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

Deep hypothermic circulatory arrest facilitates repair of congenital cardiac anomalies in infants. It is known empirically that hypothermia protects against central nervous system (CNS) ischemic damage. The Q10O2 is only 2.2 for brain and thus a decrease in metabolic rate does not fully account for protective effects of hypothermia. Since enthalpy of dissociation of H2O is high (approximately 7 kcal/mole), its pH is temperature dependent (7.0 at 25 degrees C, 7.4 at 20 degrees C) and hypothermia may in part protect by its influence on hydrogen ion concentration. A manifestation of CNS susceptibility to ischemia is an obstruction of the microcirculation [no-reflow lesion (NRL)] demonstrated by infusion of carbon black into the cerebral circulation after a period of circulatory arrest. White lesions (NRL) against a gray background on cut section of brain increase in size with increasing time of arrest. The effect of anoxia versus circulatory arrest, brain temperature, and extracellular brain pH on NRL was studied in 45 mongrel dogs, subjected to varying periods of N2-induced anoxia on cardiopulmonary bypass (CPB) at 37 degrees C or 20 degrees C. In some studies jugular venous pH was adjusted by infusion of NaHCO3 or HCl. Control groups included normothermic CPB without anoxic and normothermic CPB, anoxia, and equimolar NaCl infusion. NRL was quantified by planimetry of photographs of cut sections of brain. These results confirm that NRL is abated by hypothermia and suggest that (1) NRL is a function of anoxia and not arrested circulation since perfusion with N2 at 37 degrees C does not protect the brain (i.e., NRL is not solely related to "critical reopening pressure") and (2) NRL is in part a function of extracellular pH.
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PMID:Cerebral anoxia: effect of deep hypothermia and pH. 3 7

Segments of superficial and juxtamedullary proximal convoluted tubules of the rabbit were perfused in vitro to examine the mechanisms responsible for net volume reabsorption. The very early postglomerular segments were not studied. Fluid reabsorptive rates and transepithelial potential differences were compared under various conditions: (a) with perfusate that simulated glomerular filtrate; (b) with perfusate that lacked glucose, amino acids, and acetate and that had HCO(3) and Cl concentrations of 5 and 140 mM, respectively; (c) with perfusate that lacked glucose, amino acids, and acetate but with 20 meq of NaHCO(3) replaced with 20 meq of Na cyclamate; (d) with the same perfusate as in b but in the presence of ouabain in the bath; (e) with ultrafiltrate of rabbit serum titrated with HCl to final HCO(3) and Cl concentrations of 2 and 134 mM, respectively. Tubules were perfused with this titrated ultrafiltrate at 37 degrees C, 21 degrees C, and in the presence of 0.1 mM ouabain in the bath. Bath fluid in all experiments was regular rabbit serum. Under conditions a and b superficial proximal convoluted tubule (SFPCT) and juxtamedullary proximal convoluted tubule (JMPCT) behaved similarly with the exception that SFPCT exhibited a lumen-positive and JMPCT a lumen-negative electrical potential under condition b. However, under condition c SFPCT failed to exhibit net volume reabsorption, whereas reabsorption in JMPCT continued unchanged. Ouabain did not affect volume reabsorption in SFPCT under condition d, whereas neither ouabain nor hypothermia affected SFPCT under condition e. In contrast, ouabain and hypothermia totally inhibited volume reabsorption in JMPCT under conditions d and e. These studies document heterogeneous mechanisms responsible for volume reabsorption in the major portions of SFPCT and JMPCT with passive forces predominating in SFPCT and active forces in JMPCT.
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PMID:Characteristics of volume reabsorption in rabbit superficial and juxtamedullary proximal convoluted tubules. 42 62

I.p. injections of desipramine-HCl (100 mg/kg) produced decreases in the contents of several amino acids of mouse brain after 1 h. Using a 10-100 mg/kg range of doses, these effects appeared to be dose-dependent for alpha-alanine and aspartate. These changes may be due, in part, to a decrease in cerebral oxidative metabolism (Krebs cycle activity) which occurs secondarily to desipramine-induced hypothermia.
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PMID:Effect of desipramine on the contents of some free amino acids of mouse brain. 62 61

Quinine HCl in doses from 10-50 mg/kg lowered the body temperatures of nonfebrile rats in the cold, primarily by suppressing shivering. However, if given an opportunity to turn on a heat lamp the rats worked much more than normal after a quinine injection and were theraby able to counteract the hypothermia to some extent. The effect of quinine is interpreted as an action on effector mechanisms rather than as an alteration of the thermal setpoint.
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PMID:Quinine-induced hypothermia in cold-exposed rats. 89 91

Rectral temperatures and feeding activity were measured in adult male rats every 30 min for 4 hr, then every 4 hr following daily s.c. injections at 08:00 or 20:00hr or saline or heroin. Initial heroin injections disrupted diurnal temperature and feeding rhythms: 5 mg/kg heroin HCl induced hyperthermia and abolished feeding for 2 hr; 20 mg/kg led to hypothermia, then hyperthermia and abolished feeding for 4 hr. By the 5th heroin day hyperthermia and increased feeding occurred in all groups with a shorter latency to onset. Total food intake was higher than on the 1st heroin day but the diurnal patterns remained disrupted. Changes in both diurnal rhythms again occurred on the 1st withdrawal day as hypothermia, sporadic feeding and hyper-irritability were observed. By the 5th withdrawal day diurnal temperature and feeding rhythms resembled those of the control period. Monitoring diurnal temperature and feeding patterns of rats reveals characteristic dose-related disruptions after heroin which are modified by repeated doses as tolerance develops and which eventually disappear on withdrawal.
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PMID:Changes in diurnal temperature and feeding patterns of rats during repeated injections of heroin and withdrawal. 103 35

Using several routine screening procedures to determine anti-depressant drug activity in experimental laboratory animals, ketamine HCl was found to possess significant activity over a wide-range of oral doses. The tests used were (a) reversal of tetrabenazine-induced ptosis in mice, (b) reversal of reserpine-induced hypothermia in rats, (c) enhancement of yohimbine toxicity in mice and (d) inhibition of oxotremorine-induced tremors in mice. In general, the anti-depressant potency of ketamine HCl was substantially less than that of imipramine HCl.
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PMID:Evaluation of ketamine HCl for anti-depressant activity. 115 26

Four groups of mink were immobilized with medetomidine-HCl (MED) 0.1 mg/kg + ketamine (KET) 5 or 7.5 mg/kg at different ambient temperatures. The induction time, degree of immobilization and analgesia, rectal temperature, heart and respiration rates were recorded at intervals throughout the immobilization period. The animals were then given atipamezole-HCl (ATI) 0.5 mg/kg for reversal at different times after injection of MED/KET and the effects of the antagonist were evaluated. Subcutaneous administration of MED/KET induced complete immobilization in all 20 animals, and the highest dose was considered suitable for major surgery. Prolonged immobilization at low ambient temperatures (-10 to +5 degrees C) caused severe hypothermia in all animals. The mean rectal temperature had dropped to 37.8 degrees C and 32.1 degrees C at 15 and 85 min, respectively, after injection of MED/KET, significantly lower than the corresponding values for animals immobilized at room temperature. Intramuscular administration of ATI 20 or 40 min after injection of MED/KET rapidly remobilized the animals without apparent side-effects. Administration of ATI to animals recovering spontaneously 90 min after injection of MED/KET induced thermogenesis (shivering) in animals immobilized at a low ambient temperature, while no such effect was seen in animals immobilized at room temperature. One hour after injection of ATI, the rectal temperatures of all treated animals had returned to normal and there were no signs of abnormal behaviour.
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PMID:Immobilization of mink (Mustela vison) with medetomidine-ketamine and remobilization with atipamezole. 136 Dec 73

Metabolic acidosis immediately after surgical operation is followed by metabolic alkalosis. Hormonal change by surgical stress and anaerobic glucolysis due to tissue ischemia cause initial lactic acidosis. Later alkalosis may be caused by secondary aldosteronism and bicarbonate production from lactate and citrate supplied by massive infusion and transfusion. Postoperative complications, such as respiratory insufficiency, renal failure and hypovolemic or septic shock, cause acidosis. In the gastrointestinal surgery, acidosis can be caused by starvation and loss of bicarbonate contained in bile, pancreatic juice or intestinal fluid, and alkalosis can be caused by loss of HCl in gastric juice. Severe acidosis can be caused by extracorporeal circulation, hypothermia, low output syndrome or declamping shock in cardioaortic surgery.
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PMID:[Acid-base disturbances in surgical operation]. 143 18

Urethane-anesthetized rats were used to study the mechanism of cocaine-induced death. Continuous recording of the changes in five physiological parameters, including respiratory rate (RR), electroencephalogram (EEG), blood pressure (BP), electrocardiogram (ECG), and body temperature (BT), were conducted after intraperitoneal (IP) administration of a single dose of cocaine HCl (70 mg/kg). In the control group (normothermic with core body temperature 37.7 +/- 0.1 degree C and spontaneously breathing), the death rate was 88% (15/17), and the average time to respiratory arrest was 12.99 +/- 1.40 min (mean +/- SEM). The first set of experiments investigated the contribution of hypothermia to cocaine-induced death. The hypothermic group (core body temperature 33.9 +/- 0.3 degrees C and spontaneously breathing) had a death rate of 81.5% (22/27), and an average time to respiratory arrest of 16.70 +/- 1.24 min, which was significantly (p les than 0.05) prolonged. A substantial decrease in respiratory rate was seen in normothermic group, while all the other measured parameters remained relatively stable until respiratory arrest. Sequential arterial blood gas data in this group showed a decrease in PaO2 from 116.0 +/- 5.7 mmHg to 57.7 +/- 4.6 mmHg, an increase in PaCO2 from 27.7 +/- 2.2 mmHg to 42.7 +/- 3.0 mmHg, and a decrease in pH from 7.467 +/- 0.039 to 7.357 +/- 0.003. To confirm that respiratory depression was an important mechanism of cocaine-induced death in this model, ten normothermic rats underwent mechanical ventilation, and all survived cocaine exposure. This study points to the important role of respiratory depression as a cause of cocaine-induced death.
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PMID:Cocaine-induced respiratory depression in urethane-anesthetized rats: a possible mechanism of cocaine-induced death. 178 91

Effects of morphine on the rectal temperature and respiratory rate, and [3H]naloxone binding to brain membranes from seven brain regions were compared among six strains of male mice, including DBA/2N, C57BL/6N, BALB/c, C3H/HeN, A/J and ICR. The administration of 10 and 20 mg/kg doses of morphine HCl to these strains of mice decreased rectal temperature and respiratory rate. However, there was a significant strain difference in these two measures of the effect of morphine. The DBA/2N strain was the most sensitive in both measures of morphine action. The magnitude of hypothermia was positively correlated with respiratory depression among six strains of mice after the administration of 10 and 20 mg/kg morphine HCl, suggesting common mechanisms. Strain difference in naloxone binding in the brain regions could not explain that of the morphine responses, because there was no correlation between the intensity of morphine-induced hypothermia or respiratory depression and the regional [3H]naloxone binding for the mouse strains.
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PMID:Strain difference in the effects of morphine on the rectal temperature and respiratory rate in male mice. 309 May 93


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