Nursing procedures
Conventional saline test injection was conducted with the following procedures. (1) As per the instructions, the Y-type 18 G indwelling needle was connected to a disposable pressure extension tube at one end, and the lumen was filled with normal saline. Afterward, the indwelling needle was inserted into the right median cubital vein of patients. (2) After lid removal and disinfection, the normal saline and contrast agent bottles were respectively connected to the NaCl cylinder and the CA1 or CA2 cylinder of the high-pressure injector (CT injector, XD 2000, Mississippi ™). (3) Air in the NaCl cylinder, CA1 or CA2 cylinder, and connecting tube was evacuated successively, after which the heparin cap at one side of the disposable pressure extension tube was removed and the pressure extension tube was connected to the distal end of the connecting tube. Then, we ensured that each part was firmly connected and no air bubbles existed within all tubes. (4) Patients lay in the scanning bed and positioned. Afterward, the Y-type 18 G indwelling needle in the elbow was connected to the high-pressure injector and 15–20 mL normal saline was injected 1–2 times at a flow rate of 2 mL/s to ensure the fluent injection for the following CTA examination [
Diagram for the conventional saline test injection Notes: ① The high-pressure injector; ② The external tube of the high-pressure injector; ③ The connection between the external tube and the disposable pressure extension tube of the high-pressure injector; ④ The disposable pressure extension tube; ⑤ The connection between the disposable pressure extension tube and the Y-type indwelling needle; ⑥ The unconnected outlet of the Y-type indwelling needle; ⑦ The clipping switch for the Y-type indwelling needle; ⑧ The entry of the Y-type indwelling needle into the human body. In the conventional saline test injection, the injection can be conducted after connection in ③ and the open of the clip switch in ⑦Modified saline test injection was performed. Specifically, the initial operations were the same as the 1–3 steps of the conventional saline test injection. After the completion of step 3, the patient lay in the scanning bed and was positioned. Next, the 18 G indwelling needle in the elbow was clipped, whose disposable pressure extension tube was then connected to the high-pressure injector. Liquids (20–30 mL) were drained out of the unconnected outlet (to exhaust the probably generated air in the tubes during connection) with the use of the three joint design of the indwelling needle. After drainage, the heparin cap was used to close the drainage outlet and the clipped 18 G indwelling needle was opened. Subsequent to all of the aforesaid operations, saline test injection (15–20 mL normal saline was injected 1–2 times at a flow rate of 2 mL/s) was conducted to ensure the fluent injection of normal saline, followed by CTA examination (Fig. 
Diagram for the modified saline test injection Notes: ① The high-pressure injector; ② The external tube of the high-pressure injector; ③ The connection between the external tube and the disposable pressure extension tube of the high-pressure injector; ④ The disposable pressure extension tube; ⑤ The connection between the disposable pressure extension tube and the Y-type indwelling needle; ⑥ The unconnected outlet of the Y-type indwelling needle; ⑦ The clipping switch for the Y-type indwelling needle; ⑧ The entry of the Y-type indwelling needle into the human body; ⑨ The three joint design of the Y-type indwelling needle utilized for liquid drainage out of the unconnected outlet. In the modified saline test injection, the injection can be conducted after connection in ③, the close of the clip switch in ⑦, the open of the unconnected outlet in ⑥, and the operation in ⑨