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

Cerebral ischemia produces a disruption of calcium homeostasis in neurons. This may explain the extreme sensitivity of these cells to ischemic insult. Prolonged increases in calcium levels may produce irreversible damage to the cell by altering important calcium-dependent enzyme systems such as calcium/calmodulin-dependent protein kinase II. Five minutes of acute forebrain ischemia in the gerbil produced a significant decrease in calcium/calmodulin-dependent protein kinase II activity as early as 10 seconds postischemia and persisting up to 7 days after insult. Because hypothermia protects against ischemia-induced cell death in the gerbil, we examined the effect of ischemia on cell death and calcium/calmodulin-dependent protein kinase II at different intracerebral temperatures: hyperthermia (39 degrees C), normothermia (36 degrees C), and hypothermia (32 degrees C). In ischemic animals, hyperthermia produced severe loss of neurons in CA1 and moderate loss in CA3-CA4 subregions. Normothermia in ischemic animals produced severe loss of neurons in the CA1 subregion. Hypothermic ischemic animals showed no significant loss of neurons in any hippocampal region. Ischemia produced a severe decrease (17 +/- 6% of control) in calcium/calmodulin-dependent kinase II activity in hyperthermic animals, a moderate decrease (55 +/- 15% of control) in normothermic animals, and no decrease of enzyme activity in hypothermic animals. Thus, lowering and raising intracerebral temperature decreased and increased, respectively, the extent of ischemia-induced damage in the gerbil. Because ischemia-induced effects on calcium/calmodulin-dependent protein kinase II activity are rapid and long-lasting, hypothermia may protect through preservation of calcium/calmodulin-dependent protein kinase II activity.
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PMID:Effects of ischemia on multifunctional calcium/calmodulin-dependent protein kinase type II in the gerbil. 217 73

The effect of cooling of animals on phosphorylation of proteins in hypothalamus, pituitary gland and adrenals, was studied in white mice. The regulation of protein phosphorylation in cells during hypothermia was carried out via the adenylate cyclase system in all these structures. The calcium-calmodulin system took part in this process in hypothalamus and adrenals.
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PMID:[The regulation of protein phosphorylation in the hypothalamus, hypophysis and adrenals during deep hypothermia]. 217 87

The importance of age-related changes in drug sensitivity is increasingly appreciated. More conclusive evidence is now being presented in combined kinetic and dynamic studies. The type, intensity, and duration of drug action may be affected, ranging from therapeutic failure to major drug toxicity. Alterations in physiologic and homeostatic systems, including the autonomic system, baroreceptors, thermoregulation, and balance, have been described. These may explain the propensity to postural hypotension, falls, hypothermia, and confusion, particularly following drug-induced decrements in these systems. Studies on the sensitivity to individual drugs produce a varied picture emphasizing the danger of generalizations. An increased sensitivity to many agents affecting the central nervous system, including benzodiazepines, halothane, metoclopramide, and narcotic analgesics, is becoming apparent. For the latter this may also be accompanied by an age-associated qualitative difference in toxicity. Whereas there is conclusive evidence of a reduced responsiveness to propranolol, the data are conflicting for calcium antagonists. The increased hypotensive response to ACE inhibitors is more likely due to kinetic factors. The anticoagulant response to warfarin is enhanced. Evidence is also emerging of a wide divergence in the sensitivity of different systems to the same drug--with aging the inotropic effect of theophylline is increased, but the bronchodilator response is decreased. It is becoming clear also that there is a need to separately study certain subgroups of the elderly population.
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PMID:Altered pharmacodynamics in the elderly. 218 23

Use of addictive drugs, such as cocaine, marijuana, and nicotine, affects food and liquid intake behavior, taste preference, and body weight. Changes in specific nutrient status and metabolism can also develop; heroin addiction can cause hyperkalemia and morphine use can result in calcium inhibition. Nutrition-related physiological aspects, such as impaired gastrin release, hypercholesterolemia, hypothermia, and hyperthermia, are also seen with morphine use. Nutrition-related conditions can affect sensitivity to and dependence on drugs and their effects. Diabetes decreases sensitivity to and dependence on morphine, protein deprivation produces preferential fat utilization with low cocaine use, and vitamin D deficiency decelerates morphine dependency. During use and/or withdrawal from nicotine, heroin, marijuana, and cocaine, major changes in food selection and intake occur, which result in weight gain or loss. Detailed human studies are needed to investigate the effects of drug use on the broad spectrum of nutrients and to determine the role of nutrition during drug withdrawal.
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PMID:Nutritional effects of marijuana, heroin, cocaine, and nicotine. 220 48

Massive transfusion, or the rapid administration of a quantity of blood products that approximates an individual's blood volume, is associated with many potentially lethal complications. If the need for transfusion is immediate, ie, before adequate typing and crossmatching procedures can be completed, O negative RBCs can be given safely in the interim. Hypothermia caused by cold banked blood is aggravated by multiple environmental factors and should be aggressively avoided through the use of heat lamps, warming coils, blankets, and other warming devices. The coagulopathy seen in massive transfusion probably has a mixed etiology involving dilution and consumption of clotting factors and platelets. Although fresh frozen plasma and platelets both play a critical role in blood replacement, deficiencies should be treated with appropriate component therapy dictated by coagulation studies rather than by protocol. Transfusion reactions, the most serious type of which is the hemolytic reaction, may go unrecognized in the bleeding patient in critical condition. Hemolytic reactions can usually be prevented by careful attention to administrative and clerical accuracy. Although the overwhelming majority of the 10 million units of blood transfused annually are uncontaminated, transmission of hepatitis and the human immunodeficiency virus through blood products remains a significant screening problem. Posttransfusion hyperkalemia and acidosis are more likely to be related to inadequate resuscitation from shock than to administration of blood. Citrate toxicity and hypocalcemia are usually self-limiting disturbances. Prophylactic use of calcium chloride is dangerous and unnecessary. The complexity of the conditions necessitating massive transfusion demands frequent reevaluation of multiple laboratory and clinical factors for effective resuscitation and for safe administration of blood.
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PMID:Massive transfusion: complications and their management. 220 22

Neuroprotective agents may exert their effect by reducing cerebral oxygen demand (CMRO2), increasing cerebral oxygen delivery, or by altering ongoing pathological processes. Barbiturates provide neuroprotection by reducing the CMRO2 necessary for synaptic transmission while leaving the component necessary for cellular metabolism intact. Isoflurane may exert a neuroprotective effect by a similar mechanism but its efficacy is likely less than that of barbiturates due to adverse effects on cerebral blood flow. Lidocaine reduces CMRO2 by affecting both cellular metabolic processes and synaptic transmission and thus resembles hypothermia in its mechanism of action. Benzodiazepines reduce CMRO2 by reducing synaptic transmission and their use as neuroprotectants produces less haemodynamic compromise than barbiturates. The mechanism of protection by calcium entry blocking agents appears to be due to improved blood flow as opposed to altering abnormal Ca++ fluxes. In contrast, agents such as ketamine and MK-801 may prevent abnormal Ca++ fluxes through their competitive interaction with N-methyl-D-aspartate receptors. Phenytoin prevents K(+)-mediated ischaemic events from progressing. Agents worthy of further investigation include corticosteroids, free radical scavengers, prostaglandin inhibitors and iron chelators.
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PMID:Brain protection: physiological and pharmacological considerations. Part II: The pharmacology of brain protection. 222 93

The use of profound hypothermia and total circulatory arrest for repair of heart defects in neonates usually involves a period of systemic and myocardial bypass cooling. Rapid cooling of muscle (skeletal, smooth, and myocardial) can result in contracture through elevation of cytosolic calcium levels. The increased myocardial tone caused by cooling might render the heart more vulnerable to a subsequent period of cardioplegic ischemic arrest. Infants may be more susceptible to contracture because their small body mass allows more rapid myocardial temperature change when prearrest bypass cooling is used. The influence of avoiding rapid myocardial cooling before induced cardioplegic arrest was analyzed in a group of infants weighing less than 6 kg at the time of open cardiac operation. Myocardial ischemic arrest by warm (37 degrees C) induction blood cardioplegia was used in 57 infants and compared with results in 440 infants treated with standard blood cardioplegia. Multivariate logistic regression analysis revealed that patient diagnosis, weight, and age at operation were significant risk factors for operative mortality. The use of warm induction blood cardioplegia had a strongly positive independent effect on survival (p = 0.0003) for any patient weight, age, or diagnostic group. We recommend the avoidance of rapid myocardial cooling on bypass in all patients before induction of cardioplegic ischemic arrest.
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PMID:Warm induction blood cardioplegia in the infant. A technique to avoid rapid cooling myocardial contracture. 224 12

During hibernation the body temperature may fall to only a few degrees above 0 degree C. The heart of the hedgehog continues to function whereas the hearts of nonhibernating mammals stop beating. The present study was performed to investigate and compare the mechanical responses to hypothermia in rabbits, rats, and hedgehogs. Isometric force was recorded from papillary muscles mounted in an organ bath and effects of hypothermia on the mechanical restitution curve were also compared. A reduction of bath temperature from 35 degrees C caused an increase in peak developed force. Maximum force was seen at 20 degrees C in the rabbit, 15 degrees C in the rat, and 10 degrees C in the hedgehog preparations. In all the species there was a similar prolongation of time to peak force and of time from peak to half-relaxation as temperature was lowered. An increase in resting force and after-contractions were recorded in the rabbit and rat muscles at temperatures below 15 and 10 degrees C, respectively. The rabbit and rat preparations became inexcitable at temperatures below 10 and 5 degrees C, respectively. The hedgehog papillary muscle, on the other hand, still contracted at 0 degree C and did not show increased resting force nor after-contractions. The results are consistent with the hypothesis that there is a calcium overload in cardiac cells from rabbit and rat at low temperatures but there is no calcium overload in the hedgehog muscle during hypothermia.
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PMID:Effects of low temperature on contraction in papillary muscles from rabbit, rat, and hedgehog. 224 56

Anesthetic experience of 4 cases of hepatic resection using veno-venous bypass was reported. Non-forced bypass (passive shunt) was used in case 1. Hepatic resection was performed while supporting hemodynamic stability during the subsequent anhepatic phase using pump-driven veno-venous bypass (active shunt) in case 2-4. Various problems arose in each case. In the non-forced bypass case, hypotension during the bypass created a problem; whereas, hypothermia was pronounced during bypass in the pump-driven bypass cases. Massive transfusion due to bleeding, hypocalcemia, and unintentional hypothermia after veno-venous bypass precipitated heart failure. Attention should therefore be directed toward, (1) preparation for massive transfusion, (2) measurement and correction of the plasma calcium ion concentration, (3) maintenance of body temperature, and (4) hemodynamic control with a Swan-Ganz catheter and an inferior vena cava catheter. Extracorporeal bypass using a pump-driven veno-venous bypass (Bio-pump) and splanchnic decompression system via the portal system appear to be advantageous.
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PMID:[Anesthetic considerations for hepatic resection using veno-venous bypass]. 225 38

The production and prevention of calcium paradox injury in myocardium was studied in a canine model of cardiopulmonary bypass with multidose, moderately hypothermic, crystalloid cardioplegic solution. During 4 1/2 hours of global ischemia, three groups of six dogs each received one of three histidine-buffered cardioplegic solutions (500 ml initially and 250 ml every 30 minutes) at 27 degrees C. Group 1 cardioplegic solution was calcium free, group 2 solution contained a trace amount of calcium chloride (70 mumols /L), and group 3 cardioplegic solution was calcium free but contained diltiazem (150 micrograms/kg body weight). Left ventricular function measured as percent control of developed pressure revealed significantly greater (p less than 0.05) recovery in groups 2 and 3. Triphenyltetrazolium chloride staining showed 35% +/- 9% (mean +/- standard error) of heart mass necrosis in group 1 versus 0% and 0.5% +/- 0.4% in groups 2 and 3, respectively (p less than 0.001). Electron microscopy revealed ultrastructural changes characteristic of calcium paradox injury in group 1 myocardium. Calcium paradox injury was produced in an in vivo model of global myocardial ischemia and multidose cardioplegia despite moderate hypothermia and non-coronary collateral flow. The addition of either trace levels of calcium or diltiazem to the cardioplegic solution was effective in preventing this injury.
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PMID:Calcium paradox in an in vivo model of multidose cardioplegia and moderate hypothermia. Prevention with diltiazem or trace calcium levels. 230 65


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