CA1246412A

CA1246412A - Vena caval catheter

Info

Publication number: CA1246412A
Application number: CA000474299A
Authority: CA
Inventors: Alan B. Ranford; David C. Fecht
Original assignee: Sherwood Medical Co
Current assignee: Covidien AG
Priority date: 1984-02-23
Filing date: 1985-02-14
Publication date: 1988-12-13
Also published as: JPH0114794B2; DE3563418D1; JPS60188174A; BR8500631A; EP0159773A1; EP0159773B1; ATE35222T1; US4680029A

Abstract

VENA CAVAL CATHETER

Abstract A vena caval catheter is provided with a distal cage-like catheter tip having a cone connected to the inner side of the distal end of the tip within the cage and with the apex proximally of the distal end of the tip and coincident with the longitundinal axis of the catheter tip. The tip has a distal end and struts having smoothly contoured surfaces.

Description

`` ~2~4~2 This invention relates to vena caval catheters and, more particularly, to a vena caval catheter having a -tip shaped for improved blood flow characteristics.

As is well known, vena caval catheters are used during surgical procedures on the heart or on adjacent blood vessels to connect the vena cavae into a cardiopulmonary by-pass extracorpo-real circulation system. Generally, -the extracorporeal system includes a blood oxygenator, defoamer, heat exchanger to control body temperature, an air bubble trap, a particulate filter, and a blood pump for returning oxygenated blood -to the arterial system of the patient.

In one standard method of employing vena caval catheters to effect venous return catheterization, two vena caval catheters are inserted independently into the atrium. One of the catheters is directed into the inferior vena cava and the other catheter is directed into the superior vena cava. Tourniquets are sometimes used to close the vena cavae about the catheters, so that substantially bloodless surgery may be performed on the heart or ad;acent vessels. Venus blood from the upper extremi-ties of the body flows in the superior vena cava and into the tip o the vena caval or return catheter that is directed into that vena cava. Blood from the trunk and lower extremities of the patient flows in the inferior vena cava and into the tip of the return catheter disposed in that vena cava. In certain cases~ a complete by-pass is not employed, for example, a single vena cava catheter may be used where the heart is not to be opened. For example, a two-stage vena caval or venous return catheter having an open end and sidewall openings may be inserted through the right atrium and into the inferior vena cava for draining venous blood into the extracorporeal circulation system. Venous blood, in such case, can flow from the inferior vena cava into the end opening of the dual-stage catheter and blood from the right atrium can flow into the openings in the sidewall of the catheter. Because the walls of the vena cava are flexible, some - ~2~

vena cava catheters have been provided with molded, cage-like tips so that the walls of the vena cava cannot close the inlet or tip of the catheter.

Known vena caval catheters have not been entirely sat-isactory for one reason or another. The shape of the catheter tip through which blood enters the catheter has, in some cases, resulted in poor hemodynamic properties. For example, surfaces at the tip may effect relatively high flow resistances, thus causing undesire-~5 ~ - la -~ 2 ~ 2 able pressure drops as the blood flows into the catheter tip and this tends to increase blood hemolysis. In some cases, surfaces may not be washed with blood thereby increasing the danger of creating initial stages of thrombosis, especially if anitcoagulant levels become low.
The present invention provides a vena caval catheter which reduces or obviates the above-mentioned disadvantages or problems.
The invention also provides a vena caval catheter having an improved tip resulting in good blood flow character-istics so as to effect reduced pressure drops, reduced hemoly-sis, and reduced chance of initiating thrombosis.
In accordance with one aspect of the present inven-tion, a vena caval catheter is provided which has a catheter -tip that includes a plurality of circumferentially spaced, longitudinally extending struts connected together, a distal end having a smoothly rounded outer surface, and a generally cone-shaped portion connected to the distal end and tapering radially inwardly in the proximal direction.
According to the present invention therefore, there is provided a catheter comprising an elongate tube, and a catheter tip including a proximal end portion connected to one end of said tube, a distal end portion having a smoothly con-toured outer surface, a plurality of circumferentially spaced, longitudinally extending struts each connected at one end to said proximal end portion and at the opposite end to said dis-tal end portion, and a generally cone-shaped member connected to the inner surface of said distal end portion and tapering radially inwardly in the proximal direction. Suitably, each of said struts has an ou~er smoothly contoured periphery throughout the length of the strut. Preferably, said proximal end portion of said tip is generally cylindrical. Desirably,

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the catheter includes a ring integrally connected to the distal end of said proximal end portion and having a smoothly contoured distal end surface, said ring being inte-grally connected to the proximal ends of said s-truts, and said struts being integrally connected to said distal end portion.
More desirably, the apex of said cone-shaped inner surface is substantially coincident with the longitudinal axis of said tip. Suitably, said outer surface of said distal end portion smoothly connects with the outer surface of said cone-shaped member and the radially outer surface of each of said struts.
In one embodiment of the present invention said tube tapers radially inwardly in the distal direction. Suitably, said tube has a plurality of openings in the sidewall thereof.
Preferably, the radially inner and outer corners of the distal side of said ring are smoothly rounded. Desirably, said tube has a distal end portion which tapers radially inwardly in the distal direction and a plurality of openings extending through the sidewall of said distal end portion of said tube.
In a particular aspect thereof the present invention provides a vena caval venous blood return catheter for drain-ing venous blood from a vena cava to an extracorporeal circu-lation system comprising a flexible tube having proximal and distal ends, the proximal end of said tube being adapted for connection in the extracorporeal circulation system, and a catheter tip including a cylindrical connector portion at the proximal end thereof fixedly connected to the distal end of said tube, a ring integrally connected to the distal end of said connector and having a greater outer diameter than said connector to form a shoulder facing the distal end of said

3~ tube, a generally annular distal end member having a smoothly contoured outer distal end surface, a plurality of generally longitudinally extending, circumferentially spaced struts - 2a -integrally connected at their proximal ends to said ring and integrally connected at their distal ends to said distal end member to define a cage having a plurality of windows for the flow of venous blood into said tip and tube, each of said struts smoothly curving radially inwardly adjacent the distal end thereof, said ring having smoothly curving distal wall portions, and a cone having its base connected to the inner side of said distal end member with its apex proximally spaced from said base and substantially coincident with the longitu-1~ dinal axes of said tube and said tip. Suitably, said tube isformed of a plastic material. Desirably, said catheter tip is of plastic material.
The present invention will become apparent from the following detailed description and accompanying drawings in which:
Fig. 1 is a side elevational view of certain organs of a patient including the heart connected to an extracorpo-real system utilizing vena caval catheters made in accordance with the present invention;
Fig. 2 is an enlarged side view of a vena caval catheter of Fig. l;
Fig. 3 is an enlarged side view of the tip of the catheter of Fig. 2;
Fig. 4 is a right end view of the tip of Fig. 3;
Fig. 5 is a cross-sectional view taken along the line 5-5 of Fig. 3;
Fig. 6 is a cross-sectional view taken along the line 6-6 of Fig. 4; and Fig. 7 is a side view of a vena caval catheter in accordance with a modified embodiment of the present inven-tion.
Referring now to the drawings, and particularly to - 2b -.~

z Fig. 1, there is illustrated a portion of a surgical site lO
showing a heart 12, a right atrium l~, and superior and infe-rior vena cavae 16 and 18, respectively. The vena cavae are 3~ ~

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connected by a pair o-f identical vena caval catheters 20 and 22 into a cardio-pulmon-ary by-pass or extracorporeal circulation systern indicated generally at 24. Catheters 20 and 22 are connected by a Y-connector 26 which delivers the venus blood through a tube 28 into the main components of the extracorporeal system 24. System 24 generally will include a blood oxgenator, blood defoamer, blood pump, particulate filter, a bubble trap, and a return tube such as indicated at 30, for returning oxygen-ated blood to the arterial system of the patient, such as by connecting tube 3û to the qorta, indicated at 32.
The walls of the atrium 14 are sealed about catheters 20 and 22 such as by conventional purse string sutures (not shown). Conventional vascular torniquets, 34 and 36 are shown closing off the vena cavae 16 and 18, respectively, from theright atrium 14. As shown, torniquet 34 encircles and is tightened about vena cava 16 and catheter 20 while torniquet 36 is tightened about vena cava 18 and catheter 22. With this system, the heart and lungs of the patient are fully or completely by-passed so that the heart and adjacent vessels may be operated on in the dry state.
Other apparatus, including other catheters such as left ventricular vent and/or atrial vent catheters, may be employed in the extracorporeal system 24 as required.
Since the catheters 20 and 22 are identical, only catheter 20 is shown and described in detail. As seen in Fig. 2, catheter 20 includes a tube 38, and a cage-lilce catheter tip 40 connected to the distal end 42 of tube 38. The tube 38 may be, for example, an extruded flexible tube of a plastic material such as rubber, polyvinyl chloride, polypropylene, or other suitable plastic material. Preferrably9 the tube is of a transparent plastic such as o-F transparent polyvinyl chloride. The catheter tip 40 may be molded From a plastic material such as polyvinyl chloride, polypropylene or other suitable plastic. The proximal end 44 of tube 38 is adapted to be connected as shown in Fig. I to a connector such as Y connector 26. The tube 38 may be slightly tapered with the diameter of the distal end slightly narrower than the proximal end. Also, the distal end of the tube 38 may be beveled radially inward-ly in the distal direction as shown in Fig. 2 to provide a smooth outer surface at the juncture of the tube and tip for reducing hemolysis.
Catheter tip 40 includes a cylindrical proximal end portion 46 having an outer diameter sized to closely fit within the distal end 42 of tube 38, as seen in Fig.
2. End portion 46 of the tip serves as a connector which may be fixed within thebore or lumen 50 of catheter 38, such as by applying a cement or otherwise bonding the connector 46 to the sidewalls of lumen 50.
Referring also to Figs. 3-6, connector 46 has a bore 48 connected in fluid communication with lumen 50 of tube 38 when in the assembled condition, such as shown in Fig. 2. An annular, radially outwardly extending, flange or ring 52 is intreg-ally connected to the distal end of connec-~or 46 and has a grea-ter outer diameter than that of the connector so as ~o provide a radial shoulder 54 which engages the distal end of tube 38. Integral with and extending longitudinally from the ring 52, are four bars or struts 56, 58, 60 and 62. The struts are shown circumferentialIy or angularly equally spaced to provide four windows or openings 64. Tip 40 may have a lesser or greater munber of struts and windows than are shown and described. Thernqin portions of the struts are equally radially spaced from and extend parallel to the longitudinal axes of tube 38 and the tip 40. The distal ends of the struts smooth-10 Iy curve radially inwardiy and are integrally connected to a distal tip end 65 havinga smoothly rounded distal outer end surface indicated generally at 66. As clearly seen in Fig. 4, the distal end 65 is generally circular and has an outer diameter that is less than that oF the bore 48 and inner diameter of the ring 52 so that some blood can Flow in a straight line path through tip 40.
As best seen in Figs. 4 and 5, each of the struts 56-62 is smoothly con-toured or rounded on its radially outer surface to reduce flow resistance and hemoly-sis, qnd the radially inner corners are also smoothly rounded to reduce hemolysis.
Thus, the struts have a smoothly contoured periphery throughout their length andare free of any sharp edges. The outer surfaces of the struts smoothly blend into 20 the outer surface of ring 52 as well as the outer surface of distal end 65. Also, the leading or distal surface 67 of ring 52, as best seen in Figs. 3, 4 and 6, is smoothly contoured or rounded. The ring is rounded at both the radially inner and outer corners of the distal surface 67 to reduce hemolysis.
Catheter tip 40 also has a generally cone-shaped member or cone 70 having its base integrally connected to the inner side of distal end 65 of the tip. The outer surfaces of the cone and distal end 65, as best seen in Figs. 3 and 6, join in a smoothly curving or round juncture so as to avoid blood cell hemolysis and flow restric-tions. The cone 70 extends distally with its longitudinally extending vertical axis and apex, indicated at 72, coincident with the longitudindal axes of the tip 40 and 30 tube 38. Cone 70 is circular in cross~section and its apex is smoothly contoured or rounded. The cone tapers radially inwardly in the proximal direction, the direction in which blood flows through the tip 40, as will be discussed hereafter.
During an operation, for example, when the catheter 20 is conveying blood from superior vena cava 16 to the extracorporeal system 24, as shown in Fig.
1, venous blood flows longitudinally into the distal end 65 of tip 40. Blood flows against the rounded distal tip end surface 66, through windows 64 between the smooth-ly connected and rounded struts 56-62, into the bore 48, and then into lumen 50 of tube 38 to the circulation system 24. Because the distal en;l surface 66 is rounded 69t~

and the cone 70 is smoothly inclined proximally, which is the direction of blood flow, these surfaces do not present a high resistance to blood flowing longitudinally and proximally in or externally of catheter tip 4û. Blood flowing into the tip 4û can flow from the cqge or strut portion into the cylindrical bore 48 without a high resistance to flow since this juncture, indicated at 74 in Fig. 3, is rounded. Also, the smoothly curved or contoured sidewalls of the struts 5û-62 and rounded distal wall portions 67 of the ring 52 allow blood to engage and flow around these smooth or rounded surfaces with little resistance. Some blood can flow in a subs~antially straight axial or longi-tudinal direction through the tip 40. Thus, blood can flow into and about the tip 4û
10 with less turbulance and hemolysis.
The cone 70 not only provides a low resistance to blood flow into the tip 40 and tends to reduce turbulence but it prevents a fluid-flow dead space on theinner side of the distal end 65 of the tip. Eliminating the dead space reduces the chance of causing initial stages of thrombosis that might otherwise occur where the cone 70 is not present and surfaces unwashed by blood are present during extracor-poreal circulation.
Thus, with the cone 70 and the smoothly rounded surfaces as described above, pressure drops and hemolysis of blood, as well as the chance of initial throm-bosis are substantially reduced while the struts tend to prevent collapse or occlusion 20 of the catheter by the sidewalls of the vena cava.
Catheter 20 has a single stage of blood entry and may be used with a second such catheter where total venous blood is to be drained from the vena cavae into the extracorporeal system as in the system shown in Fig. 1. However, catheter 20 may be used to deliver only a portion of the blood from the vena cava in which it is inserted where desired and when the particular surgery or operation permits.
In Fig. 7, a dual stage vena caval catheter 80 is shown which includes a tube 82 having a catheter tip 84 connected to the distal end of the tube. Catheter tip 84 is identical to catheter tip 40 of Fig. 2. Catheter tube 82 has a distal end portion 85 which is tapered radially inwardly toward the distal end and is provided 30 with a plurality of inlet openings or holes 86. Tube 82 will generally have a larger lumen than that of catheter 20. Catheter 80 may be used as a two stage venus return catheter where of all of the vena cavae blood is not required to by-pass the right atrium, for example, during certain operations on blood vessels externally of the heart.
Catheter 80 may be inserted through an opening provided in the atrial appendage and be sealingly secured thereto by conventional purse string sutures.The tip 84 of catheter 80 may extend into the inferior vena cava while the entrance holes 86 are disposed in the right atriumO In such a procedure, the catheter is arranged ~4~

so that blood from the inferior cava flows upwardly into the tip 84 of the catheter and between the catheter and walls of the vena cava toward the right atrium while blood from the superior vena cava flows down into the right atriurn and into the holes 86. The proximal end of tube 82 may be connected to an extracorporeal system such as system 24, for example, by connecting the proximal end of catheter 80 to tube 28. In this case, for example, only a portion of the blood from the vena cavae flows into tube 28 of the s~stem.

Since the construction of tip 84 is ldentical to that of tip 40 of Fig. 2, the sams desirable and advantageous effects previously described in connection with the catheter 20 are pro-vided by catheter 80. That is, because of the described smoothly curved or rounded surfaces and relative dimensions described above in connection with tip 40, the blood that flows into and around the catheter 40 or 80 tends to produce reduced pressure drops, reduced turbulence, and reduced hemolysis. Use of tips 40 and 84 tend to minimize or reduce the chance of initiating throm-bosis since the cone allows blood to pass through the tip withoutcreating a dead space or a blood free space on the proximal side of the distal end of the tip.

Catheter 80 is also shown to include a closure tube or obturator 88. Obturator 88 is a cylindrical plastic tube which when inserted into the tube 82 closes off communication be-tween the tip 84 and the interior of tube 82. Obturator 88 is used during insertlon of the catheter 80 into the right atrium so as to prevent initial blood flow into the catheter or tube 82 and out openings 86 until the openings are within the atrium. After completing the insertion of catheter 80, tube 88 is removed.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A catheter comprising an elongate tube, and a catheter tip including a proximal end portion connected to one end of said tube, a distal end portion having a smoothly contoured outer surface, a plurality of circumferentially spaced, longi-tudinally extending struts each connected at one end to said proximal end portion and at the opposite end to said distal end portion, and a generally cone-shaped member connected to the inner surface of said distal end portion and tapering radially inwardly in the proximal direction.

2. The catheter of claim 1 wherein each of said struts has an outer smoothly contoured periphery throughout the length of the strut.

3. The catheter of claim 2 wherein said proximal end portion of said tip is generally cylindrical.

4. The catheter of claim 3 including a ring integrally connected to the distal end of said proximal end portion and having a smoothly contoured distal end surface, said ring being integrally connected to the proximal ends of said struts, and said struts being integrally connected to said distal end portion.

5. The catheter of claim 4 wherein the apex of said cone-shaped inner surface is substantially coincident with the longitudinal axis of said tip.

6. The catheter of claim 5 wherein said outer surface of said distal end portion smoothly connects with the outer surface of said cone-shaped member and the radially outer surface of each of said struts.

7. The catheter of claim 1 wherein said tube tapers radially inwardly in the distal direction.

8. The catheter of claim 7 wherein said tube has a plurality of openings in the sidewall thereof.

9. The catheter of claim 6 wherein the radially inner and outer corners of the distal side of said ring are smoothly rounded.

10. The catheter of claim 1 wherein said tube has a distal end portion which tapers radially inwardly in the distal direction and a plurality of opening ex-tending through the sidewall of said distal end portion of said tube.

11. A vena caval venous blood return catheter for draining venous blood from a vena cava to an extracorporeal circulation system comprising a flexible tube having proximal and distal ends, the proximal end of said tube being adapted for connection in the extracorporeal circulation system, and a catheter tip including a cylindrical connector portion at the proximal end thereof fixedly connected to the distal end of said tube, a ring integrally connected to the distal end of said connector and having a greater outer diameter than said connector to form a shoulder facing the distal end of said tube, a generally annular distal end member having a smoothly contoured outer distal end surface, a plurality of generally longitudinally extending, circumferentially spaced struts integrally connected at their proximal ends to said ring and integrally connected at their distal ends to said distal end member to define a cage having a plurality of windows for the flow of venous blood into said tip and tube, each of said struts smoothly curving radially inwardly adjacent the distal end thereof, said ring having smoothly curving distal wall portions, and a cone having its base connected to the inner side of said distal end member with its apex proximally spaced from said base and substantially coincident with the longitudinal axes of said tube and said tip.

12. The catheter of claim 11 wherein said tube is formed of a plastic material.

13. The catheter of claim 12 wherein said catheter tip is of plastic mater-ial.

14. The catheter of claim 11 wherein said ring has an outer diameter substantially equal to the outer diameter of the distal end of said tube.

15. The catheter of claim 11 wherein a distal portion of said tube tapers radially inwardly in the distal direction.

16. The catheter of claim 14 wherein said distal portion of said tube has a plurality of opening in the sidewall thereof.

17. The catheter of claim 11 wherein said ring has an inner diameter greater than the outer diameter of said distal end member to provide straight line liquid flow through said tip.

18. The catheter of claim 17 wherein the outer diameter of said ring is substantially the same as the outer diameter of the distal end of said tube and where-in said distal end of said tube is engaged by said shoulder.

19. The catheter of claim 18 wherein the radially outer surface of each of said struts connects with the radially outer surface of said ring substantially in a smooth straight line fashion, and the radially inner surface of each of said struts smoothly connects with the radially inner walls of said connector.

20. The catheter of claim 11 wherein the apex of said cone is smoothly rounded, the outer surface of the base smoothly connects with the outer surface of said distal end member, and said cone is circular in cross-section.