Patent Publication Number: US-7713256-B2

Title: System and method of delivering local anesthesia

Description:
RELATED APPLICATIONS 
     This application is a divisional application of U.S. Ser. No. 10/682,848 filed Oct. 10, 2003, which claims benefit under 35 U.S.C. §119(e) from U.S. Provisional Patent Application No. 60/417,728, filed on Oct. 10, 2002, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to systems and methods of delivering anesthesia to tissue. Specifically, the invention relates to systems and methods of providing anesthesia to tissue using a catheter and introducer needle assembly, and applying a current to the needle assembly to create stimulation in the tissue to identify a target needle depth at which to deliver the anesthesia. The present application 
     2. Description of the Related Art 
     In certain instances, it is desirable to provide anesthesia at a point in a patient&#39;s tissue proximate to a nerve. Such procedures are known as peripheral block procedures. Typically, the clinician employs a hollow needle that is coated with an electrical insulator, leaving only the tip of the needle exposed. The clinician first locates anatomical landmarks to establish the location of the nerve. As the needle is inserted into the tissue, a small electric current is passed through the needle. The current passes to the patient&#39;s tissue at the tip of the needle (the only exposed portion of the needle) and causes surrounding muscle tissue to contract or “twitch.” This twitching is observed by the clinician and helps locate the needle tip. As the needle tip proceeds closer to the nerve, the clinician reduces the current and moves the needle tip to a point that is believed to be appropriately close to the nerve to be effective. 
     Once the needle tip is in place, the clinician delivers a bolus of anesthesia through the needle to the region around the nerve. Typically, such a delivery of anesthesia will deaden both the motor and sensory impulses. After delivery of the anesthesia, the rigid needle is withdrawn. Consequently, if more anesthesia is required, another needle must be inserted. Alternatively, some practitioners will insert a catheter through the needle so that the tip of the catheter is near the tip of the needle. The needle is then withdrawn over the catheter and the catheter remains in place. After the needle is threaded off the catheter, a special connector is attached to the catheter end to permit that delivery of additional anesthesia. This can be a time consuming process. 
     SUMMARY OF THE INVENTION 
     It is an aspect of one implementation of the invention to provide a system and method for delivering anesthesia via a needle while providing a catheter for delivery of additional anesthesia over time. 
     It is an aspect of another implementation of the invention to provide a device and method adapted for delivering anesthesia to tissue via both a needle and a catheter, at the election of the clinician. 
     It is an aspect of yet another implementation of the invention to provide a system and method for locating the tip of the needle within the patient&#39;s tissue before delivering anesthesia or withdrawing the needle. 
     In accordance with one implementation of the invention, a catheter and introducer needle assembly is provided including a catheter adapter at its proximal end, which preferably includes at least one wing radially extending from the catheter adapter. The catheter adapter also includes a side port in fluid communication with the catheter. A septum is located in the proximal end of the catheter adapter proximal of the side port. Preferably, the septum prevents any fluid from flowing into or out of the proximal end of the catheter adapter and thus diverts any fluid flowing in the catheter lumen into the side port. Similarly, the septum diverts any fluid flowing from the side port into the catheter lumen. The septum has a hollow interior portion to minimize drag on the introducer needle as it is being withdrawn from the catheter through the septum. 
     The introducer needle is connected at its proximal end to a needle hub and preferably includes at least one notch, i.e., a hole or opening in the sidewall, formed therein in communication with the introducer needle lumen (or “central bore”). The notch is formed in the introducer needle such that fluid can flow between the central bore of the needle and the catheter adapter. When delivering anesthesia through the needle, anesthesia fluid is delivered through the extension tube to the side port. From the side port, the fluid enters the catheter adapter and proceeds either directly through the notch, or travels in the annular space between the needle and the catheter, and then through the notch (depending on the position of the notch along the needle). Passing through the notch, the fluid passes through the central bore and out of the tip of the needle. As shown, the notch may be positioned near the tip of the needle within the catheter. The notch can also be positioned elsewhere and still practice aspects of the invention. For example, the notch may be positioned on the needle within the catheter adapter aligned with the side port, as discussed in U.S. Pat. No. 5,935,110, incorporated herein by reference, to encourage flow through the needle. 
     It will be appreciated that this structure permits the flow of liquid through the side port to either the annular space between the needle and the catheter (or a notch that may positioned on the needle within the catheter adapter), through the notch into the lumen within the needle, and out of the tip of the needle. When the needle is removed, the catheter adapter remains in place, permitting later delivery of fluids through the catheter. Access to the side port may be through a closed system access port, thereby ensuring that an open conduit to the environment is not created. 
     In accord with certain implementations of the invention, an electrical connection may be provided to the needle via the needle hub. A hand-held, battery powered device may be connected to the electrical connection, thereby providing an appropriate charge. The needle may be made of an electrically conductive material, such as stainless steel. The catheter, however, is made of a material that acts as an electrical insulator. Therefore, only the tip of the needle carries the electrical charge to the patient&#39;s tissue. As the clinician inserts the catheter assembly into the patient&#39;s tissue, an electrical charge may be delivered through the needle to the tissue. Certain tissue will respond to the electrical charge by twitching. Specifically, muscles will contract under an electrical charge. Consequently, the clinician can use this information, along with other indicia, to determine the location of the tip of the needle during insertion. After the clinician confirms proper placement of the catheter assembly into the patient&#39;s tissue, the clinician delivers liquid anesthesia to that tissue by supplying the anesthesia to the side port of the catheter assembly. Preferably, the clinician delivers the anesthesia using a syringe attached to the extension tube. The clinician then withdraws the introducer needle from the catheter by pulling the needle hub in a proximal direction. The septum should be long enough so that both the notch and the open distal end of the introducer needle can be located simultaneously within the septum, such as described in U.S. Pat. No. 6,506,181, incorporated herein by reference. This ensures no blood or anesthesia leakage occurs when the introducer needle is being withdrawn from the catheter. If the septum is too short, the open distal end of the introducer needle could be distal of the distal end of the septum in the fluid flow path while the notch could be located proximal of the proximal end of the septum. This could allow fluid to leak from the catheter when the introducer needle is being withdrawn. 
     During infusion of the anesthetic, it is desirable that a clinician be able to aspirate though the device to assure that the needle point is not accidentally located within an artery (which anatomically is very near the target nerves). The need to aspirate is so that a clinician can determine if the device is in the venous system prior to infusing significant amounts of anesthetic, which could result in a very detrimental result if infused into the venous system. If the device accidentally penetrates an artery, during aspiration blood would be drawn through the needle point, out through the notch in the needle, and visualized in the annular space between the needle and the catheter and all fluid connection locations proximal of the notch (i.e. catheter adapter and extension tubing) if the notch is located near the distal end of the needle. If the notch is located in the catheter adapter the aspirated blood would be visualized in the clear/translucent catheter adapter and points proximal of the notch located within the catheter adapter. 
     Once the needle is withdrawn, the catheter remains in place, with the tip of the catheter disposed in the tissue being anesthetized. Over time, the clinician may determine that additional anesthesia needs to be applied. In such case, the clinician operably connects a source of anesthesia to the fluid access device on the extension tube. The fluid anesthesia passes through the extension tube, into the catheter adapter and into the catheter itself. The fluid anesthesia then passes through the catheter lumen into the patient&#39;s tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an integrated catheter and introducer needle for use in accordance with an aspect of this invention; 
         FIG. 2  is an exploded perspective view of an integrated catheter assembly of  FIG. 1 ; 
         FIG. 3  is a perspective cross-sectional view taken along line  3 - 3  in  FIG. 1  showing the catheter and introducer needle assembly having a first embodiment of the low drag septum, with a portion of the introducer needle assembly in phantom, prior to insertion into a patient; 
         FIG. 4  is a perspective cross-sectional view similar to the view of  FIG. 3  after the catheter assembly has been inserted into a patient but before the introducer needle has been completely retracted from the catheter assembly with the distal portion of the introducer needle disposed in the distal portion of the septum; 
         FIG. 5  is a perspective cross-sectional view similar to the view of  FIG. 3  after the catheter assembly has been inserted into a patient but before the introducer needle has been completely retracted from the catheter assembly with the distal portion of the introducer needle disposed in the proximal portion of the septum; 
         FIG. 6  is a perspective cross-sectional view similar to the view of  FIG. 3  after the catheter assembly has been inserted into a patient with the introducer needle completely retracted from the catheter; 
         FIG. 7  is a cross-sectional view of a portion of the integrated catheter taken along line  7 - 7  in  FIG. 1  without the introducer needle assembly; 
         FIG. 8  is a perspective cross-sectional view of the catheter and introducer needle assembly similar to  FIG. 3  but showing a different relationship between the introducer needle and the low drag septum where the distal tip of the introducer needle is distal of the distal end of the septum; 
         FIG. 9  is a perspective cross-sectional view of the catheter and introducer needle assembly similar to  FIG. 4  but showing a different relationship between the introducer needle and the low drag septum where the distal tip of the introducer needle is disposed in the distal portion of the septum; 
         FIG. 10  is a perspective cross-sectional view of the catheter and introducer needle assembly similar to  FIG. 5  but showing a different relationship between the introducer needle and the low drag septum where the distal tip of the introducer needle is disposed in the proximal portion of the septum; 
         FIG. 11  is a cross-sectional view similar to the view in  FIG. 7  of a portion of the integrated catheter having the low drag septum but showing the configuration of the second embodiment of the low drag septum disposed in the catheter; 
         FIG. 12  is a schematic cross sectional view showing the catheter assembly inserted into a patient&#39;s tissue; 
         FIGS. 13A and 13B  are top and side isolation views in partial cutaway showing  25  the needle tip and catheter tip; 
         FIG. 14  is a perspective view of an integrated catheter and introducer needle for use in accordance with another aspect of this invention; 
         FIG. 15  is an exploded perspective view of an integrated catheter assembly of  FIG. 14 ; 
         FIG. 16  is a detailed perspective view of the catheter adapter of the catheter as shown in  FIG. 14 ; 
         FIG. 17  is a cross-sectional view taken along line  17 - 17  in  FIG. 14  showing the catheter and introducer needle assembly; 
         FIG. 18  is a detailed cross-sectional view of the catheter adapter shown in  FIG. 16 ; 
         FIG. 19  is a cross-sectional view of an example of a luer lock adapter and luer lock about to engage the luer lock adapter; 
         FIG. 20  is a cross-sectional view of the luer lock engaged with the luer lock adapter shown in  FIG. 19 ; 
         FIG. 21  is a perspective view of the luer lock adapter shown in  FIG. 19 ; 
         FIG. 22  is a top view of the luer lock adapter shown in  FIG. 19 ; and 
         FIG. 23  is a perspective view of an example of the relationship between the needle assembly shown in  FIG. 1  and the needle shield assembly when the needle shield assembly is extended over the needle tip. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As used herein, the term “proximal” refers to a location with respect to the device that, during normal use, is closest to the clinician using the device and farthest from the patient in connection with whom the device is used. Conversely, the term “distal” refers to a location with respect to the device that, during normal use, is farthest from the clinician using the device and closest to the patient in connection with whom the device is used. 
     As used herein, the term “top”, “up” or “upwardly” refers to a location with respect to the device that, during normal use, is radially away from the longitudinal axis of the device and away from the patient&#39;s skin. Conversely, as used herein, the term “bottom”, “down” or “downwardly” refers to a location with respect to the device that, during normal use, is radially away from the longitudinal axis of the device and toward the patient&#39;s skin, 
     As used herein, the term “in” or “inwardly” refers to a location with respect to the device that, during normal use, is toward the inside of the device. Conversely, as used herein, the term “out” or “outwardly” refers to a location with respect to the device that, during normal use, is toward the outside of the device. 
     An integrated catheter and introducer needle assembly is shown generally at  10  in  FIG. 1 . The catheter and introducer assembly may be configured as described in U.S. patent application Ser. No. 09/865,918, incorporated herein by reference. Of course, other assemblies may be used and practice aspects of the invention, such as the assembly described in U.S. patent application Ser. No. 09/717,148, incorporated herein by reference. Specifically, the catheter and introducer assembly may include a shield  200  or other device designed to capture the tip of the needle as it is withdrawn from the assembly, as disclosed in U.S. patent application Ser. No. 09/717,148, incorporated herein by reference. Further details of a catheter and introducer assembly can be also found in U.S. patent application Ser. No. 09/590,600 and in WO 01/93940, the entire contents of both of these documents being incorporated herein by reference. 
     As shown, the catheter assembly  20  includes catheter  21  affixed to catheter adapter  24 . Suitable materials for catheter  21  include, but are not limited to, thermoplastic resins such as fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyurethane and the like. The catheter  21  is formed from a thermoplastic hydrophilic polyurethane that softens with exposure to physiological conditions present in the patient&#39;s body. Importantly, the catheter is preferably made of a material that does not occlude during use and that acts as an electric insulator. The electric insulation characteristic of the catheter material should be such that the electric charge passing through the needle, discussed below, does not pass through the catheter to the patient&#39;s tissue. In addition, the material used to form catheter  21  may be transparent or at least translucent to reduce visual interference with the clinician. The catheter material should also be selected so that it does not interact with the intended liquid anesthesia. Suitable materials for catheter adapter  24  include, but are not limited to, thermoplastic polymeric resins such as polycarbonate, polystyrene, polypropylene and the like. The material used to form catheter adapter  24  may be transparent or at least translucent to allow the clinician to view the flow of anesthesia there through. 
     Catheter adapter  24  includes a side port  22 , which has an extension tube  25  connected thereto. Extension tube  25  is preferably formed from a translucent material such as polyvinyl chloride, polyurethane and the like to facilitate visualization of the anesthesia through extension tube  25 . The proximal end  127  of extension tube  25  may include a closed-system access port, such as luer lock adaptor  126 . The closed system-access port may include the needleless luer access connector as shown in  FIGS. 19-22  and disclosed in U.S. Pat. No. 6,171,287, incorporated herein by reference, or other fluid access device to allow the connection of an anesthesia or other IV fluid supply line to extension tube  25 . Preferably, the closed system access port is designed to receive a luer lock, luer slip or other connector. The closed system access port may also be a PRN adapter. In any event, it is desirable that the port maintain a seal against the environment until accessed by a syringe tip or other device. 
     Specifically, as shown in  FIGS. 19-22 , the needleless luer access connector includes a housing  410  having a top portion  412  and bottom portion  416 . Typically plastic materials such as polycarbonate, or PETG could be used to form housing  410 . Housing  410  defines an inlet  411  and an outlet  417  with a cavity or bore  413  extending therebetween. Inlet  411  is defined at the top of top portion  412  and outlet  417  is defined at the bottom of bottom portion  416  of the needleless luer access connector. Inlet  411 , and thus that portion of bore  413  adjacent to inlet  411  and that portion of top portion  412  adjacent to inlet  411 , must be sized and configured in conformity with at least some of the International Standards Organization (ISO) standards for a female luer connection. This will allow a male luer slip or lock to be connected to inlet  411 . Thus, inlet  411  has a maximum external diameter of about 0.265 inches (6.73 millimeters) and an internal diameter of about 0.214 inches (5.44 millimeters) to allow a male luer taper to extend into inlet  411 . The exterior of the top of top portion  412  includes luer threads  414  that allow another medical device having a male luer lock to be connected to the top of proximal portion  412 . Alternatively, no luer threads  414  need be formed on the exterior of the top of top portion  412  so that another medical device having a male luer slip can be connected to the top of top portion  412 . Outlet  417 , and thus that portion of bore  413  adjacent to outlet  417  is sized and configured as a male luer taper that complies with the ISO standards for a male luer taper. ISO standard 594-2:1986(E) requires that the male luer taper have a minimum length of about 0.2953 inches (7.5 millimeters). Forming this part of housing  410  in accordance with ISO standards allows the needleless luer access connector of this invention to be connected to a standard female luer configuration of another medical device. If desired, a luer lock collar  416   a  may be formed about the male luer taper to lock the connector to a female luer. In such a case, the luer lock should comply with ISO standards. According to ISO standards, the root diameter R of the thread on the male luer lock fitting should be about 0.315 inches (8 millimeters) and the crest diameter C of the thread on the male luer lock fitting should be about 0.276 inches (7 millimeters). In addition, the male luer taper must extend a minimum of about 0.083 inches (2.1 millimeters) past the end of luer lock collar  416   a.    
     The top surface  415  of top portion  412  adjacent to inlet  411  transitions between two high points and two low points. Each high point is about 180 degrees apart from each other and each low point is also about 180 degrees apart from each other such that each high point is about 90 degrees from each low point. Preferably, each high point should be greater than zero but less than about 0.050 inches (1.143 millimeters) higher than each low point. Most preferably, each high point should be about 0.027 inches (0.686 millimeters) higher than each low point. To achieve a smooth circumferential top surface  415  that transitions in a smooth undulating fashion between high points and low points, top surface  415  can be formed by using a curved surface with a radius of about 0.30 inches (7.62 millimeters) as the template to cut the top of proximal portion  412 . In geometric terms, an imaginary cylinder defined by the top of proximal portion  412  can be cut with an imaginary cylinder having a radius of about 0.30 inches (7.62 millimeters) oriented 90 degrees to the longitudinal axis of the imaginary cylinder defined by the top of proximal portion  412 . This results in top surface  415  having the shape described. By changing the radius of the imaginary cylinder, the distance between high points and low points can be changed. 
     A septum  420  is located in top portion  412  of the needleless luer access connector to control fluid flow therethrough. Typically materials such as silicone or polyisoprene could be used for form septum  420 . Septum  420  has an enlarged proximal portion  421 , a medial portion  422  and an enlarged distal portion  423 . The top of enlarged proximal portion  421  can be formed with an annular lip  424  extending about the circumference of proximal portion  421 . Lip  424  provides extra mass to give enlarged proximal portion  421  extra rigidity to prevent it from folding in when it is accessed by a male luer taper. Lip  424  may also be bonded to the proximal portion of top portion  412 . Medial portion  422  has a cross sectional area that is smaller than the cross sectional area of proximal portion  421  and smaller than the cross sectional area of distal portion  423 . Preferably medial portion  422  has a generally oblong cross-section with a major axis M 1  substantially equal to the internal diameter of inlet  411 . Alternatively, the major axis may be slightly greater than the internal diameter of inlet  411  to help ensure that septum  420  remains in inlet  411 . The minor axis M 2  of medial portion  422  is smaller than the diameter of proximal portion  421  and smaller than the internal diameter of inlet  411 . Thus, medial portion  422  has a cross-sectional area that is smaller than the cross-sectional area of inlet  411 . This provides a space between the external surfaces of medial portion  422  along the major axis thereof and the sidewalls of housing  410  that define inlet  411  where the material of septum  420  can be displaced when a male luer taper is disposed in septum  420 . Enlarged distal portion  423  defines an annular slot  426  extending about the bottom thereof. In addition, an enlarged diametrical portion  427  extends across the bottom of enlarged distal portion  423 . 
     A slit  425  is formed in septum  420  and extends longitudinally through proximal portion  421 , medial portion  422  and distal portion  423 . As seen in the top plan view of septum  420  of  FIG. 22 , slit  425  has a transverse axis T and is defined by a pair of sides  425   a  and a pair of ends  425   b . Preferably, a diametrical portion of an enlarged distal portion extends from sides  425   a  of slit  425  along an apex back to the bottom surface of enlarged distal portion. Diametrical portion provides increased mass adjacent to the bottom of slit  425  to help keep slit  425  closed against fluid flow. 
     Septum  420  is disposed in top portion  412  of housing  410  such that enlarged proximal portion  421  rests on top of top surface  415 . As a result, enlarged proximal portion  421  projects above the top of inlet  411 . In addition, because of the undulating configuration of top surface  415 , proximal portion  421  is pushed upon along high points A. Septum  420  is aligned in housing  410  such that the middle of sides  425   a  of slit  425  are aligned with each of the high points and transverse axis T is aligned with the low points. Thus the minor axis of medial portion  422  is aligned with the high points and the major axis of medial portion  422  is aligned with the low points. Distal portion  423  is captured between top portion  412  and bottom portion  416  of housing  410  such that preferably the top wall of bottom portion  416  engages annular slot  26  of septum  420 . The bottom wall of top portion  412  is bonded to a circumferential flange  419  formed along a medial portion of bottom portion  423  adjacent to luer lock collar  416   a . If desired, an annular slot  419   a  can be formed in flange  419  and the bottom wall of top portion  412  can be inserted into annular slot  419   a . Any standard bonding technique, such as chemical adhesive or ultrasonic welding can be used to bond top portion  412  to bottom portion  416 . Preferably, medial portion  422  is held in tension when septum  420  is located in housing  410 . This tension in combination with portions of proximal portion  421  being lifted up by high points A on top surface  415  results in a compressive force being exerted against sides  425   a  to force slit  425  closed at least at the top of proximal portion  421 . 
     When a male luer taper of another medical device, such as a syringe, is pushed against the top of proximal portion  421  of septum  420 , proximal portion  421  deflects distally and laterally and allows the male luer taper to access slit  425  in septum  420 . As the male luer taper is pushed further into slit  425 , medial portion  422  also deflects distally and laterally. By having a cross-section for medial portion  422  that is smaller than the cross-section of bore  413 , space is provided inside bore  413  to allow such lateral deflection of medial portion  422 . This distal and lateral deflection of septum  420  forces slit  425  to open and allows the male luer taper to penetrate septum  420  into slit  425 . When the male luer taper is fully inserted into septum  420 , slit  425  is forced open along the entire length of septum  420  and thus allows fluid to flow through septum  420  and the needleless luer access connector. Thereafter, the male luer taper of the other medical device can be withdrawn from slit  425 . The inherent resiliency of septum  420  causes septum  420  to return to its normal unstressed state with slit  425  closed. This prevents any further fluid flow through septum  420 . 
     The catheter adapter may be selectively connected to a source of anesthesia  300  via the extension tube. Such a fluid supply line can be connected to extension tube  25  prior to insertion of assembly  10  into a patient. In such case, a stopcock or Roberts clamp is provided to prevent fluid flow through the extension tube until desired. Further, a syringe may be employed as an anesthesia source to engage the luer lock adapter  126 , allowing the clinician to deliver controlled doses of anesthesia using a syringe. Side port  22  is in fluid communication with the lumen of catheter  21  via the opening  122  so that fluid infused through extension tube  25  will pass into the patient once catheter  21  is properly positioned in the patient. 
     Catheter adapter  24  may also include a pair of wings  26  that extends radially  25  outwardly from either side of catheter adapter  24 . Wings  26  are preferably located adjacent to side port  22  below the main body portion of catheter adapter  24 . Wings  26  facilitate manipulation of catheter assembly  20  and enhance patient comfort when catheter assembly  20  is affixed to the patient. Wings  26  may include suture holes  28  to facilitate fixation of catheter assembly  20  to the patient. Alternatively, various adhesive systems may be employed to affix the catheter adapter to the patient&#39;s skin. The proximal end of catheter adapter  24  is sealed with a septum  29  to ensure that fluid does not leak out of the proximal end of catheter adapter  24 . The septum can be a single plug bonded to the catheter adapter. Alternatively, the septum  29  may be formed from two portions, a proximal portion  29   a  and a distal portion  29   b , each of which is pre-slit to facilitate locating an introducer needle  31  there through. 
     Septum distal portion  29   b  provides the primary seal preventing fluid flow past septum while septum proximal portion  29   a  provides a secondary seal. Although septum  29  could be formed from one piece, two pieces may be used because it is easier and less expensive to manufacture. In addition, forming septum  29  from two separate pieces increases the column strength and facilitates assembly into catheter adapter  1024 . Preferably, septum distal portion  29   b  and septum proximal portion  29   a  are formed from the same material and have the same hardness. Suitable materials for septum  29  include a peroxide-cured elastomer such as polyisoprene, silicone and the like where the materials have a durometer in the range of 35-45 Shore A. Preferably, a septum housing  27  having an open proximal end and an open distal end surrounds at least a portion of septum proximal portion  29   a  and septum distal portion  29   b  in an interference fit to hold septum  29  in place in position in catheter adapter  24 . Alternatively, septum  29  could be located in catheter adapter  24  without the use of housing  27 . However, housing  27  facilitates placement of septum  29  in catheter adapter  24 . 
     As shown in the Figures, housing  27  extends only along the proximal portion of septum distal portion  29   b . However, if desired, housing  27  could extend completely along the entire length of septum  29  or just along septum distal portion  29   b . With such a configuration, it is to be understood that housing  27  would be configured so it would apply the desired compressive force to septum  29  instead of catheter adapter  24  as discussed below. The open proximal and distal ends of housing  27  allow an introducer needle  31  to extend through septum  29  past housing  27 . Preferably, the proximal end of housing  27  abuts and extends over a portion of the surface area of the proximal face of septum  29 . This configuration prevents the attachment of another medical device to the proximal end of catheter adapter  24 . Instead, any such medical device that should be connected to catheter adapter  24  would be connected to the fluid access device  126  located at the proximal end of extension tube  25 . 
     Septum  29  and septum housing  27  are located in catheter adapter  24  so that at least the distal portion of septum distal portion  29   b  engages the inside of catheter adapter  24 . The external diameter of at least the distal portion of septum distal portion  29   b  is greater than the internal diameter of catheter adapter  24  at least along the portion that engages the distal portion of septum distal portion  29   b . Preferably, the external diameter of the distal portion of septum distal portion  29   b  should be at least 5% larger than the internal diameter of the relevant portion of catheter adapter  24 . With this configuration, catheter adapter  24  exerts a radial compressive force against distal portion  29   b . This compressive force helps to hold housing  27  in place and also helps to seal septum distal portion  29   b  after introducer needle  31  has been withdrawn from septum  29  so that septum distal portion  29   b  does not take a compression set about introducer needle  31 . The portion of catheter adapter  24  that engages septum distal portion  29   b  should be arranged such that the proximal end of septum  29  is adjacent to the open proximal end of catheter adapter  24  when catheter adapter  24  engages septum distal portion  28   b . Septum housing  27  and septum  29  could also be affixed inside catheter adapter  24  using an alternate technique such as by an interference fit between housing  27  and catheter adapter  24 , the use of an adhesive or by ultrasonic welding. 
     Septum  29  defines a cavity or hollow interior portion  29   c  formed between septum proximal portion  29   a  and septum distal portion  29   b . This minimizes drag on introducer needle  31  as it is being withdrawn from catheter assembly  20 . Testing of septum  29  against a standard septum shows that the average drag force for septum  29  with hollow interior portion  29   c  is about 0.15 pounds while the average drag force for a septum without a hollow interior is about 0.30 pounds. Hollow interior portion  29   c  should be sized to minimize drag but it must not be too large so that it acts as a reservoir for microbial growth therein if fluid were to become trapped therein. Hollow interior portion  29   c  could have a cylindrical configuration such as shown in  FIG. 7 . However, preferably hollow interior portion  29   c  has a configuration such as shown in  FIG. 11  where the proximal section is generally cylindrical, the medial section is tapered such that it increases in diameter in the distal direction, and the distal section is tapered such that it decreases in diameter in the distal direction. Preferably the taper should be between about 2 degrees and about 10 degrees to the horizontal plane. This configuration reduces the volume of dead space that could become a reservoir for blood when introducer needle  31  is withdrawn from catheter  21 . Thus the cross section of hollow interior portion  29   c  should closely approximate the cross section of the largest needle that would be used for introducer needle  31 . Preferably, hollow interior portion  29   c  is between about 6 and about 8 millimeters in length. If desired, hollow interior portion  29   c  could be filled with some material to prevent unwanted material from becoming trapped therein. If a lubricious material such as a silicone liquid or gel is disposed in hollow interior portion  29   c  that material could also serve to enhance the drag-reducing characteristic of septum  29 . 
     In certain implementations of the invention, the septum  29  is longer than the distance between the distal end of introducer needle  31  and the proximal end of notch  33 . This prevents fluid or blood from leaking out of catheter assembly  20  when introducer needle  31  is being withdrawn therefrom. As shown in  FIG. 8 , during withdrawal of introducer needle  31 , when the distal end of introducer needle  31  is distal of septum distal portion  29   b  and notch  33  is located in hollow interior portion  29   c  anesthesia fluid can flow into introducer needle  31  and into hollow interior portion  29   c  but anesthesia fluid or blood cannot flow out of catheter assembly  20  because of the proximal portion of septum proximal portion  29   a . As shown in  FIG. 9 , during withdrawal of introducer needle  31  when the distal end of introducer needle  31  is located in the distal portion of septum distal portion  29   b , there is no longer a fluid flow path through introducer needle  31  and thus fluid cannot escape from catheter assembly  20 . Finally, as shown in  FIG. 10 , continued withdrawal of introducer needle  31  allows the proximal portion of septum proximal portion  29   a  to wipe introducer needle  31  of any residual fluid that may be disposed thereon. 
     Alternatively, the proximal portion of septum proximal portion  29   a  and the distal portion of septum distal portion  29   b  could each be at least as long as the distance between the distal tip of introducer needle  31  and the proximal end of notch  33  formed in the sidewall of introducer needle  31 . See  FIGS. 4 and 5 . This dimension ensures that no flow path is created through introducer needle  31  between the proximal and distal sides of either septum distal portion  29   b  or septum proximal portion  29   a . This will thus minimize fluid leakage into hollow interior portion  29   c  as introducer needle  31  is removed from septum distal portion  29   b.    
     In order to minimize drag on introducer needle  31 , the distal portion of septum distal portion  29   b  and the proximal portion of septum proximal portion  29   a  should not be longer than about 3 millimeters. Preferably, the distal portion of septum distal portion  29   b  should be between about 2 and about 3 millimeters long while the proximal portion of septum proximal portion  29   a  should be between about 1 and about 2.5 millimeters long. In addition, the septum  29  and/or septum housing  27  can include needle capture and shield functionality, which could eliminate the need for a separate needle shield  200  of the type discussed above. 
     Introducer needle assembly  30  includes introducer needle  31  having a sharp distal tip  32  defined by a bevel, a central bore  130  and a proximal end connected to a needle hub  34 . The needle (excluding the very tip) may be coated with a lubricant that is an electric insulator. Leads  140  may be connected to the needle at its proximal end to allow the delivery of an electrical charge to the needle, as discussed below. The lead  140  may be, welded, crimped or soldered (or a combination of these) to the proximal end of the needle. Alternatively, the leads could be formed integrally with the needle itself, or with a collar in the needle hub in which the needle sits. Further, the leads could be attached to a collar that is within the needle hub and that grips the needle. Introducer needle  31  is preferably formed from stainless steel and has a longitudinal axis that is generally parallel to the longitudinal axis of catheter and introducer needle assembly  10 . Introducer needle  31  may be formed with notch  33 , i.e., a hole or opening in the sidewall, adjacent to the distal end to allow fluid to flow into the open distal end of introducer needle  31 , through the central bore, and then out of notch  33  into the annular space  171  between catheter  21  and introducer needle  31 . Alternatively, the notch  33  may be positioned on the needle  31  such that it is aligned with or substantially aligned with opening  122  in the insertion position (see notch  33 ′ as shown, for example, in  FIG. 3 ). In such case, fluid passing through the tube  25  will flow directly through opening  122  into the notch  33 ′, and out of the tip  32  of the needle  31 . The tip of the catheter is narrowed to sealingly engage the needle near the tip. As discussed below, the seal will direct fluid flow in the annular space through the notch, rather than out the distal end of the catheter. 
     A vented plug, which allows air but not fluid to flow there through, may be provided at the fluid access device to permit blood flow into the extension tube  25 . Needle hub  34  may be formed from the same types of materials that are used to form catheter adapter  24 . Of course, other materials could be used to form needle hub  34 . 
     As will be understood, the instant invention permits the delivery of peripheral block anesthesia via a “closed” system, that is, a system that does not create an open conduit from the environment to the patient&#39;s tissue. Such systems are desirable because they can reduce risk of infection. In the implementation of the invention depicted in the Figures, the needle is withdrawn through a septum  29  (thus maintaining system closure), and the anesthesia is introduced through the luer lock adapter  126 , which an also be a closed system device such as that disclosed in U.S. Pat. No. 6,171,287 or that depicted in  FIGS. 18-22 , referenced above. 
     To use the catheter and needle assembly  10 , the clinician first inserts the needle tip  32  into the patient&#39;s tissue. Typically, the clinician will use anatomical landmarks to determine where to insert the needle  31 . The clinician will also receive tactile feedback from the patient&#39;s tissue. For example, if the needle tip is moving adjacent to an artery, the clinician can feel the pulsing blood. Further, the clinician can detect parasthesia should the needle tip actually “hit” the nerve. To assist in locating the needle tip, the clinician can provide an electrical charge, via the leads  140 , to the needle  31 . Since the catheter  21  is made of an electrical insulating material, the charge on the needle  31  only passes to the patient&#39;s tissue at the needle tip. Consequently, the clinician can observe the response of the tissue surrounding the tip, discerning the precise location of the tip within the target tissue. 
     After confirming placement of introducer needle  31  and catheter  21  in the target tissue, the clinician can then attach a source of anesthesia  300 , such as a filled syringe, to the luer lock adapter  126  (this can also be done before insertion of the catheter and introducer needle assembly, as desired by the particular clinician). As the clinician actuates the syringe, anesthesia fluid passes through the extension tube to the catheter adapter  24 . When the notch  33  is positioned near the tip  32  of the needle  31 , the fluid passes through the annular space  171 . The seal formed between the tip of the catheter and the tip of the needle directs the fluid in the annular space through the notch  33  in the needle  31  into the central bore of the needle  31  and out the open tip of the needle  31 . When the notch  33 ′ (see  FIG. 3 ) is alternatively positioned in alignment with opening  122  of the adapted  21 , the anesthesia fluid passes directly through the notch  33 ′, into the central bore of the needle  31  and out the open tip  32  of the needle  31 . Anesthesia is thus delivered through the extension tube to the catheter adapter  26  and out the needle tip  22 . The clinician is therefore able to immediately deliver anesthesia to a precise location in the patient&#39;s tissue. 
     After this initial introduction of anesthesia, the clinician then withdraws introducer needle  31  from catheter  21  by moving needle hub  34  proximally while holding the catheter adapted  24  in place on the patient. Introducer needle assembly is removed from catheter adapter  24  and disposed of according to the facility&#39;s disposal protocol. Again, because of septum  29 , blood and liquid anesthesia will not escape from catheter adapter  24  even as the needle is removed. A needle shield  200  may be provided in the assembly. In such case, the tip of the needle  31  will be shielded upon withdrawal as shown in  FIG. 23 . Further details of the needle shield  200  can be found in U.S. patent application Ser. Nos. 09/590,600 and 09/717,148, and in WO 01/93940, referenced above. 
     As can be appreciated, during infusion of the anesthetic it is desirable that a clinician be able to aspirate though the device to assure that the needle point  32  is not accidentally located within an artery (which anatomically is very near the target nerves). The need to aspirate is so that a clinician can determine if the device is in the venous system prior to infusing significant amounts of anesthetic, which could result in a very detrimental result if infused into the venous system. If the device accidentally penetrates an artery, during aspiration blood would be drawn through the needle point  32 , out through the notch  33  in the needle  31 , and visualized in the annular space between the needle  31  and the catheter  21  and all fluid connection locations proximal of the notch  33  (i.e. catheter adapter and extension tubing) if the notch  33  is located near the distal end of the needle. If the notch  33 ′ is located in the catheter adapter  24  the aspirated blood would be visualized in the clear/translucent catheter adapter  24  and points proximal of the notch located within the catheter adapter  24 . 
     The clinician can then bend wings  26  so they match the contour of the patient&#39;s skin and suture catheter assembly  20  to the patient&#39;s skin using suture holes  28 . Alternatively, the clinician can tape catheter assembly  20  to the patient&#39;s skin, or use some other method of affixation. The catheter remains within the patient with the tip of the catheter in the tissue to be anesthetized. The clinician can deliver additional anesthesia to the tissue by delivering anesthesia to the luer lock adapter  126  as discussed above. 
     Another implementation of an aspect of the present invention is shown in  FIGS. 14-18 . Similar to introducer needle assembly  10  discussed above, the introducer needle assembly  300  comprises a needle assembly  302  and a catheter assembly  304 . Needle assembly  302  includes a needle handle  306  having an opening  307  that mates with a bayonet mounting pin  321  on the catheter assembly  304 . A needle  308  having a notch  310  and open needle tip  311 , and constructed similar to needle  31  discussed above, is mounted in the needle handle  306  by, for example, adhesive or any other suitable mounting material or technique. Alternatively, the notch  310  can be configured as notch  310 ′ shown in  FIG. 18  to be positioned at a more proximal location along needle  308  to function in a manner similar to notch  33 ′ discussed above. The needle handle  306  has a rear opening which is capable of receiving an electrical connector assembly  314  that can removably attach to the back of the needle  308 . The connector  314  is coupled to a conduit  316  that is further coupled to another connector  318  having an opening that enables the connector  318  to couple to a connector of a power supply (not shown) to deliver current to the needle  308  in a manner similar to that discussed above. 
     The needle  308  is received into the catheter assembly  304  which includes a catheter  322  into which the needle passes  308 , so that an annular space  323  similar to annular space  171  discussed above is formed between the needle  308  and catheter  322 . Catheter assembly  304  further includes a side port  330  having an opening  331  configured similar to opening  122  discussed above. The side port  330  is connected to conduit  326  that is further connected to an adapter  324  having an opening  328  therein. Adapted  324  can include a closed-system access port, such as the needleless luer access connector disclosed in U.S. Pat. No. 6,171,287 referenced above and shown in  FIGS. 19-22 . Catheter assembly also includes a septum  332  and septum housing  334  similar to septum  29  and septum housing  27 , respectively, as discussed above. Catheter assembly  304  further includes bayonet mounting pin  321  that is received and mates with opening  307  in needle handle  306  to removably secure needle handle  306  to catheter assembly  304 . Specifically, the bayonet pin  321  enters the opening  307  and becomes snap fit with the catheter adapted  324  by twisting the catheter adapter  324  and needle handle  306  relative to each other about their respective axes, thus securing the catheter adapter  324  to the needle handle  306  so that they do not separate as the clinician is searching for the nerve. That is, in the process of finding the right nerve the clinician may withdraw the needle/catheter multiple times which could cause the catheter adapter  324  to separate from the needle handle  306  allowing the tip of the catheter  322  to extend beyond the needle tip  311 . The bayonet pin and slot arrangement secures the two together until the clinician disconnects the two by twisting the bayonet mounting pin  321  past a snap in the needle handle  306  allowing it to come out the slot in the distal end of the handle  306 . 
     The needle  308 , catheter assembly  304 , catheter  322  and related components are made of materials similar to those discussed above. The introducer needle assembly  300  can thus be used to deliver anesthesia in a manner similar to introducer needle assembly  10  as discussed above. 
     Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. For example, while certain aspects of the current invention are depicted in the context of a side ported catheter adapter, it will be appreciated that other ports of catheter adapters and hubs may be employed in conjunction with aspects of the invention. For example, a closed system access port may be used to serve as the septum. The needle would then pass through the access port until removed. Once removed, a luer tip syringe can then access the access port.