US20060282043A1 - Intrathecal catheter having a stylet with a curved tip - Google Patents

Abstract

An apparatus includes a catheter for an intrathecal drug delivery system and a stylet having a curved forward end. Preferably, the curved forward end has a shape in the form of a “J” or a “C.” Also preferably, the catheter has a distal end that conforms to the curved forward end of the stylet. Thus, the present invention provides a catheter having a blunt forward end that minimizes the risk of penetrating the substance of the spinal cord. Additionally, the curved forward end of the stylet can be formed of a springy material so that it straightens out during the processes of insertion through a guide needle and retraction from the needle.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application claims priority to U.S. Provisional Patent Application Ser. No. 60/690,253, filed Jun. 14, 2005, which is hereby incorporated herein by reference in its entirety for all purposes.
TECHNICAL FIELD
• The present invention relates generally to the field of surgical instruments and methods, and more particularly to an intrathecal catheter having a stylet with a curved forward end.
BACKGROUND OF THE INVENTION
• Human and animal subjects suffering from chronic pain have several options available to help alleviate the pain. One option is intrathecal drug delivery, in which a low dose of a medication, typically a narcotic such as morphine, is delivered to the intrathecal space (i.e., within the spinal canal). A typical system for intrathecal drug delivery includes a drug delivery pump implanted in the patient's abdomen, which has a reservoir for the medication, and a catheter leading from the pump into the intrathecal space. The pump releases the medication at a set rate, and the medication flows from the pump, through the catheter to the site of delivery in the intrathecal space. Intrathecal drug delivery is beneficial because typically smaller doses of the medication can be used to gain relief, as compared to the dosages of those medications taken orally.
• However, implanting the device is not without risk. Inadvertently implanting the catheter into the spinal cord can result in permanent injury to the spinal cord, potentially resulting in irreversible paralysis. For example, there is some risk that the practitioner, when placing the guide needle or the styletted catheter within the spinal canal, might puncture the spinal cord with the sharp tip of the guide needle and/or the styletted catheter and subsequently accidentally thread the styletted catheter into the center of the spinal cord. And since typically, most practitioners choose to perform this operation under general anesthesia in which the patient is completely unaware of the procedure, the patient will not know something is wrong until he or she wakes up, and in a more egregious case, the patient may wake up paralyzed from the waist down.
• Therefore, a need exists for an apparatus and method that allows a catheter for an intrathecal drug delivery system to be guided more safely into proper placement within the intrathecal space.
SUMMARY OF THE INVENTION
• Advantageously, the present invention provides an intrathecal catheter having a curved forward end for placement in the intrathecal space. The intrathecal catheter includes a guide wire or a stylet, within the catheter, that has a curved tip, and the tip of the catheter itself conforms to the shape of the stylet tip. Thus, the catheter provides a blunt forward end, which minimizes the likelihood of puncturing tissue, such as the spinal cord.
• In an example form, the present invention provides an apparatus including a catheter for an intrathecal drug delivery system and a stylet, wherein the stylet has a curved forward end. Thus, the catheter has a tip that can conform to the curved forward end of the stylet. Preferably, the curved forward end of the stylet is in the shape of a “J” or a “C.” Also preferably, the curved forward end of the stylet is formed of a resilient and flexible material.
• In one embodiment, the catheter has a single lumen for housing the stylet and for carrying a fluid from a fluid source to target tissue. Preferably, the catheter has a biocompatible body with at least one opening extending along the body near its distal end for drug delivery to target tissue.
• In another form, the present invention provides a method for introducing a catheter for an intrathecal drug delivery system into the intrathecal space. The method includes the steps of inserting a stylet having a curved forward end into an intrathecal catheter; inserting the intrathecal catheter into an incision in the body; and guiding the intrathecal catheter into the intrathecal space by manipulation of the combination of the stylet and the catheter. The method can further include the steps of removing the stylet from the intrathecal catheter such that the catheter tip straightens out in the intrathecal space; anchoring the intrathecal catheter to adjacent tissue; and connecting the intrathecal catheter to a drug delivery pump.
• In yet another example form, the present invention includes a kit for intrathecal drug delivery. The kit can include one or more of the following items packaged in a single kit: an intrathecal catheter, a stylet having a curved forward end, a drug delivery pump, a guide needle, an insertion device, a tunneling tool, and suturing supplies.
• These and other aspects, features and advantages of the invention will be understood with reference to the drawing figures and detailed description herein, and will be realized by means of the various elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following brief description of the drawings and detailed description of the invention are exemplary and explanatory of preferred embodiments of the invention, and are not restrictive of the invention, as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 depicts a perspective view of a catheter having a stylet with a curved forward tip according to an example embodiment of the present invention.
• FIG. 2 depicts a longitudinal cross-sectional view of an end portion of the catheter ofFIG. 1.
• FIG. 3 depicts a pictorial representation of advancing the catheter ofFIG. 1 through the intrathecal space.
• FIG. 4 depicts a pictorial representation of the catheter ofFIG. 1 implanted in the intrathecal space.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
• The present invention may be understood more readily by reference to the following detailed description of the invention taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. Also, as used in the specification including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment.
• Referring toFIGS. 1-4 acatheter10 having an associated flexible stylet orguidewire12 extending therethrough for an intrathecal drug delivery system is shown by way of an example embodiment. Intrathecal drug delivery systems, commonly referred to as morphine pumps, and methods of implanting such pumps are generally well known. Intrathecal drug delivery systems typically include acatheter10 and adrug delivery pump13, as shown inFIGS. 3 and 4. Referring back toFIGS. 1 and 2, thecatheter10 has abiocompatible body14 constructed of a biocompatible and flexible material. Preferably, thebody14 has a single lumen orcanal16 extending therethrough for carrying a medication from thepump13 to the intrathecal space and for housing thestylet12. Alternatively, thecatheter10 can include dual lumens, one for carrying a medication and one for housing thestylet12.
• In an example embodiment, thecatheter10 has a length of about 60 to about 90 cm, an internal diameter in the range of about 0.4 to about 0.6 mm and more preferably in the range of 0.5 mm to 0.6 mm. In an example embodiment, thecatheter10 has an internal diameter of about 0.53 mm. The external diameter can be about 1.0 to about 3.0 mm, and more preferably from about 1.4 mm to about 2.0 mm, though those skilled in the art will understand that the dimensions can be larger or smaller. Preferably, thecatheter10 has a closeddistal end17. Thedistal end17 also preferably includes at least one and preferably a plurality of lateral openings, slots, orholes18 in thebody14 ofcatheter10 through which the medication can be pumped. As shown in the figures, thecatheter10 has threesuch openings18, though those skilled in the art will understand that the catheter can have more or fewer openings. Those skilled in the art will also understand how to determine the placement of the openings and the spacing between theopenings18.
• Also, afitting19, such as a conventional fitting as shown inFIG. 4, can be attached to the proximal end of thecatheter10 to connect to thedrug delivery pump13 implanted in the patient's abdomen once thestylet12 has been removed.
• Thestylet12 has atip20 at its distal end and ahandle21 at its proximal end for manipulating the stylet. Those skilled in the art will understand that thehandle21 shown inFIG. 1 is exemplary and that the handle can have a variety of shapes and sizes. Preferably, thetip20 of thestylet12 has the shape of a “J”, a “C”, or is otherwise curved so as to provide a blunt, forward end that will not puncture tissue as the stylet and associatedintrathecal catheter10 are guided through the intrathecal space. Thus, thedistal end17 of thecatheter10 conforms to the shape of thetip20 of thestylet12. Preferably, thetip20 of thestylet12 is stiffer or less flexible than thedistal end17 of thecatheter10. By providing a blunt end, the risk of puncturing tissue that otherwise should not be punctured is greatly minimized, as compared to using a sharp tip.
• Preferably, thestylet12 is constructed of a resilient and flexible material that allows thetip20 to adjust from a curved position in its neutral state to a straight position when being inserted through a guide needle or when being retracted from thecatheter10. Thus, at least thetip20 of thestylet12 is springy or flexible in the sense that when the stylet is retracted from thecatheter10, the tip of the stylet straightens itself out, and in so doing straightens out thedistal end17 of thecatheter10, so that removal from the catheter is made easier and minimizes the chances of tearing the catheter. Thetip20 of thestylet12 can be constructed of a spring or coil material. Additionally, theentire stylet12 can be a unitary piece that is constructed of a resilient, flexible, and biocompatible material, such as a plastic or a metal.
• The size of thestylet12 can vary, but in an example embodiment, the diameter of the stylet is smaller than the internal diameter of thecatheter10 and is about 0.46 mm. Those skilled in the art will understand that thestylet12 can have a larger or smaller diameter, such as in the range of about 0.2 mm to about 0.52 mm and more preferably in the range of about 0.4 mm to about 0.5 mm. The length of thestylet12 is preferably similar to the length of thecatheter10, and can be about 38 cm to about 89 cm, though those skilled in the art will understand that the dimensions can be larger or smaller.
• The practitioner inserts thecatheter10 with thestylet12 through a guide needle previously inserted through an incision in the patient's back and into the intrathecal space. Those skilled in the art will understand where and how to insert the guide needle. To facilitate threading thestyletted catheter10 into the needle, aninsertion device22, as depicted inFIG. 1, can be used. Theinsertion device22 is funnel-shaped, and has a largerdistal end24 through which thecatheter10 andstylet12 are inserted, and a narrowerforward end26 which has an opening that can mate with the opening of the needle. Thus, theinsertion device22 facilitates threading thestyletted catheter10 through the needle by allowing the practitioner to insert thedistal end17 of the catheter along with thetip20 of the stylet into the insertion device. Alternatively, thestyletted catheter10 can be inserted through a guide needle having a flared proximal end. Also alternatively, the styletted catheter can be inserted through a stiff or rigid sheath. Additionally, theinsertion device22 or another generally funnel-shaped piece can be used to facilitate the threading of thestylet12 into thecatheter10.
• The guide needle or sheath generally deflects thecurved tip20 of thestylet12 to at least a somewhat straight position so that the catheter and stylet can be threaded through the needle or sheath. Thus, while thestyletted catheter10 is threaded through the needle, thetip20 of thestylet12, and hence thedistal end17 of thecatheter10, temporarily straighten out. Once thestyletted catheter10 is threaded through the needle, thetip20 of thestylet12 springs back into its curved shape (i.e., back to its neutral position), which causes thedistal end17 of thecatheter10 to curve in shape. Alternatively, the curved tip of thecatheter10 can be threaded through a needle or sheath of a diameter sufficient to accommodate the diameter of the catheter in its curved tip position. Thus, thecatheter10 has a blunt forward end that can be manipulated through the intrathecal space.
• The practitioner advances thecatheter10 into the intrathecal space, as pictorially shown inFIG. 3. The curved forward ends of both thestylet12 and thecatheter10 minimize the likelihood that the stylet or catheter would penetrate the substance of the spinal cord. Once thecatheter10 is properly positioned, the practitioner pulls thestylet12 rearwardly. As thestylet12 is pulled rearwardly, thetip20 straightens out to permit removal through thelumen16 while simultaneously straightening out thedistal end17 of theintrathecal catheter10. The practitioner removes thestylet12 from thecatheter10 while leaving the catheter positioned within in the intrathecal space. The practitioner secures and anchors theintrathecal catheter10 to adjacent tissue and connects it to thedrug delivery pump13 that is implanted in the patient's abdomen, as pictorially shown inFIG. 4. Those skilled in the art will understand how to tunnel thecatheter10 to the pump and how to connect it thereto using conventional techniques and conventional fittings that are well known. When activated, thepump13 delivers the medication from its reservoir, through thelumen16 of thecatheter10, and to the target tissue in the intrathecal space.
• Optionally, the tools that the practitioner uses to implant the catheter into the patient can be assembled into a single kit. For example, the kit can include acatheter10 with astylet12 having acurved tip20, apump13, a guide needle, aninsertion device22, a tunneling tool, an anchor, a sterile drape, and suturing supplies.
• While the invention has been described with reference to preferred and example embodiments, it will be understood by those skilled in the art that a variety of modifications, additions and deletions are within the scope of the invention, as defined by the following claims.

Claims (18)

1. An apparatus, comprising:

a catheter for an intrathecal drug delivery system; and

a stylet, wherein the stylet has a curved forward end.

2. The apparatus ofclaim 1, wherein the catheter comprises a lumen for housing the stylet.

3. The apparatus ofclaim 1, wherein the catheter has a tip that conforms to the curved forward end of the stylet.

4. The apparatus ofclaim 1, wherein the curved forward end of the stylet has a shape generally in the form of a “J.”

5. The apparatus ofclaim 1, wherein the curved forward end of the stylet has a shape generally in the form of a “C.”

6. The apparatus ofclaim 1, wherein the curved forward end comprises a resilient and flexible material.

7. The apparatus ofclaim 1, wherein the catheter has a biocompatible body with at least one opening extending along the body near its distal end for drug delivery to target tissue.

8. The apparatus ofclaim 7, wherein the intrathecal catheter has a closed distal end.

9. A method for introducing a catheter for an intrathecal drug delivery system into the intrathecal space, comprising:

inserting a stylet having a curved forward end into an intrathecal catheter;

inserting the intrathecal catheter having a forward tip into an incision in the body; and

guiding the intrathecal catheter into the intrathecal space by manipulation of the stylet.

10. The method ofclaim 9, further comprising removing the stylet from the intrathecal catheter such that the curved forward end of the stylet straightens out during removal from the catheter.

11. The method ofclaim 10, wherein removing the stylet further comprises causing the tip of the catheter to straighten out in the intrathecal space.

12. The method ofclaim 9, wherein inserting the catheter into the body further comprises inserting the catheter through a guide needle positioned in the intrathecal space.

13. The method ofclaim 9, further comprising anchoring the intrathecal catheter to adjacent tissue.

14. The method ofclaim 13, further comprising connecting the intrathecal catheter to a drug delivery pump.

15. A kit for intrathecal drug delivery, comprising:

an intrathecal catheter;

a stylet having a curved forward end; and

a drug delivery pump, wherein all of the above are packaged in a single kit.

16. The kit ofclaim 15 further comprising a guide needle and an insertion device.

17. The kit ofclaim 15 further comprising suturing supplies.

18. The kit ofclaim 15 further comprising a tunneling tool.

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