1. Field of Invention
The invention relates to a resuscitation apparatus and method for directing a chilled medical fluid to the brain at a sufficient rate to allow a rapid drop in overall brain temperature. The apparatus and method extend the period of time in which life resuscitation methodologies may be performed on a patient suffering from trauma or decreased blood flow to the brain, without permanent brain damage resulting if recovery is achieved.
2. Description of Related Art
When trauma or decreased blood flow to the brain occurs, the brain is deprived of freshly oxygenated blood. For example, this situation typically occurs during cardiac arrest, respiratory arrest, stroke and other cerebrovascular trauma, suffocation, drowning, strangulation, electrocution, toxic poisoning (carbon monoxide, cyanide, etc.), metabolic insults or other similar trauma. Without a steady supply of freshly oxygenated blood, the brain ceases to function. After resuscitation, most patients will suffer some damage to the brain and associated neurologic tissues.
For example, among cardiac arrest victims overall less than 10% survive neurologically intact and without significant brain damage. The other approximately 90% either die or sustain some neurologic injury from ischemia (i.e., lack of blood flow to the brain) or anoxia (i.e., lack of oxygen to the brain). Such frequency of neurologic injury occurs because after a cardiac arrest, basic cardiopulmonary resuscitation and advanced life support techniques, such as CPR, closed heart cardiac chest massage, and electroshock treatments, typically require fifteen to twenty minutes to regain circulation from a failed heart. Reversible neurologic damage begins as early as four minutes and irreversible neurologic damage begins as early as six minutes after circulation stops. To combat this potential neurologic injury, initial resuscitation efforts need to be directed toward reviving and/or preserving the viability of the brain in addition to resuscitating the heart.
Anoxic and ischemic brain injuries from cardiac arrest result in damage to the brain and associated neurologic tissues after about four minutes. In contrast, the heart can survive intact up to four hours after cardiac arrest. The short viability of brain tissue upon deprivation of oxygenated blood is a result of the requirement of high amounts of nutrients for tissue maintenance. Brain tissue uses for maintenance almost all of the nutrients supplied to it by the circulating blood, and stores only a very small amount of nutrients. Absent blood flow to the brain, the small amount of stored nutrients is rapidly exhausted. Once the stored nutrients are exhausted, brain oxygen content rapidly depletes. This oxygen depletion is traumatic and causes a series of reactions in the oxygen starved brain tissue cells. These reactions are believed to produce free radical ions, primarily consisting of the superoxide radical O2xe2x88x92. These free radicals complex with proteins in the brain and associated neurologic tissues, altering respiration, energy transfer and other vital cellular functions, and irreversibly damaging these tissues.
Efforts should be directed toward extending the period of time the brain can function without oxygen while the patient remains neurologically intact.
The medical literature is replete with examples of humans surviving extended periods of time (greater than 5 minutes) without oxygen being delivered to the brain. For example, children revived after hours of submersion in very cold water have fully recovered with little if any neurologic damage.
Hypothermic therapy is one method of keeping the brain alive absent oxygen. It involves cooling the brain to a temperature where its metabolic activity is decreased. When the brain""s metabolic activity is decreased, it uses much less oxygen and more slowly exhausts stored nutrients, while production of irreversibly damaging O2xe2x88x92 free radicals is slowed and almost completely ceased. Thus, upon resuscitating the body from trauma, the patient emerges neurologically intact. The literature has demonstrated that a drop of 3-4 degrees Celsius can be sufficient to protect the brain from irreversible damage in a hypoxic state for at least 10-20 minutes.
Various apparatus and/or methods have previously been disclosed for directing a chilled medical fluid to the brain to prevent anoxic and/or ischemic injury during trauma.
In the article, xe2x80x9cPreservation of Cerebral Function During Circulatory Arrest and Resuscitation: Hypothermic Protective Considerationsxe2x80x9d, Robert M. White teaches delivering chilled fluids to the brain via the carotid arteries. According to the White method, the carotid arteries are punctured with Rochester no. 15 needles connected via plastic tubing to intravenous bottles containing cooled perfusate. The fluids are delivered at an average pressure of 75 mm mercury by an attached standard sphygmomanometer bulb. The fluids taught include saline, dextran and oxygenated blood.
Russian Patent No. 760,972 to Raduschkevi et al. discloses apparatus for cooling the brain during a sudden stoppage of the heart or an ineffective functioning of the heart. The apparatus includes a refrigeration unit that includes a heat-insulated chamber for cooling a blood-mixed fluid; a heat exchanger; a filter/trap; a perfusion pump; cannulae for connecting to blood vessels; and means for control and regulation of temperature and fluid transport. Blood from an artery can also be withdrawn through a tube, circulated through the apparatus, passing through the perfusion pump, the heat exchanger and the filter trap, and returned to the artery via a tube.
In U.S. Pat. No. 4,451,251, Osterholm discloses an apparatus and method for circulating a nutrient emulsion through the cerebrospinal fluid pathway system to satisfy cerebral metabolic needs where the vascular system has been obstructed. Osterholm teaches injecting the nutrient emulsion via cerebral catheter means directly into a cerebral ventricle. Osterholm further teaches that hypothermic temperatures may be selected for the nutrient emulsion in order to establish certain treatment conditions if so desired. The apparatus includes a nutrient emulsion reservoir, a heat exchanger, an oxygenator, a filtration device and the cerebral catheter means.
In U.S. Pat. Nos. 5,149,321, 5,234,405 and 5,395,314 and co-pending U.S. patent application Ser. No. 08/484,601 now U.S. Pat. No. 5,827,222, Ronald M. Klatz and Robert M. Goldman disclose a brain resuscitation device and corresponding method. The device includes a solution reservoir, an oxygenator, a heat exchanger, a fluid pathway and a catheter. The catheter may be a balloon catheter. The solution may include barbiturates, free radical scavengers and/or oxygen carrying agents. Further, the device may be portable.
However, none of these references provide heat exchange apparatus that provides intense cooling to quickly chill a medical fluid a sufficient amount to slow a metabolic rate of a brain of a mammal into which the medical fluid is introduced. Further, none of them provides a convenient portable apparatus. Furthermore, none discloses docking apparatus that allows the portable apparatus to be removably attached to a heat exchange apparatus in order to maintain a medical fluid chilled an amount sufficient to slow a metabolic rate of a brain of a mammal into which the medical fluid is introduced until the portable apparatus is needed. Additionally, none discloses a control unit that controls the introduction of medical fluid into the system to prime the system prior to introducing the medical fluid into a mammal.
The apparatus and method according to the invention extend the period of time in which life resuscitation methodologies may be performed on a patient suffering from trauma or decreased blood flow to the brain, without permanent brain damage resulting if recovery is achieved. Because emergency personnel often must treat patients suffering from trauma or decreased blood flow to the brain without the conveniences of a hospital, sometimes an apparatus is needed that can be carried with emergency personnel to the patient and be ready upon demand.
The apparatus and method according to the invention can utilize heat exchange apparatus that provide intense cooling to quickly chill a medical fluid a sufficient amount to slow a metabolic rate of a brain or other organ of a mammal into which the medical fluid is introduced, or alternatively, the resuscitation apparatus can be provided with docking apparatus that allows the portable apparatus to be removably attached to a heat exchange apparatus in order to maintain the medical fluid chilled an amount sufficient to slow a metabolic rate of an organ of a mammal into which the medical fluid is introduced until the portable apparatus is needed. Accordingly, the apparatus can provide the necessary cooling on demand, and, if optionally configured to be portable, can be carried to the patient. The apparatus is particularly applied to slow the metabolic rate of the brain but can be used to slow the metabolic rate of other organs depending on the location of entry in the cardiovascular system.
Further, medical fluids are expensive, and, away from the conveniences of a hospital, may be in short supply. The apparatus and method according to the invention can withdraw medical fluid from a mammal, degas, oxygenate and/or chill the medical fluid before reintroducing the medical fluid into the mammal. Accordingly, less medical fluid is needed.
Additionally, the apparatus and method can utilize a control unit to prime the system prior to introducing medical fluid into a patient. This allows medical personnel to focus more of their attention on life resuscitation methodologies which they are performing to revive the patient.