# Patent

## Title
Method and apparatus for spinal cooling

## Abstract

A method for exchanging heat with a patient's spinal column incident to spinal surgery or to relieve a patient for a hypoxia condition of the spine. A closed loop heat exchange catheter is percutaneously advanced into the retroperitoneal space of the patient, and then heat exchange fluid is circulated through the catheter to cool the spinal column.

## Background
FIELD OF THE INVENTION
The present invention relates generally to methods and apparatus for exchanging heat with the spine of a patient.
BACKGROUND OF THE INVENTION
It has been discovered that the medical outcome for a patient suffering from various maladies, e.g., 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 spinal surgery or to counter the effects of spinal injury, the present invention recognizes that cooling the spine can be advantageous.
The following U.S. patents, all of which are incorporated herein by reference, disclose various intravascular catheters/systems/methods which, as understood herein, can be used in the novel non-intravascular approach described herein: U.S. Pat. Nos. 6,749,625, 6,419,643, 6,416,533, 6,409,747, 6,405,080, 6,393,320, 6,368,304, 6,338,727, 6,299,599, 6,290,717, 6,287,326, 6,165,207, 6,149,670, 6,146,411, 6,126,684, 6,306,161, 6,264,679, 6,231,594, 6,149,676, 6,149,673, 6,110,168, 5,989,238, 5,879,329, 5,837,003, 6,383,210, 6,379,378, 6,364,899, 6,325,818, 6,312,452, 6,261,312, 6,254,626, 6,251,130, 6,251,129, 6,245,095, 6,238,428, 6,235,048, 6,231,595, 6,224,624, 6,149,677, 6,096,068, 6,042,559, and U.S. patent application Ser. No. 10/355,776.
SUMMARY OF THE INVENTION
A method for treating a patient includes instructing a medical caregiver to advance a closed loop heat exchange catheter into the retroperitoneal space of the patient, and to circulate heat exchange fluid through the catheter. The instructions may be given by, e.g., a medical device manufacturer as part of regulatory labeling.
The catheter may be advanced percutaneously into the patient, and in preferred implementations the heat exchange fluid is colder than the patient. The catheter is closed loop in that heat exchange fluid does not exit the catheter into the patient.
Preferably, a heat exchange element of the catheter is positioned against the spinal column. The heat exchange element can be spiral shaped, it can be plastic or metal, and/or it can be a balloon.
In another aspect, a method for cooling at least a portion of a spinal column of a patient disposed in an operating room includes advancing a closed loop heat exchange catheter into the retroperitoneal space of the patient, and circulating heat exchange fluid through the catheter to cool the spinal column. Spinal surgery is then conducted on the patient.
In another aspect, a method for treating a patient for a hypoxia condition of the spine includes advancing a closed loop heat exchange catheter into the retroperitoneal space of the patient, and circulating heat exchange fluid through the catheter to cool the spinal column and thereby relieve the patient of at least some deleterious effects of spinal hypoxia. The hypoxia condition may be caused by cardiac arrest, myocardial infarction, stroke, or trauma.
The details of the present invention, both as to its construction and operation, can best be understood in reference to the accompanying drawings, in which like numerals refer to like parts, and which:



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an exemplary patient cooling system; and
FIG. 2 is a cross-section of a patient, showing the retroperitoneal space and the catheter placed therein.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring initially to FIG. 1, a patient heat exchange system is shown and generally designated 10. The system 10 includes an indwelling heat exchange catheter 12 that can be inserted into a patient to heat or cool the patient. The catheter 12 may be any of the catheters disclosed in the above-referenced patents or other appropriate closed loop heat exchange catheters.
Coolant such as but not limited to saline is circulated through the catheter 12 in a closed loop to and from a member such as a heat exchange system 14 through coolant supply and return tubes 16, 18 under the influence of a pump 20 (such as but not limited to a gear pump, roller pump, diaphragm pump, or other type of pump) to heat or cool the coolant as desired to warm or cool a patient. The catheter 12 is made of biocompatible material that may be coated with an anti-coagulant substance such as Heperin®. Preferably, the catheter 12 is made of flexible plastic, and on its distal end it may include one or more heat exchange elements 13 such as balloons or fibers (including intertwined spiral balloons) or metallic structures.
In the particular non-limiting embodiment shown in FIG. 1, the cooling system 14 includes a working fluid bath container 22 in which a working fluid bath 24 such as saline, glycol, a mixture thereof, or other appropriate working fluid is disposed. The container 22 may define a cooling receptacle 26 that can receive a tubing set 28 through which coolant flows as part of the closed coolant path. The tubing set 28 may be implemented as a single length of IV tubing or, as indicated in FIG. 1, the tubing set 28 may include a serpentine-like coolant path in a bag-like cartridge assembly that can be easily engaged and disengaged with the receptacle 26. In any case, it will be appreciated that the working fluid in the bath 24 is in thermal contact with the cooling receptacle 26 and, hence, with the coolant in the tubing set 28 to cool the patient coolant flowing through the path when the patient coolant is warmer than the working fluid.
The cooling system 14 also includes a heat sink 30 that is in thermal contact with the working fluid in the bath 24. The working fluid may be circulated between the heat sink 30 and the bath 24. The heat sink 30 may be a combined heater/chiller system that can include a refrigerant compressor and/or a thermo-electric cooler (TEC) to cool working fluid. Details of various types of non-limiting heat sinks are set forth in selected of the above-referenced U.S. patents. In any case, a thermal interface 31 can be provided in some implementations to permit heat transfer between the heat sink 30 and working fluid in accordance with disclosure below, without permitting electrically connectivity therebetween.
FIG. 1 shows that a controller 32 receives a patient temperature signal from a temperature sensor 34. In accordance with present principles, the controller 32 accesses a logic module 36 to control the heat sink 30 and pump 20 in accordance with logic set forth further below. The controller 32 may be implemented by any suitable processor. The temperature sensor 34 may be any suitable temperature sensor such as a thermocouple, resistance temperature detector (RTD), tympanic IR sensor, or other sensor that outputs a signal representative of patient temperature, preferably patient spinal temperature. The sensor 34 may be placed in the bloodstream of the patient, or in the esophagus, rectum, bladder, or near the ear canal to sense tympanic temperature, or in the retroperitoneal cavity. The logic module 36 may be implemented in electronic storage such as disk or solid state memory and accessed by a processor to execute the present logic.
Now referring to FIG. 2, a patient 40 has a digestive tract 42 and a spinal column 44 anterior thereto, with a retroperitoneal space 46 formed adjacent the spinal column 44. To cool the spine for, e.g., spinal surgery, or to protect it during hypoxic events such as but not limited to those caused by cardiac arrest, myocardial infarction, stroke, and trauma that causes spinal hypoxia, the catheter 12 is advanced percutaneously into the retroperitoneal space 46 as shown, preferably with the heat exchange element 13 placed near or against the spinal column 44. A sheath may be used for placement. In any case, the catheter 12 does not reside in the vasculature of the patient. Coolant is then circulated through the catheter 12 and coolant temperature is controlled by the controller 32 in response to feedback from the sensor 34 to establish a desired patient temperature, e.g., to establish a physician-defined spinal temperature or core body temperature. While the particular METHOD AND APPARATUS FOR SPINAL COOLING 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.

## Claims

1. A method for cooling at least a portion of a spinal column of a patient disposed in an operating room, comprising:
advancing a closed loop heat exchange catheter into the retroperitoneal space of the patient;
circulating heat exchange fluid through the catheter to cool the retroperitoneal space and thereby cool the spinal column; and
conducting spinal surgery on the patient.

2. The method of claim 1, wherein the catheter is advanced percutaneously into the patient.

3. The method of claim 1, wherein at least one heat exchange element of the catheter is positioned against the spinal column.