RELATED APPLICATION 
       [0001]    This application is a Divisional of U.S. patent application Ser. No. 13/545,185, filed Jul. 10, 2012. This disclosure of this prior application is herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Related technical fields include cannulas and clamping methods including cannulas and clamping methods for perfusing one or more organs or tissue to monitor, treat, sustain and/or restore the viability of the organ(s) or tissue and/or for transporting and/or storing the organ(s) or tissue. 
         [0003]    Various devices have been developed that couple the anatomy of an organ being perfused to a perfusion machine or other equipment such as that described in U.S. Pat. No. 7,824,848, the entire disclosure of which is hereby incorporated by reference. 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 this specification to refer to a clamp or other device that provides a connection through which fluid flow may be established. 
         [0004]    A type of cannula as described in U.S. Pat. No. 5,728,115 to Westcott et al. is shown in  FIGS. 1-3 . A clamping device (cannula)  10  is used to couple a perfusion device 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 . 
         [0005]    In use, the clamp  10  is attached to a blood vessel of a donor organ such as the renal aorta  34  of 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 . 
       SUMMARY 
       [0006]    In the cannula described above, the orientation of the clamp heads  24  and  26  with respect to each other is fixed because the clamp heads  24  and  26  are integral to the members  12  and  14 , respectively. Accordingly, the force applied to the tissue during the clamping process may be unevenly distributed across the surface of the tissue, thereby potentially resulting in damage to the tissue or an inadequate grip that is susceptible to failure. In addition, although the cannula shown in  FIGS. 1-3  is biased in the closed or clamping position by the spring  22 , the cannula does not include a locking mechanism to prevent the cannula from opening at an undesired time. Also, the cannula shown in  FIGS. 1-3  provides poor visibility of the vasculature because of a limited range of movement and because the clamp heads  24  and  26  are made of an opaque material (typically metal). The limited range of movement also limits access to the clamp heads  24  and  26 , increasing difficulty of use. Further, the nipple  28  may be susceptible to leaks due to a relatively smooth construction and the spring  22  does not allow for adjustment of the force applied to clamped tissue. 
         [0007]    In exemplary embodiments, a clamp such as a cannula includes a longitudinal base member and a longitudinal arm member pivotally attached to the longitudinal base member. The clamp also includes a first clamp member at a first end of the base member and a second clamp member pivotally attached to the arm member at a first end of the arm member, the first clamp member opposing the second clamp member. The second clamp member may be movable in more rotational axes and/or more rotational directions with respect to the arm member than the arm member is movable with respect to the base member. In addition, the second clamp member may have one or more than one degree of freedom of movement relative to the arm member, for example, two rotatable degrees of freedom with respect to the arm member. 
         [0008]    Pivotally attaching the second clamp member to the arm member allows for force applied to the tissue during the clamping process to be more evenly distributed, thereby reducing damage to the tissue. In addition, the grip on the tissue may be less likely to fail. Also, pivotally attaching the second clamp member to the arm member may allow the a first clamping surface to have a variable position relative to a second clamping surface when the arm member and the base member are held in place with respect to one another. 
         [0009]    In exemplary embodiments, a clamp such as a cannula includes a longitudinal base member having a first clamping end and a longitudinal arm member pivotally attached to the longitudinal base member and having a second clamping end. The clamp is in a closed position when the first and second clamping ends are brought together. The clamp also includes a first locking member positioned on the arm member and a second locking member positioned on the base member. The first and second locking members interact with each other to releasably lock the clamp in the closed position. 
         [0010]    In exemplary embodiments, a clamp such as a cannula includes a longitudinal base member having a first clamping end and a longitudinal arm member pivotally attached to the longitudinal base member and having a second clamping end, the clamp being in a closed position when the first and second clamping ends are brought together. The clamp also includes a first clamp member at a first end of the base member and a second clamp member movably (e.g., pivotally) attached to the arm member at a first end of the arm member, the first end of the arm member opposing the first end of the base member. In addition, the clamp includes a first locking member positioned on the arm member and a second locking member positioned on the base member. The first and second locking members interact with each other to releasably lock the clamp in the closed position. 
         [0011]    In exemplary embodiments, a method of clamping or cannulating a blood vessel includes clamping the blood vessel between a first clamp surface that applies a first force on the blood vessel and a second clamp surface that applies a second force on the blood vessel. A magnitude of the first force is substantially consistent over an entire surface of the blood vessel that is in contact with the first and second clamp surfaces. Clamping or cannulating the blood vessel may facilitate a connection between the blood vessel and a perfusion apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Exemplary implementations can be described with reference to the following figures wherein: 
           [0013]      FIGS. 1-3  illustrate a cannula of the prior art; 
           [0014]      FIG. 4  illustrates an exemplary clamping apparatus in a closed position; 
           [0015]      FIG. 5  illustrates an exemplary clamping apparatus of  FIG. 4  in an open position; 
           [0016]      FIG. 6  illustrates an exemplary base member of the clamping apparatus of  FIGS. 4 and 5 ; 
           [0017]      FIG. 7A  illustrates an exemplary floating clamp member of the clamping apparatus of  FIGS. 4 and 5 ; 
           [0018]      FIG. 7B  illustrates another view of the floating clamp member of  FIG. 7A ; 
           [0019]      FIG. 8  illustrates an exemplary floating clamp member seat of the clamping apparatus of  FIGS. 4 and 5 ; and 
           [0020]      FIG. 9  illustrates exemplary clamping surfaces of the clamping apparatus of  FIGS. 4 and 5 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0021]      FIG. 4  shows a perfusion clamping apparatus or cannula  100  according to exemplary embodiments. The cannula  100  is capable of connecting one or more blood vessels of an organ or tissue to a perfusion machine or system (not shown) such as that described in U.S. Pat. No. 7,824,848, the entire disclosure of which is hereby incorporated by reference, 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. For convenience, the term “organ” will be used herein to mean organ and/or tissue, except as otherwise specified. 
         [0022]    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 on the physiological environment and specific agents known to aid in tissue protection. Further, the medical fluid may be or include blood or blood products. 
         [0023]    The cannula  100  is shown in  FIG. 4  in a closed or clamping condition and in  FIG. 5  in an open condition. The cannula  100  may comprise a base  102 , an arm  104 , an optional locking mechanism  106  and a floating clamp member  108 . Although the floating clamp member  108  is illustrated as being attached to the arm  104 , it is contemplated that the floating clamp member  108  may be attached to the base  102  instead of the arm  104 . It is further contemplated that the base  102  and the arm  104  may both be attached to respective floating clamp members  108 . The base  102  and the arm  104  may be pivotably connected via a pivot mechanism  110 . As illustrated, the pivot mechanism  110  may be a pin about which one or both of the base  102  and the arm  104  can rotate. The pivot mechanism  110  may be positioned at any location between a distal end  112  and a clamping end  114  of the cannula  100 . As can be seen in  FIG. 4 , when the cannula  100  is in the closed condition, the base  102  and the arm  104  are brought together at the distal end  112  and at the clamping end  114 . As can be seen in  FIG. 5 , when the cannula  100  is in the open condition, the base  102  and the arm  104  are moved apart from each other at the distal end  112  and at the clamping end  114 . When being rotated from the closed condition to the open condition, the arm  104  and/or base  102  may be rotated as much as or more than 180 degrees. 
         [0024]    The base  102  and the arm  104  may be pivotable around an axis  116  of the pivot mechanism  110  that extends in a first direction and may be adjacent to each other at the pivot mechanism  110  in the first direction. The first direction may be perpendicular to a longitudinal axis of the cannula  100 . The base  102  and the arm  104  may also be adjacent to each other in the first direction at the distal end  112  but may be adjacent to each other in a second direction at the clamping end  114 . The second direction may be different from the first direction. The second direction is preferably, but not necessarily, substantially perpendicular to the first direction. For example,  FIG. 4  illustrates the base  102  and the arm  104  as being adjacent to each other at the pivot mechanism  110  in a side-by-side configuration (i.e., adjacent in the first direction).  FIG. 4  also illustrates the base  102  and the arm  104  as being overlapped at the clamping end  114  in a stacked configuration (i.e., overlapped in the second direction). The base  102  and the arm  104  are preferably pivotable with respect to each other around only the axis  116 . 
         [0025]    As illustrated in  FIGS. 4 and 5 , there is preferably no biasing member (such as the spring  22  shown in  FIG. 1 ) that biases the cannula  100  towards either a closed or open position. Such a lack of a biasing member may be advantageous in that the cannula  100  can be opened or closed, or adjusted to any position in between, and remain in that position without further action by a user. If such a biasing member were included, further structure, such as a brake or locking mechanism, could be included to achieve the advantage of the cannula  100  remaining in a position set by the user (other than the position dictated by the biasing member). A lack of biasing member may also allow the cannula  100  to open wider than if a biasing member is provided. For example, the spring  22  shown in  FIG. 1  requires that the cannula  10  be squeezed to open, and there is limited travel between the handles  18  and  20 , which results in a limited opening space between clamp heads  24  and  26 . However, the cannula  100  shown in  FIGS. 4-5  is not so limited. The cannula  100  has a squeeze-to-close action opposite of the squeeze-to-open action of the cannula  10 . By including a squeeze-to-close action and no biasing member, the cannula  100  can be opened over a much wider range than is possible with the cannula  10  of  FIG. 1 . Also, such a squeeze-to-close configuration without a biasing member may allow for intermediate positions or stop points between a fully open position and a fully closed position. Any desired stop points may be provided with structure than tends to keep the cannula  100  in an intermediate position. Such structure could be achieved, for example, using detents (not shown). However, one of ordinary skill would appreciate that the cannula  100  could include a biasing member biasing the cannula  100  either open or closed if the needs of a user so dictate. 
         [0026]    The base member  102  may include a first gripping portion  118  and a clamping portion  120 . The first gripping portion  118  may extend from the distal end  112  of the cannula  100  to near the clamping members, e.g., the optional locking mechanism  106 , and may be ergonomically configured to receive at least a first portion of a right and/or left hand of a user. The clamping portion  120  may be integrally formed with the base member  102  or may be a separately formed component. In addition, the clamping portion  120  may include an opening  122  through which an aortic patch or other type of vasculature of an organ may be fed. The clamping portion  120  may also include a first clamping surface  124  that is configured to cooperate with the floating clamp member  108  to clamp the aortic patch or other type of vasculature of the organ. 
         [0027]    The arm member  104  may include a second gripping portion  126  and a floating clamp member seat  128 . The second gripping portion  126  may extend from the distal end  112  of the cannula  100  to near the clamping members, e.g., the optional locking mechanism  106 , and may be ergonomically configured to receive at least a second portion of the right and/or left hand of the user. The floating clamp member seat  128  may be configured to receive and support the floating clamp member  108 . 
         [0028]    The cannula  100  may preferably be configured to be operated (i.e., moved from the open condition to the closed condition or moved from the closed condition to the open condition) by one hand of the user. In addition, the cannula  100  may be ergonomically configured to be used by either a left hand or a right hand of the user. For example, in a left-handed configuration (as shown throughout the figures), the base  102  may be positioned to the right of the arm  104  at the pivot mechanism  110  when the cannula  100  is oriented so that the clamping end  114  is furthest from the user. Conversely, in a right-handed configuration (a mirror-image of what is shown throughout the figures), the base  102  may be positioned to the left of the arm  104  at the pivot mechanism  110  when the cannula  100  is oriented so that the clamping end  114  is furthest from the user. 
         [0029]    The optional locking member  106  may lock the cannula  100  in the closed condition. Preferred embodiments may include a primary lock member  130 , a toothed member  132  and an optional secondary lock member  134 . The primary lock member  130  may be pivotally connected to the base  102  and may include an interacting portion  136 , an unlocking portion  138  and a biasing portion  140 . The interacting portion  136  may extend from the base  102  toward the toothed member  132  attached to the arm  104  and may pivot between a locked position and an unlocked position. The interacting portion  136  may include a hook-like portion  142  that may be positioned between the teeth of the toothed member  132 . When the hook-like portion  142  is hooked to a tooth of the toothed member  132 , the locking member  106  prevents the arm  104  from rotating open with respect to the base  102 . It is contemplated that the toothed member  132  may be flexibly or pivotally attached to the arm  104 . In either case, the toothed member  132  may be optionally biased. It is further contemplated that the primary lock member  130  may be pivotally connected to the arm  104  and the toothed member  132  may be flexibly or pivotally attached to the base  102 . 
         [0030]    The unlocking portion  138  may be connected to the interacting portion  136  at a pivot  144  so that when the unlocking portion  138  is pivoted around the pivot  144 , the interacting portion is also pivoted around the pivot. The unlocking portion  138  is preferably positioned so that the base  102  is between the unlocking portion  138  and the interacting portion  136 . Accordingly, pressing the unlocking portion  138  toward the base member  102  may cause the interacting portion  136  to move into the unlocked position. Conversely, allowing the unlocking portion  138  to pivot away from the base member  102  may cause the interacting portion  136  to move into the locked position. 
         [0031]    The biasing member  140  is optional, and may be a spring-like element that extends from the interacting portion  136  toward the base  102 . The biasing member may apply a biasing force that biases the interacting portion  136  toward the locked position. 
         [0032]    The optional secondary lock member  134  may include a first sliding member  146  (as illustrated in  FIG. 4 ) and a second sliding member  148  (as illustrated in  FIG. 6 ). The first sliding member  146  may be positioned on the same side of the base  102  as the interacting portion  136 . Positioning the first sliding member  146  in this manner may allow the optional secondary lock member  134  to be actuated by the user&#39;s thumb. The first sliding member  146  may be slidable toward and away from the interacting portion  136 . The second sliding member  148  may be positioned on the same side of the base  102  as the unlocking portion  138  and may be slidable toward and away from the unlocking portion  138 . The first and second sliding members  146  and  148  are connected to each other so that when the first sliding member  146  is moved in a particular direction, the second sliding member  148  is moved in the same direction. In addition, the second sliding member  148  is positioned so that when the second sliding member  148  is moved toward the unlocking portion  138 , the second sliding member  148  is moved between the base  102  and the unlocking portion  138 . This has the effect of preventing the unlocking portion  138  from being pressed toward the base  102 . Accordingly, while the second sliding member  148  is between the unlocking portion  138  and the base  102 , the interacting portion  136  cannot be moved to the unlocked position, and the cannula  100  cannot be moved from the closed condition to the open condition. This is advantageous because the cannula  100  is less likely to open unintentionally, which could result in the loss of or damage to an organ that has been cannulated. 
         [0033]    The first sliding member  146  may be omitted from the secondary lock member  134 . In an embodiment without the first sliding member  146 , the user may operate the optional secondary lock member  134  by sliding the second sliding member  148 , which may be accomplished with one of the user&#39;s fingers. 
         [0034]    As illustrated in  FIGS. 7A and 7B  the floating clamp member  108  may include a coupling portion  150 , a support portion  152  and a cup portion  154 . The coupling portion  150  may form a tubular structure and may provide a connection (such as a hose barb or luer lock) to a tube or other fluid conduit that connects the cannula  100  to the perfusion machine or system (not shown). Use of a hose barb or luer lock is advantageous because such structures are less likely to leak than the nipple  28  shown in  FIGS. 1-3 . 
         [0035]    In embodiments, the cannula  100  may include features that allow for the second clamping surface  178  to change an angle relative to the first clamping surface  124  other than through movement of the base  102  and the arm  104 . The change in relative angle can be about one or more axes. Such a change in angle can allow for the cannula  100  to clamp or cannulate varying thickness of tissue in a single blood vessel or the like that would otherwise prove troublesome with a cannula that does not allow for similar relative changes in angle between clamping surfaces. For example, with a cannula that does not allow for relative change in angle between clamping surfaces, it may be necessary to overly compress, and possibly damage, a blood vessel that is being cannulated or clamped in order to produce an adequate seal. Alternatively, a seal that leaks may be required in order to avoid damage to the blood vessel. 
         [0036]    In the depicted embodiment, the support portion  152  may include a plurality of features to connect the floating clamp member  108  to the arm  104 . For example, the support portion may include a main body  156 , upper primary support members  158 , lower primary support members  160  and secondary support members  162 . The upper primary support members  158  may be projections from the main body  156  and may each have a substantially horizontal bottom surface  164 . The lower primary support members  160  may be positioned closer to the cup portion  154  than the upper primary support members  156  and may also be projections from the main body  156 . The lower primary support members  160  may each have substantially horizontal top surfaces  166 . The secondary support members  162  may be positioned closer to the cup portion  154  than the lower primary support members  160  and may also be projections from the main body  156 . Alternatively, the lower primary support members  160  may be positioned closer to the cup portion  154  than the secondary support members  162 . Either of these offset configurations may be advantageous in that when interacting with corresponding mating structure on the floating clamp member seat  128 , two rotational degrees of freedom can be achieved while preventing a third rotational degree of freedom. The secondary support members  162  may each have horizontal top surfaces  168 . The upper primary support members  158  may preferably be on opposite sides of the main body  156  from each other, the lower primary support members  160  may preferably be on opposite sides of the main body  156  from each other and/or the secondary support members  162  may preferably be on opposite sides of the main body  156  from each other. The upper primary support members  158  and the lower primary support members  160  may have similar or different shapes and sizes. 
         [0037]    As can be seen in  FIG. 8 , the floating clamp member seat  128  may include an opening  170  through which the floating clamp member  108  may be inserted and a support portion  172  surrounding the opening  170  that may support the floating clamp member  108 . The support portion  172  may include a plurality of first recesses  174  and a plurality of second recesses  176 . The first recesses  174  may each be configured to receive a corresponding upper primary support member  158 . In addition, each first recess  174  may be shaped complementarily to the corresponding upper primary support member  158 . For example, each of the first recesses  174  may be closed at the bottom and may be open at the top. The first recesses  174  may be sized to have a larger volume than the respective corresponding upper primary support members  158  so that the upper primary support members  158  may be free to move within the respective corresponding first recesses  174 . 
         [0038]    The second recesses  176  may each be configured to receive a corresponding lower primary support member  160 . In addition, each second recess  176  may be shaped complementarily to the corresponding lower primary support member  160 . For example, each of the second recesses  176  may be open at the bottom and may be closed at the top. The second recesses  176  may be sized to have a larger volume than the respective corresponding lower primary support members  160  so that the lower primary support members  160  may be free to move within the respective corresponding second recesses  176 . 
         [0039]    The configuration of the support portion  172  within the floating clamp member seat  128  may permit the floating clamp member  108  to rotate around more than one axis. For example, the floating clamp member  108  may rotate around an axis  180  that extends through centers of the upper primary support members  158 . The axis  180  may extend along a plane that is parallel to a longitudinal axial plane of the cannula  100 . The floating clamp member  108  may also rotate around an axis  182  that extends through centers of the lower primary support members  160 . The axis  182  may also extend along a plane that is parallel to the longitudinal axial plane of the clamping apparatus. Other structures that allow at least two degrees of rotation between the floating clamp member  108  and the arm  104  are contemplated by the inventive principles discussed herein. 
         [0040]    By permitting the floating clamp member  108  to rotate around two or more different axes, the orientation of a second clamping surface  178  may be variable with respect to the orientation of the first clamping surface  124 . Accordingly, the cannula  100  may be more sensitive to variations in thickness of the tissue being clamped, thereby reducing the amount of damage to the tissue that may occur during the clamping process and reducing the likelihood that the grip will fail. Such rotation about two or more different axes also allows the first clamping surface  124  and the second clamping surface  178  to approach and/or engage one another, or engage clamped tissue, in a parallel fashion. In this mariner, the entirety of each clamping surfaces will engage as near to simultaneously as practicable, which may result in more even application of clamping force and less likelihood of damage (or uneven damage) to clamped tissue. Evenly distributed clamping force may also be achieved, which may result in a superior seal versus clamping surfaces that cannot achieve such relative movement. Preferably, the floating clamp member  108  has a range of motion about each axis of about 15 degrees (7.5 degrees of positive and negative rotation for each axis) and more preferably about 12 degrees (6 degrees of positive and negative rotation for each axis) to avoid superfluous movement. 
         [0041]    The cup portion  154  of the floating clamp member  108  may include the second clamping surface  178 , which interacts with the first clamping surface  124  of the base  102  to clamp the tissue. As can be seen in  FIG. 9 , one clamping surface (e.g., the second clamping surface  178 ) may have a larger diameter than the other clamping surface (e.g., the first clamping surface  124 ). Although  FIG. 9  illustrates the second clamping surface  178  having a larger diameter than the first clamping surface  124 , it is contemplated that the first clamping surface  124  can have the larger diameter. In addition, one clamping surface may have a stepped shape along a perimeter, while the other clamping surface may have a shape complementary to the stepped shape of the one clamping surface in order to form a tighter seal around the clamped tissue. Alternatively, the first clamping surface  124  and the second clamping surface  178  may have similar cross-sectional shapes. It should be understood that, while in the closed position, the clamping surfaces can be in contact with each other or spaced apart a suitable distance (e.g., 0.5 mm to 4.00 mm, more preferably 1.0 mm to 3.0 mm) to accommodate tissue. 
         [0042]    The cannula  100  can be made from any suitable material or materials, such as metal or transparent or opaque plastics, but plastics provide several advantages. Plastics are usually less costly, and can therefore be made disposable. A disposable version of the cannula  100  will not have the additional costs associated with reuse, such as re-sterilization. 
         [0043]    Portions of the cannula  100  can be made from optically transparent material. This may be beneficial in that it can aid a clinician in positioning the vasculature and in detecting air bubbles or the interior or intima of the vasculature. 
         [0044]    Either or both of the first clamping surface  124  and the second clamping surface  178  can include serrations and/or knurls to facilitate securing the clamped tissue. If the serrations or knurls are made from plastics, the plastics can be chosen with specific material properties to limit or prevent damage to clamped tissue. Additionally, serrations or knurls can be specifically tailored to the tissue to be clamped. The first clamping surface  124  and/or the second clamping surface  178  may include an elastomeric material to work in conjunction with and/or be substituted for the serrations and/or knurls. 
         [0045]    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.
A cannula has a longitudinal base member having a first clamping end and a longitudinal arm member pivotally attached to the longitudinal base member and having a second clamping end, the cannula being in a closed position when the first and second clamping ends are brought together. A first clamp member is located at the first clamping end and has a first passage. A second clamp member is rotatably attached to the aim member at the second clamping end and has a second passage. The first and second passages form a combined passage when the clamp is in the closed position. The cannula may have a first locking member positioned on the arm member and a second locking member positioned on the base member. The first and second locking members interact with each other to lock the cannula in the closed position.