Mediator of anaphylactic shock is

Appeared in: UPPSC 2017

Explanation

Anaphylactic shock is a Type I hypersensitivity reaction where pre-sensitized IgE antibodies on mast cells and basophils bind to an allergen.
This binding triggers rapid degranulation, releasing pre-formed chemical mediators, with histamine being the most significant primary mediator.
Histamine causes widespread vasodilation (leading to hypotension), increased vascular permeability (causing edema and hives), and smooth muscle contraction (resulting in bronchospasm).

Option B: Cytokines (like TNF and IL-1) are primarily involved in the late-phase reaction of anaphylaxis (hours later) and chronic inflammation, not the immediate, acute shock.
Option C: Dopamine is a catecholamine medication used as a vasopressor to treat shock; it is not a naturally released mediator that causes anaphylaxis.
Option D: Adrenaline (epinephrine) is the primary medication used to treat anaphylactic shock. It acts as a physiological antagonist to histamine, reversing its effects.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology of Anaphylactic Shock: Chemical Mediators as background academic context rather than a clinical decision trigger.
Recognizing the signs of histamine release (flushing, hives, wheezing, hypotension) is critical for early identification of anaphylaxis.
The immediate nursing priority is to administer adrenaline (epinephrine) as prescribed, which directly counteracts the life-threatening effects of histamine.
What if? If the patient is on a beta-blocker medication, they may have a blunted response to adrenaline. In this case, glucagon may be required to help reverse the effects of anaphylaxis, as it has a positive inotropic and chronotropic effect on the heart that is not dependent on beta-receptors.

How to Approach the Question

Identify the core concept: The question asks for the 'mediator' of anaphylactic shock.
Understand the term 'mediator': This refers to the chemical substance released by the body's cells that causes the signs and symptoms of the reaction.
Recall the pathophysiology of anaphylaxis: It's a Type I hypersensitivity reaction involving mast cell degranulation.
Evaluate the options: Histamine is the classic pre-formed mediator released from mast cells. Cytokines are involved, but in a later phase. Dopamine and Adrenaline are medications used to treat shock, not cause it. Adrenaline is the specific antidote.
Select the option that is the primary chemical cause of the immediate symptoms. This is histamine.

Concept Tested & Keywords

QL5pMCUcqOQied1eykKFH6

E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed pp. 95-97, 101-103

E6 Pharmacology Katzung 16e p. 1548-1550

Practise the full UPPSC 2017

Attempt every question from this paper in a timed mock, then review the full solution for each one.