Self-dilating cannula

1. A self-dilating cannula assembly for introduction into a patient's vasculature, comprising:

a stylet comprising a distal end;

a cannula, comprising:

an elongate body, the elongate body having a proximal end, a distal end, and a fluid-flow lumen extending therebetween, wherein the fluid-flow lumen is the only longitudinally-extending lumen defined in the cannula; and

an atraumatic tip positioned at the elongate body's distal end, the atraumatic tip having a blunted nose and a conical shape, wherein the atraumatic tip comprises a plurality of axially elongate fluid-flow openings on a conical portion of the atraumatic tip proximal to the blunted nose and configured to disperse fluid from the fluid-flow lumen in a plurality of directions with respect to the atraumatic tip, and wherein the atraumatic tip further comprises an opening in the blunted nose sized to a guidewire;

an external concentric stop slideable along the elongate body, the stop including a locking mechanism for holding the stop in place on the elongate body for controlling a degree of insertion of the distal end of the self-dilating cannula into a patient's vasculature; and

an obturator, comprising a lumen sized to receive the stylet, wherein the obturator is configured to reduce fluid flow through the fluid-flow lumen during introduction of the cannula into a blood vessel, the obturator sized to slide within the fluid-flow lumen from the proximal end towards the distal end of the fluid-flow lumen, wherein the obturator and stylet are sized to provide an interference fit between the distal end of the stylet and an inside surface of a distal end of the obturator, wherein the interference fit is configured to control an amount of stylet insertion into the obturator.

2. The self-dilating cannula assembly of claim 1 , wherein the distal end of the stylet comprises an incising end, wherein the opening of blunted nose is sized to the stylet.

3. The self-dilating cannula assembly of claim 2 , wherein the stylet is configured to provide a predetermined shape to the elongate body when inserted therein.

4. The self-dilating cannula assembly of claim 2 , wherein the stylet is configured to provide stiffness to facilitate insertion in a vessel lumen.

5. The self-dilating cannula assembly of claim 1 , further comprising a reinforcing element configured to provide increased stiffness to the elongate body.

6. The self-dilating cannula assembly of claim 5 , wherein the reinforcing element comprises a wire.

7. The self-dilating cannula assembly of claim 5 , wherein the reinforcing element comprises a spring.

8. A self-dilating cannula assembly for introduction into a patient's vasculature, comprising:

a stylet comprising an incising end;

a cannula, comprising:

an elongate body, the elongate body having a proximal end, a distal end, and a fluid-flow lumen extending therebetween, wherein the fluid-flow lumen is the only longitudinally-extending lumen defined in the cannula; and

an atraumatic tip positioned at the elongate body's distal end, the atraumatic tip having a blunted nose and a conical shape, wherein the atraumatic tip comprises a plurality of fluid-flow openings proximal to the blunted nose and configured to disperse fluid from the fluid-flow lumen in a plurality of directions with respect to the atraumatic tip, and wherein the atraumatic tip further comprises an opening in the blunted nose sized to a guidewire, wherein the atraumatic tip is configured to dilate an incision in a wall of a blood vessel when advanced therethough, wherein the incision is the size of the incising end of the stylet, and wherein the incising end of the stylet is capable of being inserted through the opening in the blunted nose;

an external stop disposed concentrically around the elongate body, wherein the stop is slideable along the elongate body and includes a locking mechanism for holding the stop in place on the elongate body for controlling a degree of insertion of the distal end of the self-dilating cannula into a patient's vasculature; and

an obturator, comprising a lumen sized to receive the stylet, wherein the obturator is configured to reduce fluid flow through the fluid-flow lumen during introduction of the cannula into a blood vessel, the obturator sized to slide within the fluid-flow lumen from the proximal end towards the distal end of the fluid-flow lumen, wherein the obturator and stylet are sized to provide an interference fit between the incising end of the stylet and an inside surface of a distal end of the obturator, wherein the interference fit is configured to control an amount of stylet insertion into the obturator.

9. The self-dilating cannula assembly of claim 8 , wherein the fluid-flow openings are on a conical portion of the atraumatic tip.

10. The self-dilating cannula assembly of claim 8 , wherein the fluid-flow openings are sized and oriented to allow blood to smoothly flow along a direction of a longitudinal axis of the elongate body.

11. The self-dilating cannula assembly of claim 8 , wherein the fluid-flow openings are aligned in a plurality of longitudinally spaced rows and are aligned in a plurality of circumferentially spaced columns on the atraumatic tip.

12. A self-dilating cannula assembly for introduction into a patient's vasculature, comprising:

a stylet comprising a distal end;

a cannula, comprising:

an elongate body, the elongate body having a proximal end, a distal end, and a fluid-flow lumen extending therebetween, wherein the fluid-flow lumen is the only longitudinally-extending lumen defined in the cannula; and

an atraumatic tip positioned at the elongate body's distal end, the atraumatic tip having a blunted nose and a conical shape, wherein the atraumatic tip comprises a plurality of axially elongate fluid-flow openings proximal to the blunted nose and configured to disperse fluid from the fluid-flow lumen in a plurality of directions with respect to the atraumatic tip, wherein the axially elongate fluid-flow openings are sized and oriented to allow blood to smoothly flow along a direction of a longitudinal axis of the elongate body, and wherein the atraumatic tip further comprises an opening in the blunted nose sized to a guidewire; and

an obturator, comprising a lumen sized to receive the stylet, wherein the obturator is configured to reduce fluid flow through the fluid-flow lumen during introduction of the cannula into a blood vessel, the obturator sized to slide within the fluid-flow lumen from the proximal end towards the distal end of the fluid-flow lumen, wherein the obturator and stylet are sized to provide an interference fit between the distal end of the stylet and an inside surface of a distal end of the obturator, wherein the interference fit is configured to control an amount of stylet insertion into the obturator.

13. The self-dilating cannula assembly of claim 12 , the distal end of the stylet comprising an incising end, wherein the opening of blunted nose is sized to the stylet, wherein the atraumatic tip is configured to dilate an incision having a diameter of the stylet.

14. The self-dilating cannula assembly of claim 13 , wherein the stylet has a diameter of about 0.038 inches and the atraumatic tip is configured to dilate an incision having a diameter of about 0.038 inches.

15. The self-dilating cannula assembly of claim 12 , wherein the axially elongate fluid-flow openings are both longitudinally and circumferentially spaced along the atraumatic tip.

16. The self-dilating cannula assembly of claim 12 , wherein the axially elongate fluid-flow openings are arranged in at least three longitudinally spaced rows on the atraumatic tip.

17. The self-dilating cannula assembly of claim 12 , wherein the axially elongate fluid-flow openings are axially aligned in at least one column on the atraumatic tip.