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

Oxygenation of crystalloid cardioplegic solutions is beneficial, yet bicarbonate-containing solutions equilibrated with 100% oxygen become highly alkaline as carbon dioxide is released. In the isolated perfused rat heart fitted with an intraventricular balloon, we recently observed a sustained contraction related to infusion of cardioplegic solution. In the same model, to record these contractions, we studied myocardial preservation by multidose bicarbonate-containing cardioplegic solutions in which first the calcium content and then the pH was varied. An acalcemic cardioplegic solution (Group 1) and the same solution with calcium provided by adding calcium chloride (Group 2) or blood (Group 3) were equilibrated with 100% oxygen. Ionized calcium concentrations were 0, 0.10 +/- 0.06, and 0.11 +/- 0.07 mmol/L and pH values were 8.74 +/- 0.07, 8.54 +/- 0.08, and 8.40 +/- 0.07, all highly alkaline. Hearts were arrested for 2 hours at 8 degrees +/- 2.5 degrees C and reperfused for 1 hour at 37 degrees C. At end-arrest, myocardial adenosine triphosphate was depleted in all three groups, significantly in Groups 2 and 3. In Group 1 the calcium paradox developed upon reperfusion, with contracture (left ventricular end-diastolic pressure = 60 +/- 7 mm Hg), creatine kinase release up to 620 +/- 134 U/L, a profound further decrease in adenosine triphosphate to 1.9 +/- 1.7 nmol/mg dry weight, and either greatly impaired or no functional recovery (17% +/- 10% of prearrest developed pressure). Three hearts in this group released creatine kinase during arrest and did not resume beating during reperfusion. In Groups 2 and 3, the calcium paradox did not occur; functional recovery was 61% +/- 4% and 71% +/- 9% at 5 minutes of reperfusion. In two additional groups (4 and 5), the pH of the acalcemic cardioplegic solution was decreased by equilibration with 2% and 5% carbon dioxide in oxygen to 7.53 +/- 0.03 and 7.11 +/- 0.02. Contractions during arrest were smaller than in Groups 1, 2, and 3; adenosine triphosphate was maintained during arrest; functional recovery was 101% +/- 3% and 96% +/- 4% at 5 minutes of reperfusion. We conclude that acalcemic solutions with carbon dioxide are superior to highly alkaline calcium-containing solutions. If oxygenation of cardioplegic solutions, of proved value, causes severe alkalinity, then calcium paradox may result even with hypothermia. This hazard is prevented by adding calcium or blood to the solution or carbon dioxide to the oxygen used for equilibration.
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PMID:Oxygenation of cardioplegic solutions. Potential for the calcium paradox. 311 49

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

Rat embryos explanted at head fold stage were stored under various levels of hypothermia prior to culture. The storage media were Hanks' Balanced Salt Solution (BSS), 50% rat serum with 50% Dulbecco's Modification of Eagle's Medium (standard medium), or 100% rat serum. The media were gassed with 5% O2/5% CO2/90% N2 or 20% O2/5% CO2/75% N2. Subsequent development of embryos after storage at temperatures between 10 degrees C and 30 degrees C for 5 hr in Hanks' BSS, or for 5-10 hr in standard medium or serum, was similar to that of controls. Some embryos developed well even after storage for 48 hr in standard medium. Development was poorer after storage at 0 degrees C or 5 degrees C, and after storage at all temperatures in ungassed Hanks' or standard medium (pH greater than 8.0). Differences in oxygen level had little effect. For routine explantation at room temperature in (ungassed) phosphate-buffered saline solutions such as Hanks', it is recommended that the delay before transferring the embryos to the culture incubator not exceed 2-3 hr.
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PMID:Effects of temporary cooling, and of different explantation and storage conditions, on the subsequent development of post-implantation rat embryos in vitro. 323 94

The course and outcome in terms of cerebral morbidity and hospital mortality in 79 severely carbon monoxide poisoned patients admitted to the intensive care unit during a period of 15 years is presented. Treatment consisted of administration of pure oxygen. Ninety-four per cent of the patients were artificially hyperventilated, and the majority of the patients were also treated with moderate hypothermia, steroid hormones and diuretics. Hospital mortality was 30%, and 14% of the patients were discharged after long-term hospital treatment with signs of brain damage. Due to the unpredictable cerebral course after the acute incident long-term follow-up is recommended.
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PMID:Acute carbon monoxide poisoning. 339 78

Protection of the brain and spinal cord against ischemia is a goal of vast clinical importance. One approach to this objective is to reduce the tissue's functional activity in order to preserve energy for the metabolic processes that are essential to viability. Experiments to explore ways of reducing function-related energy demands were performed on isolated rabbit retina, a well-characterized model of organized adult mammalian central nervous system (CNS) tissue. The retina was maintained in a nearly physiological state in a miniature "heart-lung" apparatus. Energy metabolism (oxygen consumption and glycolysis) and electrophysiological function (determined by electroretinogram) of the in vitro retina were monitored, and their responses to a series of agents that may reduce energy requirements were determined. Large reversible reductions in O2 consumption, glycolysis, and electrophysiological function were seen in response to mild hypothermia (-3 degrees to -6 degrees C), phenytoin (Dilantin, 100 to 200 mg/kg), chlordiazepoxide (Librium, 200 microM), lithium (1 to 4 mM), Mg++ (6 to 20 mM), strophanthidin (0.15 to 0.25 microM), CO2 (25% to 30%), 2-amino-5-phosphonovaleric acid (APV, 500 microM), amiloride (1 mM), and dantrolene (1 mM). One retina was exposed simultaneously to a combination of six of these agents, which reduced its oxidative and glycolytic metabolism to less than 50% of the control level. The retina recovered metabolic and electrophysiological function after a 2 1/2-hour exposure period. Other agents tested (diphenhydramine, midazolam, nifedipine, nimodipine, and quercetin) had effects on energy metabolism and electrophysiological function that were poorly reversible. Surprisingly little effect was seen in response to general anesthetic agents (thiopental and Althesin) and other CNS depressants (chlorpromazine, ethanol, lidocaine, paraldehyde, valproic acid, and baclofen). The presumed mechanisms through which these agents reduce cellular energy requirements, as well as their potential roles in the treatment of CNS ischemia, are discussed.
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PMID:Reduction of cellular energy requirements. Screening for agents that may protect against CNS ischemia. 341 90

A boy referred at the age of 4 years because of obesity and under observation for 16 years, was found to be suffering from a hypothalamic syndrome of unknown origin characterized by progressive obesity, polyphagia, deficiency of growth and thyroid hormone, hyperprolactinemia, hypodipsia, hypernatremia and hyperosmolality without diabetes insipidus. At ages 11 and 16 there were 3 day episodes of spontaneous muscular weakness, hypersomnolence and hypothermia associated with central sleep apnea and severe bradycardia. Subsequently, decreased ventilatory responsiveness to carbon dioxide (CO2) was found as a consequence of blunted neural drive. Therapy with clomipramine HCl (Anafranil Ciba-Geigy) for 6 months led to a normalization of serum sodium levels, pulse rate, ventilatory response to dioxide with no recurrence of the central apnea within 4 following years.
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PMID:Recurrent hypothermia, hypersomnolence, central sleep apnea, hypodipsia, hypernatremia, hypothyroidism, hyperprolactinemia and growth hormone deficiency in a boy--treatment with clomipramine. 346 79

The type and the incidence of complications during treatment with high-frequency jet ventilation were evaluated in 10 critically ill patients with acute respiratory failure. HFJV was used for 2 to 34 days for management of bronchopleural fistulae, tracheal rupture, laryngeal trauma or voluminous lung abscesses. The most significant technical problems observed were disconnection or kinking of the jet catheter, hypothermia and CO2 retention. Insufficient humidification could induce severe complications such as viscous bronchial secretions, desiccation of the tracheobronchial mucosa or total obturation of the endotracheal tube. Psychological tolerance of high-frequency jet ventilation was generally satisfactory but the ventilator noise was sometimes hardly tolerated. Patients could develop a psychological dependence to high-frequency jet ventilation, leading to weaning problems. Solutions are suggested to decrease the incidence and severity of the technical and psychological complications.
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PMID:Technical and psychological complications of high-frequency jet ventilation. 347 1

During progressive hypothermia for cardiac surgery, the need for advanced and comprehensive physiological monitoring systems is even more apparent and vital. A review of the literature on the physiological effects of hypothermia in animals reveals that the "physiological neutrality" intracellularly is achieved at progressively higher pH values as temperature falls, and that this more alkaline acid-base balance is apparently achieved while the total carbon dioxide content of the tissues remains at normothermic (normal body temperature) levels. Based on this, an anesthetic technique was studied, whereby the ventilation was maintained throughout the cooling/surgery/rewarming cycle at normothermic levels. This allowed a progressively more alkaline acid-base environment to be achieved. This technique is discussed in detail, together with information relating to the circulatory changes and complications seen and the degree of acid-base control obtained. The conclusion is drawn that the addition of carbon dioxide to the ventilation gases, of alternatively, a decrease in ventilation as temperature falls, is not only unnecessary, but perhaps also harmful.
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PMID:Hypothermia and acid-base regulation in infants. 354 13

Sudden unexplained death may be seen with treatment of craniovertebral anomalies and surgery of the upper cervical spine. Death is due to sleep-induced apnea, premonitored by periods of confusion, lethargy, and asthenia. There may be associated hypotension, bradycardia, hyponatremia, hypothermia, inappropriate antidiuretic hormone secretion, and difficulty in micturition. The potential for respiratory failure may be predicted if a CO2 response test demonstrates an attenuated or abnormal response. Apnea during sleep may be reversed by arousal or may require ventilatory support for a period of time. The condition is self-limiting, but remains the major life-threatening complication. Both apnea and autonomic dysfunction are treatable and curable with appropriate diagnosis and management.
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PMID:Occult respiratory and autonomic dysfunction in craniovertebral anomalies and upper cervical spinal disease. 375 66

Survival following 3 hr of total circulatory arrest under profound hypothermic conditions was explored in 19 adult mongrel dogs. Thermoregulatory management included combined surface/perfusion hypothermia and azeotrope anesthesia in 95% O2/5% CO2. All animals were resuscitated and survived for at least 12 hr. During the last seven trials (Group II) the following principles were applied: uniform whole-body cooling where differences between rectal, esophageal, and pharyngeal temperatures averaged less than 1 degree C, induction of circulatory arrest at approximately 3 degrees C, constant lung inflation (10-12 cm H2O between 20 degrees C cooling and 20 degrees C rewarming, including the 3-hr arrest period) and ventilation assistance with positive end-expiratory pressure (4 cm H2O) after 20 degrees C rewarming, intraoperative maintenance of colloid osmotic pressure (COP) above 11 mm Hg, replacement of the cooling perfusate with a colloid-rich rewarming prime (COP = 15 mm Hg) and restoration of hemostasis with fresh whole blood transfusions. The application of these principles resulted in the long-term survival of five animals with four survivors displaying no clinically detectable neurological abnormalities. However, two animals developed optic impairment and one animal died from intusseption on the fourth postoperative day. Despite the improved results, it should also be noted that during pilot (Group I) studies (from which the aforementioned principles were derived) fatalities from complications attributed to systemic edema, central nervous system, or pulmonary or coagulation dysfunctions occurred in 9 out of 12 trials. We conclude that whole body protection following 3 hr of total circulatory arrest at a uniform temperature less than 5 degrees C can be successfully accomplished.
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PMID:Whole body protection during three hours of total circulatory arrest: an experimental study. 380 87


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