, aminoglycoside antibiotic, angiotensin-converting enzyme inhibitor, radiocontrast agent). Discontinuation of the responsible drug is often the only necessary therapy.

Haemodynamic effects of water-soluble contrast media on the isolated perfused rat kidney

The precise mechanism underlying the nephrotoxicity of radiocontrast media remains ill defined. In this study we have examined the direct effect of a wide range of low- and high-osmolar water-soluble contrast media (WSCM) on the vascular resistance of the isolated perfused rat kidney (IPRK). Water-soluble contrast media led to a significant fall in the renal perfusate flow and an increase in the renal vascular resistance (RVR). The magnitude of these haemodynamic changes was independent of the osmolality of the tested agents. This study shows a direct effect of WSCM on the vascular resistance of the isolated perfused rat kidney.

Choice of contrast agents for cardiac angiography: review and recommendations based on clinically important distinctions

Low osmolal contrast agents (LOCA) are measurably superior to high osmolal contrast agents (HOCA) in a number of properties. However, LOCA are substantially more expensive than HOCA, and universal use of LOCA for cardiac angiography would strain the health care budget. Therefore, the choice to use LOCA in place of HOCA should be based on clinically important differences. Review of available published data suggests that HOCA can be used safely and effectively for cardiac angiography in patients with mild or moderately severe heart disease. When HOCA are used, those that do not bind calcium should be chosen as they cause fewer clinically important adverse reactions than those that do bind calcium. Use of LOCA may offer added safety in high risk patients, although to date, this conclusion has not been proved with clinical experience. Nonionic LOCA may be safer to use than ionic LOCA.

The use of ionic and nonionic contrast agents and the effects of hydration in the post cardiac transplant patient with moderate renal insufficiency

To determine the effects of ionic (diatrizoate) and nonionic (iopamidol) contrast and of hydration, 90 asymptomatic cyclosporine-treated cardiac transplant patients with moderate renal insufficiency (serum creatinine greater than or equal to 1.5 mg/dL) undergoing cardiac catheterization were evaluated. All patients were hydrated with intravenous fluid (5% dextrose and 0.5 normal saline) over a twelve-hour period prior to catheterization and with oral fluids thereafter. Thirty patients received iopamidol (Group I) and 60 were given diatrizoate (Group II). Renal function was determined the day before and after catheterization in all patients of Group I and in 30 patients of Group II (Group IIa). In the remaining 30 patients of Group II renal function was also determined before contrast administration (Group IIb). The dose of dye was similar in all groups (I: 139 +/- 55 mL, IIa: 140 +/- 58 mL, IIb: 128 +/- 38 mL). There was a significant decrease in BUN (I: 41 +/- 10 to 33 +/- 8 mg/dL [p less than 0.005], IIa: 42 +/- 9 to 33 +/- 8 mg/dL mg/dL [p less than 0.001], IIb: (44 +/- 12 to 34 +/- 10 mg/dL [p less than 0.005]) and a small decrease in serum cratinine after catheterization (I: 2.0 +/- 0.3 to 1.9 +/- 0.3 mg/dL, IId: 2.0 +/- 0.3 to 1.9 +/- 0.3 mg/dL, IIb: 2.1 +/- 0.4 to 1.8 +/- 0.4 mg/dL [p less than 0.005].(ABSTRACT TRUNCATED AT 250 WORDS)

A randomized comparison of the nephrotoxicity of iopamidol and diatrizoate in high risk patients undergoing cardiac angiography

Three hundred seven high risk patients with renal impairment (serum creatinine greater than or equal to 1.5 mg/dl) were randomized in a double-blind manner to either iopamidol (a nonionic, low osmolar radiocontrast agent) or diatrizoate (a conventional radiocontrast agent) at cardiac angiography with subsequent follow-up study of renal function. Baseline clinical and angiographic variables were similar in the iopamidol (n = 155) and diatrizoate (n = 152) groups. Change in renal function after angiography was less pronounced with iopamidol compared with diatrizoate as measured by mean ( +/- SD) increase in 24 h serum creatinine (0.11 +/- 0.2 versus 0.22 +/- 0.26 mg/dl, p less than 0.001), mean maximal increase in serum creatinine (0.2 +/- 0.44 versus 0.38 +/- 0.73 mg/dl, p less than 0.0001) and percent of patients with a maximal increase in serum creatinine greater than 0.5 mg/dl (8% versus 19%, p less than 0.01). Such differences could not be documented in diabetic patients using insulin. There was no significant difference between agents in the number of patients developing clinically severe acute renal dysfunction. It is concluded that iopamidol is less nephrotoxic than diatrizoate in high risk patients at cardiac angiography. However, the difference in nephrotoxicity is small, of no major clinical significance in the majority of high risk patients and could not be documented in insulin-using diabetic patients. Iopamidol may be the preferred agent in certain patients with advanced renal impairment, but further study is warranted.

Ioversol for intravenous urography: a comparison study

A new nonionic, low-osmolar iodinated contrast media, ioversol, was compared with another low-osmolar, nonionic contrast media, iohexol, in 80 patients undergoing intravenous urography. There were 40 patients in each contrast group. Patients were assessed for changes in vital signs, patient tolerance (heat and pain), and other adverse effects. Double-blind evaluation was also performed for comparison of the urogram image quality. There were no severe, life-threatening reactions for either contrast group. Ten patients (25%) receiving ioversol and seven (17.5%) receiving iohexol perceived body heat related to the injection of contrast material. Two patients (5%) in each group experienced mild nausea. Two patients (5%) of each group experienced noted unpleasant taste, and two patients (5%) of the iohexol group complained of headache. Vital signs remained stable without significant change in both groups, and image quality was considered equivalent. The results indicate that the two contrast agents are equivalent in image quality, safety, and incidence of adverse effects.

Contrast nephropathy in azotemic diabetic patients undergoing coronary angiography

PURPOSE

To evaluate the incidence of, risk factors for, and outcome of contrast nephropathy in azotemic diabetic patients undergoing coronary angiography.

PATIENTS AND METHODS

Fifty-nine insulin-dependent diabetics with a mean serum creatinine level of 522 mumol/L (5.9 mg/dL) underwent coronary angiography as part of a pretransplant evaluation. Twenty-four azotemic diabetics undergoing inpatient evaluation not including angiography for transplantation formed the control group. Serum creatinine measurements obtained at baseline and after radiocontrast exposure were compared in patients and control subjects. Risk factors for contrast nephropathy were evaluated in patients with a 25% or greater increase in serum creatinine.

RESULTS

Serum creatinine was significantly elevated 24 hours after radiocontrast exposure in patients (557 +/- 141 mumol/L versus 522 +/- 141 mumol/L, mean +/- SD; p less than 0.001) but not in controls. Seven patients required dialysis within 6 days of coronary angiography and two additional patients required dialysis within 14 days. Contrast nephropathy, defined as a serum creatinine increase of greater than 25% when measured 48 hours after radiocontrast exposure, occurred in 50% of patients and no controls. Univariate analysis of risk factors for contrast nephropathy revealed a significant association with dye quantity (p = 0.002), mean arterial pressure less than 100 mm Hg (p = 0.02), and ejection fraction less than 50% (p = 0.04). Stepwise logistic regression verified the independence of dye quantity and low mean arterial pressure but not low ejection fraction as risk factors for contrast nephropathy. Follow-up serum creatinine values were not significantly different in patients and control subjects.

CONCLUSIONS

Azotemic patients with diabetes are at high risk of developing contrast nephropathy even when less than 100 mL of radiocontrast agent is used. The acute renal failure is reversible but precipitates the need for short-term dialysis in some patients. Radiocontrast quantity is an important risk factor not previously noted. The incidence of contrast nephropathy can be minimized by using less than 30 mL of radiocontrast agent.

Selection of a contrast agent in the cardiac catheterization laboratory

The evolution of contrast material for intravascular use has been directed toward the development of better-tolerated agents. Currently, a variety of such "dyes" are available for coronary angiography and left ventriculography. Considerable animal and human investigation suggests that significant differences exist between the families of contrast agents that relate to patient tolerance. The newer low osmolality agents (especially the nonionic agents) produce less perturbation of the homeostatic state, which is clinically manifested by a lessened incidence of side effects, including those of a hemodynamic and electrophysiologic nature. While controversy continues over the cost/benefit ratio of the low osmolality contrast agents compared to traditional high osmolality agents, the former are rapidly becoming the community standard for diagnostic and especially therapeutic cardiologic procedures. Accepting the advantages of the low osmolality contrast agents, differences between the ionic dimers and the nonionic agents have been examined. Both experimental and clinical data suggest superiority of the nonionic agents. Although controversy still surrounds the issue of thromboembolism with the nonionic agents, accumulating evidence fails to support a clinically significant relation. The choice of contrast material is the responsibility of the invasive cardiologist. While the benefits of low osmolality agents are most obvious in high-risk patients, experience with large-scale intravenous studies suggests that the choice of contrast agent is a better discriminator of adverse reaction than is preprocedural risk stratification.

Randomized comparison of the cost and effectiveness of iopamidol and diatrizoate as contrast agents for cardiac angiography

To evaluate the effectiveness and cost of low osmolarity, nonionic contrast agents for cardiac angiography, 443 patients were randomized to receive either iopamidol or diatrizoate. All adverse events that occurred within 24 h of the procedure were recorded prospectively by study personnel and classified according to previously determined criteria. Major events were defined as life threatening or requiring a procedure to treat, or both. Costs of the catheterization procedure, pharmacy, hospital laboratory and treatment of adverse events were determined on the basis of actual resource use. A total of 20 patients (8.5%) had major and 143 (61%) had minor adverse events with diatrizoate use; 10 patients (4.8%) had major and 53 (25%) had minor adverse events with iopamidol (p = 0.12 for major events; p less than 0.001 for total events). Most adverse events were treated fairly easily and inexpensively. The median overall cost was $186 higher for patients after iopamidol use compared with diatrizoate (p less than 0.0001), but all costs except the cost of the contrast agent were not significantly different between the two groups. Thus, patients who received iopamidol for cardiac angiography had a significantly lower rate of adverse events than those who received diatrizoate, but this difference was achieved at a considerably high overall cost.

High-dose contrast agent administration during complex coronary angioplasty

To examine the necessity and consequences of high-dose contrast media administration during coronary angioplasty, the records of 730 consecutive patients over a 6-month period were reviewed. The 54 patients (7%) requiring contrast agent doses greater than or equal to 400 ml were examined in detail. The mean contrast dose in this group was 496 +/- 76 ml (range 400 to 785 ml). Their mean age was 63 +/- 11 years (range 36 to 83 years), 10 patients had diabetes mellitus (19%), and four patients had a baseline creatinine level greater than or equal to 1.5 mg/dl (7%). Following coronary angioplasty, the serum creatinine rose from 1.1 +/- 0.2 to 1.2 +/- 0.3 (p = 0.08). The creatinine rose greater than or equal to 0.5 mg/dl in six patients (11%) and greater than or equal to 1.0 mg/dl in one patient (2%). Five of these six patients had either diabetes mellitus, baseline renal insufficiency, or both. Oliguria was not observed. The most important procedural factors contributing to the high doses of contrast media were multilesion and multivessel angioplasty in 96% and 83% of patients, respectively, prior bypass surgery in 52%, and combined diagnostic cardiac catheterization and angioplasty in 13%. Thus renal dysfunction following high-dose contrast agent administration during complex coronary angioplasty is infrequently associated with nephrotoxicity. Whenever possible, contrast doses in patients with diabetes mellitus and renal insufficiency should be minimized.

Carbon dioxide digital subtraction arteriography: a pilot study

To investigate the diagnostic value of carbon dioxide arteriograms in patients with peripheral vascular disease, ten patients in whom standard contrast arteriography was contraindicated underwent carbon dioxide digital subtraction arteriography. Lower extremity ischemia or severe hypertension with renal insufficiency were the indications for arteriography. Standard contrast arteriography was precluded by chronic nondialysis-dependent renal insufficiency, severe congestive heart failure or contrast hypersensitivity. All critical arterial segments were well visualized with the exception of the infrapopliteal arterial tree in three patients. Adequate imaging of this segment required the addition of 20 cc of dilute nonionic contrast. Guided by carbon dioxide digital subtraction arteriography, four percutaneous transluminal angioplasties and three reconstructive procedures were successfully performed. One patient did not have surgically reconstructible disease and two had renal arteries without critical stenoses. Renal function transiently deteriorated in one patient who received 20 cc of nonionic contrast. No adverse events occurred due to carbon dioxide. Clinically useful diagnostic arteriograms are possible using carbon dioxide as the contrast agent.

Intravenous urography with iopamidol in children with reflux and obstructive nephropathy: effects on glomerular and tubular functions and the renin-angiotensin-aldosterone system

Twenty-seven children [2 with chronic renal failure (CRF)] with reflux or obstructive nephropathy underwent intravenous urography with iopamidol 370, a nonionic contrast medium 1 (CM), osmolality 796 mosmol/kg, for renal growth evaluation. Mean iopamidol dosing was 1.69 ml/kg (range 1.22-2.42); the 2 children with CRF received 2 and 2.42 ml/kg respectively. One hour after infusion a significant decrease in haematocrit, haemoglobin, plasma sodium (Na+), chloride (Cl-), renin activity and aldosterone was observed, consistent with a possible plasma volume expansion due to the slightly hypertonic CM. At the same time there was a significant increase in fractional excretion of Na+, Cl- and potassium, probably due to the haemodynamic effects and tubular response to a substance acting as on osmotic diuretic. The -24 to +48 h monitoring of albuminuria, beta-2-microglobulin excretion, and in 4 children excretion of N-acetyl-beta-glucosaminidase and alanine-aminopeptidase did not show any relevant nephrotoxicity. No untoward effect of clinical relevance was observed.

Effects on renal hemodynamics and tubular function of the contrast medium iohexol in renal patients

Renal function was assessed in 20 (11 female and 9 male, age 21-76 years, mean 53) renal patients with a creatinine clearance 25-145 ml/min, mean 95, to evaluate the effects of iohexol, a non-ionic low-osmolar contrast medium. Intravenous urography was performed in 16 patients and computed body tomography in 4, using a dose of iohexol ranged between 0.6-3.3 (mean 1.17) g/kg b.w. Different parameters of renal function were determined in the week preceding and 1, 3 and 5 days after the administration of iohexol. The principal renal effect of iohexol was an increase of urinary alanine aminopeptidase, gamma-glutamyltransferase, lactate dehydrogenase, alkaline phosphatase and N-acetyl-beta-D-glucosaminidase. The maximum increase of enzymuria was observed on day 1 after the administration of iohexol. In most cases enzymes returned to base-line values within 3 days. No relevant variation of renal hemodynamics (glomerular filtration rate and effective renal plasma flow) was observed after iohexol. In conclusion, iohexol can increase of urinary enzymes, but the effect is rapidly reversible and is not accompanied by a clinically significant impairment of renal hemodynamics.

Comparison of toxicity of radiocontrast agents to renal tubule cells in vitro

We have previously reported that radiocontrast agents induce direct renal tubule cell toxicity in vitro. The observed toxic effects were markedly potentiated by concomitant hypoxia. In addition, we have reported that the ionic radiocontrast agent diatrizoic acid is more toxic than the nonionic radiocontrast agent iopamidol in this system. Using suspensions enriched in rabbit renal proximal tubule segments, we compared the direct toxicities of the ionic dimeric ioxaglic acid to the nonionic monomeric compound iopamidol. Toxicity was assessed by comparing tubule potassium and calcium content, ATP levels, and respiratory rates after exposure to clinically achievable concentrations of radiocontrast agents. Ioxaglate (25 mM) produced significant declines in tubule cation content and respiratory rate with 30 min of hypoxia followed by 60 min of reoxygenation compared to molar-equivalent concentrations of iopamidol under similar conditions. Meglumine, a cationic compound frequently present in ionic contrast agent solutions, and ioxaglate tubule toxicity was additive. Iopamidol and ioxaglate exhibited similar tubule cell toxicity when comparison was based on iodine content. These experimental results suggest that the intrinsic nephrotoxic potential of ioxaglic acid is greater than that of iopamidol on a molar basis, but that the nephrotoxic potential of the two radiocontrast agents is similar when comparison is based upon iodine content.

Renal failure following radiologic procedures

Radiologic procedures that employ intravascular contrast material with or without angiography may lead to renal failure. In procedures that use intravenous contrast alone, the mechanism of renal injury is not precisely known, but direct toxicity to renal tubular cells is likely to be a major factor. Ionic and nonionic contrast agents are both capable of causing this adverse reaction. Renal failure occurring during angiography may also be secondary to the effects of radiocontrast, but the additional possibility that micro cholesterol emboli have been dislodged from atheroma located on the intima of large vessels must be considered. The acute or subacute development of renal failure in the presence of skin changes (livido reticularis), hypertension, multiple organ failure or dysfunction, and a fatal outcome favors the later diagnosis.

Contrast-associated nephropathy

Contrast nephropathy can be defined as an acute impairment of renal function that follows exposure to radiocontrast materials and for which alternative explanations for renal impairment have been eliminated. Based on reported studies, the incidence of contrast associated nephropathy (CAN) varies from 0 to 22%. This wide variation can be traced to differences in study design and the criteria used to designate significant renal impairment. Irrespective of the exact incidence, 2 defined risk factors have been identified: preexisting renal disease and diabetes mellitus. Whereas preexisting renal insufficiency is the single most influential risk factor for CAN, when diabetes coexists the incidence approaches 100%. The clinical presentation of CAN is distinct, having a temporal relation between the performance of the contrast study in the high-risk patient and the onset of an increase in serum creatinine levels within the next 24 hours. Serum creatinine values greater than 50% of baseline or rising 1 mg/dl or more is diagnostic. The peak serum creatinine level occurs within 3 to 5 days of the contrast study and oliguria is associated in approximately 30% of the cases. Monitoring serum creatinine is the most useful clinical procedure in high-risk patients after angiography. At least 5 potential pathophysiologic mechanisms of CAN have been proposed: interference with renal perfusion, altered glomerular perm-selectivity, direct tubular injury, intraluminal obstruction, and immunologic mechanisms. Support for each mechanism, either singularly or in combination, can be found in published reports; however, none has achieved universal acceptance. The single most important clinical axiom regarding the prevention and management of CAN is, "Always use the least invasive diagnostic procedure available."(ABSTRACT TRUNCATED AT 250 WORDS)

Low-osmolality contrast media: a current perspective

Intravascular radiographic contrast media play a major role in diagnostic imaging. Recently, low-osmolality contrast media (LOCM) have become available in the United States. Because of their lower osmolality, these new agents cause fewer undesirable physiologic effects and fewer adverse reactions than do conventional agents after intravascular administration. Unfortunately, the cost of LOCM is substantially higher than the cost of conventional contrast media. Appropriate use of these newer, more expensive contrast agents must be based on a thorough knowledge and understanding of their chemistry, physiologic features, and relative safety. Some questions remain about these new agents. Further studies are needed to determine the nephrotoxicity of LOCM relative to that of conventional agents. In addition, LOCM have less anticoagulant capacity than do the conventional media; therefore, clotting may occur when the LOCM and blood mix in syringes and small catheters. This potential decrease in anticoagulation and its clinical implications should be further investigated. Finally, the mortality rate associated with use of LOCM needs to be determined in future studies in large numbers of patients.

Dosing of contrast material to prevent contrast nephropathy in patients with renal disease

PURPOSE

Contrast-induced renal dysfunction has been reported to occur in 15% to 42% of patients with underlying azotemia, but there is disagreement as to whether its incidence is reduced by limiting the amount of contrast material. To adjust the amount of contrast material to the severity of azotemia, we have utilized the following formula to calculate a contrast material "limit" in patients with renal disease: Contrast material limit = (formula; see text)

PATIENTS AND METHODS

Over a 10-year period, 115 patients (53 men, 62 women, aged 61 +/- 11 [mean +/- SD] years) with renal dysfunction (baseline serum creatinine level greater than or equal to 1.8 mg/dL) underwent cardiac catheterization and angiography, after which the level of serum creatinine was measured daily for five days. The amount of contrast material that was given adhered to the limit in 86 patients (Group I) and exceeded it in 29 (Group II).

RESULTS

Contrast-induced renal dysfunction (an increase in serum creatinine greater than or equal to 1.0 mg/dL) occurred in two (2%) patients in Group I and in six (21%) patients in Group II (p less than 0.001). Of the 48 patients with concomitant diabetes mellitus, the contrast limit was surpassed in 16, six (38%) of whom had contrast nephropathy. Only two of the 32 (6%) diabetic patients in whom the contrast limit was not exceeded had contrast nephropathy (p less than 0.001).

CONCLUSIONS

Thus, contrast-induced renal dysfunction occurs infrequently if the amount of contrast material is limited in accordance with the degree of azotemia. Diabetic patients have a high incidence of contrast nephropathy, particularly when they receive an excessive amount of contrast. In patients with diabetes and renal impairment, it may be preferable to perform angiography as a staged procedure or to utilize alternative (non-contrast) techniques to obtain the desired information rather than to exceed the prescribed contrast limit.

Acute renal failure associated with ioxaglate, a low-osmolality radiocontrast agent

Iodinated radiocontrast agents may cause acute renal failure, particularly in patients with preexisting renal failure, heart failure, or diabetes. The low-osmolality contrast agents cause less hypersensitivity, but substantial nephrotoxicity has not been noted. We report three high-risk patients who developed acute renal failure after one of these new agents, ioxaglate, was administered for coronary arteriography and ventriculography. The renal failure was severe: two of the patients required dialysis. We could find no previously reported cases of acute renal failure associated with ioxaglate. Despite their theoretical advantages, the low-osmolality contrast agents may cause acute renal failure in patients who are at risk and should be used with the same precautions as the conventional agents.

Acute renal failure caused by low-osmolar radiographic contrast media in patients with diabetic nephropathy

Four patients reacting with acute renal failure despite using low osmolar contrast media are reported. They all had diabetic nephropathy and renal insufficiency. A retrospective study of 75 consecutive patients examined with angiography showed that 13% had both of these two risk factors.