Abstract:
Intravenous access is achieved by introducing a catheter over an access needle which is initially present in the catheter. A tapered dilating element is positioned over the needle and provides a transition between the needle and a larger catheter lumen. The access needle is hollow and has a port which allows blood to flash back through a lumen of the catheter so that flashback can be observed on a catheter hub or the catheter itself.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the non-provisional of, and claims priority to U.S. Provisional Application No. 61/760,841 (Attorney Docket No. 28175-709.101), filed Feb. 5, 2013, the entire content of which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to methods and systems for performing venipuncture. More particularly, the present invention relates to a catheter and needle assembly which provides transcutaneous insertion of a large diameter catheter with a smaller diameter the needle into a patient&#39;s vein with optional blood flashback. 
         [0004]    The term “venipuncture” refers generally to the process of obtaining intravenous access for any one of a variety of purposes, including intravenous infusion, therapy, blood sampling, and the like. In the hospital, for example, venipuncture is commonly used to place a small intravenous catheter for delivering intravenous fluids, drug delivery, blood sampling and the like. 
         [0005]    Venipuncture for catheter placement comprises placing a catheter over an access needle and inserting the access needle and catheter into a peripheral vein by penetrating the needle through the skin surface. One challenge to venipuncture is the introduction of large diameter catheter. Such introduction frequently requires use of a large diameter needle which can be painful for the patient. While it has been propose to grind down the needle tip to reduce discomfort (see, e.g. U.S. Pat. No. 4,767,407), such grinding significantly increases the cost of the needle. Alternatively, it has been proposed to taper the catheter tip down to the smaller needle diameter (see, e.g. U.S. Pat. No. 6,273,871), but such tapering reduces the catheter tip diameter which can be disadvantageous. 
         [0006]    Another challenge to venipuncture is the delay in observing “flashback.” In order to assure that the needle has reached the vein, the person inserting the needle will look for “flashback,” i.e. a flow of blood through a lumen of the needle to a proximal end of the needle where the appearance of blood can be observed. As venous access needles can be long, there can be a perceptible delay between the actual entrance of the needle tip into the vein and the appearance of blood at the proximal end of the needle. While such delays will typically be relatively short, even very small delays between vein entry and the appearance of flashback can result in misplacement of the needle. For example, the needle may continue to be advanced and pierce the opposite wall of the vein. Such “overshoot” is obviously undesirable and should be avoided. 
         [0007]    For these reasons, it would be desirable to provide improved apparatus and methods for performing venipuncture. In particular, it would be desirable to provide apparatus and methods which allow the use of reduced size needles for advancing relatively large diameter catheters. It would be further desirable to provide methods and apparatus for detecting blood which minimize the delay between actually entry of a needle tip into a vein and the appearance of blood flashback to the user introducing the needle and catheter. It would be further desirable if such improved methods and apparatus could be provided without the need to significantly modify the design or increase the cost of the catheter and/or access needle and with minimum change in the protocol used by those introducing the needles and catheters. At least some of these objectives will be met by the inventions described below. 
         [0008]    2. Description of the Background Art 
         [0009]    Needle and catheter assemblies are described in U.S. Pat. Nos. 3,469,579; 4,368,730; 4,767,407; 6,273,871; and U.S. Patent Publ. No. 2011/0208157. The following commonly owned applications, the full disclosures of which are incorporated herein by reference, also describe needle and catheter assemblies: U.S. Patent Publ. Nos. 2010/0094310; 2010/0210934; and 2012/0197200. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention provides needle and catheter assemblies and methods for their use. In a first aspect of the invention, a needle and catheter assembly comprises a catheter body having a proximal end, a distal end, and a lumen therethrough. A needle is removably received in the catheter lumen, and the needle has a tissue-penetrating distal end and a lumen therethrough. A tapered dilator element is mounted coaxially over the exterior of the needle proximal of the distal tip. The needle has a cross-sectional area which is less than the cross-sectional area of the catheter lumen so that the tapered dilating element occupies an annular gap which would exist between the needle and the interior of the distal end of the catheter in the absence of the tapered dilating element. 
         [0011]    In specific embodiments, the catheter body may consist of a tube having a single lumen configured to be positioned in a peripheral vein, and a proximal hub may be attached to the proximal end of the catheter body. The needle usually comprises a metal tube, and the tapered dilating element usually comprises a polymer collar. An exemplary access needle has a circular cross-section, and an exemplary catheter body lumen also has a circular cross-section, wherein the needle has an outer diameter in the range from 0.3 mm to 1.7 mm and the catheter body lumen has a diameter in the range from 0.4 mm to 2.8 mm. Usually, the inner diameter of the catheter body lumen is at least 20% larger than the outer diameter of the needle. 
         [0012]    In a second aspect of the present invention, a method for introducing a catheter into a vein comprises providing a catheter as described above. A distal end of the access needle carries a distal tip of the catheter into the vein in a distal direction. The tapered dilator element provides a transition from the small needle diameter to the larger catheter diameter to reduce patient discomfort. After the catheter has entered the vein, the catheter is advanced over the needle (and optionally a guidewire) to a target location in the vein. 
         [0013]    In a third aspect of the present invention, a needle and catheter assembly comprises a catheter body having a proximal end, a distal end, and a lumen therethrough. A needle is removably received in the catheter lumen, and the needle has a tissue-penetrating distal end, a lumen therethrough, and a flashback port proximal of the dilating element. The needle has a cross-sectional area which is less than the cross-sectional area of the catheter lumen so that blood which enters the needle can flow through the flashback port and into the catheter lumen where it will be visible through a transparent or translucent region in the catheter located near the distal end of the catheter. 
         [0014]    In specific embodiments, the catheter body may consists of a tube having a single lumen configured to be positioned in a peripheral vein. A proximal hub may be attached to the proximal end of the catheter body, and the needle may have a circular cross-section and the catheter body lumen may have a circular cross-section, where the needle may have an outer diameter in the range from 0.3 mm to 1.7 mm and the catheter body lumen may have a diameter in the range from 0.4 mm to 2.8 mm. The inner diameter of the catheter body lumen is typically at least 20% larger than the outer diameter of the needle. 
         [0015]    In a fourth aspect of the present invention, a method for introducing a catheter into a vein, comprises penetrating a distal end of a needle carrying a catheter into the vein in a distal direction. Blood enters a distal tip of the needle, flows proximally through a needle lumen to a flashback port on the needle, and then flows radially outwardly through the flashback port into an annular lumen in the catheter surrounding the needle. When the blood appears in a transparent or translucent region near the distal end of the catheter, the user may advance the catheter over the needle (and optionally a guidewire) until the catheter reaches a target location in the vein. 
       INCORPORATION BY REFERENCE 
       [0016]    All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: 
           [0018]      FIG. 1  is a perspective view of an intravenous catheter and a needle assembly constructed in accordance with the principles of the present invention. 
           [0019]      FIG. 2  is an exploded view of the intravenous catheter and needle assembly of  FIG. 1 . 
           [0020]      FIG. 3  is an axial cross-sectional view of the intravenous catheter and needle assembly of  FIGS. 1 and 2 . 
           [0021]      FIGS. 4A through 4B  illustrate use of an intravenous catheter and needle assembly for introducing a catheter into a vein in accordance with the principles of the methods of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    As shown in  FIGS. 1-3 , an exemplary intravenous catheter and needle assembly  10  constructed in accordance with the principles of the present invention comprises a catheter body  12  having a proximal end  14  and a distal end  16 . A proximal hub  18  is attached to the proximal end  14  of the catheter body and includes a pair of attachment wings  20  which are used to secure the catheter hub to a patient&#39;s skin in the conventional manner after the catheter has been introduced into a target vein or other blood vessel. 
         [0023]    The catheter body  12  has a central lumen  34  ( FIG. 2 ) which slidably receives an access needle  22  having a tissue-penetrating distal tip  24  which extends distally from the distal end  16  of the catheter body  12  when the assembly is ready for use. The tissue-penetrating tip will usually be a sharpened needle-type or trocar-type tip but could alternatively be a radiofrequency electrode or other energy-enhanced penetrating element. A proximal grip  26  is attached to a proximal end of the needle  22  so that a user can grip and hold the needle as a slider  28  is advanced over the needle, as will be described in more detail below. The slider  28  is attached to a proximal end of a guidewire  30  ( FIG. 2 ), and the guidewire  30  usually has a safety tip  32  at its distal end, typically being a planar coil as illustrated. The proximal hub  18  will usually have a hemostasis valve  36  in its interior where the hemostasis valve can receive the needle  22 , as best seen in  FIG. 3 . 
         [0024]    The slider  28  will be slidably mounted over the exterior of the needle  22 , as best seen in  FIG. 3 . The guidewire  30  will be present in a central passage (not shown) of the access needle, and the slider  28  is slidably mounted over a proximal portion of the needle. A link  42  attached to the slider  28  passes through a slot  38  in the proximal region of the needle so that translation of the slider  28  in a distal direction causes distal safety tip  32  of the guidewire  30  to advance axially out the distal tip  24  of the needle, as shown in broken line in  FIG. 1 , while retraction of the slider  28  in a proximal direction fully withdraws the guidewire into the needle so that the guidewire is not visible outside of the needle. 
         [0025]    When the access needle  22  is introduced into the lumen  34  of the catheter  12 , as shown in  FIG. 3 , a tapered dilator element  44  which is coaxially disposed over a distal portion of the needle sits in an open distal end of the lumen  34  of the catheter body  12 . The tapered dilator element  42  provides a tapered transition from the small diameter needle, typically having an outer diameter from 0.3 mm to 1.7 mm, usually from 0.4 mm to 1.7 mm, to the larger diameter of the catheter body  12 , typically from 0.4 mm to 2.8 mm, usually from 0.9 mm to 2.5 mm. Often, the distal end of the catheter body  12  will also be tapered to further assist in the transition, and the tapered dilator element  44  will act to fill or occupy an annular gap between the outer diameter of the needle and the inner diameter of the catheter lumen. 
         [0026]    The tapered dilator element  44  also helps to properly position the needle distal tip so that a short distal segment, typically in the range from 0.1 mm to 5 mm, preferably from 0.2 mm to 0.4 mm, extends distally beyond the distal end  16  of the catheter, as shown in  FIG. 3 . A blood perfusion port  46  is formed in the needle just proximally of the seal  44  so that the blood entering the distal tip  24  of the needle (when the needle is introduced to a vein or other blood vessel) will flow out through the port  46  and provide blood “flashback” flow to a transparent or translucent region or window  50  near the distal end of the catheter body  12 . The short distance between the needle tip and the port  46  assures that “flashback” occurs rapidly so that the user knows immediately when the needle has entered the vein. 
         [0027]    Referring now to  FIGS. 4A-4B , the needle tip  24  and distal end of catheter body  12  are manually advanced by a user so that distal tip  24  of access needle  22  is penetrated through the patient&#39;s skin S, as shown in  FIG. 4A . Once the needle tip  24  and the distal end of the catheter body  12  enter the vein V, as shown in  FIG. 4A , blood will flow through lumen  52  of the needle in a proximal direction toward flashback port  46 . Once the blood B reaches the flashback port  46 , the blood will flow radially outward into the lumen  34  of the catheter body  12 . The blood will then be visible to the user through the transparent/translucent region  50 , alerting the user the needle tip has entered the vein. 
         [0028]    Once the needle tip  24  and the distal end of the catheter body  12  are in the vein, the user may optionally advance the safety tip of guidewire  30 , allowing the needle and catheter to be further advanced into the vein while minimizing the risk of accidentally puncturing the vein wall. Once the catheter  12  is in a desired position, the needle  22  and guidewire  30  may be withdrawn ( FIG. 4B ), leaving the catheter in place for use. 
         [0029]    While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.