NORMAL cell metabolism and function depend on the constant presence of adequate amounts of oxygen within the cell. The amount of molecular oxygen in tissue (ie, tissue oxygen tension) is determined by a host of interrelated factors under normal conditions:
Coefficient of oxygen diffusion
Rate of delivery of oxygen to tissue
Amount of oxygen in arterial blood
Alveolar oxygen tension
Oxygen tension in inspired air
Alveolar ventilation
Ventilation: perfusion ratio
Pulmonary diffusion capacity
Solubility of oxygen in plasma
Amount of hemoglobin
Rate of delivery of arterial blood to tissues
Cardiac output
Blood pressure
State of peripheral vasculature (vasoconstricted or vasodilated)
Arterio-venous shunts
Rate at which oxygen leaves blood
Oxygen dissociation curve
Oxygen solubility in plasma
Rate of consumption of oxygen by tissue
Work
Drugs
Endocrine
Epinephrine
Corticosteroids
Thyroxine
Insulin
Temperature
Under conditions as physiologically and pharmacologically complex as clinical anesthesia, the determinants of tissue oxygenation become even more complex. Some
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