Abstract:
A method of cooling an organ. A portion of a body fluid bathing an organ is withdrawn while a cool fluid is infused. A separate portion of the body fluid can be cooled during the withdrawing. A volume of up to about 5% of the body fluid can be withdrawn. A catheter is provided with a cooling mechanism to contact and cool the body fluid. The catheter can have an inlet port to withdraw body fluid and an outlet port to allow infusion of a cool fluid. Additionally, an organ cooling pump assembly is provided including a pump and a catheter.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to treatment of organs. In particular, the present invention relates to treatment of organs that have been subjected to trauma or ischemia. 
     BACKGROUND OF THE RELATED ART 
     When an organ has been injured or its blood supply compromised, timeliness of treatment can be critical. Organ tissue necrosis, or death, begins when the organ&#39;s blood supply is compromised and treatment is ineffective with respect to organ tissue that has died prior to treatment. Nevertheless, the time required for proper diagnosis and treatment of the organ cannot be eliminated. 
     The brain is no exception. Injury to the brain may result from increased pressure due to swelling of brain tissue. For example, swelling may result from internal bleeding such as from a ruptured aneurysm. Alternatively, generalized head trauma may cause swelling of brain tissue. Injury to the brain may also be the result of a lack of oxygen to brain tissue due to an embolus present within a cerebral vessel. Such an embolus can cut off an adequate blood supply to portions of brain tissue. As noted in these examples, perfusion of brain cells is compromised in both trauma and ischemia. 
     When brain tissue is subjected to such traumas noted above the effects as well as the need for treatment are immediate. The rate at which brain tissue dies is dependant on several factors, such as the degree of swelling or, in the case of cerebral embolism, the presence or absence of collateral vessels supplying alternative avenues of perfusion. 
     Treatment of the injured brain first requires a proper diagnosis. A diagnosis pinpointing the originating site of the injury can come from a computed tomography (CT) scan. From a logistical standpoint, a patient that presents, for example at an Emergency Room, with a head trauma will not likely obtain CT scan results in less than half an hour. During this critical time, brain tissue continues to die as a result of the head trauma. 
     Once diagnosed, the treatment chosen will take a significant amount of additional time to carry out. For example, if the brain has been subjected to an ischemic stroke, drugs such as Tissue Plasminogen Activator (TPA) may be given to the patient to help dissolve any thrombus or blood clot. Alternatively, if swelling is of concern, a hole may need to be drilled through the skull to relieve pressure on brain tissue. Additionally, more direct vascular intervention may be required. In such cases a host of catheter lab procedures may be employed. In more extreme cases, actual brain surgery may be required. 
     Regardless of the treatment path chosen, several hours will likely be lost during the course of the treatment. Throughout this time brain tissue will continue to die. The problem is compounded by the fact that the brain tissue cannot be regenerated. 
     In order to combat the problem of brain tissue death attempts have been made to curb the rate of brain tissue death. As noted above, the rate of brain tissue death is affected by factors such as the degree of swelling involved, or the overall lack of oxygen supplied to the affected tissue. Therefore, attempts to curb the rate of brain tissue death have focused on the induction of hypothermia in the patient. Hypothermia can reduce swelling. Tissue affected by hypothermia will also experience a decrease in metabolic requirements, and thus, experience a decrease in need for oxygen. 
     Hypothermia can be induced to reduce the core temperature of a patient. That is, the temperature of the entire body of the patient can be reduced. This can be done by reducing the temperature of the patient&#39;s blood. Reducing even a portion of the patient&#39;s blood will result in a generalized cooling of the body as the blood is carried throughout the body of the patient. However, in the case of a head trauma, a generalized reduction in the core temperature of the patient is limited in effectiveness. Reduction of a body&#39;s core temperature means that hypothermia will not be focused on the brain tissue specifically. Rather, the temperature of the brain tissue, as in the rest of the body, will be reduced by a small amount. Even if the blood of the brain is cooled directly, the focus of this cooling effect will be lost as this cooled blood, along with the remainder of the patient&#39;s blood (e.g. about 5 liters), is circulated throughout the body. In the end, a generalized core temperature reduction is the major effect obtained. This problem is applicable to any organ for which hypothermia is to be induced. Therefore, what is needed is an improved method of cooling an organ. 
     SUMMARY OF THE INVENTION 
     In one method of cooling an organ a portion of a body fluid bathing the organ is withdrawn. A cool fluid is infused during the withdrawing. 
     In yet another method of cooling an organ a volume of up to about 5% of a body fluid bathing the organ is withdrawn. A cool fluid is infused. 
     Another embodiment of a catheter is provided with an inlet port to withdraw a portion of a body fluid bathing an organ from a location adjacent the organ. An outlet port is included to infuse a cool fluid to the location as the portion of the body fluid is withdrawn. 
     An embodiment of an organ cooling assembly is provided including a pump assembly and a catheter coupled to the pump assembly. The catheter includes an inlet port and an outlet port. The pump is to withdraw a portion of a body fluid bathing an organ through the inlet port and to infuse a cool fluid through said outlet port. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an embodiment of an organ cooling system of the present invention including embodiments of a catheter and a pump assembly. 
     FIG. 2 is a longitudinal cross-sectional view of the catheter of FIG.  1 . 
     FIG. 3 is a perspective view of an embodiment of a catheter of the present invention. 
     FIG. 4 is a cross-sectional view of the catheter of FIG. 3 taken from section line  4 — 4  of FIG.  3 . 
     FIG. 5 is a cross-sectional view of the catheter of FIG. 3 taken from section line  5 — 5  of FIG.  3 . 
     FIG. 6 is a longitudinal cross-sectional view of the catheter of FIG.  3 . 
     FIG. 7 is a side view of the catheter of FIG. 3 inserted within a patient to contact a fluid bathing an organ. 
     FIG. 8 is a side view of the catheter of FIG. 3 inserted within a patient and contacting separate portions of a fluid bathing an organ. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While embodiments of the present invention are described with reference to certain cooling methods, devices, and mechanisms, embodiments of the invention are applicable to any cooling system where an organ of a body is to be cooled. This would include organ cooling methods, devices, and systems directed toward cooling organs such as the brain, lungs and heart. The invention is particularly useful when the body organ to be cooled is bathed in a body fluid. 
     Referring to FIG. 1, a catheter  100  and pump assembly  150  are shown. Embodiments of the catheter  100  can be constructed of flexible plastic materials such as polyvinyl chloride, polyethylene, nylon, polytetrafluoroethylene, and other such materials. In the embodiment shown, the catheter  100  is configured to be positioned to contact a body fluid bathing an organ. A body fluid bathing an organ is distinguished from other body fluids, such as blood, which are channeled throughout the body and not generally isolated in a region surrounding a particular organ or organs as in the case of a fluid bathing an organ. 
     The pump assembly  150  includes tubing  120  attached to a main body  130 . The tubing  120  includes a lumen and has an intake portion  125  and an output portion  117 . The tubing  120  forms a loop with the end of the intake portion  125  and the end of the output portion  117  coming together at a juncture. A portion of the tubing  120  passes through a cooling region  140  to cool any fluid contained within the lumen of the tubing  120 . In the embodiment shown, the cooling region  140  includes an ice bath. However, in other embodiments of the invention, other cooling mechanisms may be included in the cooling region  140  to cool fluid within the tubing  120 . For example, in one embodiment of the invention, the cooling region  140  is surrounded by a coil carrying a refrigerant to cool any fluid within the tubing  120  as it is passed through the cooling region  140 . 
     Continuing with reference to FIG. 1, the juncture includes a joining mechanism  151  to which a proximal-most end  152  of a catheter  100  is coupled. The catheter  100  of the embodiment shown includes an outlet port  118  at the end of an output lumen  119  and an inlet port  126  at the end of an intake lumen  127 . As discussed below, the catheter  100  includes cooling capacity as provided by the cooling region  140  of the pump assembly  150 . 
     When the catheter  100  is plugged in, the joining mechanism  151  couples the end of the intake portion  125  to the intake lumen  127 . The joining mechanism  151  also couples the end of the output portion  117  to the output lumen  119  of the catheter  100 . In the embodiment shown, the proximal-most end  152  of the catheter  100  snaps into the joining mechanism  151  to securely position and align the catheter  100  to the tubing  120 . However, in other embodiments of the invention, a luer-loc or other coupling mechanism may be employed to secure and align the catheter  100  and lumens  127 ,  119  to the tubing portions  125 ,  117 . In this manner an uninterrupted lumen path from the inlet port  126 , through the catheter  100 , through the tubing  120 , and to the outlet port  118  is provided when the catheter  100  is plugged into the pump assembly  150 . 
     The embodiment of pump assembly  150  shown includes a roller assembly  103 . The pump assembly  150  is operated by the roller assembly  103  rotating and contacting the tubing  120 . The tubing  120  is held in place by a support roller  105  as the roller assembly  103  contacts the tubing  120 . During rotation of the roller assembly  103 , the portion of the tubing  120  contacted by the roller assembly  103  is intermittently compressed and relaxed between the roller assembly  103  and the support roller  105 . In this manner, any fluid present within the tubing  120 , and therefore, the uninterrupted lumen path discussed above, is circulated. 
     The amount of fluid pumped per rotation of the roller assembly  103  can be determined based on the size of the tubing  120  used, the amount of compression obtained during a rotation of the roller assembly  103 , and the length of contact between the roller assembly  103  and the tubing  120  during a rotation of the roller assembly  503 . Therefore, the roller assembly  103  can be configured and directed with a particular exchange or cooling method in mind (see FIGS.  7  and  8 ). 
     The roller assembly  103  which acts to compress the tubing  120 , discussed above, is driven by a motor drive unit. The motor drive unit rotates the roller assembly  103  based on a control signal received. The control signal is established by an operator of the pump assembly  150 , for example, at a control panel coupled to the pump assembly  150 . The roller assembly  103  will rotate according to a particular fluid exchange or cooling method to be employed as directed by the operator (see FIGS.  7  and  8 ). 
     Referring to FIG. 2, a longitudinal cross-sectional view of the catheter  100  of FIG. 1 is shown. The output lumen  119  is shown throughout the catheter  100  terminating at outlet port  118 . The intake lumen  125  is shown terminating more proximally at inlet port  126 . 
     Referring to FIG. 3, an alternate embodiment of catheter  300  is shown. In the embodiment of FIG. 3, the distal portion  310  of the catheter  300  includes a cooling mechanism. In the embodiment shown, the cooling mechanism includes cooling elements  312 . In one embodiment of the invention, discussed further herein, the cooling elements  312  are thermoelectric cooling chips which, when activated, absorb heat from a surrounding environment to cool the surrounding environment. An insulated lead  313  is coupled to the catheter  300  at the proximal portion  320  to electronically couple a power source to the cooling elements  312  as also discussed further herein. 
     The distal portion  310  of the catheter  300  embodiment shown also includes an outlet port  317  from which a cool fluid can be dispensed. The proximal portion  320  of the catheter  300  includes an inlet port  325  through which a fluid can be drawn into the catheter. In one embodiment of the invention, also discussed further herein, where the catheter  300  is to be inserted within a spinal canal  700  (see FIG.  7 ), the inlet port  325  is positioned from about 5 cm to about 25 cm from the outlet port  317 , preferably from about 10 cm to about 20 cm. 
     Referring to FIGS. 3-5, cross sectional views, taken from section lines  4 — 4  and  5 — 5 , of the catheter  100  of FIG. 1 are shown. FIG. 4 reveals an intake lumen  425  not present in FIG.  5 . This is because the intake lumen  425  does not run through the distal portion  310  of the catheter  300 . The inlet port  325  leads to the intake lumen  425  which runs proximally from the inlet port  325  to a proximal-most end of the catheter  300 . FIG. 4 also reveals an output lumen  417 . The outlet port  317 , shown in FIG. 3, leads to the output lumen  417  which runs proximally from the outlet port  317  to a proximal-most end of the catheter  300 . 
     Continuing with reference to FIGS. 3-5, the catheter  300  also includes a cooling lumen  412 . The cooling lumen  412  runs interior of the catheter  300  from the insulated lead  313  to a position within the distal portion  310  of the catheter  300 . In the embodiment shown, the cooling lumen  412  carries electrical wire from the insulated lead  313  to the cooling elements  312 . In other embodiments of the invention, where other cooling mechanisms are employed, the cooling lumen  412  carries other supportive cooling features. 
     Referring to FIG. 5, the cooling lumen  412  of the embodiment shown is electrically coupled to each cooling element  312  of the distal portion  310  of the catheter  300  (see FIG. 3) through a via  512 . In this manner, electrical wire can be carried directly to each cooling element  312 . 
     Continuing with reference to FIG. 5, each cooling element  312  achieves temperature differential by the Peltier effect. That is, each cooling element  312  has a semiconductor layer  520  disposed between a heat absorbing layer  515  and a heat dissipating layer  525 . The heat absorbing layer  515  includes a heat absorbing electrode and insulating substrate. The heat dissipating layer  525  includes a heat dissipating electrode and insulating substrate. As a current from a power source reaches each cooling element  312  the heat absorbing layer  515  begins to absorb heat which is dissipated interior of the catheter  300  from the heat dissipating layer  525 . To further dissipation, heat sinks from the heat dissipating layer  525  and into the catheter interior  530  can be provided. A cooling element  312  as described can be placed in contact with a body fluid and activated to cool the body fluid (see FIGS.  7  and  8 ). The heat absorbing layer  515  of the cooling element is of a biocompatible material or covered by a biocompatible material for contacting a body fluid. 
     Referring to FIG. 6, a longitudinal cross-sectional view of the catheter  300  of FIG. 3 is shown. The cooling elements  312  are shown disposed in the distal portion  310  of the catheter  300 . The output lumen  417  is shown through both the proximal  320  and distal  310  portions of the catheter  300 , and terminating at the outlet port  317 . The intake lumen  325  is shown running to within the proximal portion  320  of the catheter  300  and terminating at the inlet port  325 . The catheter  300  may be coupled to a pump assembly  150  (as shown in FIG. 1) to pump fluids through the intake lumen  425  or output lumen  417  as a body organ is cooled (see FIGS.  7  and  8 ). 
     Referring to FIG. 7, a method of the invention is described where the catheter  300  of FIG. 3 is inserted into a body of a patient to an area containing a body fluid bathing an organ. In the embodiment shown, the catheter  300  is inserted into the spinal canal  700  of the patient where cerebrospinal fluid (CSF) is found. The catheter  300  is inserted at this location to treat the brain of the patient. The catheter  300  has an outer diameter of between about 0.7 mm and about 1.3 mm, preferably between about 0.9 mm and about 1.1 mm. 
     The CSF bathes the brain of the patient. CSF, as with other fluids bathing organs, is not circulated throughout the body of the patient. Rather, the CSF is found only in the spinal canal and surrounding the brain of the patient. Therefore, as described below, cooling of the CSF can act to cool the brain of the patient without losing the cooling effect, via circulation, to the rest of the body. Additionally, only about 70 cc to about 120 cc of CSF is present within the patient. Therefore, a lower total volume of fluid (e.g. CSF) can be cooled to induce hypothermia of the brain. 
     Continuing with reference to FIG. 7, a spinal needle  750  is shown inserted between vertebrae  710  of the lumbar region  730  of a patient to provide access to the patient&#39;s spinal canal  700 . In other embodiments of the invention, the spinal needle  750  is inserted between vertebrae  710  in other regions of the spine. The catheter  300  is inserted through the spinal needle  750  and into the spinal canal  700 . In one embodiment of the invention, the cooling elements  312  of the distal portion  310  of the catheter  300  are activated to begin cooling CSF within the spinal canal  700  immediately upon contacting the CSF. The catheter  300  is advanced within the spinal canal  700  toward the cervical region  830  (see FIG. 8) of the spinal canal  700 . In one embodiment of the invention, the catheter  300  is advanced over a pre-positioned guidewire in the spinal canal  700 . However, a guidewire is not required for the catheter  300  to reach the spinal canal  700  or for advancement to the cervical region  830 . 
     In the embodiment shown the catheter  300  is coupled to the pump assembly  150  of FIG.  1 . Thus, as described further herein, cooling of CSF occurs directly through contact with the cooling elements  312  and once pumped through the cooling region  140  of the pump assembly  150  shown in FIG.  1 . However, in other embodiments of the invention, the cooling elements  312  or the cooling region  140  alone can be used to cool the CSF. 
     Referring to FIG. 8, the catheter  300  has been advanced as far distally as possible to within the cervical region  830  of the spinal canal  700 , adjacent the brain of the patient. CSF within the cervical region  830  filters through the spinal canal  700  to bathe the brain of the patient. The inlet port  325  of the catheter  300  remains within the lumbar region  730  of the spinal canal  700  whereas the outlet port  317  of the catheter  300  is found within the cervical region  830  of the spinal canal  700 . The cooling elements  312  as shown are cooling CSF within the cervical region  830  of the spinal canal. 
     Continuing with reference to the embodiment of FIG. 8, the pump assembly  150  (shown in FIG.  1 ), to which the catheter  300  is attached, is activated to draw in warm CSF  840  through the inlet port  325  and expel cool CSF  850  through the outlet port  317 . The amount of CSF drawn in is substantially equivalent to the amount expelled. In one embodiment of the invention, only up to about 5% of the total volume of CSF is exchanged per pump compression in this manner, preferably between about 2% and about 3%. Such an exchange helps ensure a stable pressure within the spinal canal  700  during induction of hypothermia. To further ensure efficient cooling and stable pressure, in one embodiment of the invention, the pump  150  and roller  103  assemblies (shown in FIG. 1) are configured to pump between about 1.5 cc and about 3.5 cc per compression, preferably between about 2.0 and about 3.0 cc. Additionally, in another embodiment of the invention, the assemblies  150 ,  103  are configured to pump from about 130 cc to about 230 cc per minute, preferably between about 170 cc and about 190 cc. 
     In one embodiment of the invention, the catheter  300 , and tubing  120  are initially filled with cool saline. The cool saline is expelled prior to cool CSF  850  to prevent pressure changes or the influx of air or gas to within the spinal canal  700  when CSF has yet to circulate through the system to reach the outlet port  317 . 
     Warm CSF  840  is taken to the pump assembly  150  where it is initially cooled by the cooling region  120  (shown in FIG.  1 ). The CSF is then cool CSF  850  which travels through the tubing  120  (shown in FIG. 1) and back through the catheter  300  where it exits at the outlet port  317 . The cooling elements  312  continue to cool the cool CSF  850  once it is emptied into the cervical region  830  of the spinal canal  700  from the output port  317 . 
     In the embodiment shown, warm CSF  840  is that portion of CSF which is still to be cooled as discussed above. By distancing the inlet port  325  away from the outlet port  317  and within the lumbar region  730 , hypothermia can be focused on the cervical region  830  from where CSF is to be filtered to bathe the brain of the patient to induce hypothermia of the brain. However, positioning of the ports  317 ,  325  in this manner is not required in order to cool the CSF to induce hypothermia of the brain. In another embodiment of the invention, the patient is placed in the Trendelenburg position, with the lower limbs elevated to a position higher than the heart, during cooling of the CSF to aid in the transfer of cool CSF  850  from the spinal canal  700  to surround the brain. 
     As described above, hypothermia is induced in the brain by cooling CSF in which the brain is bathed. The CSF within the spinal canal  700  continually diffuses beyond the cervical region  830  to directly contact the brain. In fact, a complete transfer of the total volume of CSF within the spinal canal  700  is exchanged with CSF directly bathing the brain several times each day. Therefore, cooling of the CSF within the spinal canal  700  can be used to begin the process of hypothermia induction in an immediate manner. 
     In embodiments of the invention described above, CSF within the spinal canal  700  is cooled in order to induce hypothermia of the brain. Cooling CSF in this manner requires only the simple placement of a spinal needle  750  and insertion of the catheter  300  there through in order for cooling to begin. Access to the CSF is readily available in the spinal canal  700 . Placement of a spinal needle  750  does not require fluoroscopic control and the patient does not need to be brought to an X-ray suite. Therefore, embodiments of the invention can be quickly applied to save brain tissue prior to moving forward with additional treatment and/or diagnosis. 
     Employing embodiments of the invention allows time to be saved, hypothermia to be induced, and brain cells to be saved when a patient presents with a head trauma. Additionally, the organ hypothermia induces is focused on the brain and the cooling effect is not redistributed throughout the body. Therefore, the efficiency of the cooling is increased and the amount of brain tissue saved is optimized. 
     In other embodiments of the invention, other organs are cooled by cooling fluids, or portions of fluids, in more direct contact with the organs to be cooled. For example, in one embodiment of the invention, a catheter is inserted to within the pericardium, containing pericardial fluid, to treat a patient&#39;s heart. In this embodiment, pericardial fluid in direct contact with the heart is cooled to induce hypothermia in the heart. In another embodiment of the invention, a catheter is inserted to within the pleura, containing pleural fluid, to treat a lung of a patient. Again, in this embodiment, pleural fluid in direct contact with the lung is cooled to induce hypothermia in the lung. 
     Embodiments of the invention include an improved method for cooling an organ. Although exemplary embodiments of the invention describe particular hypothermia treatments with respect to the brain of a patient, additional embodiments of the invention are possible. For example, in other embodiments of the invention a catheter is advanced to areas containing other body fluids to treat other organs of the patient. Additionally, many changes, modifications, and substitutions may be made without departing from the spirit and scope of this invention.