Which component of Cushing's triad is not part of the classic triad?

• A. Hypertension
• B. Bradycardia
• C. Tachycardia
• D. Irregular respirations

Answer: (C)

Cushing's triad reflects late-stage intracranial hypertension and how the brainstem and autonomic centers respond to rising pressure. The classic signs are elevated systolic blood pressure with a widened pulse pressure, a slow heart rate (bradycardia), and irregular or abnormal respirations. The hypertension is the body's attempt to maintain cerebral perfusion as ICP climbs. Bradycardia occurs because brainstem compression stimulates vagal pathways, slowing the heart. Respirations become irregular because the medullary centers that regulate breathing are disrupted by the pressure.

Tachycardia is not part of this classic triad. While heart rate can vary for other reasons, the hallmark response to dangerous ICP progression is bradycardia, not tachycardia, alongside hypertension and irregular breathing.