A treatment of inserting a catheter such as a balloon catheter and a guiding catheter or a lead wire of a cardiac pacemaker into a blood vessel is performed by using an indwelling needle assembly (see e.g. Patent Document 1) and a sheath introducer. The indwelling needle assembly includes an outer needle and an inner needle inserted into the outer needle. The sheath introducer includes a sheath and a dilator inserted into the sheath.
In general, an indwelling needle assembly in which an outer needle and an inner needle are assembled together (a needlepoint of the inner needle projects from the tip of the outer needle) is inserted into a blood vessel such as a femoral artery. The inner needle is next withdrawn from the outer needle to indwell only the outer needle. A guide wire is inserted into the inside of the blood vessel through the outer needle. A sheath introducer in which a sheath and a dilator are assembled together is inserted onto the guide wire, introduced into the blood vessel and advanced to a desired position. Thereafter, the dilator and the guide wire are withdrawn to indwell the sheath in position. Thus, the inside of the blood vessel can directly be accessed from outside of the body of a patient through the sheath. This makes it possible to introduce catheters of various types or the lead wire of the cardiac pacemaker into the blood vessel via a sheath.
The indwelling needle assembly (puncture device) mentioned above is needed to give small damage to a blood vessel at the time of puncture and to easily catch the blood vessel. It is thus preferred that the inner needle and the outer needle are as thin as possible (have respective small outer diameters).
However, if a needle tube is made thin, its strength is reduced to become yielding, deteriorating puncture performance (accessibility of a needlepoint to a target site of a living body). In other words, the resistance of skin, subcutaneous fat, muscle tissue or the like deforms the needle tube, which makes it impossible for the needlepoint to reach a targeted blood vessel. In particular, if a puncture is made to an artery located deep in the living body, such a defect appears dominantly and high frequently.
The needlepoint of the inner needle which has caught the blood vessel can be confirmed by visually observing the inflow (flashback) of blood into an inner hub provided at the proximal end of the inner needle. If the inner needle is made thin to reduce its inner diameter, a time difference increases between an actual puncture of the needlepoint into the blood vessel and the confirmation of the flashback. This may make it probable not to accurately and quickly recognize catch of the blood vessel.
At the time of confirming the flashback, usually the inner needle and outer needle are slightly advanced (based on a sense or experience of an operator, the inner and outer needles are slightly advanced in a delicate distance). This determines that the tip of the outer needle has been inserted into the inside of the blood vessel. However, the late flashback has a bad influence on the operation of advancing the inner and outer needles in a delicate distance. For instance, the inner needle may be inserted too deep so that it injures the opposite side of the blood vessel or impales the blood vessel.
To quickly recognize the flashback, a puncture device 100 including an inner needle 104 with the so-called different diameters as shown in FIG. 6 has been devised as below. The inner needle 104 includes a small diameter portion 142, a large diameter portion 144 and a tapered intermediate portion 143. The small diameter portion 142 is located on the proximal end side of the needlepoint 141. The large diameter portion 144 is located closer to the proximal end than the small diameter portion 142 and has inner and outer diameters greater than those of the small diameter portion 142. The intermediate portion 143 is located between the small diameter portion 142 and the large diameter portion 144 so as to be formed to alleviate the changes in the inner and outer diameters of the small and lager diameter portions 142, 144.
The puncture device 100 shown in FIG. 6 is such that the inner needle 104 is inserted into the lumen of an outer needle 102 and a needlepoint 141 is most projected from the distal opening of the outer needle 102. In this case, the puncture device 100 has a significant gap between the outer needle 102 and the inner needle 104 (the small diameter portion 142) in a portion L3 where the outer needle 102 covers the small diameter portion 142 of the inner needle 102. The outer needle 102 easily moves on the small diameter portion 142 of the inner needle 104; therefore, when the puncture device 100 is inserted into skin, the outer needle 102 does not follow the inner needle 104, which causes a phenomenon in which only the outer needle 102 is pushed back from the surface of the skin. If the puncture device 100 is forcibly pushed in without change, the outer needle 102 collapses and outwardly rises at a position close to the intermediate portion 143 of the inner needle 104, as shown in FIG. 7. After the outer needle 102 has risen, if the puncture device 100 is further forcibly pushed in, significant puncture resistance is produced to increase the load of the operator and the patient.
Patent Document 1: Japanese Patent Laid-Open No. 2001-112871