Dynamic cannula
A perfusion cannula constructed of a wire mesh or other structure having an expandable portion capable of expanding from a constricted state to an expanded state such that a vessel is stented open while permitting fluid flow through a cannula into the vessel.
1. An expandable cannula having a first state having a constricted diameter and a second state having an expanded diameter for at least a portion of its length, said cannula comprising:
a tube comprising a material that enables the diameter along at least a portion of its length to increase radially from the first state to the second state, said tube having
i) a wall enclosing a lumen;
ii) a proximal end; and
iii) a distal end;
wherein the wall of at least a portion of the tube of the cannula in the second state gradually flares from the constricted diameter to the expanded diameter at an angle of up to 20 degrees from a central axis of the tube to form a funnel shape.
2. The expandable cannula of claim 1 , wherein at least a portion of said tube is fluid impermeable coating.
3. The expandable cannula of claim 1 , wherein at least a portion of said tube is at least partially fluid permeable.
4. The expandable cannula of claim 1 , wherein at least a portion of the inside of said tube is coated with a first coating and at least a portion of the outside of said tube is coated with a second coating.
5. The expandable cannula of claim 1 , further comprising a joining of expandable materials at one end.
6. The expandable cannula of claim 1 , further comprising an end cap.
7. The expandable cannula of claim 6 , wherein the end cap is solid.
8. The expandable cannula of claim 6 , wherein the end cap has an opening defined therein.
9. The expandable cannula of claim 1 , wherein the tube of the cannula in the second state gradually tapers from the expanded diameter to a smaller diameter.
10. The expandable cannula of claim 1 , wherein said tube is self-expanding.
11. The expandable cannula of claim 1 , wherein said tube expands in response to a mechanical force.
12. The expandable cannula of claim 1 , wherein said tube contracts in response to a mechanical force.
13. The expandable cannula of claim 1 , wherein said tube expands in response to an electrical stimulus.
14. The expandable cannula of claim 1 , wherein said tube contracts in response to an electrical stimulus.
15. The expandable cannula of claim 1 , wherein said tube expands in response to a thermodynamic stimulus.
16. The expandable cannula of claim 1 , wherein said tube contracts in response to a thermodynamic stimulus.
17. The expandable cannula of claim 1 , wherein the material comprises a mesh material.
18. The expandable cannula of claim 1 , wherein the material comprises a biodegradable material.
19. The expandable cannula of claim 1 , wherein the wall of at least a portion of the tube of the cannula in the second state gradually flares from the constricted diameter to the expanded diameter at an angle of up to about 7 degrees from the central axis of the tube.
20. The expandable cannula of claim 1 , wherein said flared portion, when positioned within a vessel having an internal wall having a diameter, substantially expands to said internal wall diameter.
21. The expandable cannula of claim 1 , wherein the material of at least a portion of said tube comprises a wire mesh material.
22. A method of stenting a vessel while permitting fluid flow, the method comprising:
a. providing an expandable cannula of claim 1
b. inserting said expandable cannula through an opening in said vessel;
c. permitting said cannula to expand from the first state to the second state; and
d. permitting fluid to flow through said tube.
23. A method of cannulating a vessel, the method comprising:
a. providing an expandable cannula of claim 1 ;
b. providing a trocar having a proximal end and a distal end;
c. inserting said trocar into said tube so that said trocar distal end contacts at least a portion of said wall of said tube at the distal end;
d. introducing said tube and trocar into a vessel; and
e. permitting said cannula to expand from the first state to the second state, thereby cannulating the vessel.
24. A blood vessel access kit, comprising:
a. a needle;
b. an actuator comprising an elongated member; and
c. an expandable cannula of claim 1 .
25. The expandable cannula of claim 1 , wherein said material comprises a shape memory material.
26. The expandable cannula of claim 1 , wherein said material comprises a metal, ceramic, or polymer.
27. The expandable cannula of claim 1 , wherein said material comprises nitinol or stainless steel.
28. The expandable cannula of claim 1 , wherein an inner side of said wall comprises grooves or ribs.
29. The expandable cannula of claim 1 , wherein the flared portion of the wall flares in a straight line.
30. The expandable cannula of claim 1 , wherein the flared portion of the wall flares in a curved line.
31. The expandable cannula of claim 1 , wherein the gradual flare provides a decrease in exit velocity of fluid passing through the cannula compared to a cannula of the same constricted diameter without the funnel shape.
32. The expandable cannula of claim 1 , wherein the wall flares from the distal end towards the proximal end.
33. The expandable cannula of claim 1 , wherein the wall flares from the proximal end towards the distal end.
34. The expandable cannula of claim 1 , further comprising a trocar having a diameter sized to fit within said tube and attached to a distal end of the tube.
35. The method of claim 23 , wherein permitting said cannula to expand from the first state to the second state comprises removing said trocar such that said cannula tube radially expands to said second state.
36. The method of claim 23 , wherein permitting said cannula to expand from the first state to the second state comprises leaving the trocar in place and releasing a temporary attachment of the proximal end of the tube to a proximal end of the trocar such that said cannula tube radially expands to said second state.