METABOLISM

METABOLISMSHOCKMetabolismCellular metabolism is based primarily on the hydrolysis of adenosine triphosphate (ATP).The majority of ATP is generated in our bodies through aerobic metabolism in the process of oxidative phosphorylation in the mitochondria.This process is dependent on the availability of O2 as a final electron acceptor in the electron transport chain.When oxidative phosphorylation is insufficient, the cells shift to anaerobic metabolism and glycolysis to generate ATP.This occurs via the breakdown of cellular glycogen stores to pyruvate. Additionally, under hypoxic conditions in anaerobic metabolism,pyruvate is converted into lactate, leading to an intracellular metabolic acidosis.Furthermore, acidosis leads to changes in calcium metabolism and calcium signaling.The depletion of ATP potentially influences all ATP dependent cellular processes. This includes maintenance of cellular membrane potential, synthesis of enzymes and proteins, cell signaling, and DNA repair mechanisms. Decreased intracellular pH also influences vital cellular functions such as normal enzyme activity, cell membrane ion exchange, and cellular metabolic signaling. Compounded, these changes may lead to irreversible cell injury and death.The relative underuse of glucose by peripheral tissues preserves it for the glucose-dependent organs such as the heart and brain.ENDPOINTS IN RESUSCITATIONSHOCKShock is defined as inadequate perfusion to maintain normal organ function. With prolonged anaerobic metabolism, tissue acidosis and O2 debt accumulate. The goal in the treatment of shock is restoration of adequate organ perfusion and tissue oxygenation. Resuscitation is complete when O2 debt is repaid, tissue acidosis is corrected, and aerobic metabolism is restored.