Energy Reserves and Requirements
Posted by Surgery on Aug 8, 2008
The neonate and child differ significantly from the adult patient in the proportion of available metabolic reserves. Table 8-1 outlines the macronutrient reserves of the neonate, child, and adult in percentage of total body weight (14,15,16). Carbohydrate stores are limited in all age groups and afford only acute provisions when necessary. Lipid reserves, an important and efficient source of energy, are reduced in the neonate as compared with the adult and gradually increase with age. The most striking difference between the adult and pediatric patient is the quantity of stored protein. The protein reserve of the adult is nearly twice that of the neonate.
Tags: Avapro, Cardiopulmonary Critical Care and Shock, Energy Reserves, Isordil, Metabolism, Principles of Genetics, SorbitrateOXYGEN KINETICS : Aceon
Posted by Surgery on Jul 11, 2008
Oxygen Consumption
Oxygen-based metabolism is necessary to maintain cell life. The cellular milieu typically requires an oxygen tension of about 1 to 4 mm Hg to sustain baseline VO2 levels (1). Intravascular venous oxygen tensions of at least 20 mm Hg are required to maintain an appropriate oxygen gradient to achieve these minimal levels of intracellular oxygen tension (2). Oxygen is necessary to provide reduction of cytochromes A and A3 to allow oxidative phosphorylation to occur (Fig. 10-1) (3).
oxygen
Hypoxemia results in a decrease in the availability of oxygen to mitochondria. The consequence is inhibition of Krebs cycle activity with reduction in adenosine triphosphate (ATP) production. With a decrease in perfusion, metabolism of other substrates such as glucose by the glycolytic pathway is necessary to maintain cellular metabolic processes. As ATP stores diminish, cellular synthetic and transport functions become impaired and eventually stop. With continued hypoxia, mitochondrial and endoplasmic reticulum swelling is observed, and lysosomal rupture and intracellular proteolysis follow.
Tags: Aceon, Cardiopulmonary Critical Care and Shock, OXYGEN KINETICS, Scientific Principles
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