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

The body temperature of rats has been studied in a cold environment. In this setting, bromocriptine induced hypothermia. This fall in core temperature was inhibited by pimozide. It was concluded that bromocriptine has a dopamine-like action in areas of the brain concerned with the control of body temperature, as has previously been shown for apomorphine and amphetamine.
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PMID:Hypothermic action of bromocriptine. 113 73

Metabolic rates and rectal temperatures were continuously monitored for humans immersed in cold ocean water (4.6--18.2 degrees C) under stimulated accident conditions. The subjects wore only light clothing and a kapok lifejacket while either holding-still or swimming. While holding-still, metabolic heat production (Hm,kcal-min--1) was inversely related to water temperature (Tw, degrees C) according to the equation Hm equals 4.19 minus-0.117 Tw. This temperature response pattern is shown to be similar to that for exposure to air of the same temperature when air velocity is just over 5 m.p.h. (2.24 m/s). The thermogenic response was one-third efficient in balancing the calculated heat loss in cold water, resulting in hypothermia at a rectal temperature cooling rate (C, degrees C-min--1) dependent on water temperature (Tw, degrees C) according to the relation C equal 0.0785 - 0.0034Tw. Although swimming increased heat production to 2.5 times that of holding-still at 10.5 degrees C water temperature, cooling rate was 35% greater while swimming. A prediction equation for survival time (ts, min) of persons accidentally immersed in cold water (Tw, degrees C) has the form ts equal 15 + 7.2/(0.0785-0.0034Tw), based on the findings of this study, and it is compared to pre-existing models.
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PMID:Thermal balance and survival time prediction of man in cold water. 113 45

Five different behaviors of man while in cold ocean water (9-10 degrees C) were assessed for their effect on rate of progress into hypothermia. With subjects wearing lifejackets, two thermally protective behaviors were studied which reduce exposure to the water of areas of body surface with high relative heat loss potential. One was huddling of three persons and the other a self-huddle behavior (HELP or Heat Escape Lessening Posture). These two behaviors resulted in significant reductions of rectal temperature cooling rate of 66 per cent and 69 per cent, respectively, of that of a control behavior. With no flotation available, two survival swimming behaviors (treading water and drownproofing) were shown to result in significant increases in cooling rate to 134 per cent and 182 per cent, respectively, of the control behavior. Potential swimming distance of subjects wearing a life-jacket was 0.85 miles in water near 12 degrees C before predicted incapacitation by hypothermia. It was concluded that behavioral variables can be of major importance in determining survival time in cold water through modulation of cooling rate associated with other variables such as fatness, body size, and clothing.
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PMID:Effect of behavioral variables on cooling rate of man in cold water. 114 Nov 20

The tolerance of altitude-acclimatized (18,000 ft 4 wk) and unacclimatized rats to exercise at 5 degrees was determined. Fewer unacclimatized than acclimatized rats became fatigued during 9 hr of exercise in the cold. Normal body temperatures were maintained in both groups during 9 hr in the cold at rest, but after exercise unacclimatized rats became mildly hypothermic (body temperature 35 degrees) and acclimatized rats severely hypothermic (body temperature 27.9 degrees). Polycythemia (hematocrit 69) was produced during the altitude acclimatization. Altitude-acclimatized rats developed more severe hypoglycemia and lower liver glycogen and serum lactic acid concentrations after exercise than did controls. No pathological changes were found in resting altitude-acclimatized rats, but after exercise in the cold, a higher percentage of acclimatized than unacclimatized rats developed focal myocardial necrosis within 4 days. Reduced exercise tolerance is attributed to severe hypothermia with associated decreased metabolism, polycythemia, hypoglycemia, and a higher incidence of pathological changes in the cardiac and striated muscles.
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PMID:Tolerance of altitude-acclimatized rats to exercise in the cold. 114 56

Seveteen infants (2 1/2 to 28 months old) were continuously monitored by six-channel electroencephalography (EEG) during the entire surgical procedure of open-heart repair. They were subjected to surface hypothermia supplemented by cold extracorporeal circulation (ECC) down to an average esophageal temperature of 21 degrees C., to cardiac arrest of 40 minutes average (range 19 to 62 minutes), and to ECC rewarming. Survival time of the EEG was correlated to esophageal temperature at the time of arrest. EEG reappeared an average of 26 minutes (5.30 to 50) after the strat of rewarming ECC and became strictly continuous after 44 minutes. Reappearance latency was well correlated with the duration of arrest. Potential normalization was oberved in 13 infants, but true normalization was observed in only 2 infants during the 90 to 120 minute period after ECC. By judging the EEG and by comparing this series with two previous series of moderate and deeper hypothermia in older patients, we concluded that the immediate tolerance of the brain to deep hypothermia and circulatory arrest seems no different in infants and in older patients.
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PMID:A study of the electroencephalogram during surgery with deep hypothermia and circulatory arrest in infants. 115 15

An earlier study reported an increased resistance of chickens to an acute lethal heating episode (43 degrees C. and 45% relative humidity) during aflatoxicosis. This varies from other stresses investigated which interact with aflatoxicosis to make chickens more sensitive to the stress factor. The effects of graded doses of dietary aflatoxin (0, 0.625, 2.5, 5.0, and 10.0 mug./g.) on the body temperature, on body fat, on the serum glucose, and on the effect of varying the severity of the heat stress were measured. Both serum glucose and total body fat were decreased significantly (P less than 0.05) by doses of 2.5 mug./g. and above. Cloacal temperature was decreased slightly but significantly (P less than 0.05) in chickens fed 5 or 10 mug./g. for 12 days or longer. The mean survival time of birds exposed to a heat stress of 40 degrees C. and 45% relative humidity did not vary with the dose of aflatoxin while a milder stress of 37 degrees C. and 45% relative humidity caused chickens fed aflatoxin at 2.5 mug./g. or above to show decreased survival times (P less than 0.05) in comparison to the controls. These data can be rationalized by assuming that the lessened burden of body fat during aflatoxicosis accounts for the increased survival time in a severe (43 degrees C. and 45% relative humidity) heat stress but that other parameters related to physiological stress play a dominant role during a less severe but more prolonged heating episode. It seems likely that the hypoglycemia, hypothermia, and lessened body fat also account for the previously reported increased sensitivity to a lethal cold exposure during aflatoxicosis.
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PMID:Interaction of aflatoxicosis with heat stress. 116 99

The administration of d-amphetamine (15 mg/kg, i.p.) to rats causes stereotypy, hypothermia among animals placed in a cold environment, and paradoxical behavioral thermoregulation (i.e., animals in a cold environment choose not to place themselves under the beam emitted by a heat lamp). These effects are blocked in animals lesioned unilaterally in the mesolimbic dopaminergic projections to the olfactory tubercule and nucleus accumbens. In contrast, a unilateral lesion destroying the nigro-striatal projections within the caudate nucleus blocks none of these responses, and actually potentiates the induction of stereotypy by d-amphetamine. Both lesions cause the animal to exhibit rotational behavior in response to the subsequent administration of d-amphetamine. These observations suggest that the mesolimbic dopaminergic projections mediate some of the behavioral and visceral effects of d-amphetamine.
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PMID:Dopaminergic neurons in the nigro-striatal and mesolimbic pathways: mediation of specific effects of D-amphetamine. 116 75

Right heart catheterisation was undertaken in six patients with accidental deep hypothermia. Studies were carried out before and after rapid blood volume expansion, with and without Isoproterenol infusion, and were repeated at normal body temperatures. The initial haemodynamic pattern indicated a marked hypovolemia with a simultaneous decrease of both cardiac output and ventricular filling pressures, and a decreased measured total blood volume. Rapid correction of the hypovolemia revealed cardiac insufficiency, in part due to the persisting bradycardia. Left ventricular function was depressed in patients with prolonged cold exposure and normal in patients with short exposure. These abnormalities disappeared after Isoproterenol infusion during hypothermia, and spontaneously after return to normothermia. No imbalance existed between the decreased cardiac output and oxygen uptake in hypothermia, arterio-venous oxygen difference being within normal limits.
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PMID:Haemodynamic study of prolonged deep accidental hypothermia. 118 54

In order to assess the long-term effects of cardiopulmonary bypass (CPB) in combination with pupular methods of myocardial protection, 37 dogs were placed on CPB for 100 minutes with the use of a bubble oxygenator without hemodilution. A separate group (I) of eight normal dogs served as a control for assessment of hemodynamic changes. The operative groups were as follows: II, continuous coronary perfusion with an empty, beating heart for 60 minutes at 35 degrees C.; III, hypothermic anoxic arrest (aortic occlusion) for 60 minutes with topical cold saline lavage (4 degrees C.); IV, anoxic arrest for 60 minutes at 35 degrees C. Subgroups of Groups III and IV received intracoronary perfusion with Ringer's lactate or Sacks' solution during aortic occlusion and were compared with those animals receiving no perfusion. Survival in Groups II and III was significantly better than in Group IV (82 and 92 per cent vs. 45 per cent). Coronary perfusion with Ringer's lactate or Sack's solution did not influence survival. The 23 survivors from all groups underwent left heart catheterization and LV cineangiography 5 months after operation. All three operative groups had significant elevation of LVEDP and depression of maximum developed dp/dt when compared with normal dogs. Ejection fraction was significantly depressed in Groups III and IV, and there was evidence of left ventricular hypokinesia and/or akinesia in all three operative groups. Differences in function between Groups II, III, and IV were not significant. The use of intracoronary solutions during anoxic arrest did not significantly influence these functional alterations. Evidence of subendocardial fibrosis was found in each of the operative groups, with the most marked changes found in the normothermic arrest group. Moderate fibrosis was present, however, in some survivors in both the continuous coronary perfusion and topical hypothermic arrest groups. These data indicate that although survival is greatly enhanced when coronary artery perfusion or topical hypothermia is used, neither method prevents chronic deterioration in ventricular function nor the development of subendocardial fibrosis.
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PMID:Long-term morphologic and hemodynamic evaluation of the left ventricle after cardiopulmonary bypass. A comparison of normothermic anoxic arrest, coronary artery perfusion, and profound topical cardiac hypothermia. 118 84

Rectal temperatures of salicylate-treated and untreated rats were observed in 21-23 degrees C air at 1, 3, 6, and 8 ATA, in 21-23 degrees C helium at 1 and 6 ATA, and in 1 ATA thermal neutral air (28 degrees C). Significant dose-related temperature decreases occurred in 21-23 degrees C 1 ATA air with 180 and 300 mg/kg of salicylate; 60 mg/kg had no effect. However, in thermal neutral air, 300 mg/kg significantly elevated temperatures. Hyperbaric air and helium had temperature-lowering effects which were correlated with thermal properties of these environments, and in them the hypothermic effects of salicylate were similar to those in 1 ATA air, the total temperature decreases being the sum of the salicylate hypothermia and that caused by the hyperbaric air or helium. These additive temperature effects are unlike previously reported results in which the temperature lowering effects of 5 degrees C cold exposure and salicylate together were greater than the sum of the two individual effects.
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PMID:Salicylate hypothermia in rats exposed to hyperbaric air and helium. 119 49


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