JP2003339878A - Inverted taper-shaped cannula - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverted taper-shaped cannula capable of increasing the drawing-out resistance without damaging a rubber elastic body in insertion and without using a special locking means after insertion, being easily operated, and being applied even to a cock for medical treatment having a short length from an inlet to a switching passage. <P>SOLUTION: This cannula 1 used when the drug solution is injected to a side injection tool or a mixing injection tool having the inlet connected to a fluid infusion line and made of a rubber elastic body, is configurated by a blunt needle 2 having the inverted taper 4 of which an outer diameter is gradually reduced from a tip part to a basic end part, and a connecting part 3 formed on a knife lure extended from a basic end of the blunt needle 2 in the shape of stepped shaft, and communicated to an inner cavity of the blunt needle 2, a tip of the blunt needle is closed, and a side hole 6 is formed on a side wall of the tip closed part 5. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cannula used for temporarily or continuously injecting a medicinal solution into a side injection tool or a mixed injection tool whose injection port connected to an infusion line is made of a rubber-like elastic material. In particular, the present invention relates to a reverse taper type cannula which does not damage the rubber-like elastic body at the time of insertion and can increase pull-out resistance after insertion.

[0002]

2. Description of the Related Art A medicinal solution is temporarily or continuously injected into a side infusion tool or a mixed infusion tool connected to an infusion line with a rubber-like elastic body called a septum for preventing infection from the injection port. In this case, a cannula with a blunt needle tip is used from the viewpoint of prevention of needle stick accidents by medical staff.

However, when inserting such a cannula into the rubber-like elastic body of the injection port, it is necessary to consider the backward movement of the cannula due to the repulsive force from the rubber-like elastic body so that the medical staff can carry out the injection operation with peace of mind. There is. Therefore, various techniques have been proposed to prevent the backward movement of the cannula due to the repulsive force from the rubber-like elastic body.

For example, in Japanese Examined Patent Publication No. 5-32071 (hereinafter referred to as a first conventional example), a side hole is provided in a side wall of a tip closing portion of a cannula whose tip is closed, and the cannula extends from the tip closing portion to the base side. The outer surface of the intermediate section is formed in a cylindrical shape parallel to the axis to reduce kickback when inserting the cannula into a rubber-like elastic body, or the base side of the blunt needle of the cannula with an open tip. An annular hump is provided on the outer peripheral surface of the junction between the area and the tapered area on the tip side, thereby increasing the pulling force and preventing the inadvertent removal of the cannula from the rubber-like elastic body. ing.

Further, in Japanese Unexamined Patent Publication No. 2002-17853 (hereinafter referred to as a second conventional example), a spherical convex portion is provided on the outer surface of a blunt needle of a puncture tube, that is, a cannula. A spherical space is formed in the slit of the rubber-like elastic body so that the convex portions can match, or a spherical convex portion is provided on the outer periphery of the tip of the blunt needle of the cannula, whereby the blunt needle of the cannula is attached to the rubber-like elastic body. It is disclosed that the cannula is locked so as not to come off, and at the same time, the cannula can be positioned with respect to the rubber-like elastic body.

Further, in Japanese Patent No. 2584994 (hereinafter, referred to as a third conventional example), the piercing means is formed in a stepped shaft shape in which the outer diameter is gradually increased, and the outer peripheral surface of the second step from the tip is formed. A reverse taper is formed in which the proximal end side is reduced in diameter (minimum diameter), and the cylindrical first step of the piercing means (in this conventional example, the tip is formed into a sharp needle) is pierced. A port connector having a membrane having a diameter substantially the same as that of the membrane is provided with a peripheral wall extending rearward from the membrane, and the peripheral wall comes into contact with the reverse taper portion of the second stage when the piercing means is pierced. By doing so, it is disclosed that the piercing means is prevented from coming off from the port connector.

By the way, a rubber-like elastic body for preventing infection is provided at the injection port, and it has a function of switching the injection route such as injection of the main drug solution or side injection or mixed injection, and the drug solution is temporarily or long-term injected into the infusion line. In the case of a medical stopcock used for blood sampling from an arterial line or the like, the distance from the injection port to the switching path is long, and if there is a dead space, it may be necessary to administer a small amount of drug solution in one shot. In addition, there is a problem that the drug solution, etc. stays in the mouth and it is not possible to administer the drug sufficiently, and when another drug solution is added and administered, it mixes with the drug solution retained in the dead space, and There is the problem that in some cases there may be serious risks. Therefore, the present applicant has proposed a medical stopcock having a small dead space with a short distance from the injection port to the switching path and a cannula having a short blunt needle that can be used therefor (Japanese Patent Laid-Open No. 11-94).
No. 103 gazette: hereinafter referred to as a fourth conventional example). The blunt needle of the cannula of the fourth conventional example is formed in a taper type in which the tip is opened and the outer diameter is reduced toward the tip, or a side hole is provided in the side wall of the tip opening. .

In addition to the above-mentioned fourth conventional example, the one having a side hole at the tip of the cannula is, for example, Japanese Patent Application Laid-Open No.
No. 002-17856 (hereinafter referred to as a fifth conventional example)
Are disclosed in. The cannula of the fifth conventional example is formed in a long taper type in which the distal end of the needle tube is closed and the outer diameter is reduced toward the distal end portion, and a side hole is formed in the side wall of the distal end closed portion. It is provided.

[0009]

However, the above-mentioned conventional examples have the following problems. That is, in the case of the first conventional example, the intermediate region of the cannula is formed in a cylindrical shape parallel to the axis line, and in a normal state, the elastic force of the rubber-like elastic body acts only in the radial direction (tightening direction) of the cannula, and The component force is not generated in the backward direction to reduce kickback when inserting the cannula.However, since the frictional force between the cannula cylindrical part and the rubber-like elastic body is large, the rubber is not easily inserted when the cannula is inserted. When the contact portion of the elastic body with the cannula is pulled in the cannula insertion direction (axial front direction) and the pushing force is released after the insertion is completed, the return force of the rubber elastic body and the friction force cause the cannula to return to its original position. Is inevitable. Therefore, the length of the cannula must be set long so that the side hole of the distal end closed portion is not blocked by the backward movement of the cannula for the pulling, from the injection port to the switching path as in the fourth conventional example. Not applicable to medical stopcocks with short distances. Further, it is undeniable that the annular hump on the outer surface of the blunt needle may damage the rubber-like elastic body when inserting the cannula into the rubber-like elastic body. Furthermore, in the case where the tip of the blunt needle is open, the rubber-like elastic body may be damaged by the edge of the tip opening when inserting the cannula into the rubber-like elastic body. If a small piece of rubber-like elastic material is produced due to damage to the body, it is quite possible that the rubber-like elastic material may flow into the body through the infusion line, and in the worst case, a serious medical accident may occur. There is a nature.

Further, the spherical projection on the outer surface of the blunt needle in the second conventional example cannot be denied that the rubber-like elastic body may be damaged when the cannula is inserted into the rubber-like elastic body. further,
In this second conventional example, since the blunt needle tip is open,
When inserting the cannula into the rubber-like elastic body, the rubber-like elastic body may be damaged at the edge of the tip opening, and when the rubber-like elastic body is actually damaged and a small facet of the rubber-like elastic body is generated. It is quite possible that the rubber-like elastic facets flow into the body through the infusion line, and in the worst case, a serious medical accident may occur.

Further, in the case of the third conventional example, since the first cylindrical step of the piercing means for piercing the membrane is formed as a sharp needle having an open tip, the cannula is inserted into the membrane. At this time, there is a high possibility that the membrane will be damaged. Furthermore, since the distance from the sharp tip of the cannula to the stepped portion at the base of the sharp needle is as long as about 10 mm or more, this cannula has a distance from the injection port to the switching path as in the above-mentioned fourth conventional example. When it is used for a short medical stopcock and is inserted into the rubber-like elastic body of the inlet up to the stepped portion to stabilize the cannula, the tip of the cannula hits the switching passage, possibly damaging the cannula or the switching passage. Then, it is quite possible that the resulting chips enter the body together with the drug solution via the infusion line, and in the worst case, the blood vessel may be blocked and a serious medical accident may occur. Furthermore, when the diameter of the reverse taper portion of the second step is as large as 0.508 to 0.5588 cm and this reverse taper portion is used by being penetrated through the rubber-like elastic body of the medical stopcock as in the above-mentioned fourth conventional example. In addition to the need to increase the diameters of the inlet and the rubber-like elastic body, the distance from the inlet to the switching path must be secured, which inevitably causes a dead space.

Further, in the case of the cannula of the fourth conventional example, since the blunt needle is formed in a taper type in which the tip has a reduced diameter, the cannula is caused by the repulsive force from the rubber-like elastic body when it is inserted into the rubber-like elastic body. A locking means for preventing the backward movement tends to be required, and the structure of the entire cannula tends to be complicated. Further, similarly to the above-mentioned first and second conventional examples, since the blunt needle tip is open, the rubber-like elastic body is damaged at the edge of the tip opening portion when the cannula is inserted into the rubber-like elastic body. There is a possibility that, like the first to third conventional examples described above,
At worst, it can lead to serious medical accidents.

Further, in the case of the fifth conventional example, since the tip of the cannula is closed, there is little possibility of damaging the rubber-like elastic body, but since it is formed in a long taper taper type, 4 It cannot be applied to a stopcock for medical use where the distance from the inlet to the switching path is short, as in the conventional example.

The technical problem of the present invention is that the rubber-like elastic body is not damaged at the time of insertion and the pull-out resistance can be increased after insertion without using any special locking means. It is also applicable to medical stopcocks that have a short distance to the switching path.

[0015]

A reverse taper type cannula according to claim 1 of the present invention has the following structure. That is, a cannula used when injecting a drug solution into a side infusion tool or a mixed infusion tool in which an injection port connected to an infusion line is made of a rubber-like elastic body, wherein the cannula has an outer diameter from a distal end portion to a proximal end portion. Is provided with a blunt needle formed in a reverse taper with a reduced diameter, and a connecting portion formed in a female luer extending from the base end of the blunt needle in a stepped shaft shape and communicating with the lumen of the blunt needle, wherein the blunt needle is The tip is closed, and a side hole is provided in the side wall of the tip closing portion.

Further, in the inverted taper type cannula according to claim 2, the length of each of the specifications of the blunt needle from the tip to the proximal stepped portion which is the boundary with the connecting portion is 8 mm or less, and Maximum outer diameter is 2.5 mm or less, inner diameter is 0.5 mm or more, base end wall thickness is 0.25 mm or more, reverse taper angle is 0.25 ° to 4 °
It is set in the range of.

Further, in the inverse tapered cannula according to claim 3, the maximum outer diameter of the inverse tapered portion is set to be smaller than the maximum outer diameter of the tip portion, and the transition from the maximum outer diameter portion of the tip portion to the inverse tapered portion is performed. It is configured such that a step portion is formed in the portion.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 shows the first of the present invention.
2 is a plan view showing the entire structure of the inverted taper cannula according to the embodiment of the present invention, FIG. 2 is an enlarged plan view showing a blunt needle part which is a main part thereof, FIG. 3 is a sectional view showing the whole structure, and FIG. Sectional drawing showing an example of use in a medical stopcock with a short distance from the injection port to the switching path, FIGS. 5 and 6 are explanatory views of various specifications of the blunt needle portion, and FIG. 7 is drawing with respect to the reverse taper angle. It is a graph which shows the experimental result of the relationship between the resistance and the blunt needle proximal end side wall thickness. The reverse taper angle θ of the blunt needle shown in FIG. 2 is larger than the actual one for convenience of explanation.

In FIGS. 1 to 3, reference numeral 1 denotes a cannula made of synthetic resin, which is composed of a blunt needle 2 at the tip and a connecting portion 3 extending rearward from the base end of the blunt needle 2.

On the outer peripheral surface of the blunt needle 2, an inverse taper 4 whose outer diameter is reduced from the tip to the base is formed, and the tip is closed, and the side wall of the tip closing portion 5 is formed. A rectangular side hole 6 is provided.

The connecting portion 3 is formed in a female lure extending rearward from the base end of the blunt needle 2 in a stepped shaft shape, and has a lumen 7 of the blunt needle 2.
Has lumens 8 and 9 communicating with.

The inverted taper type cannula of this embodiment having the above-described structure can be used for the medical stopcock 10 having a short distance from the inlet to the switching path shown in FIG. The stopcock for medical use 10 has a bottomed cylindrical body in which a main body 11 is integrally formed with branch pipes 12, 13 and 14 branched in three directions on its side wall. The branch pipes 12 and 13 are provided such that their inner cavities are aligned with each other through the chamber portion 15 of the main body 11 and form a main route through which the main drug solution (infusion) flows. An inlet 16 is formed at the end of the branch pipe 12, and a discharge port 17 is formed at the end of the branch pipe 13. A valve body 18 is rotatably installed in the chamber portion 15, and the injection route of the chemical liquid is switched by operating the valve body 18 with an operation lever (not shown) extending outward from the valve body 18. You can do it. In addition, the branch pipe 14 has an inner lumen thereof
It is provided so as to be equidistantly arranged at an angle of 90 ° between Nos. 2 and 13, and a mixed injection port 19 is formed at the end thereof.
Rubber-like elastic body 21 for preventing infection inside 9
Are fitted to form a side-injection route for side-injection.

The rubber-like elastic body 21 is made of a synthetic rubber material such as natural rubber or isopropylene rubber having a thickness in the axial direction of at most about 5 mm, and a slit 22 penetrating in the axial direction is provided at the center thereof. At the same time, the lower surface, that is, the liquid contact surface, is formed with an arcuate surface 23 for providing repeated puncture durability, and the peripheral edge of the arcuate surface 23 is formed in a double cylinder shape on the proximal end side in the branch pipe 14. It is inserted into the annular protrusion 24 and is constantly compressed inward in the radial direction. In addition,
Reference numeral 25 is a lock ring for fastening with the port connector on the other side to which the medical stopcock 10 is attached.

Such an injection port (here, mixed injection port 19)
In order to enable use in the medical stopcock 10 having a short distance from the chamber portion 15 to the switching path, the inverted taper cannula of the present embodiment has the main specifications of the blunt needle 2 set as follows. ing. That is, the length A (FIG. 5) from the tip to the proximal stepped portion 26 which is the boundary with the connecting portion is 8 mm or less, the maximum outer diameter D1 (FIG. 5) of the tip is 2.5 mm or less, and the inner diameter D2 ( 6) is 0.5 mm or more, the thickness T of the base end portion (FIG. 6) is 0.25 mm or more, and the inverse taper angle θ (FIG. 2) is 0.
It is set in the range of 25 ° to 4 °.

The grounds for setting the specifications of the blunt needle 2 are as follows. Length A: 8 mm or less Insert the blunt needle 2 into the injection port of the medical stopcock 10 (here, mixed injection port 1
9) Rubber-like elastic body 21 (axial thickness of slit part: 5
mm), the side hole 6 of the blunt needle 2 is completely opened and blunted in the chamber portion 15 when the proximal end stepped portion 26 is inserted until it abuts the outer end surface of the rubber-like elastic body 21. The tip of the needle 2 (closed portion 5) should not hit the valve body 18. Maximum outer diameter of the tip D1: 2.5 mm or less Can be inserted into the injection port (here, mixed injection port 19: inner diameter 4.2 mm) of the stopcock 10 for medical use, and the tip should not be easily broken when a load is applied. . Inner diameter D2: A sufficient flow rate of 0.5 mm or more is obtained, and excessive pressure is not applied to the fingertip when administering the drug solution from the cannula 1 using a syringe. Thickness of base end T: 0.25 mm or more The base end should not easily break (break) when a load is applied. Inverse taper angle θ: 0.25 ° to 4 ° The above conditions must be satisfied, and a significant increase in pull-out resistance can be expected. Note that the pull-out resistance of the cannula 1 from the rubber-like elastic body 21 is indicated by the line B (-in FIG. 7).
(Indicated by-), the angle increases depending on the reverse taper angle. Therefore, the larger the reverse taper angle, the more difficult it is for the cannula to be pulled out, which is advantageous. On the other hand, in order to increase the angle of the reverse taper, due to the restrictions on the length A and the maximum outer diameter D1 of the tip portion, the line C (-) in FIG.
(Indicated by □-), the wall thickness of the base end must be reduced, and if the wall thickness of the base end becomes 0.25 mm or less, the risk of breakage due to stress concentration on the base end increases. Will end up. For this reason, the upper limit of the reverse taper angle is 4 °. If the reverse taper angle is smaller than 0.25 °, the reverse taper may not be formed at all due to the characteristics of the material used and manufacturing errors. It was set at 25 °.

A drawing B of the pull-out resistance with respect to the inverse taper angle in FIG. 7 is obtained by plotting the average values of the experimental results of the samples 1 to 3 shown in Table 1 below.

[0027]

[Table 1]

In this experiment, a model (specimen 1 to specimen 3) in which the length A of the needle portion is set to 8 mm and the inverse taper angle θ is set to 0 °, 2 °, 5 °, and 8 °, respectively, is prepared. After being inserted into the rubber-like elastic body 21 of the medical stopcock 10 as shown in FIG. 5, the mechanical resistance value at that time was measured by pulling it out with a tensile tester.

As is clear from Table 1, the average value of the specimen 1, the specimen 2, and the specimen 3 shows that the inverse taper angle is 0 °.
The increase in pull-out resistance between ~ 2 ° is particularly significant, about 2.
You can see that it is 0 times. However, even at 2 ° or more, the pull-out resistance increases depending on the increase in the inverse taper angle. For example, it can be seen that when the inverse taper angle is 5 °, it is about 2.6 times as large as 0 °, and when it is 8 °, it is 3.3 times.

As described above, in the reverse taper type cannula of this embodiment, the outer diameter of the blunt needle 2 whose length can pass through the rubber-like elastic body 21 is reduced from the distal end to the proximal end. Since the reverse taper 4 is formed, the tip thereof is closed, and the side wall 6 of the tip closed portion 5 is provided with the rectangular side hole 6, the rubber-like elastic body 21 is not damaged during insertion, and After insertion, the blunt needle 2 can be urged in the insertion depth direction by the component force by utilizing the repulsive force from the rubber-like elastic body 21 without using any special locking means.
The pullout resistance can be increased. Therefore, during use, the blunt needle 2 is slit 22 until the proximal stepped portion 26 of the blunt needle 2 contacts the outer end surface of the rubber-like elastic body 21.
It only needs to be inserted inside, the operation is simple, and it can be used for a medical stopcock having a short distance from the inlet to the switching path.

Embodiment 2. FIG. 8 is an enlarged plan view showing a blunt needle portion which is a main part of an inverted taper cannula according to a second embodiment of the present invention. In the figure, the same as that of the first embodiment described above, or Corresponding parts are designated by the same reference numerals. Here, the reverse taper angle of the blunt needle is set larger than the actual one for convenience of explanation.

In the reverse taper type cannula of the second embodiment, the maximum outer diameter of the reverse taper 4 portion of the blunt needle 2A is set to be smaller than the maximum outer diameter of the tip portion, and the reverse taper is applied from the maximum outer diameter portion of the tip portion. The difference from the above-described first embodiment is that a step portion 31 is formed at the transition portion to the portion, and all other configurations are the same as those in the above-described first embodiment.

In the second embodiment, the step portion 31 at the tip of the blunt needle, which is the penetrating end from the rubber-like elastic body 21 (see FIG. 4), acts as an anchor, so that, for example, the rubber-like elastic body 21 in the axial direction. Even when the thickness is thin and an increase in pull-out resistance due to the inverse taper 4 cannot be expected, the step portion 31 engages with the edge of the slit 22 in the arc surface 23 that is the liquid contact surface of the rubber-like elastic body 21, and functions as a stopper. The backward movement of the cannula 1 can be reliably prevented.

In each of the above-described embodiments, the stopcock for medical treatment having a short distance from the injection port to the switching path has been described as an application example of the present invention, but the present invention is not limited to this, and it is not limited to the conventional medical stopcock. It goes without saying that it can also be used as a stopcock as it is, and by using the plug 40 as shown in FIGS. 9 and 10, it is possible to connect to various infusion lines and the versatility can be expected to be expanded.

[0035]

As described above, according to the invention of claim 1, the cannula has a blunt needle formed in an inverse taper whose outer diameter decreases from the distal end portion to the proximal end portion, and the base of the blunt needle. A blunt needle was formed with a connecting part formed in a female luer extending in a stepped axis from the end and communicating with the inner lumen of the blunt needle, and the tip of the blunt needle was closed, and a side hole was provided in the side wall of the tip closed portion. Therefore, the rubber-like elastic body is not damaged during insertion, and no special locking means is used after the insertion, and the repulsive force from the rubber-like elastic body is used to insert the blunt needle by the component force. It was possible to urge in the lateral direction and increase the pull-out resistance.

Further, according to the invention of claim 2, the length of each of the specifications of the blunt needle is 8 mm or less from the tip to the base end stepped portion which is a boundary with the connecting portion, and the outermost portion of the tip is outside. Diameter is 2.5mm
Below, the inner diameter is 0.5 mm or more, and the wall thickness of the base end is 0.25 mm
As described above, since the reverse taper angle is set in the range of 0.25 ° to 4 °, when using, the blunt needle is inserted until the proximal end stepped portion of the blunt needle contacts the outer end surface of the rubber-like elastic body. It is simple and easy to operate, and can be used as a stopcock for medical treatment where the distance from the inlet to the switching path is short.

According to the invention of claim 3, the maximum outer diameter of the reverse taper portion is set smaller than the maximum outer diameter of the tip portion,
Since the step portion is formed at the transition portion from the maximum outer diameter portion of the tip portion to the inverse taper portion, the step portion 31 acts as an anchor, and thus the rubber elastic body 21 has a small axial thickness, for example. Even when the pulling resistance due to the reverse taper 4 cannot be expected to increase, even when the step portion can be made to act as an anchor and the axial thickness of the rubber-like elastic body is thin, and the pulling resistance due to the reverse taper cannot be expected to increase. ,
It was possible to reliably prevent the backward movement of the cannula.

[Brief description of drawings]

FIG. 1 is a plan view showing the overall configuration of an inverted taper cannula according to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view showing a blunt needle portion which is a main portion of the inverted taper cannula according to the first embodiment.

FIG. 3 is a cross-sectional view showing the overall configuration of the inverted taper cannula according to the first embodiment.

FIG. 4 is a cross-sectional view showing an example of use of the inverted taper cannula according to the first embodiment in a medical stopcock having a short distance from an inlet to a switching path.

FIG. 5 is an explanatory diagram of respective specifications of the blunt needle portion of the inverted taper cannula according to the first embodiment.

FIG. 6 is an explanatory diagram of respective specifications of the blunt needle portion of the inverted taper cannula according to the first embodiment.

FIG. 7 is a graph showing the experimental results of the relationship between the pull-out resistance and the blunt needle proximal end side wall thickness with respect to the reverse taper angle of the reverse taper cannula according to the first embodiment.

FIG. 8 is an enlarged plan view showing a blunt needle portion which is a main portion of an inverted taper cannula according to a second embodiment of the present invention.

FIG. 9 is a plan view showing another example of use of the inverted taper cannula according to the present invention.

10 is an enlarged cross-sectional view of a main part of FIG.

[Explanation of symbols]

1 cannula 2,2A blunt needle 3 connection 4 Reverse taper 5 Tip closing part 6 side holes 7 Blunt needle lumen 10 Medical stopcock (side or mixed injection device) 19 Mixed injection port (injection port) 21 Rubber-like elastic body 26 Base end stepped part 31 steps 40 plugs (side or mixed injection) A Length of blunt needle Maximum outer diameter of D1 blunt needle tip D2 blunt needle inner diameter T Thickness of blunt needle base end θ Reverse taper angle

Continued front page    (72) Inventor Nobufumi Fujiwara             5 27-7 Sendagaya, Shibuya-ku, Tokyo Sun             Book Brunswick Building Japan Shaw             Do Co., Ltd. (72) Inventor Nobuaki Suzuki             5 27-7 Sendagaya, Shibuya-ku, Tokyo Sun             Book Brunswick Building Japan Shaw             Do Co., Ltd. F term (reference) 4C066 AA10 BB01 CC01 DD06 FF01                       FF10 JJ10 LL30

Claims (3)

[Claims] 1. A cannula used when injecting a drug solution into a side infusion tool or a mixed infusion tool in which an injection port connected to an infusion line is made of a rubber-like elastic body, wherein the cannula is a distal end portion to a proximal end portion. A blunt needle formed in a reverse taper whose outer diameter is reduced over the length, and a connecting portion formed in a female luer extending in a stepped shaft shape from the base end of the blunt needle and communicating with the inner lumen of the blunt needle. The inverted taper type cannula, wherein the blunt needle has a closed tip, and a side hole is provided in a side wall of the closed portion of the tip. 2. The blunt needle has a length from a tip thereof to a proximal stepped portion which is a boundary with a connecting portion of 8 mm or less, a maximum outer diameter of the tip portion of 2.5 mm or less, and an inner diameter of 0.5 mm or more. , The thickness of the base end is 0.25 mm or more, and the inverse taper angle is 0.25 ° to 4 °
The inverse taper type cannula according to claim 1, wherein the inverted taper cannula is set in the range of. 3. The maximum outer diameter of the reverse taper portion is set smaller than the maximum outer diameter of the tip portion, and a step portion is formed at the transition portion from the maximum outer diameter portion of the tip portion to the reverse taper portion. The inverted taper type cannula according to claim 2, wherein