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

Inhalation rewarming of hypothermic humans with heated, humidified oxygen was compared to rewarming by immersion in a hot bath. In 10 subjects cooled to approximately 35 degrees C core temperature, there was no significant difference in the amount of temperature "afterdrop" with the two rewarming procedures. Inhalation rewarming provided rapid commencement of increase in tympanic and esophageal temperatures, indicating effective rewarming of critical core regions, especially heart and brain. This method of core rewarming avoids the physiological hazards associated with the peripheral vasodilation which accompanies external rewarming. Moverover the simplicity of application of this method suggests its greater use in both first-aid and hospital treatment of accidental hypothermia.
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PMID:Accidental hypothermia: an experimental study of inhalation rewarming. 118 Jul 82

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

Depressed postoperative myocardial performance (low output syndrome) requiring inotropic drugs or balloon counterpulsation is due to subendocardial ischemic damage. Before July, 1972, we needed inotropic drugs in 30 to 52 per cent of 189 patients undergoing coronary revascularization or aortic or mitral valve replacement in whom we used ischemic arrest, profound topical hypothermia, and ventricular fibrillation. The mortality rate ranged from 10 to 17 per cent. Our experimental studies show that morbidity and death in such cases are caused by ischemic injury to the heart resulting from inadequate myocardial protection during bypass. Based on these experimental studies, we have, since July, 1972, employed the following principles clinically: (1) Maintain beating empty heart whenever possible; (2) maintain adequate coronary perfusion pressure (less than 80 mm. Hg); (3) avoid extreme hemodilution; (4) avoid ventricular fibrillation; (5) avoid prolonged hypothermic arrest, limiting ischemic periods to less than 15 minutes; (6) repay myocardial ischemic oxygen debt with total (vented) bypass; and (7) optimize DPTI/TTI (supply/demand ratio) pre- and postoperatively. These principles were followed in 189 consecutive operations, and postoperative inotropic drugs were needed in only 12. The principles were violated in 4 of the 12 patients (6 per cent), and 5 others had identifiable causes of myocardial depression; low output syndrome was unexplained in only 3 patients (1.7 per cent).
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PMID:Depressed postoperative cardiac performance. Prevention by adequate myocardial protection during cardiopulmonary bypass. 118 89

The mechanism of the hypothermia produced in mice by the naturally occurring cannabinoids, delta9-tetrahydrocannabinol, cannabinol, and cannabidiol, was investigated by evaluating the direct effect of these drugs on the oxygen consumption of tissue homogenates and isolated mitochondria. The tissues studied were brain, liver, skeletal muscle, and heart; the mitochondrial preparations were limited to brain and skeletal muscle. The in-vitro studies included a description of the influence of various cannabinoid vehicles containing Tween 80, ethanol, Pluronic F68, and albumin on the oxygen consumption of tissue preparations. Of these vehicles, only albumin was without effect on all tissues. The other vehicles produced diverse responses, including some that were qualitatively different; the data illustrate that the influence of each vehicle on oxygen consumption must be defined for each tissue employed. In spite of the different vehicle effects, delta9-tetrahydrocannabinol generally reduced oxygen consumption of all tissue preparations; however, the vehicles were capable of modifying the dose-effect relationship. The results of all three drugs prepared in Pluronic F68 on brain and skeletal muscle indicated that the cannabinoids generally cause a dose-related depression of oxygen consumption. The findings demonstrate that the cannabinoids can directly decrease oxidative metabolism of tissue and isolated mitochondria and that a marked response occurs in the concentration range of 1 X 10(-5) to 1 X 10(-4) M. Because these concentrations can exist in tissues following the in-vivo administration of delta9-tetrahydrocannabinol, the results suggest that the depressant effect of the cannabinoids on metabolic rate may contribute to the mechanism of the hypothermia produced by the drugs.
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PMID:The influence of delta9-tetrahydrocannabinol, cannabinol and cannabidiol on tissue oxygen consumption. 119 14

Small lesions in the brain stem (including the hypothalamus) of the European hamster were effective with respect to food intake, hibernatory disposition and thermogenic power (oxygen consumption) as well. Hyperphagia was accompanied by depression of hibernation mostly. Moreover, hibernation was hindered by impairment of the thermogenic capacity. Entrance into hibernation depended on the integrity of the middle and caudal hypothalamic areas and the rostral portions of the pons and midbrain. Hyperphagia resulted from destruction of the middle (ventromedial) hypothalamic and caudal hypothalamic areas, including transition structures to the pons. A depression of thermogenesis against cold was observed after destruction of supramammillary and neighbouring mesencephalic areas. Supplementary results: An annual metabolic rhythm characterized by a minimum in december has been established once more. Urethane anesthesia did not abolish cold thermogenesis, despite the development of a slight hypothermia. Poikilothermia resulting from brain stem damage disappeared during a three-day period. Furthermore, diencephalic lesions did not suppress arousal from hibernation significantly.
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PMID:[Effect of brain stem lesions on hibernation of the hamster (Cricetus cricetus L.)]. 119 40

36 dog kidneys were perfused with different perfusion pressures (between 15 and 60 mm Hg) for 72 hrs and then transplanted. Hypothermic human albumin was the perfusion fluid. Kidneys perfused with a flow rate of 0.8 ml/g/min (21 mm Hg mean perfusion pressure) showed the smallest increase in kidney weight and the best function after transplantation. Renal vascular resistance was independent of the level of the perfusion pressure and renal oxygen consumption was independent of the applied flow rate.
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PMID:[Optimum perfusion pressure, renal resistance and oxygen consumption of kidney in hypothermic pulsating perfusion]. 120 22

Isolated perfused working rat hearts were subjected to elective cardiac arrest for 20 or 30 min. Various methods of arrest were studied, either singly or in combination and with or without coronary perfusion. The functional recovery of the heart following the termination of arrest was found to be related to the concentration of ATP and creatine phosphate in the myocardium at the end of the period of arrest. In turn, these concentrations were dependent upon the method used to induce arrest. Normothermic ischemic arrest led to a marked reduction in high energy phosphates and a poor functional recovery. In contrast, coronary perfusion with hypothermic solutions or solutions containing high concentrations of potassium, induced arrest without depleting ATP or creatine phosphate. These procedures conferred considerable protection on the myocardium and thus permitted good recoveries. The energy status and recovery associated with ischemic arrest could be improved by combining the ischemia with hypothermia or potassium arrest. The latter, while increasing recovery significantly, still failed to afford complete protection to the myocardium. Potassium chloride gave greater protection than potassium citrate. When topical hypothermia was combined with ischemia, a time and temperature relationship was demonstrated but effective protection could only be obtained with severe topical hypothermia over a relatively short time period. The results stress the importance of maintaining high energy phosphates during arrest, and this requires the provision of a continuous supply of oxygen and nutrient, which may perhaps be best achieved by ensuring continuous and adequate coronary perfusion.
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PMID:Ischemic damage and metabolism during elective cardiac arrest. 120 80

The advantages of a bloodless field and total cardiac relaxation have popularized the technique of deep hypothermia and total circulatory arrest for the correction of complex congenital cardiac defects in infancy. There is, however, a significant potential for cerebral and pulmonary complications. Presently, the most common technique is that of using a combination of surface cooling and cardiopulmonary bypass cooling and rewarming. Normal neurological development has been claimed with the present technique of hypothermia at 20 degrees C and total circulatory arrest for periods up to an hour; however, there are reports of seizure activity in the early postoperative period. There is also a disturbing incidence of respiratory insufficiency and, occasionally, hemorrhagic pulmonary edema. This study, using growing puppies and subjecting them to deep hypothermia and total circulatory arrest for varying periods of time, disclosed that animals subjected to 60 min of circulatory arrest recovered neurologically; however, there were histological changes of anoxia in the brain. Animals subjected to 30 min of total circulatory arrest were normal neurologically and there was no histological evidence of anoxic damage to brain tissue. Puppies that were continuously on cardiopulmonary bypass had no significant pulmonary changes caused by increasing the inspired oxygen tension in the ventilator; however, striking changes were noted when limited cardiopulmonary bypass was employed for core cooling and total circulatory arrest combined with pulmonary ventilation with 100% oxygen. We conclude from this experimental study that the use of surface cooling and core cooling with subsequent total circulatory arrest at 20 degrees C is a safe procedure, providing the period of time of cardiac arrest is kept around 30 min. We also conclude that the alveolar oxygen tension should be maintained at the lowest level possible during the interval of circulatory arrest to avoid the apparent rapid onset of post-traumatic pulmonary insufficiency.
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PMID:Effect of deep hypothermia, limited cardiopulmonary bypass, and total arrest on growing puppies. 120 92

Changes in rectal and skin temperatures following intraventricular injection of biogenic amines and related substances were investigated in rats. Intraventricular injection of norepinephrine in a small dose (6 mug) produced a slight elevation of rectal temperature, but in larger amounts (25-50 mug) resulted in a dose-dependent hypothermia which was associated with a marked rise of skin temperature. No change was observed in plasma free fatty acid and glucose levels and oxygen consumption after intraventricular injection of norepinephrine (25 mug). Intraventricular injection of imipramine and safrazine produced a slight fall in the rectal temperature. Norepinephrine-induced hypothermia was more pronounced in rats pretreated with safrazine and less in rats pretreated with alpha-methyl-p-tyrosine, as compared with that in controls. Intraventricular injection of 6-hydroxydopamine (0.75-250 mug) brought about a marked dose-dependent hypothermia. The second injection of 6-hydroxydopamine 5 days after the first injection had no effect on the body temperature. Norepinephrine injection 2 days after the second injection of 6-hydroxydopamine produced a more pronounced hypothermia than the change in control rats without pretreatments. Haloperidol did not affect the hypothermia induced by 6-hydroxydopamine. Intraventricular injection of dopamine and L-DOPA showed less effect that norepinephrine had. Intraventricular injection of phenoxybenzamine prior to norepinephrine blocked the hypothermia and skin temperature elevation which are normally observed following norepinephrine injection, while propranolol given in the same way showed less or no effect. Intraventricular injection of phenylephrine produced a dose-dependent hypothermia, whereas no dose-response relationship was obtained by isoproterenol. These results suggest that in the rat the hypothermic effect of norepinephrine injected intraventricularly is mediated by an action of central alpha-receptor. At high and low ambient temperatures hypothermia was similarly observed following intraventricular injection of 5-hydroxytryptamine (25 mug) as at normal room temperature. On the other hand, norepinephrine (25 mug) produced a rise in rectal temperature at high ambient temperature and a marked fall at low ambient temperature. The hypothermic effect of norepinephrine was not different between cold-adapted ones at room temperature. From the results the role of norepinephrine and other biogenic amines in the brain in thermoregulatory processes was discussed.
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PMID:[Role of brain biogenic amines in the central thermoregulatory mechanism of the rat (author's transl)]. 124 80

Because use of the bubble oxygenator during open-heart surgery is associated with complications such as hemolysis, pulmonary insufficiency and oliguria, a membrane oxygenator was used in conjunction with hypothermia in 37 infants. The main features of the oxygenator are gravitational blood flow, oxygenation into an airless, collapsible blood reservoir, low-flow roller pump flow back to the patient, accurate determination of flows and careful use of a heat exchanger. Gas flow (98% oxygen, 2% carbon dioxide) for the unit of 2 m2 is maintained at 3 to 4 1/min. Specific precautions are taken to ensure absence of bubbles. Three prime solutions are used, the final one having an osmolality of 381 mOsmol and containing 129.9 meq of sodium, 3.8 of potassium and 94.0 of chloride and 2001 mg/dl of glucose. Six patients died, but none of the deaths could be directly related to the use of the oxygenator. Respiratory complications were minimal, as were other complications. The technique is reliable in oxygenating blood in an tracorporeal circulation, but further familiarity with the membrane oxygenator for use in open-heart surgery in infants is desirable before firm conclusions can be drawn as to its value.
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PMID:Use of a membrane oxygenator for open-heart surgery in infants. 126 May 50


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