Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
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.
 ...
PMID:Carbon dioxide response curves during hypothermia. 0 Jun 52

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.
 ...
PMID:Protective effect of hypothermia in cerebral oxygen deficiency caused by arterial hypoxia. 0 Sep 30

In order to study the relationship between arterial PCO2 and cerebral blood flow (CBF) in hypothermia, the body temperature of artifically ventilated rats was decreased to 22 degreesC, and changes in CBF were evaluated from arteriovenous differences in oxygen content (AVDO2) at PaCO2 values of 15, 30, 40 and 60 mm Hg. The results were compared to those obtained at normal body temperature (37 degrees C) over the PaCO2 range 15-60 mm Hg. Separate experiments were performed to evaluate CBF and CMRO2 at 22 degrees C and a PaCO2 of 15 mm Hg, using an inert gas technique for CBF. The tissue contents of phosphocreatine, ATP, ADP, AMP and lactate were measured in hypothermic animals at PaCO2 values of 15, 30 and 60 mm Hg. The results showed that changes in CBF were of the same relative magnitude in hypothermia and normothermia when PaCO2 was increased from about 35 to about 60 mm Hg. However, with a decrease in PaCO2 the reduction in CBF was much more pronounced in hypothermia, and at PaCO2 15 Mm Hg CBF was less then 20% of the value measured in normothermic and normocapnic animals. The results of the metabolite measurements gave no evidence of tissue hypoxia in spite of the pronounced reduction in CBF. Although the results demonstrate that the brain of a hypothermic animal is protected against the harmful effects of a lowered CBF, it may not warrant recommending hyperventilation in clinical cases of hypothermia, especially not in patients with arteriosclerosis or cerebrovascular diseases.
 ...
PMID:Influence of changes in arterial PCO2 on cerebral blood flow and cerebral energy state during hypothermia in the rat. 0 61

Hypocapnia during extracorporeal circulation in hypothermia increases oxygen consumption. Po2 in mixed venous blood decreases. This probably reflects a decrease in tissue oxygen tension. Hyperventilation will therefore increase the risk of hypoxia in critically perfused tissues. Therefore we recommend to keep PaCO2 (T) constant at 40 mm Hg during hypothermia.
 ...
PMID:[The influence of PaCO2 on oxygen consumption during extracorporeal circulation in hypothermia (author's transl)]. 0 89

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.
 ...
PMID:Hypothermia and rewarming by peritoneal dialysis and temperature-controlled inhalate. 0 72

Pulmonary complications after cardiac surgery under extracorporeal circulation remain frequent and sometimes grave, in spite of the great progress which has been made over the past 20 years in the methods of cardiorespiratory assistance. The authors analyse the clinical and radiological repercussions of perfusion on the lung, in 40 patients operated under ECC for coronary revascularisation. The simutaneous study of the arterial, and mixed venous blood gasses and of the alveolar gases, in 20 of these patients showed the constant occurrence of a shunt syndrome, without alveolar hypoventilation or disorders in peripheral circulatory flow. Ventilatory alcalosis, hypocapnia, hypoxemia and the rise in the alveolar arterial oxygen gradient is increased during the second post-operative day. Among the variables studied (duration of ECC, degree of hypothermia, duration of the intervention, duration of anesthesia, pleurotomy) only the latter intervened in a statistically significant manner in this study, in the increase in hypoxemia. 46 pulmonary biopsies carried out before and after ECC in 23 coronary patients were examined with the electron microscope. The initial alveolar involvement affects the septal microcirculation with signs of an increase in capillary permeability leading to an interstitial and epithelial destruction. The use of a membrane oxygenator prevents some of the alveolar lesions, as has been proved by the study of five pulmonary biopsies carried out in dogs submitted to ECC of long duration. Catherterization of the pulmonary artery carried out in 35 patients by means of a SWAN-GANZ catheter, before the intervention enabled supervision of the degree of importance and speed of the hemodynamic variations in the pulmonary circulation during the different phases of ECC (during the phase of ventricular fibrillation). The rise in the flow of left output can lead to the occurrence of negative pulmonary intravascular pressures which can be prejudicial for capillary trophicity. The syndrome of "ECC lung", a veritable "induced post-agressive lung" must be placed in the group of refractory hypoxemia of which it represents one of the most typical pictures.
 ...
PMID:[Pulmonary complications after extracorporeal circulation. ECC lung syndrome]. 1 38

Oxygen availability during cardiopulmonary bypass was assessed in 22 patients under hypothermic and relatively normothermic conditions. The patients were divided into two groups, 17 of whom received ACD blood and 5, CPD blood. The mean P50 for all patients fell from a preoperative value of 25.9 +/- 2.4 (SD) to 15.6 +/- 2.1 during hypothermia confirming a leftward shift of the oxyhemoglobin dissociation curve. Oxygen uptake, calculated from a-v oxygen content differences (avDO2) and flow, was significantly lower during hypothermic bypass (65 +/- 27 ml/min) than during rewarming (121 +/- 41 ml/min). The increase in oxygen affinity during hypothermia was influenced also by changes in acid base and 2,3-DPG concentrations, the changes being similar in both the ACD and CPD groups of patients. During rewarming, however, oxygen availability was increased in the CPD group presumably from significantly increased 2,3-DPG concentrations. A "functional" value of hemoglobin, based upon the effects of the shift of the oxyhemoglobin dissociation curve and, therefore, reflecting the true capacity of hemoglobin to unload oxygen at the tissue level, was calculated. During the hypothermic phase of bypass, this functional hemoglobin was only 4.2 g/100 ml blood, suggesting that, in spite of reduced metabolic demands, oxygenation reserves are minimal.
 ...
PMID:Oxygen availability during hypothermic cardiopulmonary bypass. 1 30

This study tests the hypothesis that postischemic myocardial depression can be reduced by providing an initial reperfusate pH which is appropriate for myocardial temperature (i.e., metabolic systems function optimally when pH is kept slightly alkaline to the neutral point, which changes with temperature in concordance with the pK of water). Ten dogs underwent 1 hour of ischemic arrest with topical hypothermia (intramyocardial temperature 16+/-2 degrees C). The initial reperfusate (500 cc of blood from the extracorporeal circuit) was infused (100 cc/minute) into the proximal aorta just before removing the cross-clamp. Reperfusate pH was kept at 7.4 in five dogs (control) and raised to 7.8 with THAM [tris (hydroxymethyl) aminomethane] in five dogs. Measurements 30 minutes after reperfusion showed that raising reperfusate pH to 7.8 resulted in (1) higher subendocardial blood flows (109+/-20 vs 61 cc+/-8 cc/100 gm/minute), (2) redistribution of postischemic blood flow toward the subendocardium (endocardial/epicardial flow 1.25+/-0.1 vs 1.0+/-0.03), (3) higher left ventricular oxygen uptakes (0.046 vs 0.033 cc/100 gm/beat), (4) better postischemic left ventricular compliance (56+/-3% more compliant), and (5) improved left ventricular performance (88+/-7% recovery vs only 57+/-3% recovery at pH 7.4). Postischemic edema (2% water gain) was unchanged by pH modification. We conclude that initial reperfusion with the appropriate pH provides an optimal milieu for restoration of cellular metabolism, counteracts the acidosis of ischemia, and improves postischemic left ventricular blood flow, distribution, oxygen uptake, compliance, and performance.
 ...
PMID:Studies on myocardial reperfusion injury. I. Favorable modification by adjusting reperfusate pH. 1 28

The well known effects of the lowering of the intraerythrocyte 2, 3, diphosphoglycerate (2, 3, DPG) level and hypothermia, on the affinity of oxygen for hemoglobin, lead the authors to study the influence of these parameters on this affinity during general anesthesia. The following observations were made in 15 adult subjects, undergoing prolonged general anaesthesia (average time: 3 hrs. 10 minutes): the dissociation curve of oxyhemoglobin (DCO) by the method of mixing, the intraerythrocyte 2,3, DPG level, the hemoglobin concentration and arterial blood parameters (PO2, PCO2, pH). These measurements were recorded before and after the general anaesthesia. The results were the following: a significant reduction of P50, measured under standard conditions (from 27.64 +/- 1.74 torr to 25.57 +/- 2.28, p less than or equal to 0.01) associated with a decrease in 2,3, DPG (from 0.94 +/- 0.31 mol/mol Hb at 0.64 +/- 0.24 p less than 0.01). Among the factors responsible for this variation in the affinity, it was proved that the volume of blood transfused was of importance as well as a decrease in body temperature during the operation. When the temperature is made to vary from 37 degrees C to 35 degrees C. the P50 ranges from 25.57 +/- 2.28 to 22.86 +/- 0.97 (p less than 0.01). To conclude the authors underline the importance of hypothermia and the volume of blood transfused (average time of preservation = 15 days) on the effects of the affinity of oxygen for hemoglobin.
 ...
PMID:[Changes in the affinity of oxygen for hemoglobin during general anesthesia]. 2 19

The physiological effects and certain aspects of cardiac metabolism were studied in 14 patients undergoing primary aortic valve replacement. The operations were performed under moderate hypothermia (30 degrees +/- 2 degrees C) and blood for coronary perfusion was taken from a sidebranch of the arterial line. The majority of the hearts went spontaneously into ventricular fibrillation at some stage of the operation. In spite of the high resistance measured in the coronary perfusion cannulae, an intraluminar coronary blood flow of 380 ml/min was recorded. The myocardial oxygen uptake decreased to 6.0 ml/min at 29 degrees C compared with 20.0 ml/min at 36 degrees C. The elevated coronary sinus lactate throughout the period of coronary perfusion and the increasing level of ASAT-enzyme indicated that this technique could not fully protect the myocardium from ischaemic changes. One patient died of myocardial infarction and two others needed vasopressor support postoperatively, in spite of documented effective coronary perfusion throughout the procedure. Cannulation of the coronary sinus is a valuable adjunct for the study of cardiac metabolism during ECC and it was accomplished without complications.
 ...
PMID:Myocardial protection during aortic valve replacement. Physiological and metabolic effects of selective coronary perfusion on the fibrillating heart. 3 82


1 2 3 4 5 6 7 8 9 10 Next >>