Management of a 3.5 mm Subdural Hematoma
A 3.5 mm subdural hematoma in a neurologically intact patient should be managed conservatively with close observation, serial neurological assessments, and repeat imaging, as no patient with an initial SDH ≤3 mm has ever required surgical intervention. 1
Conservative Management Protocol
For stable patients without significant neurological deficits and small hematomas, conservative management with close monitoring is the appropriate strategy. 2
Observation Requirements
- Admit to a monitored hospital setting with neurosurgical consultation available, regardless of Glasgow Coma Scale score, due to risk of delayed deterioration 3
- Perform GCS monitoring every 15 minutes for the first 2 hours, then hourly for 12 hours 3
- Document individual GCS components (Eye, Motor, Verbal) rather than sum scores 3
- Assess pupillary size and reactivity at each evaluation 3
- Monitor for focal neurological deficits and level of confusion/orientation hourly 3
Imaging Protocol
- Obtain repeat CT scan at 20-24 hours after initial imaging, particularly if the patient is on anticoagulation 3
- Serial imaging is essential because 25% of acute subdural hematomas enlarge on follow-up 1
- Although 11.1% of SDHs ≤3 mm may enlarge (maximum width 10 mm), none require surgery 1
Anticoagulation Management
If the patient is on anticoagulation or antiplatelet therapy, all agents must be discontinued immediately and reversed during the acute period for at least 1-2 weeks after the hemorrhage. 4
- Rapidly reverse anticoagulation using prothrombin complex concentrate plus vitamin K 2
- The duration of anticoagulation interruption is typically 7-15 days, with low risk of ischemic events during this period 2
- Oral anticoagulants may be resumed after 3-4 weeks (or approximately 4 weeks post-surgical removal if surgery becomes necessary), with rigorous monitoring and maintenance of INRs in the lower end of the therapeutic range 4, 2
Critical Thresholds for Surgical Intervention
Immediate surgical evacuation becomes necessary only if the patient develops:
- A decrease of 2 or more points in GCS score 3
- New focal neurological deficits or signs of herniation (pupillary changes) 2, 3
- Altered or decreased consciousness 5
- Significant mass effect with midline shift >5 mm or hematoma thickness >5 mm 2
The evidence is clear that an 8.5 mm initial SDH size threshold best predicts the need for surgical intervention, and your patient at 3.5 mm falls well below this threshold. 1
Risk Factors for Expansion to Monitor
While your patient's 3.5 mm SDH is unlikely to require intervention, monitor closely for these expansion risk factors:
- Hypertension (significant predictor of expansion) 3, 1
- Concurrent subarachnoid hemorrhage 3, 1
- Convexity location 1
- Initial midline shift 1
- Advanced age (>60 years increases risk) 3
Special Considerations for Elderly Patients
- Elderly patients on anticoagulation or antiplatelet therapy have higher risk of delayed deterioration, with 70% deteriorating within the first 24 hours 3
- Delayed hemorrhage occurs in 1.4-4.5% of anticoagulated patients even with initially negative CT 3
- Mandatory 24-hour observation with repeat CT at 20-24 hours is necessary for anticoagulated patients 3
Critical Pitfalls to Avoid
- Never discharge based solely on small hematoma size without appropriate observation period, especially in elderly patients or those on anticoagulation 3
- Do not administer long-acting sedatives or paralytics before neurosurgical evaluation, as this masks clinical deterioration 3
- Do not delay correction of secondary insults (hypotension with SBP <100 mmHg, hypoxia with SpO2 <95%) 3
- Maintain mean arterial pressure ≥80 mmHg to ensure adequate cerebral perfusion 3