Vein catheter for coaxial blood stream and use of a split needle for its introduction in a vein

An intravenous catheter comprising an inner return tube (1) having return mouth or tip (2) and attached to the return tube (1) an outer access or draw-off tube (3) having draw-off openings (4), where tube (3) and openings (4) are arranged around and coaxial with the inner tube (1), at least along that part which in use is to be inside the vein (8), whereby the distal end of the return tube (1) extends beyond the distal end of the access tube (3), the distance between the return mouth (2) and this distal end preferably being at least twice the width of an approved stasis band.

The present application relates to a intravenous catheter for coaxial 
bloodflow, especially for use in stem cell aferesis from peripheral blood. 
The catheter according to the present invention is particularly suitable 
for aferesis with a view to extracting white blood cells and will be 
described below with reference to this technology, but the catheter may 
also be used in the continuous withdrawal from and return to the body of 
blood which is treated with a view to isolating, for example, blood 
platelets or various types of white blood cells. 
The invention also relates to the use of a split needle for the insertion 
of this intravenous catheter into a vein. 
Stem cells are immature cells which under given circumstances can be 
stimulated to divide and differentiate to a plurality of more mature cells 
with very different functions. 
Within the context of the invention the term "stem cells" is used to denote 
cells which are the basis of the cellular elements of blood. These stem 
cells give rise to red blood cells, white blood cells and platelets and 
are crucial to the continued and continuous production thereof. 
Without stem cells, the levels of white blood cells would drop continuously 
and unhindered to a dangerously low level, thereby exposing the individual 
to life-threatening infections that would eventually result in death. 
In the same way red cells would gradually die, resulting in death due to 
lack of oxygen in the tissues. 
The level of platelets would also fall and potentially fatal bleeding would 
ensue. 
Cancer can affect cells in the blood, both the stem cells and the later 
developed, more mature cells. By killing off the blood forming cells with 
either cytostatics or radiation, and subsequently introducing new stem 
cells, the patient may be completely cured and health restored to normal. 
These new stem cells may be taken from another human being (allogenous 
transplantation) or extracted from the patient (and purified of cancerous 
cells) prior to the cell destruction procedure. After this procedure the 
cells are reintroduced (autologous transplantation). 
Today there is an increasing demand for stem cells as the above-mentioned 
stem cell based modes of therapy are developed. Stem cells can be taken 
from a donor or a patient in two ways. 
The first method is based on the stem cells being taken from the bone 
marrow. Bone marrow harvesting requires general anaesthesia and often 
produces nausea and local pain in the area of incision through the bone 
after the procedure. This method also calls for more personnel and 
material resources. The stem cells harvested will also take longer to 
establish a thriving, functional bone marrow than stem cells collected 
from peripheral blood. Risks of infections and other complications are 
ever-present. 
All these drawbacks have resulted in an extensive use of a second method, 
namely harvesting stem cells from peripheral blood, and on the basis 
thereof stem cell aferesis has been developed. 
Some of the stem cells in the bone marrow percolate into the bloodstream, 
and normally only a tiny fraction of the white blood cells in the 
circulating blood are stem cells. In the bone marrow 0.01 to 0.05% of the 
cells are stem cells and this percentage is even smaller in the peripheral 
blood. 
However, this amount can be increased considerably if the stem cells are 
mobilised into the bloodstream with different kinds of drugs or factors. 
This forms the basis for harvesting stem cells from peripheral blood by 
processing blood taken from a superficial vein immediately below the skin 
(as opposed to a "central" large vessel deep inside the body and/or close 
to the heart). 
This technology is called Peripheral Blood Stem Cell Aferesis", PBSC 
aferesis. 
In principle, there are two techniques in current use: 
1. A suitable amount of blood, normally 400 to 500 ml, is drawn into a 
machine in a sterile system and processed, a comparatively small amount 
containing stem cells being held back before the main bulk of the blood is 
returned to the donor or patient through the same needle. The same 
procedure is then repeated until a sufficient number of stem cells has 
been harvested. This technology is called Intermittent Flow Cytaferesis, 
ICF. 
2. The second method is based on blood being drawn from one vein and 
returned to another vein continuously, normally using a vein in both arms, 
whilst the blood is processed with a view to stem cell extraction, in the 
machine. This technology is called Continuous Flow Cytaferesis, CFC. 
The blood drawn from the body is processed by spinning in a suitable 
apparatus, normally either a centrifugal bowl or a ring-formed channel. 
Owing to the different specific gravity of the various components of the 
blood, on centrifugal separation the red cells will be located furthest 
from the centre. Closer to the centre are the white blood cells, the 
platelets and the plasma in that order. 
The stem cells are in the white blood cell layer and can be collected in 
different ways after centrifugal separation. 
In some IFC machines the separated elements are run through some plastic 
tubes starting centrally from the top of the centrifugal bowl. Plasma is 
then sent through the tubes first, and the other elements follow in the 
reverse order to that mentioned above. Optical density sensors can then 
detect the different components, and by using different values the desired 
components can then be channelled into separate collection bags, whilst 
the rest is returned to the patient or donor. 
The CFC machine has a spinning channel and after the separation of the 
components has been established, the collection begins. 
The narrow line between the red blood cells and plasma represents the white 
blood cells, and this area is called the interface. 
It is very important that this interface is stable before collection 
begins. Any irregularity or abrupt change in the flow parameters 
(different pumps and valves, changes in the access or return flow from the 
donor or patient) will cause undulation of this interface, thereby 
lowering considerably the number of stem cells collected. 
This is due to the way in which the stem cells today are collected in this 
system. Here, a straw-like tube is positioned exactly in this interface, 
and is used to "suck out" at a very low flow-rate white blood cells 
containing stem cells. 
Today's "single needle" system, as will be described in more detail below, 
causes major disturbances of this interface and is therefore not 
recommended. 
However, a system where only one needle is used is highly recommendable 
because of the vastly increased patient or donor comfort associated with 
such a system. 
As such aferesis, i.e., the collection of cells, takes 4 to 5 hours, and 
sometimes needs to be carried out over two days to obtain enough stem 
cells, having to keep the elbow stretched and immobilised for so long can 
be quite uncomfortable and sometimes even painful for the patient or 
donor. 
As far as is known there is today no system or needle which is adapted 
especially for the purpose of stem cell CFC. The system available, 
marketed by Gambro, comprises a Y-shaped needle, which as far as is known 
is the only needle made for single venous access in a peripheral vein, but 
this needle is made for aferesis of blood platelets. Blood is drawn from 
the vein through the needle and is processed in the machine before being 
pumped to a collection chamber with a pressure sensor. When a threshold 
pressure is reached the access pump stops and the return pump starts up. 
The blood is then returned to the patient or donor. The volume in the 
collection chamber is very small, so there is a frequent change in the 
direction of flow, access I return. Furthermore, the same lumen (i.e., 
needle) is used for access and return blood, i.e., for unprocessed and 
processed blood. In principle this is a form of intermittent flow 
cytaferesis, but the large fluctuations in volume from the donor is 
avoided. The very large fluctuations in the flow of return and access 
blood, as mentioned above, causes unmanageable undulations in the 
interface. This needle is therefore useless for stem cell CFC, and even 
for platelet aferesis such needles are often not used because they tend to 
lower the yield of the platelets. 
So-called venflons can also be used, although they are not designed for 
this purpose. In any one case a venflon must be inserted into each arm, 
one for access blood and one for return blood. Naturally, this limits 
considerably patient or donor comfort and the danger of spilling blood is 
present when the tubes are connected to the needle. Sterile conditions are 
therefore difficult to maintain. 
As indicated, the traditional system is a metal needle or cannula in each 
elbow vein. This is a simple, easy method based on the needles used in 
ordinary bleeding of donors. However, if this system is used the donor 
must keep his arms stretched and immobilised for the duration of the 
aferesis, and this can be extremely unpleasant if the aferesis lasts for 
several hours. If the arm is moved, the needle may easily fall out of the 
vein, or even penetrate the other vein wall, causing bleeding in the 
surrounding tissue. Naturally, the aferesis must then be halted 
immediately. 
The other system that has been used is based on catheters inserted into a 
central vein, that is a large vein, close to the heart. This approach 
calls for skilled doctors, anaesthetists or surgeons, an operating theatre 
and an intensive care ward nearby, and in addition considerably more 
sterile equipment than required when withdrawing blood from peripheral 
blood vessels. 
The method is time-consuming, requires local anaesthesia and is much more 
expensive, In addition, the procedure for inserting the central catheter 
carries a risk of more serious complications. For instance, other vital 
structures may be perforated, e.g., the lungs, major arteries, nerves etc. 
Of course, the more skilled the personnel are, the lower the risk. 
However, because of the prevailing problems, this procedure is only used 
on patients who are donating stem cells to themselves. 
There is therefore a great need for a safe, efficient and sterile system 
which is easy to use and where the patient or donor preferably may move or 
flex the arm in use. 
Accordingly, the present invention relates to a intravenous catheter for 
coaxial bloodflow, of the type mentioned above, and this catheter is 
characterised in that it comprises an inner return tube having a return 
mouth and an outer access or draw-off tube with draw-off openings, where 
draw-off tubes and openings are arranged around and substantially coaxial 
with the inner tube, at least along the part which in use will be inside 
the vein, whereby the distal end of the return tube extends beyond the 
distal end of the access tube, the distance between the return mouth or 
tip and this distal end being preferably at least twice the width of an 
approved stasis band. 
The distance between return tip and draw-off opening is preferably 6 and 
most preferably about 8 cm. 
As mentioned the invention relates to the use of a split needle for 
insertion of the intravenous catheter described above in to a vein, 
preferably in the elbow. 
From the prior art in this field reference will made to: 
1. U.S. Pat. No. 4,096,860, which describes an encatheter for biaxial flow, 
primarily intended for a haemodialysis process. The patent describes a 
form of hub having an end piece positioned inside the blood vessel. The 
hub is inserted with the aid of a hypodermic needle through the centre of 
the hub and attached thereto by means of a threaded connection. After 
insertion, the hypodermic needle and associated syringe may be drawn out 
in such a way that the end piece of the hub remains inside the blood 
vessel. 
Backflow is prevented by a centrally positioned elastic flap or valve, 
secured by means of an expansion ring. When the syringe has been drawn 
out, the central tube for backflow of processed blood is inserted. This 
will go somewhat further in than the hub end piece. 
The device is relatively complicated and does not seem to allow continuous 
withdrawal of unprocessed blood and return of processed blood. 
The patent describes a device consisting of very many individual parts, 
which in addition are in movable relation with one another, i.e., a 
relatively complex and thus costly apparatus, and furthermore, the system 
is one which must be characterised as open. 
In contrast to this, according to the invention there is provided a 
catheter which can be made as one unit without movable parts, flaps, 
special screw or attachment means. 
The insertion does not take place with the aid of a conventional syringe or 
hypodermic needle, and furthermore conventional clips on the tubes, both 
the return and access tubes will suffice to prevent backflow. The catheter 
is suitable preferably for being integrated in an aferesis set and it is 
thus possible to provide a fully closed system, which distinguishes the 
subject of the invention from the prior art described above and all other 
prior art. 
2. U.S. Pat. No. 4,666,426, which describes a catheter for coaxial flow and 
having a capacity of as much as 600 ml per minute, designed to be placed 
in the vena cava very close to the heart, i.e., a central venous access. 
The catheter may be as much as 65 to 70 cm in length. Furthermore, there is 
a description of a two-way connecting member in the rear part of the 
catheter, and in addition a separate mechanism for stopping the bloodflow 
as required. This mechanism is shown in the form of a V-flap device. The 
catheter consists of a plurality of parts and suffers therefore from the 
same defects as the US patent discussed above, and nor can the patent now 
under discussion be deemed to be a closed system since there are several 
possibilities of connection. 
The inventive subject described in '426 is intended for central venous 
access in large and central veins such as the vena femoralis or femoral 
vein. All dimensions and descriptions are adapted to this purpose and the 
device is definitely not suitable for the area in which it is the 
objective of the present invention to work, viz., continuous withdrawal 
from and return to peripheral veins, preferably elbow veins, with the 
possibility of applying a stasis. Nor does the patent describe any 
possibility for closed systems and or for any simple and safe insertion 
method which makes possible-routine use of blood bank personnel.

FIG. 1 shows an area around the elbow where superficial veins are 
indicated. The band 8 represents an elastic stasis. The skin is penetrated 
at arrow B and, when the catheter of the invention is in place, the tip of 
the return tube will be approximately at the point indicated by arrow A. 
The vein is deliberately drawn straight as in nature it often bends in 
various directions and may also be branched. The mouth of the return tube 
preferably has slightly rounded edges, and it might also be an advantage 
if a form of coil is incorporated in the return tube wall, as this can 
ease the insertion of the catheter. The elasticity makes it possible for 
the patient or donor to bend his elbow somewhat once the catheter is in 
place, which of course makes the aferesis more comfortable. 
The two alternatives in FIG. 2 show the principle of two possible 
configurations of the area where the outer access or draw-off tube 3 is 
concentrically secured to the return tube 1 which lies within and runs the 
length thereof. 
The access tube 3 has in its distal end close to the area of attachment to 
the return tube 1 a form of a peripheral bulb 10 or bead equipped with 
access or draw-off openings 4. The shape and structure of the bulb are 
essential to its function. Specifically, the transition areas between the 
bulb 10 and the return tube 1, in both the upstream and downstream 
direction are markedly oblique, in order to facilitate insertion into a 
vein 8 and also withdrawal therefrom. 
The maximum radius of the bulb 10 here is so large that at the point of 
maximum radius it will abut or lie close to the internal wall of the vein 
8. Normally, this will be sufficient to cause the bulk of the blood flow 
to leave the vein 8 and enter the access tube 3 through the opening 4 for 
conveying to a non-illustrated processing apparatus with subsequent return 
through the return tube 1. 
The cavity of the bulb 10 may act as a temporary reservoir for the blood, 
so that fluctuations in the intravenous blood flow are levelled out, 
although this function may not be very important. FIG. 2a) shows an 
embodiment where essentially the entire cavity of the bulb 10 is used for 
the collection of blood and where upstream or downstream of the point of 
maximum radius there are provided access openings 4 to the access tube 3. 
Holes downstream may necessitate use of a stasis if the access tube and 
bulb internally abut the vein wall. 
FIG. 2b) shows an alternative embodiment, where the area of transition from 
the essentially circular-cylindrical upstream part of the unit is slightly 
sharper, and where the inner lower part of the bulb 10 is filled with a 
plastic material, and where the downstream "bottom" of the access tube 3 
is rounded to aid smooth bloodflow. 
Any combinations or variations of the embodiments shown in FIGS. 2a) and b) 
are conceivable, bearing in mind of course the desired objectives, namely 
to be able to withdraw blood from the vein 8 smoothly and continuously, 
without interruptions and also without the bulb 10 collapsing because of 
negative pressure which is created from the processing apparatus situated 
downstream. 
A collapse of this kind can be counteracted by the embodiment shown in FIG. 
2b), where the cavity in the distal end of the bulb 10 on the access tube 
3 in the area of attachment to the return tube is filled with a plastic 
material. 
FIGS. 3, 4 and 5 show embodiments of the inventive intravenous catheter 
where an attempt has been made to give the catheter a slimmer form in 
order to facilitate the penetration of the access tube through the skin 
and into the vein. 
FIG. 3 shows an embodiment where the access tube 3 has been placed on the 
outside of the return tube 1 and where the access openings are in the form 
of slits 4. 
These slits must not be too long as blood may be spilled if insertion into 
the vein is too slow. 
FIG. 4 shows an embodiment where a tube downstream is used as return tube 
1, whilst upstream of the access openings 4 it serves as access tube 3. 
The upstream part of the return tube 1 is passed as a separate tube through 
the wall in the part serving as access tube and exactly downstream of the 
access opening 4 is attached internally to the tube which now constitutes 
the return tube 1. 
FIG. 5 shows a combination of the embodiments in FIGS. 3 and 4, inasmuch as 
the radius of the access tube downstream of the access openings has been 
made slightly larger, thereby producing a slightly increased volume of 
blood. 
The insertion procedure for the inventive catheter will be described in 
greater detail in FIGS. 6a) to 6l). 
FIG. 6a) shows an insertion needle 5 in the form of a split needle, which 
in a starting position encircles the return tube I and the return mouth 2. 
The tip 6 of the needle 5 has penetrated the skin 7. 
FIG. 6b) shows the situation once the needle 5 has been inserted further 
and has penetrated into the vein 8. Venous blood will now flow into the 
return mouth 2 and flow in the direction of the processing machine. How 
far back the blood is allowed to flow can be controlled by conventional, 
non-illustrated clips, which can be manipulated in a simple manner to be 
opened and closed as desired. 
FIG. 6c) shows the situation when the needle 5 is fully inserted into the 
vein 8. It is not until this point that the return tube 1 should be pushed 
into the split needle 5. 
In FIG. 6d) the return tube 1 begins to penetrate into the vein. 
In order to ensure a smooth and problem-free insertion into the vein 8, it 
is an advantage if the mouth 2 of the return tube 1 has slightly rounded 
edges, and it might also be an advantage if the walls of the return tube 
are slightly stiffened, for example, by means of a suitable coil. 
At this point it is of crucial importance that the insertion needle 5 is 
held still and in position so that it does not slip out of the vein 8 or 
perforate the vein wall. FIG. 6e) shows a situation where the return tube 
1 has been passed so far into the vein 8 that the withdrawal of the needle 
5 may begin and the needle is gradually pulled all the way out, as shown 
in FIGS. 6f) and g). 
In FIG. 6h) the insertion needle 5 has split fully into two parts and has 
been disposed of, and the insertion of the return tube 1 continues as 
indicated in FIG. 3i), which shows the situation immediately prior to the 
access tube 3 with its oblique shape being ready for insertion through the 
skin 7 and into the vein 8. 
A situation of this kind is shown in FIG. 6l). The bulb 10 of the access 
tube 3 in the distal end pierces through the skin 7 because of its oblique 
shape and the skin seals the widened hole after the passage of the bulb 
because of its inherent elasticity. Once the bulb 10 of the access tube 3 
and associated openings 4 are inside the vein 8, blood will begin to flow 
into the access tube 3 in the direction of the processing machine. Again, 
conventional, non-illustrated clips may be used to regulate the backflow 
as desired. 
FIG. 6k) shows the situation when both the return tube 1 and the access 
tube 3 have been put in place inside the vein 8. A possible sterile bag 12 
(see below, FIG. 5) may now be removed and the parts of the apparatus that 
are outside the body are connected to tubings which run to and from the 
processing apparatus. For this purpose, the return tube 1 is now passed 
out of the access tube 3, as indicated to the left in FIG. 6l). 
To build up pressure in the vein 8 and to prevent an excess of blood from 
flowing past the openings 4 of the access tube 3, a stasis 9 is applied 
approximately half way between the distal bulb 10 of the access tube 3 and 
the distal mouth or tip of the return tube 1. The free end of the return 
tube 1 is preferably at least twice the width of an approved stasis band 
9, and most preferably the return tube 1 has a free part in the vein which 
is about three times the width of an approved stasis band 9. 
In this position the blood 8 flows from the machine through the access tube 
3. The arterial pressure, that is the pumping effect of the dynamic muscle 
contractions in conjunction with the unidirectional valves in the vein, 
guarantees a slight positive pressure of about 20 mm Hg in the vein. The 
blood flows "slowly" back towards the heart. It is this bloodflow that 
must be interrupted so that the blood enters the access openings 4, whence 
the blood is drawn to the processing machine. The venous bloodflow is 
reestablished on the other side of the catheter of the invention. To 
increase intravenous pressure around the opening 4 of the access tube 3 a 
stasis is applied. With the aid thereof it is ensured that in addition to 
increased pressure non-processed and processed blood are not mixed. The 
vessel walls cling to the return tube 1 at the stasis site. Pressure is 
applied both to the subcutaneous tissue area and to the deep tissue area, 
however the vein 8 suffers no damage because the aferesis using this 
method requires a relatively short time. 
It should be unnecessary to mention that the catheter of the invention is 
made of a medically speaking compatible material. 
The internal diameter of the return tube 1 should be about 1.2 to 1.4 mm. 
The flow resistance must be adapted to the pumping effect of the machine, 
and since resistance is inversely proportional to the square of the 
radius, this is a critical point as the diameter is of course also limited 
by normal vein sizes. The resistance is also proportional to the length of 
the tube, but a free length of the return tube 1 in the vein 8 downstream 
of the distal end of the access tube 3 of about 6 to 10 cm, preferably 8 
cm, has proved to be favourable according to the invention. A further 
limitation on the external diameter of the return tube 1 is of course the 
vein size, seen in connection with the distal end and bulb 10 of the 
access tube 3. 
The return tube 1 must be made of a material that has sufficient mechanical 
strength to resist the pressure that is applied when a stasis is applied 
and, as mentioned above, this can be achieved by, for example, embedding a 
coil of a suitable material in the return tube 1. 
The insertion needle 5 for first inserting the return tube 1 and then the 
access tube 3 in a vein 8 is illustrated in FIGS. 7a) to d). 
FIG. 7a) shows a split needle 5 in the form of a pointed sleeve encircling 
the distal end of the return tube 1. At the rear edge the needle is 
equipped with two wings 13 of a conventional type to facilitate the grip 
around and insertion of the needle 5 into a vein 8. 
When the needle, as shown in FIG. 3 c) is fully inserted into the vein 8, 
the return tube 1 is pushed forward, as shown in FIGS. 6d) and 7b). The 
distal end of the insertion needle permits free passage of the return tube 
1, as indicated by an arrow in FIG. 7b). 
After sufficient insertion of the return tube 1 into the vein 8, the split 
needle 5 is drawn back, as indicated in FIGS. 6f), 6g) and 7c), and 
finally the split needle 5 is split completely as indicated in FIG. 7d), 
whereupon the two parts are disposed of. 
The split needle 5 is of a conventional type per se where the two halves 
are secured to one another in a suitable manner along the diametrically 
disposed, longitudinal seams. 
Well-trained health personnel have no difficulties in manipulating this 
type of needle. 
Finally, FIG. 8 shows a possible packaging unit where everything which is 
upstream of the insertion needle 5 is enveloped by a stocking or bag 12. 
The catheter of the invention and also the bag 12 are of a material which 
permits sterilisation, and when in addition the insertion needle 5 is 
enveloped by a nonillustrated protective sleeve, which allows 
sterilisation of the catheter and needle, this means that the unit of the 
invention and associated equipment can be delivered in a sterile condition 
for rapid, speedy connection to machines. Since the device in addition is 
so simple that it can be used by reasonably well-trained health personnel, 
this means that this mode of treatment can be moved from hospitals and out 
among the general public, i.e., to, for example, local health centres, 
which in turn will mean a considerable improvement of efficiency with a 
view to being able to use to a maximum the resources which are represented 
by voluntary blood donors.