Abstract:
An introducer system having an elongate shaft with proximal and distal ends. A flexible sleeve is mounted on the distal end of the shaft and is adapted to circumferentially cover the outer surface of a distal end of a cannula when the shaft is positioned within a lumen of the cannula. The introducer system has dilation capabilities which facilitates insertion of a medical device into a vessel or organ. Methods of using the devices herein are also disclosed.

Description:
This is a continuation of U.S. application Ser. No. 09/547,953, filed Apr. 12, 2000, now U.S. Pat. No. 6,569,182, which is a continuation of U.S. application Ser. No. 09/149,981, filed Sep. 9, 1998, now U.S. Pat. No. 6,093,173, all of which are expressly incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to an introducer system having dilatation capabilities to facilitate insertion of a medical device into a body tissue, including a patient&#39;s vascular system. More particularly, the introducer protects the medical device from damage and the body tissue from trauma during insertion. 
     BACKGROUND OF THE INVENTION 
     Catheters or cannulas with relatively large diameters are commonly used in various surgical procedures, which include draining fluid from a body cavity, delivering fluid to a body tissue, and introducing surgical and diagnostic tools. To access a body tissue for insertion of these large catheters or cannulas, a guidewire is traditionally used, as described by Seldinger in  Br. J.  2(6026):21-22 (1976), incorporated herein by reference in its entirety. For example, to insert an internal jugular cannula to provide venous drainage for cardiopulmonary bypass during coronary artery bypass grafting surgery, a patient&#39;s right internal jugular vein is first punctured by a small diameter needle. A guidewire is then inserted through the needle into the internal jugular vein. The needle is withdrawn, leaving the guidewire in the blood vessel. A dilator is inserted over the guidewire into the puncture site to enlarge the opening into the internal jugular vein. The dilator is removed and the venous drainage cannula is inserted over the guidewire into the internal jugular vein. After final placement of the cannula, the guidewire is removed, leaving the cannula in the internal jugular vein and available to drain venous blood to a cardiopulmonary bypass machine. In this approach, dilators are used to enlarge an opening on the body tissue for inserting cannulas, and therefore, often traumatize the body tissue. 
     To reduce the trauma associated with these access devices, thin wall construction using elastomeric materials has been attempted. However, access devices formed of these materials possess a tendency to buckle or bulge during insertion. To overcome the problem of buckling and folding, an adjustable vascular introducer formed of a rolled up plastic sheath in tube form surrounded by a coaxial elastic sheath was described in  Cardiovasc. Intervent. Radiol.  2:169-171 (1989), incorporated herein by reference in its entirety. This device would expand around the oversized portion of a balloon catheter as it passed through the device. This adjustable introducer, however, has an expandable circular cross-section which limits its applicability beyond balloon valvuloplasty. 
     Other introduction devices which utilize a trocar or dilator inside a straight or curved cannula to facilitate insertion of the cannula have been described in Klyce et al., U.S. Pat. No. 4,863,430, incorporated herein by reference. Although these devices simplify the steps for inserting a cannula, they lack the ability to protect the cannula, especially when mounted with fragile, exposed, external balloons, from damage during insertion. 
     A need therefore exists for an introducer system which provides dilation capabilities to facilitate insertion of a medical device into a body tissue, and provides protection for the device and the body tissue from trauma during insertion. 
     SUMMARY OF THE INVENTION 
     The present invention provides an introducer system having the ability to dilate an incision on a body tissue for insertion of a medical device, said introducer further having the ability to protect the medical devices and body tissue from injury during insertion. The introducer system comprises an elongate shaft having a proximal and a distal end. A flexible sleeve is mounted on the distal end of the shaft. When the shaft is positioned within a lumen of a cannula, having a proximal end, a distal end, and a lumen therebetween, the sleeve is adapted to circumferentially cover the outer surface of the distal end of the cannula. The flexible sleeve, which is typically also expandable, may be constructed using elastomeric or lubricious material. The elongate shaft may be made of flexible material, e.g. plastic. In certain embodiments, the shaft may include a coil which also provides flexibility for the shaft. 
     In an alternative embodiment, the proximal end of the shaft may have a collet and a screw lock proximal to the collet adapted for securing the introducer in the lumen of a cannula. The screw and collet also provide a hemostatic seal for the cannula. The distal end of the elongate shaft may include an angulated tip which enlarges an opening into a body tissue, thereby facilitating insertion of a cannula. 
     The present invention also provides methods for introducing a cannula into a body tissue, including a patient&#39;s blood vessel. The methods employ an introducer insertable within a lumen of the cannula, said introducer having a proximal and distal end, and a flexible sleeve mounted on the distal end of the shaft and adapted to cover a distal end of the cannula. After an incision is made on the body tissue, the distal end of the cannula is inserted through the incision into the body tissue with the sleeve covering the outer surface of the distal end of the cannula. This feature is particularly significant in a cannula having an expandable balloon mounted at its distal end in that the balloon is protected from being punctured by the sometimes—calcific plaque of a vessel wall. After final placement of the cannula, the elongate shaft is retracted, whereby the sleeve is inverted and drawn into the lumen of the cannula, thereby removing the sleeve from the outer surface of the distal end of the cannula. The shaft and sleeve are subsequently withdrawn from the lumen of the cannula. 
     It will be understood that there are many advantages to using an introducer/dilator with balloon protection as disclosed herein. For example, the introducer of the present invention provides (1) dilatation capability, thereby obviating the need for another dilator, (2) a flexible shaft which can be easily accommodated in any curved or straight cannula, (3) protection for a body tissue from trauma during insertion, (4) protection for a medical device from being damaged during insertion, (5) a shaft and sleeve which are easily removed after final placement of the medical device, and (6) a restraint on the outer diameter of the medical device which helps to minimize the cross-sectional profile of the device for insertion into a vessel or other body tissue. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a preferred embodiment of an introducer/dilator with balloon protection. 
     FIG. 2 depicts an alternative preferred embodiment of an introducer/dilator with balloon protection. 
     FIG. 3 depicts a distal end of an introducer/dilator without balloon protection. 
     FIG. 4 depicts an end view of the tip depicted in FIG.  3 . 
     FIG. 5 depicts an introducer/dilator with balloon protection positioned within a lumen of a cannula entering an aorta. 
     FIG. 6 depicts withdrawal of the introducer/dilator with balloon protection as depicted in FIG.  5 . 
     FIG. 7 depicts the cannula of FIG. 6 connected to a bypass-oxygenator machine. 
     FIG. 8 depicts withdrawal of the introducer/dilator with filter protection. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The devices and methods disclosed herein facilitate insertion of various medical devices, including infusion catheters, aspirators, balloon occluders, pressure monitors, and arterial or venous catheters. A preferred embodiment of an introducer/dilator with balloon protection according to the invention is illustrated in FIG.  1 . The introducer/dilator has proximal end  1 , distal end  2 , and elongate shaft  3 . Distal end  2  further comprises tip  10  adapted for insertion into a body tissue. Flexible sleeve  5  is mounted proximal to tip  10  for protecting a medical device. 
     An alternative embodiment of the introducer/dilator with balloon protection is illustrated in FIG.  2 . In this embodiment, elongate shaft  3  further comprises a coil  12  to provide flexibility. Proximal end  1  has collet  15  and screw lock  16  adapted to securely engage a proximal end of a medical device, thereby locking the introducer securely within a lumen of the medical device. 
     FIG. 3 depicts a distal end of an introducer/dilator without balloon protection. In this embodiment, tip  10  is constructed using a plurality of geometric shapes. This is further illustrated in FIG. 4 which depicts an end view of the tip having three prisms  20 , each extending distally and sharing a common point  22  at a vertex. Construction of the tip utilizing other numbers of different geometric cuts is also possible to facilitate insertion and dilation in a body tissue. 
     The length of the elongate shaft is generally between 3 and 15 inches, preferably approximately 7 inches. The diameter of the elongate shaft is generally between 0.05 and 0.25 inches, preferably approximately 0.127 inches. The length of coil from the distal end of the elongate shaft is generally between 2 and 5 inches, preferably approximately 3.5 inches. The foregoing ranges are set forth solely for the purpose of illustrating typical device dimensions. The actual dimensions of a device constructed according to the principles of the present invention may obviously vary outside of the listed ranges without departing from those basic principles. 
     Methods of using the invention are illustrated in FIGS. 5 and 6. FIG. 5 depicts an introducer/dilator with balloon protection positioned within a lumen of a cannula entering an aorta. During cardiopulmonary bypass, cannula  25  having expandable balloon  30  mounted at distal end  40  is inserted into a patient&#39;s ascending aorta  50  to provide circulatory isolation of the heart and coronary blood vessels from the peripheral vascular system. The cannula has lumen  26  for delivering oxygenated blood from the bypass oxygenator machine  55  to the aorta. Expandable balloon  30  is in communication with inflation lumen  32  and inflation port  34 . Distal region  40  of the cannula is angled in relation to proximal region  42 . Elongate shaft  3  is also angled within the cannula lumen at coil  12 . Tip  10  protrudes from distal opening  44  of the cannula. A collet  15  and screw lock  16  secure the introducer/dilator at the proximal region of the cannula. 
     When in use, the cannula  25  containing the introducer/dilator with balloon protection is introduced through an incision made on the aorta  50 . Tip  10  facilitates entry of the cannula by enlarging the incision on the aorta, thereby functioning as a dilator. As distal region  40  of the cannula enters the incision, flexible sleeve  5  protects the distal end of the cannula and expandable balloon  30  from damage by the sometimes—calciflc aortic plaque. The flexible sleeve also protects the aorta from blunt trauma during insertion of the cannula. After the cannula is positioned within the aorta, screw lock  16  is disengaged at the proximal region of the cannula so that shaft  3  and sleeve  5  can be withdrawn proximally. As the shaft is withdrawn into the lumen of the cannula, flexible sleeve  5  is inverted, thereby releasing the balloon as shown in FIG.  6 . As shown in FIG. 7, after the shaft and sleeve are completely removed from the lumen of the cannula, the balloon can be inflated through inflation lumen  32  and inflation port  34  to occlude the aorta, thereby providing isolation of the heart and coronary blood vessels from the peripheral vascular system. Cardiopulmonary bypass can then be initiated by delivering oxygenated blood from a bypass-oxygenator machine  55  to the aorta (shown in FIG.  7 ). The bypass-oxygenator machine  55  can be connected to the cannula  25  through fitting  53 . 
     In addition to the aortic cannula described above, the devices and methods disclosed herein can be utilized in inserting other medical devices into blood vessels or organs, such as atherectomy devices, angioplasty catheters, coronary sinus catheters, percutaneous gastrostomy tubes, intra-aortic balloons, suprapubic catheters, and aortic cannulas with filter  100  as disclosed in Barbut et al., U.S. Pat. No. 5,769,816, incorporated herein by reference in its entirety. FIG. 8 shows the present invention in use with such a filter. 
     Although the foregoing invention has, for the purposes of clarity and understanding, been described in some detail by way of illustration and example, it will be obvious that certain changes and modifications may be practiced which will still fall within the scope of the appended claims.