shock

shock
Is the most common and therefore the most important cause of death in surgical patients.
Definition shock is a systemic state of low tissue perfusion which is in adequate for normal cellular respiration with insufficient delivery of oxygen and glucose, cells switch from aerobic to anaerobic metabolism.
If perfusion is not restored in a timely fashion, cell death ensues.
Pathophysiology
1-cellular as perfusion to tissues is reduced; cells are deprived from oxygen and must switch from aerobic to an aerobic metabolism. The product of anaerobic metabolism is not carbon dioxide but lactic acid, the accumulation of lactic acid in blood cause systemic metabolic acidosis.
As glucose within the cells exhausted, anaerobic respiration ceases and failure of sodium and potassium pump in the cell membrane and intracellular organelles.
Intracellular contents, including potassium released into blood stream.
2-microvascular as tissue ischemia progress, there will be activation of immune and coagulation system. Hypoxia and acidosis activate complement and prime neutrophils resulting in generation of oxygen free radicals and cytokines release. Which lead to injury to capillary endothelial cells. Damaged endothelium loses its integrity and becomes (leaky). Fluid leak out and tissue oedema ensues, exacerbating cellular hypoxia.
3-systemic
Cardiovascular as preload and afterload decrease, there is compensatory baroreceptor response resulting in increased sympathetic activity and release of catecholamine into the circulation, this result in tachycardia and systemic vasoconstriction (except in sepsis)
Respiratory the metabolic acidosis and increased sympathetic response result in increased respiratory rate and minute ventilation to increase excretion of CO2 and so produce compensatory respiratory alkalosis.