Acute Subdural Hematoma - Trauma Management

Key Points

• Acute SDH often indicates both a mass lesion and significant underlying parenchymal brain injury.
• BTF recommends surgery for thickness greater than 10 mm or midline shift greater than 5 mm regardless of GCS.
• Smaller SDHs can still require surgery when a comatose patient deteriorates, has abnormal pupils, or elevated ICP.
• Prevent hypotension and hypoxemia aggressively.
• Reverse anticoagulation promptly.
• Hyperosmolar therapy is a temporizing bridge when herniation or high ICP is present.
• Stable nonoperative cases require serial neurologic examinations and repeat CT.

Algorithm

1. Stabilize airway, oxygenation, and blood pressure while maintaining cervical-spine precautions.
2. Document GCS and pupil findings and identify anticoagulant exposure.
3. Obtain immediate noncontrast head CT.
4. Activate neurosurgery and compare thickness, midline shift, and neurologic status with surgical criteria.
5. Reverse anticoagulants and treat active seizures.
6. Proceed to craniotomy or decompressive surgery when indicated.
7. For nonoperative cases, use ICU or high-acuity observation with serial exams and repeat CT.
8. Manage intracranial hypertension using tiered severe-TBI strategies.

Clinical Synopsis & Reasoning

Acute subdural hematoma appears on CT as a crescent-shaped extra-axial collection that can cross cranial sutures but is limited by dural reflections. It commonly results from high-energy trauma, falls in older adults, or injury in anticoagulated patients. Unlike many epidural hematomas, acute SDH often coexists with contusion, diffuse axonal injury, swelling, and other parenchymal damage, so prognosis depends on more than removing the clot.

Assess GCS, pupils, focal deficits, seizure activity, anticoagulant use, and signs of systemic trauma. Hypotension and hypoxemia are particularly harmful in severe TBI and should be corrected immediately. Rapid loss of consciousness, progressive hemiparesis, anisocoria, posturing, or Cushing physiology signals dangerous mass effect. Even a patient with a modest-appearing collection can deteriorate if cerebral swelling increases.

Brain Trauma Foundation surgical guidance recommends evacuation of an acute SDH with thickness greater than 10 mm or midline shift greater than 5 mm regardless of GCS. In a comatose patient with a smaller SDH, surgery is indicated when GCS falls by at least 2 points from injury to admission, pupils are asymmetric or fixed and dilated, or ICP exceeds 20 mm Hg. These criteria support, rather than replace, immediate neurosurgical judgment.

Treatment Strategy & Disposition

Manage airway, ventilation, and circulation according to severe TBI principles, with meticulous avoidance of hypotension, hypoxemia, fever, and major carbon dioxide derangement. Elevate the head if safe, reverse anticoagulants promptly, correct clinically significant coagulopathy, and treat seizures. Obtain neurosurgical consultation as soon as SDH is identified rather than after repeat imaging.

Perform surgical evacuation when size or neurologic criteria are met. Craniotomy allows hematoma removal; decompressive craniectomy may be required when severe swelling prevents safe bone-flap replacement or when refractory intracranial hypertension is present. For selected small stable SDHs without surgical criteria, admit for serial neurologic examinations and repeat CT because expansion can occur.

Hypertonic saline or mannitol can temporarily lower ICP during acute deterioration while surgery is arranged. Brief hyperventilation is reserved for impending herniation, not routine prophylaxis. ICP monitoring is considered in severe TBI according to imaging and clinical status. Begin venous thromboembolism prophylaxis when repeat imaging demonstrates stability and neurosurgical risk is acceptable, using current trauma protocols.

Epidemiology / Risk Factors

• Acute SDH is common in severe blunt TBI and in older adults after falls.
• Anticoagulation increases incidence and risk of expansion.
• Mortality is higher than for isolated epidural hematoma because underlying brain injury is often more severe.
• Alcohol use, frailty, and repeated falls are common contributors in older populations.

Investigations

Typical Surgical Indicators

Pharmacology

Prognosis / Complications

• Initial GCS, pupil reactivity, age, hypotension, associated brain injury, and time to decompression strongly influence outcome.
• Some patients recover well after prompt evacuation, while others remain disabled from diffuse primary injury.
• Delayed expansion can occur during nonoperative management.
• Survivors often require prolonged cognitive, physical, and occupational rehabilitation.

Patient Education / Counseling

• Explain that surgery removes pressure from blood but cannot reverse all injury that occurred to the brain at impact.
• Families should understand why anticoagulant reversal and repeat imaging are urgent.
• Discuss likely rehabilitation needs after severe injury.
• For stable nonoperative cases, provide strict return precautions after discharge and review fall-prevention and anticoagulation plans.

Notes

A subdural hematoma should never be interpreted as an isolated image finding in a severely injured patient. It often marks a broader injury that includes contusion, edema, diffuse axonal injury, and systemic trauma.

The CT thresholds are memorable, but neurologic deterioration overrides a reassuring measurement. A smaller clot with worsening pupils or consciousness can be more urgent than a larger stable clot.

Nonoperative management requires a defined surveillance plan rather than simple admission. The frequency of neurologic examinations should match injury severity, and staff must know which change triggers immediate CT and neurosurgical reassessment. A subtle new pronator drift, increasing confusion, repeated emesis, or new anisocoria may precede profound decline. Older adults are particularly vulnerable to under-recognition because baseline cognitive impairment can make small changes difficult to detect. When antithrombotic therapy was prescribed for a strong indication such as a mechanical valve or recent thrombosis, the eventual restart plan should be discussed early with neurosurgery and the prescribing specialty rather than left unresolved at discharge.

References

1. Brain Trauma Foundation: Surgical Management of Traumatic Brain Injury — Link
2. ACS Best Practices Guidelines for Traumatic Brain Injury — Link