A cannula assembly for insertion in a blood vessel includes a cannula and a dilator. The cannula has a proximal end, a distal end, and a lumen extending therebetween. The dilator, which is telescopically received in the lumen of the cannula, includes proximal and distal ends, a passage extending between the proximal and distal ends, and a dilator tip disposed at the distal end. The cannula assembly further includes a needle and a guide wire disposed within the passage of the dilator. The dilator tip has an opening formed therein for receiving one of the needle and guide wire. The dilator tip is configured to limit insertion of the needle in the blood vessel.