Cushing triad

**Components** 1. Hypertension (often systolic hypertension with widened pulse pressure) 2. Bradycardia 3. Irregular or depressed respirations (e.g., Cheyne-Stokes, ataxic/Biot breathing, apnea)

**Pathophysiology** - Rising ICP reduces cerebral perfusion pressure (CPP = MAP − ICP). - Cerebral ischemia, particularly of the medullary vasomotor center, triggers a sympathetic surge. This causes vasoconstriction and increased cardiac output, which raises systemic BP to restore cerebral perfusion. This is the Cushing reflex. - Hypertension is sensed by aortic arch and carotid baroreceptors. The baroreceptor reflex (vagal) then causes reflex bradycardia. - Brainstem compression or ischemia disrupts the medullary and pontine respiratory centers, producing irregular respirations.

**Clinical significance** - It is a late sign and indicates imminent or ongoing herniation (uncal/transtentorial, tonsillar). It is a neurosurgical emergency. - Causes of raised ICP include intracranial hemorrhage (epidural, subdural, intraparenchymal, subarachnoid), mass or tumor, cerebral edema, TBI, hydrocephalus, abscess, and severe meningitis. - Associated findings: declining level of consciousness, headache, vomiting, papilledema, a blown pupil (CN III compression), and posturing (decorticate/decerebrate).

**Management (high yield)** - Airway protection and intubation, with mild hyperventilation (PaCO₂ ~30–35 mmHg) as a temporary bridge only. It causes cerebral vasoconstriction and lowers ICP briefly. - Head of bed elevated 30°. - Osmotic therapy: mannitol or hypertonic saline. - Definitive treatment: surgical decompression, evacuation of the hematoma or mass, or CSF diversion (EVD). - Do NOT treat the hypertension aggressively. It is compensatory and maintains CPP. - Avoid lumbar puncture when ICP is raised, because of herniation risk.

**Do not confuse with** - Cushing syndrome/disease (hypercortisolism), which is unrelated. - Neurogenic shock (hypotension + bradycardia, from spinal cord injury above T6). - Cushing ulcer: stress-related gastric ulcers from raised ICP, caused by vagal stimulation → increased acid secretion.

**Board pearl:** HTN + bradycardia + irregular breathing in a head trauma patient = raised ICP/herniation → emergent ICP-lowering measures and neurosurgical intervention.