There are two types of indwelling needles according to the way of blood return, one is the steel needle of the indwelling needle has a cut, when the steel needle pierced the blood vessel, the blood will flow down the inside of the syringe and out of the cut, then you can see the blood inside the hose outside the steel needle, this type of needle has Europe and the United States BD, BB, and the domestic brand of indwelling needles, these companies, you see the return of the blood, it only means that the blood from the syringe passes through the inside of the syringe, can't Ensure that the hose enters the inside of the blood vessel. Generally, after the steel needle is pierced into the blood vessel, the puncture angle is lowered to within 20° (recommended by the Japanese Nursing Association), and then the needle is advanced 1~2mm on one side while the steel needle is withdrawn.
The second type is a steel needle with a blood return groove (similar to the blood release groove of cold weapons), this kind of needle is produced by Japanese manufacturers, and the needle is inserted at an angle of 15~20°, when you see blood flowing out of the hose, it means that the hose has already entered the blood vessel (this design is that the blood flows out of the gap between the outer surface of the steel needle and the inner surface of the hose), and at this time, you can just pull out the steel needle and send the cannula at the same time.
The above is to determine the relationship between the blood return and the success of the puncture, Chinese hospitals with indwelling needles of this generation are mostly with pigtails (Shanghai region called), is with extended catheter, generally like Jiangsu, Zhejiang and Shanghai around the tertiary hospitals in the nurses are in accordance with the individual operating habits of the needle.
Pinch steadily in order to hit the accurate, understand the design principle of the needle on the operation should be of some use.
I hope this helps.