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18.9A: Types of Shock

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    Circulatory shock is a life-threatening medical condition that occurs due to inadequate substrate for aerobic cellular respiration.

     

    LEARNING OBJECTIVES

     

    Differentiate among the types of shock

     

    KEY TAKEAWAYS

    Key Points

     

    • Circulatory shock, commonly known simply as shock, is a life-threatening medical condition that occurs due to the provision of inadequate substrates for cellular respiration.Typical symptoms of shock include elevated but weak heart rate, low blood pressure, and poor organ function, typically observed as low urine output, confusion, or loss of consciousness.
    • There are four subtypes of shock with differing underlying causes and symptoms: hypovolemic, cardiogenic, obstructive, and distributive.
    • Distributive shock can be further divided into septic, anaphylaxis, and neurogenic shock.

     

    Key Terms

     

    • shock: A medical condition that occurs due to an inadequate supply of substrates required for aerobic respiration by the bodies tissues.

    Circulatory shock, commonly known simply as shock, is a life-threatening medical condition that occurs due to inadequate substrates for aerobic cellular respiration. In the early stages, this is generally caused by an inadequate tissue level of oxygen. The typical signs of shock are low blood pressure, a rapid heartbeat, and signs of poor end-organ perfusion or decompensation (such as low urine output, confusion, or loss of consciousness). In some people with circulatory shock, blood pressure remains stable.

    This schematic of the manifestation of shock includes vasoconstriction, failure of precapillary sphincters, peripheral pooling of blood, inadequate perfusion, cell hypoxia, energy deficit, lactic acid accumulation and fall of pH, anaerobic metabolism, metabolic acidosis, cell membrane dysfunction and failure of sodium pump, intracellular lysosomes release digestive enzymes, efflux of potassium, influx of sodium and water, toxic substances enter circulation, capillary endothelium damage, destruction, dysfunction, and cel death.

     

    Shock: The scheme depicts the cell metabolic response as a result of inadequate blood delivery during circulatory shock.

    The presentation of shock is variable with some people having only minimal symptoms such as confusion and weakness. While the general signs for all types of shock are low blood pressure, decreased urine output, and confusion, these may not always be present. Specific subtypes of shock may have additional symptoms.

     

    Hypovolemic Shock

     

    Hypovolemic shock, the most common type, is caused by insufficient circulating volume, typically from hemorrhage although severe vomiting and diarrhea are also potential causes.

    Hypovolemic shock is graded on a four-point scale depending on the severity of symptoms and level of blood loss. Typical symptoms include a rapid, weak pulse due to decreased blood flow combined with tachycardia, cool, clammy skin, and rapid and shallow breathing.

     

    Cardiogenic Shock

     

    Cardiogenic shock is caused by a failure of the heart to pump correctly, either due to damage to the heart muscle through myocardial infarction or through cardiac valve problems, congestive heart failure, or dysrhythmia.

     

    Obstructive Shock

     

    Obstructive shock is caused by an obstruction of blood flow outside of the heart. This typically occurs due to a reduction in venous return, but may also be caused by blockage of the aorta.

     

    Distributive Shock

     

    Distributive shock is caused by an abnormal distribution of blood to tissues and organs and includes septic, anaphylactic, and neurogenic causes.

     

    Septic

     

    Septic shock is the most common cause of distributive shock and is caused by an overwhelming systemic infection that cannot be cleared by the immune system, resulting in vasodilation and hypotension.

     

    Anaphylactic

     

    Anaphylactic shock is caused by a severe reaction to an allergen, leading to the release of histamine that causes widespread vasodilation and hypotension.

     

    Neurogenic

     

    Neurogenic shock arises due to damage to the central nervous system, which impairs cardiac function by reducing heart rate and loosening the blood vessel tone, resulting in severe hypotension.