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Disturbances in peripheral O extraction can be produced in dogs treated with 2 endotoxin and thereby provide an opportunity to test theories for the origin of pathological O supply dependency or to try different treatment modalities. The 2 most serious deficiency in the current animal models is the inability to mimic the increased O demand that is observed in patients at 02 delivery rates in excess of 2 normal. A particular feature of this increased O demand is that it apparently does 2 not stimulate increased 02 extraction, although the limitation in O extraction has 2 not been explored in patients by lowering 02 supply, for obvious reasons. At least two possibilities to account for increased 02 demand could be investigated in animal models, however. The amount of 02 that is utilized in extramitochondrial pathways, which is normally on the order of 10%, may be greatly increased in ARDS and sepsis by O radical formation. There is presently no information 2 concerning how much 02 might be used in this way. Another strong possibility is that mitochondrial injury, perhaps as a result of 02 radical formation, uncouples oxidative phosphorylation. Some evidence presently in the literature supports this idea [19]. Indeed, the association of increased blood lactate levels with higher than expected 02 demands makes uncoupling a very attractive hypothesis that warrants further investigation in animal models using such agents as 2,4-dinitrophenol. References 1.
List of contents
Intracellular Oxygen Supply: Implications for Intensive Care.- NMR Investigations of Cardiac Metabolism.- Evaluation of Tissue Hypoxia by Optical Methods.- Application of NIR Spectroscopy to Problems of Tissue Oxygenation.- Principal Determinants of Tissue PO2: Clinical Considerations.- Cellular Metabolic Consequences of Altered Perfusion.- Vascular Response to Hypoxia.- Blood Rheology Factors and Capillary Blood Flow.- Physiological and Pathological Oxygen Supply Dependency.- Oxygen Delivery and Utilization in Acute and Chronic Disease.- Oxygen Transport and Uptake in Health and Disease.- Multiple Organ Oxygen Supply-Demand Relationships and Redistribution of Flow.- The Determinants of Maximun Oxygen Utilization: The Role of Hemoglobin Concentration.- Oxygen Cost of Breathing.- Myocardial Oxygen Metabolism in the Sepsis Syndrome.- Tissue Oxygen Utilization in Septic Shock.- Oxygen Supply Dependency in Septic Shock.- Cellular Metabolism in Sepsis.- Multiple Organ Failure: Is It Only Hypoxia?.- Oxygen Demand/Supply Relationship: Role of Hormonal Influences.- The Value of Blood Lactate Monitoring in Clinical Practice.- Clinical Assessment of Tissue Oxygenation: Value of Hemodynamic and Oxygen Transport Related Variables.- Therapeutic Implications of Oxygen Transport in Critically Ill Patients.- The Effects of Anesthesia on Tissue Oxygen Balance.- Clinical Use of Continuous Mixed Venous Oximetry.- Tissue Oxygen Tension Monitoring: Relation to Hemodynamic and Oxygen Transport Variables.- Measurement and Control of Tissue Oxygen Tension in Surgical Patients.- Conditions Associated with Impaired Oxygen Extraction.
