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Proximal Veins (proximal + vein)
Selected AbstractsExperimental Study of a New Method for Early Detection of Vascular Access Stenoses: Pulse Pressure Analysis at Hemodialysis NeedleARTIFICIAL ORGANS, Issue 2 2010Koen Van Canneyt Abstract Hemodialysis vascular access (VA) stenosis remains a frequent complication. However, early detection is challenging and costly. The aim of this in vitro study was to assess a new detection method based on pulse pressure analysis at the hemodialysis needle. A silicon model of a radiocephalic arteriovenous fistula was built in a mock loop. Pressure profiles were measured at the arterial hemodialysis needle and in the proximal feeding artery. Stenoses (50 and 25% diameter reduction) were created proximal to the anastomosis (proximal artery) and distal to the arterial needle (distal vein and proximal vein). The pulse pressure (PP) at the needle was divided by the PP at the feeding artery to obtain a dimensionless ratio, %PP. Experiments were conducted at different blood flow (500,1200 mL/min) and heart rates (60,90 beats/min) to test this new index over a wide range of hemodynamic conditions. In the control model (no stenosis), %PP was 20.26 ± 4.55. A proximal artery 50% stenosis significantly decreased %PP to 7.69 ± 2.08 (P < 0.0001), while the presence of 50% stenosis in the distal (36.20 ± 2.12) and proximal (32.38 ± 2.17) vein led to significantly higher values of %PP (P < 0.0001). For stenosis of 25% diameter reduction in the proximal artery, the %PP decreased to 15.45 ± 2.13 (P = 0.0022) and the %PP increased with a 25% stenosis in the distal vein to 26.71 ± 3.01 (P = 0.0003) and in the proximal vein to 26.53 ± 2.67 (P = 0.0004). This in vitro study shows that the analysis of the PP at the dialysis needle is useful for early detection and localization of hemodialysis VA stenosis, independent of heart rate and flow level. [source] Asymptomatic deep vein thrombosis in advanced cancer patients: The value of venous sonographyJOURNAL OF CLINICAL ULTRASOUND, Issue 5 2010Nira Beck-Razi MD Abstract Purpose. Although guidelines for venous thromboembolism prevention are available, the implementation of anticoagulant prophylaxis in patients with advanced cancer has yet to be more clearly defined. We aim to determine the incidence of lower extremity deep vein thrombosis (DVT) diagnosed by Doppler sonography (USD) in asymptomatic nonambulatory patients with advanced cancer. Method. In a prospective study, 44 nonambulatory cancer patients with grade 3,4 World Health Organization performance status, asymptomatic for lower extremity DVT, underwent bilateral venous USD studies of the lower extremities. Different risk factors and laboratory data were registered and correlated with the incidence of DVT. Result. Asymptomatic DVT was detected in 15 of 44 patients (34%, 95% CI, 0.21,0.49). Twenty-three percent of all patients had isolated deep calf vein thrombi and 11% of all patients had thrombi in the proximal veins. The only significant risk factor was the number of metastatic sites. DVT was found in 4 of 23 (17.4%) patients with one metastatic site as opposed to 11 of 21 (52.3%) with two or more sites (p < 0.01). Conclusion. USD of the lower extremities detected asymptomatic DVT in 34% of advanced nonambulatory cancer patients and may serve as an additional decision-making tool in the consideration of anticoagulant therapy for this specific population. © 2010 Wiley Periodicals, Inc. J Clin Ultrasound, 2010 [source] Is it worth diagnosing and treating distal deep vein thrombosis?JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2007Summary., The standard diagnostic approach to suspected deep vein thrombosis (DVT) is serial lower limb compression ultrasound (CUS) of proximal veins. Although it only assesses the proximal veins, withholding anticoagulant treatment in patients with a negative CUS on day 1 and after 1 week has been proved safe. In particular, studies evaluating CUS limited to the proximal veins showed a good safety profile with a pooled estimate of the 3-month thromboembolic rate of 0.6% (95% CI, 0.4,0.9%) in non-anticoagulated patients. However, performing two lower limbs CUS is cumbersome and expensive. Recently, studies using a unique complete (proximal and distal) CUS showed a similar pooled estimate of the 3-month thromboembolic rate (0.3%; 95% CI, 0.1,0.6%) but distal DVTs accounted for as many as 50% of all diagnosed DVTs in those series. Comparing these studies may suggest that systematically searching for calf DVTs potentially doubles the number of patients given anticoagulant therapy and entails a risk of over-treatment. Admittedly, performing calf CUS is highly useful in diagnosing other conditions such as popliteal cyst, hematoma or muscle rupture. Performing a CUS limited to the popliteal site in the presence of calf pain may be not well accepted by the patient. However, the advantage of calf CUS in diagnosing venous thromboembolism appears to be at the least debatable. Data suggesting that anticoagulation is indicated for distal DVT are limited, and realizing systematic distal CUS entails a risk of over-treatment. There is an urgent need for randomized trials assessing the usefulness of anticoagulant treatment in distal DVT. [source] The utility of quantitative calf muscle near-infrared spectroscopy in the follow-up of acute deep vein thrombosisJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 4 2006T. YAMAKI Summary.,Background:,To investigate patterns of venous insufficiency and changes in calf muscle deoxygenated hemoglobin (HHb) levels after an acute deep vein thrombosis (DVT). Methods:,A total of 78 limbs with an acute DVT involving 156 anatomic segments were evaluated with duplex scanning and near-infrared spectroscopy (NIRS) at 1, 3, 6 and 12 months. Venous segments were examined whether they were occluded, partially recanalized, and totally recanalized, and the development of venous reflux was noted. The NIRS was used to measure calf muscle HHb levels. Calf venous blood filling index (HHbFI) was calculated on standing, then the calf venous ejection index (HHbEI), and the venous retention index (HHbRI) were obtained after exercise. Results:,The segments investigated were the common femoral vein (CFV; 38 segments), femoral vein (FV; 37), popliteal vein (POPV; 44), and calf veins (CV; 37). At 1 year, thrombi had fully resolved in 67% of the segments, 27% remained partially recanalized, 6% were occluded. The venous occlusion was predominant in the FV (24%) at 1 year. On the contrary, rapid recanalization was obtained in CV than proximal veins at each examination (P < 0.01). Venous reflux was predominant in POPV (55%), followed by FV (19%), and no reflux was found in CV. At 1 year, the HHbFI in POPV reflux patients was significantly higher than those with resolution (0.19 ± 0.14, 0.11 ± 0.05 ,m s, P = 0.009, respectively). Similarly, there was a significant difference in the HHbRI between the two groups (3.08 ± 1.91, 1.42 ± 1.56, P = 0.002, respectively). In patients with FV occlusion, the value of HHbRI was significantly higher than those with complete resolution (2.59 ± 1.50, 1.42 ± 1.56, P = 0.011, respectively). Conclusions:,The lower extremity venous segments show different proportions of occlusion, partial recanalization, and total recanalization. The CV shows more rapid recanalization than proximal veins. The NIRS-derived HHbFI and HHbRI could be promising parameters as the overall venous function in the follow-up of acute DVT. These findings might be very helpful for physician in detecting patients who require much longer follow-up studies. [source] | ||||||||||