Distensibility of forearm veins in haemodialysis patients on duplex ultrasound testing using three provocation methods.

OBJECTIVE: It is well-known that vasodilatator function is affected in patients with renal failure. We hypothesized impaired venous forearm distensibility in haemodialysis patients. The purpose of this study was to investigate which provocation method generated 'maximal' venous distensibility in the forearm of haemodialysis patients compared to healthy volunteers by using duplex ultrasound. DESIGN: The study group consisted of haemodialysis patients (n=30) and healthy volunteers (n=30). In each participant ultrasound measurements of the venous diameter were performed by using 3 different provocation methods. METHODS: The applied provocation methods were: 1) hydrostatic pressure, 2) venous congestion and 3) hydrostatic pressure and warmth. Significance of differences in mean diameter changes within the groups was assessed with the paired t-test. Significance of differences in mean diameter changes between the groups was compared by using multivariate regression analysis. RESULTS: In haemodialysis patients, the increase in mean diameter after the different methods was: 29% after methods 2 versus 1, 23% after methods 3 versus 2 and 59% after methods 3 versus 1. In healthy volunteers, the mean diameter increase was: 27% after methods 2 versus 1, 29% after methods 3 versus 2 and 64% after methods 3 versus 1. The greatest increase in the mean internal venous diameter among the haemodialysis patients and the healthy volunteers was after the provocation method which combined hydrostatic pressure with warmth (mean difference: 1mm, 95% CI: .57, 1.36; P<.001 and mean difference: 1.4mm, 95% CI: .88, 1.78; P<.001, respectively). After adjustment for the baseline variables, both groups demonstrated a non-significant mean diameter difference for each of the provocation methods. CONCLUSION: Hydrostatic pressure combined with warmth generates the greatest venous distensibility in the lower arm in haemodialysis patients in a sitting position and is not significantly different compared to healthy volunteers. Without the superior provocation method, venous diameters of haemodialysis patients can be assessed as false-negatives yielding that a primary radio cephalic arteriovenous fistula (RCAVF) at wrist level (the first choice) in these patients will be withheld.

Dialysis fistulae patency and preoperative diameter ultrasound measurements.

BACKGROUND: This study was designed to investigate the possibility of defining a vascular diameter with a practical cut-off point, which predicts a successful patency for radiocephalic arteriovenous fistulae in dialysis patients. METHODS: This is a retrospective analysis of prospectively gathered data. Consecutive patients (n=148) with chronic renal failure, needing vascular access for haemodialysis, were included if they underwent duplex ultrasound examination to evaluate preoperatively the vascular status and diameters for radiocephalic arteriovenous fistulae (RCAVF) construction. The associations between the diameter of the radial artery and cephalic vein and primary failure at six weeks, primary and secondary patency at one year were investigated. RESULTS: There was no significant association between either radial artery diameter or dilated cephalic vein diameter and primary failure. There was an association between radial artery diameter and primary patency (Overall P=0.042). Males had a significantly larger mean radial artery diameter than females (P=0.005). Gender did not influence primary patency. CONCLUSION: We recommend using radial artery diameters of > or = 2.1 mm and < or = 2.5 mm for RCAVF construction, this diameter category having the highest patency at 1 year. A single cut-off guideline cannot be recommended.

[Consensus on the concepts of cortical, subcortical and frontal dementia. Research by national and international dementia experts]. / Consensus over de begrippen corticale, subcorticale en frontale dementie. Een onderzoek onder nationale en internationale dementie-experts.

The level of agreement concerning the concepts cortical, subcortical and frontal dementia. The level of agreement between experts in the field of dementia concerning cortical, subcortical and frontal dementia was established. Nowadays these syndromes are implemented in clinical practice; the discussion about the validity and reliability of these concepts however has diminished. Forty-one national and international dementia experts of four disciplines completed a questionnaire, based on the cognitive section of the CAMDEXR. For each syndrome they marked whether the cognitive function mentioned was impaired or unimpaired in cortical, subcortical and frontal dementia. The level of agreement between experts was determined by use of a derivative of the kappa-coefficient. Cortical dementia was characterised by high levels of agreement between the experts. With an observed level of agreement of 0.76, experts reached the highest consensus about this syndrome. Less agreement was observed in the judgements of subcortical and frontal dementia, with observed levels of agreement of 0.64 and 0.67 respectively. No differences were found in the assessments of national and international experts, as well as between the participating disciplines. Apparently, the application of these syndromes in clinical practice is difficult. Because of this confusion the practical meaning is limited, and one may wonder wether these concepts must still be used in clinical practice.

Flow measurements in dialysis shunts: lack of agreement between conventional Doppler, CVI-Q, and ultrasound dilution.

BACKGROUND: Measuring flow in dialysis shunts is recommended to predict imminent thrombosis. Multiple methods for measuring blood flow are in use. Numerous ultrasound protocols exist which determine volume flow using a conventional Doppler (CD) frequency shift analysis technique. All of these are subject to potentially large errors. Quantitative colour velocity index (CVI-Q) does not make use of the Doppler equation and is more precise in vitro. Ultrasound dilution (UD) measures access flow during dialysis in a non-operator-dependent way. The aim of the present study was to compare these three methods of measuring access flow in vivo for agreement with each other. METHODS: In 38 accesses flow was measured by CD, CVI-Q, and UD. All measurements were done during dialysis. Agreement was determined by intraclass correlation coefficient (ICC=R(i)) and Bland-Altman analysis. RESULTS: ICC between UD and CVI-Q was R(i)=0.56. ICC between UD and CD was R(i)=0.10, and ICC between CD and CVI-Q was R(i)=0.16. Bland-Altman analysis revealed a bias (mean difference) of -38 ml/min between UD and CVI-Q, a bias of 1129 ml/min between UD and CD, and a bias of 1167 ml/min between CVI-Q and CD. CONCLUSIONS: CD measurements did not agree with UD or CVI-Q much higher values were recorded with the former than with the latter two techniques. The agreement between UD and CVI-Q measurements is low but reasonable. Caution must be applied in comparing and interpreting values of access flow measured by different techniques.

Peripheral haemodynamics and renal function in relation to the menstrual cycle.

1. The objective of this study was to investigate whether the luteal phase of the menstrual cycle differs from the follicular phase by the development of a state of general vascular relaxation. 2. Once in the follicular and once in the luteal phase of the menstrual cycle, we measured by non-invasive techniques: arterial blood pressure (by finger blood pressure measurements), vascular tone (by pulse-wave velocity and plethysmography), blood flow to skin (by laser-Doppler), blood flow to forearm (by plethysmography) and blood flow to kidneys (by para-aminohippurate clearance), and the glomerular filtration rate (by inulin clearance). The data points obtained in the luteal phase were compared with those in the follicular phase by non-parametric tests. 3. Arterial blood pressure, vascular tone and the blood flows to the forearm and kidneys were comparable in the two phases of the menstrual cycle. In contrast, the blood flow to the skin was consistently lower, and the glomerular filtration rate higher in the luteal phase of the menstrual cycle. 4. The results of the present study do not support our hypothesis of a general vascular relaxation in the luteal phase of the menstrual cycle. The lower skin flow in the luteal phase may be an adaptation needed to ensure the higher core temperature of 0.3-0.5 degree C in the luteal phase. The higher glomerular filtration rate was in most case paralleled by a higher renal blood flow in the luteal phase. This suggests that the higher glomerular filtration rate is secondary to a selective vasorelaxation of the afferent renal arterioles.