FEVER REGULATION METHOD AND
CROSS REFERENCE TO RELATED
This is a continuation-in-part patent application of U.S. Provisional Patent Application Serial No. 60/246,620, filed Nov. 7, 2000, entitled "Fever Regulation Method and Apparatus" and of U.S. patent application Ser. No. 09/566,531, filed May 8, 2000, entitled "Method of Making Selective 10 Organ Cooling Catheter", which is a continuation of U.S. patent application Ser. No. 09/103,342, filed on Jun. 23, 1998, entitled "Selective Organ Cooling Catheter and Method of Using the Same", now issued U.S. Pat. No.
6,096,068. This is also a continuation-in-part patent application of U.S. patent application Ser. No. 09/586,000, filed Jun. 2, 2000, entitled "Method for Determining the Effective Thermal Mass of a Body or Organ Using a Cooling Catheter"; the entirety of all of the above applications being incorporated by reference herein. 20
STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable 25
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the lowering and control of the temperature of the human body. More 30 particularly, the invention relates to a method and intravascular apparatus for cooling the whole body, especially during periods of fever.
2. Background Information
Organs in the human body, such as the brain, kidney and heart, are maintained at a constant temperature of approximately 37° C. Hypothermia can be clinically defined as a core body temperature of 35° C. or less. Hypothermia is sometimes characterized further according to its severity. A 4Q body core temperature in the range of 33° C. to 35° C. is described as mild hypothermia. A body temperature of 28° C. to 32° C. is described as moderate hypothermia. A body core temperature in the range of 24° C. to 28° C. is described as severe hypothermia. 45
Hypothermia is uniquely effective in reducing brain injury caused by a variety of neurological insults and may eventually play an important role in emergency brain resuscitation. Experimental evidence has demonstrated that cerebral cooling improves outcome after global ischemia, focal 50 ischemia, or traumatic brain injury. For this reason, hypothermia may be induced in order to reduce the effect of certain bodily injuries to the brain as well as other organs.
Cerebral hypothermia has traditionally been accomplished through whole body cooling to create a condition of 55 total body hypothermia in the range of 20° C. to 30° C. The currently-employed techniques and devices used to cause total body hypothermia lead to various side effects. In addition to the undesirable side effects, present methods of administering total body hypothermia are cumbersome. go
Catheters have been developed which are inserted into the bloodstream of the patient in order to induce total body hypothermia. For example, U.S. Pat. No. 3,425,419 to Dato describes a method and apparatus of lowering and raising the temperature of the human body. Dato induces moderate 65 hypothermia in a patient using a rigid metallic catheter. The catheter has an inner passageway through which a fluid, such
as water, can be circulated. The catheter is inserted through the femoral vein and then through the inferior vena cava as far as the right atrium and the superior vena cava. The Dato catheter has an elongated cylindrical shape and is constructed from stainless steel. By way of example, Dato suggests the use of a catheter approximately 70 cm in length and approximately 6 mm in diameter. Thus, the Dato device cools along the length of a very elongated device. Use of the Dato device is highly cumbersome due to its size and lack of flexibility.
U.S. Pat. No. 5,837,003 to Ginsburg also discloses a method and apparatus for controlling a patient's body temperature. In this technique, a flexible catheter is inserted into the femoral artery or vein or the jugular vein. The catheter may be in the form of a balloon to allow an enhanced surface area for heat transfer. A thermally conductive metal foil may be used as part of a heat-absorbing surface. This device fails to disclose or teach use of any ability to enhance heat transfer. In addition, the disclosed device fails to disclose temperature regulation.
An ailment particular susceptible to treatment by cooling, either selective or whole body, is fever or hyperthermia. There is a growing awareness of the dangers associated with fever. Many patients, especially after surgery and/or in the intensive care unit, suffer from fever. For example, it is estimated that 90% of patients in neurointensive care units suffering from sub-arachnoid hemorrhage have a fever. Further, 60% of patients in neurointensive care units suffering from intra-cranial hemorrhage have a fever. 80% of patients in neurointensive care units suffering from traumatic brain injury have a fever. These patients are typically treated with Tylenol, cooling blankets, or other such methods. These methods are not believed to be very effective; moreover, they are difficult to control.
Therefore, a practical method and apparatus that lowers and controls the temperature of the human body satisfies a long-felt need.
SUMMARY OF THE INVENTION
In one aspect, the apparatus of the present invention can include a heat transfer element that can be used to apply cooling to the blood flowing in a large vein feeding the heart.
The heat transfer element, by way of example only, includes first and second elongated, articulated segments, each segment having a mixing-inducing exterior surface. A flexible joint can connect the first and second elongated segments. An inner lumen may be disposed within the first and second elongated segments and is capable of transporting a pressurized working fluid to a distal end of the first elongated segment. In addition, the first and second elongated segments may have a mixing-inducing interior surface for inducing mixing within the pressurized working fluid. The mixing-inducing exterior surface may be adapted to induce mixing within a blood flow when placed within an artery or vein. In one embodiment, the flexible joint includes a bellows section that also allows for axial compression of the heat transfer element as well as for enhanced flexibility. In alternative embodiments, the bellows section may be replaced with flexible tubing such as small cylindrical polymer connecting tubes.
In one embodiment, the mixing-inducing exterior surfaces of the heat transfer element include one or more helical grooves and ridges. Adjacent segments of the heat transfer element can be oppositely spiraled to increase mixing. For instance, the first elongated heat transfer segment may include one or more helical ridges having a counter