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

Elevating serotonin (5-HT) contents in brain with 5-hydroxytryptophan (5-HTP) reduced rectal temperature (Tre) in rabbits after peripheral decarboxylase inhibition with the aromatic-L-amino-acid decarboxylase inhibitor R04-4602 at two ambient temperatures (Ta), 2 and 22 degrees C. The hypothermia was brought about by both an increase in respiratory evaporative heat loss (Eres) and a decrease in metabolic rate (MR) in the cold. At a Ta of 22 degrees C, the hypothermia was achieved solely due to an increase in heat loss. Depleting brain contents of 5-HT with intraventricular, 5,7-dihydroxytryptamine (5,7-DHT) produced an increased Eres and ear blood flow even at Ta of 2 degrees C. Also, MR increased at all but the Ta of 32 degrees C. However, depleting the central and peripheral contents of 5-HT with p-chlorophenylalanine (pCPA) produced lower MR accompanied by lower Eres in the cold compared to the untreated control. Both groups of pCPA-treated and 5,7-DHT-treated animals maintained their Tre within normal limits. The data suggest that changes in 5-HT content in brain affects the MR of rabbits in the cold. Elevating brain content of 5-HT tends to depress the MR response to cold, while depleting brain content of 5-HT tends to enhance the MR response to cold.
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PMID:Changes in serotonin contents in brain affect metabolic heat production of rabbits in cold. 30 17

Both coronary perfusion and hypothermic cardioplegia are widely used methods of myocardial protection during aortic valve replacement. A theoretical objection to coronary perfusion is that it is not synchronized with cardiac contractions. Accordingly, a special pump was designed to provide perfusion at a constant range of pressure. Twenty dogs were studied during 4 hours of bypass. In six dogs no manipulations were carried out and hearts were allowed to beat in a nonworking state. Seven dogs underwent 2 hours of aortic cross-clamping and constant-pressure aortic root perfusion. Seven dogs underwent 2 hours of uninterrupted aortic occlusion with myocardial protection being maintained by cold potassium-induced arrest, Contractility did not change significantly in any of the three groups. All animals demonstrated significant hyperemia after bypass but normal endocardial/epicardial flow ratios. Although compliance deteriorated in all groups, the most striking changes were seen following 4 hours of bypass alone or constant-pressure aortic root perfusion. Hypothermic potassium arrest, in contrast, provided a slightly greater degree of myocardial protection, perhaps both by limiting the degree of ischemic injury directly and by excluding the heart from the circulating blood and the pump oxygenator system.
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PMID:Constant-pressure aortic root perfusion versus cardioplegia and hypothermia. Comparison of methods of myocardial protection. 31 94

The authors analyze the results of 220 applications of internal cold cardioplegia in 136 patients with ischaemic heart disease, treated surgically by aortocoronary bypass. The operation was performed under neuroleptanalgesia and artificial circulation with hypothermia (27.9 +/- 0.2 degrees C) and haemodilution (24.9 +/- 0.3%). On the basis of clinical examination, electron microscopy of the myocardial ultrastructure, and investigation of the myocardial metabolism (contents of glucose, lactate, pyruvate, free fatty acids, catecholamines, and oxygen in arterial and venous blood flowing out of the myocardium), they come to the conclusion that internal cold cardioplegia efficiently protects the myocardium during aortocoronary bypass and secures favourable conditions for the development of anastomoses between coronary arteries and venous shunts.
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PMID:Myocardial protection during aortocoronary bypass. 31 79

Sixteen cases of neonatal cold injury, five of them fatal, were seen in the winter of 1974-75. The affected infants, who weighed from 2.5 to 3 kg. had developed symptoms when the ambient termperature was below 10 C. Few of them were referred as cases of hypothermia. Refusal to eat was the most common complaint and less often edema and/or apathy. No correlation was found between death and ethnic origin, sex, duration of illness or minimum temperature. Admission weight, however, tended to be lower in the infants who died. The consistent finding of thrombocytopenia and the suspected bleeding phenomena suggested that disseminated intravascular coagulation may have been a factor in the unfavorable outcome of some of the cases. Evidence supporting such a hypothesis and proposals for the prevention. Diagnosis and treatment of neonatal cold injury are presented.
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PMID:Cold injury in early infancy. 32 24

The functional outcome after the transplantation of 97 cadaveric kidneys stored up to 25 hours with simple hypothermia was analysed in relation to age of donor, extent of pre-agonal kidney damage, the length of warm, cold and standardised ischaemic times and the presence of multiple renal arteries. Analysis of various factors showed that the most important for function after transplantation were pre-agonal anoxic damage and the ratio of the cold/warm ischaemia time. Based on that observation, a diagram has been proposed which allows calculation of the safe cold storage time after retrieval of the kidney.
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PMID:Factors responsible for the functional pattern of cadaveric kidneys stored up to 25 hours before transplantation. 39 14

There are 2 competing methods for cooling the kidney in situ during surgical ischemia: from without by applying ice to the renal surface and from within by perfusing the renal artery. The latter procedure is said to be superior in protecting renal function. Herein the protective effect on renal function of both methods are compared. Pigs of 15--25 kg weight underwent nephrectomy on one side. The remaining kidney was subjected to cold ischemia during 90 minutes while perfusion- or surface cooling was performed. For perfusion cooling the aorta was punctured and the catheter introduced into the renal artery. The perfusing liquid consisted of a physiologic electrolyt solution (Ringer-Lactate) with heparin kept at a temperature of 3--5 degrees C. The initial perfusion lasted 10 minutes and resulted in a median renal core temperature of 23 degrees C. Then the kidney was put on a cooling pad and every 15 minutes again perfused for one minute. For surface cooling sterile melting ice made of glucose solution 5% was applied directly to the kidney. The renal core temperature could be kept at 15--20 degrees C. The two methods of hypothermia were judged by comparing the serum creatinine levels and the I131-hippuran clearances one month after surgery. There was no difference whatever as analysed by the t-test. Hypothermia by applying ice to the renal surface therefore proved to be equivalent to hypothermia by perfusion. Moreover it is much simpler.
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PMID:[Renal hypothermia in situ. Comparison between surface and perfusion cooling concerning renal function in pigs (author's transl)]. 41 41

Heart surgery with hypothermic cardioplegia during normothermic bypass is sometimes complicated by rewarming of the myocardium caused by collateral flow of arterial blood. This problem is particularly evident in surgery of congenital malformations. The present work is a comparative study in dogs on 3 methods of avoiding the rewarming problem. In the first group, the heart was kept cold and the warm blood was drained off from the left atrium. In the second group, total body hypothermia to the level desired was used and in the third group, normothermic cardioplegia was induced (Cardioplegin) in normothermic animals. In the two latter groups, the undesired temperature gradient between heart and body was eliminated. Evaluation of the differences was made by means of ventricular function determinations. Local, hypothermic cardioplegia showed the best postoperative function (69%) followed by the total body cooling which was fully acceptable (41%). Normothermic cardioplegia after the same duration of arrest showed a too low myocardial performance (20%).
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PMID:Myocardial protection during heart surgery. An experimental evaluation of normothermic and hypothermic cardioplegia. 43 73

Studies both in vivo and in vitro implicate glucocorticoids in various aspects of thermogenesis and prevention of heat loss. Many or most of these effects are probably permissive. Adrenalectomized, cold-exposed rats require glucocorticoids for catecholamine-mediated mobilization of free fatty acids, for shivering responses, and for vasoconstriction and piloerection. Glucocorticoid pretreatment of hypothermic hamsters results in a physiological state more similar bioenergetically to hibernation than to hypothermia. For example, such hamsters can arouse to normothermia from a body temperature of 8 C in a 7--8 C cold room. Lipolytic, gluconeogenic, glycogenolic, and pressor actions resulting from several hormone interactions that require glucocorticoids for optimum responses may account for the enhanced thermogenic ability shown by glucocorticoid-pretreated hamsters. Glucocorticoid treatment also results in enhanced blood and liver carbohydrate levels during hypothermia, a condition similar to that occurring in naturally hibernating animals as opposed to the depleted carbohydrate reserves generally seen in hypothermic animals.
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PMID:The function of glucocorticoids in thermogenesis. 44 69

A model of the thermal conditions of the heart during ischemic arrest was used to study the efficiency of Shumway's technique of topical hypothermia. Cooling was improved by increasing the flow of cold saline to 350 ml per minute, reducing the saline temperature, lifting the posterior left ventricular wall away from the pericardium, and irrigating the left ventricular cavity. Perfusing the coronary circulation with cold fluid cooled the heart eight times faster than did surface irrigations by Shumway's technique.
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PMID:III. Local cardiac hypothermia: experimental comparison of Shumway's technique and perfusion cooling. 45 54

A physical model for the study of local cardiac hypothermia was developed using excised animal hearts. The validity of the model was established by showing close similarity between cooling curves of dog hearts in vivo and in the model. The model was then used to compare the cooling rates of three groups of excised hearts using cold saline irrigation. Groups 1, 2, and 3 had mean left ventricular weights of 166, 379, and 1,429 gm, respectively, and mean left ventricular wall thicknesses of 1.5, 2.0, and 3.1 cm, respectively. For the same 10 degrees C temperature fall, Group 1 took 25 +/- 2.8 minutes, Group 2 took 54 +/- 9.2 minutes, and Group 3 took 117 +/- 21 minutes. To avoid slow cooling and consequent ischemic damage in the hypertrophic ventricle, it may be desirable to initiate cooling using coronary perfusion with cold blood or cold cardioplegic solutions.
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PMID:I. Development of an in vitro model of myocardial cooling: a study of the effect of cardiac size on cooling rate. 45 60


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