Anaphylactic shock, characterized by a severe, systemic allergic reaction leading to massive vasodilation and increased capillary permeability, is classified as which type of shock?

1. A

   Cardiogenic Shock

2. B

   Hypovolemic Shock

3. C

   Distributive Shock

4. D

   Obstructive Shock

Appeared in: NORCET 9 Prelims-2025

Explanation

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• Distributive shock is defined by a primary disturbance of reduced systemic vascular resistance (SVR) due to widespread vasodilation.
• Anaphylaxis is a severe, IgE-mediated allergic reaction that causes a massive release of histamine.
• Histamine leads to profound vasodilation and increased capillary permeability, causing fluid to shift from the intravascular to the interstitial space.
• This results in a 'relative' hypovolemia, where blood volume is poorly distributed, fitting the definition of distributive shock.

Why Other Options Were Wrong

• Option A: Cardiogenic shock is caused by primary heart pump failure, where the heart cannot pump enough blood to meet the body's needs. The primary problem is with cardiac contractility, not blood vessel dilation.
• Option B: Hypovolemic shock results from the actual loss of blood or fluid volume from the body. In anaphylaxis, the fluid volume is still within the body, just not within the blood vessels.
• Option D: Obstructive shock is caused by a physical blockage that impedes blood flow to or from the heart. The problem is a mechanical obstruction, not a change in vascular tone.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification and Pathophysiology of Shock as background academic context rather than a clinical decision trigger.
• Recognizing anaphylactic shock as a form of distributive shock is crucial for initiating the correct treatment promptly. The primary goal is to reverse the vasodilation and support blood pressure.
• The first-line and most critical intervention for anaphylactic shock is the immediate administration of intramuscular (IM) epinephrine. It causes vasoconstriction, which counteracts the massive vasodilation, and bronchodilation, which helps with breathing difficulties.
• What if? If a patient in anaphylactic shock does not respond to initial epinephrine and fluid resuscitation, a continuous vasopressor infusion (like norepinephrine) may be required in an ICU setting to maintain adequate blood pressure by counteracting the persistent vasodilation.

How to Approach the Question

• First, identify the key pathophysiological processes described in the question stem: 'massive vasodilation' and 'increased capillary permeability' resulting from a 'severe, systemic allergic reaction'.
• Next, recall the four main classifications of shock: Cardiogenic, Hypovolemic, Distributive, and Obstructive.
• Analyze the primary mechanism for each shock type. Cardiogenic is pump failure, Hypovolemic is volume loss, and Obstructive is a physical blockage.
• Recognize that widespread vasodilation and maldistribution of blood flow are the defining characteristics of Distributive shock.
• Match the pathophysiology from the question (vasodilation and leaky vessels) to the correct classification, which is Distributive Shock.
• Eliminate the other options as their core mechanisms do not align with the description of anaphylaxis.

Concept Tested & Keywords

• Concept Tested: Classification and Pathophysiology of Shock
• Stem keywords: Anaphylactic shock, systemic allergic reaction, massive vasodilation, increased capillary permeability
• Lead-in keywords: classified as
• Negative lead-in flag: false

Question ID

Qo37oCv35y83w-ZmtcVPp7

Copy ID

Reference Book

E6 Medicine Harrison 22e Part 2 p. 215-217

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 645-647