Emergency Medical Technician (EMT) Intermediate Practice Exam

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Prepare for the Emergency Medical Technician (EMT) Intermediate Test with focused study methods including flashcards and multiple-choice questions. Practice with hints and detailed explanations to boost your readiness for the exam.

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What causes decreases in cardiac output and blood pressure during anaphylactic shock?

Fluid retention
Systemic vasodilation
Increased heart rate
Decreased blood volume

The correct answer is: Systemic vasodilation

In anaphylactic shock, one of the main physiological changes that occurs is systemic vasodilation. During anaphylaxis, the body's immune system overreacts to an allergen, leading to the release of histamines and other mediators. These substances cause blood vessels to widen (dilate), which significantly decreases systemic vascular resistance. As a result, blood pressure drops, and the heart's ability to maintain a sufficient cardiac output is compromised because the blood flow is not effectively returned to the heart. The widening of blood vessels means that the blood can pool in the extremities instead of being efficiently circulated throughout the body. This decrease in vascular resistance not only leads to a lower blood pressure but also means that less blood is available to be pumped by the heart at any given moment, further reducing cardiac output. This interplay is why systemic vasodilation is the critical factor leading to decreased cardiac output and blood pressure in the context of anaphylactic shock.