Slotted regional anesthesia needle

A hypodermic needle device for administration of anesthesia to a patient's epidural space comprising a hypodermic needle having a barrel portion with opposed distal and proximal ends, a hub assembly located at the proximal end of the barrel portion of the needle, through which instruments such as a rigid stylet, or a flexible catheter having a pre-affixed connector, may be introduced into the needle, and a slot formed axially along the length of the needle from the distal end through the hub at the proximal end of the needle. The slot has a minimum width dimension not greater than the outer diameter of a stylet or epidural catheter such that during location of the epidural space, and placement of a catheter in the epidural space, the stylet and catheter will not come out of the needle, yet the needle may be easily removed from the catheter once the catheter is in place, by pulling the catheter through the slot in the needle.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention most generally relates to anesthesia needles used to 
administer regional anesthesia to a patient. More particularly the 
invention relates to a regional anesthesia needle used to apply anesthesia 
to the epidural space of a patient. Most particularly the invention 
relates to an epidural anesthesia needle having a slot running the length 
of the needle from the distal end through a hub at the proximal end. The 
slot allows the use of a catheter with a permanently pre-affixed connector 
at its proximal end for administration of anesthesia to a patient. The 
slot is formed with a dimension that is smaller than the outer diameter of 
a stylet and catheter. The smaller diameter prevents the stylet and 
catheter from inadvertently coming out of the needle during the procedure. 
Once the catheter is in place in the epidural space of a patient and 
secured, the needle is withdrawn and can be removed by pulling the 
flexible catheter out of the slot in the needle, thus allowing the use of 
a catheter with a permanently pre-affixed connector at its proximal end. 
2. Description of the Prior Art 
Regional anesthesia is performed to bring about anesthesia in a specific 
region of the body. The patient remains conscious of his surroundings and 
may retain complete mobility of the area anesthetized. When successfully 
performed, regional anesthesia provides complete analgesia in the specific 
area to which it was directed and requires only a small amount of local 
anesthetic. The regional anesthesia relevant to the present invention 
relates specifically to spinal anesthesia delivered to the epidural space, 
as related to the cervical, thoracic, lumbar, or caudal regions of the 
spine, but more specifically to the regional anesthesia performed in the 
lumbar or thoracic regions. 
There are many preparative steps before administration of the anesthesia. 
The general technique of administering epidural anesthesia involves 
injecting a local anesthetic solution into the epidural space, from which 
it defuses to the immediate vertebral spaces around the injection site and 
around the outer layers of the spinal cord, surrounding spinal nerves, 
producing anesthesia. The technique is most commonly performed at the 
lumbar level of the spine and is applicable in the diagnosis and treatment 
of chronic pain, for example in cancer patients, as well as providing 
surgical and obstetric anesthesia. 
The epidural space extends from the base of the skull to the tip of the 
caudal vertebrae, and lies between the dura which surrounds the spinal 
cord and the ligaments which join the vertebrae. The epidural space is not 
considered a true space, because unless separated, it is practically 
invisible. 
Before administering the anesthesia to the epidural space, the space must 
first be located, and care taken not to penetrate to the spinal cord. 
There are two different techniques which can be used to determine when the 
tip of the needle has entered the epidural space; the "hanging drop", and 
"loss of resistance" techniques. An epidural needle is first inserted 
until a marked resistance is felt, indicating entry into the interspinous 
ligament, and up to but not through, the ligamentum flavum. At this point, 
in the "loss of resistance" technique, the epidural needle is advanced 
into the ligamentum flavum, and the stylet is removed. A syringe with an 
easily moving plunger is filled with air or normal saline and attached to 
the needle. When the needle tip is in the ligamentum flavum, air or saline 
can not be ejected from the syringe when pressure is applied to the 
plunger. Constant pressure is exerted on the plunger by one hand as the 
needle is slowly advanced. When the tip of the needle enters the epidural 
space, there is a sudden release of air or saline into the epidural space, 
thus the loss of resistance. Once the epidural space is located, the 
syringe is removed and a catheter is placed onto the needle hub, and then 
inserted through the epidural needle, between about 2 cm to about 4 cm 
past the end of the needle, into the epidural space. When the catheter is 
in place, the needle is then withdrawn over the catheter taking care not 
to move the catheter. Once the catheter is advanced past the tip of the 
needle the catheter cannot be withdrawn because it might be sheared by the 
sharp tip of the needle. If readjustment is needed, both needle and 
catheter must be removed together. An epidural catheter connector is then 
attached to the catheter to allow syringe attachment for administration of 
anesthesia through the catheter. The catheter is then taped in place on 
the patient's back. 
With the above procedure in which the needle is removed by being slid over 
the catheter, the catheter can not have a connector "built in" or 
preaffixed to its proximal end because the needle would not fit over the 
connector. The typical connector is placed on the catheter after the 
needle is removed. The connector is comprised of three parts, two that are 
threaded together sandwiching the third part, an elastomeric tube. The 
catheter is slid into the connector going through the elastomeric tube. 
When the two threaded parts are tightened together the elastomeric tube is 
compressed, so its inside diameter (ID) squeezes the catheter outside 
diameter (OD). The problems with attaching a connector to the catheter at 
the time of treatment are that the connector can be over-tightened, 
crushing the catheter or it can be under-tightened creating a leak path or 
leading to the connector falling off the catheter potentially exposing the 
patient to extrinsic contamination. The procedure is cumbersome and the 
person performing the treatment may drop the connector during 
installation. A solution would be to have a catheter with a connector 
permanently or preaffixed to its proximal end by the manufacturer or at 
least prior to insertion of the catheter into the needle. However, the 
typical needle cannot be removed over a permanently or preaffixed 
connector. 
One solution was advanced by Mohiuddin in U.S. Pat. Nos. 5,322,512 (the 
'512 patent) and 5,425,717 (the '717 patent). Mohiuddin's solution was to 
have a needle which was splittable and could break away from the catheter. 
The needle is removed from the catheter by breaking the needle in half 
along its length. Both the '512 and the '717 patents address this issue. 
The '512 patent deals with protecting the splittable needle, and the 
second includes with the splittable needle a catheter with a fixed 
connector. This needle can be used with a catheter having a permanently 
affixed connector, but presents its own problems. These problems include; 
the needle not splitting all the way, preventing its removal from the 
catheter as intended, and the needle splitting prematurely while still in 
the patient during placement, preventing catheter placement until the 
split needle is removed and another needle placed. The present invention 
solves the problems of the prior art by providing an epidural anesthesia 
needle which may be more efficiently and safely used with a catheter 
having a permanently affixed connector. 
SUMMARY OF THE INVENTION 
A slotted hypodermic regional epidural anesthesia needle having a barrel 
portion with opposing distal and proximal ends and a hub at the proximal 
end, having a slot formed axially in the barrel portion running from the 
distal end all the way through the hub at the proximal end of the needle. 
The slot has a minimum width dimension that is smaller than the outer 
diameter of a typical stylet and catheter used in such a procedure. The 
smaller diameter of the slot prevents the stylet and catheter from 
inadvertently coming out of the slot in the needle during placement of the 
catheter. In order to allow the use of the "loss of resistance" technique 
for location of the epidural space, and use of a syringe without removing 
the stylet from the needle, the stylet used with the present invention has 
a female luer fitment on its proximal end for connection to a syringe and 
is constructed of hypodermic cannula. 
The slotted hypodermic regional epidural anesthesia needle is placed in the 
same manner as current anesthesia needles, with the exception of not 
having to remove the stylet to perform the "loss of resistance" technique 
because the stylet is hollow. Once the tip of the needle is in the 
epidural space, the stylet is removed and the epidural catheter, with a 
connector and cap affixed, is passed through the needle and positioned in 
the epidural space. The slotted hypodermic regional anesthesia needle is 
then pulled out of the patient and slid to the proximal end of the 
catheter. The catheter is secured to the patient to prevent it from 
moving. The needle is then removed by pulling the catheter out through the 
slot in the needle starting at one end of the needle and working toward 
the opposite end. 
Objects and advantages of the invention are: 1.) Elimination of catheter 
crushing from over tightening connectors; 2.) Elimination of catheter 
leakage from under tightening of connector; 3.) Elimination of inadvertent 
disconnection of connector; 4.) Reduced potential for contamination and 
infection; 5.) Reduced number of procedural steps; 6.) Allowance of use of 
catheter a with pre-affixed connector; 7.) No splitting of the needle is 
required; 8.) The slot is not subject to malfunction resulting in not 
being able to remove the needle from the catheter; 9.) The slot is not 
subject to premature malfunction (splitting) during needle placement; and 
10.) Use of a cannulated stylet allows the "loss of resistance" technique 
to be performed without removing the stylet, resulting in less procedural 
steps. 
A primary object of the invention is to provide a slotted hypodermic 
regional anesthesia needle that can be used with a catheter having a 
pre-affixed connector, may be easily removed from the catheter, and does 
not have to be broken or split in order to be removed from the catheter. 
Yet another primary object of the invention is to provide a slotted 
hypodermic regional anesthesia needle through which a stylet and catheter 
may be placed without concern that the stylet or catheter will 
inadvertently come out of the catheter prematurely during placement into 
the patient. 
A particular object of the present invention is to provide a slotted 
hypodermic regional anesthesia needle for use with a catheter having a 
pre-affixed connector such that the problems associated with manually 
attaching a connector, such as over or under tightening of the connector, 
inadvertent disconnection of the connector, and greater potential for 
contamination and infection due to handling of more components, are 
eliminated. 
A further particular element of the present invention is to provide a 
slotted hypodermic regional anesthesia needle which reduces the number of 
procedural steps required to place a catheter in the epidural space of a 
patient in order to administer anesthesia. 
These and further objects of the present invention will become apparent to 
those skilled in the art to which this invention pertains and after a 
study of the present disclosure of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following is a description of the preferred embodiment of the 
invention. It is clear that there may be variations in the size and the 
shape of the device and in the materials used in the construction and in 
the orientation of the various components which make up the anethesia 
needle device. 
Reference is now made to FIG. 1 which shows the slotted hypodermic regional 
anesthesia needle 2 of the present invention. Needle 2 is similar in 
diameter, material and length to the type typically used for 
administration of epidural anesthesia. I.e., the typical needle is 17 
gauge and 31/2 inches long. Needle 2 contains a barrel portion 10, distal 
end 14 which is inserted into the patient, proximal end 16 which remains 
outside the patient. There is a hub 18 at the proximal end 16 of barrel 
portion 10, and a slot 12 running axially along the length of barrel 
portion 10, through hub 18 resulting in slotted hypodermic regional 
anesthesia needle 2. 
FIGS. 2-6 illustrate, by sketch, particular embodiments and features of the 
present invention. FIG. 2 is a cross section of barrel portion 10 of 
needle 2 showing inner and outer walls 10a and 10b of barrel portion 10, 
and slot 12 with an instrument 40 having an outer diameter 40a, such as a 
stylet 20 having an outer diameter 20a as shown in FIG. 3 or a catheter 30 
having an outer diameter 30a as shown in FIG. 5, inserted in barrel 
portion 10 of needle 2. Epidural catheter 30 is typically a 19 gauge tube 
made of nylon, polyurethane, or fluorinated ethylene propylene (FEP). Slot 
12 has opposing walls 12a and the distance between walls 12a must be 
smaller in width than the outer diameter of either a typical solid or 
cannulated stylet or typical flexible epidural catheter at at least one 
area along slot 12, such that stylet 20 or catheter 30 can not simply 
"pop" out of needle 2 through slot 12. 
FIGS. 2a-2d show cross sections of various configurations and dimensions of 
slot 12. Although some portion of slot 12 must be smaller in width than 
the outer diameter of either a stylet or catheter to prevent the stylet or 
catheter from dislodging, slot 12 may vary in width along the length of 
barrel portion 10 as long as catheter 30 will not dislodge yet is 
removable through slot 12. Slot 12 could be cut such that walls 12a are 
parallel, or non-parallel as shown in FIGS. 2a and 2b. Walls 12a may be 
radiused or rounded where they meet inner and outer walls 10a and 10b of 
barrel portion 10 of needle 2 and hub 18 as shown in FIGS. 2c and 2d. 
FIG. 3 illustrates the particular type of stylet 20 to be used with the 
present invention. Stylet 20 is cannulated, hollow, and helps keep needle 
2 rigid and clear of debris. Stylet 20 has a distal end 22 and a proximal 
end 24 to which is attached a female luer fitment 26, such that a syringe 
(not shown) may be attached to the luer for performance of the "loss of 
resistance" technique to locate the epidural space of a patient. 
FIG. 4 shows stylet 20 partially in place in slotted regional anesthesia 
needle 2. FIG. 5 illustrates needle 2 with an epidural catheter 30 in 
place in needle 2. Catheter 30 passes through hub 18 into slot 12 in 
needle 2. Catheter 30 has a distal end 32 which extends from about 2 cm to 
about 4 cm past the distal end of the tip of needle 2 when fully inserted, 
and a proximal end 34 at which is attached a pre-affixed connector 36 to 
place catheter 30 in fluid communication with a source of liquid 
anesthesia for administering to the patient. There is a cap 38 which fits 
connector 36 to close connector 36 and protect against contamination when 
anesthesia is not being administered. 
FIG. 6 shows the process of removing needle 2 from catheter 30 once 
catheter 30 is in place in the epidural space in the patient and needle 2 
has been withdrawn. Catheter 30 may be pulled from needle 2 by pulling 
flexible catheter 30 through slot 12 which runs the entire length of 
needle 2, including running through hub 18. In this way, once catheter 30 
is in place in the epidural space, needle 2 may be withdrawn from the 
patient, secured to the patient, and needle 2 removed in one piece, 
leaving the catheter 30 with its pre-affixed connector 36 ready to receive 
anesthesia. 
With the present invention, the step of removing stylet 20 in order to 
perform the "loss of resistance" technique to locate the epidural space is 
eliminated. More importantly, the step of manually attaching a connector 
to proximal end 34 of catheter 30 after insertion of catheter 30 and 
removal of needle 2 is eliminated. Needle 2 is easily removed leaving 
catheter 30 with pre-affixed connector 36 in place. 
It is thought that the present slotted regional anesthesia needle, for use 
in the administration of anesthesia to the epidural space of a patient and 
many of its attendant advantages is understood from the foregoing 
description and it will be apparent that various changes may be made in 
the form, construction and arrangement of the parts thereof without 
departing from the spirit and scope of the invention or sacrificing all of 
its material advantages, the form herein before described being merely a 
preferred or exemplary embodiment thereof.