Direct stick tear-away introducer and methods of use

A direct stick tear-away introducer having an elongate intraluminal medical device, comprising a proximal and a distal end. A sheath is disposed about the medical device and extends from the distal end of the medical device. A blade is bonded to a distal end of the sheath, and a weakened region on the sheath extends longitudinally from the distal end to a proximal end of the sheath. The introducer has the ability to incise a body tissue and allow insertion of a medical device housed within the introducer into the body tissue. Methods for using the devices herein are also disclosed.

FIELD OF THE INVENTION
 The present invention relates generally to inserting an introducer into a
 body tissue or cavity, including a patient's vascular system, and more
 particularly, to an introducer which provides access for medical devices,
 such as infusion catheters, pressure monitors, filters, balloon occluders,
 and/or cardioplegia catheters.
 BACKGROUND OF THE INVENTION
 A cannula is commonly used to introduce a catheter into a body cavity, such
 as a blood vessel. After the catheter has been inserted into the body
 cavity, the cannula, if left in place, may interfere with a surgical
 field. Removal of the cannula, therefore, is often desired. However, it is
 sometimes difficult to remove the cannula due to frequently enlarged
 proximal end of the catheter. This problem has been alleviated by
 splitable cannulas, which can be removed from a patient's blood vessel by
 separating into two parts, as described in U.S. Pat. Nos. 4,865,593,
 5,104,388, and 5,318,542, all of which are incorporated herein by
 reference. Although the disclosed splitable cannulas are easy to remove,
 they all require an access mechanism to incise the blood vessel for
 insertion. Moreover, a distal end of a catheter, housed within the
 splitable cannula, often protrudes from the distal end of the cannula, and
 thus can be damaged by sometime calcific plaque of the blood vessel walls.
 A need, therefore, exists for a cannula system which provides easy access,
 protection, and insertion of a medical device into a body tissue, and is
 removable by sliding.
 SUMMARY OF THE INVENTION
 The present invention provides a cannula system having the ability to
 incise a body tissue and allow insertion of a medical device housed within
 the cannula into the body tissue. The cannula system is a direct stick
 tear-away introducer which comprises an elongate intraluminal medical
 device having a proximal and a distal end. A sheath is disposed about the
 medical device and extends from the distal end of the medical device. A
 retractable blade is bonded to a distal end of the sheath, and a weakened
 region on the sheath extends longitudinally from the distal end to a
 proximal end of the sheath. The proximal end of the sheath may include a
 handle. The weakened region of the sheath may be a line of perforation.
 The sheath can be made from plastic, polycarbonate, or other suitable
 materials. The blade at the distal end of the sheath can be made of
 stainless steel, nitinol, or other suitable material. The blade may
 further have a lubricious coating with split to facilitate tear-away
 action. The sheath may extend from the distal end to the proximal end of
 the medical device. The medical device, therefore, is protected from
 damage during insertion.
 The present invention also provides methods for introducing a medical
 device, including infusion catheters or cannulas, pressure monitors,
 balloon occluders, filters, or aspirators into a body tissue by providing
 a tear-away sheath, which is disposed about the medical device, and has a
 weakened region extending longitudinally and a blade bonded to its distal
 end. An incision in the body tissue is made using the blade bonded to the
 distal end of the sheath. The medical device is advanced into the body
 tissue through the incision, and the sheath and blade are removed by
 separating the sheath along its weakened region. In an alternative
 embodiment where the proximal end of a direct stick tear-away introducer
 has a handle, the sheath and blade can be removed by pulling on the
 handle. In this way, a medical device is introduced into a body tissue by
 the direct stick tear-away introducer, which can be easily removed and
 obviates the need for an access mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The devices and methods disclosed herein can be used for deployment of
 various medical devices, including infusion catheters, aspirators, balloon
 occluders, filters, and cardioplegia catheters into a body tissue or
 cavity. FIG. 1 depicts a preferred embodiment of a direct stick tear-away
 introducer carrying a cannula in its lumen. Cannula 5 has proximal end 7
 and distal end 8 which is housed within introducer lumen 3. The introducer
 has perforation 10 on sheath 4 extending longitudinally from proximal end
 1 to distal end 2. Retractable blade 20 is bonded on the distal end of the
 sheath.
 FIG. 2 depicts an alternative embodiment of a direct stick tear-away
 introducer having handle 12 at proximal end 1. The handle may facilitate
 separation of the introducer sheath along perforation line 10.
 FIGS. 3 and 4 depict a cross-sectional view of a direct stick tear-away
 introducer at a perforating point. The introducer has outer layer 31 and
 inner layer 32. The inner and outer layers of the introducer are
 continuous at perforation 10. In FIG. 4, two longitudinal wedges 33 and 34
 penetrate the inner layers. Other geometric cuts in the inner layers are
 also possible to provide easy tear-away of the introducer sheath.
 The length of a direct stick tear-away introducer is generally between 5
 and 30 centimeters, preferably approximately 15 centimeters. The outside
 diameter of the introducer is generally between 0.5 and 2.0 centimeters,
 preferably approximately 1.5 centimeters. 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.
 FIG. 5 depicts a cannula deployed in an aorta using a direct stick
 tear-away introducer. The cannula has balloon occluder 9 mounted at its
 distal end. After an incision is made in aorta 40 by retractable blade 20,
 the introducer, housing the cannula, is inserted into the aorta. In this
 way, the cannula and especially the balloon occluder are protected from
 puncture by the sometimes-calcific plaque of the aortic walls. The cannula
 is then advanced distally into the aorta, and the balloon occluder is
 inflated to occlude the aortic lumen. The introducer may be withdrawn
 outside the aorta and removed by separating its sheath along perforation
 10.
 Methods disclosed herein can be used for cannulation of any body tissue,
 and are particularly useful in deployment of an arterial cannula in
 minimally invasive coronary artery bypass grafting surgery for delivering
 oxygenated blood from a cardiopulmonary bypass machine and for occluding
 the aortic lumen to provide arterial isolation of heart and coronary blood
 vessels from the peripheral vascular system. In a port-access approach
 (see Reichenspumer et al., Annals of Thoracic Surgery 65:413-419 (1998),
 incorporated herein by reference) after a patient is under general
 anesthesia, a small incision is made in the intercostal space for
 insertion of the cannula. The direct stick tear-away introducer housing
 the arterial cannula can be inserted through the access port, and the
 sheath and blade are removed by separating the sheath along its weakened
 region. Therefore, methods disclosed herein provide a time-efficient way
 for aortic cannula especially in minimally invasive surgery.
 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.