CA1326194C - Method and system for inserting spinal catheters - Google Patents

Abstract

ABSTRACT

A method and a system for inserting spinal catheters for administration of spinal anaesthesia are disclosed. An epidural needle having a hub is inserted into the epidural space of a patient and a cannula having a blunt end is inserted into and advanced forwardly within the epidural needle for abutment against the dura-arachnoid membrane to place the membrane in tension. The cannula is locked in place in the epidural needle by a securing means attached to the hub of the epidural needle. A
flexible catheter having a wire or stylet therein with an end projecting beyond the distal end of the catheter is inserted through the cannula for piercing a hole in the tensioned dura-arachnoid membrane whereby the catheter can be inserted a predetermined distance through the dura-arachnoid membrane into the subarachnoid space. The cannula and epidural needle are removed and the wire withdrawn to allow continuous administering of an anaesthetic through the catheter. A hole can be formed in the dura-arachnoid membrane by a sharp stylet prior to insertion of the catheter.

Description

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BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to the field of catheters and, more particularly, relates to a method and to a system for inserting catheters for administering spinal anaesthesia.
2. Descri~tion of the Prior Art Catheter placement devices and related methods involve puncturing of a membrane or like tissue by means of a hollow needle within which a catheter is introduced to the desired location, and the needle and related accessories removed leaving the catheter in place. The hole formed in the tissue by the needle usually is larger than the diameter of the catheter allowing fluids to leak from one side of the membrane to the other to cause severe discomfort to the patient. U.S. Patent No.
4,417,886 issued November 29, 1983 discloses a catheter introduction set for introducing a catheter into a small diameter blood vessel consisting of a catheter mounted on a hollow needle having a spring wire guide therein. In use, the hollow needle is first inserted into the blood vessel, the spring wire guide is advanced into the blood vessel as far as possible and the catheter then advanced on the spring wire guide into the blood vessel. The spring wire guide and needle are removed leaving the catheter in the blood vessel.

U.S. Patent No. 4,655,750 issued April 7, 1987 discloses another embodiment of catheter system for placement of a flexible catheter into the lumen of an artery or vein which includes a guide wire adapted to be advanced into the lumen and a catheter advanced along the guide wire until placement is a~hieved.
U.S. Patent No. 4,529,399 issued July 16, 1985 discloses a method and apparatus for placing a catheter in which a hole is made in a vessel wall by a needle outside a catheter and the catheter advanced on a stylet.
Epidural and spinal anaesthesia require the administration of an anaesthetic agent into the epidural or subarachnoid spaces respectively of the spine.
- Epidural anaesthesia requires substantially more anaesthetic agent than spinal anaesthesia and, if the anaesthetist inadvertently penetrates the dura-arachnoid membrane while endeavouring to administer an anaesthetic agent to the epidural space, a dangerous quantity of anaesthetic agent can be placed in the subarchnoid space, possibly causing paralysis or even death.
U.S. Patent No. 4,518,383 issued May 21, 1985 teaches an instrument for epidural and spinal anaesthesia - in which an outer hollow TuohyT~ needle has a bent pointed tip to locate the epidural space and an inner hollow needle with a pointed tip projecting forwardly of ~3æ6~94 the outer TuohyT~ needle in alignment therewith to penetrate the dura with a minimum of cutting of tissue.
U.s. Patent No. 4,737,146 issued April 12, 1988 discloses another version of epidural catheter in which a rigid epidural needle is inserted into an epidural space and an epidural catheter is introduced through the needle into the epidural space through a lateral opening in the tip of the needle.
It is an object of the present invention to provide a method and system for inserting a spinal catheter to ensure CQrreCt placement of the catheter in the subarachnoid space and to obviate leakage of cerebro-spinal fluid from the subarachnoid space into the epidural space of the spine during and after administration of continuous spinal anaesthesia.
BRIEF SUMMARY OF THB INV~N~O~
-; In accordance with one aspect of the catheter ~, system of the invention, for the insertion of a flexible catheter through the epidural space and dura-arachnoid membr~ne into the subarachnoid space of a spine, the syste~ comprises a hollow needle having a sharpened entry end for insertion into the epidural space and an exit end having a hub, a cannula with a blunt distal end adapted for placement into and axial movement within the hollow needle whereby said cannula can be advanced forwardly within the hollow needle for abutment of the blunt distal 5 ~32~94 end against the dura-arachnoid membrane to place tension on the dura-arachnoid membrane, securinq means adapted to be attached to the hub at the exit end of the hollow needle for locking the cannula within the hollow needle from axial movement, and a flexible catheter having a wire therein for insertion through the cannula and penetrating the dura-arachnoid membrane forming a hole, whereby the distal end of the catheter can be inserted a predetermined distance into the subarachnoid space through said hole, the cannula and the hollow needle retracted along the catheter, the securing means removed, and the wire withdrawn from the catheter.
In accordance with an aspect of the method of the invention for passing a catheter through the epidural space and dura-arachnoid membrane into the subarachnoid space of a patient's spine, the method comprises the steps of inserting a hollow needle having a sharpened entry end into the epidural space, said hollow needle having an exit end with a hub, inserting a cannula with a blunt distal end into the hollow needle and advancing the cannula forward for abutment of the blunt distal end of the cannula against the dura-arachnoid membrane to place the dura-arachnoid membrane in tension, locking the 6 ~32~9~
cannula from coaxial movement in the needle, inserting a flexible catheter having a wire therein through the cannula and penetrating the tensioned dura-arachnoid membrane through a hole therein whereby the distal end of the catheter can be fed a predetermined distance into the subarachnoid space through the hole formed in the dura-arachnoid membrane, and retracting the hollow needle and cannula along the catheter and withdrawing the wire while the distal end of the catheter remains inserted in the said subarachnoid space.
In accordance with another aspect of the present invention, the dura-arachnoid can be pierced with a sharp stylet to form a hole prior to insertion of the catheter with a wire.
BRIEF DESCRIPTION OF THE DRAWINGS
The method and apparatus of the invention will now be described with reference to the accompanying drawings, in which:
Figure 1 is an elevation of an epidural needle, with syringe, inserted into the epidural space of a spine;
Figure 2 is an elevation showing a cannula inserted into the epidural needle;
Figure 3 is an elevation showing the cannula extended to tension the dura-arachnoid membrane;

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Figure 4 is an elevation showing the cannula advanced and locked in place by a clamp;
Figure 5 is an elevation showing a sbarply pointed stylet inserted into the cannula for piercing the dura-arachnoid membrane;
Figure 6 is an elevation showing a hole pierced in the dura-arachnoid membrane;
Figure 7 is an elevation showing a catheter with a wire slidably inserted therein penetrating a hole in the dura-arachnoid membrane, the end of the wire protruding slightly beyond the end of the catheter;
Figure 8 depicts the advance of the catheter with the wire a desired distance into the subarchnoid space, as indicated by a màrk on the catheter;
Figure 9 is an elevation showing the withdrawal of the cannula with epidural needle, and wire, from the patient with the catheter left in site:
Figure 10 is a perspective view in more detail of the hub of the epidural needle showing the clamp engaging the cannula;
Figure 11 is a perspective view of the circular clamp illustrated in Figure 10 released from the cannula;
Figure 12 is a plan view of the clamp in its locking position corresponding to Figure 10;

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Figure 13 is an elevation of the cannula and epidural needle frictionally connected together at the hub end of the catheter, the clamp separated from the hub of the epidural needle, and with a syringe inserted into the catheter hub;
Figure 14 is an enlarged view of the end of another embodiment of cannula.
Figura 15 is a plan view of another embodiment of pivot clamp; and Figure 16 is a perspective view of the pivot clamp shown in Figure 15.
DESCRIPI~ION OF THE PREFERRED EMBODIMENTS
~; Figure 1 of the drawings illustrates the placement of a hollow epidural needle 10 having a sharpened end 12 inserted into the back 14 of a patient between the spinous processes 16 o~ the vertebrae and through the ligamentum flavum 18 into the epidural space 20. The opposite end of needle 10 has a hub 22 having a conventional conical interior for receiving the forward extension 24 of a syringe 26 and a pivot clamp or the like connector 30 shown in more detail in Figures 10, 11 and 12.
With reference now to Figures 10, 11 and 12, pivot . clamp 30 comprises a clamp arm 32 pivotally mounted on lateral extension or tab 36 formed adjacent the edge 38 ; of hub 22 by a stud 40. A transverse line of weakness 42 :
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is formed in tab 36 to permit separation of tab 36 from hub 22 for reasons which will become apparent as the description proceeds.
Clamp arm 32 has a peripheral reverse flange 44 adapted to overlap and engage flange 34 of hub 22 when clamp 32 is pivotted to the operative position shown in Figures 4, 10 and 12. An opening 46 on each of side edge 47 of clamp arm 32 defines slightly more than a semi-circle with a diameter su~stantially equal to the diameter of a cannula, to be described, whereby the clamp arm 32 can be snap-fitted over the cannula for frictional engagement, as shown most clearly in Figures 10 and 12.
With reference now to Figure 2, cannula 50 having a blunt distal end 52 and a hub 49 at the proximal end has a diameter slightly 1QSS than the interior diameter of the needle 10 to allow placement into and coaxial ~ovement within needle 10 such that the distal end 52 of cannula 50 can be advanced forwardly for alignment with the end 12 of needle 10 when mark 51 on the cannula is aligned with the end of needle hub 22.
With reference now to Figures 3 and 4, cannula 50 with blunt end 52 is advanced forwardly to place dura-arachnoid membrane 53 in tension and the cannula locked from axial movement by pivotting clamp arm 32 upwardly as . 25 viewed in Figures 4 - 9 of the drawings such that cannula ` 50 is frictionally engaged by the wall of an opening 46 :~' when clamp arm 32 is snap-fitted thereover with reverse flange 44 engaging flange 34 of needle hub 22.
Figure 5 illustrates a sharp stylet 55 advanced through cannula 50 to pierce the taut dura-arachnoid membrane 53 by pointed tip 58 when flanged head 57 abuts the end of hub 49 of cannula 50 to form a hole 60 (Figure 6). Stylet 55 preferably would have a diameter about the same as or slightly less than the external diameter of catheter 54 to ensure a tight fit of the catheter in hole 60 to prevent the flow of cerebral-spinal fluid from the sub-arachnoid space into the epidural space.
A catheter 54 with an interior wire 56 slidably mounted therein havlng an end pro;ecting beyond the ~orward end of catheter 54 is inserted into cannula 50 and advanced forwardly to enter hole 60, as shown in Figure 7. Catheter 54 can be advanced through hole 60 in dura-arachnoid membrane 53 a desired length as indicated by mark 62 on the catheter by pushing catheter 54 with stiffening wire 56 forwardly through the dura-arachnoid membrane 53 until mark 62 on cather 54 is aligned with the proximal end of cannula hub 49, as shown in Figure 8.
It may be preferred not to use stylet 55, in which case wire 56 would be sharply pointed and would extend beyond the tip of catheter 54 to pierce the dura-; 25 arachnoid membrane 53 when catheter 54 is advanced . against membrane 53.

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When the catheter 54 has been extended to its desired length into the subarachnoid space through the dura-arachnoid membrane 53, as indicated by lining up mark 62 on catheter 54 with the proximal end of hub 49 of cannula 50, epidural needle 10 with cannula 50 attached thereto by clamp 32 is removed from the patient, with the catheter 54 remaining in position, as typified in Figure 9. With reference now to Figure 13, clamp 32 is removed from cannula 50 and is then broken at line of weakness 42, when desired, for removal of said clamp, the hub 49 of cannula 50 is advanced into the hub 22 of epidural needle 10, and needle 10 with cannula 50 nested therein is retracted to receive the hub 68 of catheter 54 at the free end of catheter 54. A sufficient length of catheter 54 is provided to permit taping of the catheter to the patient with the epidural needle and cannula connected together in such a manner that the cannula prevents the catheter from being cut by the sharp end of . the needle.
An anaesthetic can be continuously administered to ` the patient through the catheter 54 by syringe 70 which .~
is coupled either directly or by means of an extension tubing to hub 68 of catheter 54 which is fitted tightly . into the hub 49 of cannula 50.

12 ~3 2 ~ t 9 4 Figure 14 illustrates an embodiment of cannula in which the blunt distal end 80 has an inner bevelled, i.e.
sharp, extension to pierce the dura-arachnoid membrane while maintaing the membrane taut.
Figure 15 and 16 illustrate another embodiment of pivot clamp 80 in which clamp arm 82, having over-centre semi-circular side openings 84 adapted to snap-fit onto cannula 50, has a transverse line of weakness formed by surface notch 86 interconnecting openings 84. The free end 88 of clamp arm 82 is extended to provide leverage to facilitate the breaking of clamp arm 82 to free cannula 50, when desired.
Reverse flange 90 formed in the underside of clamp arm 82 preferably has serrations 92 adapted to engage mating serrations 94 formed in the underside of rim flange 34 to effectively lock clamp 80 against cannula 50 by a friction fit of cannula 50 in an opening 84.
It will be understood that modifications can be made in the embodiment of the invention illustrated and described herein without departing from the scope and purview of the invention as defined by the appended claims.

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13 i 3 2 6 SUPPLEMENTARY DISCLOSURE
I have found that the blunt end of a cannula can be provided by a splayed end of the cannula for effective abutment against the dura-arachnoid membrane to place the membrane in tension.
As an alternative to the catheter, a flexible or semi-rigld spinal needle can be inserted through the cannula to allow the single administration of a spinal anaesthetic. Accordingly, the method and system of the invention have utility in the insertion of catheters and needles for continuous and single administrations of anesthetics.

In accordance with an aspect of the system of the invention, for the insertlon of a flexible catheter through the epidural space and dura-arachnoid membrane into the subarachnoid space of a spine, the system comprises a hollow needle having a sharpened entry end for insertion into the epidural space and an exit end having a hub, a cannula with a splayed distal end adapted for placement into and axial movement within the hollow needle whereby said cannula can be advanced forwardly within the hollow needle for abutment of the splayed distal end against the dura-arachnoid membrane to place tenslon on the dura-arachnoid membrane, securing means adapted to be attached to the hub at the exit end of the hollow needle for locXing the cannula within the hollow needle from axial movement, and a flexible catheter having a wire therein for insertion through the cannula and penetrating the dura-arachnoid membrane forming a hole, whereby the distal end of the catheter can be inserted a predetermined distance into the subarachnoid space through said hole, the cannula and the hollow needle retracted along the catheter, the 6ecuring means removed, and the wire withdrawn from the catheter.

In accordance with an aspect of the method of the invention for passing a catheter through the epidural space and dura-14 1 3 ~ 6 i v ~
arachnoid membrane into the subarachnoid space of a patient' 8spine, the method comprises the steps of inserting a hollow needle having a !~harpened entry end into the epidural space, said hollow needle having an exit end with a hub, inserting a cannula with a splayed distal end into the hollow needle and advancing the cannula forward for abutment of the splayed distal end of the cannula against the dura-arachnoid membrane to place the dura-arachnoid membrane in tension, locking the cannula from coaxial movement in the needle, inserting a flexible catheter having a wire therein through the cannula and penetrating the tensioned dura-arachnoi~ membrane through a hole herein whereby the distal end of the catheter can be fed a predetermined distance into the subarachnoid space through the hole formed in the dura-arachnoid membrane, and retracting the hollow needle and cannula along the catheter and withdrawing the wire while the distal end of the catheter remains inserted in the said subarachnoid space.
In accordance with another aspect of the present invention, as an alternative to inserting a flexible catheter containing a wire, a fine flexible or semi-rigid spinal needle can be passed through the ~annula and penetratQ the tensioned dura-arachnoid membrane for insertion into tha subarachnoid space for the administration of single dose spinal anaesthesia.

These embodiments of the method and apparatus of the invention will now be described with reference to the accompanying drawings, in which:

Figure 17 is an elevation of a cannula with a slidable sleeve on the shaft of the cannula;

Figure 17(a~ is a plan view of the cannula showing the end splayed into one tab;
Figure 17(b) is a plan view of the cannula showing the end splayed into four tabs;
Figure 18 i8 an elevation of the cannula with the sleeve slid forward to hold the previously splayed tab(s) within the sleeve in a straightened position, ready to enter the epidural needle;
Figure 19 is an elevation of the cannula poised about to enter the epidural needle which is inserted into the epidural space of the spine;
Figure 20 is an elevation showing the cannula advanced coaxially through the epidural needle with the sleeve of the cannula located in the hub of the epidural needle and the tip of the cannula co-extensive with the tip of the epidural needle;
Figure 21 is an elevation showing the cannula advanced to permit the tabs of the cannula to become splayed outwardly within the epidural space;
Figure 22 is an elevation showing the cannula advanced to tension the dura-arachnoid membrane and the cannula locked in this position by a clamp incorporated into the hub of the epidural needle;
Figure 23 is an elevation showing a pointed stylet inserted through the cannula to pierce the dura-arachnoid membrane;
Figure 24 is an elevation showing a catheter containing a sharpened wire protruding therefrom, inserted through the cannula, piercing the dura-arachnoid membrane, and threaded into the subarachnoid space a predetermined distance;
Figure 25 is an elevation showing the catheter after the cannula-epidural needle assembly has been partially withdrawn;
Figure 26 is an elevation showing the cannula-epidural assembly and sharpened wire completely withdrawn leaving the catheter in place;
Figure 27 is an elevation showing the catheter, cannula, sleeve and epidural needle withdrawn and frictionally attached together, a syringe frictionally attached to the catheter hub, and the clamp disassembled from the cannula;
Figure 28 is an elevation showing a spinal needle inserted through the cannula and piercing the dura-arachnoid membrane; and Figure 29 is an elevation showing a syringe attached to the hub of the spinal needle.

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With reference to the drawings, Figure 17 illustrates cannula 161 with shaft 150, splayed distal end 156, and hub 149 at the proximal end. The distal end 156 splays into one or more flexible tabs 157 which curl backwards (ie. proximally) when in neutral or resting position. Sleeve 179 fits slidably over shaft 150 and has ~ conical exterior to fit into hub 122 of epidural needle 110, as seen in Figures 19 - 29. The distal end 156 of cannula 161 preferably is formed of reæilient plastic material and is splayed radially outwardly such that the tabs are resiliently biased in an outward direction.
Figure 17(a) is a plan view of hollow cannula shaft 150 with the distal end 156 splayed outwardly to form single tab 157.
Figure 17(b) is a plan view of cannula shaft 150 showing another embodiment wherein the di~tal end of the cannula shaft 150 is splayed into four tabs 157. It will be understood that the distal end 156 of cannula 161 can be composed of one or more tabs 157 which splay radially outwardly in a curled fashion.
Sleeve 179 slides axially over tabs 157 to hold them in a non-splayed or straightened position pointing distally, as 6hown in Figure 18. When in this position, tabs 157 collectively form end 152 of cannula 161. Sleeve 179 is slid to this position ~ust prior to u~e.
Figure 19 illustrates the placement of hollow epidural needle 110 having a pointed end 112 inserted into the back 114 of a patient between the spinous processes 116 of the vertebrae, and through the ligamentum flavum 118 into the epidural space 120.

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The opposite end of the needle 110 has a hub 122 having a conventional conical interior for receiving a standard forward extension of a syringe and for receiving sleeve 179. A pivot clamp or the like connector 130 is formed integral therewith.
Cannula 161 with sleeve 179 holding tabs 157 straight is shown in a position to enter hub 122 of epidural needle 110. Shaft 150 of cannula 161 has a diameter slightly les6 than the interior diameter of epidural needle 110 to allow placement into and forward coaxial movement within needle 110. During this forward movement, tabs 157 are held straight by needle 110 until they l7 13261 Ji~

emerge from needle end 112 into the epidural space 120.
Figure 20 shows cannula 161 advanced coaxially within epidural needle llO so that the distal end 152 of cannula 161 i8 coextensive with the distal end 112 of epidural needle 110 when line 151 on the cannula is even with hub 122 of the epidural needle 110. Tabs 157 of the cannula are still held straight pointing distally inside epidural needle 110. With reference to Figure 21, cannula 161 is advanced axially distally and tabs 157 emerge from end 112 of epidural needle 110 to splay outwardly to resume their original open curled shape in epidural space 120.
With reference now to Figure 22, cannula 161 is advanced further so the open tabs 157 push the dura-arachnoid membrane 153 forward ànd place it in tension. When the dura-arachnoid membrane is judged to be in suitable tension, the cannula is locked from coaxial movement by pivoting clamp 132 which is pivoted upwardly, as viewed in Figures 22 through 26, such that the cannula shaft 150 is frictionally engaged by the wall of an opening 146 when clamp arm 132 is snap-fitted thereover with reverse flange 144 engaging flange 134 of hub 122.
Figura 23 illustrates a sharp stylet 155 advanced through `':
cannula 161 to pierce and form a hole in th taut dura-arachnoid membrane 153 by pointed tip 158 when flanged head 159 abuts the end of hub 149 of cannula 161. Figure 24 shows stylet 155 removed and catheter 154 advanced through said hole a desired length by pushing catheter 154 containing stiffening wire 156 forwardly through the dura-arachnoid membrane 153 until mark 162 is aligned with the proximal end of hub 149. It may be preferred not to use stylet 155, in which case wire 156 would be sharply pointed and would extend beyond the tip of catheter 154 to pierce the dura-arachnoid membrane 153 when catheter 154 i8 advanced against membrane 153.

With reference now to Figure 25, the epidural needle 110 with cannula 161 attached thereto by clamp 132 is partially withdrawn. This results in tabs 157 of cannula 161 becoming straightened in an extended position in the tract left by needle 110 and the dura-subarachnoid membrane 153 returning to its 18 132~

original non-tensioned position le~ving catheter 154 with wire lS6 inserted the. desired distance into the subarachnoid space 167. Figure 26 illustrates the cannula-epidural needle assembly 161-110 and wire 156 completely removed from the patient and tabs lS7 of cannula 161 returned to their original splayed open position having emerged from the needle tract.
Turning now to Figure 27, clamp 132 is removed from cannula shaft lSO to allow further coaxial advancement of cannula 161 within epidural needle 110 so cannula hub 149 fits frictionally inside sleeve 179 which is fitted frictionally inside needle hub 122. This ass embl y i s now slid proximally coaxially along catheter 154 to catheter hub 168~ The assembled members now comprise catheter hub 168 fitted to cannula hub 149 which is fitted to sleeve 179 which is fitted to needle hub 122. Shaft 150 of cannula 161 extends distally beyond the end 112 of needle :`
110, preventing the catheter lS4 being cut by the sharp end 112 of needle 110. An anaesthetic can now be continuously or intermittently administered through catheter lS4 by syringe 170 or other source of an anaesthetic solution which is coupled either directly or by means of an extension tubing to hub 168 of catheter 154.
Figure 28 illustrates an alternate application of the method and the system of the invention for the administration of a single dose spinal anaesthetic (ie. subarachnoid anaesthetic) through a fine flexible or semi-rigld metal splnal needle. Once the dura-subarachnoid membrane is fixed in tension as illustrated in Figure 22, a fine spinal needle is inserted as illustrated in Figure 28. This figure shows spinal needle 164 inserted coaxially through cannula 161 such that when hub 160 of spinal needle 164 abuts the cannula hub 149, and cannot be inserted further, the spinal needle 164 has pierced the dura-arachnoid membrane 153 and the needle 164 has entered the de~ired distance into the subarachnoid space 167 which contains cerebral-spinal fluid 166. The cerebral-spinal fluid 166 then flow6 proximally through needle 164 and forms a drop 166 in the spinal needle hub 160, confirming the correct placement of needle 164 in the /'-1 1326 L~
subarachnoid space 167. With reference to Figure 29, a conventional syringe 170 with a standard injection tlp fits lnto the standard interior of spinal needle hub 160 for the slngle administration of a spinal anaesthetic following which the entire assembly is removed.
It will be understood that modifications can be made of the embodiment of the invention illustrated and described herein without departing from the scope and purview of the invention as defined by appended claims.

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Claims (8)

1. A catheter system for the insertion of a flexible catheter through the epidural space and dura-arachnoid membrane into the subarachnoid space of the spine of a patient comprising:
(a) a hollow needle having a sharpened tip, for insertion into the epidural space, and an exit end having a hub;
(b) a cannula with a blunt distal end adapted for placement into and for coaxial movement within the hollow needle, whereby said cannula can be advanced forwardly within the hollow needle for abutment of the blunt distal end against the dura-arachnoid membrane to place the dura-arachnoid membrane in tension:
(c) securing means adapted to be attached to the hub at the exit end of the hollow needle for locking the cannula within the hollow needle from coaxial movement therein;
and (d) a flexible catheter having a wire therein for insertion through the cannula and for penetrating the dura-arachnoid membrane, whereby the distal end of the catheter can be inserted a predetermined distance through the dura-arachnoid membrane into the subarachnoid space, the cannula and the hollow needle retracted along the catheter, and the wire withdrawn from the catheter.

2. A catheter system as claimed in claim 1 in which the wire extends beyond the distal end of the catheter and said end of the wire extending beyond the distal end of the catheter is sharpened.

3. A catheter system as claimed in claim 1 in which the securing means comprises a clamp pivotally mouhted on a lateral extension of the hub of the hollow needle, said clamp having an opening formed on a side thereof from frictionally engaging and locking the cannula from coaxial movement in the hollow needle.

4. A catheter system as claimed in claim 3 in which said lateral extension of the hub hub a line of weakness formed therein adjacent the hub to permit separation of the lateral extension from the hub.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

5. A system for the insertion of a flexible catheter or a fine flexible or semi rigid needle through the epidural space and dura-arachnoid membrane into the subarachnoid space of the spine of a patient comprising:
(a) a hollow needle having a sharpened tip, for insertion into the epidural space, an exit end having a hub;
(b) a cannula with a splayed distal end having at least one flexible tab at said distal end;
(c) a sliding collar for axial advancement over the splayed end of said cannula to straighten said tab(s) to allow the cannula to be placed into and introduced forwardly coaxially into the hollow needle, whereby the said collar remains in the hub of the needle, and the end of said cannula, after emerging from the hollow needle, splays and abuts against the dura-arachnoid membrane to place the dura-arachnoid membrane in tension;
(d) securing means adapted to be attached to the hub at the exit end of the hollow needle for locking the cannula within the hollow needle from coaxial movement therein;
(e) a flexible catheter having a wire therein for insertion through the cannula and for penetrating the dura-arachnoid membrane, whereby the distal end of the catheter can be inserted a predetermined distance through the dura-arachnoid membrane into the subarachnoid space, the cannula and the hollow needle retracted along the catheter, and the wire withdrawn from the catheter; or (f) a flexible or semi-rigid needle having a sharpened tip for insertion through the cannula and penetration into the dura-arachnoid membrane whereby the distal end of the needle can be inserted a predetermined distance through the dura-arachnoid membrane into the subarachnoid space, and an exit end having a hub to fit a syringe.

6. A system as claimed in claim 5 in which the wire extends beyond the distal end of the catheter and said end of the wire extending beyond the distal end of the catheter is sharpened.

7. A system as claimed in claim 5 in which the securing means comprises a clamp pivotally mounted on a lateral extension of the hub of the hollow needle, said clamp having an opening formed on a side thereof from frictionally engaging and locking the cannula from coaxial movement in the hollow needle.

8. A system as claimed in claim 7 in which said lateral extension of the hub has a line of weakness formed therein adjacent the hub to permit separation of the lateral extension from the hub.