Simple dehydration from not drinking may lead to shock. b. Cardiogenic shock results in a collapse of the circulatory system secondary to pump failure. In this shock, left ventricular systole has failed and is not able to maintain cardiac output. It is the inability of the left ventricle to pump blood out to the body. This results in a decrease in cardiac output, decreased blood pressure and decreased organ perfusion and injury. This is most often caused by a myocardial infarction. In any shock state, arteries vasoconstrict. In cardiogenic
7 shock this increases the workload of the already failing left ventricle and makes it more difficult for the left ventricle to pump blood and worsens the shock state. c. Sepsis is most commonly caused by gram positive bacteria, follow by gram negative bacteria. The infective agent triggers a systemic vasodilation. The problem is not a loss of volume but rather the vascular system has expanded; thus, the available volume is insufficient to completely fill the vascular system. Gram- negative bacteria have endotoxins which are released when they are killed and this makes the septic shock worse, when it is caused by a gram negative bacteria. Antibiotics do not have any effect on endotoxins and they trigger a massive inflammatory and immune reaction. The classification of sepsis changed in early 2016. The classifications of SIRS, Sepsis, Severe Sepsis, and Septic Shock, presented in the text book no longer apply. You are not responsible for knowing these particular classifications of sepsis or the new classification of sepsis. d. Neurogenic shock results from a widespread vasodilation caused by an imbalance between the sympathetic and parasympathetic nervous systems. In normal physiology, the sympathetic nervous system opposes the effects of the parasympathetic nervous system. It increases the heart rate, decreases digestion and causes vasoconstriction. An imbalance between the two systems causes neurogenic shock. The issue with this type of shock is not with loss of volume. The volume has not changed. The tank (vasculature) has just gotten bigger and the volume is not enough to fill the tank. It may be caused by trauma to the spinal cord or dysfunction of the medulla. Severe general trauma may cause this as well. e. Anaphylactic shock results from a pathologic immune and inflammatory reaction to an antigen. In this type of shock, the individual experiences a significant allergic reaction to an antigen which results in a systemic inflammatory process and a widespread vasodilation. This occurs as a result of the release of products of inflammation, mainly histamine. This is an example of a type I hypersensitivity reaction which is IgE mediated reaction.
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