Patent Publication Number: US-5425717-A

Title: Epidural catheter system utilizing splittable needle

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of Applicant&#39;s earlier application, Ser. No. 08/076,921 filed May 7, 1993, and now U.S. Pat. No. 5,322,512. 
    
    
     BACKGROUND OF THE INVENTION 
     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 Following introducing the catheter within the needle and then into the body, the needle is withdrawn from the body and slid over the free proximal end of the catheter.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 through which the catheter is introduced over the proximal end of the catheter following introduction into the peridural space for administration of the epidural anesthesia. 
     Stated simply, the task of this invention is to provide an efficient and cost-effective system for administering epidural anesthesia utilizing an epidural catheter permanently secured at its proximal end to a connector or adapter for placing the catheter in fluid communication with a source of liquid anesthesia. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with this invention the task is solved in an elegant manner by providing a system for administering epidural anesthesia utilizing an epidural catheter permanently secured at its proximal end to an adapter for placing the catheter in fluid communication with a source of liquid anesthesia in combination with a splittable needle to be described in detail hereinafter and which can be readily split apart for separation from the catheter following introduction of the catheter through the needle into the peridural space. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the novel system for administering epidural anesthesia of this invention; 
     FIG. 2 is a perspective view of a split needle useful in the practice of this invention; 
     FIG. 3 is a perspective view partially broken away showing the epidural catheter secured to an adapter at its proximal end; 
     FIG. 4 is a top plan view of the device of FIG. 1; 
     FIG. 5 is a bottom plan view of the device of FIG. 1; 
     FIG. 6 is a front elevational view taken from the distal (leading) end of the device of FIG. 1; 
     FIG. 7 is a rear elevational view taken from the proximal (trailing) end of the device of FIG. 1; 
     FIG. 8 is an enlarged cross section view taken along lines 8--8 in FIG. 4; and 
     FIG. 9 is a cross section view similar to FIG. 8 showing the effect of flexing the wings to split the needle and thereby to separate the needle from the catheter within the needle. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As heretofore mentioned, the present invention utilizes a splittable needle for use with an epidural catheter adhered permanently at its proximal end to an adapter so that the needle cannot be slid over the proximal end for removal from the catheter. 
     Splittable needles are per se old in the art for other medical procedures, as 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. 
     The present invention utilizes a splittable needle such as is known in the art, the needle preferably having a hub assembly characterized by having means facilitating insertion of the needle into the peridural space without endangering premature unwanted splitting of the needle during insertion. 
     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 has a distal or leading end 12 and a proximal or trailing end 14 at which a unitary hub assembly 16 is provided. The hub assembly is preferably sufficiently transparent to permit visualization of any CSF fluid indicating the needle has entered the subarachnoid area or blood indicating it has entered a vein. 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. 4 and 5, 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° apart. As is known for administering epidural anesthesia, needle 10 will typically be 17-18 gauge. 
     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, as shown in FIG. 2, 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&#34;-2&#34;, about a 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, and as mentioned previously, will typically be on the order of 17-18 gauge. 
     The structure of the needle barrel and how splitting is effected may best be understood by reference to FIGS. 8 and 9 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 of the needle barrel also extending longitudinally from one end to the other. As shown, groove 44 is situated about 180° radially from slit 42 and is parallel thereto. 
     As heretofore mentioned, a splittable needle such as described above and shown in the illustrative drawing is necessitated because it is to be employed in combination with an epidural catheter permanently secured at its proximal end to an adapter for placement in fluid communication with a source of liquid anesthesia. 
     With reference in particular to FIGS. 1 and 3, a catheter 50 having distal and proximal end 52,54 is permanently adhered at its proximal end 54, e.g. by insert molding, to the distal end 59 of an adapter 56. Catheter 50 will typically be a 20 or 21 gauge catheter for insertion within needle 10. 
     Adapter 56 may be of generally known configuration, having a hollow bore 58 extending from its distal end 59 where the catheter 50 is affixed to its proximal end 60 which has a syringe port 62 for retaining a syringe (not shown) or other source of liquid anesthesia. While not essential, adapter 56 is preferably provided with a finger grip flange 64 having holes 66 for securing the adapter to a bedsheet or other item and a cap 68 fittable within syringe port 62, the cap 68 being secured to the adapter by linkage 70 and retaining ring 72. 
     The procedure for administering epidural anesthesia in accordance with this invention 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 &#34;loss of resistance&#34; 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, assigned to The Kendall Company, assignee of the present invention and commercially available under the trademark SafeTrak. 
     As distinguished from this conventional system, the present invention utilizes an epidural catheter which is preconnected to the adapter at its proximal end as heretofore discussed, 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, thus presenting the further inherent danger of contamination. 
     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 catheter, thereby requiring a splittable needle for separation from the catheter following introduction through the needle into the peridural space. 
     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&#39;s knowledge. 
     With reference against to FIGS. 8 and 9, 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. 9, 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 50 within the needle. 
     For use for epidural anesthesia as 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. Additionally, the guide bar permits the user to get a better tactile sense of the needle by allowing it to be gripped closer to the cannula. 
     As seen, the split needle device 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. 
     The splittable needle described above and shown in the illustrative drawings provides an exceptionally efficacious design 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&#39;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. 
     From the foregoing description it will thus be seen that the present invention solves the stated task of the invention in an elegant manner. 
     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. 
     In like manner, various changes in the adapter to which the epidural catheter is connected may be readily suggested to those skilled in the art. 
     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.