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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in cerebral cortex concentrations of high-energy phosphates, glycolytic metabolites, citric acid cycle intermediates, associated amino acids, and ammonia, were studied after 5, 15 and 30 min of incomplete ischemia in rats anesthetized with 70% N2O or 150 mg.kg-1 of phenobartibal. Previous results have shown that with this type of ischemia (bilateral carotid artery occlusion combined with reduction in blood pressure to 50 mm Hg) cortical blood flow is reduced to below 10% of nitrous oxide values, whether animals are anesthetized with 70% N2O or 150 mg.kg-1 of phenobarbital. In animals under 70% N2O, changes in tissue concentrations of phosphocreatine, ATP, ADP and AMP were similar to those previously obtained in complete ischemia. However, some glucose remained in the tissue, and the lactate concentrations gradually rose to reach excessive values. Changes occuring in glycolytic and citric acid cycle intermediates were similar to those seen in complete ischemia but, after 30 min, there was some reduction in the pool size of amino acids. In those animals given phenobarbital and which lost all EEG activity during ischemia, changes in cerebral metabolites were virtually identical to those observed in nitrous oxide-anesthetized animals. However, some animals exposed to 5 or 15 min of ischemia had some remaining EEG activity. In these, cerebral energy state was significantly less deranged, and levels of glycogen, glucose and pyruvate were higher.
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PMID:Effects of phenobarbital in cerebral ischemia. Part I: cerebral energy metabolism during pronounced incomplete ischemia. 2 84

In studies in the isolated rat heart that were designed to optimize the composition of the infusion conditions for a cardioplegic protective solutuin, we have observed a complex relationship between the duration and volume of infusion and the extent of tissue protection. Our results would indicate that solutions, such as that formulated at St. Thomas' Hospital, which are based on extracellular electrolyte content, afford (after a brief equilibration period) a constant degree of protection, irrespective of infusion volume or duration. In contrast other solutions, such as the Bretschneider solution, which have extremes of electrolyre concentration, are associated with a complex dose-response relationship. In the latter instance, infusion of small volumes for short durations affords an increasing degree of protection against ischemia. Increasing the infusate volume may result in a progressive loss of protection. Excessive infusion may lead to an exacerbation of ischemia-induced damage. Our studies suggest that the relative patterns and rates of re-equilibration of various ions, especially sodium and calcium, during infusion may play a major role in determining the efficacy of the infusate.
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PMID:Protection of the ischemic myocardium. Volume-duration relationships and the efficacy of myocardial infusates. 2 95

Rats with different levels of blood glucose concentration were exposed to 10 min of complete brain ischemia achieved by compression of neck vessels by a pneumatic cuff. All normoglycemic rats survived the ischemic period and made the best clinical recovery. Hyperglycemic rats died within 12 h. Seizure activity was observed in all animals in this group. Three of eight hypoglycemic rats died between 3 and 16 days. The clinical recovery was less complete than in the control group. Thus, recovery from cerebral ischemia depends upon preischemic blood glucose concentration. Hyper- and hypoglycemia hamper the clinical recovery after transient cerebral ischemia.
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PMID:Clinical restitution following cerebral ischemia in hypo-, normo- and hyperglycemic rats. 3 Feb 50

The relevance of two direct techniques for monitoring of cellular function during tissue hypoxia has been evaluated. Tissue pH and cellular transmembrane potentials were registered in canine skeletal muscle during intestinal exteriorization shock and during prolonged local tourniquet ischemia. The obtained pH and transmembrane potential changes were correlated to simultaneous changes in high-energy phosphagen (ATP + CP) and lactate levels in skeletal muscle. In control dogs no significant changes in either of the studied variables occurred. Intestinal exteriorization shock as well as local tourniquet ischemia resulted in a gradual increase in tissue lactate and a concomitant decrease in tissue pH and transmembrane potentials. In both experimental situations there was a close correlation between the transmembrane potential reduction and the tissue lactate increase. Tissue pH registrations, on the other hand, did not similarly reveal the full extent of the tissue lactate increase under the two experimental conditions. Possible reasons for this discrepancy are discussed. On the basis of the present results it may therefore be concluded that the transmembrane potential seems to be a better variable for revealing the full extent of cellular metabolic deterioration during various situations with tissue hypoxia.
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PMID:Correlation between tissue pH, cellular transmembrane potentials, and cellular energy metabolism during shock and during ischemia. 3 May 43

The direct and indirect actions on left ventricular dynamics of contrast material (sodium meglumine diatrizoate) currently used for coronary arteriography, modified ionic material (sodium meglumine calcium metrizoate) and non-ionic material (metrizamide) were assessed in conscious and anesthetized dogs. In both anesthetized and conscious animals, the diatrizoate compound caused an early (3--10 sec after injection) decrease in peak dp/dt and dp/dt/LVP40, followed by late (10--20 sec after injection) increases in these variables. The predominant early and later effects of the calcium metrizoate compound were increases in parameters of LV contractile state. Metrizamide produced no significant early alterations, but later induced a small increase in these variables. The positive inotropic actions of each of the contrast materials were attenuated by beta adrenergic blockade. The early effects of the contrast materials were similar in the presence of segmental ischemia. The late positive inotropic effects in response to the diatrizoate compound and metrizamide were not observed in the ischemic state, while the positive inotropic response induced by the calcium metrizoate compound was significantly reduced. Thus intracoronary administration of sodium meglumine diatrizoate produced direct myocardial depression, followed by adrenergically mediated myocardial stimulation. Calcium metrizoate caused prominent direct and adrenergically mediated augmentation in contractile state. Metrizamide induced the least alteration in LV contractile state.
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PMID:Direct and reflex myocardial effects of intracoronary administered contrast materials in the anesthetized and conscious dog: comparison of standard and newer contrast materials. 3 Jul 33

Hind legs of dogs were amputated at the middle of the thigh and preserved in three different conditions: in ice water, in a refrigerator, and at room temperature. After 6 or 12 hours of ischemia, recirculation was established. The survival rate of the animals was observed and measurement of limb edema, potassium, pH, and lactate in the blood was performed to study the effects of hypothermia on prevention of "replantation toxemia." Cooling of the amputated limb was effective for prevention of toxemia, and the cooling effect was greater in ice water than in a refrigerator. However, when cooled in ice water, some animals died due to toxemia when the time of ischemia was prolonged to 12 hours. In the dead animals, a close relationship was observed between the developement of toxemia and metabolic acidosis due to the increase in lactate.
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PMID:An experimental study on "replantation toxemia". The effect of hypothermia on an amputated limb. 3 78

Cerebral blood flow (CBF) was studied in non-exteriorized near-term sheep fetuses using the radioactive microsphere technique. By partially occluding the umbilical vessels for a period of 1--1 1/2 hours a progressive and severe asphyxia with a final arterial pH of 6.90 was achieved. Varying the mean arterial blood pressure in the fetuses by blood withdrawal or infusion in this state, CBF was measured at different perfusion pressures (mean arterial blood pressure (MABP) minus central venous pressure (CVP)). A passive flow/pressure relationship--loss of autoregulation--was found, with hyperemia reaching CBF values up to 6 times normal at normal MABP of about 60 to 70 mmHg, and severe ischemia reaching CBF values close to zero in large cortical areas at MABP of 30 mmHg. CVP remained essentially unchanged at 10--15 mmHg. The severe and prolonged asphyxia rendered the blood-brain barrier leaky to the albumin tracer Evans blue. In four other fetuses umbilical cord clamping was omitted. However, only in one of these cases was acidosis completely avoided, and CBF autoregulation maintained. The three other fetuses were acidotic at the end of the surgical procedure and had impaired autoregulation.
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PMID:Pressure passive cerebral blood flow and breakdown of the blood-brain barrier in experimental fetal asphyxia. 3 59

The effect of propranolol on the function of the heart, its hemodynamics and metabolism was studied on dogs and rats. It was established that propranolol-induced block of the beta-adrenergic receptors is conducive to a decrease in the intensity of myocardial metabolism and increase of myocardial tolerance to ischemia.
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PMID:[Increase in myocardial resistance to ischemia by excluding the heart from the circulation by using a beta-adrenergic receptor block]. 3 48

The protective effect of thiopental on neurological lesions provoked by cerebral anoxie was studied in the monkey. Cerebral ischemia was induced by a cervical tourniquet applied for a period of 16 minutes. A control series of 10 animals received only the normal resuscitation. A series of 27 monkeys received either 90 mg/kg of thiopental at 5, 10, 15, 30 or 60 minutes following ischemia, or 120 mg/kg at the 30th or 60th minute. One third of the dose was administered within 5 minutes and the rest during the following 55 minutes. The results shows that the prevention, by thiopental, of the clinical and histological lesion secondary to cerebral anoxia is effective when this drug is administered before the 15th minute. With 90 mg/kg administered at the 30th or 60th minute the improvement was slight: with 120 mg/kg it was greater if the injection was given at the 60th rather than at the 30th minute. These results, along with the mechanisms which may explain the action of thiopental, are discussed.
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PMID:[Experimental study of barbiturate application following anoxic encephalopathy]. 3 54

Intramuscular tissue pO2, pCO2, and pH were monitored distal to a pneumatic tourniquet in a dog hindleg preparation. A severe state of tissue hypoxia, hypercarbia, and acidosis was quantitated. The recovery time for tissue gases following release increased with increasing tourniquet time. Elevated c.p.k. and lactic acid values were noted at 2 hours of ischemia, reflecting the muscle changes at that time. Histologic sections revealed early signs of degeneration by 1 hour which progressively increased with increased tourniquet ischemia. On the basis of this study, we conclude that ischemia should not exceed 1 to 1 1/2 hours if significant pathophysiologic tissue changes are to be avoided. If longer time is required, intermittent release of the tourniquet for 10 minutes at the end of each hour of inflation will avoid complications.
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PMID:Pathophysiologic effects distal to a tourniquet in the dog. 3 19


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