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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ideal method for the preservation of donor hearts for transplantation is unclear. To assess the optimal temperature for donor myocardium preservation, the recovery of isolated canine hearts (n = 20) exposed to 4 hours of either standard ice-chest hypothermia (0-4 degrees C) or constant moderate hypothermia (12 degrees C) were compared. Functional and metabolic data were acquired before hypothermia and every 30 minutes during 3 hours of reperfusion with oxygenated blood. Mean end-systolic pressure-volume slopes were 2.11 +/- 0.06 and 2.09 +/- 0.06 mm Hg/ml for ice-chest hypothermia and constant moderate hypothermia, respectively (p = NS), which were unchanged from control. All y intercepts during reperfusion were decreased compared with control (p = 0.002) without any differences between groups. End-diastolic pressures were greater than control throughout the reperfusion period for both groups (p = 0.02), but there was a difference in change of end-diastolic pressures with time between groups (p = 0.04). Dry/wet ratios were similar after preservation and reperfusion in both groups. ATP recovered to control levels during reperfusion for both groups although energy charge ratios were greater for hearts exposed to constant moderate hypothermia (p = 0.007). These data indicate that intracellular energy stores are well maintained by preservation using either technique. Changes in function appear to be related to altered compliance irrespective of preservation temperature. These data suggest that a wide range of temperatures may be acceptable for donor heart preservation.
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PMID:Optimal temperature for preservation of donor myocardium. 222 22

The objective of this study was to define the degree of hypothermia required to diminish ischemic injury to CA1 hippocampal neurons following 5-min bilateral ischemia in the gerbil. The temperature of the body and head was regulated in three groups of animals at 37.5, 35.5, or 32.5 degrees C during 5-min bilateral carotid artery occlusion. Upon recirculation, normothermia was restored in all animals, and recovery was permitted for 1 week. Ischemic injury to CA1 hippocampus was determined using three endpoints: histologic injury, ATP content, and adenylate kinase activity. Reduction of head temperature to 35.5 and 32.5 degrees C during ischemia diminished histologic injury and improved CA1 levels of ATP and adenylate kinase activity in a dose-dependent manner. Indeed, 32.5 degrees C completely abolished ischemic injury to CA1 hippocampus, judging from each of the three endpoints. Reduction of head temperature to 32.5 degrees C delayed but did not prevent the depletion of ATP throughout the hippocampus during the 5-min ischemic insult. These results demonstrate that a decrease in head temperature of only 2 degrees C reduces the degree of CA1 injury in the gerbil model of 5-min bilateral ischemia. Thus, it is imperative to maintain strict normothermia in pharmacologic studies of ischemic protection. Finally, administration of nicardipine to normothermic gerbils failed to diminish ischemic injury in the CA1 hippocampus.
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PMID:Mild hypothermia prevents ischemic injury in gerbil hippocampus. 234 86

To test the hypothesis that hypothermia prevents myocardial Ca2+ loading during reoxygenation, we examined the effects of 2 h of hypoxia with and without hypothermia on the Ca2+ content of cultured chick embryo ventricular cells. When compared with hypoxic cells at 37 degrees C, hypoxia at 11 degrees C (hypothermia) augmented the 45Ca content of cardiocytes after 30 min of normothermic reoxygenation from 3.85 +/- 0.2 to 4.7 +/- 0.1 nmol/mg protein (P less than 0.001). The Na+ content of hypoxic myocytes was also increased at the end of 2 h of hypoxia from 648 +/- 59 to 1,026 +/- 68 nmol/mg protein in cells exposed to hypoxia at 11 degrees C (P less than 0.001). Hypothermia ameliorated hypoxia-induced depression of cellular ATP content and did not result in significant membrane injury as determined by lactate dehydrogenase release. These data indicate that hypothermia augments rather than decreases the Ca2+ content of hypoxic myocytes during reoxygenation after hypoxia. Ca2+ loading appears to be secondary to an increase in Na+ content, creating a favorable gradient for Ca2+ influx through Na(+)-Ca2+ exchange or an unfavorable gradient for Ca2+ extrusion.
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PMID:Hypothermia increases calcium content of hypoxic myocytes. 238 17

The possible myocardial protective effect of oral propranolol in combination with potassium cardioplegia and hypothermia was investigated in 30 greyhounds, divided into 2 sub-groups, by determining the changes in myocardial ATP and CP levels, ultrastructural changes and the changes in hemodynamics after a 2-hour period of myocardial ischemia. In group 1, in animals with multiple doses of cardioplegia during the 2-hour ischemic period, preoperative treatment with propranolol did not have a significant myocardial protective effect. In group 2, in animals with a single dose of cardioplegia, during the 2-hour ischemic period, propranolol resulted in a trend of improved survival, although the myocardial ATP and CP levels were the same in both sub-groups. In addition, the multiple doses of cardioplegia in group 1 caused increased subcellular edema in the myocardium. This study suggests that oral propranolol treatment may provide additional myocardial protection during ischemic periods when used with potassium cardioplegia and hypothermia. The mechanism of this effect is not established, but could relate to reduced transmembrane calcium influx.
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PMID:Oral beta-blockade with hypothermic potassium cardioplegia in cardiac surgery: is there an additive protective effect? 242 43

In hypoxia sensitive cells and tissues, the rates of glucose and O2 consumption are inversely related (Pasteur Effect). Under O2 limiting conditions the demands for glucose (glycogen) in such cells may drastically rise as a means for maintaining ATP turnover close to normoxic rates; nevertheless ion and electrical potentials cannot be sustained due to energy insufficiency and high membrane permeability; metabolic and membrane functions, in effect, are decoupled. 'Good' animal anaerobes resolve these problems with a number of biochemical and physiological mechanisms; of these metabolic arrest and stabilized membrane functions are the most effective strategies for extending hypoxia tolerance. Metabolic arrest is achievable by means of a reversed or negative Pasteur Effect (reduced or unchanging glycolytic flux at reduced O2 availability) while coupling of metabolic and membrane function is achievable in spite of the lower energy turnover rates by maintaining membranes of low permeability (probably via reduced densities of ion-specific channels). Although the strategy of combining metabolic arrest with channel arrest has been recognized as a possible intervention, to date success has been minimal, mainly because cold depression of metabolism is the usual arrest mechanism used and this hypothermia in itself perturbs controlled cell function in most endotherms. The only endothermic systems currently known which appear able to use the dual strategy for extending hypoxia tolerance are hypoperfused hypometabolic tissues and organs of diving marine mammals.
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PMID:Metabolic arrest. 242 20

To elucidate the metabolic changes during a relatively short ischemic period, papillary muscle excisions were investigated in 38 patients operated for mitral valve replacement. The overall mean age was 62 years, in 27 women and 11 men. Two excisions were made during ischemia, the first after 13 minutes and the second after 48 minutes of aortic occlusion. These excisions were analyzed for adenine nucleotide, creatine phosphate, lactate and pyruvate contents. The results indicated an ongoing metabolism with an accumulation of lactate, and also influences on the energy charge. For example, although the content of ATP was unchanged between the excisions, the relation to creatine phosphate, as a source for ATP level maintenance, was altered. This is of clinical importance since cardioplegia and hypothermia (myocardial temperature below 20 degrees C) were employed and the interval between the excisions was only 35 minutes on average. Although no significant decrease in myocardial ATP took place, 31 of 38 patients needed inotropic support to wean them off bypass. On the basis of the present results further efforts seem necessary to improve myocardial preservation techniques.
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PMID:Myocardial energy metabolism during mitral valve replacement. 243 93

In the experiments performed on white male rats (150-170 g of body mass) effect of total deep hypothermia has been studied in macrophages of the skin and regional suprascapular lymph node of various localization: Langerhans cells of the epidermis, histiocytes of the derm and hypoderm, macrophages of medullary sinuses, interdigitating cells of T-zones in the lymph node. After narcotization the animals are cooled with the rate 1 degree C per 5 min up to the rectal temperature of 18 degrees C. They are kept at this temperature for 2 h, and then are warmed with the same rate up to 37 degrees C. Actively phagocytizing macrophages of the skin and lymph node are revealed by their adsorption of trypan blue. The Langerhans and interdigitating cells of the lymph node are revealed by means of the ATP-ase method. After the cooling effect functional activity of macrophages with various localization increases. For the Langerhans cells it is manifested as a greater amount of the cells and their processes, for the interdigitating cells--as an elevated ATP-ase activity in 7 and 30 days after the experiment. Dermal histiocytes and macrophages of the lymph node sinuses respond to the cooling with an increasing adsorption of tripan blue. Amount of the cells, that adsorb the dye also increases. A conclusion is made that after the hypothermal effect protective-barrier properties of the dermal region increase.
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PMID:[Changes in the functional activity of macrophages of the skin and regional lymph node after exposure of albino rats to total deep hyperthermia]. 252 38

The effects of arterial alphastat regulation on brain intracellular pH (pHi) and several phosphate metabolites were assessed in anesthetized rats during hypothermia (28.6 +/- 0.2 degrees C) and normothermia (36.2 +/- 0.2 degrees C) by using 31P high-field (8.5 T) nuclear magnetic resonance (NMR). There were significant differences in pHi and metabolite ratios at the two temperatures under conditions of equal minute ventilation. During hypothermia, the brain pHi was 0.09 U higher, the phosphocreatine-to-inorganic phosphate (PCR/Pi) ratio 49% larger, and Pi-to-ATP 20% lower than at normothermia. These changes were fully reversible on warming the animal. The change in brain pHi/temperature was -0.011U/degrees C (95% confidence interval -0.007 to -0.016). The brain's ability to regulate its pHi and phosphate metabolism during hypercapnic acid-base stress was studied by using 10% CO2 ventilation. Hypothermic rats showed a larger fall in brain pHi (0.145 +/- 0.01 U, 7.15-7.01) with 10% CO2 than normothermic rats (0.10 +/- 0.02 U, 7.06-6.96). Similarly ventilated rats had a larger fall in arterial pH with 10% CO2 at hypothermia (0.36 +/- 0.04 U) than normothermia (0.24 +/- 0.01 U), so the delta brain pH/delta arterial pH was the same at both temperatures. The brain PCr-to-Pi ratio decreased approximately 20% during 10% CO2 breathing in both hypothermic and normothermic animals. Brain pHi and metabolite ratios returned to base line 30-50 min after CO2 washout in both groups. In summary, lowering body temperature while maintaining constant ventilation leads to changes in brain pHi and metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of hypothermia on rat brain pHi and phosphate metabolite regulation by 31P-NMR. 260 61

Isolated working rat hearts were subjected to a 3-hour ischemia followed by reperfusion. The defense effects of the heart cooling to 6-7 and 12-15 degrees C were assessed according to the degree of postischemic recovery of hemodynamic (arterial pressure, heart rate, coronary flow, cardiac output) and biochemical (ATP, phosphocreatine, Pi, and lactate content) characteristics and electron microscopic evidence. The energy resources of the myocardium and its cellular structures were effectively preserved during one-hour ischemia at 12-15 degrees C. At 6-7 degrees C, the energy resources of the hearts were better preserved in long-term ischemia, where the functional characteristics were recovered to the same extent as in the 12-15 degrees C hypothermia, but some cell damage was observed. The obtained findings suggested that the temperature of 12-15 degrees C should be the temperature of choice for heart cooling in cardiosurgery.
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PMID:[Prognostic significance of arterial blood pressure levels and the effectiveness of the treatment of arterial hypertension in a non-organized male population 40-59 years of age in Moscow]. 262 77

The metabolic response of the rat liver to flushing and reflushing with Marshall's solution at pH 7.2 or pH 7.8 has been studied by 31P nuclear magnetic resonance spectroscopy. The changes in intracellular pH, inorganic phosphate, ATP and phosphomonoesters have been determined from the 31P spectra. We show that the intracellular pH at any stage of the flushing protocol is largely independent of the pH of the medium when using these solutions. However, we demonstrate that there are differences between the efficiency of the two solutions in respect of the rates of hydrolysis of ATP and accumulation of phosphomonoesters. There were also differences in the response of the livers upon reflushing--those livers reflushed at pH 7.2 resynthesized ATP from a lower initial concentration to achieve ATP concentrations similar to those restored in livers reflushed at pH 7.8. These trends were mirrored in the responses of the phosphomonoester peaks (which contain a contribution from AMP). We conclude that short-term control of liver metabolism during hypothermia is possible by use of solutions of different pH, but that for longer-term storage, other approaches may be necessary to maintain metabolic integrity.
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PMID:Biochemical consequences of reflushing hypothermically-stored liver with fresh cold perfusate. Studies on rat liver using 31P NMR spectroscopy. 264 Dec 99


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