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

To study the cerebral protective effects of hypothermia in arterial hypoxia, anesthetized (70% N2O), mechanically ventilated rats were cooled to a body temperature of 27 C. Hypoxia was induced by decreasing the oxygen content in the inspired gas mixture either to 6-7 per cent or to 2.5-3 per cent. This reduced mean PaO2 to about 25 and 11-12 torr, respectively. At PaO2 torr, there was no change in cerebral blood flow (CBF), cerebrla oxygen consumption (CMRO2), or labile tissue metabolites. The absence of signs of cerebral hypoxia could be attributed to an effect of temperature and pH on the hemoglobin-oxygen dissociation curve. Thus, at 27 C with a PaO2 of 25 torr the total oxygen content (TO2) of arterial blood remained greater than 15 ml (100 ml)-1, about three times the value obtained at this PO2 in normothermic rats. At PaO2 11-12 torr, arterial TO2 was reduced to about 5 ml (100 ml) (-1). The hypoxia induced no change in CMRO2, a threefold increase in CBF, a moderate lactacidosis in the tissue, and a small decrease in phosphocreatine content, but no change in ATP, ADP, or AMP. These changes are less marked than those occurring at the same arterial TO2 in normothermic rats. It is concluded that hypothermia exerts a pronounced protective effect on the brain in hypoxic hypoxia, and that two mechanisms are involved. First, since hypothermia shifts the oxyhemoglobin-dissociation curve towards the left, and prevents or minimizes a rightward shift due to acidosis, it maintains a high TO2 in arterial blood at a given PaO2. Second, by reducing CMRO2, and thereby presumably also cellular energy requirements, hypothermia exerts a protective effect at the cellular level.
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PMID:Protective effect of hypothermia in cerebral oxygen deficiency caused by arterial hypoxia. 0 Sep 30

The influence of elevated and reduced body temperatures upon the metabolic state of the brain was evaluated from the tissue concentrations of phosphocreatine (PCr) ATP, ADP and AMP and from the concentrations of glucose, lactate and pyruvate in immobilized and artificially ventilated rats anesthetized with 70% N2O. The results were compared to the results obtained in normothermic animals. It was found that rats with body temperatures of 32 degrees and 22 degrees C had the same brain tissue concentrations of high energy phosphates and the same adenylate energy charge as the controls, but hypothermia led to a progressive decrease of both cerebral and arterial lactate and pyruvate concentrations. A metabolic acidosis but no excess lactate appeared in the blood. At a body temperature of 42 degrees C, the metabolic pattern in the brain agreed with a state of hypoxia at a time when there was no sign of substrate depletion. Arterial blood showed excess lactate which may indicate an inadequacy of the oxygen supply also to other tissues.
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PMID:Effects of hypothermia and hyperthermia on brain energy metabolism. 24 Nov 93

The prevention and control of massive bleeding has always been a problem in neurosurgical procedures, particularly in patients with arteriovenous malformations, intracranial aneurysms, and large vascular tumors. During the past 25 years, new technics have reduced the risk of hemorrhage; however, these have been most suitable for adult patients. Vascular intracranial lesions during infancy present even more complex problems. This is a report of the anesthetic management of a 7-month-old infant with an aneurysm of the v cerebri magna (great vein of Galen). Anesthetic management consisted of (1) halothane-N2O-O2 general endotracheal anesthesia, (2) surface-induced profound hypothermia, and (3) low-flow extracorporeal circulation. Phenothiazine premedication was used with halothane anesthesia to antagonize reflex vasoconstriction during hypothermia, hypothermia and low cardiac output to lessen the possibility of hemorrhage, aneurysmal rupture, and neurologic damage, and surface-induced hypothermia because it provides better core perfusion than central cooling. This technic allowed a successful outcome in an otherwise high-risk procedure.
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PMID:Anesthetic management of an intracranial arteriovenous malformation in infancy. 55 21

Sequential determinations of halothane blood solubility were determined in 8 patients undergoing cardiac surgical procedures with cardiopulmonary bypass (CPB), hypothermia, and crystalloid hemodilution. The mean temperature-corrected blood/gas partition coefficient (B/G) at the end of surgery (2.4) was lower than preceding induction (2.7). The greatest mean B/G (2.9) occurred after induction of anesthesia. The halothane B/G did not increase significantly at the inception of CPB but decreased from a mean 2.7 to 1.6 as the patients were rewarmed. The maximum range of B/G for a single patient was 1.4 to 3.1. For halothane, the increased blood solubility due to hypothermia was initially antagonized by the crystalloid hemodilution. This antagonism would also be anticipated for methoxyflurane, enflurane, and isoflurane. For N2O and diethyl ether, the increased blood solubility due to hypothermia would be unopposed by simultaneous crystalloid hemodilution.
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PMID:Crystalloid hemodilution, hypothermia, and halothane blood solubility during cardiopulmonary bypass. 56 87

The influence of phenobarbitone anaesthesia on cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRo2) during hypothermia (23 degrees C & 27 degrees C) was studied in the rat, using a modification of the Kety & Schmidt (1948) technique and arterio-venous differences for oxygen. Phenobarbitone (150 mg/kg) was found to decrease CMRo2 by 40-60% during hypothermia, when compared to N2O anaesthesia. At a body temperature of 23 degrees C, and during phenobarbitone anaesthesia, CMRo2 was reduced to about 15% of normal control value (about 10.3 ml.100g-1). CBF was reduced to about 50% of the phenobarbitone control value but was similar to the value obtained with N2O anaesthesia at 22 degrees C. It is concluded that the combination of phenobarbitone anaesthesia and hypothermia results in a more pronounced reduction in cerebral metablic rate for oxygen than can be achieved by administration of barbiturates to normothermic animals, or by reducing body temperature by 15 degrees C during superficial anaesthesia.
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PMID:Reduction of cerebral blood flow and oxygen consumption with a combination of barbiturate anaesthesia and induced hypothermia in the rat. 63 8

A 72-year-old male underwent radical operation for cancer of the tongue. Anesthesia was maintained with the combination of enflurane-N2O-vecuronium and cervical epidural block. Five minutes after the cessation of the longstanding operation, VT and circulatory collapse occurred. After administration of lidocaine and ephedrine, VPC and ST elevation were noted, followed by VT and Vf. Cardioversion successfully restored sinus rhythm with no ST change, suggesting an episode of coronary artery spasm. The possible inducing factors in this case were hypotension and acute imbalance in autonomic nervous systems caused by hypovolemia, hypothermia, insufficient anesthetic depth, loss of surgical stress, neostigmine and epidural block. The authors reviewed case reports on coronary spasm, especially looking for possible inducing factors of coronary artery spasm during anesthesia.
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PMID:[Coronary artery spasm immediately after the long-standing operation for cancer of the tongue]. 147 69

We studied the response of the sympatho-adrenal system to varying intensities of different stimuli. Concentrations of norepinephrine and epinephrine in plasma as well as densities of beta 2-adrenergic receptors on mononuclear leukocytes were determined in patients subjected to operations of varying complexity and different types of anaesthesia. In patients undergoing hysterectomy (n = 9), the maximal increases in plasma norepinephrine and epinephrine were 2.7- and 2.8-fold, respectively, corresponding to a post-operative decrease of the mononuclear leukocyte beta 2-adrenergic receptors of 27% after 4 hours. Patients with coronary revascularization (n = 17) were randomly selected to receive either enflurane/N2O or neurolept anaesthesia. During intraoperative periods of stress, such as cardiopulmonary bypass and hypothermia, norepinephrine and epinephrine levels were 2-3 times higher in the neurolept patients, compared with the enflurane patients. In the former group, the respective maximal norepinephrine and epinephrine concentrations were 9.7 and 28 times the vasal values of the non-anaesthetized patients. One day postoperatively, the mononuclear leukocyte beta 2-receptor density decreased maximally by 45 +/- 11% in the enflurane patients, and by 53 +/- 6% in the neurolept patients. As early as two to five days after cardiac surgery, beta 2-receptor densities were no longer distinguishable from the preoperative values. Significant correlations between the increases in catecholamine concentrations and the decreases in beta 2-receptor densities did not exist. It is concluded that enflurane blocks the sympatho-adrenal response to surgical stress more effectively than neurolept anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Magnitude and kinetics of alterations in plasma catecholamines and leukocyte beta-adrenergic receptors in response to anaesthesia and surgery. 197 38

Argon, nitrogen, nitrous oxide were administered hyperbarically in doses (atmosphere) that caused loss of righting reflex (LORR). Nitrous oxide requires pressure somewhat less than two atmospheres, eighteen atmospheres were required for argon and thirty-six atmospheres roughly for nitrogen all in 0.5 atmospheres oxygen. Loss of righting reflex was assessed by using a rolling cage method of Wilson and Miller. Since nitrogen is the least liposoluble and nitrous oxide the most liposoluble of these three gases, greater pressures were needed for nitrogen to attain sufficient concentration in the membrane for anesthesia. Due to the low lipid solubility (1.4), nitrous oxide was administered hyperbarically at a compression rate of less than 0.5 atm/min at chamber temperature of 86 degrees plus or minus 2 degrees. Body temperatures were measured by minimitter transmitters. Two types of transmitters: an AM frequency and an FM frequency were used; a comparison of the two systems were made. The ED50 (atmospheres) required to produce a given score on the LORR were determined for each strain or line of mice. This ED50 value was determined for the Hot and Cold selection lines which have been specifically bred to differ as much as possible in a hypothermic response to acute doses of ethanol. These experiments demonstrate quite clearly a degree of commonality exists among CNS depressants with regard to anesthesia, loss of righting reflex and hypothermia.
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PMID:Commonalities between gas anesthetics (nitrous oxide, nitrogen and/or argon) and ethanol intoxication in hot and cold selection line mice. 206 46

Potassium homeostasis was studied in 30 patients undergoing cardiac surgery by employing cardiopulmonary bypass (CPB) and moderate hypothermia, and using morphine, N2O, relaxant anaesthesia. There was a trend for hypokalemia, and for maintaining a K+ level of 4-4.5 mmol/l, K+ infusion was required during CPB (9.017 mmol/m2 BSA/h). K+ infusion required in the post-operative period was considerably less (1.532 mmol/m2 BSA/h). There was no significant difference in the K+ levels of patients receiving preoperative diuretic therapy, as compared to those not receiving such therapy. Potassium requirement was significantly higher in patients under-going CABG and valvular heart disease, as compared to congenital heart disease. The mean urinary loss of K+ during bypass was found to be 2.95 mmol/m2 BSA/h, which was only 32 per cent of that required to be infused (9.017 mmol/m2 BSA/h). The mean excretion of K+ in the post operative period was significantly higher (4.53 mmol/m2 BSA/h) than K+ required to be infused during this period (1.532 mmol/m2 BSA/h).
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PMID:Potassium homeostasis during & after cardiopulmonary bypass. 207 59

The hypothesis that both active and passive airway humidification prevents hypothermia in infants and children, but that neither decreases the duration of postoperative recovery was tested. Twenty-seven ASA physical status 1 or 2 patients were studied who weighed between 5 and 30 kg, underwent superficial operations, were anesthetized with halothane and 70% N2O, and whose lungs were ventilated via a Rees modification of an Ayre's t-piece. The children were randomly assigned to receive active airway humidification and warming using an MR450 Servo airway heater and humidifier set at 37 degrees C (n = 10), passive airway humidification using the Humid-Vent 1 heat and moisture exchanger placed between the Ayre's t-piece and the endotracheal tube (n = 8), or no airway humidification and heating (control, n = 9). Distal tracheal and tympanic membrane temperatures and airway humidity were recorded during the first 90 min of surgery. Rectal temperature was measured during the postanesthetic recovery period. Relative humidity of inspired respiratory gases was approximately 30% in the control group and approximately 90% in the group given active airway humidification. Initial inspired humidity in the passive humidification group (50%) increased to approximately 80%, a level not significantly different from that in the active group after 80 min of anesthesia. Central body temperature increased 0.25 degrees C during active active airway humidification and heating, whereas temperature decreased 0.25 degrees C during passive humidification and 0.75 degrees C without airway humidification. Distal tracheal temperature was significantly higher in the groups given passive and active humidification than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Passive and active inspired gas humidification in infants and children. 231 44


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