The assembly comprises: a stand for hanging a container of a main liquid, a spike, to be introduced into the container of main liquid, a multi-inlet connector with inlet tubings, to be connected to containers of additional liquids and to the container of main liquid through the spike, and an outlet tubing to be connected to a luer syringe to be introduced into a patient. The length of the spike inlet tubing of the connector has a length determined for, during use of the assembly with a container of main liquid, keeping the connector hung up on the stand through the spike and the container of main liquid. Thanks to the invention, the problem of the tubing traffic is solved.