Drug – bio-affecting and body treating compositions – Inorganic active ingredient containing – Elemental fluorine or fluorine compound
Reexamination Certificate
1999-06-22
2001-10-16
Pak, John (Department: 1616)
Drug, bio-affecting and body treating compositions
Inorganic active ingredient containing
Elemental fluorine or fluorine compound
C424S600000, C424S703000, C514S816000, C514S953000, C514S958000, C514S959000, C252S372000, C128S203160, C128S203260, C128S204150, C128S204170, C128S898000, C604S023000, C604S500000, C604S503000, C604S514000
Reexamination Certificate
active
06303156
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to noninvasive methods for rapidly changing the body temperature of a patient. This is accomplished by having the patient hyperventilate a gaseous mixture containing sulfur hexafluoride and oxygen. The invention also includes the compositions used in these methods.
BACKGROUND OF THE INVENTION
Patients undergoing operations that require low blood flow or circulatory arrest often must have their body temperature lowered prior to surgery in order to help protect the heart and brain. In particular, hypothermia has been induced in patients undergoing cardiac surgery and operations for cerebral aneurysms. More recently, the lowering of body temperature has been used as a technique for protecting the brain in head trauma patients and there are indications that this procedure may be useful in treating patients for hemorrhagic shock. Unfortunately, there is, at present, no reliable noninvasive method for rapidly lowering a patient's body temperature. The present invention addresses this problem and discloses a method that can be used for rapidly inducing hypothermia or, alternatively, for rapidly warming a hypothermic patient.
SUMMARY OF THE INVENTION
The present invention is based upon the concept that respiratory heat exchange can be used to rapidly change a patient's body temperature. The method requires nothing more than standard hospital equipment such as a ventilator and a means for heating or cooling gases prior to administration to a patient.
In its first aspect, the invention is directed to a method for reducing the body temperature of a patient by administering a gas mixture comprising a combination of sulfur hexafluoride and oxygen. In order to increase the rate of heat exchange, the gas mixture is administered while the patient hyperventilates, either spontaneously or as the result of mechanical ventilation. The mixture being administered must be below the body temperature of the patient and administration is continued until the patient's temperature is reduced to the desired level. Typically, the sulfur hexafluoride will be present at a concentration of between 20 and 80%, with about an 80/20 ratio of sulfur hexafluoride to oxygen being preferred. Unless otherwise indicated, percentages referred to herein indicate a mole percentage. It is also generally preferred that the pressure of carbon dioxide in the patient's arterial blood be maintained within the normal range during gas administration. A reduction in body temperature may be facilitated by maintaining the water vapor content of the gas mixture at low levels, preferably below 10%.
The method discussed above can, alternatively, be used for increasing the body temperature of a patient. The same mixture of sulfur hexafluoride and oxygen is administered but, rather than being cooled prior to administration, it is heated to a temperature above that of the patient. Again, administration of the mixture is maintained until the desired body temperature of the patient is achieved. As with the procedure described above, sodium hexafluoride should be maintained at a concentration of between 20 and 80%, with an 80/20 ratio of sodium hexafluoride to oxygen being preferred. A patient's arterial blood carbon dioxide pressure may be maintained within the normal range during this procedure. In order to further promote an increase in body temperature, the water vapor content of the gas mixture administered to a patient may be maintained at levels of greater than 20 or 40%.
The invention also encompasses the compositions for rapidly changing a patient's body temperature used in the methods described above. Thus, the invention includes mixtures of sulfur hexafluoride and oxygen, typically with the sulfur hexafluoride present at a concentration of 20-80%. Preferably, the composition should have about 80% sulfur hexafluoride. The most desirable concentration of water vapor will depend upon the intended use of the composition. In cases where the composition will be used for lowering the body temperature of a patient, water vapor should, preferably, be present at a concentration of less than 10%. Compositions that will be used to warm a patient should have a concentration of water vapor of greater than 20% and, more preferably, of greater than 40%.
REFERENCES:
patent: 861672 (1998-09-01), None
Ingenito, et al., “Dissociation of Temperature-Gradient and Evaporative Heat Loss during Cold Gas Hyperventilation in Cold-Induced Asthma,”Am. Rev. Respir. Dis.138:540-546 (1988).
International Search Report for PCT/US99/13878 (1999).
Beran, et al., “Hypothermia and Rewarming Induced by Surface and He-O2Inhalate Temperature Control,”J. App. Physiol.39:337-340 (1975).
Pak John
Pillsbury & Winthrop LLP
Sanzo Michael A.
The Brigham and Women's Hospital Inc.
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