1. Patient's posture: The patient's posture affects the exposure of femoral artery, which ensures that the patient lies flat on the operating table and makes the femoral artery more accessible.

2. Puncture site: The selection and preparation of puncture site will affect the placement of cannula, ensure the skin of puncture site to be clean, and use appropriate puncture needle and cannula.

3. Sleeve size: The size of the sleeve does not match the diameter of the patient's femoral artery, so it is necessary to choose a sleeve with a suitable size to ensure the successful placement of the femoral artery.