Prevention of radiographic-contrast-agent-induced reductions in renal function by acetylcysteine

Effectiveness of oral N -acetylcysteine in a rat experimental model of asthma

Oxidative stress appears to be relevant to asthma pathogenesis. Therefore, the effectiveness of the antioxidant N -acetylcysteine was examined on antigen-induced pulmonary responses in sensitized Brown-Norway rats. N -acetylcysteine (oral, 1 mmol kg(-1)per day for 7 days before challenge) did not reduce the immediate bronchospasm that followed aerosol antigen exposure but prevented airway hyperreactivity to 5-hydroxytryptamine at 24 h after antigen challenge, and reduced the eosinophils (from 0.178 +/- 0.038 in the absence to 0.064 +/- 0.020 x10(6)cells ml(-1)in the presence of N -acetylcysteine;P< 0.05), and Evans blue dye extravasation in bronchoalveolar lavage fluid. Taurine levels in bronchoalveolar lavage fluid from antigen-challenged rats were higher than control values but treatment with N -acetylcysteine failed to further increase these augmented levels. In conclusion, oral N -acetylcysteine showed beneficial effects in an in vivo model of experimental asthma, which confirm and extend the previous positive findings obtained in other models of lung injury.

A protocol for prevention of radiographic contrast nephropathy during percutaneous coronary intervention: effect of selective dopamine receptor agonist fenoldopam

Radiographic contrast nephropathy (RCN), acute worsening of renal function due to contrast agents, can occur in 15%-40% of patients with baseline renal dysfunction undergoing percutaneous coronary intervention (PCI) and is associated with increased morbidity and in-hospital mortality. The purpose of this study was to evaluate whether the selective dopamine-1 (DA-1) receptor agonist fenoldopam would be beneficial in patients with chronic renal insufficiency (CRI) undergoing PCI and also to design a protocol for prevention of RCN. We analyzed 150 consecutive patients with CRI [baseline serum creatinine (BSCr) +/- 1.5% mg] who underwent PCI and received fenoldopam during and after the procedure, in addition to saline hydration. RCN, defined as > 25% increase of BSCr 48-72 hr after PCI, occurred in 4.7% (n = 7) of 150 PCI patients receiving fenoldopam and 3.5% in diabetics (n = 85) vs. 6.1% in nondiabetics (n = 65; P = NS). No patients required dialysis. The observed 4.7% incidence of RCN with fenoldopam was significantly lower than 18.8% incidence in the historical control group (P < 0.001). Our data suggest that fenoldopam is a useful adjunct in the prevention of RCN during PCI, especially in diabetics.

A(2A) adenosine receptor: a novel therapeutic target in renal disease

Present strategies in the treatment of inflammatory renal injury have focused on developing agents that specifically target individual mechanisms thought to contribute toward the pathogenesis of the disease. Such an approach is hindered by redundancies in the inflammatory cascade, rendering intervention suboptimal. The A(2A) adenosine receptor (A(2A)-AR) is a member of the family of guanine nucleotide binding proteins and has become a focus of major interest primarily because of its ability to broadly inactivate the inflammatory cascade. This review summarizes our present knowledge regarding the molecular biology and pharmacology of A(2A)-ARs as well as the physiological effects of activation of A(2A)-ARs in the kidney. We also review our recent experience in targeting this receptor subtype in abrogating the inflammatory cascade in ischemia-reperfusion injury.

Prophylactic hemodialysis after radiocontrast media in patients with renal insufficiency is potentially harmful

PURPOSE

Acute renal failure induced by contrast media is an important cause of hospital-acquired renal insufficiency. Preexisting renal failure and the dose of contrast media are known risk factors for the development of radiocontrast nephropathy. We performed a randomized trial to test whether radiocontrast nephropathy can be avoided by prophylactic hemodialysis immediately after the administration of contrast media in patients with impaired renal function.

SUBJECTS AND METHODS

Renal function and other parameters, hemodialysis requirement, and relevant clinical events were recorded before and during the 6 days after administration of contrast media in 113 patients with a baseline serum creatinine level >200 microm/L (>2.3 mg/dL). Patients were randomly assigned to either hemodialysis (n = 55) or nonhemodialysis (n = 58) treatment after parenteral low-osmolality contrast media.

RESULTS

The characteristics of the patients in the two groups were similar. Compared with baseline levels, the mean [+/- SD] serum creatinine level decreased at day 1 (277 +/- 95 microm/L), peaked at day 4 (353 +/- 126 microm/L), and returned to baseline at day 6 (327 +/- 119 microm/L, P <0.05 by analysis of variance) after administration of contrast media in the hemodialysis group, whereas in the nonhemodialysis group, no significant changes in mean serum creatinine level were observed. Eleven patients required 1 or more hemodialyses (8 in the hemodialysis group and 3 in the nonhemodialysis group, P = 0.12), 6 of whom (4 vs. 2, P = 0.44) required 3 or more hemodialyses. Clinically relevant events included pulmonary edema (1 vs. 4 patients, P = 0.36), myocardial infarction (2 vs. 2), stroke (2 vs. 0, P = 0.24), and death (1 vs. 1).

CONCLUSIONS

The strategy of performing hemodialysis immediately after the administration of low-osmolality contrast media in all patients with a reduced renal function did not diminish the rate of complications, including radiocontrast nephropathy.

Acetylcysteine for radiocontrast nephropathy

Radiocontrast nephropathy may in part be mediated by generation of reactive oxygen species causing direct toxic damage to renal tubular epithelial cell and renal medullary ischemia. Data from experimental studies indicated that antioxidants, eg, acetylcysteine, may prevent radiocontrast-induced nephropathy. Recently, one prospective, randomized, placebo-controlled study in patients with moderate renal insufficiency confirmed that the prophylactic oral administration of acetylcysteine at a dose of 600 mg twice daily along with hydration prevents the reduction in renal function by a nonionic, low-osmolality radiocontrast agent.

Interleukin-10 inhibits ischemic and cisplatin-induced acute renal injury

BACKGROUND

Acute renal failure (ARF) is caused by ischemic and nephrotoxic insults acting alone or in combination. Anti-inflammatory agents have been shown to decrease renal ischemia-reperfusion and cisplatin-induced injury and leukocyte infiltration. Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine that inhibits inflammatory and cytotoxic pathways implicated in acute renal injury. Therefore, we sought to determine if IL-10 inhibits acute renal injury.

METHODS

The effects of IL-10 were studied in mice following cisplatin administration and bilateral renal ischemia-reperfusion, in a rat model of renal transplantation, and in cultured mouse cortical tubule cells.

RESULTS

IL-10 significantly decreased renal injury following cisplatin administration and following renal ischemia/reperfusion. Delay of IL-10 treatment for one hour after cisplatin also significantly inhibited renal damage. IL-10 and alpha-melanocyte stimulating hormone (alpha-MSH) increased recovery following transplantation of a kidney subjected to warm ischemia. To explore the mechanism of action of IL-10, its effects were measured on mediators of leukocyte trafficking and inducible nitric oxide synthase (NOS-II). IL-10 inhibited cisplatin and ischemia-induced increases in mRNA for tumor necrosis factor-alpha (TNF-alpha), intercellular adhesion molecule-1 (ICAM-1), and NOS-II. IL-10 also inhibited staining for markers of apoptosis and cell cycle activity following cisplatin administration, and nitric oxide production in cultured mouse cortical tubules.

CONCLUSIONS

IL-10 protects against renal ischemic and cisplatin-induced injury. IL-10 may act, in part, by inhibiting the maladaptive activation of genes that cause leukocyte activation and adhesion, and induction of iNOS.

Radiographic contrast media induced nephropathy: experimental observations and the protective effect of calcium channel blockers

Combined acute inhibition of the synthesis of nitric oxide with L-nitroarginine methyl ester (L-NAME) and of prostacycline synthesis with indomethacin predisposes rats to severe renal injury from radiographic contrast media. The reliability of this pharmacological manipulation in the study of radiographic contrast medium induced nephropathy (RCMN) was investigated. Adult male Sprague-Dawley rats were injected with iv L-NAME (10 mg kg(-1)) and iv indomethacin (10 mg kg(-1)) 15 min apart and prior to injection of RCM or normal saline (control group). A dose-dependent reduction in renal function was observed after intravascular injection of the high osmolar RCM diatrizoate (Angiografin, 306 mgI ml(-1)). A significant (p<0.01) increase in serum creatinine (Cr) (from 54.66+/-8.39 micromol l(-1) to 171.96+/-24.49 micromol l(-1) and from 80.95+/-6.73 micromol l(-1) to 204.76+/-16.73 micromol (-1), n=5 per group) was observed 24 h after injection of 6 ml and 8 ml of diatrizoate, respectively. The increase in serum Cr after injection of 8 ml of diatrizoate recovered spontaneously to 80.87+/-8.70 micromol l(-1) 7 days after injection. No significant change in renal function was observed in the control group (n=5) receiving 8 ml kg(-1) of normal saline or after injection of 4 ml of diatrizoate (serum Cr 69.84+/-5.5 micromol l(-1) pre contrast injection and 66.67+/-13.47 micromol l(-1) 24 h post contrast injection, n=5). The increase in serum Cr observed with 6 ml of diatrizoate was significantly higher (p<0.01) than the rise induced by equivolume of the low osmolar non-ionic monomer iopromide (Ultravist, 300 mgI ml(-1)) (serum CR 68.47+/-8.39 micromol l(-1) pre contrast injection and 143.59+/-32.03 micromol l(-1) 24 h post contrast injection, n=5). The calcium channel blocker diltiazem (10 mg kg(-1) injected intraperitoneally 30 min prior to RCM injection) prevented the rise in serum Cr observed with 6 ml of diatrizoate (serum Cr pre contrast injection 70.31+/-7.28 micromol(-1) and 78.21+/-17.81 micromol(-1) 24 h post contrast injection in animals pre-treated with diltiazem, n=5). The protective effect against RCM-induced reduction in renal function was less with lower doses of diltiazem. In conclusion, the animal model used is reliable and reproduced previously established observations in the field of RCMN. The protective effect of a calcium channel blocker at the appropriate dose against RCMN has also been shown. The clinical effectiveness of this class of drugs in preventing RCMN requires further evaluation.

Predicting renal failure after balloon angioplasty in high-risk patients

PURPOSE

To assess the incidence and predictors of acute renal failure after percutaneous transluminal angioplasty (PTA) in a cohort of patients with generalized atherosclerosis.

METHODS

A retrospective review of 213 consecutive patients (127 men; median age 71 years, interquartile range 63-77) undergoing femoropopliteal PTA was undertaken. Renal function was measured by creatinine clearance at baseline and 24 hours after the intervention; acute renal dysfunction was defined as > or = 20% decrease of creatinine clearance. The predictive value of potential risk factors was determined in a multivariate model adjusting for comorbidities, pre-existing renal impairment, and angiographic data.

RESULTS

Overall serum creatinine values and creatinine clearance remained stable within 24 hours after PTA. Acute renal dysfunction occurred in 25 (12%) patients. Two (1%) patients developed oliguria; one required transient hemodialysis and developed persistent renal failure. Pre-existing impaired renal function (OR 12.2, p < 0.0001) and contrast dosage (OR 1.1, p = 0.03) were independent predictors of acute renal failure; hypertension (OR 7.9, p = 0.06) and congestive heart failure (OR 4.5, p = 0.06) were associated factors.

CONCLUSIONS

While transient acute renal dysfunction occurs in approximately 10% of patients with peripheral artery disease within 24 hours after angioplasty, persistent renal failure or end-stage renal disease is rare.

Salvage of immature forearm fistulas for haemodialysis by interventional radiology

BACKGROUND

The goal of this article is to assess the value of endovascular techniques for the salvage of fistulas that fail to mature.

METHODS

Over a 6-year period, 52 dysfunctional and 17 thrombosed immature forearm fistulas (mean age 10 weeks) were treated by interventional radiology. Angiography was performed by puncture of the brachial artery but dilation of underlying stenoses was performed after cannulation of the fistula itself, whenever possible, with a balloon never smaller than 5 mm. Embolization or ligation of any type of vein was never indicated and never performed. For thrombosed fistulas, significant clots were removed by manual catheter-directed aspiration. A covered stent (Passager) was used in cases of dilation-induced rupture not controlled by balloon tamponade.

RESULTS

An underlying stenosis was diagnosed in 100% of cases. Half of them were located in the anastomotic area. The initial success rate of interventional radiology was 97%. Dilation-induced rupture occurred in nine cases (13%) but stents were necessary in only two cases. The rate of significant clinical complications was 2.8% (bacteraemia, pseudoaneurysm). Primary and secondary patency rates at 1 year were 39 and 79%, respectively.

CONCLUSIONS

Delayed maturation of native fistulas should lead systematically to imaging as an underlying stenosis is diagnosed in all cases. Interventional radiology can treat the majority of cases and achieve a 97% success rate but early recurrence of stenoses can occur. Multidisciplinary re-evaluation of the patient must, therefore, be performed after radiological salvage of the fistula.

Coronary artery disease in uremia: Etiology, diagnosis, and therapy

Cardiovascular disease is a major challenge to nephrologists, whether we deal with patients with pre-end-stage renal failure, on dialysis or after successful renal transplantation. It is the most common cause for death in patients with a functional allograft, and prevents many dialysis patients from being engrafted. Coronary artery disease is a diagnostic and therapeutic challenge, as it differs in some respects from that seen in non-uremic cohorts, and lacks much of the evidence-base on which therapeutic intervention rests. This review examines the experimental and clinical literature on cardiovascular disease in uremia, focusing on coronary artery disease. We focus on the incidence, presenting syndromes, screening tools, and interventions in the context of acute and chronic coronary syndromes. Recent evidence comparing coronary angioplasty, coronary artery stenting, and bypass surgery in subjects with renal failure is also reviewed. Coronary artery disease is more prevalent in uremia, more difficult to diagnose and less rewarding to treat compared to non-uremic subjects. Many more randomized trials are needed. In the absence of information from such trials, we advocate aggressive control of conventional and novel cardiovascular risk factors, and early intervention for symptomatic coronary disease.

Techniques for predicting a favourable response to renal angioplasty in patients with renovascular disease

Renovascular disease is present in some 10-40% of patients with end-stage renal disease, and constitutes the fastest-growing group of end-stage renal disease patients. The unselective correction of renal artery stenosis has led to disappointing results. Most studies that compared conservative treatment with angioplasty found only modest or no beneficial effects of angioplasty on renal function and blood pressure. It is therefore mandatory to evaluate the functional significance of a stenosis before intervention. Patients with a high likelihood of a favourable response should be identified. Factors that affect outcome include the severity of renal artery stenosis, the procedure used to treat renal artery stenosis (antihypertensive drugs, angioplasty with or without stenting, or surgery), radiocontrast nephrotoxicity, atheroembolism and, most importantly, underlying renal disease, forestalling a favourable response of renal function or blood pressure even after the successful correction of renal artery stenosis. Evaluation of the renal resistance index using Doppler ultrasound or captopril scintigraphy are the best methods by which to classify patients as responders or non-responders to intervention. Each factor has to be considered before the correction of renal artery stenosis to achieve satisfactory results with regard to an improvement in renal function and blood pressure.

Prediction and prevention of contrast nephropathy

Over the last 10 years, the main advances in RCN have come in our ability to predict outcomes for an individual patient. Treatment trials have been almost all uniformly disappointing. Recent positive trials with acetylcysteine and PGE1 will require confirmation in larger trials that are adequately powered for meaningful end points in the PCI population. In the meantime, adequate prehydration and maintenance of post-PCI urine flow rates of > 150 mL/min remain the most prudent measures. As the population ages, breakthroughs with respect to new contrast agents or effective prevention measures will be needed to offer PCI to the spectrum of patients at risk for renal injury.

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

OBJECTIVE

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

DATA SOURCES

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

STUDY SELECTION

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

DATA SYNTHESIS

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

CONCLUSIONS

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

Using Acetylcysteine to Prevent Radiographic-Contrast-Media-Induced Nephropathy in a Patient with Chronic Renal Failure

Clinical Pearls

Each of these special features conveys an idea, concept, or fact that may be useful in your pharmaceutical practice, but may not be widely known, published, or taught. An 84-year-old male with a history of chronic renal failure secondary to nephrectomy and chronic hypertension was admitted for elective coronary angiography following complaints of midsternal chest pain and an abnormal thallium stress test. The patient was found to have other risk factors for radiographic-contrast-media-induced nephropathy, including hyponatremia and hypoalbuminemia. Mild volume expansion was initiated and acetylcysteine 600 mg was administered orally every 12 hours on the day before the procedure. The patient's baseline serum creatinine was found to be 2 mg/dL. A total of 125 mL of nonionic, low-osmolality contrast media was infused during the procedure. An additional two doses of acetylcysteine 600 mg were administered on the day of the procedure. The patient's recovery was uneventful and he was discharged. The postprocedure serum creatinine was stable at 2 mg/dL 48 hours after the procedure. It appears that orally administered acetylcysteine can prevent radiographic-contrast-media-induced nephropathy.

Complications in endoluminal repair of abdominal aortic aneurysms

In this review the technical and systemic complications occurring during endoluminal repair of abdominal aortic aneurysms are summarized. According to the data in the literature the technical success-rate of the endoluminal procedure should be >90% and the overall complication-rate <10%. It should be differentiated between complications which have an adverse effect on the outcome of the procedure, and technical problems, which complicate the procedure but do not affect the outcome. The majority of the technical problems can be solved endoluminally. The 30-day mortality rate should be in the same range as elective open surgical repair. One major factor influencing the immediate results is the experience of the interventional team.

Use of fenoldopam to prevent radiocontrast nephropathy in high-risk patients

We evaluated the ability of fenoldopam, a newly available renal vasodilator, to prevent radiocontrast nephropathy in high-risk patients undergoing interventional diagnostic and therapeutic angiographic procedures. We reviewed the results from 46 consecutive procedures in patients with serum creatinine > or = 1.5 mg/dL if diabetic and > or = 1.7 mg/dL if nondiabetic. We compared our results to a previously published cohort of similarly at-risk patients. The incidence of radiocontrast nephropathy, defined as an increase in serum creatinine of > or = 25% at 48 hr following the procedure, was 13% in the group treated with fenoldopam, compared to an expected 38%. The percentage change in serum creatinine at 48 hr was +16% vs. +118%, respectively, in the two groups. In this preliminary experience, the use of fenoldopam in high-risk patients appears to minimize the likelihood of radioncontrast nephropathy. Cathet Cardiovasc Intervent 2001;53:341-345.

Malignancy and renal disease

A variety of renal diseases and electrolyte disorders may be associated with various malignancies or with treatment of malignancy with chemotherapeutic drugs or radiation. This article reviews renal disease in cancer patients, which constitutes a major source of morbidity and mortality.

Dialysis-induced oxidative stress: biological aspects, clinical consequences, and therapy

Oxidative stress, which results from a rupture in the natural balance between pro- and antioxidant systems, is considered as a major factor in dialysis-associated morbidity and mortality. Emerging pharmacologic and dialytic antioxidant therapeutic and dialysis strategies should enable us to reduce the harmful consequences of oxidative stress in dialysis patients. Moreover, since there is increasing evidence of oxidative stress long before the initiation of maintenance dialysis, antioxidant therapeutic strategies should probably be developed very early in the course of renal failure.

Prevention of contrast media-induced renal dysfunction with prostaglandin E1: a randomized, double-blind, placebo-controlled study

Preexisting renal impairment is an all-encompassing risk factor for radiocontrast-associated nephrotoxicity. Renal impairment appears to be associated with the inadequate production of renal prostaglandins at the critical time of radiocontrast administration and for a variable time period afterward. We prospectively studied 130 patients with chronic renal insufficiency (serum creatinine > or =1.5 mg/dL) who were undergoing radiocontrast administration. Using a double-blind, randomized, prospective technique, patients were assigned to either placebo or one of three prostaglandin E1 (PGE1) treatment groups (10, 20, or 40 ng/kg/min). Infusion was started 60 +/- 30 minutes before the administration of radiocontrast and was continued for a total of 6 hours. In the placebo group, radiocontrast administration resulted in a mean increase (+/- SD) in serum creatinine of 0.72 +/- 1.15 mg/dL at 48 hours. This increase was less in each of the PGE1 treatment groups after 48 hours, with a significant difference between placebo and the 20 ng/kg/min PGE1 group (P = 0.01). Using baseline adjusted means, analysis of covariance with baseline serum creatinine as the covariable demonstrated significant differences between the placebo and 20 ng/kg/min PGE1 group (P = 0.03) and between the placebo and 10 ng/kg/min PGE1 group P = 0.047). In a subgroup analysis of the diabetic patients, the increase in serum creatinine was less pronounced in the three PGE1 groups versus the placebo group, and the 20 ng/kg/min PGE1 group had the most favorable outcome. The parenteral administration of PGE1 immediately before radiocontrast exposure and continued for a period of 5 to 5.5 hours significantly reduced the elevation of serum creatinine poststudy. The most effective of the three PGE1 dosing regimens was 20 ng/kg/min.

Acute renal failure requiring dialysis after percutaneous coronary interventions

Acute renal failure requiring dialysis is a rare but serious complication after percutaneous coronary interventions (PCI), associated with high in-hospital mortality and poor long-term survival. We have analyzed the incidence, resource utilization, short- and long-term outcomes, and predictors of dialysis after percutaneous coronary interventions. We studied 51 consecutive patients who were not on dialysis on admission and developed acute renal failure that required in-hospital dialysis after PCI in comparison to the 7,690 patients who did not require dialysis after PCI. Patients who required dialysis were older, with a higher incidence of hypertension, diabetes, prior bypass surgery, chronic renal failure, and a significantly lower left ventricular ejection fraction. Despite similar angiographic success, these patients had a higher incidence of in-hospital mortality (27.5% vs. 1.0%, P < 0.0001), non-Q-wave myocardial infarction (45.7% vs. 14.6%, P < 0.0001), vascular and bleeding complications, and longer hospitalization. At 1-year follow-up, mortality (54.5% vs. 6.4%, P < 0.0001), myocardial infarction (4.5% vs. 1.6%, P = 0.006), and event-free survival (38.6% vs. 72.0%, P < 0.0001) were significantly worse in patients who required dialysis compared to patients who did not. Multivariate analysis revealed in-hospital dialysis and an increase in baseline serum creatinine levels as the most important predictors of in-hospital and long-term mortality. Thus, acute renal failure that requires dialysis after percutaneous coronary interventions is associated with very high in-hospital and 1-year mortality rates and a dramatic increase in hospital resource utilization.

Angiographic evaluation and treatment of transplant renal artery stenosis

Transplant renal artery stenosis is an uncommon but important complication of renal transplantation. It is a potentially reversible cause of patient morbidity and allograft dysfunction, which can present both early and late in the post-transplant period. Although transplant renal artery stenosis can be detected using noninvasive imaging, definitive diagnosis and percutaneous treatment typically require the use of invasive angiographic techniques. In experienced hands, these studies can be performed safely, effectively and with a low risk of contrast induced nephrotoxicity when alternative contrast agents are used.

Preventing contrast-induced nephropathy with fenoldopam

Fenoldopam is an interesting orphan drug that is a variant of dopamine. It differs significantly from dopamine in that it is a specific agonist for the type I (DA-1) receptor. The DA-1 receptors are particularly prominent in the renal vasculature, renal tubules, mesenteric vasculature, and peripheral vessels. The DA-1 receptor stimulation vasodilates renal and peripheral vessels, causing a decrease in blood pressure and an increase in renal blood flow (RBF). Stimulation of the DA-1 receptors in the tubules causes an increase in sodium excretion, which gives rise to an increase in urine volume on the basis of a sodium natriuresis. Animal testing with fenoldopam has indicated that it is 6 times more potent than dopamine in its ability to decrease renal vascular resistance and increase RBF; this suggests that it could be a much more selective and potent renal protective agent against any toxin or stimulus that causes renal dysfunction by reducing RBF or increasing renal ischemia. The clinical activity of fenoldopam, which is administered intravenously, begins almost immediately and is clearly noticeable after 5 minutes. The drug has no rebound effect, and its use can be stopped at any time. The protocol for the use of fenoldopam as a renal protective agent (performed at the University of Minnesota) involves starting an intravenous fenoldopam infusion 2 hours before the procedure at a rate of 0.1 microg/kg/min and increasing the dose in increments of 0.1 microg/kg/min every 20 minutes, until a rate of 0.5 microg/kg/min is reached or the systolic blood pressure falls more than 40 mm Hg (or below 110 mm Hg). Any infusion level at or above 0.1 microg/kg/min is considered acceptable because the response in individual patients varies so widely. The fenoldopam infusion is maintained at the maximum rate throughout the procedure and for up to 4 hours after the end of the contrast administration. At the University of Minnesota, we have had anecdotal experience using the drug in 29 patients. The drug was used for patients who were thought to be at the highest risk for contrast-induced nephropathy, ie, patients who have both diabetes and pre-existing renal failure. In this small group of patients in whom hydration and other variables were not controlled, there was a startling lack of contrast-induced creatinine increase at any point during the 24 to 48 hours after the administration of contrast in all but 1 patient. Our experience suggests that fenoldopam may be of distinct benefit to high-risk patients who need intravascular contrast, especially those who may receive a large contrast dose, such as patients undergoing peripheral or coronary angiography and intervention and/or computed tomography. Although it is impossible on the basis of simple anecdotal case reports to determine whether or not the drug was the primary reason that such a marked protective effect was seen, the results are promising enough to indicate that a careful, prospective, randomized trial of fenoldopam versus hydration is warranted.

Ischemic nephropathy

Ischemic nephropathy is a major cause of chronic renal failure in people over 50 years of age. In addition, renal artery stenosis is associated with increased mortality, particularly if renal or cardiac function is compromised. The diagnosis is made both by clinical characteristics and imaging studies. At present, duplex Doppler ultrasound and magnetic resonance angiography appear to be the most promising non-invasive screening tests. Although data from controlled trials are lacking, revascularization is the mainstay of therapy for ischemic nephropathy. Advances in percutaneous interventions now allow revascularization to be offered to many patients, including those who are poor surgical candidates. The role of medical therapies (statins, angiotensin-converting enzyme inhibitors, intensive control of blood pressure) and how to best utilize revascularization (which patients and when) remain to be defined.

The Year in Review: Critical Care Medicine

Background: There have been significant recent advances in the pharmacotherapeutic management of critically ill patients. The purpose of this article is to review and discuss the most pertinent published literature in the areas of neurology, cardiovascular diseases, infectious diseases, nephrology, hematology, and gastroenterology as it pertains to critical care in order to provide an update for the critical care practitioner.

Methods: We performed a Medline search from July 1999 to December 2000 utilizing terms relating to the pharmacotherapy of the specific aforementioned topics in critical care medicine. We focused on English-language clinical studies performed in adult intensive care unit (ICU) patients. From these articles we selected those that would have a practical impact on drug therapy in the ICU or the development of drug usage guidelines for critically ill patients. Review articles were generally not included.

Results: The following topics were found to be either new developments or of potentially significant impact in the management of adult critically ill patients. In the area of neurology, advances were found with respect to optimization of regimens for sedative and neuromuscular blocking agents, validation of sedation scales and tools, and in the treatment of head injury patients. In the cardiovascular diseases, most studies related to the hemodynamic support of septic shock. We focus on developments in fluid resuscitation, optimization of global and regional oxygen transport variables, the repositioning of vasopressor agents, and a return to the use of steroids. Given the high mortality rate associated with the development of acute renal failure in the ICU, there has been a consistent attempt to develop preventative and treatment strategies for these patients, including optimization of antimicrobial dosing methods. Several epidemiological and longitudinal studies document changes in multi-drug antimicrobial resistance patterns. The use of treatment guidelines for antimicrobials in the critically ill improves outcomes in most patients. Significant attention has focused on the characterization of anemia in the ICU and the development of alternative pharmacological strategies in its treatment. Finally, in gastroenterology, the main focus has been the investigation of methods to optimize the delivery of enteral nutrition given its proven benefits in critically ill patients.

Conclusions: Significant advances in the areas of neurological, cardiovascular, infectious diseases, renal, hematological, and gastrointestinal issues in the pharmacotherapy of critically ill patients have been published over the course of the past year. Many of these studies have yielded data that may be incorporated into the pharmacotherapeutic management of ICU patients, hence maximizing outcomes.

Review of studies establishing the aging male spontaneously hypertensive rat as a detector and quantifier of the kidney toxicity of radiocontrast media and other chemicals

RATIONALE AND OBJECTIVES

There is a need for practical and sensitive preclinical tests for detecting the kidney toxicity of chemicals. The spontaneously hypertensive rat (SHR), as it ages, develops renal and cardiovascular changes similar to those considered as human risk factors for radiocontrast-induced renal damage. Age, male gender, and uncontrolled hypertension make these animals susceptible to the volume and osmolality of the administered contrast agent and the effect of repeated contrast administration after a brief interval. This article reviews studies in which the role of these and other factors were evaluated to validate the male SHR as a small animal model for renal damage induced by contrast and other agents.

METHODS

Systolic blood pressure was measured with a tail cuff before and after the administration of the experimental substances, and the left kidney and heart were studied histologically to determine the influence of age, dose of contrast repeated at a short interval, gender and strain, the role of the sympathetic adrenergic nervous system, osmolality, and apoptosis.

RESULTS

As the animals aged and the systolic blood pressure remained elevated, the animals developed progressive renal lesions that worsened after the administration of contrast. The most advanced renal lesions occurred in adult male SHRs that received two doses of contrast 6 hours apart. Female SHR rats and male Wistar Kyoto rats showed no effect or only minimal changes in heart and kidneys after the administration of contrast compared with age-matched male SHRs. Adrenergic blockade allowed only a small elevation in systolic blood pressure after contrast administration but did not protect the kidneys against renal damage by contrast. Hypaque, Omnipaque, and mannitol caused renal damage in proportion to their osmolality. Apoptosis with Hypaque, Omnipaque, and mannitol was observed in the kidney and heart.

CONCLUSION

The results indicate that the aging male SHR develops spontaneous renal lesions that progress with age, increasing the susceptibility to the renal-damaging effects of contrast. Thus, the aging male SHR provides a laboratory tool for detecting the risk of renal damage of new contrast media as well as other pharmaceuticals and assessing methods to protect the kidneys and possible mechanisms of renal damage.

Acute renal failure: a practical update

Acute renal failure (ARF) affects almost all medical specialties. Its occurrence seems to be increasing in hospitalized patients. A structured approach to the evaluation and management of ARF would facilitate rapid diagnosis and treatment in most patients. Appreciation for the multiple drugs that affect renal function is especially important. Exclusion of urinary outflow obstruction and administration of therapies that improve renal perfusion should be given top priority with respect to managing ARF. Dialytic intervention for ARF is required when otherwise irreversible pathophysiologic derangements of electrolyte homeostasis, fluid balance, and uremic solute control are imminent. This article provides a brief review and update on the clinical evaluation and management of ARF.

Role of adenosine in contrast media-induced acute renal failure in diabetes mellitus

Increased release of renal adenosine and stimulation of renal adenosine receptors have been proposed to be major mechanisms in the development of contrast media-induced acute renal failure (CM-ARF). Patients with diabetes mellitus or preexisting renal disease who have reduced renal function have a markedly increased risk to develop CM-ARF. This increased risk to develop CM-ARF in patients with diabetes mellitus is linked to a higher sensitivity of the renal vasculature to adenosine, since experimental studies have shown increased adenosine-induced vasoconstriction in the kidneys of diabetic animals. Furthermore, recent evidence suggests that administration of adenosine receptor antagonists reduces the risk of development of CM-ARF in both diabetic and nondiabetic patients. The purpose of this review is to discuss the role of adenosine in the development of CM-ARF, particularly in the kidneys of diabetic patients, and to evaluate the therapeutic potential of adenosine receptor antagonists in the prevention of CM-ARF. Selective adenosine A1 receptor antagonists may provide a therapeutic tool to prevent CM-ARF in patients with diabetes mellitus and reduced renal function.

Reactive oxygen species and acute renal failure

Acute renal failure is commonly due to acute tubular necrosis (ATN), the latter representing an acute, usually reversible loss of renal function incurred from ischemic or nephrotoxic insults occurring singly or in combination. Such insults instigate a number of processes-hemodynamic alterations, aberrant vascular responses, sublethal and lethal cell damage, inflammatory responses, and nephron obstruction-that initiate and maintain ATN. Eventually, reparative and regenerative processes facilitate the resolution of renal injury and the recovery of renal function. Focusing mainly on ischemic ATN, this article reviews evidence indicating that the inordinate or aberrant generation of reactive oxygen species (ROS) may contribute to the initiation and maintenance of ATN. This review also discusses the possibility that ROS may instigate adaptive as well as maladaptive responses in the kidney with ATN, and raises the possibility that ROS may participate in the recovery phase of ATN.

Novel approaches to the treatment of acute renal failure

Acute renal failure (ARF) occurs frequently in hospitalised patients and is associated with significant morbidity and mortality. Many therapeutic strategies have been undertaken both to prevent acute renal injury and, once ARF occurs, to improve renal function and reduce mortality. Among the available pharmacological options, no specific therapy has been shown to alter the course of ARF. This article reviews the efficacy of several strategies in experimental renal disease and raises the possibility that similar interventions might be available to the clinician in the near future for the prevention and management of ARF. The prospect of these novel strategies together with the ever-increasing understanding of the complex pathophysiology of ARF, offers the promise of effective and more physiological therapeutic interventions in this new millennium.