The Cushing reflex (not to be confused with Cushing's triad is a hypothalamic response to ischemia, usually due to poor perfusion (delivery of blood) in the brain.
The Cushing reflex consists of an increase in sympathetic outflow to the heart as an attempt to increase arterial blood pressure and total peripheral resistance, accompanied by bradycardia.
The ischemia activates the sympathetic nervous system, causing an increase in the heart's output by increasing heart rate and contractility along with peripheral constriction of the blood vessels. This accounts for the rise in blood pressure, ensuring blood delivery to the brain. The increased blood pressure also stimulates the baroreceptors (pressure sensitive receptors) in the carotids, leading to an activation of the parasympathetic nervous system, which slows down the heart rate, causing the bradycardia.
The Cushing reflex is usually seen in the terminal stages of acute head injury.
The Cushing reflex was first described by Harvey Cushing in 1902.