WO2000018465A1

WO2000018465A1 - Needle retraction mechanism with consistent retraction speed

Info

Publication number: WO2000018465A1
Application number: PCT/US1999/022449
Authority: WO
Inventors: Greg L. Brimhall; William G. Moulton; Gregory Quickel
Original assignee: Becton, Dickinson And Company
Priority date: 1998-09-30
Filing date: 1999-09-28
Publication date: 2000-04-06
Also published as: AU1096600A; WO2000018465A8

Abstract

A needle retraction mechanism (10) includes a hollow handle (20) with a longitudinal axis defining a cavity (21) wherein the cavity has an inner diameter that decreases from its proximal portion to its distal portion. Included in the mechanism is an elongate needle (30) with an open bore therethrough with a sharp distal point (31) and a proximal end (32). The needle (30) has a first position where it is disposed in the cavity (21) so that the sharp distal point (31) of the needle (30) is proximal of the distal portion of the handle (20) and a second position where it is disposed within the cavity (21) so that the sharp distal point (31) of the needle (30) projects axially beyond the distal end (23) of the handle (20). A needle hub (40) is connected to the needle. The needle hub (40) includes a flexible stopper (45) at its proximal end that creates an air tight seal with the inner wall of the handle (20). This allows a vacuum to be created between the proximal end (22) of the handle (20) and the flexible stopper (45) when the needle hub (40) is moved from the first position to the second position. The tapered configuration of the cavity (21) results in consistent retraction speeds for the mechanism.

Description

NEEDLE RETRACTION MECHANISM WITH CONSISTENT RETRACTION SPEED

This application is a continuation in part of application Serial No.

09/164,072 filed on September 30,1998.

Background of the Invention This invention generally relates to needle retraction mechanisms. More particularly, this invention relates to needle retraction mechanisms that are used in the medical field. Such needle retraction mechanisms find particular applicability in connection with intravascular catheters, syringes, blood collection tubes and lancets. Catheters, particularly intravenous (IV) catheters, are used for infusing fluid, such as normal saline solution, various medicaments and total parenteral nutrition, into a patient or withdrawing blood from a patient. Peripheral IV catheters tend to be relatively short, and are on the order of about one and one- half inches in length. The most common type of IV catheter is an over the needle peripheral IV catheter. As its name implies, an over the needle catheter is mounted over an introducer needle having a shaφ distal tip. The catheter and the introducer needle are assembled so that the sharp distal tip of the introducer needle extends beyond the distal tip of the catheter with the bevel of the needle facing up away from the patient's skin. The catheter and introducer needle assembly is inserted at a shallow angle through the patients skin into a peripheral blood vessel, i.e. a smaller blood vessel that is not connected directly to the heart but is one of the branches of the central blood vessels that is directly connected to the heart. In order to verify proper placement of the assembly in the blood vessel, the clinician confirms that there is flashback of blood in the needle and in a flashback chamber located at the proximal end of the needle in conjunction with the needle hub. Once proper placement is confirmed, the clinician applies pressure to the blood vessel by pressing down on the patient's skin distal to the tip of the needle and the catheter. This finger pressure minimizes further blood flow through the catheter and needle. The clinician advances the catheter into the blood vessel, withdraws the needle, leaving the catheter in place, and attaches a fluid handling device to the catheter hub.

Once the introducer needle is withdrawn from the catheter, it is a "blood contaminated shaφ" and must be properly handled. With the recognition by the medical device industry of the risk of transmission of Acquired Immunosuppressive Deficiency Syndrome (AIDS) by blood contaminated shaφs, various needle shielding mechanisms have been developed. One type of a needle shielding mechanism uses a substantially hollow handle with an introducer needle movably disposed in the handle. In such a device, the shaφ distal tip of the needle may be extended from a hollow handle so the shaφ distal tip of the needle is exposed. After the needle has been used to place a catheter into a patient, the needle can be retracted into the handle so that the shaφ distal tip of the needle is no longer exposed. Various biasing mechanisms can be used to allow the introducer needle to be retracted into the handle after use. For example, a helical spring, either in compression or tension, could be used to provide the biasing force. Alternatively, an elastic tube could be used to provide the biasing force. In order to minimize the number of parts needed for the device, a vacuum created in the proximal portion of the handle between the proximal wall of the handle and the proximal portion of the needle/needle hub can be used to provide the biasing force to retract the needle into the handle. Although such devices generally work for their intended puφose, they could be improved. For example, it is desirable that the needle be retracted into the handle with a specific speed profile. For example, the retraction speed should not be too slow. If it is too slow the shaφ distal tip of the needle will be exposed longer than is necessary after the procedure. Increased exposure time increases the risk of an accidental needle stick. On the other hand, the retraction speed should not be too fast. If the retraction speed is too fast, any blood in the needle, flashback chamber or on the exterior of the needle could become airborne during needle retraction and could be deposited outside of the handle. Such a potential blood splatter issue is especially problematic when the needle is initially removed from the catheter after the catheter has been properly placed in the patient because significant amounts of blood may have contaminated the device. This is unacceptable when the blood could be contaminated by blood borne pathogens.

Where a helical spring or an elastic tube is used as the biasing mechanism, the spring or tube can be designed to ensure that the needle is retracted with an appropriate speed profile. However, where a vacuum is used as the biasing mechanism, control of the retraction speed profile becomes problematic as the biasing mechanism is atmospheric pressure. Because the atmospheric pressure varies with altitude, the needle retraction speed profile is difficult to control. Heretofore there has not been a mechanism to accurately control the retraction speed profile of the needle for a needle retraction mechanism that makes use of a vacuum as the biasing mechanism.

Summary of the Invention

It is an object of this invention to provide a needle retraction mechanism that provides a desired needle retraction speed profile for the device.

It is another object of this invention to provide a needle retraction mechanism that provides a desired needle retraction speed profile for the device even where the needle retraction mechanism uses a vacuum as the biasing mechanism. It is yet another object of this invention to provide a needle retraction 20 mechanism that provides a desired needle retraction speed profile for the device when the needle retraction mechanism is used at different altitudes even where the needle retraction mechanism uses a vacuum as the biasing mechanism. The needle retraction mechanism of the present invention includes a hollow handle defining an inner wall, an outer wall and a cavity, a needle, a needle hub and a needle cover. The handle has a closed proximal end and a distal end defining an opening therein. The inner wall of the handle has a tapered configuration along a medial portion of the handle. This taper decreases the inner diameter of the handle toward the distal end of the handle. The handle includes a release mechanism adjacent to the distal end. This release mechanism cooperates with the needle hub to allow the needle to be retracted into the handle after the needle has been used. The needle has an open bore therethrough with a shaφ distal tip and a proximal end. The needle hub assembly is connected to the proximal end of the needle and defines a flashback chamber therein. The needle hub also includes a stopper portion that engages the inner wall of the barrel and creates an air tight seal with the inner wall. The stopper ensures that a vacuum is created between the proximal end of the handle and the stopper when the needle hub is moved from the proximal end to the distal end of the handle. The needle hub cooperates with the release mechanism adjacent to the distal end of the handle to hold the needle in the extended position. The needle cover is removably connected to the needle hub and is disposed over the needle. The needle cover includes a configuration that is easily grasped by a clinician to facilitate extension of the needle. When the needle retraction mechanism of the present invention is used to place a catheter into a patient, a standard catheter is located coaxially over the needle.

In the retracted position prior to use, the needle hub is adjacent to the proximal end of the handle. The handle is long enough so that the shaφ distal tip of the needle does not extend past the distal end of the handle. Indeed preferably, the shaφ distal tip of the needle is proximal of the distal end of the handle. This further minimizes the chance of an accidental needle stick from occurring if the needle cover is accidentally removed from the needle prior to use or after the needle has been retracted into the handle after use. Prior to use of the needle retraction mechanism of this invention, the needle cover is disposed over the needle to shield the shaφ distal tip of the needle. In addition, the needle cover is operatively connected to the needle hub with the distal portion of the needle cover extending beyond the distal end of the handle. This provides a handle for the clinician to grasp the needle cover and extend the needle so the shaφ distal tip of the needle extends beyond the distal end of the handle. The needle hub includes a latch that is configured so that it engages a distally facing shoulder formed in the inner wall of the handle to temporarily lock the needle in the extended position. Since the stopper creates an air tight seal with the inner wall, moving the needle hub distally creates a vacuum in the space between the proximal end of the handle and the needle hub. This vacuum biases the needle hub and thus the needle toward the proximal end of the handle when the clinician properly places the catheter into a patient, the clinician can press the release mechanism of the handle. This releases the latch on the needle hub from engagement with the distally facing shoulder in the inner wall of the handle and allows the vacuum to bias the needle hub and thus the needle toward the retracted position. The retraction speed profile of the needle hub, and thus the needle, can be controlled by the configuration of the inner wall of the handle. For example, by tapering the inner wall of the handle so the inner diameter of the handle decreases toward the distal end of the handle, the speed of retraction at the initial phases of needle retraction will be slower than the speed of retraction at the final phase of needle retraction. This change in retraction speed occurs because of the interference between the stopper on the needle hub and the inner wall of the handle. Along the narrow portion of the taper, there is greater interference between the stopper and the inner wall of the handle. This greater interference results in a greater force opposing the vacuum force biasing the needle hub toward the proximal end of the handle which slows down the speed of retraction. Along the wider portion of the taper there is less interference between the stopper and inner wall of the handle. This lesser interference results in less force opposing the vacuum force biasing the needle hub toward the proximal end of the handle. Thus the needle retraction speed will be greater along this portion of the handle.

The above and other objects and advantages of the invention will be apparent upon consideration of the following detailed description.

Brief Description of the Drawings The preferred embodiments are illustrated in the drawings in which like reference numerals refer to like elements and in which:

FIG. 1 is an exploded perspective view of the needle retraction mechanism of the present invention for use with an intravascular catheter;

FIG.2 is a cross-sectional view of the needle retraction mechanism of the present invention for use with an intravascular catheter with the needle in the retracted position with the needle cover still covering the needle;

FIG. 3 is a cross-sectional view of the needle retraction mechanism of the present invention for use with an intravascular catheter with the needle in the extended position with the needle cover still covering the needle; FIG. 4 is a cross-sectional view of the needle retraction mechanism of the present invention for use with an intravascular catheter with the needle in the extended position with the needle cover removed;

FIG. 5 is an enlarged cross-sectional view of the distal portion of the needle retraction mechanism of the present invention with the needle in the extended position;

FIG. 6 is a cross-sectional view of the needle retraction mechanism of the present invention for use with an intravascular catheter with the needle in the retracted position and the needle cover removed;

FIG. 7 is an enlarged cross-sectional view of the proximal portion of the needle retraction mechanism of the present invention with the needle in the retracted position;

FIG. 8 is an enlarged cross-sectional view of the handle used in connection with the needle retraction mechanism of the present invention;

FIG. 9 is a schematic profile of one geometry of the inner wall of the handle used in connection with the needle retraction mechanism of the present invention; and

FIG. 10 is a schematic profile of another geometry of the inner wall of the handle used in connection with the needle retraction mechanism of the present invention.

Detailed Description of the Invention

As used herein, the term "proximal" refers to a location on the needle retraction mechanism of this invention 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 on the needle retraction mechanism of this invention farthest from the clinician using the device and closest to the patient in connection with whom the device is used.

Although this invention is described herein in connection with intravascular catheters, it is to be understood that this invention is applicable to other medical devices where it is desirable for a medical needle to be shielded after use. In addition, while this invention is satisfied by embodiments in many different forms, there are shown in the drawings and herein described in detail, preferred embodiments of the invention with the scope of the invention measured by the appended claims. Referring to the FIG. 1, the needle retraction mechanism 10 of the present invention includes a hollow handle 20, an elongate introducer needle 30, a needle hub assembly 40, a flexible stopper 45 connected to needle hub assembly 40, a needle cover 50 and a catheter 60. No separate biasing element is used in the present invention. Instead a vacuum created proximal of flexible stopper 45, when needle hub assembly 40 is moved from its proximal position in handle 20 to its distal position in handle 20, is used to bias needle hub assembly 40, and thus needle 30, toward the retracted position.

Handle 20 defines an elongate cavity 21 and has a closed proximal end 22 and an open distal end 23. Suitable materials for forming handle 20 include, but are not limited to, thermoplastic polymeric resins such as polycarbonate, polystyrene, polypropylene and the like. Handle 20 is preferably formed from a substantially transparent or at least translucent material to allow a clinician to view the interior thereof.

Handle 20 includes a latching mechanism that may be located along a distal portion of handle 20. The latching mechanism temporarily locks needle hub assembly 40 adjacent to distal end 23 of handle 20 against the bias of the vacuum created between flexible stopper 45 and proximal end 22 of handle 20 when flexible stopper 45 is moved distally from its retracted position. The latching mechanism can take many forms. See for example U.S. Patent No.5,487, 734 the disclosure of which is expressly incoφorated herein by reference. However, preferably the latching mechanism is a distally facing shoulder 24 formed adjacent to distal end 23 of handle 20. Distally facing shoulder 24 engages a portion of needle hub assembly 40 to temporarily lock needle hub assembly 40 of the needle retraction mechanism of the present invention in the extended position against the bias of the vacuum. A tab 25 formed in and connected to the wall of handle 20 via a living hinge is used to disengage that portion of needle hub assembly 40 from distally facing shoulder 24 to allow needle hub assembly 40, and thus needle 30, to be retracted toward proximal end 22 of handle 20. The inner wall 26 of handle 20 can be configured in such a way to control the retraction speed profile of the present invention. See FIGS. 9 and 10. For example in a preferred embodiment, inner wall 26 is tapered so that the inner diameter of handle 20 decreases from proximal end 22 to distal end 23. See FIG. 9. Preferably the taper does not extend completely to proximal end 22 or completely to distal end 23. Instead the inner diameter of handle 20 should be substantially constant along the distal portion of handle 20 and the inner diameter of handle 20 should be substantially constant along the proximal portion of handle 20 while the inner diameter of handle 20 should decrease along an intermediate portion of handle 20 from the proximal portion to the distal portion with the inner diameter along the proximal portion being smaller than the inner diameter along the distal portion. See FIG. 10. This tapered configuration varies the interference between inner wall 26 and flexible stopper 45 that is connected to needle hub assembly 40. This variable interference controls the retraction speed profile of the needle hub assembly. Needle 30 has an open bore therethrough and a shaφ distal tip 31 defined by a bevel 31a. Needle 30 is preferably formed from a stainless steel alloy or the like. Needle 30 is connected at its proximal end 32 to needle hub assembly 40.

Needle hub assembly 40 defines a flashback chamber 41 and a movable latch 42. Latch 42 engages distally facing shoulder 24 when needle hub assembly 40 is adjacent to distal end 23 of handle 20. See FIGS. 3-5. Latch 42 is preferably connected to the main body portion of needle hub assembly 40 by a living hinge and is biased away from the main body portion of needle hub assembly 40. This allows latch 42 to engage distally facing shoulder 24 when latch 42 is distal of distally facing shoulder 24 and needle hub assembly 40 is biased to proximal end 22 of handle 20. When a clinician depresses tab 25, it forces latch 42 out of engagement with distally facing shoulder 24. This allows needle hub assembly 40 and thus needle 30 to be retracted into handle 20. Suitable materials for forming needle hub assembly 40 include, but are not limited to, thermoplastic polymeric resins such as polycarbonate, polystyrene, polypropylene and the like.

As noted above, flexible stopper 45 is connected to the proximal end of needle hub assembly 40. Flexible stopper 45 is preferably formed with two radially extending flanges 45a and 45b defining a trough 45c therebetween. Flanges 45a and 45b create an air tight seal with inner wall 26 of handle 20.

Thus when needle hub assembly 40 is moved from its retracted position adjacent to proximal end 22 of handle 20 toward its extended position adjacent to distal end 23 of handle 20, a vacuum, or at a minimum an area of negative pressure relative to the area distal of flexible stopper 45, is created in the space between flexible stopper 45 and proximal end 22 of handle 20. Suitable materials for forming flexible stopper 45 include, but are not limited to, elastomeric thermoset polymers such as polyisoprene and styrene butadiene rubber (SBR).

Preferably, a silicone oil is located in trough 45c so that flanges 45a and 45b wipe the silicone oil against inner wall 26 as flexible stopper 45 moves therealong. It has been found that the amount and viscosity of the silicone oil in combination with the degree of interference between flexible stopper 45 and the inner wall of handle 20 affects the retraction speed for needle hub assembly 40 as it is biased toward proximal end 22 by the vacuum. When larger amounts of silicone oil are used, the retraction speed is quicker. When more viscous silicone oil is used, the retraction speed is slower. When the interference is greater, the retraction speed is slower. The degree of interference between flexible stopper 45 and the inner wall of handle 20 also affects the amount of force needed to overcome the static friction between flexible stopper 45 and the inner wall of handle 20 when needle hub assembly 40 is adjacent to distal end 23 of handle 20 prior to retraction of needle hub assembly 40 by the vacuum. The greater the interference, the greater the force needed to overcome this static friction. However, the amount and viscosity of the silicone oil are significantly less relevant to overcoming this static friction.

Needle cover 50 is removably connected to needle hub assembly 40 and is sized and shaped to fit over needle 30 and within handle 20. The puφose of needle cover 50 is two fold. First, needle cover 50 serves to prevent accidental contact with shaφ distal tip 31 of needle 30 prior to insertion of needle 30 into a patient. Second, needle cover 50 serves as a handle connected to needle hub assembly 40 to allow a clinician to move needle hub assembly 40 distally to a position adjacent to open distal end 23 of handle 20. When needle hub assembly 40 is in this position it is "armed" and ready for use. Suitable materials for forming needle cover 50 include, but are not limited to, thermoplastic polymeric resins such as polycarbonate, polystyrene, polypropylene and the like.

Needle cover 50 should be sufficiently long so that when needle hub assembly 40 is adjacent to proximal end 22, the distal portion of needle cover 50 extends distally beyond distal end 23 of handle 20. This makes it easy for the clinician to move needle hub assembly 40 distally. The proximal portion of needle cover 50 is formed with an arm 58 and an upwardly extending finger 59. Finger 59 engages the proximal face of a flange 43 formed adjacent to the distal end of needle hub assembly 40 and thus pulls needle hub assembly 40 in the distal direction when needle cover 50 is pulled distally. The distal portion of needle hub assembly 40, the distal portion of handle 20, arm 58 and finger 59 must be appropriately configured so that finger 59 will stay engaged with flange 43 until the proximal end of latch 42 is distal of distally facing shoulder 24 but will become disengaged with flange 43 thereafter. Preferably arm 58 is biased outwardly from needle hub assembly 40 so that when the proximal end of latch 42 is distal of distally facing shoulder 24, arm 58 and finger 59 are no longer constrained against outward movement by handle 20. At that point finger 59 will become disengaged from flange 43 and needle hub assembly 40 will be temporarily locked adjacent to distal end 23 of handle 20 by virtue of the engagement between latch 42 and distally facing shoulder 24 against the bias of the vacuum created between proximal end 22 of handle 20 and flexible stopper 45.

A catheter 60 that has a proximal end 61, a distal end 62 and a catheter hub 63 affixed to catheter proximal end 61 is mounted over needle 30 so that catheter distal end 62 is proximal of shaφ distal tip 31 of needle 30. Suitable materials for catheter 60 include thermoplastic resins such as fluorinated ethylene propylene (FEP), polyurethane and the like. Preferably, catheter 60 is formed from a thermoplastic hydrophilic polyurethane that softens with exposure to physiological conditions present in the patient's body. Suitable materials for catheter hub 63 include, but are not limited to, thermoplastic polymeric resins such as polycarbonate, polystyrene, polypropylene and the like.

In order to place a catheter into a patient's blood vessel, the clinician grasps the distal portion of needle cover 50 and pulls its so as to move needle hub assembly 40 toward distal end 23 of handle 20. When the proximal end of latch 42 is distal of distally facing shoulder 24, finger 59 becomes disengaged from flange 43 so that needle cover 50 no longer shields needle 30. At this point, the proximal end of latch 42 engages distally facing shoulder 24 to temporarily lock needle hub assembly adjacent to distal end 23 of handle 20 so shaφ distal tip 31 of needle 30 and catheter 60 extend beyond distal end 23 of handle 20. This distal movement of flexible stopper 45 with needle hub assembly 40 creates a vacuum in the space between proximal end 22 of handle 20 and flexible stopper 45. The clinician can then substantially longitudinally align needle 30 and catheter 50 with the target blood vessel. Bevel 31 a should be facing substantially away from the skin surface during venipuncture. The clinician inserts needle 30 and catheter 60 at a shallow angle, preferably less than about 35 degrees, into the skin so that shaφ distal tip 31 enters the target blood vessel. The clinician then preferably observes a blood flashback in flashback chamber 41. After confirming placement of needle 30 and catheter 60 in the target blood vessel, the clinician advances catheter 60 distally axially along needle 30 into position in the blood vessel. After proper placement of catheter 60 is achieved, the clinician places a finger from his other hand on the patient's skin over the blood vessel distal of distal end 62 of catheter 60 and shaφ distal tip 31 of needle 30. By placing his finger on the patient's skin and applying sufficient pressure on the skin, the clinician thereby minimizes blood flow through catheter 60. The clinician then withdraws needle 30 from catheter 60 by depressing tab 25. Depressing tab 25 forces latch 42 toward needle hub assembly 40 and out of engagement with distally facing shoulder 24. This allows the vacuum to urge needle hub assembly 40, and thus needle 30, into the retracted position within needle 20. The clinician may then attach any desired fluid handling device to catheter hub 63 and commence the planned treatment. Handle 20 with needle 30 substantially within it may then be disposed of according to the facility's disposal protocol. Because inner wall 26 is tapered so the inner diameter of needle 30 decreases toward distal end 23, the force exerted on flexible stopper 45 caused by inner wall 26 compressing flexible stopper 45 decreases as needle hub assembly 40 and thus flexible stopper 45 move proximally. This configuration ensures that the retraction speed of needle is slower at the initial stages of needle retraction and is faster at the final stages of needle retraction. This retraction speed profile prevents blood within or on the surface of needle 30 or within flashback chamber 41 from becoming airborne and being deposited outside of handle 20. In addition, since the inner diameter of handle 20 is greater along the proximal portion of handle 20, flexible stopper 45 is less likely to be influenced by compression set and is less likely to be permanently reduced in diameter when the needle retraction device 10 of this invention is stored for long periods of time with needle 30 in the retracted position. Moreover, even if flexible stopper 45 is influenced by compression set within the proximal portion of handle 20, the taper of inner wall 26 still allows a vacuum to be created and maintained between proximal end 22 and flexible stopper 45. This is because flexible stopper 45 will be further compressed by inner wall 26 as needle hub assembly 40 is moved distally.

Thus it is seen that a needle retraction mechanism is provided that retracts the needle at a desired speed within a narrow range of values even where the needle retraction mechanism uses a vacuum as the biasing mechanism.

Claims

We claim:

1. A needle retraction device comprising: a handle having a proximal portion and a distal portion and defining a cavity having an inner diameter that decreases from the proximal portion to the distal portion, the handle having a proximal end and a distal end defining an opening therein; a needle with a proximal end and a shaφ distal point; a needle hub connected to the needle and having a proximal portion and a 10 distal portion; and a latch associated with the needle hub to releasably hold the needle in an extended position.

2. A needle retraction device, comprising: a handle having a proximal portion, an intermediate portion and a distal portion and defining a cavity having an inner diameter that is substantially constant along the proximal portion and the distal portion and that decreases along the intermediate portion from the proximal portion to the distal portion, the handle having a proximal end and a distal end defining an opening therein; a needle with a proximal end and a shaφ distal point; a needle hub connected to the needle; and a latch associated with the needle hub to releasably hold the needle in an extended position.

3. The needle retraction device of claim 2 wherein the inner diameter along the proximal portion is less than the inner diameter along the distal portion.