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67-489: When blood circulation stops at normal body temperature (37 °C), permanent damage occurs in only a few minutes. More damage occurs after circulation is restored. Reducing body temperature extends the time interval that such stoppage can be survived. At a brain temperature of 14 °C, blood circulation can be safely stopped for 30 to 40 minutes. There is an increased incidence of brain injury at times longer than 40 minutes, but sometimes circulatory arrest for up to 60 minutes

134-409: A cerebral aneurysm is to be performed to help create a bloodless surgical field. After surgery is completed during the period of cold circulatory arrest, these steps are reversed. The brain and heart naturally resume activity as warming proceeds. The first activity of the warming heart is sometimes ventricular fibrillation requiring cardioversion to re-establish a normal beating rhythm. Except for

201-418: A disruption of intracellular organelles and subsequent cellular death. Virtually all patients who undergo DHCA develop impaired glucose metabolism and require insulin to control blood sugars. Thrombocytopenia and clotting factor deficiencies prove to be a significant cause of early death after DHCA. Careful monitoring intra-procedure and post-procedure is needed. Although DHCA is necessary for some procedures,

268-589: A freestanding Ambulatory Care Center, and expanded parking options for visitors. In 1998, the Duke University Health System was created with newly established partnerships with Durham Regional Hospital and Raleigh Community Hospital . That same year, the National Institutes of Health partnered with Duke to offer the first joint master's of health science in a clinical research degree. With this extraordinary partnership,

335-401: A joint program leading to simultaneous M.D. and Ph.D. degrees , was established, becoming one of the first three in the nation. In 1969, the first recorded studies of human's abilities to function and work at pressures equal to a 1,000-foot (300 m) deep sea dive were conducted in the hyperbaric chamber . With the dawn of the 1970s, Duke underwent a period of expansion that continued well into

402-503: A mean temperature of 24 °C, and electrocerebral silence occurs at a mean temperature of 18 °C. The achievement of measured electrocerebral silence has been called "a safe and reliable guide" for determining cooling required for individual patients, and verification of electrocerebral silence is required prior to stopping blood circulation to begin a DHCA procedure. Secondary to conservation of local energy resources by metabolic slowing and brain inactivation, hypothermia also protects

469-638: A network of physicians and hospitals serving Durham County and Wake County, North Carolina , and surrounding areas, as well as one of three Level I referral centers for the Research Triangle of North Carolina (the other two are UNC Hospitals in nearby Chapel Hill and WakeMed Raleigh in Raleigh ). It is affiliated with the Duke University School of Medicine . The institution traces its roots back to 1924, six years before

536-499: A patient's body temperature down to less than 50 degrees Fahrenheit in an effort to minimize tissue damage during lengthy surgeries. With the success of this experiment, systemic hypothermia has become standard procedure in all hospitals worldwide. In 1957, the hospital and medical school were renamed Duke University Medical Center. In 1958, Thelma Ingles, a professor and chair of the Department of Medical-Surgical Nursing, developed

603-509: A state of cold circulatory arrest with the heart stopped until the cause of bleeding could be surgically repaired to allow later resuscitation. In preclinical studies at the University of Pittsburgh during the 1990s, the process was called deep hypothermia for preservation and resuscitation , and then suspended animation for delayed resuscitation . The process of cooling people with fatal bleeding for surgical repair and later resuscitation

670-403: A temperature of 5 °C, groundhogs could endure two hours of stopped blood circulation without ill effects. This research was motivated by a desire to stop the heart from beating long enough to do surgery on the heart while it remained still. Since heart-lung machines, also known as cardiopulmonary bypass (CPB), had not been invented yet, stopping the heart meant stopping blood circulation to

737-450: Is recommended that rewarming is stopped once the body is warmed to 37 °C. Post-operative hyperthermia is associated with adverse outcomes. Patients are completely rewarmed before discontinuing CPB, but temperature remain labile despite rewarming efforts which requires close monitoring in the ICU. The use of hypothermia following cardiac arrest shows increased likelihood of survival. It is

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804-404: Is skin irritation, shivering and rate of cooling. Intravascular cooling systems regulate temperature from inside veins such as the femoral, sub-clavian, or internal jugular to reduce adverse effects that external cooling methods cause. This method is unparalleled in achieving and maintaining the target temperature desired. The use of continuous renal replacement therapy (CRRT) has proven effective in

871-414: Is still used today. In 1963, Christiaan Barnard and Velva Schrire were the first to use DHCA to repair an aortic aneurysm , cooling the patient to 10 °C. Randall B. Griepp , in 1975, is generally credited with demonstrating DHCA as a safe and practical approach for aortic arch surgery. Cells require energy to operate membrane ion pumps and other mechanisms of cellular homeostasis . Cold reduces

938-569: Is used if life-saving surgery requires it. Infants tolerate longer periods of DHCA than adults. Applications of DHCA include repairs of the aortic arch , repairs to head and neck great vessels, repair of large cerebral aneurysms , repair of cerebral arteriovenous malformations , pulmonary thromboendarterectomy , and resection of tumors that have invaded the vena cava . The use of hypothermia for medical purposes dates back to Hippocrates, who advocated packing snow and ice into wounds to reduce hemorrhage. The origin of hypothermia and neuroprotection

1005-474: The public domain from page 547 of the 20th edition of Gray's Anatomy (1918) Anatomy Teaching Case from MedPix Duke University Hospital Duke University Hospital is a 1062 -bed acute care facility and an academic tertiary care facility located in Durham, North Carolina , United States . Established in 1930, it is the flagship teaching hospital for the Duke University Health System ,

1072-550: The thyroid ima artery , a variant artery supplying the thyroid gland may arise from the aortic arch. The aortic knob is the prominent shadow of the aortic arch on a frontal chest radiograph . Aortopexy is a surgical procedure in which the aortic arch is fixed to the sternum in order to keep the trachea open. Aortic isthmus is the relatively fixed part of the aortic arch. It is prone to shearing force and trauma that can cause it to tear and result in massive bleeding. [REDACTED] This article incorporates text in

1139-463: The 1960s. In these procedures, cooling was accomplished externally by applying cold water or melting ice to the surface of the body. The advent of cardiopulmonary bypass in the United States during the 1950s allowed the heart to be stopped for surgery without having to stop circulation to the rest of the body. Cooling more than a few degrees was no longer needed for heart surgery. Thereafter,

1206-519: The 1980s ushered in a twenty-year low in organizing and activism at the hospital. In 1980, Duke moved into its present $ 94.5 million facility (Duke North) on Erwin Road, located just north of its original location. In 1985, with the emergence of AIDS bringing alarm to the medical community, Duke became one of the first two hospitals to conduct human clinical trials on AZT , the first drug to offer an improved quality of life in patients battling AIDS. In

1273-491: The 1980s, it had been thought impossible to resuscitate people whose heart stopped because of blood loss, resulting in these people being declared dead when cardiac resuscitation failed. Traditional treatments such as CPR and fluid replacement or blood transfusion are not effective when cardiac arrest has already occurred and bleeding remains uncontrolled. Safar and Bellamy proposed flushing cold solution through blood vessels of patients with deadly bleeding, and leaving them in

1340-705: The 1980s. In December 1971, the Duke Comprehensive Cancer Center was established under the National Cancer Act . Duke's cancer center, one of the first in the nation under this groundbreaking legislation, was officially designated as a "comprehensive" cancer center by the National Cancer Institute in 1973. That same year, the Duke Eye Center was dedicated and opened on November 8. In 1978,

1407-449: The 1990s, the medical research at Duke reached the forefront for the detection of ailments that can be treated with a larger success rate. In 1990, Duke geneticists invented a three-minute test to screen newborns for over 30 metabolic diseases at one time. This practice has since become standard worldwide. In 1992, Duke's cancer center became the first hospital to develop an outpatient bone marrow transplant program. That same year,

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1474-553: The Morris Cancer Research Building opened, giving researchers a place to study and find cures for the disease. DCI partners with a number of other centers and institutes including North Carolina State University and the University of Michigan Rogel Cancer Center. During the 1970s, the hospital also faced two distinct unionization drives aimed at uniting the unskilled service workers of Duke Hospital. The 1974 and 1978 drives both ultimately failed, and

1541-507: The NIH became the first organization to offer a joint graduate degree program with a major university. In 2001, the hospital was the first to establish a center dedicated exclusively to Cardiovascular Magnetic Resonance Imaging . In December 2019, a team at the hospital became the first in the United States to transplant an adult heart into a recipient through a process known as donation after circulatory death. The transplant takes place after

1608-463: The Research section of this article. Since the benefits of hypothermia were discovered there have been numerous methods used to cool the body to desired temperatures. Hippocrates used snow and ice to surface cool wounded patients to prevent excessive bleeding. This method would fall under conventional cooling techniques, in which cold saline and crushed ice are used to induce a state of hypothermia to

1675-440: The anticipated medical uses of long circulatory arrest times, or so-called clinical suspended animation, is treatment of traumatic injury. In 1984 CPR pioneer Peter Safar and U.S. Army surgeon Ronald Bellamy proposed suspended animation by hypothermic circulatory arrest as a way of saving people who had exsanguinated from traumatic injuries to the trunk of the body. Exsanguination is blood loss severe enough to cause death. Until

1742-496: The aorta , or transverse aortic arch ( English: / eɪ ˈ ɔːr t ɪ k / ) is the part of the aorta between the ascending and descending aorta . The arch travels backward, so that it ultimately runs to the left of the trachea . The aorta begins at the level of the upper border of the second/third sternocostal articulation of the right side, behind the ventricular outflow tract and pulmonary trunk . The right atrial appendage overlaps it. The first few centimeters of

1809-406: The aorta . The ductus arteriosus connects to the final section of the arch in foetal life. Ductus arteriosus then regresses to become ligamentum arteriosum during later life. There are three common variations in how arteries branch from the aortic arch. In about 75% of individuals, the branching is "normal", as described above. In some individuals the left common carotid artery originates from

1876-438: The aortic arch is responsible for sensing changes in the dilation of the vascular walls, inducing changes in heart rate to compensate for changes in blood pressure. The aortic arch is the connection between the ascending and descending aorta, and its central part is formed by the left 4th aortic arch during early development. The ductus arteriosus connects to the lower part of the arch in foetal life. This allows blood from

1943-430: The aortic arch to the left of the left common carotid artery and ascends, with the left common carotid, through the superior mediastinum and along the left side of the trachea. An anatomical variation is that the left vertebral artery can arise from the aortic arch instead of the left subclavian artery. The arch of the aorta forms two curvatures: one with its convexity upward, the other with its convexity forward and to

2010-425: The arch of the aorta is the brachiocephalic trunk , which is to the right and slightly anterior to the other two branches and originates behind the manubrium of the sternum. Next, the left common carotid artery originates from the aortic arch to the left of the brachiocephalic trunk, then ascends along the left side of the trachea and through the superior mediastinum. Finally, the left subclavian artery comes off of

2077-499: The arch. The diameter of the descending aorta should not exceed 25 mm. The arch of the aorta lies within the mediastinum . At the cellular level, the aorta and the aortic arch are composed of three layers: The tunica intima , which surrounds the lumen and is composed of simple squamal epithelial cells; the tunica media , composed of smooth cell muscles and elastic fibers; and, the tunica adventitia , composed of loose collagen fibers. Innervated by barometric nerve terminals,

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2144-467: The ascending aorta and pulmonary trunk lies in the same pericardial sheath . and runs at first upward, arches over the pulmonary trunk , right pulmonary artery , and right main bronchus to lie behind the right second coastal cartilage. The right lung and sternum lies anterior to the aorta at this point. The aorta then passes posteriorly and to the left, anterior to the trachea, and arches over left main bronchus and left pulmonary artery , and reaches to

2211-562: The bottom of this temperature range. Profound hypothermia (< 14 °C) usually isn't used clinically. It is a subject of research in animals and human clinical trials. As of 2012, the lowest body temperature ever survived by a human being was 9 °C (48  °F ) as part of a hypothermic circulatory arrest experiment to treat cancer in 1957. This temperature was reached without surgery, using external cooling alone. Similar low temperatures are expected to be reached in emergency preservation and resuscitation (EPR) clinical trials described in

2278-451: The brachiocephalic artery rather than the aortic arch. In others, the brachiocephalic artery and left common carotid artery share an origin. This variant is found in approximately a 20% of the population. In a third variant, the brachiocephalic artery splits into three arteries: the left common carotid artery, the right common carotid artery and the right subclavian artery; this variant is found in an estimated 7% of individuals. In rare cases,

2345-707: The brain from injury by other mechanisms during stopped blood circulation. These include reduction of free radicals and immune-inflammatory processes. Mild hypothermia (32 °C to 34 °C) and moderate hypothermia (26 °C to  31 °C) are contraindicated for hypothermic circulatory arrest because 100% and 75% of people respectively will not achieve electrocerebral silence in these temperature ranges. Consequently, safe circulatory arrest times for mild and moderate hypothermia are only 10 and 20 minutes respectively. While moderate hypothermia may be satisfactory for short surgeries, deep hypothermia (20 °C to 25 °C) affords protection for times of 30 to 40 minutes at

2412-619: The brain. When compared to Moderate Hypothermia (temperature dropped to 26-31 °C), there was less bleeding volume experienced during surgery thus leading to less use of packed red blood cells or plasma post surgery. Longer recovery time postoperatively have been noted with DHCA as compared to Moderate Hypothermia, but the length of hospital stay and death has no correlated difference. Most patients can tolerate 30 minutes of DHCA without significant neurological dysfunction or adverse effects, but after an extended period of 40 minutes or more, prevalence of increased brain injury have been noted. One of

2479-429: The clinical nursing specialist program, becoming the first master's program of its kind in the United States. The establishment of the nursing specialist program paved the way for advanced clinical knowledge in the delivery and teaching of the nursing field. The 1960s brought extraordinary firsts to Duke. In 1963, the first African-American student was accepted to the prestigious medical school. Two years later, in 1965,

2546-511: The first two organized in the country. In 1955, psychiatrist Ewald W. Busse established the Duke University Center for Aging, the first research center of its kind in the nation. Currently the oldest continuously operating facility in the United States, this center has pioneered long-term studies of health problems among seniors. In 1956, Duke surgeons performed the first cardiac surgery using systemic hypothermia to bring

2613-409: The heart has stopped beating and the person is declared dead. In 2019, Duke Regional Hospital began a major expansion project on its emergency department and behavioral health unit. The $ 102.4 million project will increase the number of private rooms and increase the number of outpatient behavioral health clinic rooms from 19 to 30. In September 2021, doctors at Duke University Hospital completed

2680-448: The heart is not functioning. In 1959, using cardiopulmonary bypass (CPB), Barnes Woodhall and colleagues at Duke Medical Center performed the first brain surgery using DHCA, a tumor resection, at a brain temperature of 11 °C and esophageal temperature of 4 °C. This was quickly followed by use of DHCA by Alfred Uihlein and other surgeons for treatment of large cerebral aneurysms , another neurosurgical procedure, for which DHCA

2747-416: The heart stops beating completely ( asystole ), which is protective of both the heart and brain when circulation is later stopped. Cooling continues until the brain is inactivated by the cold, and electrocerebral silence (flatline EEG) is attained. The blood pump is then switched off, and the interval of circulatory arrest begins. At this time more blood is drained to reduce residual blood pressure if surgery on

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2814-693: The hospital and medical school were officially dedicated on April 20 and the Private Diagnostic Clinic (Duke's in-house physician system) was organized on September 16. In 1935, less than five years after the hospital opened, the American Medical Association ranked Duke among the top 20 of medical schools in the country. In 1936, a team of physicians led by Dr. Julian Deryl Hart introduced ultraviolet light in operating rooms in an effort to kill germs and combat post-operative staph infections , greatly reducing

2881-509: The hospital established the first physician assistant program in the country. In 1966, Duke became the first medical center in the world to offer radio consultations with physicians in developing countries. This program, called Med-Aid (short for Medical Assistance for Isolated Doctors), met the critical needs of the physicians who lacked proper treatment. That same year, the Medical Scientist Training Program,

2948-677: The hospital made its first expansion, adding a new wing to the original building. In 1946, the Division of Thoracic Surgery, today the Duke Division of Cardiovascular and Thoracic Surgery, was organized by Josiah Charles Trent . In 1947, the Bell Research Building became the first freestanding building on the hospital campus. In 1954, the Duke Poison Control Center was organized, becoming one of

3015-635: The hospital performed its first lung and heart/lung transplants. The year 1994 marked the beginning of accelerated expansion for Duke. That year, the Levine Science Research Center and the Medical Sciences Research Center were opened. In addition, there were extensive renovations of the Duke Clinic (Duke South), additions to the Morris Cancer Research Building, a new Children's Health Center,

3082-449: The increased oxygen demand that occurs with rapid rewarming. Several theories have been proposed, with one being during re-warming, the body releases increasing catecholamines which increase heat production leading to a loss of thermoregulation. Hyperthermia in the preperfusion period can also be caused by an increase in the production of oxygen radicals, which influences brain metabolism. These oxygen radicals attack cell membranes, leading to

3149-412: The induction of hypothermia as an intravascular cooling system. People who are to undergo DHCA surgery are placed on cardiopulmonary bypass (CPB), a procedure that uses an external heart-lung machine that can artificially replace the function of the heart and lungs. A portion of the circulating blood supply is removed and stored for later replacement, with the remaining blood diluted by added fluids with

3216-410: The largest blood vessel of the body ( aorta ). By remaining in circulatory arrest at temperatures below 10 °C (50 °F), it is believed that surgeons have one to two hours to fix injuries before circulation must be restarted. Surgeons involved with this research have said that EPR changes the definition of death for victims of this type of trauma. Aortic arch The aortic arch , arch of

3283-550: The left side of the T4 vertebral body. Apart from T4 vertebral body, other structures such as trachea, oesophagus, and thoracic duct (from front to back) also lies to the left of the aorta. Inferiorly, the arch of aorta is connected to ligamentum arteriosum while superiorly, it gives rise to three main branches. Arch of aorta continues as the descending aorta after T4 vertebral body. The aortic arch has three main branches on its superior aspect. The first, and largest, branch of

3350-441: The left. Its upper border is usually about 2.5 cm. below the superior border to the manubrium sterni . Blood flows from the upper curvature to the upper regions of the body, located above the heart - namely the arms, neck, and head. Coming out of the heart, the thoracic aorta has a maximum diameter of 40 mm at the root. By the time it becomes the ascending aorta, the diameter should be < 35–38 mm, and 30 mm at

3417-454: The metabolic rate of cells, which conserves energy stores ( ATP ) and oxygen needed to produce energy. Cold therefore extends the length of time that cells can maintain homeostasis and avoid damaging hypoxia and anaerobic glycolysis by conserving local resources when blood circulation is stopped and unable to deliver fresh oxygen and glucose to make more energy. Normally 60% of brain oxygen utilization (CMRO2) consists of energy generation for

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3484-430: The neuronal action potentials of brain electrical activity . A key principle of DHCA is total inactivation of the brain by cooling, as verified by "flatline" isoelectric EEG , also called electrocerebral silence (ECS). Instead of a continuous decrease in activity as the brain is cooled, electrical activity decreases in discontinuous steps. In the human brain, a type of reduced activity called burst suppression occurs at

3551-402: The number of infections and related deaths. In the same year, the hospital established the nation's first brain tumor program, launching what would become one of the world's most renowned programs in the field of cancer treatment. In 1937, Joseph Beard developed a vaccine against equine encephalomyelitis , one of the first known vaccines to combat the mosquito -carried disease. In 1940,

3618-477: The objective of reducing viscosity and clotting tendencies at cold temperature. The remaining diluted blood is cooled by the heart-lung machine until hypothermia causes the heart to stop beating normally, after which the blood pump of the heart-lung machine continues blood circulation through the body. Corticosteroids are typically given 6–8 hours before surgery as it has shown to have neuroprotective properties to decrease risk of neurological dysfunction by decreasing

3685-406: The only surgeries that required stopping blood circulation to the whole body ("total circulatory arrest") were surgeries involving blood supply to the brain. The only heart surgeries that continued to require total circulatory arrest were repairs to the aortic arch . Cardiopulmonary bypass machines were essential to the development of deep hypothermic circulatory arrest (DHCA) in humans. By 1959, it

3752-518: The opening of the hospital, when James Buchanan Duke established the Duke Endowment to transform Duke University (then known as Trinity College) into the research university it is today. In 1925, Duke bequeathed $ 4 million to establish the medical school , nursing school , and hospital. Two years later, in 1927, construction began on the original hospital (now known as Duke South), which opened on July 21, 1930, with 400 beds. In 1931,

3819-570: The patient. These techniques are inexpensive but lack the precision needed to maintain target temperatures and require careful monitoring. It has been proven to help prevent undesirable rewarming of the brain during DHCA. Hospitals and emergency medical services commonly use surface cooling systems that circulate cold air or water around blankets or pads. Advantages of this method are accuracy of cooling due to auto-regulating temperature control, feedback probes, applicable in non-hospital settings, and non-complexity of use. Drawbacks to surface cooling systems

3886-522: The period of complete inactivation just prior to and during the circulatory arrest interval, barbiturate infusion is used to keep the brain in a state of burst suppression for the entirety of the DHCA procedure until emergence from anesthesia. Hypothermic perfusion is maintained for 10–20 minutes while on CPB before rewarming as to reduce the risk of increased intracranial pressure. Warming must be done carefully to avoid overshooting normal body temperature. It

3953-416: The re-warming period that, if not controlled properly, can have detrimental effects. Hyperthermia during the re-warming period shows unfavorable neurologic outcomes. For each degree the body is warmed above 37 °C, there is an increased association with severe disability, coma, or vegetative states. Excessive rewarming with temperatures above 37 °C can increase the risk of cerebral ischemia secondary to

4020-427: The release of inflammatory cytokines. Glucose is eliminated from all intravenous solutions to reduce the risk of hyperglycemia. In order for accurate hemodynamic monitoring, arterial monitoring is typically placed in the femoral or radial artery. Temperature taken from two separate sites, typically the bladder and nasopharynx, is used to estimate brain and body temperatures. Cardioplegic drugs may be administered to ensure

4087-462: The right ventricle to mostly bypass the pulmonary vessels as they develop. The final section of the aortic arch is known as the aortic isthmus. This is so called because it is a narrowing ( isthmus ) of the aorta as a result of decreased blood flow when in foetal life. As the left ventricle of the heart increases in size throughout life, the narrowing eventually dilates to become a normal size. If this does not occur, this can result in coarctation of

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4154-709: The use of anesthesia can provide optimum operation time and organ protection but can also have serious impacts on cellular demand, brain cells, and serious systemic inflammatory results. Possible disadvantages of DHCA includes alteration in organ functions of the liver, kidney, brain, pancreas, intestines and smooth muscles due to cellular damage. Permanent neurological injury has been seen in 3-12% of patients when using DHCA. Cases of partial or complete limb motor loss, impaired language, visual defects, and cognitive decline have all been reported as consequences of DHCA. Other neurological complications are increase risk for seizures postoperative due to delayed return of cellular blood flow to

4221-619: The whole body, including the brain. The first heart surgery using hypothermia to provide a longer time that blood circulation through the whole body could be safely stopped was performed by F. John Lewis and Mansur Taufic at the University of Minnesota in 1952. In this procedure, the first successful open heart surgery , Lewis repaired an atrial septal defect in a 5-year-old girl during 5 minutes of total circulatory arrest at 28 °C. Many similar procedures were performed by Soviet heart surgeon, Eugene Meshalkin, in Novosibirsk during

4288-508: Was also observed in infants who were exposed to cold due to abandonment and the prolonged viability of these infants. In the 1940s and 1950s, Canadian surgeon Wilfred Bigelow demonstrated in animal models that the length of time the brain could survive stopped blood circulation could be extended from 3 minutes to 10 minutes by cooling to 30 °C before circulation was stopped. He found that this time could be extended to 15 to 24 minutes at temperatures below 20 °C. He further found that at

4355-443: Was difficult and hazardous. At temperatures below 24 °C, the human heart is prone to fibrillation and stopping. This can begin circulatory arrest before the brain has reached a safe temperature. Cardiopulmonary bypass machines allow blood circulation and cooling to continue below the temperature at which the heart stops working. By cooling blood directly, cardiopulmonary bypass also cools people faster than surface cooling, even if

4422-407: Was finally called Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma (EPR-CAT), or EPR. It is presently undergoing human clinical trials. In the trials, patients who experience clinical death for less than five minutes duration from blood loss are being cooled from normal body temperature of 37 °C to less than 10 °C by pumping a large quantity of ice-cold saline into

4489-460: Was known from the animal experiments of Bigelow, Andjus and Smith , Gollan, Lewis's colleague, Niazi, and others that temperatures near 0 °C could be survived by mammals, and that colder temperature permitted the brain to survive longer circulatory arrest times, even beyond one hour. Humans had survived cooling to 9 °C, and circulatory arrest of 45 minutes, using external cooling only. However, reaching such low temperatures by external cooling

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