Shock: Definition and Classification

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which type of shock is characterized by a severe antibody-antigen reaction?

Anaphylactic shock (correct)

Cardiogenic shock

Hypovolemic shock

Septic shock

What is the primary cause of hypovolemic shock?

Impaired heart function

Loss of circulating or intravascular volume (correct)

Maldistribution of blood volume

Severe allergic reaction

Which of the following classifications of shock includes septic shock?

Cardiogenic shock

Hypovolemic shock

Obstructive shock

Distributive shock (correct)

What is a key pathophysiological change that occurs in all types of shock?

Impaired tissue perfusion Signup and view all the answers

Which type of shock results from the heart's inability to pump effectively?

Cardiogenic shock Signup and view all the answers

What is the primary result of neurogenic shock?

Loss of sympathetic tone Signup and view all the answers

Which stage of shock is characterized by the highest levels of lactic acid production?

Initial stage Signup and view all the answers

What compensatory mechanism is primarily responsible for increasing heart rate and contractility?

Neural response Signup and view all the answers

Which hormone is produced as a result of the activation of the renin response during compensatory stage?

Angiotensin II Signup and view all the answers

What effect does hyperventilation have during chemical compensation?

Causes respiratory alkalosis Signup and view all the answers

The progressive stage of shock can lead to which issue within the cardiovascular system?

Cardiac dysfunction Signup and view all the answers

Which of the following responses is NOT a part of the hormonal compensation during shock?

Increased glucagon production Signup and view all the answers

In the compensatory stage of shock, what is the primary purpose of blood shunting to vital organs?

To prioritize blood flow to essential systems Signup and view all the answers

What is a consequence of renal dysfunction during the progressive stage of ventricular failure?

Acute kidney injury (AKI) Signup and view all the answers

During which stage does shock become unresponsive to therapy and is considered irreversible?

Refractory stage Signup and view all the answers

Which factor does NOT influence oxygen transport to tissues?

Medications administered Signup and view all the answers

What primary dysfunction develops as a result of increased pulmonary capillary membrane permeability?

Respiratory failure Signup and view all the answers

Which of the following is a sign of shock in the assessment and diagnosis stage?

MAP less than 60 mm Hg Signup and view all the answers

What physiological consequence results from splanchnic vasoconstriction during gastrointestinal dysfunction?

Release of gram-negative bacteria Signup and view all the answers

What should be the first step in ensuring adequate oxygenation during medical management?

Establishing a patent airway Signup and view all the answers

Which element is crucial for adequate cardiac output (CO) and subsequently for oxygen transport?

Preload and after-load Signup and view all the answers

What initial signs indicate the progressive stage of hypovolemic shock?

Rising BUN and serum creatinine levels Signup and view all the answers

Which of the following is a characteristic of the refractory stage of hypovolemic shock?

Severe tachycardia and hypotension Signup and view all the answers

Which hemodynamic changes are expected in hypovolemic shock?

Decreased mean arterial pressure and cardiac index Signup and view all the answers

What is the primary goal in managing hypovolemic shock?

To correct the causes of the hypovolemia and restore tissue perfusion Signup and view all the answers

What is the expected clinical manifestation in the patient during the refractory stage of hypovolemic shock?

Unresponsiveness and varied clinical manifestations Signup and view all the answers

What characterizes absolute hypovolemia?

Loss of fluid from the intravascular space Signup and view all the answers

What is a compensatory mechanism that occurs when fluid volume loss is up to 30%?

Increased heart rate of more than 100 b/m Signup and view all the answers

Which of the following best describes the progressive stage of hypovolemic shock?

Dysrhythmias develop due to myocardial ischemia Signup and view all the answers

What does a decrease in venous return lead to in the context of hypovolemic shock?

Decrease in cardiac output Signup and view all the answers

What blood gas abnormality is typically present during the progressive stage of hypovolemic shock?

High PaCo2 and low bicarbonate Signup and view all the answers

Which compensatory response occurs when fluid volume loss reaches 15% to 30%?

Increased respiratory rate and depth Signup and view all the answers

What indicates ineffective tissue perfusion during the progressive stage of hypovolemic shock?

Oliguria resulting from renal perfusion decrease Signup and view all the answers

What is a potential clinical manifestation during the compensatory stage of hypovolemic shock?

Increased heart rate above 100 b/m Signup and view all the answers

Study Notes

Definition of Shock

Shock is a widespread process that impairs tissue perfusion causing cellular, metabolic, and hemodynamic alterations.

Classification of Shock

Hypovolemic shock: results from fluid loss, either external or internal.
Cardiogenic shock: occurs due to the heart's inability to pump effectively.
Distributive shock: causes blood maldistribution within the body, further categorized into:
- Septic shock: arises from infection entering the body.
- Anaphylactic shock: caused by severe allergic reactions.
- Neurogenic shock: results from the loss of sympathetic nerve function

Stages of Shock

Initial stage: decreased cardiac output leads to anaerobic metabolism, producing lactic acid.
Compensatory stage: sympathetic nervous system activation increases heart rate, vasoconstriction, and redirects blood to vital organs. This involves neural, hormonal, and chemical responses.
Progressive stage: compensatory mechanisms fail, leading to organ dysfunction like cardiovascular, central nervous system, pulmonary, renal, and gastrointestinal impairments.
Refractory stage: shock becomes unresponsive to treatment, leading to multiple organ dysfunction syndrome (MODS) and eventual death.

Pathophysiology of the Compensatory Stage

Neural response: increased heart rate, contractility, and vasoconstriction to redirect blood.
Hormonal response: Includes:
- Renin response: causes vasoconstriction, aldosterone, and ADH release.
- Anterior pituitary stimulation: releases ACTH, leading to glucocorticoid release.
- Adrenal medulla stimulation: releases epinephrine and norepinephrine, reinforcing compensatory mechanisms.
Chemical response: hyperventilation, resulting in respiratory alkalosis.

Pathophysiology of the Progressive Stage

Cardiovascular system: Myocardial hypoperfusion causes dysfunction. Ventricular failure occurs.
Central nervous system: Cerebral hypoperfusion causes SNS failure, cardiac and respiratory depression, and thermoregulatory failure.
Pulmonary system: Pulmonary capillary membrane permeability, microemboli, and vasoconstriction lead to acute lung injury (ALI) and ventilatory failure.
Renal system: Renal vasoconstriction causes renal hypoperfusion resulting in acute kidney injury (AKI).
Gastrointestinal system: Splanchnic vasoconstriction and hypoperfusion impair gut function. Enteric bacteria release into the bloodstream, exacerbating shock.

Assessment and Diagnosis

Mean arterial pressure (MAP) less than 60 mmHg and systolic BP less than 90 mmHg.
Tachycardia or bradycardia.
Altered mental status.
Elevated serum lactate, arterial base deficit, serum bicarbonate, and reduced central or mixed venous oxygen saturation.

Medical Management

Focus on restoring tissue perfusion through:
- Improving pulmonary gas exchange: Ensuring adequate oxygenation through airway management, supplemental oxygen, and mechanical ventilation.
- Adequate cardiac output and hemoglobin: Using fluids (crystalloids, colloids, or blood products) and medications like vasoconstrictors, vasodilators, inotropes, and anti-dysrhythmics.

Hypovolemic Shock

Occurs due to inadequate intravascular volume, leading to decreased tissue perfusion and shock syndrome.
Types:
- Absolute hypovolemia: external fluid loss (blood, plasma, etc).
- Relative hypovolemia: vasodilation reduces effective circulating volume.

Pathophysiology of Hypovolemic Shock

Causes: Loss of circulating fluid volume, reduced venous return, lowered preload, decreased CO, inadequate cellular oxygen supply, and ineffective tissue perfusion.

Clinical Manifestations of Hypovolemic Shock

Initial stage: fluid loss up to 15% (750 ml), compensatory mechanisms maintain CO, appears asymptomatic.
Compensatory stage: fluid loss of 15-30% (750-1500 mL), CO drops, leading to:
- Increased heart rate (more than 100 bpm).
- Increased respiratory rate (20-30 bpm).
- Respiratory alkalosis and hypoxemia (low PaCO2 and low PaO2).
- Decreased urine output (20-30 ml/h).
- Pale and cool skin with delayed capillary refill.
- Flat jugular veins.
Progressive stage: fluid loss of 30-40% (1500-2000 mL), compensatory mechanisms fail, resulting in:
- Heart rate exceeding 120 bpm, dysrhythmias, and myocardial ischemia..
- Respiratory distress.
- Respiratory and metabolic acidosis, hypoxemia (high PaCO2, low bicarbonate, low PaO2).
- Oliguria.
- Ashen, cold, and clammy skin with marked delayed capillary refill.
- Lethargy due to declining cerebral perfusion.
Refractory stage: fluid loss exceeding 40% (2000 mL), compensatory mechanisms collapse, leading to:
- Severe tachycardia and hypotension.
- Absent peripheral pulses and capillary refill.
- Cyanotic and diaphoretic skin.
- Unresponsiveness, and multiple organ system failure manifestations.

Hemodynamic Parameters in Hypovolemic Shock

Reduced CO and cardiac index.
Decreased preload (reduced CVP, RAP, PAOP).
Increased afterload (elevated SVR).
Lowered MAP.

Management of Hypovolemic Shock

Focus on addressing the cause of hypovolemia and restoring circulatory volume.
Methods include:
- Stopping fluid loss.
- Administering fluids (crystalloids, colloids, blood products).
- Monitoring for fluid overload.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the critical concepts surrounding shock, including its definition, classification into hypovolemic, cardiogenic, and distributive types, and the stages of shock. Learn how tissue perfusion and metabolic alterations affect the body in this essential medical overview.