Patent Publication Number: US-2005137527-A1

Title: Graduated sheath and dilator assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/531,948, filed 23 Dec. 2003. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to a dilator and sheath assembly that is used during the insertion of a catheter into a patient&#39;s blood vessel.  
     BACKGROUND OF THE INVENTION  
      Catheters are often used for the delivery and withdrawal of fluids to and from a blood vessel in a patient, respectively. The fluids may be medication that is administered to the patient, or blood that is withdrawn from the patient.  
      Typically, to insert a catheter into a blood vessel, the blood vessel is located by known methods. An aspirating needle is inserted into the vessel to confirm placement within the vessel. A guide wire is then inserted through a proximal end of the aspirating needle and into the vessel. The aspirating needle is withdrawn by sliding the needle proximally over the guide wire, leaving the guide wire within the vessel. If a catheter with a sufficiently hard wall is being used, the catheter may be slid over the guide wire, directly into the vessel.  
      However, for some catheters, particularly soft walled catheters, a dilator is required to dilate the vessel at the insertion point in order to accommodate the insertion of the catheter. The dilator is typically inserted into a sheath and initially used as a dilator and sheath assembly. The assembly is inserted into the vessel over the guide wire and the dilator is used to dilate the insertion opening in the vessel wall. After the insertion opening is dilated, the dilator and the guide wire are removed from the vessel by removing both the dilator and the guide wire proximally from the sheath. The sheath remains in the vessel to accommodate insertion of the catheter through the sheath and into the blood vessel. After the catheter is inserted into the blood vessel, the sheath is torn from around the catheter and removed from the vessel.  
      However, once distal ends of the dilator and sheath assembly are inserted through the patient&#39;s skin and into the vessel, it is impossible to tell exactly how far the dilator has been inserted, running the risk of the inserting physician inserting the dilator too far and damaging the vessel walls. It would be beneficial to provide an ability for the inserting physician to determine exactly how far the dilator has been inserted into the patient.  
     BRIEF SUMMARY OF THE INVENTION  
      Briefly, the present invention provides a sheath and a dilator assembly. The assembly comprises a sheath having a proximal sheath end, a distal sheath end, and a generally tubular sheath body extending between the proximal sheath end and the distal sheath end. The sheath body includes sheath indicator indicia extending from the distal sheath end toward the proximal sheath end. The assembly also includes a dilator disposed within the sheath. The dilator includes a proximal dilator end extending proximally of the proximal sheath end, a distal dilator end extending distally of the distal sheath end, and a dilator body extending between the proximal dilator end and the distal dilator end. The dilator body includes dilator indicator indicia extending from the distal dilator etid toward the proximal dilator end, such that the sheath indicator indicia and the dilator indicator indicia display predetermined dimensions from the distal dilator end toward the proximal dilator end.  
      Additionally, the present invention also provides sheath and dilator assembly comprising a sheath having a proximal sheath end, a distal sheath end, and a generally tubular sheath body extending between the proximal sheath end and the distal sheath end. The sheath body includes sheath indicator indicia extending from the distal sheath end toward the proximal sheath end. A first connecting means is disposed at the proximal sheath end. A dilator is disposed within the tubular sheath body. The dilator includes a proximal dilator end extending proximally of the proximal sheath end, a distal dilator end extending distally of the distal sheath end, and a dilator body extending between the proximal dilator end and the distal dilator end. The dilator body includes dilator indicator indicia extending from the distal dilator end toward the proximal dilator end, such that the sheath indicator indicia and the dilator indicator indicia display predetermined dimensions from the distal dilator end toward the proximal sheath end. A second connecting means is disposed at the proximal dilator end. The first and second connecting means are releasably engageable with each other to releasably secure the dilator within the sheath.  
      The present invention also provides a method of inserting a sheath and dilator assembly into a patient&#39;s blood vessel. The sheath and dilator assembly comprise a sheath having a proximal sheath end, a distal sheath end, and a generally tubular sheath body extending between the proximal sheath end and the distal sheath end. The sheath body includes sheath indicator indicia extending from the distal sheath end toward the proximal sheath end. The assembly also includes a dilator disposed within the sheath. The dilator includes a proximal dilator end extending proximally of the proximal sheath end, a distal dilator end extending distally of the distal sheath end, and a dilator body extending between the proximal dilator end and the distal dilator end. The dilator body includes dilator indicator indicia extending from the distal dilator end toward the proximal dilator end, such that the sheath indicator indicia and the dilator indicator indicia display predetermined dimensions from the distal dilator end toward the proximal dilator end. The method furher includes inserting the distal dilator end and the distal sheath end into the blood vessel a distance determined by the sheath indicator indicia and the dilator indicator indicia. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. In the drawings:  
       FIG. 1  is a top plan view of a dilator and sheath assembly according to a preferred embodiment of the present invention.  
       FIG. 2  is an exploded top plan view of the dilator and sheath assembly of  FIG. 1 .  
       FIG. 3  shows a partially cutaway view of the dilator and sheath assembly being inserted into a patient&#39;s blood vessel. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      In the drawings, like numerals indicate like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. The words “proximal” and “distal” refer to directions away from and closer to, respectively, the insertion tip of the dilator in the dilator and sheath assembly according to the present invention. The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import. The following describes a preferred embodiment of the invention. However, it should be understood based on this disclosure, that the invention is not limited by the preferred embodiment described herein.  
      Referring now to  FIGS. 1 and 2 , a dilator and sheath assembly  100  according to the present invention is shown. The assembly  100  includes a dilator  110  that is disposable within a sheath  130 . The dilator  110  includes a hollow elongated body  112  that has a tapered distal tip  114  and a connector  116  at a proximal end  118 . Preferably, the connector  116  is a luer connector, or some other suitable connector. The connector  116  preferably includes male threads  117  to engage mating female threads on a medical device (not shown) that may be releasably connected to the connector  116 . The connector  116  preferably includes locking threads  120  at a distal end of the connector  116 .  
      A hollow passage  121  extends through the body  112  between the distal tip  114  and the proximal end  118 . The hollow passage  121  is sufficiently sized to allow the dilator  110  to be inserted over a guide wire (not shown) such that the guide wire passes through the hollow passage  121 .  
      A distal end  122  of the dilator  110  includes indicator indicia  124  that extend toward the proximal end  118  of the dilator  110 . Preferably, the indicator indicia  124  include markings to indicate distance from the distal tip  114 . The distance may be in centimeters or other predetermined distances. Also preferably, the indicator indicia  124  include numerical references to further indicate distance. The indicator indicia  124  may extend entirely around an outer circumference of the body  112 , or the indicator indicia  124  may only extend partially around the outer circumference of the body  112 .  
      The sheath  130  includes a hollow elongated body  132  that has a tapered distal tip  134  and a handle  136  at a proximal end  138 . Preferably, the handle  136  includes mating female threads  139  disposed to releasably engage the locking threads  120  on the dilator  110  when the dilator  110  is inserted into the sheath  130 . The female threads  139  and the locking threads  120  provide for a releasable connection between the dilator  110  and the sheath  130  after the dilator  110  is inserted into the sheath  130 . The dilator  110  can then be rotated approximately 90 degrees so that the locking threads  120  are releasably engaged with the female threads  139 .  
      A distal end  142  of the sheath  130  includes indicator indicia  144  that extend toward the proximal end  138  of the sheath  130 . Preferably, the indicator indicia  144  include markings to indicate distance from the distal tip  14  of the dilator  110  when the dilator  110  is fully inserted into the sheath  130 . The distance is preferably in the same units as the distance on the dilator  110  as described above. Also preferably, the indicator indicia  144  include numerical references to further indicate distance. The indicator indicia  144  may extend entirely around an outer circumference of the body  132 , or the indicator indicia  144  may only extend partially around the outer circumference of the body  132 .  
      Preferably, the dilator  110  and the sheath  130  are constructed from a radiopaque polymer such as polypropylene, polyethylene, TEFLON®, or other suitable biocompatible, with BaSO 4  or other suitable material added for radiopacity. The indicator indicia  124 ,  144  may be radiopaque or non-radiopaque. Alternatively, the dilator  110  and the sheath  130  may be constructed from a virgin, non-radiopaque polymer such as polypropylene, polyethylene, TEFLON®, with the indicator indicia  124 ,  144  being radiopaque.  
      Initially, the dilator  110  is preferably fuilly inserted into the sheath  130  as seen in  FIG. 1 . The distal tip  134  of the sheath  130  tapers such that the dilator body  112  at the distal tip  134  of the sheath  130  frictionally engages the distal tip  134  of the sheath  130 . The taper of the distal tip  134  of the sheath  130  provides a smooth transition between the dilator  110  and the sheath  130 . The locking threads  120  are engaged with the female threads  139 , securely retaining the dilator  110  within the sheath  130 .  
      Referring now to  FIG. 3 , to use the dilator and sheath assembly  100  during insertion of a catheter (not shown) in a patient  50 , an inserting physician locates an incision point according to known techniques and makes an appropriate incision  52  in the patient  50 . An aspirating needle with syringe (not shown) is inserted into the incision  52  and an appropriate blood vessel  54 , such as the internal jugular vein, is located according to known techniques. The syringe is removed and a distal end  62  of a guide wire  60  is inserted through the needle and into the vessel  54 . The needle is then removed, leaving the guide wire  60  in place.  
      The physician inserts a proximal end  64  of the guide wire  60  that is exposed into the hollow passage  121  of the dilator  110  and slides the dilator and sheath assembly  100  over the guide wire  60  so that the distal tip  114  of the dilator  110  enters the incision  52 . The physician continues to insert the dilator  110  and subsequently, the sheath  130 , into the incision  52 , while watching the indicator indicia  124 ,  144  on the dilator  110  and sheath  130 . By way of example only, the indicator indicia  124 ,  144  shown in  FIG. 3  represent one centimeter spacings between adjacent indicia  124 ,  144 . When the physician has determined that the dilator and sheath assembly  100  has been sufficiently inserted into the patient  50 , as indicated by the indicator indicia  124 ,  144 , the physician stops inserting the dilator and sheath assembly  100  into the patient  50 . As shown in  FIG. 3 , the dilator and sheath assembly  100  has been inserted approximately 10 centimeters into the patient  50 . At this point, the guide wire  60  may be removed from the patient by grasping the proximal end  64  of the guide wire  60  and pulling the guide wire  60  from the vessel  52 .  
      The physician then rotates the dilator  110  approximately 90 degrees relative to the sheath  130  to unlock the locking threads  120  from the female threads  139 . The dilator  110  is then pulled from the proximal end  138  of the sheath  130  and removed. A catheter (not shown) is then inserted into the incision  52  through the sheath  130  according to known methods. After the catheter is fully inserted, the physician grasps the handle  136  of the sheath  130  and tears the sheath  130 , while pulling the sheath  130  from the patient  50 .  
      An example of a dilator and sheath assembly  100  that may be used with the present invention is disclosed in U.S. Pat. No. 6,796,991 (“the &#39;991 patent”), which issued on Sep. 28, 2004, and is owned by the assignee of the present invention and is incorporated herein as though fully set forth.  
      It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.