Abstract:
A medical catheter assembly includes a catheter tip coupled to a distal end of an elongate catheter member and is symmetric about a plane defined by a septum of the elongate catheter member. The catheter tip defines first and second lumens, and the catheter tip defines first and second openings in the distal portion of the catheter tip. Each opening of the catheter tip is defined by a respective side surface of the catheter tip. Each opening is in fluid communication with a respective one of the first and second lumens of the catheter tip and with a respective one of a pair of lumens defined by the elongate catheter member. The distance between upper and lower surfaces of the catheter tip decreases from a distal end of the proximal portion toward a closed distal end of the catheter tip.

Description:
[0001]    This application is a divisional of U.S. application Ser. No. 14/852,934, which was filed on Sep. 14, 2015, is entitled, “SYMMETRICAL TIP ACUTE CATHETER,” and is a divisional of U.S. patent application Ser. No. 13/629,915, which was filed on Sep. 28, 2012 and is entitled, “SYMMETRICAL TIP ACUTE CATHETER.” The entire content of U.S. application Ser. No. 14/852,934 and U.S. patent application Ser. No. 13/629,915 is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to a catheter assembly, and, in particular, to a symmetrical tip acute catheter. 
       BACKGROUND 
       [0003]    Catheters are flexible medical instruments intended for the withdrawal and introduction of fluids to and from body cavities, ducts and vessels. Catheters have particular application in hemodialysis procedures, in which blood is withdrawn from a blood vessel for treatment and subsequently returned to the blood vessel for circulation. Hemodialysis catheters can include multiple lumens, such as dual lumen or triple lumen catheters, which permit bi-directional fluid flow within the catheter whereby one lumen, the arterial lumen, is dedicated for withdrawal of blood from a vessel and the other lumen, the venous lumen, is dedicated for returning purified blood to the vessel. During some hemodialysis procedures, a multiple lumen catheter is inserted into a body, and blood is withdrawn through the arterial lumen of the catheter. The withdrawn blood is directed to a hemodialysis unit which dialyzes, or purifies, the blood to remove waste and toxins. Thereafter, the dialyzed blood is returned to the patient through the venous lumen of the catheter. 
         [0004]    Generally, hemodialysis catheters are categorized as either chronic or acute in nature. Chronic catheters typically remain in place for extended periods of time, and may be implanted via surgical dissection. Acute catheters, by comparison, are designed to be placed in a patient under emergent circumstances in which speed of placement is desirable. Acute catheters typically remain in place for only a few days. As such, acute catheters are often more rigid than chronic catheters, given the urgency of placement. 
         [0005]    In hemodialysis catheters, recirculation can occur when purified blood exiting the venous lumen of the catheter is withdrawn directly into the arterial lumen such that purified blood is returned to the dialyzer. As such, recirculation increases the time required to complete the hemodialysis procedure. 
       SUMMARY 
       [0006]    The present disclosure is directed to further improvements in hemodialysis catheters and systems used therewith. A catheter assembly includes an elongate catheter member, and a catheter tip. The elongate catheter member includes a septum defining at least a portion of each of a pair of internal lumens. The catheter tip is coupled to a distal end of the elongate catheter member and is symmetric about a plane defined by the septum. The catheter tip includes a distal portion and a proximal portion, an upper surface, a lower surface, and side surfaces between the upper and lower surfaces, the distal portion including a closed distal end. The catheter tip defines first and second lumens and first and second openings in the distal portion of the catheter tip. Each opening is defined by a respective side surface of the catheter tip. Each opening is in fluid communication with a respective one of the first and second lumens of the catheter tip and with a respective one of the first and second lumens of the elongate catheter member. The distance between the upper and lower surfaces of the catheter tip decreases from a distal end of the proximal end portion toward the closed distal end. The first and second openings are diametrically opposed to one another and may be laser-cut or otherwise formed to have contoured edges to reduce the likelihood of thrombus formation. 
         [0007]    The first and second passages of the catheter tip are in fluid communication with a respective one of the pair of internal lumens of the elongate catheter member such that fluids may pass between the elongate catheter member, the catheter tip, and the first and second opening so that the catheter member is in fluid communication with an outside environment such as an internal body cavity. The pair of internal lumens may be configured for opposing bi-directional fluid flow, as in the case of hemodialysis procedures. In embodiments, one or more connecting members may be disposed between the elongate catheter member and the catheter tip, and the one or more connecting members may define channels to facilitate communication between the elongate catheter member and the catheter tip. Distal ends of the connecting members may be disposed adjacent the proximal ends of the first and second side openings such that fluids exit the connecting members upon reaching the proximal ends of the first and second side openings. 
         [0008]    In embodiments, the distance between the upper and lower surfaces along the proximal portion increases in the distal direction adjacent the distal portion. In another embodiment, the proximal portion of the catheter tip is defined by a curved spheroid region. In still another embodiment, the first and second openings are each an elongate oval. 
         [0009]    In a further embodiment of the present disclosure, the elongate catheter member defines a longitudinal axis and the first and second side openings are spaced a distance along the longitudinal axis from the distal end of the catheter tip. In another embodiment of the present disclosure, the first and second internal lumens are semicircular in cross-sectional shape. 
         [0010]    In still another embodiment, the elongate catheter member and the catheter tip are coupled by at least one connecting member extending therebetween. The at least one connecting member defines a channel in fluid communication with the elongate catheter member and the catheter tip. The at least one connecting member may include a proximal end and a distal end, and the distal end of the connecting member is adjacent one of the first and second side openings. The first and second side openings each have a contoured perimeter. 
         [0011]    In a further embodiment of the present disclosure, a medical catheter includes an elongate tubular member defining a pair of lumens and a longitudinal axis. A pair of diametrically opposed side openings in fluid communication with the respective pair of lumens. Each side opening has a proximal end and a distal end, and each side opening has an elongated substantially z-shaped configuration including a rectangular central portion defining a transverse axis and triangular proximally and distally extending portions. The triangular proximally extending portion defines an apex at the proximal end of the side opening and the triangular distally extending portion defines an apex at the distal end of the side opening. The transverse axis of the rectangular central portion defines an acute angle with the longitudinal axis of the elongate tubular member. The acute angle can be between about fifteen and about seventy-five degrees. In some embodiments, the elongate tubular member includes a septum defining at least a portion of each of the pair of lumens. The septum extends parallel to the longitudinal axis, and the elongate tubular member is symmetrical about a plane defined by the septum. In certain embodiments, the pair of side openings each have contoured edges. In some embodiments, the proximal and distal ends of each of the side openings are rounded. 
         [0012]    Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of a distal portion of a medical catheter including an elongate catheter member and a tip. 
           [0014]      FIG. 2  is a cross-sectional view of the medical catheter of  FIG. 1 , taken along section line  2 - 2  of  FIG. 1 . 
           [0015]      FIG. 3A  is a perspective view of the tip of the catheter of  FIG. 1  including a pair of side openings. 
           [0016]      FIG. 3B  is a side view of the catheter tip of  FIG. 3A . 
           [0017]      FIG. 3C  is a top view of the catheter tip of  FIG. 3A . 
           [0018]      FIG. 4A  is a perspective view of a catheter tip which includes a proximal portion having a changing diameter from the proximal portion to the distal portion. 
           [0019]      FIG. 4B  is a side view of the catheter tip of  FIG. 4A . 
           [0020]      FIG. 4C  is a top view of the catheter tip of  FIG. 4A . 
           [0021]      FIG. 5A  is a perspective view of a catheter tip having a proximal portion with a curved spheroid region. 
           [0022]      FIG. 5B  is a side view of the catheter tip of  FIG. 5A . 
           [0023]      FIG. 5C  is a top view of the catheter tip of  FIG. 5A . 
           [0024]      FIG. 6A  is a perspective view of an alternate embodiment of a catheter tip having diametrically opposed top and bottom planar surfaces and a proximal portion having top and bottom walls which diverge outwardly as the proximal portion approaches a distal portion of the catheter tip. 
           [0025]      FIG. 6B  is a side view of the catheter tip of  FIG. 6A . 
           [0026]      FIG. 6C  is a top view of the catheter tip of  FIG. 6A . 
           [0027]      FIG. 7A  is a perspective view of a catheter tip including diametrically opposed planar top and bottom surfaces and having side openings extending through the distal end of the catheter tip. 
           [0028]      FIG. 7B  is a side view of the catheter tip of  FIG. 7A . 
           [0029]      FIG. 7C  is a top view of the catheter tip of  FIG. 7A . 
           [0030]      FIG. 8A  is a perspective view of a catheter assembly including an elongate catheter member having a pair axially opposed and offset tapered slots. 
           [0031]      FIG. 8B  is a side view of the catheter assembly of  FIG. 8A . 
           [0032]      FIG. 8C  is a top view of the catheter assembly of  FIG. 8A . 
           [0033]      FIG. 9A  is a perspective view of a catheter assembly including side openings having rounded ends. 
           [0034]      FIG. 9B  is a side view of the catheter assembly of  FIG. 9A . 
           [0035]      FIG. 9C  is a top view of the catheter assembly of  FIG. 9A . 
           [0036]      FIG. 10A  is a perspective view of a catheter assembly having a catheter body with a pair of diametrically opposed side openings, each shaped as a tapered slot with rounded ends. 
           [0037]      FIG. 10B  is a side view of the catheter assembly of  FIG. 10A . 
           [0038]      FIG. 10C  is a top view of the catheter assembly of  FIG. 10A . 
           [0039]      FIG. 11A  is a perspective view of a catheter assembly having a catheter body with a pair of diametrically opposed side openings, each having a truncated oval shape with a flat distal wall. 
           [0040]      FIG. 11B  is a side view of the catheter assembly of  FIG. 11A . 
           [0041]      FIG. 11C  is a top view of the catheter assembly of  FIG. 11A . 
           [0042]      FIG. 12A  is a perspective view of a catheter assembly having a catheter body with a pair of diametrically opposed side openings each having a shape defined by a circular distal portion intersecting a smaller circular proximal portion. 
           [0043]      FIG. 12B  is a side view of the catheter assembly of  FIG. 12A . 
           [0044]      FIG. 12C  is a top view of the catheter assembly of  FIG. 12A . 
           [0045]      FIG. 13A  is a perspective view of a catheter assembly having a catheter body with a pair of diametrically opposed side openings each having an L-shape including rectangular slots intersecting in transverse relation. 
           [0046]      FIG. 13B  is a side view of the catheter assembly of  FIG. 13A . 
           [0047]      FIG. 13C  is a top view of the catheter assembly of  FIG. 13A . 
           [0048]      FIG. 14A  is a perspective view of a catheter assembly having a catheter body with a pair of diametrically opposed side openings having a shape defined by a circular distal portion intersecting a circular proximal portion. 
           [0049]      FIG. 14B  is a side view of the catheter assembly of  FIG. 14A . 
           [0050]      FIG. 14C  is a top view of the catheter assembly of  FIG. 14A . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0051]    Embodiments of the presently disclosed catheters are discussed in terms of medical catheters for the administration of fluids and, more particularly, in terms of hemodialysis catheters. However, it is envisioned that the present disclosure may be employed with a range of catheter applications including surgical, diagnostic and related treatments of diseases and body ailments, of a subject. It is further envisioned that the principles relating to the presently disclosed catheters include, for example, hemodialysis, cardiac, abdominal, urinary, intestinal, in chronic and/or acute applications. 
         [0052]    In the discussion that follows, the term “proximal” will refer to the portion of a structure closer to an operator, while the term “distal” or will refer to the portion further from the operator. As used herein, the term “subject” refers to a human patient or other animal. The term “operator” refers to a doctor, nurse or other care provider and may include support personnel. 
         [0053]    Referring now to  FIGS. 1-2 , a catheter  10  includes a catheter body  20  and a catheter tip  40 . The catheter body  20  defines a longitudinal axis “A” and may have a substantially circular cross-section. The catheter body  20  defines a pair of lumens  22 ,  23  extending the length of catheter  10 . Alternately, the catheter  20  may define a third lumen for receiving a guidewire or the like. The lumens  22 ,  23  may include oblong, kidney-shaped, and/or D-shaped cross-sectional configurations. A septum  24  defined by the catheter body  20  is disposed between the adjacent lumens  22 ,  23  and can define at least a portion of each lumen  22 ,  23 . In some embodiments, the catheter tip  40  has a substantially frusto-conical profile. The frusto-conical shape may aid in the insertion of the catheter  10 , for example, in time-sensitive circumstances in which acute catheters are utilized. 
         [0054]    The components of the catheter  10  may be fabricated from materials suitable for medical applications, such as, for example, polymers, silicone and/or polyurethane. The catheter body  20  is flexible and may be formed by injection molding or extrusion. The catheter body  20  may have a preformed bend in its normal condition to facilitate conforming to an internal body cavity or vessel in which the catheter body  20  is to be positioned. Alternatively, catheter body  20  may be substantially straight. 
         [0055]    The catheter tip  40  may be fabricated from material suitable for medical application, including, for example, polymers, silicone, and/or polyurethane. In addition, the catheter tip  40  fabricated from the same material or a different material than catheter body  20 . In some embodiments, catheter tip  40  is formed separately from catheter body  20  and is secured to a distal end portion of the catheter body  20 . In certain embodiments, the catheter tip  40  is integrally or monolithically formed with the catheter body  20 . 
         [0056]    The catheter tip  40  includes a partition  44 . The catheter tip  40  and the partition  44  define the lumens  42 . An outer surface  47  of catheter tip  40  is tapered distally and approaches a closed, distal end  46  to aid insertion of the catheter  10 . While the distal end  46  is shown as having a rounded, blunt profile, other shapes and profiles of the distal end  46  are possible. When the catheter body  20  and the catheter tip  40  are assembled, the lumens  42  of tip  40  are in fluid communication with and are aligned with the lumens  22 ,  23  of the catheter body  20 . Similarly, the septum  24  and the partition  44  are aligned such that lumens  22 ,  23  and the respective lumens  42  define substantially parallel and separate pathways parallel to the longitudinal axis A along the catheter body  20 . At least a distal portion of the septum  24  and a proximal portion of the partition  44  have substantially similar dimensions to provide a smooth transition between the catheter body  20  and the catheter tip  40 . 
         [0057]    The catheter tip  40  may include a pair of proximally extending connecting members  48  that are insertable into lumens  22 ,  23 . The connecting members  48  are spaced to receive septum  24  and define channels  50 . The channels  50  are in fluid communication with the lumens  22 ,  23  of the catheter body  20  when the catheter body  20  and the catheter tip  40  are assembled. The connecting members  48  may engage the lumens  22 ,  23  with an interference or frictional fit, forming a substantially fluid tight seal with lumens  22 ,  23 . Alternatively or additionally, the connecting members  48  may be secured within with lumens  22 ,  23  using chemical adhesives or mechanical coupling, such as by welding. 
         [0058]    Referring now to  FIGS. 3A-3C , a pair of side openings  52  is defined in the outer surface  47  of the catheter tip  40 . The side openings  52  are substantially elongated, oval shaped slots that extend along catheter tip  40  and are symmetrical about the longitudinal axis A. The side openings  52  allow fluid streams F, F′ to travel between an environment, such as an internal body cavity, and the internal lumens  42 . The side openings  52  may have contoured edges formed, for example, by laser cutting, molding with catheter tip  40 , and/or otherwise smoothed to minimize flow disruption and thrombus formation. 
         [0059]    In a hemodialysis application, a proximal end portion of catheter body  20  ( FIG. 1 ) is connected to a dialyzer (not shown) such that blood is withdrawn from a body vessel through one lumen  22  ( FIG. 2 ), the arterial lumen, of the catheter body  20  via the respective side opening  52  of the catheter tip  40  and delivered to a dialyzer for purification. The purified blood is then returned to the body vessel through the second lumen  23 , the venous lumen, of the catheter body  20  via the other side opening  52  of the catheter tip  40 . Because of the symmetrical configuration of the catheter body  20 , and the catheter tip  40  and the lumens  42 , either lumen  22 ,  23  may serve as the arterial lumen or the venous lumen. Because of the configuration of the catheter tip  40 , the blood flow stream F into the side opening  52  communicating with the arterial lumen  22  and the blood flow stream F′ exiting the side opening  52  communicating with the venous lumen  23  are separated such that the degree of fluid recirculation is minimized. 
         [0060]    The symmetrical nature of the catheter tip  40 , the diametrically opposed positioning of side openings  52  along the tip  40 , and the elongated shape of side openings  52  enables the spacing between the fluid stream F′ exiting venous lumen  23  and the fluid stream F entering arterial lumen  22  to be maximized, which minimizes the degree of recirculation of purified blood between the venous lumen  23  and the arterial lumen  22  of the catheter  10  ( FIG. 1 ). Specifically, blood enters proximally through the side openings  52  and exits distally through the side openings  52 . The outer surface  47  and the distal end  46  of the catheter tip  40  provide spacing that substantially minimizes the fluid stream F′ exiting the venous lumen  23  from migrating toward the fluid stream F entering the arterial lumen  22 , which can also minimize the degree of fluid recirculation. 
         [0061]    Referring now to  FIGS. 4A-4C , a catheter tip  140  includes a proximal portion  141  and a distal portion  143 . The distal portion  143  of the catheter tip  140  gradually tapers towards a closed distal end  146 , which may have a blunt or a traumatic shape. The proximal portion  141  increases in diameter in a direction toward the distal portion  143 . The increase in diameter along proximal portion  141  provides a radially expanding surface proximal to side openings  152 . This radially expanding surface can direct fluid stream F′ away from the side openings  152 . The side openings  152  can be similar in configuration to side openings  52  and define an elongated oval configuration formed along the sides of the outer surface  147  of catheter tip  140 . Because of the configuration of the catheter tip  140 , the blood flow stream F into the side opening  152  communicating with an arterial lumen and the blood flow stream F′ exiting the side opening  152  communicating with a venous lumen are separated such that the degree of fluid recirculation is minimized. 
         [0062]    Referring now to  FIGS. 5A-5C , a catheter tip  240  includes a proximal portion  241  and a distal portion  243 . The distal portion  243  has a substantially tapered profile that gradually tapers towards a closed distal end  246 . The catheter tip  240  defines a pair of side openings  252  disposed along opposed sides of the outer surface  247  of the catheter tip  240 . The proximal portion  241  of the catheter tip  240  is a curved spheroid region adjacent the distal portion  243 . The curved spheroid region of the proximal portion  241  provides a radially expanding surface proximal to the side openings  252  that directs fluid stream F′ away from side openings  252  to minimize recirculation of fluid stream F′ in the manner discussed above with respect to catheter tip  140 . 
         [0063]    Referring now to  FIGS. 6A-6C , a catheter tip  340  includes diametrically opposed planar surfaces  354 , a proximal portion  341  and a distal portion  343 . Lateral surfaces  360  of proximal portion  341  diverge outwardly in a direction toward distal portion  343 . Each planar surface  354  extends the length of the catheter tip  340  and converges inwardly approaching a blunt distal end  346 . Side surfaces  362  of the distal portion  343  taper inwardly in a direction approaching the distal end  346 . Side openings  352  are similar to openings  52 ,  152  and  252  discussed above. Each side opening  352  is positioned along a respective side surface  362 . The planar surfaces  354  direct fluid stream F′ away from side openings  352  by providing a path of least resistance for fluid stream F′ to flow toward distal end  346 . The lateral surfaces  360  of the proximal portion  341  also direct fluid outwardly of side openings  352 . 
         [0064]    Referring now to  FIGS. 7A-7C , a catheter tip  440  defines a pair of distally positioned, diametrically opposed side openings  452  along the outer surface of a catheter tip  440 . The side openings  452  extend through a portion of a distal end  446  of the catheter tip  440 . The side openings  452  are in fluid communication with internal lumens  442  of catheter tip  440 . The catheter tip  440  functions in a manner similar to that described above with respect to catheter tip  340  ( FIGS. 6A-6C ). 
         [0065]    Referring now to  FIGS. 8A-8C , a catheter  510  includes an elongated body  520  and a catheter tip  540  supported at the distal end of the elongated body  520 . The elongated body  520  defines first and second lumens (not shown) which extend from a proximal end of the catheter  510  toward the distal end of the catheter  510 . In some embodiments, the catheter tip  540  is substantially conical and tapers inwardly in the distal direction to define a blunt or a traumatic end. 
         [0066]    The catheter body  520  defines first and second side openings  526  diametrically opposed to one another along the length of body  520 . Each side opening  526  is in fluid communication with a respective one of the first and second lumens. Each side opening  526  has an elongated Z-shaped configuration including a rectangular or rhombus-shaped central portion  527   a  and triangular proximal and distal portions  527   b  and  527   c . The apex of the triangular portion  527   b  is at the proximal end of the triangular portion  527   b  and the apex of the triangular portion  527   c  is at the distal end of the triangular portion  527   c . In some embodiments, the rectangular portion  527   a  defines a transverse axis T ( FIG. 8B ) which defines an acute angle θ with a longitudinal axis B defined by the catheter body  520 . For example, the angle θ can be between about fifteen degrees and about seventy-five degrees. In certain embodiments, sidewalls  529  defining a portion of rectangular portion  527   a  and triangular portions  527   b  and  527   c  are substantially parallel to a longitudinal axis B defined by catheter body  520 . 
         [0067]    As discussed above, the side openings  526  are symmetrically positioned on opposite sides of the catheter body  520  and each of the side openings  526  communicates with a respective lumen of the catheter  510 . The side openings  526  facilitate separation of the fluid flow stream F into the arterial lumen of the catheter  510  and the fluid flow stream F′ exiting the venous lumen of the catheter  510 . More specifically, because of the configuration of the side openings  526 , blood flow has a tendency to flow into a proximal end of the side opening communicating with the arterial lumen of the catheter body  520  and exit the distal end of the side opening  526  communicating with the venous lumen of the catheter body  520 . Because of this, the fluid streams F and F′ to and from the catheter  510  are spaced to minimize the degree of recirculation within the catheter body  520 . 
         [0068]    Referring to  FIGS. 9A-9C , a catheter  610  includes a body  620  defining side openings  626  that have rounded proximal and distal ends  627 . The ingress and egress points for fluid flow streams F, F′ through arterial and venous lumens (not shown), respectively, are axially spaced apart as described above. Thus, fluid stream F entering the arterial lumen and fluid stream F′ exiting the venous lumen are circumferentially and axially spaced apart, to minimize the degree of recirculation. As compared to sharp edges, the rounded edges  627  of side openings  626  reduce shear stresses on the blood flow to reduce the likelihood of thrombus formation. 
         [0069]    Referring to  FIGS. 10A-10C , a catheter  710  defines a pair of diametrically opposed side openings  726 , each side opening having a proximal end  727  and a distal end  728 . The side openings  726  have a substantially teardrop-shaped profile with rounded ends. The taper of the teardrop shape of each side opening  726  tapers proximally from the proximal end  727  to the distal end  728 , with the proximal end  727  having a smaller radius of curvature than the distal end  728 . Fluid stream F enters an arterial lumen at the proximal end  727 . Fluid stream of F′ exits a venous lumen at the distal end  728 . Accordingly, proximal and distal flow of fluid streams F, F′ through respective lumens are both axially and circumferentially spaced to minimize recirculation. 
         [0070]    Referring to  FIGS. 11A-11C , a catheter  810  defines a pair of diametrically opposed side openings  826 . Each side opening  826  has a proximal end  827  and a distal end  828  and an elongated, truncated oval shape. The distal end  828  of each side opening  826  has a generally flat or planar shape. Each side opening  826  tapers proximally and narrows toward the respective proximal end  827 , which has a curved shape. Fluid stream F enters an arterial lumen at the proximal end  827  and fluid stream F′ exits a venous lumen at the distal end  828 . Accordingly, proximal and distal flow of fluid streams F, F′ through respective lumens are both axially and circumferentially spaced from one another to minimize recirculation. 
         [0071]    Referring to  FIGS. 12A-12C , a catheter  910  defines a pair of diametrically opposed side openings  926 . Each side opening  926  has a proximal portion  927 , a distal portion  928 , and a substantially pear-shaped profile. The distal portions  928  of each side opening  926  is arcuate and has a first diameter “A 1 ”, and the proximal portion  927  of each side opening  926  is arcuate and has a second diameter “A 2 ” that is smaller than diameter A 1 . The respective proximal portions  927  and distal portions  928  intersect along a transverse axis T′ of catheter  910 . Fluid stream F enters an arterial lumen at the proximal portion  927 , and fluid stream F′ exits a venous lumen at the distal portion  928 . Accordingly, proximal and distal flow of fluid streams F, F′ through respective lumens are both axially and circumferentially spaced relative to one another to minimize recirculation. 
         [0072]    Referring to  FIGS. 13A-13C , a catheter  1010  defines a pair of diametrically opposed side openings  1026 . Each side opening  1026  has a proximal portion  1027  and a distal portion  1028  and has a substantially L-shaped profile. The distal portion  1028  of each side opening  1026  extends across a portion of the surface of the catheter  1010  in transverse relation to a longitudinal axis A′ of catheter  1010 . The proximal portion  1027  of each side opening  1026  extends along a portion of the surface of the catheter  1010  parallel to the longitudinal axis A′ and intersects a respective distal portion  1028 . Fluid stream F enters an arterial lumen at the proximal portion  1027  and exits a venous lumen at the distal portion  1028 . Accordingly, proximal and distal flow of fluid streams F, F′ through respective lumens are both axially and circumferentially spaced from one another. 
         [0073]    Referring to  FIGS. 14A-14C , a catheter  1110  defines a pair of diametrically opposed side openings  1126 . Each side opening  1126  has a proximal portion  1127 , a distal portion  1128 , and a substantially figure eight-shaped profile. The proximal portion  1127  and distal portion  1128  of each respective side opening  1126  each have a shape defined by an arcuate distal portion intersecting an arcuate proximal portion, and are symmetric about a transverse axis B″ of the catheter  1110 . Fluid stream F enters an arterial lumen at the proximal portion  1127 , and fluid stream F′ exits a venous lumen at the distal portion  1128 . Accordingly, proximal and distal flow of fluid streams F, F′ through respective lumens are both axially and circumferentially spaced from one another to minimize recirculation. 
         [0074]    Although the illustrative embodiments of the present disclosure have been described herein with reference to the accompanying drawings, it is to be understood that the disclosure is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the disclosure.