Patent Publication Number: US-2001000528-A1

Title: Cavo-atrial cannula and method of use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     1. This application is a Continuation in Part application related to U.S. patent application Ser. No. 09/274,588 which has issued as U.S. Pat. No. ______ on ______.  
    
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       2. None  
       REFERENCE TO MICROFICHE APPENDIX  
       3. N/A  
       BACKGROUND OF THE INVENTION  
       4. 1. Field of the Invention  
       5. This invention relates to the field of heart surgery. More specifically, this invention relates to a method of performing heart surgery using a cavo-atrial cannula to remove blood from the body.  
       6. 2. Description of the Related Art  
       7. When the heart must be stopped for a surgical procedure, the function of the heart and lungs is assumed temporarily by a mechanical device, a pump oxygenator, which drains the patient&#39;s blood, oxygenates it, and returns it to the patient through tubing connected to cannulae placed in the patient&#39;s heart and aorta. This surgical technique is known as cardiopulmonary bypass surgery. Typically, drainage is accomplished by a single venous cannula, possessing two sets of openings, placed through an incision in the right atrium and secured in place by a pursestring-suture tourniquet applied along the edges of the atrial incision such that the cannula tip lies in the inferior vena cava. The set of openings at the cannula&#39;s terminus drain blood from the inferior vena cava, and the openings proximal to it drain the blood which has arrived from the superior vena cava and other lesser sources into the right atrium. An alternative method uses two venous cannulae, one directed into the superior vena cava and the other into the inferior vena cava. One or both of these cannulae are introduced through incision(s) in the right atrium.  
       8. The currently used venous cannulae and the methods by which they are placed in the heart present certain problems. The right atrium suffers significant damage not only from the incisions made to introduce the cannula(e) but also because of the right atrium&#39;s relative inaccessibility to the protective measures used to preserve heart tissue functional integrity during surgery. These protective measures consist primarily of drugs, such as cardioplegic solutions, infused into the blood supply of the heart tissue to arrest beating, as well as the constant application of ice-cold saline or ice to the surface of the arrested heart to slow down the heart&#39;s metabolism. The method by which the cannula(e) is/are currently placed in the right atrium prevents the protective drugs from reaching the atrial tissue constrained in the tourniquet. Furthermore, the atrial tissue at the entry site of the cannula(e) escapes the cold saline bath inasmuch as the atrial tissue is suspended upward out of the chest by the outward course of the cannula(e) toward the pump oxygenator. The functional consequences of direct injury to the atrial tissue as well as the sub-optimal access to the protection afforded to the rest of the heart include decreased strength of contraction and, perhaps more importantly, disordered atrial rhythm, e.g., atrial fibrillation, which can cause poor cardiac function, blood clots, and dangerously high heart rates. The drugs used to treat atrial fibrillation also have an array of potentially dangerous side-effects. The economic costs of atrial dysfunction reflect the price of the drugs used to treat it, longer hospital stays, and the additional hospital admissions for related complications.  
       9. These problems can be avoided by making no incision in the atrium, and instead, placing the venous drainage cannula through an incision in the superior vena cava or inferior vena cava.  
       10. Currently available cannulae can not be inserted into the vena cava as a single drainage conduit for blood from the venae cava and right atrium for three reasons. First, most currently available caval cannulae are designed to be used in pairs and if used singly have too narrow a diameter for adequate venous drainage and to maintain adequate flow of blood from the patient. Second, even if the diameter of the currently available cannulae were enlarged enough to maintain adequate flow of blood from the patient, the placement of such enlarged diameter cannulae in the superior vena cava would cause significant obstruction to blood flow from the head and upper body which normally courses through the superior vena cava into the right atrium. Similarly, enlarged diameter cannulae can not be inserted into the inferior vena cava because the placement of such cannulae in the inferior vena cava would cause significant obstruction to blood flow from the lower body which normally courses through the inferior vena cava into the right atrium. Third, currently available cannulae contain circumferential openings. If a large cannula with circumferential openings lies obliquely just within the vena cava, then it would increase the risk of entraining air into the pump circuit, causing an “air lock” and obstruction to flow.  
       11. The placement of the openings in the currently available cannulae is not appropriate for effective drainage of the blood flowing down the superior vena cava when the cannulae are inserted through the superior vena cava nor for effective drainage of the blood flowing up the inferior vena cava when the cannulae are inserted through the inferior vena cava. Use of currently available cannulae for drainage of blood through the superior vena cava would cause obstruction of the blood flow and could cause swelling of the brain, neurological dysfunction, and stroke. Obstruction of inferior vena cava blood flow could cause congestion and dysfunction of the abdominal organs.  
       BRIEF SUMMARY OF THE INVENTION  
       12. This invention overcomes all of the problems associated with the prior art. The heart may be effectively drained of blood during cardiopulmonary bypass using a single cannula without injuring the right atrium, thereby according the right atrium all the benefits of cardioprotective measures. The device and the methods of its use accomplish these effects by placing a cannula into the right atrial cavity through an incision in the adjacent vena cava. No incision is made in the atrium. There is no pursestring-suture tourniquet in the atrial tissue. Cardioprotective agents are infused into all of the atrial tissue. The atrium lies well within the chest, accessible to the cold saline bath.  
       13. The present invention contains a bend in the cannula because a cannula entering a vena cava from the usual opening in the patient&#39;s chest must make a roughly right-angle bend to proceed on to the right atrium or into the opposite vena cava.  
       14. The present invention also contains openings at a bend in the cannula. These openings face the direction of approach of the blood from the head and upper body if the invention is inserted into the superior vena cava or from the lower body if the invention is inserted into the inferior vena cava. Thus, the openings must be on the outer aspect of the bend in the cannula. Furthermore, the openings at the cannula&#39;s bend are not circumferential.  
       15. Therefore, in addition to openings at the closed terminus of the cannula to drain the right atrium, the device incorporates separate openings in the cannula, specifically positioned on the outer aspect of the bend in the cannula such that it would receive the blood from the head and upper body when inserted through the superior vena cava into the right atrium and from the torso and lower body when inserted through the inferior vena cava into the right atrium.  
       16. Furthermore, in order to prevent the massive loss of blood during insertion of the cannula into the vena cava in the form of blood entering the openings at the closed terminus and exiting through the openings at the bend before it is seated in the vena cava, the device incorporates a removable obturator to block the second openings from within the cannula until the cannula is properly seated, at which time the obturator is withdrawn from the lumen of the cannula.  
       17. In an alternative embodiment the removable obturator is placed on the outside of the cannula over the openings at the bend. These obturators can include a sliding cover over the openings that is either moved or removed or a tape-like cover that is removed prior to securing the cannula into position.  
       18. To maximize drainage of blood from the right atrium, the diameter of the distal portion of the cannula should not be substantially less than that of the cannula resting in the vena cava. Therefore, the invention provides for little or no narrowing of the cannula beyond the vena cava openings except a short curved taper at the tip to facilitate initial insertion into the vena cava.  
       19. The invention also pertains to an improvement in the method of performing cardiopulmonary bypass surgery, the improvement being the use of a cavo-atrial cannula inserted into the superior vena cava or inferior vena cava and having its closed terminus within the right atrium to remove blood from the patient. The cavo-atrial cannula is connected to tubing through which the blood travels to a pump oxygenator. From the pump oxygenator, the blood travels through tubing to an arterial cannula positioned in the aorta or another artery.  
       20. The invention also pertains to an improvement in the method of performing cardiopulmonary bypass surgery, the improvement being the insertion of a cavo-atrial cannula into either venae cava and positioning the closed terminus of the cannula in the right atrium. The cavo-atrial cannula has a curved tip at the closed terminus, openings near the closed terminus, a bend, and openings at a bend on the outside of the bend. In this improvement, if the cavo-atrial cannula is inserted into the inferior vena cava, blood from the lower body enters the lumen of the cannula via the openings at the bend seated in the inferior vena cava while blood from the head, upper body, and right atrium enters the lumen of the cannula via the openings near the closed terminus, seated in the right atrium. Alternatively, if the cavo-atrial cannula is inserted into the superior vena cava, the blood from the head and upper body enters the lumen of the cannula via the openings at the bend which is seated in the superior vena cava while blood from the lower body and right atrium enters the lumen of the cannula via the openings near the closed terminus which is seated in the right atrium. In this method, one removes the removal obturator from the openings at the bend after insertion of the device into the venae cava to prevent blood from flowing out of the device through the openings at the bend. The cavo-atrial cannula is connected to tubing through which blood travels to a pump oxygenator and any other device before returning to the patient&#39;s body via arterial cannula placed in aorta or other artery.  
       21. Another improvement for the method of cardiopulmonary bypass surgery relates to using the cavo-atrial cannula having three sets of openings. This cavo-atrial cannula is inserted into a vena cava, the closed terminus is seated in the opposite vena cava. The cavo-atrial cannula is secured into position and the obturator is removed. Alternatively the obturator is removed or moved prior to completely securing the cavo-atrial cannula into place. Blood from the lower body enters the cannula via one set of openings. Blood from the head and upper body enters the cannula via another set of openings. Blood from the right atrium enters the cannula from a third set of openings. The cannula is connected to tubing which takes the blood to a pump oxygenator after which the blood is returned to the body via a cannula previously placed in the aorta or another artery.  
       22. This invention also relates to a method of removal of blood from a patient so that one can perform surgery with an opened right atrium. For this method of removal of blood from a patient during surgery the cavo-atrial cannula is inserted in the superior vena cava and then extended into the inferior vena cava or inserted into the inferior vena cava and then extended into the superior vena cava. The obturator is removed or moved prior to completely securing the cannula into proper position, or completely removed after securing the cannula into proper position. Again tubing is connected to the cannula to take blood to a pump oxygenator after which the blood is returned to the body via a cannula inserted into the aorta or other artery. Tourniquets around the outside of the vena cavae are used to prevent blood from entering into the right atrium, thereby permitting one to perform surgery with the right atrium open.  
       23. A further improvement to these methods is one using the safe mark, the reference mark and the rotation mark to assist in the proper positioning of the cannula in the patient&#39;s vena cava.  
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
     24.FIG. 1 shows a side view of the invention according to the preferred embodiment.  
     25.FIG. 2A shows a back view of the invention according to the preferred embodiment.  
     26.FIG. 2B shows a front view of the invention according to the preferred embodiment.  
     27.FIG. 3 shows a cut-away view of the invention according to the preferred embodiment.  
     28.FIG. 4 shows a side view of an alternative embodiment of the invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     29.FIG. 1 illustrates the preferred embodiment of a cavo-atrial cannula,  10 . A cavo-atrial cannula is a hollow tube containing an upper portion,  11 , a middle portion,  12 , and a closed terminus,  14 . The closed terminus contains a curved tip,  13 . At the end opposite the curved tip is the cavo-atrial cannula&#39;s open terminus,  15 . The cavo-atrial cannula possesses, at a minimum, two sets of openings, a first openings,  16 , and a second openings,  17 . The first openings may be circumferential, but the second openings can not be circumferential. In the preferred embodiment, the cavo-atrial cannula also contains a bend,  18 , located at the junction between the upper portion and middle portion.  
     30. As illustrated in FIG. 3, when used in adult patients, it is preferable for the interior diameter,  51 , of the middle portion,  12 , and upper portion,  11 , to be constant until the beginning of the closed terminus,  14 . However, it is possible for the upper portion,  11 , to have a wider diameter above the safe mark,  30 , than the diameter in the middle portion,  12 . The interior diameter,  51 , can range approximately between one to two centimeters which is sufficient caliber to permit blood to flow freely within the lumen of the cavo-atrial cannula, and to avoid sheer stress on the blood cells. The thickness of the walls,  52 , of the cavo-atrial cannula does not add substantially to the overall diameter of the device. The overall diameter of the cavo-atrial cannula enables the invention to fit inside the patient&#39;s superior vena cava and/or inferior vena cava. For pediatric patients, the interior diameter,  51 , and overall diameter will be smaller than when used for adult patients.  
     31. Referring to FIGS. 1, 2B, and  3 , the curved tip,  13 , has a gradual taper. Thus, the cavo-atrial cannula&#39;s overall diameter increases from the curved tip&#39;s terminus to the beginning of the middle portion,  12 . The curved tip is curved in the plane and same direction as the bend,  18 . The end of the curved tip terminates prior to it reaching beyond the overall diameter of the cavo-atrial cannula in order to minimize the tendency to snag tissue as the cavo-atrial cannula is advanced or withdrawn. The curved tip makes it easier for the user to insert the device into the patient&#39;s vena cava. The tapered, curved tip also helps the surgeon to negotiate the right angle of the vena cava with respect to the approach as he first inserts the cannula into the vena cava.  
     32. The first openings,  16 , can be located anywhere between the closed terminus,  14 , and a point in the middle portion located approximately three centimeters from the junction of the middle portion,  12 , and the closed terminus. While the exact location can vary, the first openings should be located at a point where the interior diameter,  51 , of the cavo-atrial cannula is large enough to permit blood to flow freely within the lumen of the cavo-atrial cannula, and to avoid sheer stress on the blood cells. When the cavo-atrial cannula is properly inserted, the first openings should be located inside the patient&#39;s right atrium. The first openings will be of sufficient size to permit the unobstructed flow of blood into the cannula and to minimize the disruption of red blood cells.  
     33. In FIG. 1, the bend,  18 , is located at the junction of the middle portion,  12 , and upper portion,  11 . The angle of inclination,  40 , of the bend can range from approximately twenty-five degrees (25°) to one-hundred eighty degrees (180°), depending on the physical properties of material used to make the cavo-atrial cannula. If the material is flexible and can bend without creating a closure of the lumen of the device, then the angle of inclination can be larger than one-hundred thirty-five degrees (135°). In the preferred embodiment, the angle of inclination ranges between forty-five degrees (45°) and one-hundred thirty-five degrees (135°).  
     34. In FIGS. 1 and 2A, the second openings,  17 , of the cavo-atrial cannula is located at the junction of the upper portion,  11 , and the middle portion,  12 , on the outer side of the bend,  18 . When the cavo-atrial cannula is properly inserted into the vena cava, the second openings is located so that blood from the vena cava can flow into the cavo-atrial cannula. If the second openings was absent the cavo-atrial cannula would obstruct the flow of blood from the head to the heart when the invention is inserted into the superior vena cava or from the lower body to the heart when the invention is inserted into the inferior vena cava. The distance from the curved tip,  13 , to the second openings,  17 , can range from approximately five centimeters to approximately fifteen centimeters.  
     35. The first openings,  16 , and the second openings,  17 , can be a plurality of holes or slits adjacent to each other in the walls of the cavo-atrial cannula. They may run laterally or longitudinally. It is recommended that the walls of the cavo-atrial cannula proximal to and surrounding the openings be of a stiffer, stronger material than the rest of the walls of the cavo-atrial cannula for increased support. The increased support is recommended but not vital.  
     36. The distance between the first openings and the second openings can range from approximately five to thirteen centimeters. The length of the upper portion can be approximately twenty centimeters or longer.  
     37. The cavo-atrial cannula,  10 , can be made of any material that is approved by the Food and Drug Administration for these types of devices. The material should be flexible yet not able to bend or kink so that the flow of blood will not be obstructed. Use of a polyvinylchloride reinforced with an intramural spiral wire is commendable.  
     38. In the preferred embodiment, as shown in FIGS. 1 and 3, the cavo-atrial cannula has a removable obturator,  25 , located inside the lumen of the invention, extending from the second openings,  17 , through the open terminus,  15 . The obturator occludes the second openings while the cavo-atrial cannula is being inserted into the patient. The obturator prevents blood which enters the lumen of the cavo-atrial cannula via the first openings,  16 , from leaving the lumen of the invention through the second openings,  17 , prior to the proper seating of the cavo-atrial cannula within the vena cava. Without the obturator, blood may exit the cavo-atrial cannula inappropriately, causing excessive bleeding, blood loss, and possibly death. The obturator,  25 , may be made from plastic or any other appropriate material. The obturator has an occluding portion,  26 , and non-occluding portion,  27 . The occluding portion covers the second openings,  17 , and extends above the second openings for some distance. The diameter of the occluding portion is identical to or slightly smaller than the interior diameter,  51 , of the cavo-atrial cannula so that the occluding section fits snugly inside the lumen of the invention and prevents blood from entering or exiting the cannula through the second openings,  17 . The diameter of the non-occluding portion,  27 , of the obturator can be less than the interior diameter,  51 , of the cavo-atrial cannula so as to reduce friction during withdrawal and insertion of the obturator,  25 . When properly seated, the obturator terminates at or just beyond the bend,  18 , and blocks completely the second openings,  17 . The obturator may be solid or hollow. After the cavo-atrial cannula is properly inserted into the vena cava and is secured into place with a Rummel tourniquet and pursestring suture, one slides the obturator,  25 , out through the open terminus,  15 , thereby uncovering the second openings,  17 .  
     39. In alternative embodiments, the removable obturator can rest on the outside of the cannula and cover the second openings. In one of these embodiments, the obturator can be a strong, flexible material, such as a bendable plastic or metal, that is detachably secured by an adhesive to the outside of the device. It completely covering the second openings. Alternatively, each hole or slit of the second openings can be covered by an individual obturator. The second openings are covered by the occluding portion,  26 , of the obturator. The non-occluding portion,  27 , of the obturator extends from the bottom edge of the occluding portion, closest to the middle portion,  12 . The non-occluding portion folds one-hundred eighty degrees upon itself, traveling upward along the outside of the occluding portion and the upper portion,  11 , of the cannula. After the cavo-atrial cannula is seated in a vena cava, but before detachably securing it into place by tightening a Rummel tourniquet and pursestring suture, one pulls the non-occluding portion upward, peeling the occluding portion away from the second openings. The adhesive must be strong enough to prevent the obturator from falling off during handling but permits one to remove the obturator by pulling on the non-occluding portion with a small amount of force. Too strong of an adhesive may require too much force which may cause the device to move around and injure the patient.  
     40. In a second alternative embodiment, the obturator is made of stiff material. The occluding portion is shaped to conform to the curvature of the outside of the cannula. The obturator presses against the outside of the cannula and remains attached via pressure of the occluding portion pressing against the cannula over the second openings. A non-occluding portion extends upward from the top of the occluding portion along the upper portion of the cannula. After insertion of the device into a vena cava, one pulls on the non-occluding portion to slide the occluding portion upward along the outside of the cannula, thereby uncovering the second openings. One can either remove the obturator completely or let it stay attached to the cannula, so long as the obturator is completely above the safe mark. Then one secures the cavo-atrial cannula into place by tightening a Rummel tourniquet and pursestring suture.  
     41. In any embodiment, after the occluding portion of the obturator is moved away from the second openings, blood from the vena cava enters the lumen of the cavo-atrial cannula through the second openings. When the cavo-atrial cannula is used properly, the open terminus,  15 , remains outside the vena cava. After removal of the obturator,  25 , or uncovering of the second openings, depending on the embodiment used, one connects the open terminus,  15 , of the cavo-atrial cannula to tubing that carries the blood to a pump oxygenator or other equipment.  
     42. As shown in FIGS. 1, 2A and  2 B, the cavo-atrial cannula has a plurality of markings on the upper portion,  11 . These markings are visible markings. They can be colored lines or indentations or bumps or a combination of all three on the exterior of the cavo-atrial cannula. The markings need not be visible during radiographic imaging of the device. The safe mark,  30 , indicates the lowest level at which one can safely tighten and secure a pursestring suture. The safe mark is located approximately five millimeters above the top of the second openings,  17 , and designates the point beyond which the cavo-atrial cannula should not be withdrawn from the patient&#39;s vein because of the danger of air entrainment. Air entrainment can occur if, after the cavo-atrial cannula is connected to a pump oxygenator, air enters the lumen of the cavo-atrial cannula through the second openings and causes an air-lock. The safe mark ensures the proper depth of insertion of the cavo-atrial cannula. The reference mark,  31 , is located approximately five millimeters above the safe mark. The reference mark serves as a reference to warn that the last extent of safe withdrawal of the cavo-atrial cannula during seating is nearby. The safe mark and reference mark extend around the upper portion,  11 , perpendicular to the direction of flow of blood through the cavo-atrial cannula.  
     43. In FIGS. 1 and 2B, the rotation mark,  32 , runs on the exterior of the cavo-atrial cannula, on the side containing the angle of inclination,  40 , and opposite the location of the second openings,  17 . It begins on the middle portion,  12 , and terminates on the upper portion,  11 , above the safe mark,  30 . The rotation mark,  32 , assists in identifying the axial rotation of the second openings,  17 , particularly in those embodiments of the invention with a angle of inclination greater than 90°.  
     44.FIG. 3 illustrates the relative placement of the cavo-atrial cannula when inserted into a vena cava,  55 , and advanced into the right atrium,  56 . The pursestring suture and Rummel tourniquet are placed at the safe mark,  30 , or higher than the safe mark (see FIG. 1).  
     45. As illustrated in FIG. 4, in another alternative embodiment, the cavo-atrial cannula has three sets of openings. This alternative embodiment differs from the preferred embodiment by having an extended middle portion,  12   a , and another set of openings, the third openings,  35 . The third openings,  35 , is located in or just prior to the beginning of the curved tip,  13 . The extended middle portion allows the curved tip,  13 , and third openings,  35 , to lie in the vena cava opposite the site of insertion. The third openings,  35 , when the cavo-atrial cannula is properly inserted into the superior vena cava, is located in the inferior vena cava, and thus can drain blood from the inferior vena cava. The extended middle portion,  12   a , is extended approximately eight centimeters in length. In this alternative embodiment, the first openings,  16 , and the second openings,  17 , are located in the same positions with respect to each other on the cavo-atrial cannula as in the embodiment containing two sets of openings.  
     46. The improved methods of cardiopulmonary bypass surgery using the cavo-atrial cannula differs from current surgical techniques. In current surgical techniques, one either maks an incision in the right atrium and inserts a cannula through the right atrium into the inferior vena cava, or make two incisions for separate cannulation of each vena cava. In the improved method of cardiopulmonary bypass surgery of this invention, one makes an incision in the superior vena cava and inserts the cavo-atrial cannula into the superior vena cava. One then advances the cavo-atrial cannula through the superior vena cava to the right atrium. (See FIG. 3) The curved tip should either rest within the right atrium if one uses the cavo-atrial cannula with a first openings and a second openings or the inferior vena cava if one uses the cavo-atrial cannula with a first openings, a second openings, and a third openings. Alternatively, one makes an incision in the inferior vena cava and inserts the cavo-atrial cannula into the inferior vena cava. One then advances the cavo-atrial cannula through the inferior vena cava to the right atrium. (See FIG. 3) The curved tip should either rest within the right atrium if one uses the cavo-atrial cannula with a first openings and a second openings or the superior vena cava if one uses the cavo-atrial cannula with a first openings, a second openings, and a third openings. Caution must be exercised when the cavo-atrial cannula is inserted into the inferior vena cava because the extent of the inferior vena cava in the chest is quite short.  
     47. In these improved methods of cardiopulmonary bypass surgery, there are several steps that are performed on the patient prior to the commencement of surgery; these steps are well-known in the art field of surgery and, more specifically, cardiac surgery. After performing these well-known steps, the patient is lying on the operating table, anaesthetized, and has intravenous lines inserted into the patient&#39;s body. Various apparatuses are attached to the patient to monitor the patient&#39;s physiological status.  
     48. To begin cardiopulmonary bypass surgery, one exposes the heart through a sternotomy incision. Heparin or other anticoagulant drug is administered intravenously to prevent clotting of the patient&#39;s blood. Next one makes an incision in the aorta or other artery and inserts an arterial cannula into the artery. One applies a tourniquet around the arterial opening and the arterial cannula to keep the arterial cannula in place and prevent leakage of blood out and entrainment of air into the artery. One attaches tubing to the arterial cannula; the tubing is connected to the pump oxygenator and other various equipment.  
     49. In the improved method of cardiopulmonary bypass surgery, one makes an incision in the superior vena cava and inserts the curved tip of the cavo-atrial cannula into the superior vena cava. Then one inserts the middle portion of the cavo-atrial cannula into the superior vena cava such that the curved tip comes to rest in the right atrium, if the cavo-atrial cannula has two sets of openings, or the inferior vena cava, if the cavo-atrial cannula has three sets of openings. One positions the cavo-atrial cannula such that the second openings,  17 , is located inside the patient&#39;s superior vena cava and pointed toward the patient&#39;s head so that the blood from the head and upper body can enter into the lumen of the cavo-atrial cannula after removal of the obturator from the second openings. Blood in the right atrium and the inferior vena cava can enter the lumen of the cavo-atrial cannula through the first openings or the first openings and third openings, depending on the version of the cavo-atrial cannula used.  
     50. In an alternative improved method of cardiopulmonary bypass surgery, one makes an incision in the patient&#39;s inferior vena cava, and inserts the curved tip of the cavo-atrial cannula into the inferior vena cava. Then one inserts the middle portion of the cavo-atrial cannula into the inferior vena cava such that the curved tip comes to rest in the right atrium, if the cavo-atrial cannula has two sets of openings, or the superior vena cava, if the cavo-atrial cannula has three sets of openings. One positions the cavo-atrial cannula such that the second openings,  17 , is located inside the patient&#39;s inferior vena cava and pointed toward the patient&#39;s feet so that the blood from the lower body can enter into the lumen of the cavo-atrial cannula after removal of the obturator from the second openings. Blood in the right atrium and the superior vena cava can enter the lumen of the cavo-atrial cannula through the first openings or the first openings and third openings, depending on the version of the cavo-atrial cannula used.  
     51. During insertion and positioning of the cavo-atrial cannula, one uses the safe mark,  30 , and reference mark,  31 , on the upper portion,  11 , to make sure that the cavo-atrial cannula is inserted to the proper depth. Also, one uses the rotation mark,  32 , to make sure that the cavo-atrial cannula is in the proper orientation.  
     52. Depending of which embodiment of the obturator that one uses, the steps are different but accomplish the same goal.  
     53. If one uses the obturator that covers the second openings from the lumen of the cavo-atrial cannula, first one detachably secures the cavo-atrial cannula using a variety of methods known in the field. A preferred method is to use a Rummel tourniquet with a pursestring suture to detachable secure the cavo-atrial cannula to the superior vena cava or inferior vena cava. Then, after the cavo-atrial cannula is inserted into the patient&#39;s vena cava and properly secured, one removes the obturator,  25 , by withdrawing the obturator through the open terminus,  15 . After removal of the obturator, one connects tubing to the open terminus of the cavo-atrial cannula.  
     54. If one uses the obturator that covers the second openings from the outside of the cavo-atrial cannula, one loosely detachably secures the cavo-atrial cannula into place using a variety of methods known in the field with the preferable method being a Rummel tourniquet and pursestring suture. Then one uncovers the second openings by removing or moving the obturator. Next, one tightly detachably secures the cavo-atrial cannula into proper position. Then one attaches tubing to the open terminus of the cavo-atrial cannula.  
     55. The Rummel tourniquet or other type of securing mechanism is to prevent blood from leaking out of the incision in the venae cavae and to prevent air from entraining into the venae cavae and becoming entrapped inside the cavo-atrial cannula.  
     56. The tubing attached to the open terminus carries blood to a pump oxygenator or any other device. Gravity drainage is the preferable mode of removal of blood from the body, however, one can also use augmented suction drainage. Other instruments to which the cavo-atrial cannula can be attached may utilize other methods for the draining of blood. Blood is returned from the pump oxygenator to the patient&#39;s body via tubing and the arterial cannula inserted into the aorta or other artery.  
     57. While using the cavo-atrial cannula, cardioplegic solutions is infused into the heart&#39;s blood supply to arrest the heart and/or ice-cold saline is applied topically to the heart, if the surgeon so chooses. Also, blood passing through the pump oxygenator may be cooled. One blocks entry of blood and/or cardioplegic solution into the coronary blood vessels on which one is operating using well-known in the art-field techniques.  
     58. After one completes the surgical tasks that required the diversion of the patient&#39;s blood away from the heart, one first restores cardiac function by flushing out the cardioplegic solutions from the coronary vessels and restores blood flow to the coronary blood vessels. Next one removes the tourniquets from the vena cava. Once the temperature of the patient is normal, one weans the heart from the cardiopulmonary bypass equipment, such as the pump oxygenator and/or other equipment, by progressively decreasing the pump flow rates. Then one removes the cavo-atrial cannula from the vena cava and sutures close the cannulation hole in the vena cava. One also removes the arterial cannula and sutures close the hole in the artery or aorta. Reversal of the effects of the anticoagulation drugs is accomplished by administering protamine or a similar acting drug. Then one places temporary pacing wires on the heart to help control the heart&#39;s rhythm and inserts temporary drains to remove any fluid accumulation around the heart. Finally one closes the chest. Other post-operative care is provided to the patient which is well-known in the art field of surgery and more specifically cardiac surgery.  
     59. When one desires to perform surgery with the patient&#39;s right atrium opened, such as during mitral valve surgery, one must divert the patient&#39;s blood from the body to a pump oxygenator prior to the entry of blood into the right atrium, and then return the blood to the patient&#39;s body via an artery or aorta. In such a manner, one can prevent blood from interfering with the surgery and prevent massive air locks in the venous drainage tubing. For this type of surgery through an atrium, one can use the cavo-atrial cannula to remove blood from the patient&#39;s body. In this method, the cavo-atrial cannula would be approximately fifteen centimeters from the curved tip to the second openings. One would use a cavo-atrial cannula with only the first openings and the second openings.  
     60. In this method, there are several steps that are performed on the patient prior to the commencement of surgery; these steps are well-known in the art field of surgery and more specifically cardiac surgery. After performing all of these well-known steps, the patient is lying on the operating table, anaesthetized, and has intravenous lines inserted into the patient&#39;s body. Various apparatuses are attached to the patient to monitor the patient&#39;s physiological status.  
     61. To begin the cardiac surgery, one exposes the heart through a sternotomy incision. Heparin or other anticoagulant drug is administered intravenously to prevent clotting of the patient&#39;s blood. Next one makes an incision in the aorta or other artery and inserts an arterial cannula into the artery. One applies a tourniquet around the arterial opening and the arterial cannula to keep the arterial cannula in place and prevent leakage of blood out and entrainment of air into the artery. One attaches tubing to the arterial cannula; the tubing is connected to the pump oxygenator and other various equipment.  
     62. In the improved method of cardiac surgery, one makes an incision in the superior vena cava and inserts the curved tip of the cavo-atrial cannula into the superior vena cava. Then, one inserts the middle portion of the cavo-atrial cannula into the superior vena cava such that the curved tip comes to rest in the inferior vena cava. One positions the cavo-atrial cannula such that the second openings face toward the patient&#39;s head so that all the blood flowing down the superior vena cava from the head and upper body can enter into the lumen of the cavo-atrial cannula upon uncovering of the second openings and be diverted away from the heart. The blood from the lower body enters the cavo-atrial cannula from the inferior vena cava through the first openings and is diverted away from the heart.  
     63. In an alternative improved method of cardiac surgery, after the arterial tubing is connected to the arterial cannula and pump oxygenator, one makes an incision in the inferior vena cava and inserts the curved tip of the cavo-atrial cannula into the inferior vena cava. Then, one inserts the middle portion of the cavo-atrial cannula into the inferior vena cava such that the curved tip comes to rest in the superior vena cava. One positions the cavo-atrial cannula such that the second openings face toward the patient&#39;s legs so that all the blood flowing up the inferior vena cava from the lower body can enter into the cavo-atrial cannula upon uncovering of the second openings and be diverted away from the heart. The blood from the head and upper body enters the cavo-atrial cannula from the superior vena cava through the first openings and is diverted away from the heart.  
     64. During insertion and positioning of the cavo-atrial cannula, one uses the safe mark,  30 , and reference mark,  31 , on the upper portion,  11 , to make sure that the cavo-atrial cannula is inserted to the proper depth. Also, one uses the rotation mark,  32 , to make sure that the cavo-atrial cannula is in the proper orientation.  
     65. Depending of which embodiment of the obturator that one uses, the steps are different but accomplish the same goal.  
     66. If one uses the obturator that covers the second openings from the lumen of the cavo-atrial cannula, first one detachably secures the cavo-atrial cannula using a variety of methods known in the field. A preferred method is to use a Rummel tourniquet with a pursestring suture to detachable secure the cavo-atrial cannula to the superior vena cava or inferior vena cava. Then, after the cavo-atrial cannula is inserted into the patient&#39;s vena cava and properly secured, one removes the obturator,  25 , by withdrawing the obturator through the open terminus,  15 . After removal of the obturator, one connects tubing to the open terminus of the cavo-atrial cannula.  
     67. If one uses the obturator that covers the second openings from the outside of the cavo-atrial cannula, one loosely detachably secures the cavo-atrial cannula into place using a variety of methods known in the field with the preferable method being a Rummel tourniquet and pursestring suture. Then one uncovers the second openings by removing or moving the obturator. Next, one tightly detachably secures the cavo-atrial cannula into proper position. Then one attaches tubing to the open terminus of the cavo-atrial cannula.  
     68. The Rummel tourniquet or other type of securing mechanism is to prevent blood from leaking out of the incision in the venae cavae and to prevent air from entraining into the venae cavae and becoming entrapped inside the cavo-atrial cannula.  
     69. The tubing attached to the open terminus carries blood to a pump oxygenator or any other device. Gravity drainage is the preferable mode of removal of blood from the body, however, one can also use augmented suction drainage. Other instruments to which the cavo-atrial cannula can be attached may utilize other methods for the draining of blood. Blood is returned from the pump oxygenator to the patient&#39;s body via tubing and the arterial cannula inserted into the aorta or other artery.  
     70. Next one applies a tourniquet around the superior vena cava near the junction of the superior vena cava and the right atrium, and around the inferior vena cava near the junction of the inferior vena cava and the right atrium using well-known in the art-field techniques. In such a manner, one prevents the flow of blood into the right atrium and, upon opening of the right atrium, air from entering into the venae cavae. Furthermore, the tourniquets prevent air from entering into the cavo-atrial cannula and becoming entrapped. After securing the tourniquets around the superior vena cava and the inferior vena cava, one arrests the heart by perfusing the coronary vessels with cardioplegic solutions. Topical ice-cold saline or ice may be applied to the heart surface. The patient may be cooled by cooling the blood passing through the pump oxygenator. Next, one makes an incision into the right atrium. One can proceed with the surgery on the mitral valve or other section of the heart.  
     71. After one has completed the surgical tasks that required the diversion of the patient&#39;s blood away from the heart, one first restores cardiac function by flushing out the cardioplegic solutions from the coronary vessels and restores blood flow to the coronary blood vessels. Next one removes the tourniquets from the venae cavae. Once the temperature of the patient is normal, one weans the heart from the cardiopulmonary bypass equipment, such as the pump oxygenator and/or other equipment, by progressively decreasing the pump flow rates. Then one removes the cavo-atrial cannula from the vena cava and sutures close the cannulation hole in the vena cava. One also removes the arterial cannula and sutures close the hole in the artery or aorta. Reversal of the effects of the anticoagulation drugs is accomplished by administering protamine or a similar acting drug. Then one places temporary pacing wires on the heart to help control the heart&#39;s rhythm and inserts temporary drains to remove any fluid accumulation around the heart. Finally one closes the chest. Other post-operative care is provided to the patient which is well-known in the art field of surgery and more specifically cardiac surgery.  
     72. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by terms of the appended claims.