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

To investigate the oxygen transport capacity of solutions for blood replacement the oxygen solubility coefficients (ml/ml atm) at 37 degrees C of 12 solutions for volume replacement were determined and compared with those of 12 solutions for parenteral nutrition, 4 electrolyte solutions and 5 solutions for osmotherapy. All solutions for volume replacement have lower values for oxygen solubility than human plasma which shows a very constant oxygen solubility value even under extreme conditions. For clinical use of volume replacement solutions it is recommended that the oxygen solubility of the substitute be considered when any of the following conditions presents: a) large amounts are infused (hemodilution), b) isobar of hyperbar oxygen therapy is employed (hyperoxia), c) the body temperature is lowered (hypothermia). This is valid especially in the case of any impairment of the microcirculation.
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PMID:[Oxygen transport by solutions for blood replacement in comparison with other infusion solutions (author's transl)]. 9 98

The content of ammonia, glutamine, dicarboxylic amino acids and GABA was studied in the brain under 1, 2, 4-fold separate and simultaneous effect of hypothermia (19-20 C) and hyperoxia (3 atm.). A two-fold hypothermia of rats is accompanied by a greater increase of ammonia in the brain than a three-fold one. The content of glutamine under two-fold cooling is unchanged and under three-fold cooling it is twice as low as compared to its content in the brain of the control rats. The content of glutamic acid decreased after two-fold hypothermia is almost unchanged by the third seance of hypothermia. The repeated actions of hyperoxia also cause a considerable increase in the ammonia content but the dynamics of changes in the content of the nitrogenous metabolic products is contary to that in animals subjected to repeated seances of hypothermia. A simultaneous combined action of hypothermia and hyperoxia produces no additive effect on the system ammonia-glutaminic acid.
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PMID:[Effect of hypothermia and hyperoxia on the ammonia-glutamic acid system in the brain of rats]. 96 Feb 39

1. The role of chemoreceptors in the control of heart rate and behaviour during diving activity in the tufted duck was investigated in two ways. In a closed-loop experiment, ducks were exposed to ambient gas mixtures of varied composition during diving activity in an indoor tank. Characteristics of diving behaviour, heart rate and deep body temperature were monitored under hypoxic, hyperoxic and hypercapnic conditions and compared with those in air. Secondly, in an open-loop experiment the role of the carotid body (CB) chemoreceptors in the control of the responses to altered inspired gas composition and in the cardiac responses to extended and enclosed dives (Stephenson, Butler & Woakes, 1986) was investigated by chronic bilateral denervation of these receptors. 2. Heart rate during submersion was unaffected by inspired gas composition in control (data from intact and sham-operated ducks combined) and CB-denervated ducks, though diving behaviour was significantly modified in both groups of animals in response to altered inspired gas composition. Hypoxia and hypercapnia resulted in an increase in the proportion of total diving time spent breathing at the surface. The main effect of hypoxia (9-10% O2) was to reduce dive duration in control ducks and this effect was almost completely abolished after CB denervation. Hypercapnia (5-6% CO2) reduced dive duration less markedly than hypoxia but it greatly increased the duration of the inter-dive interval, effects which were not significantly influenced by CB denervation. Hyperoxia (40-45% O2) had very little effect on either behaviour or heart rate during diving, although deep body temperature was significantly elevated in this gas mixture during diving activity. There was also a less marked, but nevertheless significant, apparent hyperthermia during diving activity in air on an indoor tank but not on an outdoor pond. Conversely, there was a significant apparent hypothermia during diving activity under hypoxic conditions. 3. The CB chemoreceptors were shown to play a role in cardiac control during diving under certain circumstances. The duration of pre-dive tachycardia was significantly increased in hypoxia and this increase was abolished after CB denervation. The rate of development of bradycardia during extended and enclosed dives was slowed following CB denervation, though the initiation of the responses in extended and enclosed dives and the eventual attainment of sub-resting heart rates in enclosed dives were not prevented, indicating that other, as yet unidentified, sensory inputs are involved in cardiac control under these conditions.
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PMID:Chemoreceptor control of heart rate and behaviour during diving in the tufted duck (Aythya fuligula). 313 33

The development of osteonecrosis after exposure to altered air pressures is consistent with cellular injury brought about by active oxygen species. The syndrome is considered to arise as a result of an unusual combination of circumstances in which hyperoxia itself, together with the additive responses of the endocrine system to hyperoxia, hypothermia and exertion, each appear to play a part; the net result is thought to increase the mitochondrial generation of superoxide. It is suggested that effective prophylaxis may be possible primarily by establishing a nutritional status that is adequate to ensure that the functional activities of radical-scavenging systems are not hampered by deficiencies either of essential trace elements or of vitamin E. Pharmacological pretreatments designed both to decrease excessive levels of superoxide through increased catalysis of anionic dismutation and to attenuate enzyme-dependent peroxidation may provide an additional line of defence.
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PMID:Dysbaric osteonecrosis (caisson disease of bone): are active oxygen species and the endocrine system responsible, and can control of the production of free radicals and their reaction products confer protection? 333 53

White Leghorn chicken eggs were exposed to either 60% O2 or room air (21% O2) for the first 19 days of incubation. Chicks that hatched from these eggs were then tested in discrimination learning tasks in which keypecking was autoshaped to colored lights that were paired with either access to food (Experiment 1) or heat (Experiment 2). Chronic prenatal exposure to 60% O2 reduced hatchability but did not affect mean hatching time. Although previous research has shown that hyperoxic treatment accelerates growth in chick embryos until the 18th day of incubation, experimental chicks weighed either the same (Experiment 1) or less (Experiment 2) than controls at hatching. Prenatal exposure to hyperoxia depressed rate of acquisition, but not final performance level in both discrimination tasks. The initial performance deficit appeared to reflect a temporary depression of activity or arousal, possibly due to a relatively greater hypothermia in experimental chicks. This general pattern of results was attributed to premature depletion of essential nutrients within the egg as a result of oxygen-induced growth acceleration.
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PMID:Autoshaped discrimination learning in chicks incubated under normobaric hyperoxia. 371 63

Yellow staining of central nervous system (CNS) nuclei occurs in the brains of some neonates, despite low levels of serum bilirubin. Two conditions appear to be important in the evolution of this form of kernicterus: prematurity and asphyxia. In a seven year retrospective study of a large neonatal autopsy population, 102 cases had kernicterus as indicated by selective macroscopic yellow staining and microscopic damage within specific CNS nuclei. Neuropathological study disclosed minor variations and numerous similarities in the manifestations of kernicterus in the asphyctic premature neonate with low levels of serum bilirubin, as compared to kernicterus in the full-term neonate with high levels of serum bilirubin. Acidosis, hypoxia, hyperoxia, hypothermia and sepsis have been considered significant risk factors, but recent comparative clinical studies have not defined predictive indices. Analysis of this disorder is difficult because of the concurrence of other complications of asphyxia and its pathological correlates in premature infants. Diagnostic difficulties are also compounded by variations in the definitions of kernicterus as used by different investigators.
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PMID:The neuropathology of kernicterus in the premature neonate: diagnostic problems. 669 27

Knowledge of the interrelation of the central nervous system-respiratory axis is crucial to the management of patients with head injuries with or without concomitant pulmonary-thoracic problems. Damage to the central nervous system (CNS) can result in unexplained hypoxemia, noncardiac pulmonary edema, altered patterns of respiration, and an increased risk of aspiration. The damaged thorax and lung can contribute to brain ischemia and rises in intracranial pressure. The treatment of one end of the CNS-respiratory axis is not without effect on the other end of the continuum. Corticosteroids, diuretics, mannitol, iatrogenic hyperventilation, barbiturates, and vasopressors are used in the management of patients with head trauma, but may have an impact on oxygenation and ventilation. When positive end expiratory pressure is used in the management of a pulmonary process, it should be optimized and used with caution while monitoring for its effect on intracranial pressure. Pulmonary toilet, while remaining a necessity, must be performed in a manner so as to minimize potential negative effects on the brain. Hyperoxia and hypothermia should be avoided. Mechanical ventilation should be used as dictated by the desired PaCO2 and not as a mandatory adjunct to endotracheal intubation.
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PMID:Pulmonary effects of head trauma. 679 86

The rat erythrocytes' Na, K-ATPase activity was found to drop under the effects of five various stresses: immobilisation, hypothermia, hyperoxia, physical strain, and physical strain against the background of fasting. An endogenous digoxin-like inhibiting agent(s) acting on the Na, K-ATPase seems to appear in the blood plasma of the animals under stress. The suggestion is corroborated by the fact that albumin-less supernatants of the stressed rats' blood plasma are able to inhibit the Na, K-ATPase in the erythrocytes of the control animals.
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PMID:[The dynamics and mechanism of changes in the erythrocyte Na, K-ATPase activity of rats under the action of different types of stressors]. 816 17

We tested the hypothesis that hypercapnia will induce behavioral hypothermia in toads and that central chemoreceptors are involved in this response. Animals were tested in an enclosed temperature gradient supplied with different gas mixtures. Fractional inspired CO2 (FICO2) between 0 and 0.05 had no significant effect on selected body temperature, but FICO2 between 0.06 and 0.10 reduced the selected body temperature from U approximately 28 to 18 degrees C. To determine if the hypercapnia-induced hypothermia is mediated by acidification of central chemoreceptors, the pH of the fourth ventricle was kept constant by perfusion with mock cerebrospinal fluid of pH 7.7 or 7.1 (normal and acidic values, respectively). Ventricular perfusion at pH 7.7 under normocapnic conditions had no effect on body temperature. Hypercapnia (FICO2 0.08) failed to induce hypothermia when the fourth ventricle was kept at pH 7.7 and when hyperoxia was present. Acidic ventricular perfusion under normocapnic conditions decreased selected body temperature from 27 to 25 degrees C, a significant drop but much less than that due to hypercapnia producing the same brain pH, suggesting an important role of peripheral chemoreceptors. The physiological significance of behavioral hypothermia and nature of the peripheral stimulus were evaluated by measuring the effect of hypercapnia on arterial oxygen saturation, PO2, and pH at 15 and 25 degrees C. Arterial oxygen saturation was higher at the lower temperature. Increasing FICO2 decreased oxygen saturation at 25 degrees C but not at 15 degrees C. Arterial PO2 increased with increasing inspired CO2. This increase was greater at 15 degrees C than at 25 degrees C. Arterial pH decreased at both temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Role of central chemoreceptors in behavioral thermoregulation of the toad, Bufo marinus. 820 24

Pontine cat is an ectothermic preparation, whose central temperature can artificially be lowered from 36 degrees C to 26 degrees C; this gradual hypothermia is accompanied by a dramatic increase in paradoxical sleep (PS). Two main hypotheses might explain this result: executive systems of PS might be switched on gradually by cold-sensitive thermodetectors, whereas inhibitory monoaminergic mechanisms appear to be warm-sensitive. On the other hand, energy saving mechanisms peculiar to hypothermia might promote PS appearance. Indeed, in normal animals, PS is selectively suppressed both by hyperthermia and hypoxia. The inhibitory effect of hypoxia might explain why hypothermia, which protects the brain against hypoxic alterations, might facilitate PS. If this last hypothesis is correct, the putative increase in cerebral oxygen supply might increase PS. For this reason, we submitted eight pontine carotid-deafferented cats, kept at the same central temperature (34 +/- 0.5 degrees C: temperature clamp) to periodic hyperoxia (PaO2 = 58 +/- 7 kPa) or room air (PaO2 = 17 +/- 2 kPa) alternatively during 4- or 12-h periods. Hyperoxia induced an 85% increase in PS, mainly due to an increase in PS rhythm (PS cycle duration was 65 +/- 4 min in normoxia and 45 +/- 4 min in hyperoxia, p<0.0001). In five animals, after hyperoxia, PS cycle returned gradually back to control values in 4 to 12 h. These findings show that PS is exquisitely sensitive to conditions that impair oxidative metabolism. The role of cholinergic executive PS systems as putative metabolic-sensitive neurons remains to be established.
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PMID:Hyperoxia increases paradoxical sleep rhythm in the pontine cat. 975 24


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