A catheter intended for the administration of an anesthetic into a body space and methods of use such as introduction within the interpleural space are disclosed. According to the disclosure, the catheter is constructed so that only a soft distal portion resides within the body space. A relatively stiff portion joined to the relatively soft portion is intended to extend from the relatively soft portion through the dense body tissue to the proximal end of the catheter. A bio-compatible resin providing a softness of about 80A to 100A Rockwell is used for the relatively soft distal portion. A bio-compatible resin providing a catheter portion having a durometer value of about 65D to about 75D Rockwell is used for the relatively stiff portion. The relatively soft portion avoids damage to the delicate body tissue bounding the space whereas the relatively stiff portion resists kinking or collapse, both within the relatively stiff body tissue and outside the body. Spaced apart reference markings are provided on the relatively stiff portion of the catheter in position to provide a visual indication of the amount of the relatively soft distal portion that is within the body space.

FIELD OF THE INVENTION 
This invention relates to catheters intended for the administration of 
local anesthetic into a body space, more particularly to a catheter 
designed to avoid trauma to delicate body tissue within the space while 
remaining in place for prolonged periods of time. 
BACKGROUND OF THE INVENTION 
Catheters of the kind referred to are particularly useful for the 
administration of medicaments, more particularly for the continuous 
administration of anesthesia within the epidural or intra-pleural 
(interpleural) spaces. In each application, the space involved is 
relatively long and narrow and is relatively inaccessible except in a 
direction which is at an angle relative to the long axis of the space. In 
each instance, nerves and relatively delicate body tissues are involved 
which are subject to trauma, producing paresthesia and in some cases 
considerable discomfort and permanent injury due to disturbance of the 
relatively delicate tissue bordering the space. In extreme cases, 
puncture, irritation or erosion of the tissue can result. 
In the use of intra-vascular catheters, relatively short, soft distal tips 
for catheters for venous and arterial use have recently come into use as a 
means of avoiding vessel puncture and the dislodgment of plaque with the 
vessel. In these applications, substantially all of the catheter dwelling 
within the vessel must be relatively stiff due to the need to guide and 
turn the catheter tip within the vessel. Because of this limitation, the 
soft tip employed on an intra-vascular catheter has at most been about one 
to one and one half centimeters in length. Catheters of this type have not 
been recognized or considered to be adaptable for use within the epidural 
or intrapleural spaces because the relativelY stiff material comprising 
the major part of the catheter may damage the delicate tissues within the 
space. Further, the restlessness of patients to whom anesthesia is 
administered by intra-pleural and epidural techniques increases the risk 
that the soft tip will become separated from the body of the catheter, 
particularly since the catheter may reside within the space over a period 
of many days or even weeks. 
SUMMARY OF THE INVENTION 
With the foregoing in view, the present invention provides a catheter which 
has an elongated soft distal section intended to reside within a body 
cavity and a substantially stiffer, kinkresistant, proximal section 
extending proximally from a junction with the distal section. Preferably 
the junction with the distal section comprises a relatively short 
intermediate section in which polymers of the distal and proximal portions 
are bonded by the application of sufficient heat to cause the materials to 
freely flow together in a large bond area thereby integrally joining the 
softer distal end portion to the stiffer proximal portion. Preferably the 
stiffer proximal portion is provided with one or more indicator markings 
spaced from the tip to enable the anesthesiologist to make certain that 
only the relatively soft distal portion is within the body space and that 
the relatively stiff section is within the relatively dense tissue 
proximally of the body space and outside the body. Preferably the soft 
portion is long enough so that it extends into the relatively dense tissue 
by a centimeter or two so as to provide a relatively soft buffer zone. 
Since the requirement for anesthetic administration (either intermittently 
or continuously) may remain for a prolonged period extending as long as a 
week or more, the relative stiffness of the section of catheter proximally 
of the soft portion provides resistance to kinking or collapsing and 
interruption of flow caused by patient restlessness. To insure that the 
tip will not become separated from the remainder of the catheter, care 
must be taken that a strong bond exists between the relatively soft tip 
portion and the relatively stiff portion. Preferably this is accomplished 
by abutting the two sections together and applying heat sufficient to 
effect a flowing together of the relatively stiff and the relatively soft 
resins within a relatively short transition zone of approximatelY one 
sixteenth of an inch in length. Although longer transition zones may be 
provided, the transition zone must not be too long, i.e. two to three 
centimeters, since there is a risk that it would project outside the body 
when the tip is positioned. 
Preferably, the relatively stiff portion of the catheter is formed of a 
polyurethane resin having a durometer reading of about 68D Rockwell. 
Resins ranging in stiffness from about 65D to about 75D may be employed. 
For certain procedures an elongated stiffening wire stylet may be provided 
for use in the introduction of the catheter. If the stylet is employed, 
its distal end should not enter the relatively soft distal end portion. 
In a preferred mode of use of the catheter for intra-pleural administration 
of anesthesia, a skin wheal is raised at the chosen puncture site and a 
small skin nick made to facilitate penetration. A curved-tip needle such 
as a 17 gauge needle of the Husted type with stylet inserted is introduced 
at a 30 degree to 40 degree angle to the skin into the intercostal space 
just above the upper edge of the lower rib. The needle is advanced in the 
medial direction with the cutting edge upwardly after perforation of the 
caudal intercostal membrane, which can be identified bY the distinct 
resistance it offers. Upon removal of the needle stylet, a syringe is 
attached to the needle with the plunger retracted between about 2-4 
centimeters. The needle is advanced slowly. When the parietal pleura is 
perforated the syringe plunger will begin to return to the non-retracted 
position due to the negative pressure within the pleural space. The 
syringe is then removed and the distal tip of the catheter quickly 
threaded through the needle. When the tip of the catheter reaches the 
curved point of the needle, a slight increase in pressure is felt which 
indicates that the catheter is about to enter the pleura. At that point a 
first reference mark on the catheter will substantially coincide with the 
needle hub. Subsequent pressure to advance the catheter should be minimal. 
When a more remote reference mark coincides with the needle hub, the 
catheter has been inserted 5 centimeters into the pleura. Thereafter, the 
needle is removed while maintaining the catheter in place; the catheter is 
then coiled into a strain loop and fixed in place, a syringe is attached 
in the usual manner and the anesthetic administered as required. 
A similar procedure is employed for catheterization of the epidural space 
although a stiffening stylet is preferably fitted within the lumen of the 
catheter, the stylet distal tip terminating short of the softer distal 
portion. As is recognized in the art, in the use of epidural catheters, 
the hanging drop method or the loss of resistance technique are employed 
in determining penetration of the dura.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
With reference to the drawings, a catheter is shown by way of example as 
being introduced into the pleural space for administration of anesthetic, 
such as for the administration of bupivacaine solution for pain relief in 
a patient with multiple rib injuries. Other procedures, such as anesthetic 
administration within the epidural space, are also contemplated with the 
present invention. The catheter formed according to the teachings of the 
invention is shown at 10 and is formed of biocompatible, radio opaque 
resin materials. Preferably the catheter is about 90 centimeters in length 
and is about 19 gauge in diameter. Such a catheter is illustrated as being 
introduced through a 17 gauge curved-tip needle 11. 
Catheter 10 is of substantially uniform outer diameter and has a single 
lumen extending lengthwise thereof to an exit port 12 in the distal tip 
through which anesthetic solution or other medication is adapted to be 
administered. Additional lumens may be provided if required. The proximal 
end of the catheter 13 is initially not provided with any fitting so as to 
allow for complete withdrawal of the needle over the catheter and removal 
once the catheter is in place. After the needle is withdrawn and removed, 
the proximal end of the catheter can then be fitted into a 
catheter-syringe adapter and a syringe attached for injection of the 
anesthetic as required. 
According to the invention, the catheter 10 is comprised of a relatively 
long distal tip section 13, formed of a biocompatible resin. A critical 
feature of the tip portion is that the tip be of relatively soft material 
throughout the length intended to reside within the body space so as to 
avoid irritation and damage to delicate tissue. Preferably a biocompatible 
resin providing a tip section having a durometer reading of about 93A 
Rockwell is employed. A suitable biocompatible resin is an aliphatic 
polyurethane manufactured by Thermedics under the trademark TECOFLEX or a 
similar resin of Dow Chemical Company. Aromatic polyurethanes such as 
Tellethane, also from Dow Chemical Company, may be employed. From the 
biocompatible resins specified above, relatively soft resins having a 
specified durometer value of from 8OA to 1OOA Rockwell may be employed. 
The tip section should preferably be at least 4 centimeters up to about 8 
centimeters in length, although the length may vary in practice. An 
insertion length of about 5 centimeters in length for administration of 
anesthetic within the pleural or epidermal spaces with an extra centimeter 
or two to insure that only the soft portion is within the space has proven 
to be satisfactory. 
The relatively soft distal portion 13 is joined to a relatively rigid 
proximal portion 14 which extends to the proximal end of the catheter. 
Preferably the relatively rigid 14 portion is also formed of a 
bio-compatible polYurethane resin. Excellent results are obtainable 
utilizing a aliphatic polyurethane resin as identified above and capable 
of producing a catheter material having a durometer reading of about 68D 
Rockwell. A material of this stiffness has proved to be sufficiently 
resistant to kinking and collapse under normal conditions of use so that 
closure of the lumen by kinking or by pressure from the relatively dense 
bodY tissue in which this portion of the catheter is to reside is avoided. 
Others of the resins noted above having a Rockwell value of 65D to 75D may 
be employed. The stiffer out-dwelling portion also resists kinking or 
collapsing outside of the body, which is especially critical when the 
catheter is used in the epidural technique where the patient is apt to lie 
on the catheter for a prolonged period of time. 
Preferably, the relatively soft distal end portion and the relatively long 
and rigid portion are joined together by heat and pressure sufficient to 
form an intermediate section or transition zone, perhaps about 
one-sixteenth of an inch in length in which the relatively stiff resin and 
the relatively soft resin interface, forming a strong bond over a 
relatively large surface area, which will not separate during the 
relatively long time that the catheter may remain in place. 
In order to properly position the distal tip of the catheter within the 
space, and to insure that no part of the more rigid, relatively long 
section does not enter the space, and cause trauma to delicate tissue, it 
is preferred that the catheter be provided with spaced apart reference 
marks to visually indicate the location of the tip. For example, a first 
reference mark 15 is located on the catheter body so that when it is 
adjacent the hub of the needle, it will indicate to the anesthesiologist 
that the tip of the catheter coincides with the tip of the needle. A 
second marking 16, spaced proximally from the first by the insertion 
length of the soft distal end section, will indicate to the user that the 
approximate length of the distal end of the catheter has been inserted 
into the space when the second marking 16 is adjacent the hub. Additional 
markings intermediate the first two markings may be provided if desired. 
In use of the catheter in the administration of the anesthetic in the 
intra-pleural space, a curved-tip needle 11 is inserted at the chosen 
intercostal space as seen in FIG. 1. Once the needle tip is properly 
positioned within the space, the catheter is threaded through the needle 
hub and advanced until the first reference mark 15 reaches the hub of the 
needle. This will indicate that the distal tip of the catheter is about to 
exit from the needle tip. The user should experience less resistance once 
the catheter exits from the needle tip and is advanced into the 
intrapleural space. Once the marking 16 is adjacent the needle hub, as 
seen in FIG. 2, the appropriate amount of soft catheter is within the 
pleural space, no further advancement should be attempted as to avoid any 
risk that the relatively rigid catheter material may be entering the 
space. At this point the needle is removed and separated from the catheter 
as seen in FIG. 3.