Blood vessel catheter

Details Blood vessel catheter Blood vessel catheter

2001-01-11

2004-03-09

Casler, Brian L. (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Material introduced into and removed from body through...

C604S006160, C604S524000, C138S177000

Reexamination Certificate

active

06702776

ABSTRACT:

FIELD OF THE INVENTION
This invention relates in general to medical catheters and, more particularly, to blood vessel catheters. In one aspect of the invention it relates to hemodialysis catheters.
BACKGROUND OF THE INVENTION
Blood vessel catheters are normally either venous catheters or arterial catheters. Venous catheters, in turn, usually come in several forms. The simplest are short peripheral catheters. Next come midline catheters, central venous catheters and port catheters. A hemodialysis catheter is one form of central venous catheter and is normally placed in the superior vena cava. The present invention may find application in each of the aforementioned venous catheters. However, it finds particularly advantageous application in hemodialysis catheters.
Hemodialysis, as practiced today, normally employs one of two types of catheter to remove blood from the patient for processing and return processed blood to the patient. Most commonly, a catheter tube containing two lumens is used, each lumen having a semi-cylindrical configuration. This is frequently referred to as a dual lumen catheter. Alternatively, two separate tubes, each with a full cylindrical configuration, may be used to remove blood for dialysis and return the processed blood.
Hemodialysis membranes are now able to process blood at over 500 ml of flow per minute. Even higher processing rates are foreseeable. However, problems occur with both the line introducing purified blood back into the vein (the venous line) and the line removing blood for purification (the arterial line) at flow rates above 300 ml per minute. A high flow rate from the venous line can cause whipping or “firehosing” of the tip in the vein with consequent damage to the vein lining. A corresponding high flow rate into the arterial line causes the port to be sucked into the vein wall, resulting in occlusion. It should be understood, of course, that both lines normally access the superior vena cava and the designations are used for differentiation purposes.
Speed of flow through a catheter lumen, whether it be in a single lumen or a dual lumen catheter, is controlled by a number of factors including the smoothness of the wall surface, the internal diameter or cross-sectional area of the tube lumen, and the length of the tube lumen. The most important factor is the cross-sectional area of the tube lumen. The force or speed of the fluid flow in a tube lumen for a given cross-sectional area is controlled by the external pumping force, of course. This is a positive pressure pushing processed blood through the venous lumen and a negative (suction) pressure pulling unprocessed blood through the arterial lumen.
Problems encountered in providing for a high flow rate through a catheter are magnified in a dual lumen catheter construction. Because each of the lumens in a dual lumen catheter has a D-shape, it has been assumed that flow rates are limited. Furthermore, such dual lumen catheters are, to a great extent, catheters with a main port which opens at the end of a lumen substantially on the axis of the lumen. Thus, firehosing frequently results. There are dual lumen catheters which utilize side ports for both outflow and inflow. An example is the catheter disclosed in the Cruz et al. U.S. Pat. No. 5,571,093. However, such catheters have not been successful in solving numerous problems related to hemodialysis with dual lumen catheters, e.g., high incidences of catheter port occlusion as well as some degree of fire-hosing still occurs.
A flow balance between the venous and arterial lines is also of obvious importance. Occlusion of the arterial line is a very common limiting factor in hemodialysis. While the venous line tends to remain clear and open, because the direction of flow forces tube ports away from the vein wall, in the arterial line this high flow tends to pull the port against the vein wall, thereby sucking the wall into the port and occluding it. Andersen et al. U.S. Pat. No. 4,594,074, Quinn U.S. Pat. No. 5,451,216, Quinn U.S. Pat. No. 5,810,787, Quinn U.S. Pat. No. 5,599,322 and Quinn U.S. Pat. No. 5,571,093 all discuss the need for improved aspiration in catheters generally.
Additionally, some key problems face dialysis clinicians using dual lumen central venous catheters or catheters placed via the jugular route. Clinicians routinely face a situation where either the venous or the arterial lines fail to function during dialysis, or when the patent is first connected to the dialysis machine. The dialysis center clinician must find a way to make the system work as he or she does not have the option of immediately changing the catheter. Failure is most often on the arterial or pulling side, where the catheter port is sucked against the vessel wall. Occlusion can also be caused by a combination of clots and the proximity of the vessel wall. The problem is frequently addressed by reversing the lines, by flushing the lines with saline and/or by repositioning the patient so that gravity can help move the catheter tip way from the vessel wall. Insofar as reversing the lines is concerned, although it can be very effective, it also may result in ineffective dialysis because venous (dialyzed) and arterial blood tend to mix more easily when venous blood is then being directed at the arterial port instead of away from it.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved blood vessel catheter.
Another object is to provide a blood vessel catheter which substantially reduces the opportunity for occlusion to occur during outflow.
Another object is to provide an improved hemodialysis catheter which is capable of delivering processed blood to the patient at high flow rates without harmful firehosing or whipping of the catheter tip.
A further object is to provide a hemodialysis catheter which is capable of returning processed blood to the patient at flow rates of 500 ml or greater without traumatizing the patients blood vessel.
Yet a further object is to provide a hemodialysis catheter which permits high flow rates while minimizing trauma and potential red cell and platelet damage so as to avoid clotting.
Yet another object is to provide a hemodialysis catheter which permits substantially increased venous flow rates while reducing output force and increasing the diffusion rate.
Another object is to provide a dual lumen hemodialysis catheter which permits flow rates higher than the latest separate lumen catheters without harmful firehosing of the catheter tip.
Yet another object is to provide a dual lumen hemodialysis catheter which permits high flow rates while minimizing trauma and potential red cell and platlet damage so as to substantially avoid clotting.
A further object is to provide a dual lumen hemodialysis catheter which substantially reduces the incidence of arterial port occlusion.
Still a further object is to provide a dual lumen hemodialysis catheter in which flow can be reversed without significant mixing of venous and arterial blood.
Yet a further object is to provide new and improved bolus tips for dual lumen, hemodialysis catheters.
The foregoing and other objects are realized in accord with the present invention by providing a first embodiment of blood vessel catheter which combines a single lumen catheter tube and a bolus tip. The bolus tip has a bullet nose and a main side port. The catheter has at least one additional radially extending side port displaced axially from the main side port. The additional port or ports are elongated axially of the catheter so as to have a race-track shaped edge. The edge is semi-circular in cross-section.
In one form of the first embodiment, the catheter tube has an elongated cylindrical body, fabricated of thermoplastic material such as polyurethane, or thermoset material such as silicone rubber. An axial passageway or lumen extends the length of the cylindrical body, from a proximal to a distal end. The cylindrical wall which defines the lumen has an axially and circumferentially spaced series of radially extending ports formed in it adjacent the distal end. Eac

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