Guyton and Hall Physiology Chapter 24 - Circulatory Shock and its Treatment
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Questions and Answers

What characterizes the nonprogressive stage of shock?

  • The heart rate drops significantly.
  • The body’s compensatory mechanisms can restore normal circulatory function. (correct)
  • Immediate intervention is required for recovery.
  • Blood volume must be restored externally.

    • Which stage of shock is described as being progressively worse without intervention?

  • Nonprogressive stage
  • Compensated stage
  • Irreversible stage
  • Progressive stage (correct)

    • What is the primary effect of sympathetic reflexes during shock?

  • Decreased heart rate to conserve blood
  • Increased arteriolar constriction in systemic circulation (correct)
  • Increased metabolic rate in tissues
  • Increased blood flow to the extremities

    • In which situation does the heart rate significantly increase during shock?

    <p>Due to compensatory mechanisms in response to diminished blood volume</p> Signup and view all the answers

    At what point in shock does the body lose the ability to recover despite existing therapies?

    <p>In the irreversible stage</p> Signup and view all the answers

    What is a significant consequence of venous constriction during shock?

    <p>Maintenance of venous return despite decreased blood volume</p> Signup and view all the answers

    What ultimately happens to arterial blood pressure as shock progresses?

    <p>It begins to drop drastically after significant blood volume loss.</p> Signup and view all the answers

    Which mechanism primarily initiates sympathetic reflexes in shock?

    <p>Arterial baroreceptors and vascular stretch receptors</p> Signup and view all the answers

    At what arterial pressure level does recovery from shock begin to slow?

    <p>45 mm Hg</p> Signup and view all the answers

    What role does angiotensin II play during hemorrhagic shock?

    <p>It constricts peripheral arterioles</p> Signup and view all the answers

    What is a critical threshold for arterial pressure below which life cannot be sustained?

    <p>45 mm Hg</p> Signup and view all the answers

    What hormonal response increases during shock to help constrict blood vessels and retain water?

    <p>Vasopressin</p> Signup and view all the answers

    What happens to animals whose arterial pressures are bled rapidly to levels above 45 mm Hg?

    <p>They may recover, depending on the extent of pressure reduction.</p> Signup and view all the answers

    Which of the following is NOT a compensatory mechanism during hypovolemic shock?

    <p>Vasodilation of peripheral vessels</p> Signup and view all the answers

    Which physiological change occurs with increased secretion of epinephrine during shock?

    <p>Increased heart rate</p> Signup and view all the answers

    What typically indicates that shock is becoming progressive?

    <p>Further blood loss crosses a critical threshold</p> Signup and view all the answers

    What is a possible outcome for animals with injuries that keep arterial pressure levels just above 45 mm Hg?

    <p>Hovering between life and death for hours.</p> Signup and view all the answers

    What ultimately leads to death in an animal experiencing severe hemorrhage?

    <p>A critical fall below 45 mm Hg in arterial pressure</p> Signup and view all the answers

    What is the initial stage of septic shock characterized by?

    <p>Signs of bacterial infection without circulatory collapse</p> Signup and view all the answers

    Which type of bacteria is most commonly responsible for causing septic shock?

    <p>Gram-positive bacteria</p> Signup and view all the answers

    What physiological mechanism primarily mediates compensatory responses in shock?

    <p>Diminished sympathetic actions</p> Signup and view all the answers

    In which phase of shock does plasma loss into tissues through deteriorating capillary walls occur?

    <p>Progressive stage of shock</p> Signup and view all the answers

    How can full circulatory function often be restored in the treatment of shock?

    <p>Through sympathetic drug administration</p> Signup and view all the answers

    What is a primary effect of decreased cardiac output during circulatory shock?

    <p>Decreased arterial pressure</p> Signup and view all the answers

    Which mechanism is primarily responsible for tissue ischemia during shock?

    <p>Decreased nutrition of tissues</p> Signup and view all the answers

    What happens to vasomotor activity during circulatory shock?

    <p>It decreases</p> Signup and view all the answers

    What is a common clinical treatment option for patients experiencing hypovolemic shock?

    <p>Fluid resuscitation</p> Signup and view all the answers

    Increased capillary permeability during shock is most likely to result in which of the following?

    <p>Edema and tissue swelling</p> Signup and view all the answers

    What is one potential consequence of decreased venous return during shock?

    <p>Worsening cardiac function</p> Signup and view all the answers

    What type of shock is primarily characterized by decreased blood volume?

    <p>Hypovolemic shock</p> Signup and view all the answers

    Which feedback mechanism can contribute to the progression of shock?

    <p>Increased capillary permeability</p> Signup and view all the answers

    Which pathophysiological change occurs in the vascular system during shock?

    <p>Decreased blood volume and vascular dilation</p> Signup and view all the answers

    What is one of the main factors leading to the decreased nutrition of brain tissues during shock?

    <p>Decreased systemic blood flow</p> Signup and view all the answers

    What is a primary physiological consequence of circulatory shock?

    <p>Inadequate delivery of nutrients to tissues</p> Signup and view all the answers

    Which of the following can lead to decreased cardiac output resulting in shock?

    <p>Myocardial infarction</p> Signup and view all the answers

    How can arterial pressure present a misleading measure of circulatory function in shock?

    <p>It can remain normal despite severe shock</p> Signup and view all the answers

    Which mechanism is a sympathetic reflex compensation during circulatory shock?

    <p>Increased heart rate</p> Signup and view all the answers

    What is a key characteristic of hypovolemic shock mechanisms?

    <p>Blood loss leading to reduced preload</p> Signup and view all the answers

    What is the first step in the clinical treatment of shock?

    <p>Restoration of circulating volume</p> Signup and view all the answers

    Which of the following best describes the pathophysiology of circulatory crisis?

    <p>Insufficient movement of blood to vital organs</p> Signup and view all the answers

    Which factor contributes to abnormal tissue perfusion in shock?

    <p>Improper nervous system regulation</p> Signup and view all the answers

    In the context of circulatory shock, what role do powerful nervous reflexes play?

    <p>They can maintain arterial pressure despite shock.</p> Signup and view all the answers

    What general condition can lead to the development of circulatory shock?

    <p>Inadequate blood flow due to various causes</p> Signup and view all the answers

    The mechanisms of angiotensin and vasopressin can respond completely in more than 60 minutes.

    <p>True</p> Signup and view all the answers

    Recovery from shock can take between 1 to 48 hours depending on the adjustment of blood volume.

    <p>True</p> Signup and view all the answers

    Arterial pressure remains unaffected by the reverse stress-relaxation in blood vessels.

    <p>False</p> Signup and view all the answers

    In progressive shock, cardiovascular deterioration is caused by a vicious cycle.

    <p>True</p> Signup and view all the answers

    The left atrial pressure rises without any influence from blood volume absorption.

    <p>False</p> Signup and view all the answers

    It takes only a few moments for the body to fully recover after experiencing shock.

    <p>False</p> Signup and view all the answers

    Shock may transition to a progressive stage if left untreated due to important feedback mechanisms.

    <p>True</p> Signup and view all the answers

    Oral ingestion of water and salt has no effect on recovery time from shock.

    <p>False</p> Signup and view all the answers

    Sympathomimetic drugs are ineffective in treating neurogenic shock.

    <p>False</p> Signup and view all the answers

    Complete cardiac arrest can sometimes be resolved using cardiopulmonary resuscitation procedures.

    <p>True</p> Signup and view all the answers

    Ventricular fibrillation is a condition where blood flow is maintained.

    <p>False</p> Signup and view all the answers

    Glucocorticoids may assist in glucose metabolism during severe cellular damage.

    <p>True</p> Signup and view all the answers

    Administering norepinephrine has no significant effects during a state of shock.

    <p>False</p> Signup and view all the answers

    Gas gangrene bacilli primarily cause an increase in arterial pressure during infection.

    <p>False</p> Signup and view all the answers

    Anaphylaxis results from an antigen-antibody reaction and often leads to decreased cardiac output.

    <p>True</p> Signup and view all the answers

    Histamine release during septic shock increases vascular capacity due to venous constriction.

    <p>False</p> Signup and view all the answers

    High fever is a common feature observed in septic shock.

    <p>True</p> Signup and view all the answers

    Micro-blood clots in septic shock are primarily caused by platelet aggregation in response to allergens.

    <p>False</p> Signup and view all the answers

    Marked vasodilation throughout the body is an effect of histamine release during anaphylaxis.

    <p>True</p> Signup and view all the answers

    Arteriolar dilation occurs in septic shock, likely resulting in high cardiac output in all patients.

    <p>False</p> Signup and view all the answers

    Septic shock can be categorized into a single type due to the uniformity of its causes.

    <p>False</p> Signup and view all the answers

    Severe neurogenic shock can develop from gas gangrene infections spreading through the body.

    <p>True</p> Signup and view all the answers

    In septic shock, the rapid loss of fluid and protein into tissue spaces is primarily due to decreased capillary permeability.

    <p>False</p> Signup and view all the answers

    The head-down position promotes venous return and increases cardiac output.

    <p>True</p> Signup and view all the answers

    The main requirement for a plasma substitute is that it can easily filter through capillary pores.

    <p>False</p> Signup and view all the answers

    Glucocorticoids are administered to patients in severe shock primarily to increase heart strength.

    <p>True</p> Signup and view all the answers

    Dextran can pass through capillary pores to provide colloid osmotic pressure.

    <p>False</p> Signup and view all the answers

    Oxygen therapy is universally beneficial for all types of shock.

    <p>False</p> Signup and view all the answers

    The only requirement for a plasma substitute is that it must be toxic.

    <p>False</p> Signup and view all the answers

    The administration of glucocorticoids helps control glucose metabolism.

    <p>True</p> Signup and view all the answers

    Too little delivery of oxygen to tissues is a major problem in shock.

    <p>True</p> Signup and view all the answers

    Dextrans are small molecules of glucose that can replace plasma proteins.

    <p>False</p> Signup and view all the answers

    Plasma substitutes can contain electrolytes to prevent derangement of the body's extracellular fluid.

    <p>True</p> Signup and view all the answers

    Whole blood is the most effective therapy for shock caused by plasma loss.

    <p>False</p> Signup and view all the answers

    Sympathomimetic drugs, such as epinephrine, are beneficial in treating hemorrhagic shock.

    <p>False</p> Signup and view all the answers

    Administration of an appropriate electrolyte solution can correct shock caused by dehydration.

    <p>True</p> Signup and view all the answers

    Plasma can effectively substitute for whole blood under battlefield conditions.

    <p>True</p> Signup and view all the answers

    Plasma substitutes are developed to perform functions similar to whole blood.

    <p>True</p> Signup and view all the answers

    In hypovolemic shock, a decrease in hematocrit below half of normal leads to serious consequences immediately.

    <p>False</p> Signup and view all the answers

    Sympathomimetic drugs have a vasodilating effect that counteracts histamine in anaphylactic shock.

    <p>False</p> Signup and view all the answers

    Epinephrine is ineffective against anaphylactic shock due to low histamine levels.

    <p>False</p> Signup and view all the answers

    Correcting shock often requires immediate administration of blood products.

    <p>True</p> Signup and view all the answers

    The circulatory reflexes during shock cause near-maximal activation of the sympathetic nervous system.

    <p>True</p> Signup and view all the answers

    Match the following terms related to hypovolemic shock with their definitions:

    <p>Hypovolemia = Diminished blood volume Hemorrhage = Common cause of hypovolemic shock Sympathetic reflexes = Help maintain arterial pressure Cardiac output = Amount of blood the heart pumps</p> Signup and view all the answers

    Match the following statements about blood volume loss to their corresponding effects:

    <p>15% to 20% blood volume loss = Possible without causing death 30% to 40% blood volume loss = Can occur with intact reflexes 10% blood volume removal = Almost no effect on arterial pressure Greater blood loss = First affects cardiac output</p> Signup and view all the answers

    Match the following physiological concepts with their relevant descriptions:

    <p>Arterial pressure maintenance = Lasts longer than cardiac output during hemorrhage Total peripheral resistance = Increased by sympathetic reflexes to maintain pressure Cardiac output decrease = Occurs before arterial pressure decreases Compensatory mechanisms = Help counteract the effects of shock</p> Signup and view all the answers

    Match the following percentages of blood volume loss to their consequences:

    <p>15% to 20% = Blood volume loss before death is possible without reflexes 30% to 40% = Loss sustained with intact reflexes 10% = Minimal impact on both arterial pressure and cardiac output Greater blood loss = Diminishes both cardiac output and arterial pressure</p> Signup and view all the answers

    Match the following effects of hypovolemic shock with the systems they primarily impact:

    <p>Sympathetic nervous system = Maintains arterial pressure more effectively Cardiovascular system = First to show effects from blood loss Circulatory system = Affected by hemorrhage reducing filling pressure Venous return = Decreased leading to reduced cardiac output</p> Signup and view all the answers

    Match the following factors with their roles during shock:

    <p>Sympathetic constriction = Keeps venous return stable Decreased oxygen = Triggers central nervous system response Central nervous system ischemic response = Stimulates sympathetic nervous system Arterial pressure maintenance = Protects coronary and cerebral blood flow</p> Signup and view all the answers

    Match the following pressure levels with their significance in shock:

    <p>50 mm Hg = Point of second plateau in arterial pressure curve 45 mm Hg = Critical threshold for recovery 0 mm Hg = Indicates severe hemorrhage 100 mm Hg = Normal arterial pressure level</p> Signup and view all the answers

    Match the following concepts with their explanations:

    <p>Last-ditch stand = Sympathetic reflex attempts to maintain pressure Progressive shock = Cycle leading to cardiovascular deterioration Vicious cycle = Continuous decline in circulation during shock Hemorrhage effects = Influences on cardiac output and arterial pressure</p> Signup and view all the answers

    Match the following responses with their triggers during shock:

    <p>Loss of oxygen = Activates central nervous system Excess carbon dioxide = Stimulates sympathetic system Volume decrease = Affects blood flow and pressure Sympathetic reflexes = Compensate for arterial pressure drops</p> Signup and view all the answers

    Match the following outcomes with their related mechanisms in shock:

    <p>Decreased coronary flow = Due to low arterial pressure Decreased cerebral perfusion = Caused by sympathetic responses Increased sympathetic activity = Response to low oxygen levels Compensatory mechanisms = Aim to maintain blood flow</p> Signup and view all the answers

    Study Notes

    Circulatory Shock Stages

    • Stage 1: Nonprogressive or compensated stage. Compensatory mechanisms return the body to normal without intervention.
    • Stage 2: Progressive stage. Shock worsens without therapy, leading to death.
    • Stage 3: Irreversible stage. Even with therapy, shock is too developed and the patient will die.

    Causes of Shock

    • Reduced Cardiac Output: Decreased heart function, like myocardial infarction, leads to lower blood flow and inadequate tissue oxygenation.
    • Reduced Blood Volume: Hemorrhage is the main cause, with the critical threshold being around 40-45% of blood volume loss.
    • Septic Shock: Widespread bacterial infection leading to tissue damage, often caused by Gram-positive and Gram-negative bacteria.

    Sympathetic Reflex Compensations in Shock

    • Increased peripheral resistance - vasoconstriction in most tissues.
    • Increased venous return - constriction of veins and venous reservoirs.
    • Increased heart rate - from 72 beats/minute to 160-180 beats/minute.
    • Reverse stress-relaxation - blood vessels constrict around the reduced blood volume, improving circulation.
    • Increased renin secretion and angiotensin II formation - causing peripheral vasoconstriction and reduced water/salt output by the kidneys.
    • Increased vasopressin secretion - vasoconstriction and increased water retention.
    • Increased epinephrine/norepinephrine secretion - vasoconstriction and increased heart rate.

    Progression of Shock

    • Decreased cardiac output leads to decreased arterial pressure, reduced systemic blood flow, and decreased tissue nutrition.
    • Decreased cardiac nutrition leads to decreased nutrition of the vascular system and vasoconstriction, leading to vascular dilation and venous pooling.
    • Intravascular clotting depletes the clotting factors, causing hemorrhage in multiple areas, including the intestinal tract.
    • Release of toxins adds to damage, worsening the progression of shock.

    Treatment of Shock

    • Restoring blood volume and blood flow is crucial.
    • Vasopressors are used to increase vasomotor activity, replacing the function of the weakened sympathetic nervous system.

    Mechanisms of Shock Recovery

    • The body has various mechanisms to recover from shock, each operating on different time scales.
    • The angiotensin and vasopressin systems, along with reverse stress-relaxation of blood vessels, take 10 to 60 minutes to fully respond.
    • These mechanisms increase arterial pressure and circulatory filling pressure, aiding blood return to the heart.
    • Blood volume readjustment, involving fluid absorption and intake, can take 1 to 48 hours.

    Progressive Shock and its Causes

    • Progressive shock is a worsening condition caused by a vicious cycle of cardiovascular deterioration.
    • The cycle begins with decreased cardiac output, leading to further decreases in output.
    • Various factors contribute to this cycle, including:
      • Reduced venous return
      • Reduced coronary blood flow
      • Reduced oxygen supply to the heart
      • Reduction in contractility of the heart muscle.
    • Positive feedbacks further worsen the situation.
    • Examples include reduced tissue perfusion, causing a decrease in cellular metabolism and ultimately, a decrease in cardiac output.

    Anaphylactic Shock and Histamine Shock

    • Anaphylaxis is a severe allergic reaction characterized by rapid antigen-antibody interaction leading to histamine release.
    • This release causes several adverse effects, including:
      • Increased vascular capacity due to venous dilation, reducing venous return
      • Dilation of arterioles, resulting in reduced arterial pressure
      • Increased capillary permeability, leading to fluid and protein leakage into tissues.

    Septic Shock

    • Septic shock refers to shock caused by a systemic infection.
    • It's categorized by several features, including:
      • High fever
      • Widespread vasodilation, particularly within infected tissues
      • High cardiac output in some patients, often due to arteriolar dilation and increased metabolic rate
      • Blood sludging due to red cell agglutination
      • Formation of micro-blood clots throughout the body.

    Treatment of Shock: Replacement Therapy

    • Replacement therapy is crucial in shock management because it addresses the underlying cause.
    • Hemorrhagic shock requires whole blood transfusion.
    • Plasma transfusion is appropriate for plasma loss.
    • Electrolyte solutions can correct dehydration.
    • Plasma substitutes like dextran solution can mimic the hemodynamic actions of plasma, providing colloid osmotic pressure.

    Treatment of Shock: Sympathomimetic Drugs

    • Sympathomimetic drugs mimic sympathetic stimulation, constricting blood vessels.
    • These drugs are effective in neurogenic shock and anaphylactic shock.
    • They are less effective in hemorrhagic shock because the sympathetic nervous system is already maximally activated.

    Other Treatment Strategies for Shock

    • Placing the patient in a head-down position promotes venous return and improves cardiac output.
    • Oxygen therapy can be beneficial in some cases, but it's not the primary solution for shock.
    • Glucocorticoids, like cortisol, are used to:
      • Strengthen the weakened heart
      • Stabilize lysosomes, preventing cellular damage
      • Aid in glucose metabolism.

    Circulatory Arrest

    • Circulatory arrest is a condition where all blood flow stops, potentially due to cardiac arrest or ventricular fibrillation.
    • Ventricular fibrillation can be treated using electroshock therapy.
    • Cardiopulmonary resuscitation (CPR) and oxygen administration are treatments for complete cardiac arrest.

    Hypovolemic Shock

    • Hypovolemic shock is caused by diminished blood volume, most commonly by hemorrhage.
    • Hemorrhage reduces blood volume, leading to decreased venous return and cardiac output, ultimately resulting in shock.
    • The sympathetic nervous system plays a crucial role in maintaining arterial pressure and cardiac output during blood loss.
    • Sympathetic reflexes can compensate for a 30% to 40% blood volume loss, allowing survival, while death can occur with a 15% to 20% loss without the reflexes.

    Importance of Sympathetic Nervous System

    • Sympathetic reflexes are more effective in maintaining arterial pressure than in maintaining cardiac output.
    • Increased total peripheral resistance due to sympathetic activation is the main mechanism for maintaining arterial pressure but does not benefit cardiac output.
    • Sympathetic vasoconstriction of veins is essential for maintaining venous return and preventing a drastic decrease in cardiac output.

    Central Nervous System Ischemic Response

    • The central nervous system ischemic response, triggered by brain hypoxia or carbon dioxide buildup, initiates a "last-ditch stand" by the sympathetic nervous system to prevent a critical drop in arterial pressure.
    • This response occurs when arterial pressure reaches approximately 50 mm Hg, creating a plateau in the arterial pressure curve.

    Protection of Coronary and Cerebral Blood Flow

    • Maintaining normal arterial pressure during decreased cardiac output is vital for protecting blood flow to the coronary and cerebral circulations.

    Pathophysiology of Shock Progression

    • Sluggish blood flow in microvessels leads to clotting and blockage, further worsening shock.
    • Increased tissue metabolism despite low blood flow produces acids (carbonic and lactic) that contribute to blood agglutination and microvessel blockage.
    • This phenomenon, known as "sludged blood", further impedes blood flow in the microvasculature.
    • After prolonged hypoxia, capillary permeability increases, resulting in fluid leakage into tissues, further diminishing blood volume and exacerbating shock.

    Positive Feedback Deterioration of Tissues in Shock

    • The worsening shock progresses through a vicious cycle of positive feedback mechanisms where each deterioration amplifies the shock severity.
    • The body's response to shock causes a progressive decline in tissue function and ultimately leads to multiple organ failure.
    • Disseminated intravascular coagulation (DIC) occurs, depleting clotting factors and causing bleeding in various tissues, particularly the gut wall.

    Septic Shock

    • Septic shock arises from a widespread bacterial infection carried through the bloodstream, causing tissue damage.
    • The severity of septic shock depends on the type of bacteria and the infected tissues.
    • Gram-positive bacteria are the most frequent causes, followed by endotoxin-producing Gram-negative bacteria.
    • Septic shock progresses similarly to other types of shock, leading to circulatory collapse and multi-organ dysfunction.

    Treatment of shock

    • Blood and plasma transfusion are the primary treatments for hemorrhagic shock and plasma loss, respectively.
    • Electrolyte solutions are used to correct dehydration as a cause of shock.
    • Plasma substitutes, like dextran solution, can be used when plasma is unavailable.
    • Sympathomimetic drugs, like epinephrine or norepinephrine, can be administered to counteract decreased sympathetic activity in shock, especially in anaphylactic shock.
    • Placing the patient in a head-down position can elevate blood pressure in most types of shock, particularly hemorrhagic and neurogenic shock.

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    Description

    This quiz explores the stages of circulatory shock, including the nonprogressive, progressive, and irreversible stages. It also covers causes such as reduced cardiac output, reduced blood volume, and septic shock. Test your knowledge on these critical concepts in understanding shock management.

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