A catheter instrument (1000) comprising: a catheter connector (200), a needle unit (300) and a protection of the tip of a needle of plastic (100) wherein said needle unit (300) is provided with a connecting means (301) for connection to dichoconector catheter (200), a connecting means (302) for connection to an external device, and is fijadoalrededor the rear end of a needle (303), said needle unit (300) further one agujahueca (303) with a needle (304) comprising the hollow needle (301) having an expansion region (305) being close of the needle tip (304) wherein said catheter connector (200) is connected to a catheter (201), said needle (303) extending longitudinally within said catheter (201) wherein said instrument catheter (1000) is in a modopreparado and said needle unit (300) is connected to said catheter hub (200) wherein said protection device the tip of a plastic needle (100) is installed within delconector catheter (200) and said needle (303) when said instrument catheter (1000) is in a modopreparado comprising said protection device the needle point (100): a body with a ladoposterior (106), a front side (107), an outer surface (108) connecting said rear side (106) and said ladofrontal (107), a hole (102) extending from said back side (106) to said front side (107), hole (102) through which runs said needle (303) and an elastic arm (103) extending in deunión point (105) from said front side (107) of said body, wherein said spring arm (103) has a dereposo state, from which can be pushed by said hollow needle (303) wherein said elastic arm (103) is pushed to give free passage through said hole (102) in axial unadirección of said body through said needle (300) when said instrument catheter (1000) is in elmodo prepared from so that said resilient arm (103) tends to move towards its rest state when hollow laaguja (303) is withdrawn to a point where the tip of the needle (304) passes a point of contact between elastic elbrazo (103) and the needle (303), so that a
