Triple Response of Lewis — FRCA Primary MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: D — Red line (capillary dilation) then flare (arteriolar dilation via axon reflex) then wheal (increased capillary permeability)
The triple response: (1) red line at the site of injury from local capillary dilation (appears in seconds) / (2) flare (redness spreading beyond the injury site) from arteriolar dilation via an axon reflex / (3) wheal (localised oedema) from increased capillary permeability due to histamine release. This demonstrates local vascular and neural inflammatory responses.
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist