Shock, Pathology of Different Types, Animation

(USMLE topics, cardiology) Types of circulatory shock: hypovolemic, cardiogenic, obstructive, distributive (septic, anaphylactic and neurogenic), pathophysiology, signs, symptoms, presentation and diagnosis.

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Shock, also called circulatory shock, is a life-threatening clinical state characterized by body-wide deficiency of blood supply, causing oxygen deprivation, buildup of waste products, and eventual organ failure if untreated.
Shock may have different causes and hence its classification into different types:
Hypovolemic, or low volume shock happens when the circulating blood volume is severely reduced. This can be caused by:
External blood loss, such as after an injury,
Internal blood loss such as that results from a ruptured blood vessel, ruptured ectopic pregnancy, pancreatitis …
Or fluid loss from major burns, excessive vomiting, diarrhea or urination.
Cardiogenic shock occurs when the heart fails to pump sufficiently. This can result from a sudden heart attack, or an end-stage development in various heart conditions.
Obstructive shock is caused by an obstruction of blood flow in a major circulatory circuit.
Distributive shock results from excessive dilation of blood vessels, or vasodilation, which decreases blood pressures. Distribution shock can have different causes, the most common being sepsis, anaphylaxis and damage to the central nervous system (neurogenic):
In sepsis, the immune system is overwhelmed by an infection that gets out of control, and responds with a systemic cytokine release that causes vasodilation and fluid leakage from capillaries.
In anaphylaxis, the immune system overreacts to an allergen, releasing massive amounts of histamine, which has similar effects to cytokines. Peanut allergy is a common cause of anaphylaxis.
Neurogenic shock typically occurs as a result of a spinal cord injury. As the autonomic nervous system is damaged, the sympathetic tone that normally keeps blood vessels constricted is lost, causing vasodilation and hypotension.
Common symptoms of shock include low blood pressures and signs of organ damage such as confusion, reduced urine output and cold, sweaty, mottled or bluish skin, although distributive shocks due to sepsis or anaphylaxis may initially produce warm or flushed skin. This is because the infection in sepsis usually comes with fever, and the allergic reaction in anaphylaxis is accompanied by hives. Distributive shocks may also differ from other types of shock by having, at least initially, normal or high cardiac output.
As the body tries to compensate for hypotension, fast heart rates and rapid breathing may be observed. Diagnosis may also be assisted by blood tests for blood lactate levels. This is because in the absence of oxygen, the body switches to an alternative way of producing cellular energy, called anaerobic metabolism, in which glucose is broken down only partially producing lactic acid. Blood tests may also indicate signs of organ damage, or infection in case of sepsis.
Shock is a medical emergency and requires immediate treatments which aim to increase blood pressures and treat the underlying cause.