Abstract:
Disclosed is a cannula including a first circumferential portion, a second circumferential portion, and a seal with a first clamping surface. The first circumferential portion and the second circumferential portion are configured to mutually cooperate to support a circumference of vasculature, and form a second clamping surface. The first clamping surface and the second clamping surface are configured to cooperate to secure an end of the vasculature.

Description:
BACKGROUND 
     I. Related Technical Fields 
     Related technical fields include cannulas and clamping methods, and more specifically, cannulas and clamping methods for perfusing one or more organs to monitor, treat, sustain and/or restore the viability of the organ(s) and/or for transporting and/or storing the organ(s). 
     II. Related Art 
     Various devices have been developed that couple the anatomy of an organ being perfused to a machine or other equipment. Such devices are typically referred to as perfusion clamps or simply cannulas. Although the term cannula in general use has other meanings, the term cannula is used generically throughout the specification to refer to a clamp or other device that provides a connection through which a fluid flow may be established. 
     A type of cannula as described in U.S. Pat. No. 5,728,115 to Westcott et al., which is hereby incorporated by reference, is shown in  FIGS. 1-3 . A clamping device (cannula)  10  is used to couple the perfusion cannula to the renal aorta  34 . The clamp  10  includes two longitudinal members  12  and  14  which pivot about a pin  16 . The proximal end of the member  12  includes an integral handle  18 , while the proximal end of the member  14  includes an integral handle  20 . The distal end of the member  12  includes an elongated, hollow, annular, integral clamp head  24 , while the distal end of the member  14  includes an elongated, hollow, annular, integral clamp head  26 . Clamp head  26  includes a nipple  28  attached thereto. Movement of the handles  18  and  20  toward one another forces the members  12  and  14  to pivot about the pin  16 , thereby forcing the clamp heads  24  and  26  of the members  12  and  14  away from one another. A spring  22  is positioned between the handles  18  and  20  in order to bias the handles apart. This, in turn, tends to force the clamp heads  24  and  26  together. Therefore, the clamp heads  24  and  26  of the distal ends of the members  12  and  14  are engaged in a clamping relationship unless an external compressive force is applied to the handles  18  and  20 . A lumen  32  extends through the nipple  28 . 
     In use, the clamp  10  is attached to the renal aorta  34  of a donor organ such as a kidney  36  by opening the clamp  10 , passing the distal end  38  of the renal aorta  34  through the annular clamp head  24 , holding the distal end  38  of the renal aorta  34  over the annular clamp head  24 , and releasing pressure on the handles of the clamp  10  in order to allow the clamp head  26  to engage the distal end  38  of the renal aorta  34  against the annular clamp head  24 . A catheter  40  may then be attached to the nipple  28  in order to provide perfusion of liquid through the lumen  32  and into the renal aorta  34   
     U.S. Patent Application Publication No. 2004/0111104 to Schein et al., which is hereby incorporated by reference, discloses another type of cannula. 
     SUMMARY 
     The cannulas as described above require the use of an aortic patch also known as a Carrel patch, or cuff. An aortic patch is a section of the aorta that remains attached to the organ when the organ is removed from an organ donor. The aortic patch is used to facilitate cannulation of vasculature of the donated organ. An aortic patch is typically only available from a deceased donor because of the resultant damage to the aorta required for an aortic patch. As such, the cannulas described above suffer from a problem in that they are not suitable for use with organs, such as a kidney, donated from a living donor or organs where an aortic patch is otherwise not available. With such an organ, the amount of tissue available for cannulation is much less. Care must be taken not to damage the limited amount of tissue available when attaching a cannula so that adequate tissue remains to reconnect the organ when the organ is transplanted to the recipient, and to prevent damage that could result in loss of the organ. 
     Exemplary implementations of the broad inventive principles described herein provide a cannula that can be used without an aortic patch. Exemplary implementations provide a cannula with a first circumferential portion, a second circumferential portion; and a seal with a first clamping surface. The first circumferential portion and the second circumferential portion are configured to mutually cooperate to support a circumference of vasculature and form a second clamping surface. The first clamping surface and the second clamping surface are configured to cooperate to secure an end of the vasculature. These exemplary implementations provide a solution to problems and disadvantages discussed above because the exemplary implementations do not require an aortic patch and only engage a minimal amount of tissue. 
     Exemplary implementations of the broad inventive principles described herein provide a method of cannulating vasculature of an organ. The method includes enclosing a circumference of the vasculature with a first circumferential portion of a cannula and a second circumferential portion of the cannula to support the vasculature while maintaining a capability to flow liquid through the vasculature. The method includes contacting an end of the vasculature with a sealing portion of the cannula in a manner that maintains the capability to flow liquid through the vasculature to ensure a substantially leak free condition during perfusion. These exemplary implementations provide a solution to problems and disadvantages discussed above because the exemplary implementations do not require an aortic patch and only engage a minimal amount of tissue. 
     Exemplary implementations of the broad inventive principles described herein provide a cannula with an optically clear portion configured to allow a user to view at least one portion of an interior of vasculature and a seal when the cannula is in a position in which an end of the vasculature is secured by the cannula. The optically clear portion provides optical magnification of the artery in relation to its position in the cannula. These exemplary implementations provide a solution to problems and disadvantages discussed above because they allow for inspection of the vasculature for damage and proper connection while cannulated. The magnification may also allow the clinician to observe for trapped air bubbles or clots, or to observe the intima of the artery for damage. Also, these exemplary implementations require less tissue from the vasculature to be used because the tissue can be readily viewed in the cannula to confirm that the cannula is properly connected. Thus, excess tissue does not need to be used in order to confirm that the tissue is properly cannulated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary implementations can be described with reference to the following figures wherein: 
         FIGS. 1-3  illustrate a cannula of the prior art; 
         FIG. 4  illustrates a cannula in an open state; 
         FIG. 5  illustrates a cannula in a closed state; and 
         FIG. 6  illustrates a cross section of a cannula in a closed state. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Preservation of organs by machine perfusion has been accomplished at hypothermic temperatures with or without computer control with crystalloid perfusates and without oxygenation. See, for example, U.S. Pat. Nos. 5,149,321, 5,395,314, 5,584,804, 5,709,654 and 5,752,929 and U.S. patent application Ser. No. 08/484,601 to Klatz et al., which are hereby incorporated by reference. 
     Ideally organs would be procured in a manner that limits their warm ischemia time to essentially zero. Unfortunately, in reality, many organs, especially from non-beating heart donors, are procured after extended warm ischemia time periods (i.e. 45 minutes or more). The machine perfusion of these organs at low temperature has demonstrated significant improvement (Transpl Int 1996 Daemen). Numerous control circuits and pumping configurations have been utilized to achieve this objective and to machine perfuse organs in general. See, for example, U.S. Pat. Nos. 5,338,662 and 5,494,822 to Sadri; U.S. Pat. No. 4,745,759 to Bauer et al.; U.S. Pat. Nos. 5,217,860 and 5,472,876 to Fahy et al.; U.S. Pat. No. 5,051,352 to Martindale et al.; U.S. Pat. No. 3,995,444 to Clark et al.; U.S. Pat. No. 4,629,686 to Gruenberg; U.S. Pat. Nos. 3,738,914 and 3,892,628 to Thome et al.; U.S. Pat. Nos. 5,285,657 and 5,476,763 to Bacchi et al.; U.S. Pat. No. 5,157,930 to McGhee et al.; and U.S. Pat. No. 5,141,847 to Sugimachi et al., which are hereby incorporated by reference. 
     The cannulas and clamping methods described herein may be used in conjunction with apparatus and methods described in U.S. Pat. Nos. 6,014,864, 6,183,019, 6,241,945 and 6,485,450 to Owen, which are hereby incorporated by reference. While these apparatus and methods are related to organ recovery and transplantation, the cannulas and clamping methods described herein may also be used in various other medical procedures and with various other medical equipment where clamping with fluid flow is desired. Thus, the cannulas and clamping methods described herein are not limited to the applications described below in conjunction with the exemplary implementations. 
       FIG. 4  shows a perfusion clamping apparatus or cannula  100  according to a first exemplary implementation. The cannula  100  is capable of connecting one or more arteries of an organ to a perfusion machine or system (not shown), for example, by connection to tubing of the perfusion machine or system. All medical fluid contact surfaces are preferably formed of or coated with materials compatible with the medical fluid used, preferably non-thrombogenic materials. 
     The medical fluid for perfusion may be any suitable medical fluid. For example, it may be a simple crystalloid solution, or may be augmented with an appropriate oxygen carrier. The oxygen carrier may, for example, be washed, stabilized red blood cells, cross-linked hemoglobin, pegolated hemoglobin or fluorocarbon based emulsions. The medical fluid may also contain antioxidants known to reduce peroxidation or free radical damage in the physiological environment and specific agents known to aid in tissue protection. Further, the medical fluid may also include blood or blood products. 
     The cannula  100  is shown in  FIG. 4  in an open condition and in  FIG. 5  in a closed condition. In the open condition, a first circumferential portion  110  and a second circumferential portion  120  are rotated away from one another on a first hinge  150 . The first and second circumferential portions are rotated into contact with one another to form a second clamping surface  134  (described later). When vasculature is disposed between the first circumferential portion  110  and second circumferential portion  120  in such a closed condition, the circumference of the vasculature is supported. A fastening structure  140  secures the first circumferential portion  110  and the second circumferential portion  120  in this closed condition. The fastening structure  140  can be achieved in numerous ways. In the figures, the fastening structure  140  is shown as a releasable snap fit, but other fastening structures, such as a strap or tie will have similar effect. When a releasable snap fit is used, the cannula can be reopened without breaking so that the vasculature can be trimmed or repositioned. 
     Although the first circumferential portion  110  and the second circumferential portion  120  are shown as rotatably connected at the first hinge  150 , other methods of connection are contemplated by the broad inventive principles described herein. For example, at least one of the first circumferential portion  110  and the second circumferential portion  120  could be unattached before closure, and then snap fitted to the other of the first circumferential portion  110  and the second circumferential portion  120 . Alternatively, first circumferential portion  110  and the second circumferential portion  120  could translate on pins or rails. Many implementations of relative movement between these two parts are within the broad inventive principles described herein. 
     Both of the first circumferential portion  110  and the second circumferential portion  120  include a tapered portion  190 . As shown in  FIG. 6 , the tapered portion  190  is narrower in diameter than the cylindrical space  200  formed between the first circumferential portion  110  and the second circumferential portion  120 . The tapered portion  190  helps to secure the vasculature, but should not excessively constrict fluid flow through the vasculature. To allow adequate fluid flow within the vasculature, the tapered portion  190  may constrict an outer diameter of the vasculature up to about twelve percent. 
     After the vasculature is supported between the first circumferential portion  110  and the second circumferential portion  120 , a seal  130  is brought into contact with an end of the vasculature. This can be achieved by rotating a chamber portion  160 , via a second hinge  152 , into a closed position (as shown in  FIG. 5 ), which will bring the seal  130  into contact with an end of the vasculature. In this closed position, the first clamping surface  132  and the second clamping surface  134  secure and end of the vasculature. The complementary conical surfaces of a first clamping surface  132  and the second clamping surface  134  secure the end of the vasculature in a manner that allows free flow of liquid to an interior of the vasculature. Of course, other implementations of movement that secure the end of the vasculature are within the broad inventive principles described herein. 
     Free flow to and from an interior of the vasculature can be achieved by a flow passage  136 . The flow passage  136  may be a circular hole through the seal  130 , which may also be circular. The shape of the seal  130  and flow passage  136  are not limited to being circular, and may be influenced by other design considerations. 
     The seal  130  may be made of an elastomeric material. This will help to prevent damage to the vasculature, particularly an interior of the vasculature, which may be more susceptible to damage than an exterior of the vasculature. The shore A hardness (also known as the durometer) of the seal  130  can be chosen to be within a range of not less than about 32 and not greater than about 70 or within any smaller range therein, such as, preferably not less than about 60 and not greater than about 65. As used herein, the term “about” is intended to account for inherent manufacturing tolerances and inaccuracy in measurement. The hardness may be further tailored within or outside of these ranges depending upon the needs of the vasculature to be cannulated. Seals  130  of various hardness and/or seals  130  with different sizes of the flow passage  136  may be included with the cannula  100  to form a kit that can be used with different vasculatures. 
     The seal  130  is mated with a first opening (not labeled) in a chamber  162  of the chamber portion  160 . The flow passage  136  allows liquid communication from the vasculature to the chamber  162 . The chamber portion  160  also includes a second opening  166  and a third opening  168  in fluid communication with the chamber. The second opening  166  and the third opening  168  provide a “lateral” fluid flow, i.e., a flow of fluid that is substantially perpendicular to the direction of fluid flow to and from the tissue to which the cannula is attached. For example, the one or more fittings of the cannula are oriented to have an axis of fluid flow that is substantially perpendicular to an axis of fluid flow into/out of the flow passage  136 . This “lateral” fluid flow arrangement allows the cannula to be connected to tubing of an organ transporter, for example, that is substantially in a single plane, for example, as described in U.S. Pat. No. 7,678,563 and U.S. Patent Application Publication No. 2004/0221719, both of which are hereby incorporated by reference. Further, multiple cannulas may be connected and even interconnected within substantially the same plane. 
     One or both of the second opening  166  and the third opening  168  may be connected to a fitting utilized for priming and/or air bubble removal. A second fitting  107  comprises a port or valve for such purpose. The second opening  166  and the third opening  168  may be may also be used to network multiple cannulas, for example, by connecting tubing in parallel, for example, by running a split infuse line to the first fitting of each cannula, or in series, for example, by connecting the first fitting of a cannula to the second fitting of another cannula. Standard luer geometry or other suitable structure may be used for the fittings. 
     The chamber portion  160  may include an optically clear portion  170 . The optically clear portion  170  allows for visual inspection of the interior of the cannula. This is particularly advantageous in that it allows a user to inspect the clamping of vasculature within the cannula and to inspect for other things such as damage to the vasculature or bubbles within or flowing through the cannula. The optically clear portion may provide optical magnification to allow the user to see more detail of the vasculature, which can be relatively small, perhaps three to seven millimeters in diameter. 
     As shown in  FIG. 4 , both the first circumferential portion  110  and the second circumferential portion  120  include a surface  220  that is outside a diameter of the second clamping surface  134  and is approximately perpendicular to a circumference of a vasculature that is supported within the first circumferential portion  110  and the second circumferential portion  120 . This surface includes serrations and/or knurls  180 . Such serrations and/or knurls  180  may be included to secure additional tissue of the vasculature. Although the cannula  100  is fully operational when securing vasculature without an aortic patch, the surface  220  and serrations and/or knurls  180  cooperate with corresponding structure (not labeled) on the chamber portion  160  to optionally secure an aortic patch. Thus, exemplary implementations of the broad inventive principles described herein provide for a cannula that can be used with or without an aortic patch. For example, when a kidney is cannulated, significant portions of the renal artery may or may not be present. Thus, the cannula  100  can be effectively used in either situation. 
     The serrations and/or knurls  180  may also be included on the second clamping surface  134 . Preferably, there are no serrations and/or knurls on the first clamping surface  132  because the first clamping surface  132  may contact an interior of the vasculature, which is more susceptible to damage. The relatively soft elastomeric material of the seal  130  (and therefore of the second clamping surface  132 ) will help to prevent damage to the interior surface of the vasculature. The length of the seal that enters the intima of the artery is minimized, therefore minimizing damage to the inside of the artery. 
     A notch  210  may also be included in one or both of the first circumferential portion  110  and the second circumferential portion  120 . Four such notches are shown in  FIG. 4 . Each notch  210  may be used to secure sutures or side branches of the vasculature. The sutures may be attached to the side branches. 
       FIG. 5  includes two posts  230 . These posts may be used to anchor one or more straps that wrap around the cannula  100  to fasten the chamber portion  160  to the first circumferential portion  110  and the second circumferential portion  120  and keep the cannula in a closed state. Alternative structures may also be used such as a snap fit or ratcheting mechanism. 
     While various features have been described in conjunction with the examples outlined above, various alternatives, modifications, variations, and/or improvements of those features and/or examples may be possible. Accordingly, the examples, as set forth above, are intended to be illustrative. Various changes may be made without departing from the broad spirit and scope of the underlying inventive principles.