Cushing's Reflex
Cushing's reflex is a physiological response to increased intracranial pressure characterized by the triad of hypertension, bradycardia, and apnea (or irregular respirations), indicating severe brain injury with brainstem compression or ischemia. 1, 2
Pathophysiology
The reflex occurs when elevated intracranial pressure causes direct pressure on or stretch of the brainstem, triggering a protective mechanism to maintain adequate cerebral perfusion pressure despite rising intracranial pressure 2
Brainstem ischemia alone, particularly in the posterior cerebral circulation, may be sufficient to elicit the reflex even with preserved forebrain circulation 3
The mechanism represents a baroreflex attempting to preserve cerebral blood flow in situations of extreme intracranial pressure elevation 4
Clinical Presentation
The classic triad consists of: 1, 2
Elevated blood pressure (hypertension)
Bradycardia (low heart rate)
Apnea or irregular breathing patterns
In trauma settings, systolic blood pressure ≥180 mmHg combined with heart rate ≤59 beats/min in patients with disturbed consciousness indicates high risk for life-threatening brain injury requiring immediate neurosurgical intervention 5
The reflex typically manifests in comatose patients and often signals that intracranial perfusion is about to be abolished 3
Clinical Significance and Management
Cushing's reflex is a warning sign of severe head injury requiring urgent intervention, not a pre-terminal event. 1, 2
Patients demonstrating this reflex have significantly higher rates of emergency cranial surgery within 24 hours (6.4% vs 5.4%) and in-hospital mortality (3.0% vs 2.3%) compared to those without these vital sign patterns 6
The reflex can occur with various neurosurgical conditions including subdural hematoma, tumors, hydrocephalus, and during neurosurgical procedures 2
Immediate management priorities include: 1
- Identifying and treating the underlying cause of increased intracranial pressure
- Preventing secondary brain injury by avoiding hypoxia and hypotension
- Considering urgent neurosurgical decompression
- Using anticholinergics (atropine) if needed, though cardiac pacing may be necessary in refractory cases 2
Important Caveats
Atropine use requires caution: While it can increase heart rate in autonomic derangements, it may exacerbate conduction block in patients with infranodal conduction disease and should be avoided in those settings 1
The reflex can self-abort with eventual good outcomes in some cases, supporting its role as a protective physiological mechanism rather than purely a pre-terminal sign 4
In trauma patients, the combination of hypertension and bradycardia without eye opening serves as a weak but significant predictor of need for immediate neurosurgical intervention 5
Always assess for associated spinal injuries and avoid nasopharyngeal airways if facial trauma or signs of basilar skull fracture are present 1