Determination of the dynamic behaviour of the cephalic vein in healthy volunteers: intravenous pressure measurements and simultaneously transverse B-mode ultrasound measurements for lumen-area calculations (pilot study)

Hemodialysis dependent patients, suffering from end-stage renal disease, need a
well-functioning vascular access to connect them with the dialyzer. Usually,
the vascular access is surgically created by making a connection between an
artery and a vein (arteriovenous fistula = AVF). Due to the low resistance and
the high arterial-venous pressure difference, an increase in vessel diameter
and flow is expected. Preferably an autogenous wrist AVF (between the radial
artery and the cephalic vein) is constructed, due to its better long-term
patency and its smaller complication rate. If six weeks postoperatively
cannulation is not possible (venous diameter < 4 mm, flow < 500 ml/min) an AVF
is not well maturated. Despite the fact that all those patients are selected
based on preoperative diagnostics (duplex, physical examination and CE-MRA),
30-50% of all newly created wrist AVFs fail, and are useless for hemodialysis.
For the planning of the type of vascular access for each individual patient, it
is very important to preoperatively predict the postoperative flow increase and
vessel remodeling. When insufficient vessel remodeling is likely, based on
preoperative diagnostics, another type of vascular access can be chosen. A
patient-specific computer simulation model, based on preoperative MRA, duplex
data, non-invasive blood pressure, and cardiac output measurements can possibly
give insight in the postoperative blood flow increase and failure incidence for
different fistula configurations.
This computer model will be further developed as a part of the ARCH project.
Data from this study will serve as input for the improved model. The response
of the venous diameter to increased blood pressure as a result of AVF
construction has a great influence on the predictive value of the model.
Currently a linear relationship between pressure and diameter is assumed.
However, in-vivo studies on the cephalic vein show a non-linear relationship.
Also the viscoelasticity of the venous wall is neglected in the current model,
despite the fact that in-vitro and in-vivo experiments on various veins show
viscoelastic behaviour. For characterization of this dynamical behaviour it is
crucial to measure the blood pressure instantaneously, thus intravenously.
Because of the fast pressure changes it is essential to measure the exact
pressure without temporal or spatial misalignment. It is also important to
perform the ultrasound measurements simultaneously in order to retrieve a
direct relationship between the instantaneous pressure and the ultrasound data.
Due to the elliptical cross-section of the cephalic vein, especially for low
pressures, transverse B-mode ultrasound measurements are necessary in order to
obtain the lumen-area. The pressure in the cephalic vein is altered by using a
congestion cuff around the upper arm. In order to define the reproducibility
and reliability of the study method, this current research protocol will be
only performed on healthy male volunteers.

The goal of this pilot study is to determine the dynamic behaviour of the
cephalic vein in healthy volunteers by using intravenous pressure measurements
and simultaneously transverse B-mode ultrasound measurements for lumen-area
calculations.

All included volunteers will be treated by the standard protocol. This means
that pressure in the cephalic vein will be varied during about 45 minutes by
using a congestion cuff around the upper arm. The congestion pressure will be
raised to different pressure (10, 20, 30, 40, 50, 60, 70, 80 mmHg),
subsequently the congestion cuff will be deflated. This will be repeated
several times, simultaneously recording the intravenous pressure and the
lumen-area. In order to define the reproducibility of the study method, this
standard protocol will be repeated on day 14.

An ultrasound research with an intravenous blood pressure measurement will be
performed on all included patients. The research time will be about 45 minutes,
with a two week follow-up.
The ultrasound measurements are free of risks. However, puncturing the
cephalic vein with a Venflon catheter could lead to haematoma formation. Also
there is a minimal chance on very rare complications, like superficial
thromboflebitis. This is an infection of a superficial vein, like the vena
cephalica, which results in pain and skin redness or inflammation around the
vein. Most of the time treatment is not necessary; sometimes ointment will help
to ease the symptoms. An aseptic procedure will be performed by using sterile
material. To reduce the chance of haemotoma formation, the wound will be
compressed after removal of the Venflon catheter.
Although this research has no personal benefits for the volunteers,
they contribute to the development of a better model for prediction of
successful vessel adaptation and AVFs. So they possibly contribute to a better
treatment of renal patients on hemodialysis in the future.