A multi-lumen epidural catheter includes a flexible inner tube 10 having a tip opening 12 and a surrounding flexible outer tube 11 having a pair of side openings 13 spaced upstream from the tip. An anesthetic solution may be injected through the separate flow and discharge paths defined by this structure to deaden a more elongate zone of a patient in a precisely controlled manner.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a multi-lumen epidural catheter suitable 
for use in continuous epidural anesthesia, more particularly to a 
double-lumen epidural catheter capable of controlling anesthesia. 
2. Brief Description of the Prior Art 
When the spinal nerve of the human is to be anesthesized, an epidural 
catheter having an injection opening for the inflow of an anesthetic drug 
or solution only at the tip thereof has been heretofore employed. However, 
such an epidural catheter necessarily involves a disadvantage in that the 
anesthetic drug accumulates as an undesirably large droplet around the 
opening of the catheter, whereas the peripheral portion of a region to be 
anesthesized receives relatively little anesthetic drug as it is seen in 
FIG. 5(b), and as a result, anesthesia is non-uniformly achieved. This 
disadvantage becomes more serious particularly when regional anesthesia is 
desired to be effected over a wide region, it is then necessary that the 
droplet size of the anesthetic drug be made large, and a large amount of 
the anesthetic drug is thus required. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide a multi-lumen epidural catheter 
which eliminates the above-described disadvantage. the degree of 
anesthesia, if desired, with change of time. 
Another object of this invention is to provide a multi-lumen epidural 
catheter capable of controlling an anesthetic region and the degree of 
anesthesia, if desired, with change of time. 
In accordance with this invention, it has now been found that these objects 
can be accomplished by a multi-lumen epidural catheter which comprises at 
least one inner tube having a tip and a rear portion for forming a first 
path for an anesthetic solution, and an outer tube having a tip and a rear 
portion forming a second path for an anesthetic solution between the inner 
and outer tubes, wherein the inner tube has an opening at the tip thereof, 
the outer tube has at least one pair of side openings at portions 
appropriately spaced from the tip of the outer tube, and the inner tube is 
separated from the outer tube at the rear portions thereof so that 
openings for inflow of anesthetic solution into each of the tubes are 
provided at the rear portions of the inner and outer tubes, respectively.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Only for purposes of simplicity, a description is made with reference to a 
double-lumen epidural catheter. 
Referring to the figures, reference numeral 9 denotes an epidural catheter 
which comprises an inner tube 10 having a tip 12 and a rear portion (14) 
which is molded using flexible plastics and which forms a first path for 
an anesthetic solution, and an outer tube (11) having a tip 12' and a rear 
portion 14' which is made of flexible plastics and which forms a second 
path for an anesthetic solution between the inner tube 10 and the outer 
tube 11. The outer tube 11 possesses a diameter determined such that it 
can smoothly go through an epidural needle 1 to thereby make it easy to 
locate the catheter 9 in the epidural space 7, as shown in FIG. 4. 
As is seen from the above description, the size of the inner tube 10 
primarily depends upon the volume of an anesthetic solution required and 
the rate of injecting the anesthetic solution, and this in turn determines 
the size of the outer tube 11, and the size of the epidural needle 1. 
However, from a practical standpoint, there is a certain limit for the 
size of the epidural needle 1 since the pain caused by inserting the 
epidural needle 1 into the patient should preferably be minimized. Thus, 
the size of the epidural needle 1 is automatically fixed in a certain 
range, and generally between 15 and 18 gauge, preferably 17 gauge. This 
size range of an epidural needle conversely determines successively the 
size of the outer tube and then the inner tube. A 17 gauge needle has an 
outer diameter of about 1.47 mm and an inner diameter of about 1.17 mm. 
Considering that an anesthetic solution is generally injected at a rate of 
about 10 ml/min. (though the injection rate slightly varies depending upon 
personnel, condition of the patient, degree of anesthesia required, etc., 
the variation in the injection rate can easily be appreciated by one 
skilled in the art.), it is desired that the inner and outer tubes be of a 
size sufficient to provide an anesthetic solution at a rate of about 10 
ml/min. For example, it is desired that the size of the inner tube 10 be 
in a range of about 0.2 to about 0.6 mm, preferably 0.4 mm as an inner 
diameter, and in a range of about 0.4 to 0.8 mm, preferably 0.6 mm as an 
outer diameter; and the size of the outer tube 11 be in a range of about 
0.6 to about 1.0 mm, preferably 0.8 mm as an inner diameter thereof and in 
a range of about 0.8 to about 1.2 mm, preferably 1.0 mm as an outer 
diameter. The size relation among the inner tube, outer tube and epidural 
needle can afford an effective regional anesthesia contemplated in this 
invention. 
Reference numeral 12 denotes an opening at the tip 12 of the inner tube 10 
and reference numeral 13 denotes a pair of side openings having an 
appropriate spacing from the tip 12, e.g., approximately 5 cm distance. 
While the distance is somewhat varied, one can easily determines the 
distance from the tip 12 from which an anesthetic solution is spread, 
because the epidural catheter in accordance with this invention is applied 
to the human body and the organs are located in a limited area with a 
relatively fixed positional relation. 
Reference numeral 14 is the rear portion of the inner tube 10 separated 
from the outer tube 11 at the rear portion 14' of the outer tube 11 so 
that an opening 16' for the inflow of an anesthetic solution is connected 
to a device 16 at the rear portion 14 thereof. Reference numeral 17 is a 
device for providing an anesthetic solution therefrom which is connected 
to the opening 17' at the rear portion 14' of the outer tube 11. 
The inner and outer tubes are generally molded using flexible plastics such 
as polymers of tetrafluoroethylene (generic name: teflon). It is preferred 
that the flexible plastics be transparent since undesirable back current 
of blood which might occur during anesthesia using epidural catheters can 
easily be detected with the naked eye. 
While the structure of the epidural catheter of this invention is described 
with reference to a double-lumen type, it is not limited thereto but also 
includes a triple lumen epidural catheter. In this case, three different 
regions can be anesthesized simultaneously or separately. In a similar 
manner, a multi-lumen epidural catheter can also be employed for achieving 
anesthesia at controlled regions, simultaneously or separately, depending 
upon the number of lumens used. In determining the structure of the 
multi-lumen type, the same principle, considering a volume of an 
anesthetic solution required and an injection rate of the anesthetic 
solution, as used in the double-lumen type, also applies to the 
multi-lumen type. However, from a practical standpoint and demand for type 
of anesthesia, a double-lumen type is most preferred. 
The side openings 13 provided on the outer tube 11 form a droplet as shown 
in FIG. 5(a) which can afford severely controlled anesthesia at required 
regions and at the same time minimize the volume of the anesthetic 
solution required. It is preferred that each of the side openings 
possesses a diameter of about 0.4 to about 0.8 mm, preferably 0.6 mm which 
can ensure the required injection rate (about 10 ml/min) for an anesthetic 
solution. 
The double-lumen epidural catheter 9 having the structure described 
hereinabove is employed by injecting an anesthetic solution, 
simultaneously or separately, using a syringe (not shown) from the 
respective openings 16' and 17', while detaining the portion including the 
tip opening 12 and the side openings 13 in the epidural space 7 through 
the epidural needle 1. 
In more detail, as shown in FIG. 4, the epidural needle 1 is introduced 
slowly and gradually. The needle 1 which can make it easy to locate the 
catheter 9 in the epidural space 7 passes successively through the skin 2, 
subcutaneous tissue 3, interspinous ligament 5 and ligamentum flavum 6 to 
finally reach the epidural space 7. After epidural placement of the needle 
7 has been assured (at this time, a negative pressure is loaded, unlike a 
positive pressure loading when the needle 1 is being passed through from 
the skin to the ligamentum flavum, so that the epidural placement can be 
confirmed), the epidural catheter 9 is then introduced into the epidural 
space 7 through the needle 1. The epidural catheter is inserted about 5 cm 
into the epidural space. Thereafter, the needle 1 is withdrawn from the 
skin. An anesthetic drug or solution is injected from the openings 16' 
(which forms the first path) and 17' (which forms the second path), 
respectively. If desired, anesthesia can be achieved simultaneously or 
independently. When the anesthetic solution is to be filled between 
segments A and B as shown in FIG. 5(a), the injected anesthetic solution 
forms two round droplets around the two side openings 13 provided on the 
outer tube 11. Then, the anesthetic solution spreads more smoothly in the 
segments A and B. Accordingly, the double-lumen epidural catheter of this 
invention can greatly decrease the required volume of the anesthetic 
solution for filling the solution in the segments A and B. 
To the contrary, when using the prior art epidural catheter (having only 
one opening at the tip thereof), it is necessary to inject a large volume 
of an anesthetic solution since the anesthetic solution is supplied 
through only one opening at the tip thereof. Thus, the anesthetic solution 
undesirably accumulates very heavily around the opening at which the 
anesthetic solution is introduced and the peripheral portion of the 
anesthetic droplet is very thin, as shown in FIG. 5(b). Therefore, the 
region for anesthesia cannot be severly controlled with the prior art 
catheter and of course, there is a danger that the use of an anesthetic 
solution in a large volume, which is inevitable with the prior art 
catheter to obtain regional anesthesia, might be accompanied by side 
effects. 
The multi-lumen epidural catheter in accordance with this invention 
provides the following advantages. 
(1) The spread of an anesthetic drug is greater than with the prior art 
catheter. Thus, the dosage of an anesthetic drug can be decreased so that 
side effects of the anesthetic drug can be minimized. 
(2) During an operation, it is often necessary to expand the anesthetic 
region because the focus spreads over a wider area than expected prior to 
the operation. In such a case, it is possible to expand the anesthetic 
region by injecting an anesthetic drug from the proximal or distal 
openings of the catheter. 
(3) Continuous epidural anesthesia has been used for pain relief in 
childbirth labor. This is because labor is divided into three stages. A 
first stage lasts from the onset of the time at which the cervix attains 
full dilatation. A second stage lasts from the time of the full dilatation 
to the time at which the baby has been expelled. A third stage lasts from 
the time of delivery of the baby to the complete expulsion of the 
placenta. Pain at the first stage is primarily due to dilatation of the 
cervix. Pain at the second stage is produced by distension of the lower 
birth canal, vulva and perineum. Pain at the third stage is primarily due 
to the uterus contraction. During the first stage, block can be limited to 
the lower thoracic and upper lumbar segments, but during the second stage, 
the block should be extended to the sacral segments. If a perfect 
anesthesia is requested in labor, it was necessary to insert two epidural 
catheters into the epidural space, one catheter serving for the pain 
relief of the lower thoracic and the upper Clumbar segments and another 
catheter for the sacral segments. The use of two epidural catheters is 
very troublesome and the patient suffers a pain stimulus very seriously. 
The epidural catheter in accordance with this invention possesses at least 
two openings for the inflow of an anesthetic solution. When the epidural 
catheter of this invention is used for the pain relief of labor, it is 
possible to obtain pain relief using only one opening for the inflow of an 
anesthetic solution during all the stages of labor. Anesthesia in the 
lower thoracic and upper lumbar regions is obtained by injecting an 
anesthetic solution from the proximal opening. At the second and third 
stages of labor, anesthesia in the vulva and perineum are obtained by 
injecting an anesthetic solution from the distal opening. 
(4) In epidural anesthesia, the insertion of an epidural catheter is 
performed blindly. Accordingly, the tip of the inner tube sometimes tends 
to go astray into the intervertebral space (not shown) out of the epidural 
space 7. In this case, no anesthetic effect is obtained even though an 
anesthetic solution is injected. 
In case of using the epidural catheter of this invention, there is no 
problem even if the tip opening (12) goes stray in the intervertebral 
space since the side openings (13) can remain in the epidural space and in 
this case, an anesthetic solution can be injected through the side 
openings (13) to effect anesthesia contemplated. 
In FIG. 4, reference numerals other than referred to hereinabove are used 
to mean the following: 
30: interspinous cartilage 
40: spinal chord 
50: arachnoid 
60: dura 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.