Strategies to reduce the risk of contrast-induced nephropathy

In view of the clinical importance of contrast-induced nephropathy (CIN), numerous potential risk-reduction strategies have been evaluated. Adequate intravenous volume expansion with isotonic crystalloid (1.0-1.5 mL/kg per hr) for 3-12 hours before the procedure and continued for 6-24 hours afterward can lessen the probability of CIN in patients at risk. There are insufficient data on oral fluids (as opposed to intravenous volume expansion) as a CIN-prevention strategy. No adjunctive medical or mechanical treatment has been proved to be efficacious in reducing risk for CIN. Prophylactic hemodialysis and hemofiltration have not been validated as effective strategies. The CIN Consensus Working Panel considered that, of the pharmacologic agents that have been evaluated, theophylline, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), ascorbic acid, and prostaglandin E(1) deserve further evaluation. N-acetylcysteine is not consistently effective in reducing the risk for CIN. Fenoldopam, dopamine, calcium channel blockers, atrial natriuretic peptide, and l-arginine have not been shown to be effective. Use of furosemide, mannitol, or an endothelin receptor antagonist is potentially detrimental. Nephrotoxic drugs should be withdrawn before contrast administration in patients at risk for CIN.

Baseline renal function screening

Renal impairment at baseline (estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m(2)) is the most important risk marker to predict the risk of contrast-induced nephropathy (CIN) in patients receiving iodinated contrast media. Hence, it is important to assess renal function before administration of contrast medium to ensure that appropriate steps are taken to reduce the risk. Serum creatinine alone does not provide a reliable measure of renal function, hence the National Kidney Foundation Kidney Disease Outcome Quality Initiative (K/DOQI) recommends that clinicians should use an eGFR calculated from the serum creatinine as an index of renal function. The CIN Consensus Working Panel agreed that eGFR should be determined before contrast administration, using the abbreviated Modification of Diet in Renal Disease (MDRD) formula, recommended by K/DOQI as the preferred equation for the calculation of eGFR in adults. Where a serum creatinine measurement or eGFR is not available, a simple survey or questionnaire can be used before contrast agent administration to identify patients at higher risk for CIN compared with the general population. In emergency situations, where the benefit of very early imaging outweighs the risk of waiting, the CIN Consensus Working Panel agreed that the procedure can be performed without assessment of renal function.

Risk prediction of contrast-induced nephropathy

In order to make appropriate decisions about clinical management, it is important for physicians to be able to stratify patients according to their risk for contrast-induced nephropathy (CIN). The most important risk marker for nephropathy after exposure to iodinated contrast media is preexisting renal impairment. The risk of CIN is elevated and becomes clinically important in patients with chronic kidney disease characterized by an estimated glomerular filtration rate <60 mL/min per 1.73 m(2). In patients with renal impairment, diabetes mellitus amplifies the risk of CIN and complicates postprocedure management. Other markers associated with an increased risk of CIN include cardiovascular disease, periprocedural hemodynamic instability, use of nephrotoxic drugs, and anemia. The effect of risk factors is additive, and the presence of multiple risk factors in the same patient can create a very high risk for CIN and acute renal failure requiring dialysis. Risk models incorporating baseline and periprocedural characteristics have been developed using data from large databases of percutaneous coronary intervention patients. These schemes are potentially valuable, but at present the most practical approach to risk prediction is based on a simple model incorporating renal function and diabetes mellitus.

Contrast medium use

Various properties of iodinated contrast media (osmolality, ionic versus nonionic, and viscosity) may contribute to contrast-induced nephropathy (CIN). Therefore, the choice of contrast medium affects the risk for CIN. There is good evidence that low-osmolar contrast media are less nephrotoxic than high-osmolar contrast media in patients at increased risk for CIN who receive intra-arterial iodinated contrast. Current evidence suggests that nonionic isosmolar contrast presents the lowest risk for CIN in patients with chronic kidney disease (CKD), particularly in those patients with diabetes mellitus. Intra-arterial administration of contrast media may be associated with a greater risk for CIN above that observed with intravenous administration. The use of gadolinium or CO(2) as alternative contrast media to avoid the risk of nephrotoxicity cannot be substantiated by clinical trials and therefore cannot be recommended. Most studies show that, within a class, higher volumes (>100 mL) of iodinated contrast medium are associated with a higher risk for CIN. However, in patients at high risk, such as those with CKD and diabetes, even small volumes of contrast medium can have adverse effects on renal function.

Epidemiology and prognostic implications of contrast-induced nephropathy

Contrast-induced nephropathy (CIN), usually defined as an increase in serum creatinine of 0.5 mg/dL (44.2 mumol/L), or a 25% increase from the baseline value 48 hours after the procedure, is a common and potentially serious complication of the use of iodinated contrast media in patients at risk of acute renal injury. It is an important cause of hospital-acquired renal failure, responsible for approximately 11% of cases. CIN may be difficult to distinguish from cholesterol embolization, another cause of postprocedure renal impairment. The reported incidence of CIN varies depending on the patient population studied. The impact of postprocedural renal impairment on clinical outcomes has been evaluated most extensively in patients undergoing percutaneous coronary intervention. CIN is associated with increased mortality both in hospital and at 1 year. A higher incidence of in-hospital and late cardiovascular events, as well as longer hospital stays, has been reported in patients developing CIN. In a small proportion of patients, CIN is severe enough to require dialysis, and these patients have a particularly poor prognosis. Many of the risk markers for CIN are also predictive of a worse prognosis.

Pathophysiology of contrast-induced nephropathy

Contrast-induced nephropathy (CIN) is the third leading cause of acute kidney injury in hospitalized patients and is associated with significant patient morbidity. The pathogenesis of CIN is complex and not fully understood, but iodinated contrast agents induce intense and prolonged vasoconstriction at the corticomedullary junction of the kidney. Moreover, high-osmolar dyes directly impair the autoregulatory capacity of the kidney through a loss of nitric oxide production. These effects, coupled with direct tubular toxicity of contrast media, lead to overt acute tubular necrosis and the syndrome of CIN.

Endovascular repair of a recurrent aortocaval fistula and anastamotic false aneurysm

Aortocaval fistula (ACF) and false aneurysm are a recognized complication of open abdominal aortic aneurysm (AAA) repair. Untreated they are often fatal. However, open surgical repair of this complication is associated with a high operative mortality and a significant complication rate. Endovascular management using a stent-graft to exclude the false aneurysm and fistula is a technically feasible alternative and confers many advantages over open repair by virtue of its minimally invasive nature. We report the endovascular management of this rare but serious complication of open AAA repair.

Prevalence of methadone injection in three Swiss cities

OBJECTIVE

Intravenous methadone is associated with increased risk of morbidity and mortality. A previous report from a methadone center in Fribourg, Switzerland, found a high prevalence (43%) of patients who injected oral methadone. We therefore wished to assess the prevalence of methadone injection among patients in oral methadone programs in 3 other Swiss cities--Lausanne, Geneva, and La Chaux-de-Fonds.

METHOD

Subjects were randomly selected and interviewed by assistant psychologists who were not on the staff of the study centers. Participation was voluntary and anonymous.

RESULTS

164 patients participated in the study (n = 58 in Lausanne, 52 in Geneva, and 54 in La Chaux-de-Fonds). The prevalence of methadone injection was low (5%) and did not differ significantly between the cities.

DISCUSSION

Less liberal policies cannot explain the lower prevalence of methadone injection in these three centers than in Fribourg. The high prevalence of methadone injection there is probably related to its separate methadone injection program: patients in oral methadone programs may be more likely to injection methadone when other patients authorized to do so.

IN CONCLUSION

Although the 5% prevalence of methadone injection found in the 3 cities surveyed is low, it is not negligible. These results suggest that information on the risks associated with injection of methadone syrup should be provided to all methadone maintenance. This information is especially necessary when maintenance therapy is provided in the same center, or city as injectable methadone maintenance.

Arrhythmias in an athlete: the effect of de-training

A 53 year old athlete with a history of severe palpitations and lightheadedness presented for a second opinion. He was found to exhibit very frequent atrial ectopy, frequent runs of symptomatic atrial tachyarrhythmia, and sinus bradycardia at rest. During exercise testing, his tachyarrhythmias increased in relation to the duration and intensity of exercise. A therapeutic trial of de-training was suggested. As a result, his symptoms completely resolved with a marked reduction in the frequency of atrial arrhythmia. Repeat exercise testing revealed an excellent exercise tolerance with no atrial ectopy. De-training should be considered when athletes present with arrhythmias.

Isolation of peptides of the brevinin-1 family with potent candidacidal activity from the skin secretions of the frog Rana boylii

The emergence of strains of the human pathogen Candida albicans with resistance to commonly used antibiotics has necessitated a search for new types of antifungal agents. Six peptides with antimicrobial activity were isolated from norepinephrine-stimulated skin secretions from the foothill yellow-legged frog Rana boylii. Brevinin-1BYa (FLPILASLAA10KFGPKLF CLV20TKKC) was particularly potent against C. albicans [minimal inhibitory concentration (MIC) = 3 microm] and also active against Escherichia coli (MIC = 17 microm) and Staphylococcus aureus (MIC = 2 microm), but its therapeutic potential for systemic use is limited by its strong hemolytic activity (HC50 = 4 microm). The single amino acid substitution (Phe12 --> Leu) in brevinin-1BYb resulted in a fourfold lower potency against C. albicans and the additional amino acid substitutions (Lys11 --> Thr, Phe17 --> Leu and Val20 --> Ile) in brevinin-1BYc resulted in a ninefold decrease in activity. Two members of the ranatuerin-2 family and one member of the temporin family were also isolated from the secretions but showed relatively low potency against the three microorganisms tested.

Early detection of malignant process in benign lesions of breast tumor by measurements of changes in structuredness of cytoplasmic matrix in circulating lymphocytes (SCM test) reinduced in vitro by specific tumor antigen

Early detection is crucial for successful treatment of all types of cancer. The specificity and sensitivity of the current methods vary from 50% to 80%. The use of specific tumor antigens and cytometric technology has resulted in the development of a new procedure for the early detection of breast tumors. This new method is reported. The test utilizes static cytometry, which records polarization and intensity changes in fluorescent light emitted from each individual lymphocyte obtained from tumor-bearing patients stimulated by the relevant specific tumor antigen. Using MUC-1/SEC as the specific antigen, we detected breast tumors with 85% specificity and 81% sensitivity in 137 breast tumor-bearing women. A significant linear correlation was found between the SCM test and the conventional classification of relative risk for breast cancer in benign lesions, suggesting that this is a precise method that could be used in mass screening for early detection of breast cancer.

Hematopoietic stem cell transplantation for cardiac and peripheral vascular disease

Recent studies have suggested that marrow and blood hematopoietic stem cells may contribute to nonhematopoietic tissue repair in multiple organ systems. In animal models and more recently in limited human trials, unpurified marrow mononuclear cells and/or subsets of adult hematopoietic stem cells have been reported to contribute to neoangiogenesis. Since the subset of hematopoietic stem cells (HSCs) that are both CD34+ and AC133+ are endothelial cell precursors, clinical trials using autologous AC133+ HSCs isolated with the Miltenyi CLIMACS cell separator and transplanted into patients with ischemic and refractory peripheral vascular or coronary artery disease are being implemented at Northwestern University.

Direct, real-time assessment of dopamine release autoinhibition in the rat caudate-putamen

Inhibition of endogenous dopamine release by photo-released dopamine (i.e., autoinhibition) was characterized in the rat caudate-putamen using combined caged-dopamine photolysis and fast-scan cyclic voltammetry. Coronal brain slices (400 microm thick) were perfused with caged-dopamine (150-200 microM in artificial cerebrospinal fluid). Ultraviolet illumination of increasing duration (25-250 ms, approximately 100 microm beam diameter) was focused at the tip of the recording electrode to uncage increasing amounts of exogenous dopamine at the recording sites (0.5-5 microM); a single biphasic electrical stimulus was delivered 0.1-10 s later to induce endogenous dopamine release. The concentrations of both endogenous and exogenous dopamine were determined using voltammetry, thus enabling determination of concentration-dependent inhibition of the endogenous release by the latter. While unaffected by control ultraviolet illumination, endogenous dopamine release was rapidly inhibited by photo-released dopamine in a concentration-dependent manner. Photo-application of 3-5 microM exogenous dopamine inhibited the endogenous release by 90-100% (electrical stimulus applied 1 s after photolysis initiation), an effect prevented by 2 microM sulpiride. The autoinhibition was dependent on the time between photolysis onset and electrical stimulation. Terminal dopamine autoreceptor stimulation led to robust inhibition of endogenous dopamine release with a latency of approximately 200 ms and effective duration of less than 5 s. The percent autoinhibition was a skewed, U-shaped function of photolysis/electrical stimulation intervals with the peak inhibition at 1 s. This study directly demonstrates that autoreceptor-mediated inhibition of terminal dopamine release in caudate-putamen is designed to provide a rapid, robust, yet short-lasting modulation of terminal dopamine release.

Marginal and internal adaptation of stratified compomer-composite Class II restorations

Different approaches have been proposed to improve the adaptation of Class II restorations, including applying low-elasticity modulus base liners. This in vitro fatigue test (or study) evaluated the influence of the compomer base-lining configuration on restoration adaptation. Direct Class II MOD box-shaped composite restorations with or without base and lining (n=3x8) were placed on intact human third molars with proximal margins 1 mm above or under the CEJ. The compomer (Dyract) was applied as a 1 mm-thick lining or as a base, closing proximo-gingival margins. Marginal adaptation was assessed before and after each phase of mechanical loading (250,000 cycles at 50N, 250,000 cycles at 75N and 500,000 cycles at 100N); internal adaptation was evaluated after test completion. Gold-sputtered resin replicas were observed in the SEM and restoration quality evaluated in percentages of continuity (C) at the margins and within the internal interface after sample section. Mechanical loading did not influence adaptation to enamel, while it adversely affected restoration adaptation to dentin for the full composite and compomer-base restorations (C varied, respectively, from 95.2 to 75.3% and from 98.0 to 10.6%). The internal adaptation quality showed the same general trend, however, with reduced scores of continuity. In this experimental condition, application of a low elasticity modulus layer under the restorative material proved advantageous but the compomer should not contact the gingival margins.

Heart failure in patients admitted to hospital: mortality is still high

BACKGROUND: Two separate cohorts of consecutive patients admitted to hospital with a primary diagnosis of heart failure were studied, the first in 1986 in Rochdale, and the second in 1995 in Brighton. METHODS: We observed the clinical profile, treatment and mortality during hospital admission and reviewed their status at 6 months. There were 132 patients in the Rochdale cohort and 223 in the Brighton cohort. RESULTS: The Rochdale cohort was characterised by a lower mean age and longer hospital stay. Significant differences were also observed in co-morbidity and the use of ACE inhibitors, but hospital mortality was almost identical (25% in Rochdale and 24% in Brighton). A low systolic blood pressure, hyponatraemia, hyperkalaemia and a raised blood urea at presentation were independent adverse prognostic factors. In contrast, prior treatment with ACE inhibitors in patients with congestive cardiac failure led to a more favourable hospital outcome. Age, gender and co-morbidity did not affect mortality apart from patients with acute myocardial infarction. Follow-up of these cohorts showed that mortality of the two groups remained high at 180 days after admission (40% in Rochdale and 39% in Brighton). There were marked differences in the use of ACE inhibitors in survivors, but target doses of ACE inhibitors (enalapril 20 mg/day or equivalent) were only achieved in 31%, despite direct communication between the hospital and primary care physicians. CONCLUSIONS: Although clinical and treatment profiles differed between the two periods studied, the hospital and 6-month mortality of patients with heart failure remained high. More emphasis needs to be given to optimising ACE inhibitor use in primary care.

An approach for high sensitivity detection of breast cancer by analysis of changes in structure of the cytoplasmic matrix of lymphocytes specifically induced by a specific breast tumour antigen (MUC-l/SEC)

An alternative procedure for detection breast cancer was examined based on the observation that lymphocytes re-exposed in vitro to antigenic stimulation will change their intracellular structuredness as measured by polarization of fluorescent light emitted by fluorescein labeled cells (SCM test). The specific antigen MUC-l/SEC was used to elicit such response in lymphocytes of patients with and without breast cancer. Eighty-five samples with breast cancer were tested, of which 72 were correctly diagnosed. Of the 41 controls, 35 were correctly identified as healthy subjects. The sensitivity of the test was 85% and the specificity was 81%. These results suggest a possible valuable method for screening and early detection of breast cancer. The clinical importance of this procedure lies in the ability to screen high-risk populations with higher specificity and sensitivity than any combinations of currently available procedures for breast cancer detection.