a first preferred embodiment of the present invention is shown in fig1 . the needle trap , which also serves as a handle for the insertion of a catheter , consists of a standard luer - lock syringe barrel ( 11 ) containing a needle guide ( 15 ) which is roughly the size and shape of a tuberculin syringe and which has a male tapered end ( 20 ) onto which a standard hollow - bore steel insertion needle ( 12 ) and its transparent polyvinyl needle holder ( 13 ) are matingly connected by either friction or luer - lock coupling . the hollow - bore steel insertion needle is stabilized within the needle trap by means of a standard rubber plug ( 14 ) through which the needle passes as it exits the assembly to pass through the intravenous catheter ( 16 ) to extend beyond the tip of the soft catheter ; and by frictional attachment of the needle holder to the hollow needle guide ( 15 ). the exterior portion of the needle ( 12 ) is sheathed by a silastic catheter ( 16 ) beyond which the sharp tip of the needle extends . sterility of the needle and catheter are protected by a throw - away puncture - proof scabbard ( 17 ). the trailing or proximal end of the intravenous catheter ( 16 ) is fitted to the needle trap by means of a standard needle hub ( 18 ) which screws into a luer - lock fitting ( 19 ) on the needle trap . a tapered concentric tube of decreasing bore ( 22 ) is bonded to the proximal or trailing end of the needle trap ( 11 ) or to a flange integral therewith ( 21 ) s that the body of the needle guide ( 15 ) will slide through the narrowest bore of the tapered tube ( 22 ), but the needle holder ( 13 ) will not ( see fig2 ). a compatible female fitting ( 24 ) of appropriate diameter is molded into the proximal or trailing end of the hollow needle guide for filling the assembly with infusion fluid or withdrawing venous blood , if so desired . this hub is normally occluded by a removable male cap ( 25 ) held firmly by friction means into the female fitting . after the catheter / needle assembly is inserted into a vein ( not shown ), as evidenced by &# 34 ; flash - back &# 34 ; of venous blood from the hollow - bore steel needle into its clear vinyl holder ( 13 ), and the breakaway needle guide ( 15 ) is withdrawn the needle and its holder become stuck within the tapered portion ( 22 ) of the needle trap by friction . the needle guide may then be separated from the needle holder by pulling . after removal of the needle guide , the distal catheter ( 16 ) may then be detached and left in place by grasping its proximal luer - lock hub ( 18 ) while twisting the needle trap assembly counterclockwise and removing it from the catheter . as shown in fig2 when the clear needle holder is fully retracted , friction between the rigid plastic needle holder ( 13 ) and a softer tapered inner surface of the needle trap ( 22 ) will prevent sliding of the insertion needle in either direction . removal of the break - away needle guide ( 15 ) is accomplished by means of either traction or traction and twisting . once the needle guide breaks away from the needle holder , the needle holder and needle are safely contained within the needle trap for disposal . the rubber plug ( 14 ) in addition to stabilizing the needle during insertion , also serves to block exit of the sharp needle from the trap if the needle holder becomes unstuck from the tapered part of the trap . for those who prefer to use butterfly infusion sets permanently linked to silastic catheters , a second preferred embodiment using a breakable wire linkage for the insertion needle is shown in fig3 . a &# 34 ; winged &# 34 ; or &# 34 ; butterfly &# 34 ; catheter hub is substituted for the standard round needle hub (( 18 ) fig1 ). the &# 34 ; butterfly &# 34 ; configuration of the silastic catheter hub supplies increased surface for holding , after the catheter is placed in the vein and the user retracts the steel needle into its trap ; and provides a broader surface for taping the inserted catheter to a patient &# 39 ; s skin ( not shown ). the butterfly wings may be set in a gliding plane in relation to the long axis of the needle in order to facilitate needle insertion , as well as to keep the proximal end of the hub from indenting the skin over a selected vein after the silastic catheter is secured by taping . such assemblies ( see , for example , u . s . pat . no . 4 , 177 , 809 to moorehead ) characteristically use tiny intraluminal guide wires as a needle guide to control the position of the sharp needle tip in relation to the leading end of the silastic catheter tube . the user safety of such assemblies can be augmented by making these wires breakable so that the steel insertion needles can be safely housed in a proximally located needle trap , as shown . this second preferred embodiment of the present invention is particularly adapted for butterfly infusion sets consisting of a silastic tube ( 51 ) through which a specially made hollow bore steel needle ( 52 ) slides to insert the silastic catheter . during insertion , the needle is held steady by the body and attached wings of the molded butterfly ( 53 ) through which the needle point extends to the exterior . the body of the butterfly also forms the permanent hub ( 54 ) which holds the base of an intravenous silastic catheter ( 55 ). the steel needle , essential for insertion of the catheter , is perforated ( 56 ) along its shaft near the trailing end to permit &# 34 ; flash - back &# 34 ; of visible blood when the needle and surrounding silastic catheter are inserted into a vein . proximal to this perforation , the needle is crimped ( 57 ) and proximally splayed around a stainless steel wire ( 58 ) used to hold the needle in place and to withdraw the needle into a tripartite proximal hub assembly ( 59 ) after intravenous insertion of the catheter . the central portion of the tripartite proximal hub ( 60 ) forms a rigid tube aligned with the long axis of the steel needle . the length of this tube , added to the depth of the affixed trap , directly in line with the long axis of the needle . the needle trap must be longer than the steel needle . at its proximal end , this needle trap portion of the assembly is covered with an air - tight rubber stopper ( 74 ) through which the guide wire is manipulated by a rigid handle ( 62 ). before insertion of the needle into a vein , the wire normally holds the sharp tip extended just beyond the distal opening of the silastic catheter . after the catheter is properly positioned within the vein , the rigid handle ( 62 ) provides means for withdrawing the insertion needle back into a locked position within the needle trap ( see fig4 ). the remaining sections of the tripartite hub are inlet ports for injecting fluid into the system , preferably via a standard male adapter on one side , and a rubber stopper on the other ( not shown ). it should be added that the first preferred embodiment can be made as a winged or &# 34 ; butterfly &# 34 ; assembly by attaching flexible wings to the flanged catheter hub in order to increase surface area for grasping the taping ( not shown ). after the winged silastic catheter is in place , the insertion needle is withdrawn in the direction of the arrow ( fig4 ). fig4 shows a detail of the proximal hub portion after the guide wire is withdrawn from the winged needle assembly . comparison with fig5 will reveal that mechanical splaying of the proximal portion of the hollow needle in the defined stepped pattern serves to release the needle from the needle guide . the needle ( 52 ) becomes safely housed in the needle trap and central portion of the proximal hub ( 59 ), and is prevented from leaving by a splaying of crimped parts ( 72 ) by an internal wedge - like part ( 73 ) within the bore of the affixed trap ( see fig4 and 5 for details ). such splaying , in turn , releases the crimp on the trailing end of the steel needle , such that the needle remains behind ; while the insertion wire and its handle are retracted in the direction of the arrow . although a dulled tip on the wire may have blood on its surface , after being wiped on its passage back through the rubber cap ( 74 ) it will be much less likely to inflict a dangerous wound than a rapier - like needle with blood in its bore , thrusting unpredictably on the end of a similar wire no longer confined within combinations of rigid and elastic tubing . in the first preferred embodiment , the use of a luer - lock syringe as both the needle trap and a means for holding the device during catheter insertion offers the following advantages : 1 . use of a luer - lock syringe for both a needle trap and for holding the silastic catheter makes it relatively easy for the user to accurately insert the sheathed needle into a vein , because the assembly puts syringe / needle in customary positions and the catheter is prevented from sliding off the trap if the insertion needle is pulled back . 2 . because the rubber needle stabilizer plug permits the needle to easily slide through during retraction , very little negative pressure will be generated in the syringe . in fact , if the needle stabilizer plug is tightly fitted to the internal bore of the syringe , it is unlikely to move during retraction of the needle guide . thus , the needle stabilizer plug will provide an additional barrier through which a retracted needle must pass before getting back out of the syringe and appended trap . 3 . because no suction or significant increase in positive pressure will be generated before the hollow bore steel needle is withdrawn from a vein via traction on the needle guide , it is optional whether the system is filled with infusion fluid or left filled with air before venepuncture . 4 . finally , the combined use of a flanged hub and a luer - lock syringe for silastic catheter introduction increases user control over the position of the catheter and decreases the likelihood of silastic ( usually teflon ) embolization in the patient . cutting off of the silastic by twisting of the needle bevel or advancement of the catheter over the needle cannot occur unless the user intentionally pulls the needle guide back some distance and then advances it . it should be noted that trapping the used introducer needle to prevent accidental needle - stick injury is an essential part of the invention . moreover , the use of a breakaway coupling provides an assembly that is more convenient to use . while the foregoing intravenous catheter insertion assembly has been described , in part , in terms of specific embodiments , these embodiments are exemplary only and not intended to be limiting . it will be appreciated by those skilled in the art that wide variation in details can be made without departing from the spirit of the invention as hereinafter claimed .
an intravenous catheter insertion device comprising an intravenous silastic or teflon catheter , a hollow - bore steel introducer needle , a break - away needle guide and a needle trap . prior to catheter insertion the needle is concentric within the catheter with one end extending past the distal end of the catheter . the other end of the needle is releasably attached to a needle guide . after the needle is used to guide the catheter into a vein , the needle guide is withdrawn . as the needle guide is withdrawn , the introducer - needle is drawn out of the intravenous catheter into the needle trap . as the needle guide is further withdrawn , the introducer - needle breaks loose from the needle guide to remain safely housed within the trap . the invention is easily adapted for use with most conventional intravenous catheter assemblies .