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

The responsiveness of the medullary chemoreceptors, measured by the ventilatory response to hypercapnia given in an hyperoxic gas mixture in intact anesthetized dogs has been evaluated during normothermia and at two levels of hypothermia. The response was studied in: 1) 20 dogs during normothermia, 2) 10 of these dogs at a blood temperature of 32-33 degrees C, and 3) in the other 10 dogs during deeper hypothermia (28-29 degrees C). The ventilatory response to CO2 decreased while blood temperature was lowered until the response became absent during deep hypothermia. For normothermia and both levels of hypothermia a similar oxygen drive of ventilation was found which was equivalent to approximately one fourth of the spontaneous ventilation. It is suggested, that in the deeply hypothermic animal the normal respiratory drive is apparently of peripheral (arterial) chemoreceptor origin and when this drive is nullified or significantly decreased, gentle shivering could be responsible for stimulating the respiratory center.
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PMID:Carbon dioxide response curves during hypothermia. 0 Jun 52

In 12 rabbits hypothermia and rewarming were induced with temperature-controlled circulating peritoneal dialysis in combination with temperature-controlled hypoxic and hypercapnic gas mixtures. The average cooling time necessary for the esophageal temperature to decrease from 37.7 degrees +/- 0.7 to 20.6 degrees +/- 1.0 degrees C was 81 +/- 34 minutes with a range of 41 to 150 minutes. The average warming time for esophageal temperature to increase from 20.6 degrees +/- 1.0 degrees C to 35.2 degrees +/- 1.8 degrees C was 90 +/- 35 minutes. Time of cooling was related to the proportions of inspired carbon dioxide and oxygen. In contrast to surface and bypass methods, esophageal and muscular temperatures agreed very closely, suggesting an absence of regional temperature gradients.
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PMID:Hypothermia and rewarming by peritoneal dialysis and temperature-controlled inhalate. 0 72

Blood gases were measured in hibernating and hypothermic animals as a biological model of clinical hypothermia. Blood gas analyses from hamsters and dormice were carried out with the aid of permanent arterial catheters during normothermia and hibernation. In golden hamster pH increased from 7.30 to 7.46 during hibernation and PaCO2 decreased from 59.7 to 40.5 mm Hg. In dormice pH increased from 7.24 to 7.44 and PaCO2 decreases from 38.5 to 27.4 mm Hg. The actual bicarbonate concentration increased from 29 to 52 mMol in golden hamsters and from 16 to 34 mMol in dormice during hibernation. In experiments with induced hypothermia in golden hamsters under ketamine-anaesthesia there was no correlation between temperature and PaCO2. Despite the slight decrease in PaCO2 during hibernation we conclude that PaCO2 rather than total carbon dioxide content is held constant when temperature is changed. During clinical hypothermia it will probably be safe to keep PaCO2 constant.
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PMID:Blood gas analyses of hibernating hamsters and dormice. 1 44

The respiratory pathophysiology of A2 influenza infection was studied in mice treated with small-particle aerosols (SPA) of rimantadine or ribavirin. Untreated infections in mice resulted in survival rates of 15% or less and were characterized by (i) severe hypoventilation (decreased P(O2) and increased P(CO2)), (ii) compensated respiratory acidosis (increased P(CO2) and HCO(3) (-), with normal pH), (iii) pneumonia with increased ratio of wet/dry lung weight, and (iv) hypothermia. Treatment with SPA of rimantadine (21 mg/kg per day for 4 days) beginning 72 h after virus challenge significantly improved survival rate (80%) but failed to alter lung pathology from that found in infected, untreated mice. Rimantadine treatment decreased somewhat the severity of hypoventilation, respiratory acidosis, lung wet weight, hypothermia, and lung virus titers from that observed in infected, untreated mice. SPA of ribavirin (26 mg/kg per day for 4 days) initiated 6 h after SPA exposure of mice to virus significantly improved survival rate (95%) and reduced lung virus titers and lung pathology. Gas exchange and pulmonary edema in ribavirin-treated, infected mice were significantly improved over those of infected, untreated controls. The mechanisms for increased survival rates induced by SPA of rimantadine remain uncertain, since increased survival rates could not be ascribed entirely to improvements in lung functions. In contrast, however, ribavirin treatment appeared to improve survival rates by reducing major lung pathology and pulmonary dysfunction. This was probably mediated through the antiviral effects of ribavirin.
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PMID:Effects of small-particle aerosols of rimantadine and ribavirin on arterial blood pH and gas tensions and lung water content of A2 influenza-infected mice. 1 87

When blood temperature is changed in closed system ('anaerobic') conditions, plasma pH and PCO2 vary but no titration by external CO2, acid or alkaline equivalents takes place. It is therefore assumed that the overall acid-base state undergoes no fundamental change. This is further justified by the constancy of osmotic relationships between plasma and red cells, and to a lesser extent of relative alkalinity and protein alpha imidazole (Reeves, 1972, 1976a, b). These considerations serve as a basis for a correction procedure of pH and PCO2 of blood in open systems in vivo to a standard temperature T* (25 degrees C, eventually 37 degrees C). The temperature-corrected values pH* and P*CO2, and the derived [HCO3]* can be represented on a temperature-independent bicarbonate-pH diagram. This permits an easier interpretation of blood acid-base changes occurring together with body temperature variations, such as in ectotherms, hibernators or in artificial hypothermia. Extension to intracellular pH is considered.
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PMID:Blood acid-base state at a variable temperature. A graphical representation. 2 17

The content of the free fatty acids, ketone bodies, total glycogen, glucose, adrenaline and noradrenaline and morpho-histochemical picture of the tissues of neuro-endocrinal system (hypophysis and adrenal) in the brain, heart, liver, skeletal muscles and blood of the white non-linear rats, were studied 2-3 min adaptation to complex atmosphere changes: gradual increase of the CO2, decrease of the O2, and cooling (in the condition of deep hypothermia the rectal temperature was--RT--19.1 +/- 0.1 degrees C). The same parameters were studied in 48 hrs after the same training (at normothermia) and in 2-3 min. after the same repeated training in 48 hrs after the first one, at RT--20.2 +/- 0.1 degrees C. The fluctuating character of the metabolism and of the regulating systems was shown.
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PMID:[Character of metabolism and regulating role of cholinoreactive tissue systems during hypercapnia, hypoxia and cooling]. 19 72

Acid-base terminology including the sue of SI units is reviewed. The historical reasons why nomograms have been particularly used in acid-base work are discussed. The theoretical basis of the Henderson-Hasselbalch equation is considered. It is emphasized that the solubility of CO2 in plasma and the apparent first dissociation constant of carbonic acid are not chemical constants when applied to media of uncertain and varying composition such as blood plasma. The use of the Henderson-Hasselbalch equation in making hypothermia corrections for PCO2 is discussed. The Astrup system for the in vitro determination of blood gases and derived parameters is described and the theoretical weakness of the base excess concept stressed. A more clinically-oriented approach to the assessment of acid-base problems is presented. Measurement of blood [H+] and PCO2 are considered to be primary data which should be recorded on a chart with in vivo CO2-titration lines (see below). Clinical information and results of other laboratory investigations such as plasma bicarbonate, PO2,P50 are then to be considered together with the primary data. In order to interpret this combined information it is essential to take into account the known ventilatory response to metabolic acidosis and alkalosis, and the renal response to respiratory acidosis and alkalosis. The use is recommended of a chart showing the whole-body CO2-titration points obtained when patients with different initial levels of non-respiratory [H+] are ventilated. A number of examples are given of the use of this [H+] and PCO2 in vivo chart in the interpretation of acid-base data. The aetiology, prognosis and treatment of metabolic alkalosis is briefly reviewed. Treatment with intravenous acid is recommended for established cases. Attention is drawn to the possibility of iatrogenic production of metabolic alkalosis. Caution is expressed over the use of intravenous alkali in all but the severest cases of metabolic acidosis. The role of 2,3-diphosphoglycerate on tissue oxygenation is stressed and use of intravenous sodium phosphate as an alternative to intravenous bicarbonate is mentioned.
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PMID:The physiological assessment of acid-base balance. 23 27

The effects of Forane anesthesia for deep surface hypothermia with 30 minutes of total circulatory occlusion were evaluated. With 100% O2 6 of 7 dogs developed motor disorders postoperatively, while 3 of 5 with 98% O2/2% CO2 and none with 95% O2/5% CO2 developed motor disorders. Cooling was uneventful except for 1 episode of ventricular fibrillation in the 5% CO2 group at 23 degrees C. Resuscitation was easy, but the early rewarming period was characterized by repeated episodes of ventricular fibrillation and delayed recovery of cardiac function, especially in the 100% O2 group. Blood lactate levels remained low during cooling and gradually increased during rewarming in all groups, with the highest levels in the 100% O2 group and the lowest in the 5% CO2 group. It is concluded that Forane can be used for surface hypothermia with 30 minutes' circulatory occlusion when administered in 95% O2/5% CO2. A Comparison of these results with previously reported series indicates that Forane is inferior to ether but may be superior to halothane for surface hypothermia.
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PMID:The use of Forane anesthesia for surface-induced deep hypothermia. 24 Mar 30

Unanesthetized and unrestrained rats, chronically cannulated in the carotid artery, were exposed to normal air (NA) and Helox (21% O2, 79% He) at ambient temperatures (Ta) of 22 and -10 degrees C. In Helox at Ta = 22 degrees C, the Vo2 was 1.39 ml O2/g-h and the Vco2 0.98 ml CO2/g-h, 145 and 126%, respectively, of the values in NA at Ta = 22 degrees C. The arterial Pao2, Paco2, and pH were comparable in Helox and NA at Ta = 22 degrees C. In Helox at Ta = -10 degrees C, rats invariably became hypothermic after exposure of 0.75 to 1.5 h. During the induction of hypothermia the decrease of Vo2 and Vco2 was oscillatory, Pao2 and pH increased, and Paco2 decreased significatnly (P less than 0.05). Minimum Vo2 and Vco2 during hypothermia averaged 0.71 ml O2/g-h and 0.50 ml CO2/g-h, 23 and 22%, respectively, of the values in normothermic animals at Ta = -10 degrees C. Minimum body temperature during hypothermia was clamped at 21.7 +/- 0.3 degrees C (X +/- SE) by increasing Ta to 19 degrees C. When Helox was replaced by NA, hypothermic rats rewarmed spontaneously, returning to normothermia within 4 h. The data suggest that hypothermia induced by Helox plus cold does not seem to be due to respiratory failure, as systemic hypoxia or hypercapnia were not observed. The controlled hypothermia cycle reported here provides a model for dynamic studies of thermogenic mechanisms both at the normothermic and hypothermic states without the interference of drugs and other nonphysiological treatments.
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PMID:Metabolic and respiratory responses during Helox-induced hypothermia in the white rat. 24 22

To assess the effects of moderate potassium cardioplegia (37 mEq/l KCl) on the severity of myocardial ischemia during arrest and on post arrest ventricular function, 32 isolated, isovolumic feline hearts were studied before, during and 1 hour after ischemic arrest. Normothermia (37 degrees C) was maintained in the remaining 16 hearts, eight without KCl and eight with KCl. Hypothermia (27 degrees C) was maintained in the remaining 16 hearts, eight with KCl and eight without KCl. Myocardial oxygen (PmO2) and carbon dioxide tensions (PmCO2) were measured by mass spectrometry. Maximum developed intraventricular pressure (max DP) and max dP/dt were used as indices of performance. Compared with normothermic or hypothermic arrest alone, the addition of potassium cardioplegia resulted in a significant reduction in the peak PmCO2 measured during the arrest period. Hypothermia alone resulted in morphologic evidence of improved myocardial preservation and a significant reduction in peak PmCO2 compared with normothermia. Post arrest ventricular function was best with the combination of hypothermic arrest and potassium cardioplegia (max DP = 96 +/- 6% of control and max dP/dt = 99 +/- 5% of control). These data suggest that the beneficial effects of postassium cardioplegia and 27 degrees hypothermia are additive, and that reduction in myocardial ischemia as evidenced by a reduction in peak PmCO2 correlated with improvement in ventricular performance in the post arrest period and with preservation of myocardial structure.
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PMID:Effect of potassium cardioplegia on myocardial ischemia and post arrest ventricular function. 30 60


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