Characterization of the cephalic arch and location of stenosis.

PURPOSE: The purpose of this study is to accurately characterize the cephalic arch segments into four domains and to enable more specific evaluation of cephalic arch stenosis (CAS) and determine the frequency of stenosis in each domain. METHODS: After Institutional Review Board (IRB) approval, a retrospective chart review was done to define a population of patients receiving hemodialysis who developed CAS as apparent on clinically indicated radiologic imaging. A standardized approach was devised to categorize four domains of the cephalic arch. Domain I was defined as the peripheral portion of the arch and Domain IV was the distal portion of the cephalic vein near termination with the axillary vein. The magnitude of stenosis as measured by percentage was determined and compared in the four domains. RESULTS: The most frequent location for stenosis was found in domain IV when compared with domains II or I (p<0.01). The magnitude of stenosis differed across all domains (p<0.001) with the least common place for CAS in domain I. Treatment of CAS included angioplasty in all, thrombectomy in eight, and stent placement in five. CONCLUSIONS: CAS occurs most commonly in the terminal portion of the arch. Four standardized domains have been defined; future work will validate these findings and determine the best intervention for each domain.

Asymmetric dimethylarginine and whole blood viscosity in renal failure.

BACKGROUND: Renal failure is a disease with accelerated atherosclerosis beginning with endothelial cell dysfunction. Factors affecting endothelial cell dysfunction include whole blood viscosity (WBV) and asymmetric dimethylarginine (ADMA). The relationship in controls and renal failure was determined. METHODS: 51 subjects, 20 controls, 11 renal transplant recipients, 10 chronic kidney disease and 10 end-stage renal disease patients had blood samples drawn for WBV, Hematocrit, and ADMA. WBV was measured at various shear rates from 10 s(-1) to 780 s(-1) at 37 °C. Hematocrit using CritSpin, and ADMA was assayed using an ELISA method. The significance between groups was compared by boxplots and analysis of variance. Linear relationships were shown by regression lines and correlation coefficients. RESULTS: ADMA was elevated in all groups with renal failure when compared to controls (p < 0.05). Control subjects showed a positive correlation between ADMA and WBV, while those who received a renal transplant had a negative correlation (p < 0.05). The difference in ADMA comparing pre-dialysis to post-dialysis conditions was positive (p < 0.05). CONCLUSIONS: The positive relationship between WBV and ADMA in controls is a novel finding and allows for comparison with other groups. This relationship is dramatically altered in renal failure.

Characteristic differences in cephalic arch geometry for diabetic and non-diabetic ESRD patients.

BACKGROUND: Fistula access in chronic haemodialysis patients is recommended. The first and second choice for location of fistula placement is radial-cephalic followed by the brachiocephalic fistula. Fistula access using the cephalic vein often results in cephalic arch stenosis that is less common in diabetics for unclear reasons. The objective of the current study is to determine if geometry of the cephalic arch differs between diabetics and non-diabetics. METHODS: In a retrospective design, 57 patients with brachiocephalic fistula access had radiology films of the cephalic arch reviewed for geometric analysis. Twelve patients were excluded from final analysis because of stent placement in the cephalic arch. Measurements made included diameter of the cephalic vein, minimum radius of curvature and angle of the arch. Demographics were statistically analysed to determine the association with the geometric measurements. RESULTS: Global and local measurements showed evidence of two arch types. Wider arch angles and larger R/d were associated with diabetes by univariate (P < 0.05) and multivariate analyses (P < 0.05). A wider arch angle was also associated with a history of right permcath access by multivariable analysis (P = 0.042). CONCLUSIONS: Based on this study, it was found that there are two distinct types of cephalic arch geometries. Patients having diabetes mellitus show a significant probability of having a larger R/d ratio and wider arch angle. This study has given insight into structural alterations in geometry of the cephalic arch of diabetics with brachiocephalic fistula access.

A prospective comparison of three argatroban treatment regimens during hemodialysis in end-stage renal disease.

BACKGROUND: We prospectively evaluated 3 treatment regimens of argatroban, a direct thrombin inhibitor, for providing adequate, safe anticoagulation in patients with end-stage renal disease (ESRD) during hemodialysis. METHODS: In this randomized, 3-way crossover study, ESRD patients underwent hemodialysis sessions of 3- or 4-hour duration using high-flux membranes and each of 3 argatroban treatment regimens (A: 250-microg/kg bolus, with an additional 250-microg/kg bolus allowed; B: 250-microg/kg bolus followed by 2-microg/kg/min infusion; C: steady-state, 2-microg/kg/min infusion initiated 4 hours before dialysis). Pharmacodynamic effects including activated clotting times (ACTs); hemodialysis efficacy including single-pool Kt/V, urea reduction ratio (URR), and circuit flow; and safety through a 3-day follow-up were monitored. Argatroban pharmacokinetic parameters including dialytic clearance were evaluated during regimen C. RESULTS: Thirteen patients completed 38 hemodialysis sessions (1 patient withdrew consent after 2 sessions). Mean +/- SD ACTs increased from 131 +/- 14 seconds at baseline to 153 +/- 24, 200 +/- 30, and 197 +/- 33 seconds, respectively, after 60 minutes of hemodialysis using regimens A, B, and C. Across regimens, mean Kt/Vs (1.5-1.6) and URRs (70%-73%) were comparable. No dialyzer was changed; 1 session was shortened 15 minutes because of circuit clot formation. Systemic argatroban clearance increased approximately 20% during hemodialysis, without clinically significantly affecting ACTs. Upon argatroban discontinuation, ACTs and plasma argatroban decreased concurrently (elimination half-life, 35 +/- 6 min). No thrombosis, bleeding, serious adverse events, or clinically significant changes in vital signs or routine laboratory measures occurred. CONCLUSION: Argatroban, administered by each treatment regimen, provides safe, adequate anticoagulation to enable successful hemodialysis in ESRD patients. Argatroban dialytic clearance by high-flux membranes is clinically insignificant.

Medical complications in hemodialysis patients requiring vascular access radiology procedures.

Vascular access maintenance is crucial to providing adequate hemodialysis (HD) and hence preventing signs and symptoms of uremia. The best vascular assess is a permanent arteriovenous fistula (AVF) because it has the longest survival with the least number of complications. However, because of problems with AVF maturation, the majority of HD in the United States is provided via an arteriovenous graft (AVG) or tunneled cuffed central venous catheter. The most common access complications include infection and thrombosis. For these reasons, a patient is often referred to interventional radiology for a procedure such as a catheter placement, change, or a thrombectomy with angioplasty and/or stent placement. Commonly, a HD patient will present after missing a dialysis session. This might predispose the patient to further complications. This review is intended to provide insight into some of the common medical problems (infectious, hematologic, and cardiac) facing a HD patient as a consequence of uremia. Increased awareness to these medical issues provides guidance to prevent unnecessary complications in this difficult patient population.

Hyperphosphatemia in dialysis patients: is there a role for focused counseling?

BACKGROUND: Elevated serum phosphorus (P) and calcium-P product (CaXP) are associated with cardiac mortality in dialysis patients. A CaXP <55 is considered acceptable by most authorities. Because nutrition practices can modulate CaXP, we designed a survey to study the impact of the patients' levels of education and disease awareness on their CaXP. METHODS: A survey questionnaire with 5 didactic questions pertaining to hyperphosphatemia and P-binders and 5 questions related to patient attitudes and beliefs was administered to all patients in a hemodialysis unit. The association of CaXP >55 with the patients' level of education, their score on the survey (didactic part, score 0 to 5), parathyroid hormone (PTH) levels, hyperkalemia, hypertension, and vascular disease were studied. RESULTS: Of the 117 patients (61 men, age 56.5 +/- 18 years) who participated in the survey, 49 (42%) had CaXP >55 and 100 (85%) were on P binders. Thirty-seven (31.6%) had at least some college education. Eighty-seven patients (74%) failed to identify foods rich in P; 61% were unaware of complications related to high CaXP. Patients with CaXP >55 were less likely to have college education (20% versus 39%, P =.04), and had lower survey scores (2.4 +/- 1.3 versus 2.6 +/- 1.4, P = NS). Patients with college education scored higher (2.9 +/- 1.1 versus 2.3 +/- 1.4, P =.014). Furthermore, CaXP >55 was significantly associated with hyperkalemia (P =.02), high PTH levels (P <.001), and hypertension (P =.02), but not with >Kt/V, URR, type of hemodialysis access, or vascular diseases. CONCLUSION: The majority of patients in the survey were ignorant of basic facts pertaining to high P and CaXP. The association of CaXP >55 with hyperkalemia, and not with Kt/V, suggests dietary noncompliance rather than inadequate dialysis. Patients with less education were more likely to have CaXP >55. Because this related mostly to misperception of simple facts that affect dietary habits, there is need for focused counseling of these patients at a level appropriate for their literacy skills.