Splittable needle for epidural anesthesia

Disclosed is a splittable needle device adapted for use in administering epidural anesthesia. The needle has guide means to facilitate insertion of the needle into the peridural space, contained on a splittable hub assembly.

Prior surgical procedures for administering epidural anesthesia utilize an 
epidural catheter having a free proximal end. Following introducing the 
catheter within the needle and then into the body, the needle is withdrawn 
from the body and slid over the free proximal end of the catheter. The 
proximal end of the catheter is then secured to a catheter connector or 
adapter for placement in fluid communication with a source of the liquid 
anesthesia for administering to the patient. 
To guard against overtightening of the catheter connector, causing damage 
to the catheter and/or its function, or undertightening or accidental 
loosening whereby the catheter slips out of the connector, as well as the 
problem which sometimes occurs of accidentally dropping the connector 
while attempting to secure it to the catheter, it would be desirable to 
employ an epidural catheter pre-connected at its proximal end to an 
adapter. 
However, if this is done, it will be appreciated that it would no longer be 
possible to slide the needle over the proximal end of the catheter which 
has been introduced through the needle into the body. 
A particularly efficacious way of solving this dilemma is to employ a 
so-called splittable needle, which needle is per se old in the art for 
other medical procedures and is disclosed, for example, in U.S. Pat. Nos. 
4,377,165 of Luther et al and 4,449,973 of Luther, both assigned to Luther 
Medical Products, Inc. 
Stated simply, the task of this invention is to design a splittable needle 
device which has guide means facilitating the delicate task of inserting 
the needle within the peridural space without penetrating the arachnoid 
membrane, which needle assembly is readily splittable away from the 
catheter therewithin. 
BRIEF DESCRIPTION OF THE INVENTION 
In accordance with this invention, the task is solved in an elegant manner 
by providing a splittable needle having a splittable hub assembly 
including a guide member which can be gripped by the anesthesiologist to 
gently guide the needle into the desired position, the needle and the hub 
assembly thereafter being readily separable from the catheter in a single 
manipulative step.

DETAILED DESCRIPTION OF THE INVENTION 
As previously mentioned, the present invention is directed to a so-called 
split or break-away needle for use in administering epidural anesthesia, 
the needle being characterized by having means facilitating insertion of 
the needle into the peridural space. 
The invention will best be understood by reference to the accompanying 
illustrative drawings taken in conjunction with the following detailed 
description. 
As shown in the drawings, the needle 10 has a distal or leading end 12 and 
a proximal or trailing end 14 at which a unitary hub assembly 16 is 
provided. Intermediate the distal and proximal ends 18, 20, respectively 
of the hub assembly a pair of opposed wings 22, 24, are provided for 
splitting the needle away from the catheter, as will be described 
hereinafter. As best seen in FIGS. 2 and 3, the hub assembly 16 has a pair 
of slits 26a, 26b extending between the distal and trailing end 18, 20 of 
the assembly, the slits being essentially parallel and being situated 
radially approximately 180.degree. apart. 
A guide bar 27 is provided above wings 22, 24 to facilitate inserting the 
needle without touching wings 22 and/or 24 which could cause inadvertent 
premature splitting of the needle 10 and separation from the catheter 
within the needle. 
In a preferred form, the guide bar 27 comprises substantially equal 
sections 28, 30 separated at least at their upper surface by slit 32. As 
shown in the drawings, slit 32 extends substantially through guide bar 27 
to the base or bottom members of guide bar sections 28, 30 which in the 
unitary hub assembly will be adhered to wings 22, 24, respectively. 
The proximal end 20 of the hub assembly 16 will be provided with a 
conventional luer fitting 34 for receiving a syringe. 
While not an essential component of the invention, to facilitate insertion 
of the needle, a stylet 36 having a cap 38 of per se known structure and 
configuration is preferably employed. The stylet will be of a length such 
that when inserted into the needle, the leading end (not shown) of the 
stylet will extend to the distal tip of the needle while the cap 38 abuts 
the rear of luer fitting 34. 
The splittable needle employed in the practice of this invention may be of 
the type described and claimed in the aforementioned U.S. Pat. No. 
4,377,165 of the Luther et al. 
As is described therein, a needle blank is continuously formed from flat 
sheet metal such as sections or from a roll. A groove of controlled depth 
is formed along the blank stock which is then rolled to a hollow 
configuration and then cut into individual needle barrels with a 
longitudinal slit along each needle barrel. The groove is oriented 
parallel to the slit and along the opposite side of the barrel. Finally, 
the wings are welded to the barrel on each side of the slit. The groove 
depth is sufficiently shallow to ensure adequate stiffness during use 
while being deep enough so that the needle will split easily when the 
wings are flexed, thereby separating the needle from the catheter. 
As further described in the patent, excellent stiffness, splitting and 
rolling properties are obtained with a sheet thickness of about 2-4 mils, 
a needle length of about 3/4"-2", about 12-20 gauge barrel diameter, and a 
controlled groove depth about 50%.+-.10% of the sheet thickness using a 
304-316 stainless steel or equivalent. 
The sheet stock may be in flat form such as in sections, say, 1/2-10 feet 
long, but is usually loaded on a roll. The open needle portion constitutes 
only about 7%-15% of the total barrel length, and this considerably 
improves the working strength of the needle. Thus, the needle of this 
invention can employ a relatively deep groove without losing structural 
integrity during use. 
While the needles contemplated by this invention may be made in the same 
manner, it is pointed out that epidural needles are longer than the 3/4 
inch to 2 inches recited in the patent. Specifically, the epidural needles 
of this invention will typically be about 3.5 inches in length. 
The structure of the needle barrel and how splitting is effected may best 
be understood by reference to FIGS. 6 and 7 of the application which 
correspond essentially to FIGS. 3 and 4 respectively of U.S. Pat. No. 
4,377,165. 
As shown therein, the needle has a longitudinal slit 42 extending the 
entire length of the needle barrel between its ends 12, 14. The slit is 
formed when the blank is rolled to produce the barrel and may typically, 
for example be as great as 1 mil wide. 
Groove 44 is formed on the inner wall 10a of the needle barrel also 
extending longitudinally from one end to the other. As shown, groove 44 is 
situated about 180.degree. radially from slit 42 and is parallel thereto. 
The procedure for introducing the needle into the peridural space for 
administering epidural anesthesia will now be described. 
To administer epidural anesthesia, great care must be taken in inserting 
the needle to be sure it is positioned in the peridural space between the 
ligamentum flavum and the arachnoid membrane. As is well understood, if 
the needle penetrates too far, it will penetrate into the subarachnoid 
space, causing spinal fluid to leak out. For this reason, the needle may 
be calibrated to assist the anesthesiologist in determining the degree of 
insertion into the body. 
In a typical procedure, the patient, having been prepped for surgery, is 
brought into an induction room adjacent the operating room where the 
anesthesiologist is to insert the catheter in preparation for the surgery. 
A local injection is first given to minimize pain and discomfort from 
introducing the needle. With the stylet in the needle, the needle is 
slowly and carefully inserted until it abuts the ligamentum flavum, at 
which time the skilled hands of the anesthesiologist senses a resistance 
to further insertion. At this time, the stylet is removed from within the 
needle and a "loss of resistance" syringe is inserted within the luer 
fitting. By slowly advancing the needle and syringe, the ligamentum flavum 
is penetrated and the needle tip is advanced into a vacuum area (the 
peridural space) where there is no resistance. 
At this point, the syringe is withdrawn and the catheter inserted within 
the needle and then into the peridural space. 
With the conventional needle procedures, the catheter is secured in place, 
as with adhesive tape, and the needle is withdrawn over the catheter. When 
the needle is removed, the proximal end of the catheter may be secured 
within the distal end of a catheter adapter or connector having a luer 
fitting at its proximal end to put a syringe filled with liquid anesthesia 
in fluid communication with the catheter secured to the distal end of the 
connector. As an example of such an adapter, mention may be made of the 
adapter described and claimed in U.S. Pat. No. 5,053,015 assigned of 
Gross, to The Kendall Company, assignee of the present invention and 
commercially available under the trademark Safe Trak. 
As distinguished from this conventional system, the present invention 
contemplates the use of an epidural catheter which is preconnected to the 
adapter at its proximal end, thereby obviating the need to perform the 
connection in the surgical procedure along with the inherent dangers of 
dropping the connector so that a new one is required, overtightening the 
connection to impair the catheter function and/or undertightening so that 
the catheter accidentally is removed or drops from the connector. 
While a preconnected epidural catheter accordingly has obvious inherent 
advantages, it will of course be appreciated that in view of the 
preconnection, it is not possible to slide the needle over the proximal 
(trailing) end of such a catheter. 
This problem is then solved by employing the splittable needle to which 
this invention is directed. 
While splittable needles are per se known for other medical procedures, it 
was never heretofore been suggested for use in epidural anesthesia to the 
best of Applicant's knowledge. 
With reference against to FIGS. 6 and 7, in the prior medical procedures, 
the needle will be gripped along its barrel or gently by the wings and 
inserted beneath the skin to the desired placement. After placement, the 
wings 22, 24 may be flexed in the direction shown by the arrows in FIG. 7, 
causing the needle to open up along the longitudinal slit 42, thereby 
causing splitting or cracking along the longitudinal groove 44 which in 
turn causes the needle halves following splitting to separate from the 
catheter 40 within the needle. 
For use for epidural anesthesia has contemplated by this invention, it is 
essential that the split needle device have guide means, e.g. the 
illustrated guide bar 27 for gripping or pushing against (as desired by 
the anesthesiologist) during the delicate procedure of slowly and 
carefully introducing the needle into the peridural space. 
As seen, the split needle device of this invention also utilizes a 
one-piece splittable hub assembly 16 wherein the wings, guide bar and 
other components of the assembly all split away from the catheter along 
with the needle upon flexing the wings 22, 24, the splitting of the hub 
assembly being assured by slits 26a and 26b. 
From the foregoing description it will be appreciated that the present 
invention provides an elegant design for a splittable needle for use in 
epidural anesthesia. 
The guide bar 27 is versatile and ergonomic in design in that it caters to 
the particular style or whim of the user in gripping to guide the needle 
into the peridural space. Whatever the user's preference, a secure grip is 
provided. 
The longitudinal slits 26a,b ensure splitting of the hub assembly along 
with the needle barrel for a clean separation of the catheter. 
It will be appreciated that various changes may be made without departing 
from the scope of the invention herein contemplated. 
For example, other splittable needle constructions may be readily suggested 
to those skilled in the art in the light of the foregoing description as 
will other designs for the guide means and/or the wing configuration for 
causing splitting of the needle. 
Accordingly, all matter contained in the foregoing descriptions and shown 
in the accompanying drawings shall be interpreted as being illustrative 
and not in a limiting sense.