A cannula-needle for intravenous injection has a tubular body (9) adapted to house thereinside the needle (5) of a catheter (1) and having a peripheral wall (10) extending along a longitudinal direction (L) with a predetermined length (1) form an open proximal end (11) adapted to be anchored to the connection element (3) of the catheter (1) to a distal end (12) tapered and provided with a hole (13) for the partial exit of the needle (5). The peripheral wall (10) comprises at least one pair of elongated passages (15, 15) substantially longitudinal e diametrically opposite to each other, each having a minimum dimension (d) of the order of the tenths of millimeters and between 1/3 and 1/7 of the maximum diameter (ID) of the distal hole (13) and a overall longitudinal extension (e) higher than the 50% of the predetermined length (1) of the peripheral wall (10) to define a respective section for the fluid flow having overall area (At) close to the area of the distal hole (13) and for obtaining a uniform distribution of the supplied flow along the longitudinal extension of the tubular body (9) with a total flow rate (Qt) having increased value.
