Abstract:
A catheter has a series of hollow loops arranged along a tube for carrying working fluid from a heat exchange system to exchange heat with a patient in whom the catheter is advanced. The loops when inflated are transverse to the catheter axis and parallel to each other, and circumscribe a hollow passageway through which blood can flow. Blood also flows around the outer perimeters of the loops.

Description:
FIELD OF THE INVENTION 
       [0001]    The present application relates generally to patient temperature control systems. 
       BACKGROUND OF THE INVENTION 
       [0002]    It has been discovered that the medical outcome for a patient suffering from severe brain trauma or from ischemia caused by stroke or heart attack or cardiac arrest is improved if the patient is cooled below normal body temperature (37° C.). Furthermore, it is also accepted that for such patients, it is important to prevent hyperthermia (fever) even if it is decided not to induce hypothermia. Moreover, in certain applications such as post-CABG surgery, skin graft surgery, and the like, it might be desirable to rewarm a hypothermic patient. 
         [0003]    As recognized by the present application, the above-mentioned advantages in regulating temperature can be realized by cooling or heating the patient&#39;s entire body using a closed loop heat exchange catheter placed in the patient&#39;s venous system and circulating a working fluid such as saline through the catheter, heating or cooling the working fluid as appropriate in an external heat exchanger that is connected to the catheter. The following U.S. patents, all of which are incorporated herein by reference, disclose various intravascular catheters/systems/methods for such purposes: U.S. Pat. Nos. 6,881,551 and 6,585,692 (tri-lobe catheter), U.S. Pat. Nos. 6,551,349 and 6,554,797 (metal catheter with bellows), U.S. Pat. Nos. 6,749,625 and 6,796,995 (catheters with non-straight, non-helical heat exchange elements), U.S. Pat. Nos. 6,126,684, 6,299,599, 6,368,304, and 6,338,727 (catheters with multiple heat exchange balloons), U.S. Pat. Nos. 6,146,411, 6,019,783, 6,581,403, 7,287,398, and 5,837,003 (heat exchange systems for catheter), U.S. Pat. No. 7,857,781 (various heat exchange catheters). 
       SUMMARY OF THE INVENTION 
       [0004]    The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
         [0005]    A catheter includes a proximal segment having a supply lumen configured to receive working fluid from a heat exchange system and a return lumen configured to return working fluid to the heat exchange system. The catheter also includes a distal segment in fluid communication with the proximal segment and defining plural spaced apart discrete loops, each communicating with the supply lumen and each being connected to an adjacent loop by a substantially straight connector segment. 
         [0006]    The loops when inflated with working fluid can be toroidal-shaped, disk-shaped, rectangular-shaped or triangular-shaped. Each loop can define a proximal surface and a distal surface parallel to the proximal surface and oriented transversely to a long axis of the return tube. The distal-most loop can be connected to the return lumen. 
         [0007]    Each individual loop may include a supply port communicating with the supply lumen and a fluid channel defined by the loop and a return port communicating with the supply lumen and with the fluid channel of the loop, such that working fluid can circulate through the fluid channel from the supply port to the return port. The ports can be closely juxtaposed with each other and straddle a separator such that working fluid must flow from the supply port substantially completely through the fluid channel to the return port. 
         [0008]    In an aspect, a catheter includes a series of hollow loops arranged along a tube for carrying working fluid from a heat exchange system to exchange heat with a patient in whom the catheter is advanced. When inflated, the loops are oriented transverse to a long axis of the catheter throughout their respective outer peripheries and are parallel to each other. The loops circumscribe a hollow passageway through which blood can flow. The loops are configured such that blood can also flow around the outer peripheries of the loops. 
         [0009]    In an aspect, a method includes providing a heat exchange catheter with a supply lumen configured for receiving working fluid from a heat exchange system and a return lumen configured for returning working fluid to the heat exchange system. The method also includes providing plural discrete loops on the catheter receiving working fluid from the supply lumen and circulating returning working fluid through the loop. The loops are spaced from each other and connected to each other only by a flexible tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic diagram showing an example catheter engaged with an example heat exchange system; 
           [0011]      FIG. 2  is a perspective view of the heat exchange region showing as an example three spaced apart loops on a catheter with a supply and a return lumen and a single infusion lumen for simplicity, it being understood that additional infusion lumens may be provided; 
           [0012]      FIG. 3  is a transverse view of a loop showing the supply and return ports that communicate with the supply and return lumens, respectively of the catheter; 
           [0013]      FIG. 4  is a transverse cross-section as seen along the line  4 - 4  in  FIG. 2 ; 
           [0014]      FIG. 5  is a transverse cross-section of an alternate rectangular embodiment as would be seen along the line  4 - 4  in  FIG. 2 ; 
           [0015]      FIG. 6  is a transverse cross-section of an alternate triangular embodiment as would be seen along the line  4 - 4  in  FIG. 2 ; and 
           [0016]      FIGS. 7  is a cross-section as would be seen along the  7 - 7  in  FIG. 2  of an alternate embodiment in which the supply and return ports of a loop are slightly offset axially; and 
           [0017]      FIG. 8  shows an alternate embodiment of the distal portion of an alternate embodiment in which the return lumen is distanced from the supply lumen except at the proximal-most portion of the catheter to reduce heat exchange between the lumens. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    Referring initially to  FIG. 1 , an intravascular temperature management catheter  10  is in fluid communication with a catheter temperature control system  12  that includes a processor executing logic that in some non-limiting examples is in accordance with disclosure in the above-referenced system patents to control the temperature of working fluid circulating through the catheter  10  in accordance with a treatment paradigm responsive to patient core temperature feedback signals. In accordance with present principles, the catheter  10  can be used to induce therapeutic hypothermia in a patient  14  using the catheter, in which coolant such as but not limited to saline circulates in a closed loop, such that no coolant enters the body. Such treatment may be indicated for stroke, cardiac arrest (post-resuscitation), acute myocardial infarction, spinal injury, and traumatic brain injury. The catheter  10  can also be used to warm a patient, e.g., after bypass surgery or burn treatment, and to combat hyperthermia in, e.g., patient suffering from sub-arachnoid hemorrhage or intracerebral hemorrhage. 
         [0019]    As shown, working fluid such a refrigerant may be circulated between the heat exchange system  12  and catheter  10  through supply and return lines  16 ,  18  that connect to the proximal end of the catheter  10  as shown. Note that as used herein, “proximal” and “distal” in reference to the catheter are relative to the system  12 . A patient temperature signal from a catheter-borne temperature sensor may be provided to the system  12  through an electrical line  20  or wirelessly if desired. Alternatively, a patient temperature signal may be provided to the system  12  from a separate esophageal probe or rectal probe or tympanic sensor or bladder probe or other temperature probe that measures the temperature of the patient  14 . 
         [0020]    The catheter  10 , in addition to interior supply and return lumens through which the working fluid is circulated, may also have one or more infusion lumens connectable to an IV component  22  such as a syringe or IV bag for infusing medicaments into the patient, or an instrument such as an oxygen or pressure monitor for monitoring patient parameters, etc. 
         [0021]    The catheter  10  can be positioned typically in the vasculature of the patient  14  and more preferably in the venous system of the patient  14  such as in the inferior vena cava through a groin insertion point or the superior vena cava through a neck (jugular or subclavian) insertion point. 
         [0022]    Now referring to  FIGS. 2-4 , a first embodiment of the catheter  10 , generally designated  100 , is shown with a plurality of spaced-apart hollow coolant loops  102  that may be made of medical grade balloon material. While the loops  102  are shown in a disk-shape configuration when inflated with working fluid, in other embodiments the loops  102  may be toroidal-shaped when inflated. In both cases, the loops have the ring-shaped circular transverse cross-sections shown in  FIGS. 3 and 4 . Or, the loops may be made to assume an ovular cross-section when inflated. In other embodiments and briefly referring to  FIGS. 5 and 6 , the loops may assume non-round transverse shapes when inflated, e.g., rectangular ( FIG. 5 ), triangular ( FIG. 6 ), or other shapes. 
         [0023]    Returning to  FIGS. 2 and 3 , a series of coolant loops  102  and a flexible connector segment  104  is shown. The flexible connector segment  104  includes a supply lumen  106  and a return lumen  108  and is attached to each loop  102  at the base of each loop  102 . Each loop  102  may be continuously molded to the connector segment  104  or may be attached to the connector segment  104  by means of an adhesive. Additional lumens, such as but not limited to an infusion lumen  110  connected to an IV component  22  such as a syringe or IV bag for infusing medicaments into the patient, or an instrument such as an oxygen or pressure monitor for monitoring patient parameters, etc., may be included as part of the connector segment  104 . The fluid of the infusion lumen  110  is isolated from the working fluid in the supply lumen  106  and the return lumen  108  and may enter the patient  14  through an open distal end of the catheter  100 . 
         [0024]    In the embodiment shown, each loop  102  defines a proximal surface and a distal surface parallel to the proximal surface and oriented transversely to a long axis of the return tube  108 . The loop  102  in  FIG. 3 , illustrated from a proximal perspective, forms a ring with a supply port  112  on the proximal side of the base of the loop  102  and a return port  114  on the distal side of the base of the loop  102 . The working fluid in the proximal supply lumen  106  enters the loop  102  through the supply port  112  and then re-enters the supply lumen  106  through the return port  114 . The illustration of a loop  102  in  FIG. 4  includes a separator  116  situated between the supply port  112  and return port  114 . 
         [0025]    In this embodiment, all but the distal-most loop receives working fluid from the supply lumen  106  on one side of the supply lumen  106  and returns it to the supply lumen  106  on the opposite side of the supply lumen  106 , with the supply lumen  106  being provided with a divider  118  between the two sides to ensure that working fluid flows from the supply lumen  106 , into the supply port  112  of the loop  102 , around the loop  102 , out of the return port  114 , and back into the supply lumen  106 . The distal-most loops has a return port  114  connected to a return lumen  108 , which conveys the working fluid proximally back through the catheter  100  to the heat exchange system  12 . In other embodiments, instead of being radially offset, the supply port  112  and return port  114  of a loop  102  may be slightly axially staggered as shown in  FIG. 7  such that the divider  118  in the supply lumen  106  of the catheter  100  extends axially a short way through the supply lumen  106  as shown in  FIG. 7 . In such an embodiment, the distal and proximal surfaces of the loop  102  will remain generally parallel to each other but may be angled slightly from being absolutely transverse to the long axis of the catheter  100  owing to axial offset of the supply port  112  and return port  114 . 
         [0026]    Note that each loop  102  in the example shown thus receives coolant from the supply lumen  106  and returns it to the supply lumen  106 , except the distal-most loop, whose return port is connected to the return lumen  108 . Note that in addition to the separator  116  within each loop  102  to separate the supply port  112  from the return port  114 , there is also the blockage  118  in the catheter supply lumen  106  to ensure all coolant in the supply lumen  106  flows through the first loop, back into the supply lumen  106  to the next loop, through the second loop, and so on. Also note that the flow can be reversed, i.e., the distal most loop can receive working fluid first before all other loops through an elongated straight supply lumen, with the working fluid then being fed back through the other loops in a proximal direction. In the first case all loops  102  get fed from the supply lumen  106  and the last loop feeds it back to the return lumen  108 ; in the second case the distal loop gets fed from the supply lumen  106 , feeding back the fluid through the return lumen  108  through each subsequent loop in sequence from distal to proximal. 
         [0027]    In the embodiment of the catheter  100  shown in  FIG. 8 , the distal-most loop  102  does not form a complete ring. Rather, the distal-most loop  102  forms a half-ring and connects to the return lumen  108 , which then extends in a proximal direction through the other loops  102 . The working fluid in the supply lumen  106  flows through the loops  102  and back into the supply lumen  106  in a distal-direction until the distal-most loop  102 , at which point the working fluid enters the return lumen  108  and flows in a proximal direction back to the heat exchange system  12 . The supply lumen  106  and return lumen  108  in this embodiment are spaced from each other in order to achieve a decreased amount of heat exchange between elements of the catheter  100  and increased heat exchange between the catheter  100  and the patient  14 . 
         [0028]    While the particular INTRAVASCULAR HEAT EXCHANGE CATHETER WITH MULTIPLE SPACED APART DISCRETE COOLANT LOOPS is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.