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Query: UMLS:C0020672 (hypothermia)
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Because severe cardiac insufficiency follows orthotopic heart transplantation, the authors have evaluated protection of the homograft provided by a cooling and isolating bag during the operative period of ischemia and subsequently its effect on cardiac function. In one group or four dogs hearts were transplanted without using hypothermia. In the second group, seven hearts were excised, immediately cooled by immersion in saline at 4 degrees C and orthotopically homotransplanted. In the third group, six hearts were immersed in saline and then isolated in a cooling bag until transplantation had been completed. Cardiac function in all animals was evaluated at rest, 3, 24 and 48 hours after operation. In group 1, lowering of the temperature was minimal and all animals died immediately after operation. In group 2, the myocardial temperature, which had been lowered to 13 degrees C by immersion, had risen to 25 degrees C after 17 minutes. In group 3, the myocardial temperature was maintained at 13 degrees C up to the time the aortic clamp was removed. Three hours after operation, the cardiac performance of group 3 was much better than that of group 3 was much better than that of group 2 as demonstrated by an increase of cardiac output (39%), stroke volume (44%), mean systolic ejection rate (25%), maximum systolic flow (28%), peak velocity (26%), maximum acceleration (20%), left ventricular power (32%) and left ventricular work (47%). In the following days, cardiac function of groups 2 and 3 improved and the disparity between then decreased. These results demonstrate that the cooling bag, while offering technical advantages, maintains profound hypothermia in the donor heart and substantially improves the performance of the homograft in the immediate postoperative phase.
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PMID:Protection of the myocardial homograft. 1. The cooling bag. 701 85

The homotransplanted heart is in severe failure in the immediate post-operative period, secondary to ischemia inherent to the technic of orthotopic transplantation. The present work was carried out to investigate if ventricular fibrillation followed by cold coronary perfusion could protect the homograft during implantation by evaluating the post-operative cardiac performance. In the control group, 7 hearts were excised, immediately immersed in physiological saline at 5 degrees C, and homotransplanted. In a second group of 4 grafts, ventricular fibrillation was induced and the coronary bed was perfused immediately with cold (5 degrees C) extracellular solution for a period of 10 minutes before orthotopic implantation. All animals were prepared at the end of surgery for hemodynamic studies to be carried out 3, 24 and 48 hours post-operatively in the resting state. In group I, the myocardial temperature dropped to 13.5 degrees C in 14.5 minutes. In group II, the hypothermia by perfusion was more rapid and deeper (11 degrees C within 10 minutes). Three hours post-operatively, cardiac function of group II was superior to that of group I as demonstrated by the increase of cardiac index (39%), stroke volume index (41%) mean systolic ejection rate index (44%), maximum systolic flow index (58%), maximum acceleration index (36%), stroke power index (88%), stroke work index (67%). Twenty-four and forty-eight hours post-operatively the cardio-vascular function improved in both groups but remained superior in group II. These results demonstrate that ventricular fibrillation followed by cold coronary perfusion increases protection of the homograft during the initial period of implantation.
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PMID:[Myocardial protection of the homograft. III - Evaluation of ventricular fibrillations with hypothermic coronary perfusion (author's transl)]. 703 51

Two cases of deep hypothermia due to exposure to cold are described. Although the underlying mechanism and degree of hypothermia were comparable, there was a striking dissimilarity between the observed disturbances of body homeostasis, response to rewarming technique, clinical course and outcome in the two cases. The first case was severely acidotic. She was rewarmed by immersion in warm water, but died from an acute cerebrovascular accident. The second case was moderately intoxicated by alcohol and revealed few disturbing features. She was treated by the use of thermal mattresses and survived without complications.
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PMID:Accidental deep hypothermia due to exposure. 711 23

The hypothesis tested was that the composition of the prime and the perfusate at the time of reperfusion had an influence on postischemic cardiac performance. Twelve dogs in two equal groups had long (210 +/- 10 minutes) hypothermic (25 degrees +/- 1 degree C) perfusions. Each had 180 minutes of global ischemia and were given 500 ml of the same cold (4 degrees C) cardioplegic solution (CPS) every 45 minutes and topical hypothermia with a resultant average myocardial temperature of 10 degrees +/- 2 degrees C. Group A had a prime (1,958 ml) consisting of a 50/50 mixture of 5% dextrose in water and 5% dextrose in Ringer's injection to which mannitol (12.5 gm), furosemide (20 mg), and heparin (6,000 units) were added. Group B received a prime (1,868 ml) of 5% dextrose in Ringer's injection (1 L) and 750 ml of 6% helastarch in normal saline to which NaHCO3 (10 mEq), furosemide (20 mg), mannitol (25 gm), and heparin (6,000 units) were added. During perfusion, Group A received lactated Ringer's solution and Group B received a 1 : 2 portions of Ringer's injection and 6% helastarch. Additionally, Group B received additional furosemide and mannitol 5 minutes prior to the reperfusion interval. The results showed a marked difference between groups in postischemic cardiac recovery 120 minutes after cessation of cardiopulmonary bypass. The Group B dogs had statistically (less than 0.02) greater cardiac output, stroke volumes, and stroke work index at equal preloads and lower total peripheral resistances. Arterial systolic, diastolic, and mean pressures and right atrial pressures were not different. The Group A dogs required nearly threefold the volume of fluid additions required during bypass and twice the amount of NaHCO3 as Group B dogs. It is concluded that the composition of the prime and fluids used during bypass and use of agents to counteract tissue water accumulation during the ischemic and reperfusion intervals strongly influences postischemic cardiac performance. Further, these data suggest that the composition of the perfusate may have a greater influence on the functional recovery of the heart than the composition of various CPSs.
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PMID:Adequacy of the perfusate: its influence on successful myocardial protection. 713 9

Aspartate aminotransferase (EC 2.6.1.1:AST) is known to have two isoenzymes, one associated with the cytoplasm (c-AST) and the other with the mitochondria (m-AST). We studied the relationships of m-AST activity in the coronary sinus blood to left ventricular function, coronary blood flow, water content and high-energy phosphate stores of the left ventricle following hypothermic ischemic cardiac arrest. Under cardiopulmonary bypass with hypothermia of 20 degrees C of myocardial temperature, 120 min of aortic occlusion was employed in 15 mongrel dogs. Left ventricular function (peak left ventricular pressure, left ventricular end-diastolic pressure, max dp/dt, cardiac index, left ventricular stroke work index), coronary blood flow, myocardial oxygen consumption, myocardial enzyme activity (m-AST, CK-MB), myocardial water content and high-energy phosphate stores (adenosine triphosphate, creatine phosphate) of the subendocardium of the left ventricle were measured. Data was obtained in the control state, and after 0, 30 and 60 min of reperfusion. Significant negative correlations were obtained between m-AST activity and peak left ventricular pressure (r = -0.81, p less than 0.001), max dp/dt (r = -0.83, p less than 0.001), cardiac product (r = -0.73, p less than 0.01), coronary blood flow (r = -0.59, p less than 0.05), adenosine triphosphate level (r = 0.72, p less than 0.01) and creatine phosphate level (r = -0.72, p less than 0.02) after 60 min of reperfusion. Significant positive correlations were obtained between m-AST activity and left ventricular end-diastolic pressure (r=0.75, p less than 0.01) and water content (r = 0.78, p less than 0.01) after 60 min of reperfusion. These results led to the assumption that serum m-AST activity in the coronary venous blood is a useful index to evaluate the degree of myocardial injury.
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PMID:Studies on the significance of serum mitochondrial aspartate aminotransferase activity following ischemic cardiac arrest. 714 3

We have previously shown that an intracellular-like crystalloid cardioplegic solution (ICS) provides superior protection to normothermic canine hearts subjected to 1 hour of global ischemia (GI) in comparison to a standard extracellular-type clinical cardioplegic solution (CPS). The addition of a calcium antagonist, nifedipine (N), to CPS was shown to be salutory. The new experiments used systemic hypothermia (25 degrees +/- 1 degrees C) and multidose (500 ml) cold (4 degrees C) CPS or ICS with and without N (200 to 400 micrograms/L) every 30 to 45 minutes during GI intervals of 3 hours at a resultant myocardial temperature of 10 degrees +/- 2 degrees C. The results show that after 3 hours of GI and 2 hours of observation stroke work index, (SWI) decreased to 50% +/- 10% of control for the CPS, ICS, and CPS + N groups. The ICS + N group had excellent preservation with left ventricular (LV) SWI and first derivatived left ventricular pressure (LV dP/dt) equal to the preischemic valve. Cardiac output was increased above control levels and responded normally to volume loading. Possible mechanisms of nifedipine and CPS interactions are discussed. It is concluded that a low sodium ICS containing N is highly efficacious for long ischemic intervals and that composition of the CPS strongly influences the effects of N on postischemic performance.
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PMID:Three-hour preservation of the hypothermic globally ischemic heart with nifedipine. 731 49

Accidental hypothermia, a core temperature below 34 degrees C., is frequently fatal, particularly in the ill and elderly. Traditional treatment methods result in reported mortalities of between 45 and 100 per cent. Despite these terrible statistics, advocates of slow rewarming persist. They cite the shock and vascular collapse which can occur with peripheral dilation as reasons to avoid rapid external rewarming. Isolated successes using internal core rewarming, such as hemodialysis or cardiopulmonary bypass, are spectacular but not practical in the usual clinical situation. By combining methods used for the resuscitation of burn injury with the treatment principles for frostbite, a highly effective treatment protocol results. Agressive fluid resuscitation, rapid immersion rewarming and careful systematic monitoring have been used to treat ten consecutive patients without a single death. Concomitant problems of alcoholism, stroke, myxedema, tuberculosis and paraplegia were also treated. Rapid external rewarming by immersion can result in a low mortality in patients with severe hypothermia.
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PMID:Accidental hypothermia treated without mortality. 740 8

1. Hypothermia to a temperature of 30 degrees C was induced in both shivering and non-shivering groups of dogs. 2. There was a sustained increase in oxygen consumption in the dogs allowed to shiver and this was up to 300% greater than the oxygen consumption in the relaxed dogs. 3. The increased tissue requirement for oxygen was met both by increased cardiac output and increased oxygen extraction from haemoglobin. 4. Oxygen utilization remained adequate in hypothermia, as shown by the absence of hypoxic acidosis. 5. Heart rate fell during cooling and stroke volume increased to meet the increased oxygen demands associated with shivering during the induction of hypothermia.
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PMID:Cooling responses in shivering and non-shivering dogs during induced hypothermia. 742 82

Moderate systemic hypothermia has been shown to improve neurologic outcomes in both fluid-percussion and cortical contusion models of experimental brain injury. Based upon initial clinical work, it was concluded that at temperatures < 32 degrees C, patients with severe brain injury were at increased risk of ventricular arrhythmias, and that rapid rewarming immediately postinjury predisposed to intracranial pressure increases. Subsequent clinical studies of moderate hypothermia (32 degrees C) for 24- to 48-hr duration with slow rewarming in human brain injury showed indications of neurologic improvement and a low incidence of hypothermia-related complications. Based upon the strengths of both laboratory and clinical data, a multicenter (nine centers), randomized, prospective trial testing moderate systemic hypothermia in patients with severe brain injury has been organized. This trial, funded by National Institutes of Health, National Institute of Neurological Disorders and Stroke, began on October 20, 1994. Five hundred patients are to be treated in an intent-to-treat protocol using standard management at normothermia versus standard management at hypothermia. The trial is designed to detect an absolute shift of 12% in the percentage of patients achieving satisfactory outcome (good recovery/moderate disability) at a power of 85% at 6 months postinjury. The efficacy of hyperbaric oxygen administered every 8 hrs for 1-hr duration for a 2-wk period has also been tested in patients after severe brain injury. While the mortality rate was reduced in the treated group, the percentage of favorable outcomes was unchanged. Further studies are in progress.
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PMID:Hypothermia and hyperbaric oxygen as treatment modalities for severe head injury. 749 57

During last 7 years, we performed 24 operations on the thoracoabdominal aorta. There were 9 true and 15 dissecting aneurysms. There were two cases of ruptured aneurysm and thoracoabdominal replacement was performed as a last stage operation for total aortic replacement in 4 cases. Three cases with aortic dissection died within 30 days after surgery. Femoro-femoral bypass was used in 4 cases (1 case died of brain damage, paraplegia and MOF), left heart bypass in 5 cases and separate perfusion of upper and lower body (SPULB) under deep hypothermia in 7 cases (2 cases died of LOS and cerebrovascular accident occurred at 2 weeks after operation) and SPULB with mild hypothermia in 8 cases for circulatory support. There was one case of renal dysfunction and transient mild liver dysfunction occurred in 7 cases. There was no evidence on relationship between surgical outcome and methods of circulatory supports, but we recently prefer SPULB under mild hypothermia for thoracoabdominal surgery since intraoperative massive bleeding and cardiac arrest can be easily treated and major organs can be protected by introducing hypothermia in this perfusion technique.
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PMID:[Separate perfusion of upper and lower body under mild hypothermia during operation on the thoracoabdominal aorta]. 756 31


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