Abstract:
An improved catheterization device of the type in which a flexible catheter overlays a rigid or semi-rigid stylet, the improvement residing in the preformed arcuate curvature of the stylet, the curvature of which can be in the form of a circular arc, an elliptical arc, or an irregular curvature, for facilitating insertion of the catheter into the blood vessel of a subject with reduced risk of vascular damage or where the direct path to the blood vessel is obstructed, and methods for its use.

Description:
CROSS-REFERENCE 
       [0001]    The present application claims priority from U.S. Provisional Patent Application No. 60/834,473 filed Jul. 31, 2006, the contents of which are hereby incorporated in their entirety by reference, and which is not admitted to be prior art by its mention in the background. 
     
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a system for placing a catheter in a blood vessel, and more particularly to an improved catheterization device of the catheter-over-needle type and to a method for its use. 
       BACKGROUND OF THE INVENTION 
       [0003]    Placement of a catheter into a blood vessel of a human patient may be performed for a variety of medical, therapeutic and diagnostic purposes. For example, percutaneous insertion of a catheter into the jugular or subclavian vein is often performed to enable measurement of central venous pressure or to facilitate total intravenous feeding or to administer other intravenous therapy. 
         [0004]    Percutaneous insertion of a catheter (herein “catheterization”) into a blood vessel generally involves the use of a catheter-over-needle or a catheter-through-catheter placement technique. The catheter-over-needle placement technique generally uses a catheter of up to about four inches in length that has a tapered end with a sharp, straight needle or stylet extending from the tapered end. The needle or stylet is inserted into a blood vessel, after which the needle or stylet is withdrawn. The catheter may then be pushed further along the blood vessel. 
         [0005]    Difficulties in catheterizing certain kinds of patient may arise using a catheter-over-needle technique. Elderly patients or drug-abusers may have veins that are particularly susceptible to needle damage, either from fragility or prior abuse. Also, in obese patients the correct depth of needle or stylet insertion may be difficult to assess, resulting in an increased probability that the blood vessel may be missed or penetrated completely resulting in vessel damage and bleeding into the surrounding tissues. 
         [0006]    Difficulties in catheterization using prior art devices may also arise where direct access to a target blood vessel is blocked by bone or other obstruction as may occur, for example, in catheterization of a subclavian vein. 
         [0007]    Catheterization of blood vessels oriented substantially parallel to the skin can be problematic because insertion of the needle or stylet at a large acute angle relative to the skin results in penetration of the blood vessel wall at a corresponding large acute angle and increased probability of damage or penetration of the opposite blood vessel wall. While this problem may be somewhat ameliorated by inserting the needle or stylet into the skin at a small acute angle, this technique either increases the length of the catheterization device required or reduces the length of the catheter that is available for insertion into the blood vessel. 
         [0008]    Further, the catheter-over-needle technique requires that the needle or stylet and the overlaying catheter must be handled carefully during catheterization to minimize the risk of damage to the wall of the catheter. Thus, for example, flexing of the stylet should be avoided. 
         [0009]    While elaborate devices and techniques are known for the guidance of catheters once inserted into a blood vessel (see, e.g., U.S. Pat. Nos. 4,468,224, and 6,379,346 B1), and for the production of catheters capable of assuming a desired shape once the needle or stylet is withdrawn (see, e.g., U.S. Pat. Nos. 3,719,737 and 5,044,369), these approaches do not address the difficulties described above relating to initial catheterization. 
         [0010]    Therefore, notwithstanding the existence of a variety of catheterization devices in the prior art, there is a continuing need for a device that permits catheterization of veins for which a direct approach is blocked by bone or other obstruction, and for a device that lessens the risk of vein wall damage in catheterization of blood vessels of drug abusers, the obese, and the elderly, and the present invention substantially fulfills these needs. All this and more will become apparent to one of ordinary skill, upon reading the disclosure, drawings, and claims appended hereto. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention is directed to a catheterization device, and method for its use, that satisfies the above need for improved catheterization of veins for which a direct approach is blocked, and for a device that lessens the risk of vein wall damage in catheterization of blood vessels of drug abusers, the obese, and the elderly. The inventors have surprisingly found that a device in which the stylet comprises a preformed arc along substantially its entire length satisfies at least the aforementioned needs. 
         [0012]    In a first embodiment, the device comprises a flexible catheter, the proximal end of which is mounted to the distal end of a tubular fitting, such as for example a female luer fitting, with the interior surfaces of the catheter and the fitting in fluid communication. The device further comprises a preformed arcuate stylet comprising a tip adapted for penetrating tissue. The stylet is disposed within the catheter and the tip of the stylet extends from the distal end of the catheter. A sealing member seals the proximal end of the fitting in a readily detachable manner. 
         [0013]    In a second embodiment, the device optionally further comprises a detachable covering mounting to the sealing member to substantially enclose and protect the catheter, stylet, and fitting when not in use. 
         [0014]    In a third embodiment, the device optionally comprises a means for retracting the stylet into the sealing member. For example, the stylet can be operably connected to a preloaded spring and trigger housed within the sealing member whereby operation of the trigger causes the spring to retract the stylet into the sealing member for safety. 
         [0015]    In a fourth embodiment, the arc of the stylet is selected from circular, elliptical, and irregular arcs. 
         [0016]    In a fifth embodiment, a method for blood vessel catheterization is provided for using the catheterization device of the present invention. The tip of the stylet is first positioned upon the skin of a subject proximal to a blood vessel. The tip of the stylet and at least a portion of the overlying catheter are inserted into the blood vessel by causing the tip to substantially follow the arcuation of the stylet in its passage from the skin to the blood vessel. The stylet is withdrawn from the catheter to leave the catheter in place. The sealing member is detached. It will be apparent that, according to the particular construction of the device, the steps of the preceding method can be performed in alternative orders, all of which are envisaged as being within the scope of the present invention. 
         [0017]    It is therefore an object of the present invention to provide an improved catheterization device, and method for its use, for increased ease of catheterization of blood vessels for which the direct pathway for catheterization is obstructed by bone or other obstruction. 
         [0018]    It is a further object of the present invention to provide an improved catheterization device that reduces the likelihood that a vein will be damaged or passed through during catheterization. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, claims, and accompanying drawings, where: 
           [0020]      FIG. 1  shows a perspective view of an embodiment of the catheterization device according to the present invention. Inset: a sectional view of circled portion. 
           [0021]      FIG. 2  shows longitudinal cross-sectional view of the catheterization device according to  FIG. 1 , further comprising an optional detachable covering. 
           [0022]      FIG. 3  shows embodiments of the catheterization device of the present invention comprising various preformed arcuate stylets: A-C circular arcs of differing radii; D an elliptical arc; E an irregular arc. 
           [0023]      FIG. 4  shows an alternative embodiment of the catheterization device according to the present invention comprising a two-piece sealing member. A assembled; B and C disassembled. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Certain exemplary but non-limiting embodiments of the present invention will now be described with reference to the attached drawings. 
         [0025]    Referring now to  FIG. 1 , there is shown an embodiment of a catheterization device  100  according to the present invention. The device  100  comprises a tubular fitting  102 , a flexible catheter  104 , a preformed arcuate stylet  106 , and a sealing member  108 . 
         [0026]    Tubular fitting  102  can be formed from any rigid or semi-rigid material, such as a plastic or metal, provided that the material is capable of forming a self-supporting fitting having a proximal end adapted for mounting to a means of fluid delivery or collection, such as a syringe tip or the connector of an intravenous drip. Preferably, tubular fitting  102  is a luer fitting, as is known in the art, and most preferably fitting  102  is a female luer fitting. The distal end  110  of the tubular fitting  102  is optionally narrower than proximal end  112 , and has a diameter similar to or greater than the diameter of flexible catheter  104 . Between the proximal  112  and distal  110  ends, the fitting  102  comprises an inner surface  114 . The tubular fitting  102  optionally comprises other desirable features such as, for example, one or more projections  126  providing improved grip and features  128  for securing the fitting to the means of fluid delivery or fluid collection. 
         [0027]    Flexible catheter  104  can be formed of any biocompatible flexible material, such as medical grade silicone rubber, polyurethane, polyethylene polyvinyl chloride, Teflon™, siliconised latex, or the like. The proximal end  122  of the catheter  104  is mounted to the distal end  110  of fitting  102  to permit leak-free, fluid communication between the inner surface of the fitting  114  and the inner surface of the catheter  116 . The distal end  124  of the catheter  104  is optionally tapered or otherwise shaped or treated for improved penetration of tissue and for reduced damage to vessel walls. 
         [0028]    Arcuate stylet  106  can be preformed from any sufficiently rigid material capable of forming a slender arcuate body for penetration of tissue by tip  126 . The stylet  106  can, for example, be formed from a metal such as stainless steel, or from a rigid polymeric material. Preferably, the stylet  106  is a tubular body such as a syringe needle comprising a hollow-ground point. The arcuate stylet  106  is preformed in the shape of an arc of a circle, or an arc of an ellipse, or an irregular arcuate form. The term “preformed” as used herein refers to the manufacture of an arcuate stylet prior to its combination with an overlying catheter. In embodiments comprising an arcuate form that is the arc of a circle, the radius of the arc is preferably between about 1.5 inches to about 12 inches. In other embodiments, the arcuate form of the stylet can be in the form of an elliptical arc according to known mathematical equations for ellipses. The stylet can also comprise an arc that does not conform to any simple mathematical equation, which is herein termed an “irregular” form ( FIG. 3E ). More specifically, the choice of arcuate form may be a matter of user preference or may be determined by physiological constraints at specific catheterization sites and/or types of patient, such as, for example, subclavian or jugular catheterization of minors, adults, or animals. 
         [0029]    Stylet  106  is disposed in the lumen of the catheter  104 , preferably for at least the length of the catheter, and the tip  126  of the stylet protrudes from the distal end  124  of the catheter. The catheter  104  thereby conforms to the arcuate shape of the stylet  106  at least until the stylet  106  is withdrawn. 
         [0030]    Sealing member  108  mounts to the proximal end  112  of the fitting  102 , for example to aid sterility, until the proximal end  112  is exposed in use. The shape and material of the sealing member  108  are not particularly limited, and can be, for example, in the form of a tube closed at one end, or a simple plastic or metal plug. In the exemplary embodiments shown in  FIGS. 1 and 2 , one end of stylet  114  is retained in the sealing member  108  which helps retain the sealing member  108  over proximal end  112  of the fitting until the stylet  106  and sealing member  108  are removed as an assembly. 
         [0031]    Referring now to  FIG. 2 , means that are well-known in the art for the avoidance of inadvertent needle-stick can optionally be included within sealing member  108  to retract stylet  106  under spring action into sealing member  108  when spring release button  130  is pressed. In the embodiment of  FIG. 2 , stylet retaining block  202  compresses spring  204  and is retained by trigger  206  which engages a depression in stylet retaining block  202 . Spring release button  130  releases spring  204 , whereby stylet  106  is rapidly withdrawn into sealing member  108 . 
         [0032]    Referring again to  FIG. 2 , the device of the present invention further optionally comprises a detachable cover  208  engaging sealing member  108  and substantially enclosing catheter  104 , stylet  106  and fitting  102 . The material of the cover is not particularly limited, and can be of a rigid polymer or metal. In embodiments comprising a longer stylet, or a highly arcuate form, the cover can also be non-linear to facilitate its removal in use. 
         [0033]    Referring now to  FIG. 3 , there catheterization devices according to the present invention comprising various different preformed arcuate stylets: circular arcs of different stylet radii  302 ,  304 ,  306 ; an elliptical stylet  308 ; and an irregular stylet  310  that is not elliptical or circular. 
         [0034]    Referring now to  FIG. 4 , an alternative embodiment  400  is shown in which the sealing member comprises two parts  402 ,  404 . Fitting  406  is mounted to a first portion  402  of the sealing member, and a second portion  404  of the sealing member sealingly engages the first portion  402  to perfect the seal. The stylet is affixed to the first portion  402 . 
         [0035]    A method of use of the device of the present invention will now be described for illustrative purposes. The optional cover  208 , if present, is removed and the stylet tip  126  is placed upon the skin of a subject close to a target blood vessel. The tip of the stylet is inserted into the vein by causing the tip to substantially traverse the arcuation of the stylet. Thus, for an embodiment in which the stylet is in the form of an arc of a circle, the tip is caused to traverse a substantially similar arc in passing from the skin to the blood vessel of a subject. By this means, the tip of the stylet can penetrate the skin at a large acute angle with respect to the skin surface, while the tip can subsequently enter the blood vessel at a smaller acute angle that is more nearly parallel with respect to the surface of the skin. Once the stylet has penetrated the blood vessel, the stylet is withdrawn while the catheter remains in place. In the embodiments of  FIGS. 1 and 2 , the stylet is retracted by pressing spring release button  130 . In the embodiments of  FIG. 4 , the first portion  402  of the sealing member and stylet  106  are withdrawn as a unit, and, optionally, the second portion of the sealing member  404  can be detached from the first portion  402  and mounted to the fitting for a temporary seal. 
         [0036]    A method for the use of a device of the present invention in which the stylet  114  is a tubular body such as a syringe needle will now be described for illustrative purposes. The optional cover, if present, is removed and the stylet tip  116  is placed upon the skin of a subject close to a target blood vessel. Next, the tip of the stylet is inserted into the blood vessel by causing the tip to substantially traverse the arcuation of the stylet. Upon penetration of the target blood vessel by the tubular stylet, blood flows through the tubular stylet and enters the tubular fitting  102 . The appearance of blood in the tubular fitting  102  provides a visual cue to a user to cease further insertion of the stylet tip  126 , thereby minimizing the risk that the stylet penetrates through the blood vessel into the surrounding tissue. The stylet  106  is withdrawn while the distal end  124  of the catheter  104  remains in place within the blood vessel and the stylet is retracted. 
         [0037]    The device of the present invention provides a number of advantages over the prior art. The preformed arcuate stylet permits catheterization of blood vessels for which a direct approach is blocked by bone or other obstruction. The arcuate stylet can penetrate the vein wall at a more acute angle with respect to the vein wall, whereby the risk of passing through the opposite vein wall is lessened. Thus, vein wall damage is decreased and bleeding into the tissues is lessened. These advantages are of particular benefit in the treatment of elderly patients or in the catheterization of veins of intravenous drug users, whose veins may already be damaged. The preformed arcuate stylet eliminates the risk of catheter damage that could accrue if bending of the stylet were attempted after the catheter was assembled to the stylet. 
         [0038]    While the present invention has been discussed within the context of intravenous catheterization, it will be readily appreciated that the invention can be used in other medical and veterinary contexts and for other purposes. In particular, the invention should not be construed as being limited to only intravenous applications. 
         [0039]    Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible and can be envisaged within the scope and spirit of the present invention. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein. 
         [0040]    Now that the invention has been described: