Cushing's Triad: Clinical Manifestations
Cushing's triad consists of three cardinal signs: hypertension, bradycardia, and irregular respirations (respiratory abnormalities), which indicate severe intracranial hypertension and impending herniation. 1, 2
The Three Components
- Hypertension: Elevated systemic blood pressure occurs as a compensatory mechanism to maintain cerebral perfusion pressure when intracranial pressure rises 2, 3
- Bradycardia: Slowed heart rate develops as part of the reflex response to elevated intracranial pressure 1, 2, 3
- Irregular respirations: Abnormal breathing patterns, including apnea, result from brainstem compression 3
Critical Clinical Context
Cushing's triad is a late and ominous sign that typically appears only after significant brain injury has occurred, and its absence does not exclude critically elevated intracranial pressure. 1, 2
Key Clinical Pitfalls
- The complete triad is not uniformly present in all patients with elevated ICP, and clinical signs such as pupillary dilation or decerebration typically appear late in the disease course 1
- ICP is typically >40 mmHg when Cushing's triad manifests, which is associated with a 6.9-fold increased mortality risk and almost universal severe consciousness impairment or coma 2, 4
- In patients on extracorporeal membrane oxygenation or other laminar flow circulatory support, bradycardia may be the sole component of Cushing's triad without accompanying hypertension or respiratory changes 5
Pathophysiology
The reflex represents a protective mechanism where brainstem ischemia or compression triggers systemic hypertension to preserve cerebral perfusion pressure despite elevated ICP, with bradycardia occurring as a secondary baroreflex response 3, 6
Immediate Management Implications
The presence of Cushing's reflex requires emergent neurosurgical evaluation, as it indicates severe intracranial hypertension with ICP typically >40 mmHg. 2
- Immediate interventions should include head elevation to 20-30 degrees with neutral neck positioning, ensuring adequate cerebral perfusion pressure of 60-70 mmHg 2, 7
- Osmotic therapy with mannitol (0.5-1 g/kg IV over 5-10 minutes) or hypertonic saline (3%) should be administered rapidly 2, 4
- Neurosurgical consultation is mandatory for consideration of CSF drainage, hematoma evacuation, or decompressive craniectomy 2