Vassilis Vargemezis

Development of an easily applicable risk score model for contrast-induced nephropathy prediction after percutaneous coronary intervention: A novel approach tailored to current practice

BACKGROUND Several risk factors for contrast-induced nephropathy (CIN) after percutaneous coronary intervention (PCI) have been identified. The cumulative effect of these risk factors on renal function has been assessed with the development of risk score models in a number of studies. However, concerns were raised that estimates of the risk attributable to individual factors may be unreliable. We sought to develop a simple risk score for developing CIN after PCI irrespective of use of prophylactic measures and also capturing the effect of pre-intervention medication and presence of various co-morbidities. METHODS Consecutive patients treated with elective or urgent PCI at our cardiac catheterization laboratory were enrolled (derivation cohort n = 488, validation cohort n = 200). CIN was defined as increase ≥ 25% and/or ≥ 0.5 mg/dl in serum creatinine at 48 h after PCI vs baseline. Multivariable logistic regression analysis was then performed to identify independent predictors of CIN (pre-existing renal disease, metformin use, history of previous PCI, peripheral arterial disease and ≥ 300 ml of contrast volume). RESULTS The incidence of CIN in the development cohort was 10.2% with a significant trend across increasing score values (p < 0.001). The model demonstrated good discriminating power (c-statistic 0.759) and excellent calibration (calibration slope 0.91). The model was validated internally by bootstrapping in 1000 samples (c-statistic 0.753) and in a cohort of 200 patients (c-statistic 0.864) demonstrating stable performance. CONCLUSIONS The proposed risk score is easily applicable and allows for practically simple risk assessment compared to other published scores while at the same time overcomes drawbacks of previous model designs.

Problem-Based Learning via Web 2.0 Technologies

During the last few decades, medical education is shifting is increasingly embracing active learning approaches. This shift from teaching to learning is also strongly related to an involvement of information and communication technology, and especially the Internet and the Web. The emergence of Internet 2.0 is indeed being stressed as a promising tool for advanced support of medicine and medical education. Although Web 2.0 emphasizes on participation, in its early days is still used in the majority of cases to hold and provide content (albeit created dynamically and via peer participation and collaboration) and then systematically deliver it to students. In this paper, we propose the use of wikis and blogs not just for creation and promotion of information, but as active tools to support problem based learning in medicine. In this approach, students and instructors use the Web as a virtual place to collaborate and create new knowledge and new educational experiences.

Peritoneal Catheters and Related Infections

Catheter related infectious complications (exit-site infections, tunnel infections, and peritonitis) remain the major reasons for technique failure during the three decades since, continuous ambulatory peritoneal dialysis (CAPD) treatment has been first established. Despite improvements in catheter’s survival rates, catheter related complications result in an increase in the cumulative patients’ morbidity and often leading to the catheter removal. The ideal catheter provides reliable and rapid dialysate flow rates without leaks or infections. Among several types, the double-cuff straight Tenckhoff catheter, developed in 1968, is still the most widely used, although its use is decreasing in favour of swanneck catheters. Although there are onlu few well-designed trials comparing catheters and catheters related infectious complications, controlling for all other important variables, no difference in these complications among the main types of catheters was seen. The single cuff catheters have been associated with a shorter survival rate and time to the first peritonitis episode than the double-cuff catheters. Also exit-site infections were found to be more frequent and significantly more resistant to treatment with single-cuff compared to double-cuff ones. Finally, better results have been reported with the latest developed presternal peritoneal dialysis catheter both regarding survival rates and exit-site infection and peritonitis rates. Recently a renewed interest in continuous flow peritoneal dialysis stimulated inventions of imaginative, double-lumen catheters since a suitable peritoneal access is a sine qua non condition for the development of this new technique of peritoneal dialysis.

Effect of One-year Oral α-Tocopherol Administration on the Antioxidant Defense System in Hemodialysis Patients

Abstract:  Oxidative stress is increased in hemodialysis (HD) patients and contributes to the increased morbidity and mortality in this population. Vitamin E is an antioxidant agent. In the present study the effect of prolonged oral α‐tocopherol administration on the antioxidant defense system was evaluated. The antioxidant factors plasma total antioxidant status (TAS), red blood cell superoxide dismutase (SOD) activity and glutathione peroxidase (GPX) activity were evaluated with spectrometry in 27 HD patients. Measurements were performed before and after oral administration of α‐tocopherol at a dose of 500 mg/d for a one‐year period. Twenty HD patients received a placebo and 22 healthy volunteers served as controls. TAS was increased in HD patients. No difference was detected in SOD and GPX activity between HD patients and healthy volunteers. Tocopherol administration induced a significant decrease in TAS and SOD activity. Levels of GPX activity remained unaffected. All the evaluated factors remained stable in the HD patients receiving a placebo. Prolonged oral α‐tocopherol administration in HD patients induces a decrease in some components of the antioxidant defense system, raising the possibility for a pro‐oxidative role of vitamin E. Vitamin E is an antioxidant agent, but it is also known to have pro‐oxidant action under special conditions that can be encountered in HD patients.

Home dialysis as a first option: a new paradigm

Traditionally, the initial choice of dialysis for patients with end stage renal disease (ESRD) has been in-center hemodialysis (HD) or peritoneal dialysis (PD). Usually, the choice between these (PD vs. HD) has been based on the characteristics of the dialysis techniques. Obviously the choice of peritoneal dialysis implied dialysis at home, but its geographic location has been only a secondary consideration. Peritoneal dialysis has evolved as a dependable mode that gives good outcomes. This method has become more attractive with the option of overnight cyclers and the recent use of home helpers in some jurisdictions. At the same time the interest in home hemodialysis was rekindled by reports of good outcomes with short daily or nocturnal hemodialysis. Home dialysis (PD or HD) offers high quality of treatment, a high degree of patient independence, and is financially attractive. Therefore, we propose a change in our approach to the choice of the initial form of dialysis for patients with ESRD. Instead of choosing between HD and PD we should present the new patients the advantage of dialysis at home and instead of asking them to choose between peritoneal dialysis or hemodialysis, they should be offered the option to choose between dialysis at home (PD or HD) or in-hospital. This paper will review the advantages of the home-based dialysis methods and the arguments for this simple but vital change in the process of choosing the method of dialysis.

Timely transfer of peritoneal dialysis patients to hemodialysis improves survival rates.

AIMS The two main renal replacement therapies (RRT)--hemodialysis (HD) and peritoneal dialysis (PD)--have been considered to be antagonistic in most published studies on the clinical outcomes of dialysis patients. Recently, it has been suggested that the complementary use of both modalities as an integrated care (IC) strategy might improve the survival rate of end-stage renal disease patients. The aim of this study was to estimate the final clinical outcome of PD patients when they transfer to HD because of complications related to PD. MATERIALS AND METHODS We retrospectively analyzed data from the following patients that started RRT during the last 10 years: 33 PD patients (IC group; age 55 +/- 15 years, mean +/- SD) who transferred to HD, 134 PD patients (PD group, age 64 +/- 11 years) who remained in PD, and 132 HD patients (HD group, age 48 +/- 16 years) who started and continued in HD. The main reasons for the transfer to HD were relapsed peritonitis and loss of ultrafiltration, while various comorbid risk factors were adjusted by Cox hazards regression model (age, presence of diabetes or/and cardiovascular disease, serum hemoglobin and albumin levels, as well as the modality per se). RESULTS 3- and 5-year survival rates for the IC, PD and HD groups were 97% and 81%, 54% and 28%, and 92% and 83%, respectively. The 5-year survival rate was significantly higher in IC patients than in PD patients (p < 0.00001) but, was not different from that in HD patients. CONCLUSIONS Our results show that the IC of dialysis patients undergoing RRT improves the survival of patients on PD if they are transferred to HD upon the appearance of PD related complications.

Impact of Long-Term Cinacalcet, Ibandronate or Teriparatide Therapy on Bone Mineral Density of Hemodialysis Patients: A Pilot Study

Background: Insufficient evidenced-based information is available for the treatment of osteoporosis in hemodialysis (HD) patients. Methods: In 102 HD patients, bone mineral density (BMD) was measured twice 16 ± 3 months apart. In the second BMD measurement 66 of them had a femoral neck (FN) T-score <–2.5. Of these 66 patients, 38 consented to a bone biopsy. Depending on both the bone biopsy findings and parathyroid hormone levels, patients were assigned to treatment groups. Eleven patients with osteitis fibrosa and iPTH >300 pg/ml received cinacalcet, 11 with osteitis fibrosa and iPTH <300 pg/ml received ibandronate, 9 with adynamic bone disease received teriparatide, and 7 with mild abnormalities received no treatment. A third BMD measurement was done after an average treatment period of 13–16 months. We compared the annual percent change of FN and lumbar spine (LS) BMD before and during treatment. Results: FN and LS BMD decreased significantly in the cinacalcet group, with an annual change of 3.6 and 3.4% before treatment to –4.2% (p = 0.04) and –7.7% (p = 0.02) during treatment, respectively. In the teriparatide group, FN and LS BMD increased, although not significantly, with an annual change of –5.4 and –2.6% before treatment to 2.7 and 4.9% during treatment, respectively. In both the ibandronate and the no treatment groups, BMD change rate remained negative during the whole study. Conclusions: Teriparatide administration improved BMD in HD patients with adynamic bone disease, although these results did not reach statistical significance. In HD patients with osteitis fibrosa, ibandronate did not improve BMD while cinacalcet reduced BMD.

Differential Effect of Baseline Adiponectin on All-Cause Mortality in Hemodialysis Patients Depending on Initial Body Mass Index. Long-Term Follow-Up Data of 4.5 Years

OBJECTIVES We sought to investigate the interaction of adiponectin levels and body mass index (BMI) for predicting all-cause mortality in a cohort of hemodialysis (HD) patients. DESIGN Longitudinal, observational cohort study. SETTING HD unit. SUBJECTS Sixty patients (mean age: 64 ± 13 years, 39 men) with end-stage renal disease on maintenance HD followed up for 4.5 years represented the prospective study cohort. INTERVENTION Associations between baseline plasma adiponectin levels and initial BMI with all-cause mortality were assessed taking into account the assumption of nonlinear correlations. The association between adiponectin, BMI, and serum levels of interleukin-10 (IL-10) and interleukin-6 (IL-6) with survival was determined cross-sectionally. MAIN OUTCOME MEASURE All-cause mortality. RESULTS Nonlinear survival modeling showed that there was a U-shaped association of BMI with all-cause mortality, whereas there was an inverse U-shaped association for plasma adiponectin levels. Using a BMI of 24 kg/m(2) as a cutoff, an interaction effect of BMI on the association between adiponectin and mortality was observed (P = .045). In participants with BMI ≥ 24 kg/m(2), each 15 μg/mL increase in plasma adiponectin levels was associated with a decreased hazard of death (hazard ratio: 0.57, 95% CI: 0.32 to 0.99) in unadjusted analysis. In HD patients with BMI < 24 kg/m(2), no significant association was observed between adiponectin and mortality (P = .989). Cross-sectional analysis showed that in the subgroup of patients in whom the protective effect of adiponectin was observed (BMI ≥ 24 kg/m(2)), a positive linear association existed between adiponectin and IL-10 levels (r = 0.345, P = .027) as well as a negative association with IL-6 levels (r = -0.322, P = .040). No association was observed in patients with BMI < 24 kg/m(2), neither with IL-10 nor with IL-6. CONCLUSIONS Obesity possibly modifies the effect of adiponectin on all-cause mortality in HD patients, thus explaining the published conflicting results in recent literature regarding the association of plasma adiponectin levels and mortality in chronic kidney disease patients.

Vascular access for hemodialysis: postoperative evaluation and function monitoring

SummaryVascular access (VA) survival is a crucial issue associated with morbidity and mortality of patients undergoing maintenance hemodialysis. The development of stenosis is the major factor that leads to VA failure. Strategies for early detection of lesions within a VA system before serious complications arise are therefore crucial. The implementation of a VA surveillance program could lead to timely detection of VA dysfunction and referral for correction, reduction in central venous catheter use and decrease in hospitalization and VA-related cost. Suggested methods for arteriovenous fistulae and grafts surveillance include blood flow measurement, static pressure evaluation and duplex ultrasonography. Physical examination is an accepted method in contrast to nonstandardized dynamic pressure measurement for grafts. Access recirculation (not urea based) and dynamic pressure measurements are accepted methods for fistulae. Decreasing URR or Kt/V (otherwise unexplained) and increased (negative) arterial pressure in the dialysis machine are methods of limited sensitivity and specificity for both fistulae and grafts. Measurement of access blood flow has been proposed as the gold standard for the screening of all types of VA. Access flow can be measured by various techniques which are direct or indirect. Several studies about VA surveillance programs have demonstrated conflicting results. Larger, randomized controlled trials need to be carried out in order to clarify whether surveillance programs are necessary and which is the best surveillance strategy for each type of VA.

The Value of Computed Tomography-Derived Coronary Artery Calcification Score in Coronary Artery Disease Detection in Asymptomatic Hemodialysis Patients

Background. We evaluated the value of coronary artery calcification (CAC) score in coronary artery disease (CAD) detection in asymptomatic hemodialysis (HD) patients by evaluating the association among CAC score, exercise electrocardiography (EECG), and Thallium-201 dipyridamole scintigraphy. Correlation between aortic pulse wave velocity (PWV) and CAC score was also evaluated. Methods. CAC score was assessed with conventional computed tomography in 40 patients. Thirty patients completed EECG and 25; those with a positive CAC score and/or a positive EECG performed Thallium dipyridamole scintigraphy. Carotid-femoral PWV was assessed in all patients. Results. There was no association among CAC score and EECG or Thallium dipyridamole scintigraphy. In contrast, CAC score was correlated with aortic PWV. Conclusion. The previous results question the role of CAC score in the detection of CAD in asymptomatic HD patients. The correlation between CAC score and aortic PWV raises the possibility that CAC score represents more an indicator of coronary artery medial wall calcification than a marker of CAD.