Cannula and method for bidirectional blood flow

A cannula assembly comprising in combination:

• a bifurcated cannula hub;
• a first hollow cannula mounted upon the leading end of the bifurcated cannula hub and projecting forwardly thereof a first distance;
• a second hollow cannula telescopically disposed within the first, the leading end of the second cannula projecting beyond the leading end of the first cannula and the trailing end of the second cannula being attached to a spaced rigid coupling member so as to be in direct axial alignment with one branch of the bifurcated cannula hub;
• means for fixing the position of the spaced coupling with respect to the rigid hub;
• the second branch of the bifurcated coupling defining a hollow flow path which flow path intersects the interior of the first hollow cannula within the rigid hub;
• a venipuncture needle, the trailing end of which is secured to a reciprocating shuttle member, the leading end of the needle being reciprocably disposed within the rigid cannula hub and telescopically circumscribing the second cannula;
• and
• means accommodating displacement of the needle and shuttle from a first position in which the shuttle is in a forward position adjacent the rigid cannula hub and the needle is interposed between the first and second cannulae and projecting forward of the first cannula so as to accommodate venipuncture and a second position wherein the shuttle is rearwardly displaced into engagement with the spaced coupling thereby withdrawing the needle from within the first cannula and removing its obstructing presence from the intersecting flow path whereby blood can be simultaneously conveyed in one direction through the first hollow cannula and in the opposite direction through the second hollow cannula.

A method of introducing a double lumen cannula into the cardiovascular system of a patient, the double lumen cannula comprising a branched hub with a first and second cannula, each of said cannulae being interiorily hollow, the method comprising the steps of:

• connecting one branch of the cannula hub to an extracorporeal fluid circuit and connecting another branch of the cannula to the extracorporeal fluid circuit;
• interposing a stylet needle through the hollow of a first cannula, the stylet needle being interiorily hollow and having a trailing end mounted in a shuttle member;
• initially concealing a second smaller diameter cannula telescopically within the hollow of the stylet needle;
• simultaneously introducing both the first and second cannulae into the cardiovascular system of a patient without disconnecting the cannula hub from the extracorporeal blood circuit;
• and
• displacing the stylet needle away from the leading ends of the first and second cannulae and within the cannula hub by grasping the shuttle member and displacing the shuttle member a limited distance along the axis of the second cannula.

A double lumen cannula assembly for use in a cardiovascular system of a patient comprising in combination:

• a hollow hub;
• a first lumen mounted in the hub to define a flow path to a first extracorporeal line;
• a second lumen mounted in the hub to define a flow path to a second extracorporeal fluid line, a portion of said second lumen being essentially coextensible within the distal end of the first lumen;
• a needle telescopically disposed within the first lumen and projecting therebeyond, said needle being disposed around the second lumen so as to facilitate essentially concurrent introduction of the first and second lumens into the cardiovascular system;
• and
• means for retracting the needle a limited distance along the axis of the second lumen away from said distal end such that the sharp end of the needle is retained in the hub, said displacing means accommodating venipuncture without interrupting communication of the flow paths of the first and second lumen to the respective extracorporeal fluid lines.