Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2001-07-13
2004-01-20
Gibson, Roy D. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S096000
Reexamination Certificate
active
06679906
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to medical devices and a method of using them for selectively affecting the temperature of a patient's body, or a portion of the patient's body, and more particularly, to a temperature control catheter system including an on-board temperature probe and a method of use thereof.
2. Description of the Prior Art
Under ordinary circumstances, the thermoregulatory system of the human body maintains a near constant temperature of about 37° C. (98.6° F.), a temperature generally referred to as normothermia. For various reasons, however, a person may develop a body temperature that is below normothermia, a condition known as hypothermia, or a temperature that is above normothermia, a condition known as hyperthermia. Accidental hypothermia and hyperthermia are generally harmful, and if severe, the patient is generally treated to reverse the condition and return the patient to normothermia. Accidental hypothermia significant enough to require treatment may occur in patients exposed to overwhelming cold stress in the environment or whose thermoregulatory ability has been lessened due to injury, illness or anesthesia. For example, this type of hypothermia sometimes occurs in patients suffering from trauma or as a complication in patients undergoing surgery.
However, in certain other situations hyperthermia and particularly hypothermia may be desirable and may even be intentionally induced. For example, hypothermia is generally recognized as being neuroprotective, and may, therefore, be induced in conjunction with cardiac surgery where there is an interruption or decrease of cardiac output of oxygenated blood, treatments for ischemic or hemorrhagic stroke, blood deprivation caused by cardiac arrest, intracerebral or intracranial hemorrhage, head and spinal trauma, brain or spinal surgery, or any other situation where there is danger to neural tissue because of ischemia, increased intracranial pressure, edema or other similar processes.
Other examples where hypothermia may be neuroprotective include periods of cardiac arrest in myocardial infarction and heart surgery, neurosurgical procedures such as aneurysm repair surgeries, endovascular aneurysm repair procedures, spinal surgeries, procedures where the patient is at risk for brain, cardiac or spinal ischemia such as beating heart by-pass surgery or any surgery where the blood supply to the heart, brain or spinal cord may be temporarily interrupted.
Hypothermia has also been found to be protective of cardiac muscle tissue when that muscle tissue is at risk, for example during or after a myocardial infarct (MI), or during cardiac surgery, cardiac arrest, or other situations where there is deprivation of the normal blood supply to the cardiac tissue. Indeed the tissue protective nature of hypothermia in general is recognized in a vast array of situations.
Simple surface methods for cooling such as cooling blankets, immersion in cold water or ice baths, or alcohol rubs are generally ineffective for inducing hypothermia. The body's normal thermoregulatory responses such as vasoconstriction of capillary beds at the surface of the body and arterio-venous shunting of blood away from the skin act to render such cooling methods ineffective. Further, if the body temperature drops sufficiently below normothermia, usually at about 35.5° C., the body begins to shiver as a thermoregulatory response to generate additional metabolic heat and fight the induction of hypothermia. This may increase the generation of metabolic heat by 200-500% and generally makes induction of hypothermia in an awake patient impossible by surface cooling alone. Further, the shivering itself is so uncomfortable and exhausting for the patient that this is altogether unacceptable for an awake patient. Only if the patient is paralyzed, which necessitates the patient be intubated for breathing and be placed under general anesthesia can the patient be subjected to significant surface cooling. Even under these conditions, surface cooling which necessitates cooling through the skin and surface fat layers and the use of generally low power surface cooling devices, is too slow and inefficient to be an acceptable means of inducing therapeutic hypothermia.
Furthermore, if control of the patient's temperature is desired so as to attain and maintain a target temperature (sometimes but not always normothermia), or to reverse hypothermia and re-warm the patient at a predetermined rate, surface cooling and warming far too slow and inefficient to give the required level of prompt and precise change in the patient's core temperature to allow these methods to control the patient's thermal condition.
A patient's temperature may be controlled by a very invasive method of adding heat to or removing heat from a patient's blood, particularly in the case of heart surgery. Blood is removed from a patient, circulated through a heart-lung by-pass system, and reintroduced into the patient's body. The equipment generally has a temperature control unit that heats or cools the blood as it is circulated out of the patient before it is reintroduced into the patient. Because a large volume of blood is circulated through the machine in a short time, this by-pass method may be both fast and effective in changing the patient's core temperature and in controlling that temperature, but has the disadvantages of requiring a very invasive medical procedure which requires the use of complex equipment, a team of highly skilled operators, is generally only available in a surgical setting where the patient has undergone a thoracotomy (had its chest split and opened), and involves mechanical pumping of a huge quantity of the patient's blood and channeling that blood through various external lines and conduits, all of which is generally very destructive of the blood tissue resulting in the cytotoxic and thrombolytic problems. In fact, most surgeons using such by pass machinery tend to avoid its use for longer than four hours, much less if at all possible, which is an inadequate period of time for treatment of some conditions such as stroke.
One method for adding or removing heat from a patient by adding or removing heat from the patient's blood that does not involve pumping the blood with an external, mechanical pump is by placing a heat exchange catheter in the bloodstream of a patient and exchanging heat through the catheter. This endovascular temperature management (ETM) technique was described in U.S. Pat. No. 5,486,208 to Ginsburg, the complete disclosure of which is incorporated herein by reference. The Ginsburg patent discloses a method of controlling the temperature of a body by adding or removing heat to the blood by inserting a heat exchange catheter having a heat exchange region into the vascular system and exchanging heat between the heat exchange region and the blood to affect the temperature of a patient. One method disclosed for doing so includes inserting a catheter having a heat exchange region comprising a balloon into the vasculature of a patient and circulating warm or cold heat exchange fluid through the balloon while the balloon is in contact with the blood.
In successful ETM, in addition to fast and precise changes in a patient's body temperature, fast and precise control over a patient's thermal condition is very important whether the patient is being cooled, warmed, or maintained at a constant temperature. A general apparatus and method of ETM control based on temperature management responsive to feedback from temperature probes in or on the patient is disclosed in U.S. Pat. No. 6,149,673 to Ginsburg, the complete disclosure of which is incorporated herein by reference. A similar method is described in PCT publication WO 01/10494 to Radiant Medical Inc., the complete disclosure of which is also incorporated herein by reference. In such methods, a signal representing the temperature of a target tissue, which as mentioned may be the core body
Callister Jeff P.
Hammack Amy L.
Roth Alex T.
Stull Paul M.
Tremulis William S.
Buyan Robert D.
Gibson Roy D.
Johnson Henry M.
Radiant Medical Inc.
Stout, Uxa, Buyan and Mullins, LLP
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