Shock Flashcards
Day 2
Define shock
Acute medical condition associated with a fall in blood pressure as the circulatory system fails to supply sufficient blood to peripheral tissues. Characterized by rapid pulse, irregular breathing and dilated pupils.
What are the 5 types of shock
Amount (hypovolemic), neurogenic, septic, cardiogenic, anaphylactic
Explain hypovolemic shock
Reduction in fluid, either caused by intravascular or extravascular loss.
Intra - via whole blood loss (shot), concealed (internal blood loss), plasma loss through sweating, burns, dehydration.
Extra - fluid loss but not from blood vessel, renal (urine), GIT(diarrhoea or vomit)
Explain neurogenic shock
nerves supplying to the blood vessels are malfunctioning, so they dilate, causing poor pressure and tissue profusion. Seen in patients with spinal cord injuries.
Explain anaphalactic shock
immune system reacts to an allergen, release of histamine causes vasodilation so poor pressure / flow.
Explain septic shock
sepsis the immune system kills the bacteria which then releases endotoxins which release cytokinin’s which cause vasodilation and loss of pressure.
Explain cardiogenic shock
shock generated by the heart
* Decrease in contractility
* Decrease in preload eg in MI or RV
* Dysthymias – rhythm of heart poor so not getting an output
* Seen in patients in AF
* There no forward flow of blood.
What is the difference between compensated and non compensated shock ?
Compensated – occurs early while the body is still able to compensate for a shortfall in one or more of the 3 areas of perfusion.
Uncompensated – occurs when compensatory mechanisms fail and the patient’s condition deteriorates.
Explain the pathophysiology of cardiogenic shock
1- The myocardium cannot contract sufficiently, stroke volume decreases. Pulmonary congestion – blood backs up behind the weakened left ventricle, increasing preload and causing pulmonary congestion. Compensation – drop in stroke volume (volume of blood pumped from left ventricle per beat), heart becomes tachycardic to maintain cardiac output. Diminished stroke volume – due to low stroke volume, coronary artery perfusion and collateral blood flow decreases.
Increased workload – all of the mechanisms increases workload and enhance left sided heart failure. End result is myocardial hypoxia, further decreased cardiac output, and activation of compensatory mechanisms to prevent decompensation and death.
Explain pathophysiology of anaphylactic shock
3- Reexposure to allergen through cross link with mast cell or basophil, results in cellular degranulation and de novo synthesis of mediators. IgE binds to antigen which then activates FCeri receptors on mast cells and basophils. Inflammatory mediators released (histamine). Histamine binds to receptors H1 which causes anaphylaxis symptoms. Prostaglandin D2 mediates bronchospasm and vascular dilation. Leukotriene C4 is converted into LTD4 and LTE4r which are mediators of hypotension, bronchospasm, and mucus secretion and act as chemotactic signals for eosinophils and neutrophils.
Explain the pathophysiology of septic shock
Microorganisms invade body tissues, inflicting an immune response which provokes activation of biochemical cytokines and mediators associated with the inflammatory response. Increased capillary permeability and vasodilation interrupt body’s ability to provide adequate perfusion, oxygen, nutrients to tissues and cells. Proinflammatory and anti-inflammatory cytokines are released, coagulation system is activated which forms clots whether there is bleeding or not.
Explain pathophysiology of neurologic shock
5- Sympathetic stimulation causes vascular smooth muscle to constrict, and parasympathetic stimulation causes vascular smooth muscle to relax or dilate. Experience a predominant parasympathetic stimulation that causes vasodilation lasting for an extended period of time, leading to a relative hypovolemic state.Blood volume is adequate, because the vasculature is dilated; the blood volume is displaced, producing a hypotensive (low BP) state.The overriding parasympathetic stimulation that occurs with neurogenic shock causes a drastic decrease in the patient’s systemic vascular resistance and bradycardia.
Inadequate BP results in the insufficient perfusion of tissues and cells that is common to all shock states.
Explain the pathophysiology of hypovolemic shock
luid loss. Fluid loss can either be internal or external fluid loss.
Compensatory mechanism.The resulting drop in the arterial blood pressure activates the body’s compensatory mechanisms in an attempt to increase the body’s intravascular volume.
Venous return. Diminished venous return occurs as a result of the decrease in arterial blood pressure.
Preload. The preload or the filling pressure becomes reduced.
Stroke volume. The stroke volume is decreased.
Cardiac output.Cardiac output is decreased because of the decrease in stroke volume.
Arterial pressure.Reduced mean arterial pressure follows as the cardiac output gradually decreases.
Compromised cell nutrients. As the tissue perfusion decreases, the delivery of nutrients and oxygen to the cells are decreased, which could ultimately lead to multiple organ dysfunction syndrome.
