Catheter with changeable number of lumens

A catheter assembly is provided. An attachment structure has a proximal end portion of an outer cannula attached to it. A needle is insertable through the outer cannula and the attachment structure. An inner cannula is attached to an inner cannula attachment region of the attachment structure. The inner cannula is insertable axially through the attachment structure. The attachment structure can comprise two hubs, one for the outer cannula and the other for the inner cannula, the two hubs being attachable to one another to form the overall attachment structure. A valve structure is associated with the attachment structure, suitably with the outer cannula hub. The valve structure normally closes communication between an access passage in the attachment structure, e.g., in the outer cannula hub, and the outer cannula lumen. The valve structure opens sufficiently for the inner cannula to pass through it and to open communication between the access passage and the outer cannula lumen when the inner cannula is inserted through another passage in the attachment structure and through the outer cannula lumen. The assembly allows the removal of the inner cannula and the insertion of a replacement inner cannula, if desired, without removing the outer cannula from the blood vessel. Use of a relatively small diameter needle for a desired diameter outer cannula can also be provided if the material of the outer cannula is such that it will swell in place.

TECHNICAL FIELD 
The present invention relates to a catheter assembly which includes an 
outer cannula which is insertable into a body conduit such as a vein. The 
number of lumens through which samples can be drawn, medicaments 
introduced or test probes can be inserted can be varied by the physician 
without removing the outer cannula from the blood vessel. In one 
embodiment the outer cannula is insertable utilizing an over-the-needle 
(as opposed to the over the wire) insertion technique. 
BACKGROUND OF THE INVENTION 
Currently there is a need for multi-lumen catheters for a variety of 
therapies where multiple drug injections are required. Unfortunately, 
current multi-lumen catheters are positioned in place utilizing a 
procedure which is bloody, complicated and potentially hazardous to both 
the patient and the practitioner, especially during central venous 
catheterization. 
A problem with current catheter systems is that once they have been 
inserted they must be completely removed and replaced if one wants to have 
more (or less) or cleaner lumens. Thus, a messy and uncomfortable 
procedure may have to be repeated on a patient whose body is already under 
stress. 
Another problem with existing multi-lumen catheters is that all of the 
method of inserting them cause blood loss that is dangerous to both the 
patient and the practitioner. The most common method is to utilize a 
needle to locate and pierce the blood vessel. A guide wire is then 
inserted through the needle into the blood vessel. The needle is then 
removed leaving the guide wire in place. The insertion site if often 
enlarged by sliding a dilator sheath down the guide wire to stretch open 
the skin and the vessel wall. The multi-lumen catheter is then slid along 
over the guide wire and through the now enlarged opening formed by the 
dilator sheath. Once the catheter has reached the proper location the 
guide wire and the dilator sheath are removed. The dilator sheath must be 
removed because its size and stiffness are a potential cause of serious 
injury (perforation, irritation) to the blood vessel. 
Another current alternative is to directly expose and partially transect a 
vein whereby the catheter may be directly inserted into the vein. This can 
be a very blood procedure and infection can easily set in. 
As mentioned above, another problem with current multi-lumen catheters of 
the nature disclosed above is that if one wishes to change from, for 
example, a two lumen catheter to a three lumen catheter, or if one wishes 
to change the size of the lumens, this can only be accomplished by 
removing the catheter which is in place and replacing it with another 
catheter utilizing one of the above mentioned bloody and dangerous 
techniques. 
A catheter system marketed by Arrow International, Inc. under the trademark 
Arrow-Flex allows for the insertion and removal of an inner cannula 
through a septum and through the lumen of an outer cannula. This system 
is, however, designed only for a very short term of use (during an 
operation) and can only be left in place at great risk to the patient. The 
outer cannula is made from a stiff polymer to aid in the forceful 
insertion procedure required to stretch the skin and blood vessel. Also, 
any liquids being flowed through the outer cannula lumen (i.e., through 
the annular space between the inner and outer cannulae) must be introduced 
downstream of the septum whereby the space immediately downstream of the 
septum (and upstream of the introduction of the liquid) is substantially 
stagnant. Furthermore, the fact that this space is not flushed out means 
that if the fluid being flowed through the outer cannula lumen is changed, 
there will be a transition time during which a mixture of the old and new 
fluids will be present. As some medicaments are not compatible with others 
such mixing can be undesirable. 
Yet further, the multi-lumen catheters of the prior art have generally been 
fabricated of materials which are relatively stiff in order to allow them 
to be inserted and which thereafter remain relatively stiff while they are 
within the patient's body. As a result, these catheters can cause 
perforation of major veins which can result in death. For this reason 
these types of catheters are removed as soon as possible and replaced with 
softer catheters for the ongoing delivery of medicaments. 
The present invention is directed to overcoming one or more of the problems 
as set forth above. 
DISCLOSURE OF INVENTION 
One embodiment of the invention is in the nature of an over-the-needle 
insertable multi-lumen catheter assembly. The assembly comprises an 
attachment structure having proximal and distal end regions, first and 
second internal passages which join one another at a junction region to 
form a distal exit passage, an outer cannula attachment region of a size 
and construction sufficient to allow a needle to be inserted therethrough, 
an inner cannula attachment region, a first proximal access region 
providing access to the first passage, a second proximal access region 
providing access to the second passage and an exit passage access region 
providing access to the distal exit passage. The assembly also includes an 
outer cannula having proximal and distal end portions and an outer cannula 
lumen, the proximal end portion of the outer cannula being attached to the 
outer cannula attachment region, the outer cannula lumen being of a size 
sufficient to allow the needle (and if desired an intermediate dilator) to 
be inserted therethrough. Also included is an inner cannula having 
proximal and distal end portions and an inner cannula lumen, the proximal 
end portion of the inner cannula being attached to the inner cannula 
attachment region in such a manner as to block fluid flow communication 
between the first proximal access region and the outer cannula lumen, the 
inner cannula being insertable axially through the first passage and the 
outer cannula lumen, the inner cannula being of a construction lumen, the 
inner cannula being of a construction such that when inserted into the 
outer cannula lumen it does not prevent flow therethrough. In addition 
there is valve means associated with the attachment structure for closing 
communication between the second passage and the outer cannula lumen, the 
valve means being openable sufficiently for the inner cannula to pass 
therethrough and to open up communication between the second passage and 
the outer cannula lumen. 
In accordance with another embodiment of the invention a catheter structure 
is set forth with which the number of available lumens can be changed 
without removal from a patient's body. The catheter structure comprises an 
outer cannula hub having proximal and distal end portions, a passageway 
therethrough from the distal to the proximal end portion thereof and an 
outer cannula attachment region. Also present is an inner cannula hub 
having proximal and distal end portions, a first internal passage 
therethrough from the distal to the proximal end portion thereof and a 
second internal passage which joins the first internal passage at a 
junction region, an inner cannula attachment region, the distal end 
portion of the inner cannula hub being releasably couplable to the 
proximal end portion of the outer cannula hub with the first internal 
passage in the inner cannula hub in communication with the passageway 
through the outer cannula hub. Also provided is an outer cannula having 
proximal and distal end portions and an outer cannula lumen, the proximal 
end portion of the outer cannula being attached to the outer cannula 
attachment region so that the outer cannula extends distally from the 
outer cannula hub. Further included is an inner cannula attached to the 
inner cannula attachment region in such a manner as to block fluid flow 
communication between the proximal and distal end portions of the first 
passage, the inner cannula having proximal and distal end portion, the 
distal end portion thereof being insertable through the passageway in the 
outer cannula hub from the proximal end portion thereof and out of the 
distal end portion thereof. The catheter structure additionally includes 
an elastomeric septum having a self-sealing opening therethrough 
associated with the outer cannula hub for closing communication between 
the second passage and the outer cannula lumen, the distal end portion of 
the inner cannula being insertable through the opening through the septum. 
Furthermore, inner cannula sheathing means are provided for preventing the 
septum from exerting inward radial pressure on the inner cannula when the 
inner cannula distal end portion is inserted through the opening in the 
septum, the sheathing means also providing communication between the 
second passage in the inner cannula hub and the outer cannula lumen. 
In accordance with another embodiment yet of the invention a catheter 
structure is set forth with which the number of available lumens can be 
changed without removal from a patient's body. The catheter structure 
comprises an outer cannula hub having proximal and distal end portions, a 
passageway therethrough from the distal to the proximal end portion 
thereof and an outer cannula attachment region. Also present is an outer 
cannula hub having proximal and distal end portions, a first internal 
passage therethrough from the distal to the proximal end portion thereof 
and a second internal passage which joins the first internal passage at a 
junction region, an inner cannula attachment region, the distal end 
portion of the inner cannula hub being releasably couplable to the 
proximal end portion of the outer cannula hub with the first internal 
passage in the inner cannula hub in communication with the passageway 
through the outer cannula hub. Also provided is an outer cannula having 
proximal and distal end portions and an outer cannula lumen, the proximal 
end portion of the outer cannula being attached to the outer cannula 
attachment region so that the outer cannula extends distally from the 
outer cannula hub. Further included is an inner cannula attached to the 
inner cannula attachment region in such a manner as to block fluid flow 
communication between the proximal and distal end portions of the first 
passage, the inner cannula having proximal and distal end portion, the 
distal end portion thereof being insertable through the passageway in the 
outer cannula hub from the proximal end portion thereof and out the distal 
end portion thereof. The catheter structure additionally includes an 
elastomeric septum having a self-sealing opening therethrough associated 
with the outer cannula hub which serves for closing communication between 
the second passage and the outer cannula lumen, the distal end portion of 
the inner cannula being insertable through the opening through the septum. 
An opening member is provided along with positioning means for positioning 
the opening member in the opening through the septum. The second passage 
in the inner cannula hub communicates with the outer cannula lumen 
responsive to positioning of the opening member in the opening in the 
septum. The opening member also prevents the septum from exerting inward 
radial pressure on the inner cannula when the inner cannula distal end 
portion is inserted through the opening in the septum. 
Yet another embodiment of the invention is a catheter structure which 
comprises an attachment structure having proximal and distal end regions, 
first and second internal passages which join one another at a junction 
region to form a distal exit passage, an outer cannula attachment region, 
an inner cannula attachment region, a first proximal access region 
providing access to the first passage, a second proximal access region 
providing access to the second passage and an exit passage access region 
providing access to the distal exit passage. The catheter structure 
further comprises an outer cannula having proximal and distal end portions 
and an outer cannula lumen and being formulated of a material that softens 
with a softening ratio of greater than 2:1, the proximal end portion of 
the outer cannula being attached to the outer cannula attachment region. 
Also included is an inner cannula having proximal and distal end portions 
and an inner cannula lumen and being formulated of a material that softens 
with a softening ratio of greater than 2:1, the proximal end portion of 
the inner cannula being attached to the inner cannula attachment region in 
such a manner as to block fluid flow communication between the proximal 
and distal end portions of the first passage, the inner cannula being 
insertable axially through the first proximal access region and the first 
passage. Further provided is valve means associated with the attachment 
structure for closing communication between the second passage and the 
outer cannula lumen, the valve means being openable sufficiently for the 
distal end portion of the inner cannula to pass therethrough and to open 
communication between the second passage and the outer cannula lumen. 
Still another embodiment of the invention is a catheter assembly comprising 
an outer cannula hub having proximal and distal end portions and defining 
a central longitudinal passageway therethrough having proximal and distal 
end portion, the passageway extending from the outer cannula hub proximal 
end portion to the outer cannula hub distal end portion. The assembly 
includes an outer cannula having proximal and distal end portions and 
defining an outer cannula lumen extending from the outer cannula proximal 
end portion to the outer cannula distal end portion, the outer cannula 
proximal end portion being attached to the outer cannula hub with the 
outer cannula lumen in flow communication with the outer cannula hub 
passageway. The assembly also includes an inner cannula hub having 
proximal and distal end portions and defining first and second passageways 
therethrough. Also present is an inner cannula having proximal and distal 
end portions and defining an inner cannula lumen extending from the inner 
cannula proximal end portion to the inner cannula distal end portion, the 
inner cannula proximal end portion being attached to the inner cannula hub 
with the inner cannula lumen in flow communication with the inner cannula 
hub first passageway and such that fluid flow from the inner cannula hub 
first passageway can only proceed through the inner cannula lumen. 
Attaching means are provided for detachably attaching the inner cannula 
hub to the outer cannula hub with the inner cannula positioned within and 
extending longitudinally along the outer cannula lumen. In addition, valve 
means is associated with the outer cannula hub for blocking communication 
between the proximal end portion of the outer cannula hub passageway and 
the outer cannula lumen, the valve means being openable in response to the 
inner cannula hub being attached to the outer cannula hub, the valve 
means, when opened, providing flow therethrough from the inner cannula hub 
second passageway to the outer cannula lumen. 
A further embodiment yet of the invention is a catheter structure with 
which the number of available lumens can be changed without removal from a 
patient's body. The embodiment comprises an outer cannula hub having 
proximal and distal end portions, a passageway therethrough from the 
distal to the proximal end portion thereof and an outer cannula attachment 
region. The embodiment also includes an inner cannula hub having proximal 
and distal end portions, a first internal passage therethrough from the 
distal to the proximal end portion thereof and a second internal passage 
which joins the first internal passage at a junction region, an inner 
cannula attachment region, the distal end portion of the inner cannula hub 
being releasably couplable to the proximal end portion of the outer 
cannula hub with the first internal passage in the inner cannula hub in 
communication with the passageway through the outer cannula hub. Also 
present is an outer cannula having proximal and distal end portions and an 
outer cannula lumen, the proximal end portion of the outer cannula being 
attached to the outer cannula attachment region so that the outer cannula 
extends distally from the outer cannula hub. Additionally, an inner 
cannula is attached to the inner cannula attachment region in such a 
manner as to block off fluid flow communication between the proximal and 
distal end portions of the first passage, the inner cannula having 
proximal and distal end portions, the distal end portion thereof being 
insertable through the passageway in the outer cannula hub from the 
proximal end portion thereof and out of the distal end portion thereof. 
Also, an elastomeric septum is present having a self-sealing opening 
therethrough associated with the outer cannula hub for closing 
communication between the second passage and the outer cannula lumen, the 
distal end portion of the inner cannula being insertable through the 
opening through the septum. An opening member is provided which is adapted 
to open the opening in the septum when positioned therein. Moving means 
serve for moving the opening member into the opening in the septum and 
thereby providing fluid flow communication between the second passage and 
the outer cannula lumen. 
The catheter structures of the present invention have a number of 
advantages over prior art devices. A very significant advantage is that 
one can change the number and size of the lumens without withdrawing the 
cannula from the patient's blood vessel. Another very significant 
advantage is the fact that the cannula can be made to be insertable in an 
over-the-needle fashion. This means that for the same diameter cannula one 
can utilize a smaller needle and can, in fact, make a smaller puncture 
wound in a blood vessel. Furthermore, if one uses a softening outer 
cannula in accordance with a preferred embodiment of the present 
invention, of softening outer and inner cannulae, the catheter structure 
can be left in place for relatively long periods of time due to the 
reduced potential of damaging the vessel when utilizing the softenable 
cannulae. Still further, if one utilizes a catheter structure in 
accordance with a preferred embodiment of the present invention which has 
both its inner and outer lumen swell when it is inserted in a blood 
vessel, one can utilize a stall smaller needle thus significantly further 
reducing trauma. And, construction of a catheter assembly in accordance 
with the present invention is relatively inexpensive and simple.

BEST MODE FOR CARRYING OUT INVENTION 
The present invention provides a multi-lumen catheter assembly 10 (FIG. 5) 
which can be inserted using an over-the-needle technique, as illustrated 
in, for example, FIGS. 1-4. Referring to FIG. 1, the insertion assembly 11 
includes a needle hub 12 having a proximal end portion 14 and a distal end 
portion 16. A needle 18 is attached to extend distally from the needle hub 
distal end portion 16. 
In FIG. 1 an outer cannula hub 22 is shown which has a proximal end portion 
24 and a distal end portion 26. The distal end portion 16 of the needle 
hub 12 fits within the proximal end portion 24 of the outer cannula hub 
22. An outer cannula 28, which has a proximal end portion 30 and a distal 
end portion 32, has its proximal end portion 30 attached to an outer 
cannula attachment region 31. The outer cannula 28 extends from the distal 
end portion 26 of the outer cannula hub 22. The needle 18 fits through an 
internal lumen 34 (FIG. 2) of the outer cannula 28 and extends beyond the 
distal end portion 32 of the outer cannula 28. Suitably the needle 18 will 
fit snugly but slidingly within the inner lumen 34 of the outer cannula 
28. For ease and clarity of illustration the needle 18 and the internal 
lumen 34 are illustrated as having a somewhat larger gap between them. 
In accordance with the invention an insertion assembly 11 as illustrated in 
FIG. 1 is inserted a desired distance into a selected blood vessel, 
normally a vein, after which the needle hub 12 is withdrawn leaving behind 
the outer cannula hub 22 and the attached outer cannula 28. In a manner 
which will be discussed below, blood flow is but off at the outer cannula 
hub 22 so that no significant bleeding results. 
FIGS. 3 and 4 illustrate an inner lumen positioning assembly 38. The 
positioning assembly 38 is in the nature of an inner cannula hub having a 
first internal passage 40 and a second internal passage 42 which join one 
another at a junction region 44. The inner cannula hub 38, in the 
embodiment illustrated having a Y-shape, includes a distal end region 46. 
A first proximal access region 48 provides access to the first passage 40. 
A second proximal access region 50 provides access to the second passage 
42. An inner cannula 52 has a proximal end region 54 and a distal end 
region 56 (FIG. 5). The proximal end region 54 of the inner cannula 52 is 
attached with its inner lumen 58 (FIG. 6) in flow communication with the 
first internal passage 40 of the inner cannula hub 38 but free from 
communication with the second internal passage 42 of the inner cannula hub 
38. 
FIGS. 4 and 5 illustrate a multi-lumen catheter assembly 10 (in inserted 
form) in accordance with an embodiment of the present invention. It is 
produced by inserting the assembly 11 of FIG. 1 in a blood vessel, 
withdrawing the needle 18 and needle hub 12 and inserting the positioning 
assembly 38 of FIG. 3. The inner cannula 52 is positioned within the outer 
cannula 28 (FIGS. 3 and 4). The distal end portion 56 of the inner cannula 
52, in the embodiment illustrated, extends beyond the distal end portion 
32 of the outer cannula 28. In this manner non-compatible medicaments can 
be introduced into a blood vessel or other body cavity a spaced distance 
apart from one another. Or, samples can be removed from a region of the 
vessel or cavity which is free of a particular medicament which is being 
introduced via another lumen. 
FIG. 6 illustrates the fact that an annular passage 60 between the outer 
cannula 28 and the inner cannula 52, which is the remaining available 
portion of the outer cannula lumen 34, can serve as a passage for 
introducing or extracting fluid from a blood vessel. In addition, the 
inner lumen 58 can be used for this purpose. The inner lumen 58 and the 
passage 60 can alternatively be used for introduction and/or extraction of 
sensors, surgical apparatus, fiber optics, etc. 
As may be seen in FIGS. 3 and 4 the junction region 44 serves to form an 
exit passage 62 to which access is provided by an exit passage access 
region 64. The distal end region 46 of the inner cannula hub 38 may be 
seen to be connectable to the proximal end portion 24 of the outer cannula 
hub 22, for example utilizing a Luer locking mechanism 66 to accomplish 
the connection. Other connecting mechanisms can also be used including a 
simple siding fit. As will also be noted an inner cannula attachment 
region 68 is provided which is adapted to be connected to the proximal end 
portion 54 of the inner cannula 52, for example by a press fit or plastic 
welding technique. This connection is upstream of the junction 44 whereby 
the lumen 58 of the inner cannula 52 is not in flow communication with the 
second internal passage 42 of the inner cannula hub 38. 
FIGS. 3 and 4 also illustrate the outer cannula tub 22 and valve means 70 
which can be associated with the outer cannula hub 22 and which serves for 
normally closing communication between the second passage 42 of the inner 
cannula hub 38 and the outer cannula lumen 34. The valve means 70 is 
openable sufficiently for the inner cannula 52 to pass through it. When 
the valve means 70 is open it also opens up flow communication between the 
second passage 42 and the outer cannula lumen 34, the flow communication 
being accomplished in a manner which is described immediately below. 
The particular valve means 70 illustrated includes a self-sealing septum 
72, a spring 74 and a shuttle 76 which includes a tubular portion 78 which 
on compression of the spring 74 extends through a self-sealing opening 80 
in the self-sealing septum 72. The tubular portion 78 has an inner 
diameter 81 sufficiently large so that the inner cannula 52 can pass 
through it and can leave an annular space 79, of generally about the size 
of the annular passage 60, open between the inner cannula 52 and the 
tubular portion 78. It is through the annular space 79 that flow 
communication is provided between the second passage 42 and the outer 
cannula lumen 34. 
Operation of the valve means 72 is apparent from comparison of FIGS. 3 and 
4. In FIG. 3 the distal end region 46 of the inner cannula hub 38 has not 
been slid within the proximal end portion 24 of the outer cannula hub 22. 
Once this occurs, as seen in FIG. 4, the tubular portion 78 will have been 
forces through the self-sealing opening 80 in the self-sealing septum 72 
thereby both opening the annular space and preventing pressure from being 
applied by the septum 72 to the inner cannula 52 which might cause it to 
be shut off. This allows the insertion of a relatively soft inner cannula 
52 or of an inner cannula 52 which softens on being inserted in a blood 
vessel. It should be noted that in the embodiment illustrated in FIGS. 3 
and 4 the inner cannula 52 passes through the self-sealing opening 80 in 
the self-sealing septum 72 before the shuttle 76 is moved so as to force 
the tubular portion 78 therethrough. Thus, the inner cannula 52 should 
have sufficient stiffness, at least when initially inserted, so as to be 
able to be forced through the self-sealing opening 80. It should be noted 
that the valve means 70 provides a virtually bloodless manner for changing 
intravenous connection. Furthermore, it eliminates the need for clamping 
or kinking tubing during such exchanges. Still further, the chances of air 
emboli or bleeding due to accidental disconnection of an IV (intravenous) 
set is significantly reduced. Moreover, infusion and aspiration can be 
carried out rather than only one or the other. Yet further, the apparatus 
as illustrated accepts standard luers and fits in standard luers. 
It is also important to understand that flow from the second passage 42 
into the outer cannula lumen 34 washes through and cleanses the valve 
means 70 thereby eliminating any dead space which would be present if the 
flow into the outer cannula lumen 34 was introduced downstream of the 
valve means 70. 
While the inner cannula hub 38 is illustrated as opening the valve means 70 
in FIGS. 3 and 4, it should be recognized that the inner cannula hub 38 is 
merely illustrative of one type of access member which can provide access 
through the valve means 70. It may be desirable to open the valve means 70 
for other reasons. For example, it may be desirable to insert a radiopaque 
wire through the valve means 70 so as to be able to measure the length of 
cannula which will be needed to reach a particular portion in a blood 
vessel. Accordingly, the invention includes such a mechanism and method. 
FIGS. 7, 8 and 9 illustrate an embodiment of the present invention wherein, 
in addition to the previously mentioned outer cannula 28 and inner cannula 
42, a further inner cannula 82 is present within the lumen 58 of the inner 
cannula 52. The further inner catheter 82 has its own further inner lumen 
84. Between the inner cannula 52 and the further inner cannula 82, a 
passage 86 exists through which fluids, etc., can be introduced or 
withdrawn. Thus, the configuration of FIGS. 7-9 provides for the 
introduction or extraction of three fluids, etc., one through the passage 
60, one through the passage 86 and one through the lumen 84. And, the 
respective distal end portions 88 of the further inner cannula 82, 56 of 
the inner cannula 52 and 32 of the outer cannula 28 can have openings 
which are spaced apart from one another whereby medicaments, etc., can be 
inserted and/or samples can be withdrawn and/or nutrient solution can be 
inserted at spaced distances apart from one another for reasons which have 
been discussed previously. In the embodiment of FIGS. 7-9 the inner 
cannula 52 has been attached to the inner cannula hub 38 in the manner 
shown in FIG. 4 and an additional inner cannula hub 138 has been added 
which includes its own valve means 70 which can be of the nature shown in 
FIGS. 3 and 4, through which the further inner catheter 82 can be 
inserted. It will be obvious that this type of concentric insertion can be 
continued to the extend desired and the only limiting factor is the size 
of the outer cannula 28 which may be inserted in the patient's blood 
vessel. FIG. 8 illustrates the resulting assembly. 
FIGS. 10-12 illustrate an embodiment of the present invention much like 
that of FIGS. 1-6, but wherein the inner cannula 52 is divided into two 
lumens, 90 and 92 thereby providing three different passages, namely the 
passage 60 and the lumens 90 and 92, for introduction and extraction of 
fluids, etc., from a blood vessel. As can be seen in FIG. 12 the distal 
end portion 56 of the inner cannula 52 can advantageously made to be blunt 
ended. One advantage is that when the distal end portion 56 is blunt ended 
(and generally smooth) the intima of the blood vessel is less likely to be 
damaged during insertion of the inner cannula 52 as compared with 
inserting an open ended cannula. Also, if desired a radiopaque member 97, 
generally a piece of metal or material loaded with radiopaque filler, may 
be encased in a distal end 100 of the inner lumen 52 (in lumen 90 and/or 
lumen 92), the radiopaque member 97 serving to provide a marker which 
allows location of catheter assembly 10 at a desired position within a 
blood vessel. 
In the embodiment shown in FIG. 12 the lumen 92 opens at lateral opening 93 
located farther distally along the distal end portion 56 of the inner 
cannula 52 than does the lumen 90 which opens at lateral opening 95. Also, 
the opening to passage 60 is at the end of the distal portion 32 of the 
outer cannula 28 and is a spaced distance proximally from the opening 95. 
In this manner spaced apart introduction and/or extraction of fluids, 
etc., is provided. 
In the embodiment of FIGS. 10-12 it is not necessary to have an additional 
valve means 70. Instead, an additional inner cannula hub 94 is provided 
having a first internal passage 96 communicating with the lumen 90 and 
having a second internal passage 98 communicating with the lumen 92. It 
should be noted that while the passage 90 and 92 are shown to be each 
substantially semicircular in shape any other desired shape can be 
utilized. Or, separate tubes can be provided within the inner cannula 52, 
each having a different exit. Spaced apart introduction and/or extraction 
of fluids, etc., is provided as with the other embodiments of the 
invention. An additional valve means 70 is not required. 
As has been alluded to it is advantageous if the outer cannula 28 is formed 
of a material which softens and which swells to increase both its size and 
the size of its lumen 34 on being inserted into a blood vessel. Generally, 
it is preferred that the outer cannula 28 softens by a factor (2.4% Secant 
Modulus ratio) of at least about 2:1, preferably at least about 3;1, upon 
insertion. There are also advantages in having the inner cannula 52 soften 
by a like amount upon insertion. Alternatively, the inner cannula 52 can 
simply be formulated of a soft material to begin with. This serves to 
further reduce irritation to the intima of a blood vessel. Also, the outer 
cannula 28 preferably is fabricated from a material that swells in volume 
by a factor of at least about 1.3:1 on being inserted in a blood vessel. 
This provides the advantage of allowing the use a smaller needle 18 to 
insert a cannula of a desired and significantly larger size making 
possible over-the-needle insertion of multi-lumen catheters. The inner 
cannula 52 can also swell so long as it does not swell enough to block off 
flow through the outer cannula lumen 34 or through the tubular member 78. 
In the case of cannula which soften on being inserted in a blood vessel it 
may be desirable to provide coatings on such cannula where they pass 
through the patient's tissue near the vein wall so as to prevent any 
kinking from occurring. 
In a preferred embodiment, the catheter assembly comprises a cannula of a 
desired or adjustable length with outer and inner circumferences which 
increase and/or of a material whose 2.5% Secant Modulus decreases when 
inserted in a patient. 
the cannulae (inner and outer) of the invention can be of any material 
suitable for introduction into a living subject. Preferably, these 
materials are polymeric in nature and are selected to be sufficiently 
stiff for insertion. In general, the cannulae should, when inserted have a 
2.5% Secant Modulus greater than about 20,000 N/cm.sup.2 and preferably 
greater than about 28,000 N/cm.sup.2 to prevent buckling or wrinkling upon 
insertion into the subject. Even more preferred are those compositions 
which soften or exhibit a decreased 2.5% Secant Modulus upon, for example, 
exposure to liquids, insertion of the distal end portion of the cannula 
into the body of a living subject and its maintenance therein, or exposure 
to a temperature from about 20.degree. C. to about 40.degree. C. 
Particularly, preferred compositions absorb liquid (i.e., hydrate) and 
thereafter soften to a 2.5% Secant Modulus of less than 7,000 N/cm.sup.2 
which reduces the trauma to the surrounding tissues of the subject. The 
inner cannula can simply have a 2.5% Secant Modulus of less than 7,000 
N/cm.sup.2 to begin with. The term softening ratio is used herein to refer 
to the ratio of the 2.5% Secant Modulus values of the composition selected 
in the form of a tubular cannula initially to the 2.5% Secant Modulus of 
the composition when softened. It is preferred that at least a portion of 
such compositions are hydrophilic. It is also preferred that the 
composition soften when a softening ratio of at least about 2:1. 
Examples of softening polymers useful in the practice of the invention are 
those described in U.S. Pat. Nos. 4,883,699, issued Nov. 28, 1987 and 
4,911,691, issued Mar. 27, 1990, both of which are incorporated herein by 
reference. The preferred composition for the cannula comprises: 
(a) a first phase which comprises a substantially non-hydrophilic polymeric 
component; and 
(b) a second phase which comprises a hydrophilic polymeric component; 
the material (i) being capable of absorbing water to an extent that its 
softens with a softening ratio of at least about 2:1 and/or swells with a 
swelling ratio of at least about 1.3:1; and (ii) when substantially 
completely hydrated, having an energy to break of at least about 700 
N-cm/cm.sup.3 and a 2.5% Secant Modulus of less than about 7,000 
N/cm.sup.2. 
Also useful are those softening polymers described in U.S. Pat. Nos. 
4,359,558; 4,424,305; 4,454,309 and 4,439,583 of Tyndale Plains-Hunter 
Ltd. incorporated herein by reference. The preferred cannula composition 
essentially comprises a polyurethane diacrylate composition having from 
about 90 to about 65 weight percent of a hydrophilic polyurethane resin 
and from about 10 to about 35 weight percent of a diacrylate. 
An alternative material which may be utilized as a cannula material is a 
thermoplastic composition with softenable and/or shaped-memory properties. 
Such polymeric compositions are described, for example, in the following 
articles: Softenable, Shape-Memory Thermoplastics for Biomedical Use, 
Robert S. Ward, M.D. 7 D, August 1975; and Thrombroresistant, Radiopaque, 
Softenable Thermoplastics Catheter Compounds With Shape-Memory Properties, 
R. S. Ward, K. A. White, J. S. Riffle, Second World Congress On 
Biomaterials, 10th Annual Meeting of the Society For Biomaterials, 
Washington, D.C., Apr. 27,-May 1, 1984. The aforementioned thermoplastic 
compositions comprise a base polymer that is a block or segmented 
co-polymer thermoplastic with at least one block type with an abrupt 
effective glass transition temperature (T.sub.g) at or greater than room 
temperature, but less than approximately body temperature. The remainder 
of the base polymer contains hard blocks whose dominant thermal transition 
is substantially greater than body temperature. The cannulae can also be 
made to expand and soften as follows. The cannulae are originally made 
with their eventually desired expanded internal diameter and then are 
heated above the glass transition temperature (T.sub.g), drawn out to form 
longer and thinner cannulae and held in this state until cooled below the 
glass transition temperature. Once the longer and thinner cannulae have 
warmed to a temperature that is greater than room temperature but less 
than approximately body temperature, i.e., once the cannulae have reached 
the glass transition temperature, the shape-memory properties operate and 
the cannulae increase in internal and external diameter while shrinking in 
length. 
It is also preferred when selecting such softening materials of the 
cannulae that such materials also swell wherein at least a portion of the 
cannula inner cross-section of the duct and/or outer circumference of the 
cannula increases to form an enlarged inner cross-section of the duct 
and/or enlarged outer circumference of the cannula when inserted in a 
living subject and maintained therein and/or when the duct is contacted by 
a liquid for a period of time sufficient for the enlarged duct 
cross-section and/or outer circumference to form. Preferably, the duct 
cross-section increases from about 25% to about 400%. 
The composition of the cannula may be cross-linked if desired. 
Cross-linking give the composition strength wherein the melting or 
softening points of the uncross-linked polymeric components permit 
sterilization of the catheter assembly using a cannula of such composition 
at above such temperature. Cross-linking of the material selected for the 
cannula may also be used to adjust the 2.5% Secant Modulus of the 
composition to a desired value. Cross-linking may also increase the 
tensile energy to break of the material which has been softened. 
Cross-linking can also be used to minimize extractable components of the 
composition. 
Cross-linking can be effected by use of an appropriate cross-linking agent 
or by radiation, preferably in the presence of a cross-linking promoter, 
such as triallyl isocyanourate or the like. Or, the material can be 
cross-linked by high energy gamma or beta radiation. 
The material of the cannulae may contain additional ingredients such as 
stabilizers, antioxidants, radiopacifiers, medicaments, fillers or the 
like. For certain applications it may be advantageous to incorporate a 
water soluble or water dispersable medicament which can leach from the 
material when it contacts the fluids of the living subject. Such 
medicaments include anti-thrombogenic agents, antibiotics, antimicrobial, 
antiviral agents, anticoagulants, anti-inflammatory agents, and the like. 
A cannulae selected such that it swells or softens should not do so 
appreciable during the time it is being inserted in a living subject or 
the like. It is preferable that such cannulae's swelling or softening time 
should be at least about 15 seconds and preferably at least about 60 
seconds. 
The swelling of the cannula has several advantages. Swelling of the cannula 
permits insertion of a smaller device for equivalent fluid flow and/or can 
result in pressure around a wound site reducing bleeding and bacterial 
invasion into the wound and prevent catheter slip out, a common cause for 
changing catheters prematurely. Increased cross-section of the cannula 
duct also permits increased flow through the cannula and/or the 
positioning of a larger inner cannula when compared with similar 
non-swelling cannula of identical initial dimensions. This allows access 
to smaller areas such as the veins in the limbs and easier insertion into 
the selected site. Further, if the cannula is fed into the blood vessel 
using an inserter having a channel through which the cannula is fed, 
swelling of the cannula may increase the outer circumference sufficiently 
that it becomes as great as the diameter of the inserted channel. After 
insertion of the cannula this may be desirable. The inserter then looses 
its ability to slide relative to the cannula due to the pressure of the 
cannula against the inserter channel. This is advantageous in preventing 
relative movement of the cannula and inserter. Once the inserter is 
attached (e.g., by taping) to the subject, further movement of the cannula 
in or out of the subject is limited. Cannulae which becomes soft are also 
advantageous. A soft cannula tends to cause less irritation to the intima 
(lining of the vein) and to the insertion site and is less likely to 
contribute to mechanical phlebitis. The softness of the cannula also 
permits it to float in a vein rather than lie on the point where inserted 
and consequently any infusion is delivered evenly helping to avert 
chemical phlebitis. 
Industrial Applicability 
The present invention provides an over-the-needle multi-lumen catheter 
assembly 10 which is particularly useful for inserting multi-lumen cannula 
into veins such as the superior vena cava. 
While the invention has been described in connection with specific 
embodiments thereof, it will be understood that it is capable of further 
modification, and this application is intended to cover any variations, 
uses, or adaptations of the invention following, in general, the 
principles of the invention and including such departures from the present 
disclosure as come within known or customary practice in the art to which 
the invention pertains and as may be applied to the essential features 
hereinbefore set forth, and as fall within the scope of the invention and 
the limits of the appended claims.