WO1990001349A1

WO1990001349A1 - Injection site needle

Info

Publication number: WO1990001349A1
Application number: PCT/US1989/003182
Authority: WO
Inventors: David S. Utterberg
Original assignee: Utterberg David S
Priority date: 1988-08-01
Filing date: 1989-07-24
Publication date: 1990-02-22
Also published as: AU3988989A

Abstract

A precisely shaped, but not sharp, hollow needle (2) capable of penetrating a resilient sealing member, such as an elastomeric injection site closure (110) or an elastomeric vial stopper, while being highly resistant to accidental penetration of human skin or tissue. Preferably, the needle's hollow shaft has gauge (c) in the range from 17 through 30, and has a closed, blunt end (10) having a radius (D) of about 0.15 mm to about 0.6 mm, roughly similar to a ball point pen in its ability to puncture human skin. The needle shaft has an orifice (8) spaced along the needle's longitudinal axis from the needle's closed end (10). The needle is preferably designed so that no more than about 1.8 kg of force must be exerted on the needle to cause it to penetrate each injection site with which it will be used. An elastomeric sheath (6) may be mounted around the needle.

Description

INJECTION SITE NEEDLE

Field of the Invention

The invention is a precisely shaped, but not sharp, needle capable of penetrating a resilient sealing member, such as elastomeric injection site closures or vial stoppers, while being highly resistant to accidental penetration of human skin or tissue.

Background of the Invention

Almost six billion hypodermic needles are used each year in the U.S. by health workers, lab workers, and patients. The design of hypodermic needles and their points has remained essentially unchanged since the nineteenth century, and is intended to make the needle sharp enough to pierce skin and underlying tissue with the least resistance to insertion and the least pain and tissue trauma to the patient.

However, one third or more of all hypodermic syringe needles sold never touch a patient directly, but are used only to pierce elastomeric closures on medicament injection sites, elastomeric vial stoppers, and the like. From a design point of view, these needles for "injection site" use have not been differentiated from needles intended for penetrating patient skin and tissue.

While the mortality rate from accidental stick- induced hepatitis and other disease is significant, and has a documented history of ov-ar forty years, it is AIDS that is now focusing the medical industry on ways to prevent medical workers from infection induced by accidental needle sticks. Accidental stick-induced infection from used needles is obvious, but even a new needle can be dangerous by acting as a hypodermic transport for infectious materials on the skin at the point of a needle stick. A National Institute of Health survey in 1987 estimated that more than 800,000 accidental needle sticks occur each year in the United States (almost one accidental stick per nurse per year) . The greatest percentage of such accidental sticks were recorded to occur during injection site use. Thus, health workers are at significant risk of injury and/or infection because they must use dangerously sharp "patient needles" to access injection sites, rather than instruments specifically designed to be safe. Numerous "anti-stick" devices have been proposed during the last twenty years. However, these all have sought to sheath or guard a sharp needle only after an injection to an injection site or patient. Also, all such devices have one or more of the following disadvantages: high cost, complexity of use, inability to prevent pre-injection sticks, and inability to prevent leakage of infectious materials after an injection.

Further, all antistick devices introduced prior to the present invention have required health worker retraining to exploit their safety features, a significant problem given the ingrained nature of needle use in the medical community. For example, in an effort to reduce accidental needle sticks resulting from needle recapping (the second most common source of sticks in the NIH study) , the Centers for Disease Control conducted retraining programs for nurses to change this habit. In spite of the high motivation of this group to avoid needle sticks, the post-training recapping rate (94%) was just as high as the pre-training rate. It has not been known until the present invention how to prevent accidental medical worker sticks during "injection site" injections, while also avoiding the need for health worker retraining and the other disadvantages recited above.

Summary of the Invention

The invention is a precisely shaped, but not sharp, hollow needle (referred to in this Specification as a "blunt" needle) capable of penetrating a resilient sealing member, such as an elastomeric injection site closure or an elastomeric vial stopper, while being highly resistant to accidental penetration of human skin or tissue. In a preferred embodiment, the inventive needle's hollow shaft has gauge in the range from 17 through 30, and has a closed, blunt end with a cross- section of from about 0.3 mm to about 1.2 mm, so that it will penetrate conventional injection site and vial closures, but will be roughly similar to a ball point pen in its ability to puncture human skin. In such closed end embodiment, the needle shaft has an opening spaced from -the closed end, providing fluid communication between the interior and exterior of the shaft.

The inventive needle is preferably designed so that no more than about 1.8 kg of force must be exerted on the needle to cause it to penetrate the most difficult type of injection site (typically a neoprene vial stopper) with which it will be used. The inventive needle may be treated to reduce friction between it and the injection site during insertion after penetration. This may be accomplished by siiiconizing the inventive needle (in the manner in which conventional hypodermic needles are currently siliconized) , or applying a fixed lubricant coating (such as teflon) to it.

The angle between the needle axis, and the axis of the hub on which the needle is mounted, may be selected so that medical workers may easily and accurately position the needle during use.

Preferably, an elastomeric sheath is mounted around the inventive needle, so that the needle will penetrate the sheath while advancing toward an injection site, and so that the sheath will reseal (so as to surround the needle) when the needle is retracted from the injection site following an injection, thus reducing the risk of infection due to fluid draining from the needle tip after the injection. The end portion (or "head") of such elastomeric sheath also provides additional protection to the health worker, because significant force must be applied to cause the blunt needle tip to penetrate the head (in some embodiments, the head may be as thick as a thin injection site) .

Brief Description of the Drawings

Figure 1 is a side cross-sectional view of a preferred embodiment of the inventive apparatus, including a needle surrounded by an elastomeric sheath. Figure 2 is a side elevational view of the needle of the Figure 1 apparatus, in a plane rotated by 90 degrees with respect to the plane of Figure 1.

Figure 3 is a side elevational view of another preferred embodiment of the inventive needle.

Figure 4 is a side elevational view of the Figure : needle, as viewed in plane rotated by 90 degrees about the needle's axis with respect to the plane of Figure 3 Figure 5 is a side elevational view of another preferred embodiment of the inventive needle. Figure 6 is side elevational view of the Figure 5 needle, as viewed in a plane rotated by 90 degrees about the needle's axis with respect to the plane of Figure 5.

Figure 7 is a side elevational view of a conventional injection site apparatus.

Detailed Description of the Preferred Embodiments

A first preferred embodiment of the invention will be described with reference to Figures 1 and 2. Needle 2 has a shaft portion 2a and a blunt, tapered tip 10. Tip 10 has tapered outer walls 12. Walls 12 are generally conical in the embodiments of Figs. 1 and 2. Needle 2 will typically be formed of metal having gauge in the range from 17 through 30, so that outer diameter C of shaft portion 2a will be in the range from about 0.3 mm to about 1.45 mm. Tip 10 is closed, and preferably has radius D in the range from about 0.15 mm to about 0.6 mm (where outer diameter C is in the range from about 0.3 mm to about 1.45 mm) .

Orifice 8 extends through needle 2 at a location spaced along the longitudinal axis of needle 2 from closed tip 10. Fluid may flow through orifice 8 into or out from the interior of needle 2. Although orifice 8 is shown to have an oblong shape in Figures 1 and 2, it is contemplated that orifice 8 may have any other shape, such as a circular shape.

In a preferred embodiment, the needle shown in Figures 1 and 2 is formed from 21 gauge metal tubing, so that outer diameter C is about 0.81 mm, and the thickness of shaft portion 2 's wall is about 0.125 mm. Length E of tip portion 10 is preferably about .60 mm, with the angle Y of side walls 12 in the range from about 21 to 22 degrees. Orifice 8 preferably has an axial length G of about 1.20 mm, a radial depth F of about .25 mm, and a sidewall angle Z equal to about 50 degrees. Orifice 8 is preferably spaced from tip portion 10 by an axial distance H of about .20 mm.

Resilient sheath 6 surrounds needle 2, so as to prevent fluid flow between the interior and exterior of the assembly comprising needle 2 and hub 4. Sheath 6 preferably fits tightly around shaft 2a of needle 2. Sheath 6 may be attached to end portion 4a of hub 4 in any conventional manner, such as by a layer of an adhesive substance (not shown in Fig. 1) . In the Figure 1 embodiment, hub end portion 4a is barbed and end portion 7 of sheath 6 is tightly fitted over barbed end portion 4a.

Throughout this specification, including in the claims, the phrase "injection site" will be used to denote any sealing member comprising an elastic portion capable of being pierced by a needle, and capable of automatically resealing upon withdrawal of the needle. Of course, any injection site capable of resealing when pierced by one type of needle may fail to reseal when pierced by another type of needle, and all injection sites will eventually lose their automatic resealing capacity after being pierced a sufficient number of times. The broad class of injection sites includes not only the assembly shown in Figure 8 (to be described below) , but also conventional vial, bottle, or blood collection container closures (such as rubber stoppers) . Commercially available injection sites have elastic sealing portions (or "plugs") formed of any of a wide range of materials (including natural rubber, butyl rubber, polychoroprene, ethylene propylene diene rubber, and silicone) , and having a wide range of durometers (typically from 30 to 65 SHORE A) and dimensions (from 4 mm outer diameter, with thickness of 2 mm, to 43 mm OD, with thickness of 10 mm) . As needle 2 presses end portion 6a of sheath 6 against an injection site, tip 10 of needle 2 will pierce (and completely penetrate) end portion 6a. After needle 2 penetrates portion 6a, needle 2 will continue to advance relative to sheath 6 as needle 2 penetrates the injection site, and sheath 6 will fold up on itself in collapsible-fashion as needle 2 so advances. Sheath 6 is selected to have an elastic "memory" such that, when needle 2 retracts after penetrating the injection site, sheath 6 will return to its original shape in which end portion 6a (and the remainder of sheath 6) prevents fluid flow between needle 2 and the surrounding medium. End portion 6a (alternatively denoted herein as "head" 6a) provides additional anti-stick protection to health workers, since significant force is required to cause needle tip 10 to penetrate head 6a.

The length of needle 2 between tip 10 and hub 4 will typically be in the range from 10 mm through 18 mm. Due to the variety of injection sites with which may be intended for use with needle 2, radius D and diameter C will be selected to be the largest that will allow all injection sites (with which needle 2 will forseeably be used) to reseal automatically after needle 2 pierces and withdraws therefrom. Preferably, radius D will be selected to be the largest radius which allows all injection sites (with which needle 2 will forseeably be used) to reseal automatically after up to about five penetrations by needle 2. Internal diameter I of needle 2 should be sufficiently large to permit adequate flow rates for all or most fluids (each fluid having, in general, a different viscosity) which will forseeably be caused to flow through needle 2.

It is within the scope of the invention to employ needle 2 without sheath 6. However, it is desirable to employ sheath 6 in order to reduce the risk not only of -8- pre-injection and post-injection accidental sticks, but also of post-injection contamination by body fluids that would otherwise drip from needle 2 (unless contained within sheath 6) . Conventional (sharp) needles for hypodermic injections that have an outer diameter of 0.8 mm (i.e., are formed from 21 gauge metal tubing) will penetrate the skin on calloused human fingertips at loads of as little as 11 grams. Skin areas less calloused than finger tips may be penetrated by such needles at significantly lower loads (sometimes as low as 4 g) . Once the skin is broken, infection can occur.

In the embodiment of the invention shown in Figure 1 and 2, when shaft portion 2a is formed from 21 gauge metal tubing (and radius D is about 0.3 mm and angle Y is about 22 degrees) , needle 2 will not puncture calloused human fingertips at loads in excess of 600 g, which represents a safety factor increase of about 60 fold relative to typical conventional hypodermic needles formed from 21 gauge metal (i.e., conventional "21G" hypodermic needles) . To provide adequate anti-stick protection to users of the invention, each embodiment of the inventive needle should be designed to require at least about 50 times more load force to penetrate human skin than does a conventional Becton Dickenson or

Sherwood 25G hypodermic needle (so that no embodiment of the invention will puncture calloused human fingertips at loads less than about 500 grams) .

The outer shaft diameter and tip radius of needle 2 in the Figure l embodiment (and the corresponding needle of each other embodiment of the invention) should be selected so that -the needle is capable of penetrating a wide range of commercially available injection sites at acceptable loads (i.e., loads of less than 1.8 kilograms) , while allowing the elastic material comprising each such injection site to reseal automatically upon removal of the inventive needle therefrom. The inventive needle may be treated to reduce friction between it and the injection site during insertion after penetration, such as by siliconizing the inventive needle (in the manner in which conventional hypodermic needles are currently siliconized) , or applying a fixed lubricant coating (such as teflon) to it. Such a silicone or fixed lubricant coating will reduce the loading force necessary for penetration of the needle through injection site elastomeric material, while not significantly reducing the loading force required for penetration of the needle through human skin. The 1.8 kilogram loading force design criterion set forth in the previous paragraph is a result of my research, which suggests that a force of about 1.8 kilograms is the perceived maximum force that hospital staff will willingly and safely exert to avoid use of a sharp needle. This criterion is appropriate for designing versions of the inventive needle for use with a wide range of conventional injection sites. Some injection sites, however, may excessively deform or fail (for example, due to separation of their elastomeric plugs from their housings) when subjected to load of 1.8 kg or more. When designing a version of the invention for use with such injection sites, the inventive needle's dimensions should be selected so that it will penetrate each such injection site with a load force of less than 1.8 kg.

The outer diameter of the inventive needle's shaft and blunt tip will preferably be selected to allow each injection site with which the needle will be used to reseal automatically after as many as five injections (each performed using the inventive needle) within a four hour period (where the injection site is at a temperature of 37 degrees C, and a pressure in the range from negative 500 mm Hg to positive 1000 mm Hg) , or as many as five injections within a 72 hour period (where the injection site is at room temperature, and a pressure in the range from negative 150 mm Hg to positive 200 mm Hg) .

It is important that the inventive needle be sufficiently long, and the side wall orifice (for example, orifice 8) of the closed end embodiments of invention be spaced sufficiently close to the needle tip (for example, tip 10) to allow the orifice to pass all the way through the elastomeric plug of each injection site with which the invention will forseeably be used. However, one advantage of the inventive needle design is that needles constructed in accordance with the invention will be shorter on the average than conventional hypodermic needles that have been used to pierce injection sites. Use of the inventive needle thus improves hand/eye coordination for needle point placement in the injection site context.

Additional advantages resulting from use of the invention include: less scraping of the inner walls of conventional plastic injection sites (which may lead to severing of plastic shards that can pass to the patient) ; and avoidance of "coring" of the injection site (greatly reducing the risk that elastomeric cores produced by the injection site needle will pass to the patient, and ensuring that resealing of the injection site will not be prevented by coring) .

In Figure 1, the longitudinal axis of needle 2 coincides with that of hub 4. However, rt is contemplated that needle 4 may alternatively be angled. Such an "angled needle" variation of the Figure 1 embodiment may be safer and easier to use by medical personnel for various applications. Thus, use of an angled needle may increase the operator's control over the accurate placement of the needle tip, and also reduce the risk that the operator will accidentally stick a co-worker while handling the needle. For example, if a needle having a 60 degree bend (so that its tip points in a direction rotated by 60 degrees relative to the axis of the hub to which it is attached) slips relative to the injection site when the operator applies a load thereto (in an attempt to push the needle tip through the injection site's elastic portion) the risk of accidental injury to the operator may be substantially less than in the case that a straight needle (such as the Figure 1 needle) is employed. Figures 3 through 6 show alternative preferred embodiments of the needle of the invention.

Needle 22 of Figures 3 and 4 has a blunt tip 20, as needle 2 of Figures 1 and 2 has a blunt tip 10. However, blunt tip 20 has a hemispherical profile, while tapered outer walls 12 of blunt tip 10 have a generally conical shape. The radius of hemispherical tip 20 is half the outer diameter, d, of the shaft of needle 22. In order for needle 22 to be capable of penetrating most conventional injection sites, vhile also being highly resistant to accidental penetration of human skin or tissue, the shaft's outer diameter, d, will be in the range from about 0.3 mm to about 1.45 mm.

Oval-shaped orifice 18 in the side wall of closed ended needle 22 provides fluid communication between the interior and exterior of needle 22. As shown in Figure 3, orifice 18 preferably has a radius of curvature substantially equal to the shaft's outer diameter, d. The length of needle 22 and the separation (along the longitudinal axis of needle 22) between orifice 18 and tip 20 should be selected so that orifice 18 will pass all the way through each injection site with which needle 22 will forseeably be used.

Needle 32 of Figures 5 and 6 is yet another preferred embodiment of the invention. Needle 32 has a spoon-shaped (spatulate) blunt tip 30. The thickness E and width F of tip 30 should be selected so that needle 32 is capable of penetrating the injection sites with which it will forseeably be used, while also being highly resistant to accidental penetration of human skin or tissue.

Oval-shaped orifice 28 in the side wall of closed ended needle 32 provides fluid communication between the interior and exterior of needle 32. As shown in Figure 5, orifice 28 preferably has a radius of curvature substantially equal to the needle shaft's outer diameter, d. The length of needle 32 and the separation (along the longitudinal axis o^* needle 32) between orifice 28 and tip 30 should be selected so that orifice 28 will pass all the way through each injection site with which needle 32 will forseeably be used.

Figure 7 is an example of a conventional injection site apparatus, with which the invention is designed to be used. The Fig. 8 apparatus includes needle 114 for penetrating the skin of a patient, reservoir 102 for storing fluid to be injected into the patient, tubing 106 connecting reservoir 102 with needle 114, and drip chamber 104 and clamp 112 for regulating the flow of the fluid supplied to needle 114. Injection site 100 is attached between an upper and a lower portion of tubing 106 _r so that fluid may flow from the upper and lower portions of tubing 106. Site 100 includes Y-shaped coupling member 108, and elastomeric plug 110. An injection site needle (which may be a conventional needle or the inventive needle) may be pressed downward against plug 110, to pierce plug 110 so that supplemental fluids may be injected through the injection site needle into the "primary" stream of fluid flowing from reservoir 102 to needle 114. Tubing 106 and site 100 are conventionally made of plastic. It is contemplated that the blunt tip of any of the embodiments of the inventive needle may be formed by cutting a tubular needle shaft to the desired length, and then closing and shaping the shaft's open end, such as by melting the open end and then cooling and forming the closed, molten end to the desired blunt shape as it cools. It may be preferable to crimp the shaft's open end (to reduce its outer radial dimension) after the cutting operation, but before the melting and forming operations. Alternatively, a separate blunt tip can be swaged or welded onto the cut end of the shaft, or a bead of molten metal, glass, or polymer may by applied to the cut end of the shaft to form the desired blunt tip.

In yet another embodiment, the blunt end of the inventive needle may be formed by crimping the cut shaft's open end (but not fully closing the open end), and then blasting or polishing the crimped end (or dipping it in a coating) to smooth its sharp edges. In this case, the blunt tip will .ιot strictly be closed, although the needle satisfies ^*;he design criteria for the invention (including the 1 8 kilogram maximum loading force criterion and the injection site coring avoidance criterion described above) . Instead, a small amount of fluid may flow through the relatively small passage through the blunt tip. However, the small passage through the blunt tip will not be relied upon to provide the desired fluid flow rate through the needle, and instead the above-described orifice in the needle's side wall (orifice 8 in Figures 1 and 2) will be provided, in addition to the small passage, for this purpose. Throughout this Specification, including in the claims, the phrase "closed, blunt end portion" (or variations thereon) is used to denote not only a strictly closed needle end, but also an almost-closed needle end of the type described above in this paragraph.

The foregoing is merely illustrative and explanatory of the invention. Various changes in the component sizes and shapes, and other details of the embodiments described herein may be within the scope of the appended claims.

Claims

What is claimed is:

1. An injection site needle, including: a hollow shaft, having a longitudinal axis and a closed, blunt end portion, and defining an orifice providing fluid communication between the interior and the exterior of the hollow shaft; wherein the shaft and the blunt end portion are dimensioned so as to be capable of penetrating an injection site but to be highly resistant to penetration of human skin or tissue.

2. The needle of claim 1, wherein the orifice is oval- shaped, and is separated from the blunt end portion by a first distance along the longitudinal axis.

3. The needle of claim 1, wherein the orifice is round- shaped, and is separated from the blunt end portion by a first distance along the longitudinal axis.

4. The needle of claim 1, wherein the blunt end portion has a hemispherical profile.

5. The needle of claim 1, wherein the blunt end portion has a spatulate profile.

6. The needle of claim 1, wherein the blunt end portion has tapered outer walls and a generally conical profile.

7. The needle of claim 1, wherein the hollow shaft has a first outer diameter and the blunt end portion has a radius, and the first outer diameter and the radius are selected so that the needle is capable of penetrating the injection site when a loading force of not more than 1.8 kilograms urges the needle against the injection site.

8. The needle of claim 1, wherein the needle will not puncture a calloused human fingertip when a loading force of 500 grams or less urges the needle against the fingertip.

9. The needle of claim 1, wherein the shaft has a first outer diameter in the range from about 0.3 mm to about 1.45 mm, and the blunt end portion has a radius in the range from about 0.15 mm to about 0.6 mm.

10. An injection site needle assembly, including: a hub member having a first longitudinal axis; a hollow needle, having a second longitudinal axis and a closed, blunt end portion, and defining an orifice providing fluid communication between the interior and the exterior of the needle, wherein the needle and the blunt end portion are dimensioned so as to be capable of penetrating an injection site but to be highly resistant to penetration of human skin or tissue; and an elastic sheath surrounding the needle and having a first end portion fixedly attached to the hub member, said sheath preventing significant fluid flow between the exterior of the needle and the medium surrounding the sheath and the needle.

11. The assembly of claim 10, wherein the sheath has a second end portion opposite the first end portion, said second end portion being sufficiently thin so that blunt end portion of the needle will pierce and completely penetrate the second end portion of the sheath as the needle presses the second end portion against the injection site. -17-

12. The assembly of claim 11, wherein the sheath has an elastic memory such that, after the needle penetrates the injection site and retracts away form the injection site, the sheath will automatically return to its original shape in which the sheath prevents fluid flow between the needle and the medium surrounding the needle and the sheath.

13. The assembly of claim 12, wherein the sheath is dimensioned so as to fold up on itself in collapsible- fashion while the needle penetrates the injection site.

14. The assembly of claim 10, wherein the orifice is oval-shaped and is separated from the blunt end portion by a first distance along the second longitudinal axis.

15. The assembly of claim 10, wherein the blunt end portion has a hemispherical profile.

16. The assembly of claim 10, wherein the blunt end portion has a spatulate profile.

17. The assembly of claim 10, wherein the blunt end portion has tapered outer walls and a generally conical profile.

18. The assembly of claim 10, wherein the hollow shaft has a first outer diameter and the blunt end portion has a radius, and the first outer diameter and radius are selected so that the needle is capable of penetrating the injection site when a loading force of not more than 1.8 kilograms urges the needle against the injection site.

19. The assembly of claim 10, wherein the needle will not puncture a calloused human fingertip when a loading force of 500 grams or less urges the needle against the fingertip.

20. The assembly of claim 10, wherein the needle has a first outer diameter in the range from about 0.3 mm to about 1.45 mm, and the blunt end portion has a radius in the range from about 0.15 mm to about 0.6 m .

21. The assembly of claim 10, wherein the sheath and the needle are fixedly mounted on the hub member with the first longitudinal axis substantially parallel to the second longitudinal axis.