Abstract:
A device is disclosed that allows a puncture needle to be inserted into a catheter. Once the puncture needle has performed its function, it can shoot back into the device such that there is a reduce likelihood of needlestick injury. Vacuum is used to assist in the shoot back function.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to cannula or catheter introducer devices and has particular relevance to such devices with retractable needles.  
       BACKGROUND ART  
       [0002]     Catheter insertion devices are well known in the art. When a catheter is inserted into a patient for the intravenous delivery of a fluid, a disposable needle passing through the catheter cannula is utilized to make a puncture to permit entry of the tip of the cannula into the patient. The needle is then withdrawn leaving the catheter in place either for a direct hook-up to a bottle of fluid to be delivered, or to be capped for later use. The needle which is now contaminated with blood or other body fluid must be disposed of without creating a risk of needle sticks to medical personnel which are engaged in the operation of inserting a catheter. A danger to clean up and medical waste disposal personnel continues if the used needles are not rendered harmless in some way. Caps or covers that can be mounted over the needle are not a satisfactory solution because they must be put in place and can become loose and expose the used needle.  
         [0003]     A discussion of the problems associated with various approaches and uses of cannula insertion products is found in Kulli, U.S. Pat. No. 4,747,831.  
         [0004]     Retractable needles have been recognized as the best solution to these problems.  
         [0005]     A number of these approaches are disclosed in U.S. Pat. No. 4,747,831 mentioned above which includes an external latch mechanism which is pushed to release a spring loaded needle which is withdrawn into the chamber of the device. Some embodiments have a sliding block and retractable fingers which depress springloaded ears to allow retraction of the needle holder, racheting devices which unlatch the needle holder by rotation of parts and even frangible parts which are broken when a plunger is pushed forward.  
         [0006]     Dysarz, U.S. Pat. No. 5,129,884, is another example of an external latch which may be disengaged to allow a needle holder to withdraw a needle into the main body of the device. Walter, U.S. Pat. No. 4,828,548, discloses a holder having a piston which may be operated on by vacuum to withdraw a needle. Erskine, U.S. Pat. No. 5,501,675, is a more recent version of a latch-operated device wherein a needle holding part may be released with an external latch.  
         [0007]     The devices of the prior art have complicated parts which are difficult to manufacture and especially difficult to assemble in a high speed manufacturing operation. Many of them are prone to premature firing during handling and with some, it is difficult to know when the needle is safe. Disengagement of the catheter assembly from the retraction device is not fully under the timing and control of the medical operator because retraction results in immediate separation of the device form the cannula assembly.  
         [0008]     It is an object of the present invention to provide a simplified cannula/catheter introducer which is safe to use and can be produced at a modest cost and which uses a vacuum to retract a contaminated needle to reduce needle stick injury.  
         [0009]     Further objects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.  
       DISCLOSURE OF INVENTION  
       [0010]     In one form, the invention resides in a cannula/catheter introducer comprising an outer tubular member which has a proximal end and a distal end, 
        an inner tubular member adapted for sliding movement within the outer tubular member, the inner tubular member having an open proximal end, and a closed distal end,     an end member which closes the open proximal end of the inner tubular member,     a sealing means on the end member to sealingly engage with the inner tubular member,     release means on the end member and which is movable between a first position where the release means locks the end member to the inner tubular member, and a second position where the release means is unlocked from the inner tubular member and allows the end member to retract through the inner tubular member, the inner tubular member being under vacuum, the vacuum functioning to retract the end member from the proximal end of the inner tubular member towards the distal end of the inner tubular member, the release means being movable from the first position to the second position upon movement of the inner tubular member towards the proximal end of the outer tubular member,     a needle holder which is attached to the proximal end of the outer tubular member, release means on the needle holder and which is moveable between a first position where the release means locks the needle holder to the outer tubular member, and a second position where the release means is unlocked from the inner tubular member,     wherein, upon movement of the inner tubular member towards the proximal end of the outer tubular member, the release means on the end member unlocks from the inner tubular member, and locks against the release means on the needle holder, and causes the release means on the needle holder to move to the unlocked position, after which the end member and the needle holder is retracted into the inner tubular member by virtue of the vacuum in the inner tubular member.        
 
         [0017]     In another form, the invention resides in a cannula/catheter introducer comprising an outer tubular member which has a proximal end and a distal end, 
        an inner tubular member adapted for sliding movement within the outer tubular member, the inner tubular member having an open proximal end and a closed distal end,     an end member which closes the open proximal end of the inner tubular member,     a sealing means on the end member to sealingly engage with the inner tubular member,     release means on the end member and which is movable between a first position where the release means locks the end member to the inner tubular member, and a second position where the release means is unlocked from the inner tubular member and allows the end member to retract through the inner tubular member, the inner tubular member being under vacuum, the vacuum functioning to retract the end member from the proximal end of the inner tubular member towards the distal end of the inner tubular member, the release means being movable from the first position to the second position upon movement of the inner tubular member towards the proximal end of the outer tubular member,     a needle holder which is attached to the proximal end of the outer tubular member, release means on the needle holder and which is moveable between a first position where the release means locks the needle holder to the outer tubular member, and a second position where the release means is unlocked from the inner tubular member,     the inner tubular member being movable between a retracted position and an extended position, and when in the retracted position, the tubular member is spaced from the needle holder by a short distance, and when in the extended position, the tubular member triggers retraction of the needle holder, the inner tubular member being held captive within the outer tubular member in the retracted position,     wherein upon movement of the inner tubular member towards the proximal end of the outer tubular member, the release means on the end member unlocks from the inner tubular member, and locks against the release means on the needle holder and causes the release means on the needle holder to move to the unlocked position, after which the end member and the needle holder is retracted into the inner tubular member by virtue of the vacuum in the inner tubular member.        
 
         [0025]     In this form of the invention, because the device functions to insert a puncture needle into a catheter or cannula, the device does not function as a syringe. Therefore, the inner tubular member in the initial position is substantially entirely within the outer tubular member and is only a short distance away from the needle holder. For instance, it is envisaged that the inner tubular member can be spaced between 1-20 millimetres from the needle holder, and preferably between 3-10 millimetres. As it is not desirable for the inner tubular member to be retracted too far in the outer tubular member (as the device does not function as a syringe), some form of locking arrangement can be provided to ensure that the inner tubular member can move only by a short distance between the retracted position and the forward (triggering) position.  
         [0026]     The introducer can be of any suitable shape and size which will depend, inter alia, on the size of the cannula or catheter. It is envisaged that the introducer will be made of suitable material such as plastic although some components (e.g. the sealing means) may be made of rubber or composite materials. However, no particular limitation is to be placed on the invention merely by the material from which the device is manufactured. The size of the introducer can vary, and it is envisaged that the length will be between 50-300 millimetres and typically between 100-200 millimetres. Again, no particular limitation should be placed on the invention merely by the size of the device. The introducer may have a diameter of between 5-50 millimetres and typically between 10-20 millimetres although no particular limitation should be placed on the invention merely by the diameter of the introducer.  
         [0027]     The outer tubular member may comprise finger grippable portions to assist in a one-handed operation in depressing the inner tubular member within the outer tubular member. The finger grippable portions may comprise extending members adjacent the proximal end of the outer tubular member and dimensioned to enable fingers to grip these portions.  
         [0028]     The proximal end of the outer tubular portion may be restricted in diameter with respect to the remainder of the outer tubular portion. Suitably, the proximal end contains a number of stepped portions to progressively reduce the diameter of the proximal end while still providing internal land portions.  
         [0029]     The end of the proximal end of the outer tubular portion may comprise a nozzle adapted for insertion into the rear of a catheter.  
         [0030]     Gripping means or locking means may be provided on an inner face at the proximal end of the outer tubular member to assist in gripping or locking the needle holder. The gripping means or locking means may comprise a recess such as an annular groove.  
         [0031]     The distal end of the outer tubular member may be provided with a locking means to restrict movement of the inner tubular member relative to the outer tubular member. Suitably, the locking means comprises an enlargement on the outer tubular member and adjacent the distal end, the enlargement defining a small travelling passageway which defines the limits of movement of the inner tubular member relative to the outer tubular member. The passageway may have a length of between 3-20 millimetres and typically between 3-10 millimetres. The passageway may contain engagement means to “lightly” engage with the inner tubular member. The engagement means may comprise a pair of spaced apart small ribs, which may be annular in configuration. The function of the engagement means may be to lightly hold the inner tubular member in the retracted position such that the inner tubular member does not inadvertently move to the extended position thereby triggering the shoot-back mechanism prematurely. However, the engagement means should be such that a person can press on the back of the inner tubular member to overcome the engagement means when desired.  
         [0032]     The inner tubular member, in use, will have reduced pressure, or be under vacuum. The inner tubular member will typically have a closed distal end and an open proximal end, with the open proximal end being closed by the end member. Typically, the inner tubular member will comprise a hollow tube with an open front end. The distal end of the inner tubular member will typically be provided with locking means to lock against the distal end of the outer tubular member in such a manner that the degree of sliding movement of the inner tubular member within the outer tubular member is predetermined. The locking means may comprise a projection which may be an annular rib that sits within the passageway that may be provided on the distal end of the outer tubular member.  
         [0033]     The end member closes the otherwise open proximal end of the inner tubular member. The end member may comprise a rear portion and a front portion. The rear portion may be substantially closed and may be provided with the sealing means to enable the end member to be sealingly engaged to the inner wall of the inner tubular member in a sliding but sealing manner. The sealing means may comprise a sealing ring that is fitted about the rear portion and which comprises at least one, and preferably a plurality of, spaced-apart ring members that sealingly engage against the inside wall of the inner tubular member.  
         [0034]     The front portion may contain or comprise the release means. The release means may be formed integrally with the rear portion. The release means may comprise at least one finger member. The finger member may be resiliently formed to move between a natural first position and a deformed second position. Suitably, the finger member deforms inwardly between the first position and the second position. Suitably, a plurality of finger members is provided and these may be spaced equally about the end member. The or each finger member may extend forwardly from the end member and towards the needle holder.  
         [0035]     The end member may have a length of between 5-20 millimetres although this can vary to suit.  
         [0036]     A “flash” chamber may be provided in the end member to enable the first flash of blood or body fluid to be viewed as the puncture needle penetrates into a patient&#39;s vein, etc.  
         [0037]     The or each finger member in the natural first position may lock against the inner tubular member and preferably lock against the open proximal wall of the inner tubular member. It is preferred that the or each finger member is profiled to facilitate this type of locking. Therefore, it is preferred that the or each finger member contains a step, or a shoulder, or have an arrowhead-type configuration to enable the or each finger member to abut against or lock against the open proximal wall of the inner tubular member.  
         [0038]     The needle holder is attached to the proximal end of the outer tubular member and is preferably positioned in the stepped or narrowing position of the outer tubular member. The needle holder may be made of any suitable material such as plastic, rubber, composite materials and the like. The needle holder will typically comprise a central body portion. The central body portion may contain a small passageway through which a puncture needle can be fitted to fit the puncture needle to the needle holder. The release means may be formed integrally with the remainder of the needle holder. The release means may comprise at least one finger member. The at least one finger member may be movable or deformable between a natural position which is the first position and a deformed position which is the second unlocking position. The at least one finger member may be cantilevered from the central body portion and may extend towards the inner tubular member. Suitably, a plurality of finger members is provided and these may be spaced equally about the central body portion. Each finger member may be provided with a terminal configuration which may comprise a shoulder, a step portion, a hook portion, or an arrowhead portion, the function of which is to facilitate engagement with the finger member on the end member as will be described in greater detail below. Also, each finger member may comprise an intermediate projection such as an annular ring which engages into the recess on the outer tubular member to temporarily lock the needle holder to the outer tubular member.  
         [0039]     In another form, the invention resides in a cannula/catheter inserter, the inserter comprising 
        an outer tubular member which has a proximal end and a distal end,     an inner tubular member adapted for sliding movement within the outer tubular member, the inner tubular member having an open proximal end, and a closed distal end,     a needle holding piston assembly which closes the open proximal end of the inner tubular member,     a sealing means on the needle holding piston assembly to sealingly engage with the inner tubular member,     release means on the needle holding piston assembly and which is movable between a first position where the release means locks the needle holding piston assembly to the inner tubular member and a second position where the release means is unlocked from the inner tubular member and allows the needle holding piston assembly to retract through the inner tubular member, the inner tubular member being under vacuum, the vacuum functioning to retract the needle holding piston assembly from the proximal end of the inner tubular member towards the distal end of the inner tubular member, the release means being movable from the first position to the second position upon movement of the inner tubular member towards the proximal end of the outer tubular member,     wherein upon movement of the inner tubular member towards the proximal end of the outer tubular member, the release means on the needle holding piston assembly unlocks from the inner tubular member, after which the needle holding piston assembly is retracted into the inner tubular member by virtue of the vacuum in the inner tubular member.        
 
         [0046]     It is preferred that the inner tubular member is movable between a retracted position and an extended position and when in the retracted position, the tubular member is spaced from the needle holding piston assembly by a short distance and when in the extended position, the tubular member triggers retraction of the needle holding piston assembly, the inner tubular member being held captive within the outer tubular member such that the inner tubular member can only move by the short distance.  
         [0047]     The short distance may be as described above and will of course depend on the size of the device. However, it is the intention that the inner tubular member can move forward by only a short distance to trigger the shoot back mechanism. Typically, this distance will be between 1-20 millimetres and preferably between 3-10 millimetres.  
         [0048]     Suitably, the inner tubular member and the outer tubular member are substantially as described above with reference to the first embodiment of the invention.  
         [0049]     The needle holding piston assembly may have a length of between 5-30 millimetres although no particular limitation should be placed on the invention merely by this length. The piston assembly may comprise a main body which has one closed end and one open end and is substantially hollow. The closed end may be provided with an enlargement onto which the sealing member can be positioned. The sealing member may comprise any suitable type of sealing member. The open end may contain a needle mounting block. The needle mounting block typically contains a small passageway through which the puncture needle can pass to fit the puncture needle to the needle mounting block. A small flash chamber may be provided in the main body. The needle mounting block will typically contain the release means. The release means may comprise at least one finger member. Suitably, a plurality of finger members is provided. Each finger member may contain a terminal configuration, which may comprise a step, a shoulder, a hook, or an arrowhead type configuration to facilitate locking of the finger member and therefore locking of the needle holding piston to the proximal end of the inner tubular member.  
         [0050]     In another form of the invention, there is provided a cannula/catheter introducer comprising: 
        (a) a cannula and catheter connector assembly,     (b) a retractable needle assembly for assembly with the cannula and catheter assembly, and     (c) a valving member connected with the cannula and catheter assembly for controlling in ingress and egress of fluids from a patient.        
 
         [0054]     The cannula and catheter connector assembly may be provided with an inlet tube for releasable assembly with an outlet tube of a retractable needle.  
         [0055]     The valving member will typically be manually adjustable from a first sealing position to a second flow position.  
         [0056]     The valving member may comprise a plunger type valve.  
         [0057]     Alternatively, the valving member may comprise a turn type valve.  
         [0058]     The retractable needle may be of the type described above, and therefore may comprise an outer and inner casing, an outlet from the casing, an internal piston within the inner casing mounting a needle and a sealed compartment between the piston and a closed end of the inner casing.  
         [0059]     The sealed compartment contains partial pressure.  
         [0060]     The outer casing is typically provided with wings for gripping.  
         [0061]     The piston may include a transparent vial section which enables a user to establish that the needle has been correctly inserted.  
         [0062]     The vial may comprise a minute venting aperture.  
         [0063]     With the present invention, the assembled catheter introducer is handled as a unit. When the operator verifies that the needle is properly inserted, one hand can hold the connector that remains attached to the patient while the other hand separates the retraction body which upon separation is automatically retracted. A portion of the hand rests against the cannula to prevent blood flow until the other hand inserts the conventional tube into the catheter connector to start the infusion of fluid. Immediately after separation, the retraction body safely contains the retracted needle and the removed part is safely discarded. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0064]     Embodiment of the invention will be described with reference to the following illustrations.  
         [0065]      FIG. 1  illustrates a section view of an introducer fitted to a catheter and according to a second embodiment of the invention, and in the “use” position.  
         [0066]      FIG. 1   a  illustrates a close-up view of the proximal part of the introducer and particularly illustrating the needle holding piston.  
         [0067]      FIG. 1   b  illustrates a close-up view of the distal part of the introducer and particularly illustrates the mechanism that limits travel of the inner tubular member in the outer tubular member.  
         [0068]      FIGS. 2 and 2   a  illustrate initiation of the “shoot back” mechanism where the inner tubular member is being pushed forwardly in the outer tubular member to deform the needle mounting block.  
         [0069]      FIGS. 3 and 3   a  illustrate the needle in the shoot back position.  
         [0070]      FIG. 4  illustrates the introducer removed from the catheter with the puncture needle safely within the confines of the inner tubular member.  
         [0071]      FIGS. 5 and 6  illustrate section views of the catheter.  
         [0072]      FIG. 7  illustrates a perspective view of the introducer connected to the catheter.  
         [0073]      FIG. 8  illustrates a section view of a first embodiment of the invention with the introducer attached to a catheter and in the “use” position.  
         [0074]      FIG. 8   a  illustrates a close-up of the proximal end of the introducer.  
         [0075]      FIG. 8   b  illustrates a close-up of the distal end of the introducer.  
         [0076]      FIGS. 9 and 9   a  illustrate the introducer being moved to trigger the shoot back mechanism.  
         [0077]      FIGS. 9   b  and  10  illustrate the shoot back position where the puncture needle is safely within the confines of the inner tubular member.  
         [0078]      FIG. 11  illustrates the introducer removed from the catheter.  
         [0079]      FIGS. 12-15  illustrate the valve on the catheter.  
         [0080]      FIG. 16  illustrates a perspective view of the second embodiment of the introducer attached to the catheter. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0081]     Referring to  FIGS. 8-16 , there is illustrated a first embodiment of the invention. Briefly,  FIGS. 8-9   a  illustrate a cannula/catheter introducer in the “use” position, while  FIGS. 9   a - 11  illustrate the same introducer in the “shoot back” position.  FIGS. 12-15  illustrate the valve which forms part of the catheter assembly and  FIG. 16  is a perspective view of the device attached to the catheter.  
         [0082]     Referring initially to  FIG. 16 , there is illustrated a catheter introducer  10  which comprises an outer tube  11 . Outer tube  11  contains a pair of finger gripping wings  12 . The front of outer tube  11  contains a number of step portions  13  to ultimately finish in an inlet  14 .  
         [0083]     A catheter assembly  15  can be attached to inlet  14  and assembly  15  includes a valve  16  to enable the flow from the catheter needle  17  to be regulated.  FIGS. 12-15  illustrate particularly valve  16 .  FIG. 12  is a section view showing the valve in the “off” position and  FIG. 13  is a plan view showing the valve in the “off” position.  FIGS. 14-15  illustrate similar views with the valve in the “on” position. The valve can be moved manually between the “on” position and the “off” position.  
         [0084]     Referring now in greater detail to  FIGS. 8, 8   a  and  8   b , there is illustrated details of the device  10 . Briefly, the device functions to enable a contaminated needle  18  to be “sucked” back into the main body of the device after use thereby preventing needle stick injury. Briefly, this is achieved by pushing the inner tube  19  forwardly relative to outer tube  11  by distance of only a few millimetres but this movement is sufficient to suck back a contaminated needle. This will now be described in greater detail.  
         [0085]     Referring to  FIGS. 8, 8   a  and  8   b , there is illustrated the device  10  attached to a catheter assembly  15 . Device  10  has an outer tube  11  and an inner tube  19  with the inner tube  19  able to slide within outer tube  11  by a short distance (typically a few millimetres). Outer tube  11  is cylindrical and can have a length of between 10-20 centimetres and a diameter of between 5-20 millimetres although no particular limitation should be placed on the invention merely by these dimensions. Outer tube  11  will typically be made of suitable plastic material. Outer tube  11  has a rear (distal) open end  20  to enable the inner tube  19  to be manipulated. The open end  20  contains an enlarged collar  21  which is best illustrated in  FIG. 8   b  and which defines a small travelling passageway  22  of a few millimetres.  
         [0086]     Inner tube  19  is under vacuum and has a closed rear (distal) end  23 . This distal end is formed with an annular rib  24  which is designed to move along passageway  22 . The annular rib  24  enables inner tube  19  to be moved forwardly (or be pressed into outer tube  11 ) which will cause the annular rib  24  to move from the rear position illustrated in  FIG. 8   b  to a forward position (not illustrated) but where rib  24  has been moved to adjacent the forward end of passageway  22 .  
         [0087]     Initially, device  10  is in the position illustrated in  FIGS. 8, 8   a  and  8   b . In this position, annular rib  24  is located within a pair of spaced apart internal beads  25  (see  FIG. 8   b ) to provide a positive location of the inner tube  19  within the outer tube  11 , but which still enables a person to push the inner tube out of engagement with the beads  25  when required.  
         [0088]     Referring to  FIG. 8   a , the forward part of outer tube  11  as mentioned above has a number of step portions  13  which terminate in an inlet  14 . Inlet  14  is designed to attach to the rear of the catheter assembly  15  as is illustrated in  FIG. 8 .  
         [0089]     The puncture needle  18  (see  FIG. 8   a ) is secured to a needle holder  26  of special design and which forms part of the shoot back mechanism which enables needle  18  to be shot back into the rear of inner tube  19  (see  FIG. 10  and  FIG. 11 ). Needle holder  26  is initially attached to outer tube  11  but can be detached therefrom as will be described in greater detail below. Needle holder  26  contains a plurality of resilient fingers  27 . Each finger  27  contains an outwardly extending rib  28  that extends into a corresponding recess on outer tube  11 . This engagement locks needle holder  26  to outer tube  19  and inside the stepped area  13 . The advantage of having a needle holder  26  initially locked to outer tube  11  is that there is very little chance that any rearward force on needle  18  will inadvertently release the needle holder prematurely. Also, the needle will not move forwardly during the triggering operation.  
         [0090]     The resilient fingers  27  terminate in an arrowhead type configuration  29  and initially this part of the resilient fingers merely extends into the inside of outer tube  11  but is not attached to anything.  
         [0091]     The other part of the shoot back mechanism comprises an end member  30 . End member  30  is initially fitted to the open front (proximal) end of inner tube  19  and is best illustrated in  FIG. 8   a . End member  30  comprises a seal  31  which seals against the inside of inner tube  19  to maintain vacuum inside the inner tube. End member  30  is however prevented against being sucked back into inner tube  19  by a plurality of resilient fingers  32 . Fingers  32  are biased to lock against the end of inner tube  19  (see  FIG. 8   a ) and this arrangement prevents end member  30  from being sucked back into innertube  19 .  
         [0092]     The resilient fingers on end member  30  also have an arrowhead type configuration, but the arrangement is such that these resilient fingers are able to lock against the arrowhead configuration  29  on resilient fingers  27  which form part of needle holder  26 . However, this does not occur until such time as inner tube  19  is pushed forwardly.  
         [0093]     In use, a catheter assembly  15  can be fitted to the end of device  10  as illustrated in  FIG. 8  and  FIG. 16 . The catheter can then be inserted into a person&#39;s vein. The puncture needle  18  becomes contaminated during this procedure. Once the catheter assembly  15  is in place, the conventional technique of removing the puncture needle results in a needle stick risk. However, according to the present invention, once the catheter assembly is in place, a person can push inner tube  19  forwardly in a one-handed operation by grasping the wings  12  with the person&#39;s fingers and using the person&#39;s palm to push against end  23  of inner tube  19 . This causes rib  24  to push past the small locating beads  24  and along passageway  22  (see  FIG. 8   b ).  
         [0094]     This forward movement (only a few millimetres) also causes the forward end of inner tube  19  to move towards the stepped portion  13  of outer tube  11  (this being best illustrated between  FIG. 8   a  and  FIG. 9   a ). This forward movement causes the arrowhead configuration on the end of fingers  32  to contact an internal tapering face  34  (see  FIG. 9   a ) which causes the fingers  32  to be pushed inwardly. As this occurs, fingers  32  are released from the inner edge of inner tube  19 . As it is these fingers  32  that prevent end member  30  from being sucked back, as soon as the fingers are released, the end member will be sucked back into the distal portion of inner tube  19 .  
         [0095]     Importantly, as fingers  32  are pushed inwardly and become released from the edge of inner tube  19 , they also engage behind the arrowhead formation of fingers  27  which form part of needle holder  26 . Thus, as the fingers  32  are pushed inwardly, they lock against fingers  27  and this means that the end member  30  becomes locked to needle holder  26 .  
         [0096]     Therefore, as end member  30  is sucked back into the distal end of inner tube  19 , it also drags back needle holder  26  and therefore the contaminated puncture needle  18 , this position being illustrated in  FIG. 10  and  FIG. 11 .  
         [0097]     The arrangement of having the needle holder  26  initially attached to outer tube  11  means that the puncture needle  18  exhibits no forward movement by virtue of any of the shoot back mechanism which forms part of the present invention.  
         [0098]      FIGS. 12-15  illustrate the turn valve on the catheter. The valve can turn manually between an open position and a closed position as illustrated in the figures.  
         [0099]      FIGS. 1-7  illustrate a second embodiment of the invention. This embodiment also uses vacuum to suck back the contaminated needle and is similar to the embodiment described with reference to  FIGS. 8-16 . However, one difference is that instead of a two-part needle holder/end member arrangement which is described in the first embodiment, the second embodiment describes a single unit which in the second embodiment is called a needle holding piston assembly. One difference in the use of the second embodiment of the invention is that triggering the shoot back mechanism does result in the puncture needle moving forward by a few millimetres before being shot back into the inner tube. Occasionally, this slight forward movement can create discomfort to a patient.  
         [0100]     The second embodiment ( FIGS. 1-7 ) provides a cannula/catheter introducer combination comprising a cannula and catheter assembly generally indicated by arrow  41  (see  FIG. 7 ) and a retractable needle assembly generally indicated by arrow  42  for connection to the cannula/catheter combination.  
         [0101]     The cannula/catheter assembly  41  is provided with a valving member generally indicated by arrow  43  for controlling the ingress and egress of fluids from a patient.  
         [0102]     The cannula/catheter assembly is provided with a body  44  having an inlet  45  ( FIGS. 5 and 6 ) and an outlet  46  and the valving member intersects with a valve body  47 . The inlet  45  and outlet  46  respectively provide a needle aperture  48  and a slightly tapered socket  49  for connection with an outlet nozzle  50  (see  FIG. 1   a ) of the needle assembly.  
         [0103]     The valving member  43  includes a valve plunger  51  which is adjustable from a first sealing position ( FIG. 5 ) and a second flow position ( FIG. 6 ).  
         [0104]     The plunger  51  has an aperture  52  therein supporting a resilient pierceable gasket  53 . The gasket  53  allows a puncture needle  54  to pass through it and when the needle is withdrawn it closes to seal off the needle penetration.  
         [0105]     The plunger is also provided with a peripheral fluted portion  55  which when positioned in the fluid mainstream  16  (see  FIG. 6 ) allows fluid to pass in both directions.  
         [0106]     O-ring seals  57  ensure fluid tight sealing.  
         [0107]     The retractable needle assembly  42  comprises outer and inner tubes  58 ,  59  respectively (see  FIG. 1 ) with the inner tube  59  being a sliding fit in the outer tube  58 .  
         [0108]     The outer tube  58  comprises a bore and has an open rear (distal) end  60  (see  FIG. 1   b ) and is provided with forward finger gripping wings  61 . The front (proximal) end of the outer tube has a nozzle  50  that inserts into the socket  49  on the cannula/catheter.  
         [0109]     The inner tube  59  has a closed rear (distal) end  62  (see  FIG. 1   b ) and an open front (proximal) end  63  (see  FIG. 1   a ).  
         [0110]     A needle holding piston assembly  64  (see  FIG. 1   a ) is a sliding fit within the inner tube  59 . The piston assembly  64  comprises a hollow tubular body  65 , which has an open front end and a closed rear end. The closed rear end has a mounting knob  69 . A sealing member  68  is mounted over the knob  69 . A needle mounting block  66  is fitted to the open front end of the body  65 .  
         [0111]     The piston assembly  64  includes a transparent vial section  70 , which enables medical staff to establish that the needle has been correctly inserted when blood flows to the vial and is visually detected.  
         [0112]     The open distal end  60  of the outer tube  58  ( FIG. 1   b ) is provided with a shoulder  71  and the closed end  62  of the inner tube  59  has a complementary expanded portion  72  which ensures that the inner tube is secured within the outer tube. Referring especially to  FIG. 1   b , it can be seen that this arrangement allows the inner tube to be pushed forwardly into the outer tube by a few millimetres, this distance being defined by the length of the recess  31   a  (which is a few millimetres). The arrangement also ensures that the inner tube  59  cannot be readily pulled out of the outer tube  58 . This short stroke of a few millimetres is however sufficient to trigger the shoot back mechanism of the needle as will be described in greater detail below.  
         [0113]     The front end of the needle mounting block  66  is provided with a plurality of raked fingers  67 . These fingers are formed integrally with the needle mounting block and are resilient. The fingers are designed to lock against the front of inner tube  59 . The function of fingers  67  is to prevent the needle holding piston assembly  64  from moving along the inside of inner tube  59  from the proximal end of the inner tube (see  FIG. 1   a ) to the distal end of inner tube (see, for instance,  FIG. 3  and  FIG. 4 ).  
         [0114]     A vacuum is provided in inner tube  59  and seal  68  maintains the vacuum inside inner tube  59 . Thus, there is a force acting on the needle holding piston assembly  64  to “suck” the needle holding piston assembly  64  back into inner tube  59  towards the distal end of the inner tube; however the resilient fingers  67  lock against the front of inner tube  59  and prevent the needle holding piston assembly  64  from being sucked back.  
         [0115]     The arrangement described immediately above and illustrated in  FIG. 1  and FIG.  1   a , is the initial position of the device.  
         [0116]     To dislocate the fingers  67 , the end  62  of the inner tube is pushed forward using the palm of the hand whilst gripping the wings  61  with the fingers. The fingers are thereby forced into the tapered section of the nozzle  50  and compressed to the extent that the needle assembly is withdrawn under vacuum, the situation illustrated by  FIGS. 3 and 4 .  
         [0117]     More specifically, inner tube  59  can be pushed forwardly by a few millimetres in the manner described immediately above which moves the expanded portion  72  (see  FIG. 1   b ) from the position illustrated in  FIG. 1   b , to a position (not illustrated) where the expanded portion is now at the other end of the recess  31   a . This short distance is sufficient to trigger the needle shoot back mechanism. Specifically, and best illustrated in  FIG. 2   a , as the inner tube  59  is pushed forwardly by a few millimetres, it will push the needle holding piston assembly  64  forwardly by a few millimetres. As this occurs, the resilient fingers  67  push forwardly (as they form part of the needle block  66  which is attached to the front of the needle holding piston assembly  64 ). The front part of outer tube  58  tapers inwardly (see  FIG. 1   a ) and the resilient fingers  67  are arrow shaped in configuration which means that as the resilient fingers are pushed forwardly, they will be pressed inwardly (see  FIG. 2   a ), and consequently they will dislodge from the front of inner tube  59 . As soon as the fingers  67  have been released from inner tube  59 , the vacuum inside inner tube  59  will suck back the needle holding piston assembly  64  thereby retracting the contaminated puncture needle  54  back into the body of inner tube  59 , this position being illustrated in  FIG. 3  and  FIG. 4 .  
         [0118]     The forward movement of inner tube  59  is limited by the arrangement illustrated in  FIG. 1   b , and also by a shoulder  73  (see  FIG. 2   a ) on outer tube  58 .  
         [0119]     Once the cannula/catheter device is secured and the needle assembly removed, the cannula/catheter can be used for the introduction or withdrawal of fluids to and from a patient.  
         [0120]     The arrangement is simple to use and, in practice, once the device has been inserted into the cannula assembly  41 , the inner tube  59  is pushed forwardly by just a few millimetres without any requirement to rotate the inner tube or use any separate locking mechanisms and upon forward pushing of the inner tube, the contaminated needle  54  is sucked back to the rear of inner tube  59  to render the contaminated needle  54  safe. It is not possible to push or otherwise enable the contaminated needle  54  to emerge from the safety of inner tube  59 . The arrangement is a simple one-handed reliable arrangement.  
         [0121]      FIGS. 1 and 2  of the drawings show the fully assembled device as delivered for use,  FIG. 3  of the drawings with the needle withdrawn after use, and  FIG. 4  separation of the cannula/catheter from the needle assembly.  
         [0122]      FIGS. 5 and 6  of the drawings show alternative positions of the plunger  51  of the valving member  43 .  
         [0123]     In  FIG. 5 , the plunger  51  is in a first position with the gasket  53  blocking fluid flow.  
         [0124]     In  FIG. 6 , the plunger  51  has been manually repositioned and the fluted portion  55  provides a passage for fluid flow.  
         [0125]      FIG. 7  of the drawings is an assembly drawing of the device of the present invention in a ready-to-use condition.  
         [0126]     Aspects of the present invention have been described by way of example only and modifications and additions thereto may be made without departing from the spirit or scope thereof.