Faruk Tokmak

High-dose cholecalciferol to correct vitamin D deficiency in haemodialysis patients

BACKGROUND Vitamin D has emerged as an important survival factor in patients with chronic kidney disease. Non-activated vitamin D may also have beneficial effects on bone, cardiovascular and immune functions. Cholecalciferol is the prevalent non-activated vitamin D in Europe, but there is no valid prospective data available about its use in haemodialysis patients. Thus, we initiated a prospective study to evaluate dosing, safety and tolerability of cholecalciferol supplementation in haemodialysis patients. METHODS The prospective study included 64 haemodialysis patients. During replenishment phase patients received 20 000 IU cholecalciferol/week for 9 months. In the open maintenance phase (15 months), patients were randomized to a treated group (20 000 IU cholecalciferol/month) and an untreated group, which did not receive cholecalciferol. RESULTS Calcidiol [25(OH)D] deficiency (<37.5 nmol/l; <15 microg/l) was detected in 61/64 patients (95%). During the replenishment phase, calcidiol increased significantly from 16.65 +/- 9.6 to 79.48 +/- 27.15 nmol/l (6.66 +/- 3.84 microug/l to 31.79 +/- 10.86 microg/l) (P < 0.001). Recommended levels (>75 nmol/l; >30 microg/l; K/DOQI) were achieved in 57% of patients. Calcium increased from 2.28 +/- 0.17 to 2.37 +/- 0.19 mmol/l (9.1 +/- 0.69 mg/dl to 9.49 +/- 0.75 mg/dl) (P<0.01). Phosphorus, calcium-phosphorus product and parathyroid hormone showed no significant changes. Fifty-nine patients progressed to the maintenance phase. Analysis per protocol showed a significant drop of calcidiol in the treated [83.98 +/- 31.73 versus 78.5 +/- 38.75 nmol/l (33.59 +/- 12.69 versus 31.4 +/- 15.5 microg/l) (P < 0.001)] and untreated groups [86.35 +/- 40.75 versus 53.4 +/- 26.2 nmol/l (34.54 +/- 16.3 versus 21.36 +/- 10.48 microg/l) (P < 0.001)]. The comparison of the treated and the untreated groups showed no significant differences at the beginning of the maintenance phase: 83.98 +/- 31.73 versus 86.35 +/- 40.75 nmol/l (33.59 +/- 12.69 versus 34.54 +/- 16.3 microg/l). At the end they differed significantly: 78.5 +/- 38.75 versus 53.4 +/- 26.2 nmol/l (31.4 +/- 15.5 versus 21.36 +/- 10.48 microg/l) (P < 0.001). CONCLUSION Vitamin D deficiency is present in a majority of haemodialysis patients. Supplementation with cholecalciferol is safe, well tolerated and reasonable to replenish vitamin D stores in haemodialysis patients. However, only 57% of patients achieved recommended calcidiol levels, thus favouring additional dose-finding studies.

Speciation Analysis of Gadolinium-Based MRI Contrast Agents in Blood Plasma by Hydrophilic Interaction Chromatography/Electrospray Mass Spectrometry

The first analytical method for simultaneous speciation analysis of five of the most important gadolinium-based magnetic resonance imaging (MRI) contrast agents in blood plasma samples was developed. Gd-DTPA (Magnevist), Gd-BT-DO3A (Gadovist), Gd-DOTA (Dotarem), Gd-DTPA-BMA (Omniscan), and Gd-BOPTA (Multihance) were separated by hydrophilic interaction liquid chromatography (HILIC) and detected with electrospray mass spectrometry (ESI-MS). Spiking experiments of blank plasma with Magnevist and Gadovist were performed to determine the analytical figures of merit and the recovery rates. The limits of detection ranged from 1 x 10 (-7) to 1 x 10 (-6) mol/L depending on the ionization properties of the individual compounds, and limits of quantification ranged from 5 x 10 (-7) to 5 x 10 (-6) mol/L. The linear concentration range comprised 2 orders of magnitude. With application of this method, blood plasma samples of 10 healthy volunteers, with Magnevist or Gadovist medication, were analyzed for Gd-DTPA and Gd-BT-DO3A, respectively. The obtained results were successfully validated with inductively coupled plasma-optical emission spectroscopy (ICP-OES).

Analysis of the contrast agent Magnevist and its transmetalation products in blood plasma by capillary electrophoresis/electrospray ionization time-of-flight mass spectrometry.

To study transmetalation effects of the gadolinium-based contrast agent Magnevist (Gd-DTPA), the first analytical method for the simultaneous determination of Gd-DTPA and its transmetalation products in complex clinical samples was developed. The high separation efficiency of capillary electrophoresis (CE) was employed to separate Gd-DTPA, Fe-DTPA, Cu-DTPA, Zn-DTPA, and the free DTPA (diethylenetriaminepentaacetic acid) ligand. The coupling of CE with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) provided the required sensitivity and excellent selectivity for the analysis of complex samples, such as blood plasma and whole blood. Separation and detection parameters were optimized, and crucial steps for CE/MS method development are pointed out. Limit of detection (LOD) is 5 x 10(-7) mol/L, limit of quantification (LOQ) is 1.7 x 10(-6) mol/L, and the linear range comprises 2 decades, starting at the limit of quantification. To determine recovery rates, precision, and accuracy of the method, blank plasma samples were spiked with Gd-DTPA in three different concentrations. Blood plasma samples from 10 patients with normal renal function, having received Magnevist, were analyzed for Gd-DTPA and possible transmetalation products by CE/ESI-TOF-MS. The method was validated by determination of the total Gd concentration using inductively coupled plasma optical emission spectroscopy (ICP-OES). Transmetalation assays of Magnevist with and without supplementary iron were carried out in incubated whole blood samples.

Effects of moxonidine on sympathetic nerve activity in patients with end-stage renal disease

Objective End-stage renal disease (ESRD) is characterized by markedly increased sympathetic outflow that contributes to increased cardiovascular mortality in these patients. The central sympatholytic drug moxonidine (MOX) has been shown to reduce muscle sympathetic nerve activity (MSNA) in initial stages of chronic kidney disease; however, the effects in ESRD are not known. The aim of this study was to test the hypothesis that low-dose MOX causes sustained decreases in sympathetic outflow in ESRD patients. Design and methods Twenty-three ESRD patients (mean age 46.4 ± 16 years, 14 men, seven women, no diabetic patients) were randomized to a daily treatment of 0.3 mg MOX or placebo (PLA) in addition to pre-existing antihypertensive therapy. At baseline and after 1 and 6 months of treatment, heart rate (HR, ECG), blood pressure (mean arterial pressure, automatic sphygmanometer), calf blood flow (CBF, venous occlusion plethysmography), muscle sympathetic nerve activity (MSNA) (microneurography at the peroneal nerve) were measured. Data are mean ± SEM. Results MOX acutely decreased MSNA within 2 h after oral intake (from 45 ± 3.7 to 35 ± 3.9 bursts/min, P < 0.05). This decrease was sustained over 6 months (MSNA 45 ± 3.7, 35 ± 4.6, 33 ± 4.5 bursts/min at 0, 1 and 6 months, P < 0.05). PLA had no effect. Neither MOX nor PLA resulted in any significant acute or long-term changes in HR, MAP or CBF. Conclusions In ESRD patients, low-dose MOX produced sustained and substantial reductions in sympathetic outflow without hemodynamically compromising them. We suggest that the inhibition of central sympathetic outflow may improve cardiovascular prognosis in ESRD.

Sympathetic nerve activity in renal transplant patients before and after withdrawal of cyclosporine.

Background It has been suggested that the increase in blood pressure observed in transplant patients treated with cyclosporine is mediated by cyclosporine-induced sympathoexcitation. However, the chronic effects of cyclosporine on sympathetic outflow in renal transplant patients have not been investigated. Therefore we studied sympathetic nerve activity and blood pressure before and 6 months after the withdrawal of cyclosporine in renal transplant patients. Methods Twenty-four renal transplant patients with histologically confirmed chronic allograft nephropathy (age 48 ± 3 years, 60 ± 10 months after transplantation) were included in the prospective study and randomly assigned to either withdrawal (n = 12) or continuation (n = 12) of cyclosporine. Both groups received mycophenolate mofetil and prednisolone as additional immunosuppressants. At entry and 6 months later blood pressure, muscle sympathetic nerve activity (MSNA), and plasma norepinephrine were measured. To assess the potential influence of the diseased native kidneys, three renal transplant patients who had their native kidneys removed were studied before and after cyclosporine withdrawal. Results Mean arterial pressure decreased significantly in the cyclosporine-withdrawal group (95 ± 4 versus 105 ± 4 mmHg 6 versus 0 months, P < 0.05) but not in the cyclosporine-continuation group (103 ± 3 versus 105 ± 4 mmHg, NS). However, plasma norepinephrine and MSNA did not change significantly in either group (MSNA 43 ± 4 versus 44 ± 3 and 38 ± 5 versus 39 ± 4 bursts/min in the cyclosporine-withdrawal and cyclosporine-continuation groups, NS). Graft function remained stable in both groups and in transplant patients who had their native kidneys removed MSNA did not decrease after cyclosporine withdrawal. Conclusion The withdrawal of cyclosporine in renal transplant patients, receiving relatively low doses of cyclosporine, resulted in a substantial decrease in blood pressure. However, MSNA and norepinephrine did not change. This suggests that cyclosporine treatment does not cause chronic sympathetic activation that could explain the cyclosporine-induced blood pressure elevation in renal transplant patients.

Quantification and excretion kinetics of a magnetic resonance imaging contrast agent by capillary electrophoresis-mass spectrometry.

A novel method for the analysis of Gadolinium‐based contrast agents in complex clinical matrices is presented. Three commonly applied ionic contrast agents for magnetic resonance imaging were separated by CE and detected by ESI‐MS. Blank urine samples were spiked with Dotarem® (Gd‐DOTA, Gadolinium‐1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid), Magnevist® (Gd‐DTPA, Gadolinium‐diethylenetriaminepentaacetic acid) and Multihance® (Gd‐BOPTA, Gadolinium‐benzyloxymethyl‐diethylenetriaminepentaacetic acid) to determine the recovery rates. The figures of merit were determined with LODs as low as 2.0×10−7 mol/L for Gd‐DOTA, 5.0×10−7 mol/L for Gd‐DTPA and 1.0×10−6 mol/L for Gd‐BOPTA. The respective LOQs were 6.6×10−7 mol/L for Gd‐DOTA, 1.5×10−6 mol/L for Gd‐DTPA and 3.3×10−6 mol/L for Gd‐BOPTA. The linear working range comprised two orders of magnitude starting at the LOQ, with regression coefficients of R≥0.999 for all investigated analytes. Using this CE‐MS method, Gd‐DOTA was quantified in seven urine samples obtained at different times after delivery from a volunteer magnetic resonance imaging patient who was treated with Dotarem®. Additionally, total Gd concentrations were determined by means of ICP‐optical emission spectroscopy to validate the CE‐MS data. To compensate for dietary dilution effects of the urine samples, creatinine was determined by HPLC with UV/Vis absorption detection. Gd‐DOTA concentrations were normalized to urinary creatinine, illustrating the fast excretion kinetics of Gd‐DOTA.

C-Reactive Protein Levels and Clinical Symptoms Following Gadolinium Administration in Hemodialysis Patients

BACKGROUND Until recently, gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) has increasingly replaced iodinated contrast agent examinations in dialysis patients, although only limited data existed about the clinical safety of Gd contrast agents in these patients. Specific clinical adverse events (AEs), including nephrogenic systemic fibrosis, were linked to Gd exposure in dialysis patients. An inflammatory reaction or transmetallation may be involved. STUDY DESIGN Secondary analysis of a 5-day observational study in a parent cardiovascular study with repetitive cardiac MRI (32 patients) and patients undergoing Gd-enhanced MRI for clinical indications (6 patients). Clinical information and samples were obtained according to parent protocol. SETTING & PARTICIPANTS Dialysis patients at a university-based dialysis unit. PREDICTOR Gd-chelate complex. 37 of 38 patients underwent 64 MRI studies with Gd-diethylenetriamine penta-acetic acid (Gd-DTPA). 25 of these patients underwent additional MRI studies with gadobutrol (n = 10), 0.9% saline (n = 7), or both (n = 8), and 1 patient received gadobutrol only. OUTCOMES Clinical adverse events; C-reactive protein (CRP) levels on days 1, 3, and 5 after MRI; Gd levels in blood and urine after MRI. RESULTS CRP levels increased 10-fold on day 3 after MRI in 87% of MRI studies with Gd-DTPA (+59.3 +/- 57.9 mg/L [P < 0.001] versus -0.9 +/- 3.7 mg/L with gadobutrol versus -0.9 +/- 8.5 mg/L with 0.9% saline). 77 mild to moderate and 3 serious AEs were observed in 24 patients. CRP levels and adverse events did not correlate with Gd blood concentrations. CRP level increase or AEs were not observed after MRI with gadobutrol or 0.9% saline. LIMITATIONS Observational study without randomization, risk of bias because of multiple MRI studies in a limited patient cohort. CONCLUSION Gd-DTPA, but not gadobutrol, induces an acute-phase reaction and clinical AEs in dialysis patients. Additional investigations have to analyze the underlying pathomechanism.

Hypercalcemia after transplant nephrectomy in a hemodialysis patient: a case report

IntroductionHypercalcemia is a complication often seen in chronic hemodialysis patients. A rare cause of this condition is sarcoidosis. Its highly variable clinical presentation is challenging. Especially in patients suffering chronic kidney graft failure the nonspecific constitutional symptoms of sarcoidosis like fever, weight loss, arthralgia and fatigue may be easily misleading.Case presentationA 51 year old male developed hypercalcemia, arthralgia and B-symptoms after explantation of his kidney graft because of suspected acute rejection. The removed kidney showed vasculopathy and tubulointerstitial nephritis, which had not been overt in the biopsy taken half a year earlier. Despite explantation and withdrawal of the immunosuppression the patients general condition deteriorated progressively. A rapid rise in serum calcium finally provoked us to check for sarcoidosis. CT scans of the lungs, broncho-alveolar-lavage and further lab tests confirmed the diagnosis.ConclusionThis case demonstrates that withdrawal of immunosuppressive drugs sometimes unmasks sarcoidosis. It should be considered as differential diagnosis even in hemodialysis patients, in whom other reasons for hypercalcemia are much more common.

Autotransplantation for the treatment of severe renal artery stenosis in a solitary kidney after repeated percutaneous transluminal angioplasty: a case report.

A 66-year-old female suffering from massive atherosclerosis with a long history of renal artery stenosis in the left solitary kidney was admitted to reevaluate an in-stent restenosis. Advanced peripheral arterial disease had formerly been treated by aortobifemoral bypass surgery and a highly eccentric infrarenal abdominal aortic stenosis of 70 - 80% had been treated by patch angioplasty. In this patient several percutaneous transluminal renal angioplasties after a former stent deployment had resulted in recurrent in-stent restenoses. The renal artery stenosis was reevaluated and a re-angioplasty attempt was unsuccessful due to technical failure. Blood pressure remained difficult to manage. Renal function decreased as a result of presumed acute renal failure. A further progression of the renal artery stenosis was found. Autotransplantation to the left iliac fossa was done, because aortorenal bypass was considered impossible. Renal function normalized and follow-up Doppler ultrasonography examinations revealed a newly developed ostial anastomotic stenosis of 60 - 70%. While medical therapy and percutaneous transluminal angioplasty with stent deployment are common treatment options, surgical interventions are reserved for cases of complex stenoses. Autotransplantation as a complex option in the treatment of renal artery stenosis seems to be an adequate alternative in patients with severe, generalized atherosclerosis after failure of interventional procedures and the impossibility of standard surgical techniques.

Skeletal status after kidney transplantation by quantitative ultrasound: a 2-year follow-up study

Quantitative ultrasound (QUS) is a new and non-invasive method to assess skeletal status after kidney transplantation. We evaluated the potential use of this novel method in renal allograft recipients and studied the accuracy compared to normal controls. Thirty patients (NTP, age 47.5 ± 13.0 years) were studied 4.8 ± 3.2 years after kidney transplantation. Twenty-five healthy control persons (CON) were matched for age and sex. The left and right os calcis were studied by QUS, and speed of sound (SOS) and broadband ultrasound attenuation (BUA) were measured. Bone stiffness (BS) was calculated from these parameter and corrected for age (CBS). Differences between right and left os calcis were compared to CON to assess the side variability (mean ± SD); BS was 75 ± 25% compared to young adults, age-corrected CBS was decreased in NTP with 86 ± 25% of normal, indicating a 2-fold increased risk of fracture. SOS was 1,525 ± 47.7 m/s, BUA was 105 ± 22 dB/MHz. Mean difference between right and left os calcis was significantly higher in NTP than in CON (7.2 ± 7.1% vs. 2.1 ± 2.1%, p < 0.01). Limits of agreement of the measurements (MW of differences ± 2 SD) according to a Bland-Altmann type statistic were 16.9% and 20.7%. There was no correlation between CBS and age, cumulative steroid dose, parathyroid hormone concentrations or time after transplantation. In addition, 19 patients (49 ± 3 years, graft function: 1.8 ± 0.2 and 2.0 ± 0.2 mg%) were investigated in a 2-year follow-up study. The measures of bone stiffness at months 0 and 24 were well correlated (r < 0.9, p < 0.001), however, bone stiffness did not change significantly with time. There was a significant correlation between bone stiffness and serum calcium values (0.49, p < 0.015). Our data show altered bone structure expressed by low bone stiffness values measured by quantitative ultrasound in kidney transplant patients. However, because of relatively high interfeet variance of QUS, we suggest measurement of both os calcis to minimize measurement error after transplantation. In addition, we conclude from the data of this follow-up study that despite continued low-dose steroid treatment (< 10 mg prednisolone/day), renal transplant recipients are not subject to accelerated osteoporosis. Bone stiffness did not significantly decrease over 2 years in the present study. However, bone stiffness baseline and 2 years later were found to be decreased compared to healthy controls, a finding that is in accordance with previous data demonstrating an increased fracture rate in allograft recipients.