What are the indications for placing an invasive Intracranial Pressure (ICP) monitor?

Indications for Invasive Intracranial Pressure (ICP) Monitoring

Invasive ICP monitoring is strongly indicated in patients with severe traumatic brain injury (TBI) with abnormal CT scan findings or when neurological assessment is not feasible. 1, 2

Primary Indications

• Patients with Glasgow Coma Scale (GCS) ≤8 with abnormal CT scan findings 1, 2
• Patients with normal CT scan but with inability to perform adequate neurological assessment 2
• Patients with normal CT scan but with hemodynamic instability (requires case-by-case evaluation) 2

CT Scan Findings Associated with Risk of Intracranial Hypertension

• Compression of basal cisterns (most reliable radiological sign of intracranial hypertension) 1, 2
• Disappearance of cerebral ventricles 1, 2
• Midline shift >5 mm 1, 2
• Intracerebral hematoma volume >25 mL 1, 2
• Presence of traumatic subarachnoid hemorrhage 1, 2

Post-Surgical Indications

ICP monitoring is recommended after evacuation of post-traumatic intracranial hematoma (subdural, epidural, or intraparenchymal) if at least one of the following criteria is present:

• Preoperative GCS motor response ≤5 1, 2
• Preoperative anisocoria or bilateral mydriasis 1, 2
• Preoperative hemodynamic instability 1, 2
• Preoperative severity signs on cerebral imaging 1, 2
• Intraoperative cerebral edema 2
• Postoperative appearance of new intracranial lesions on neuroimaging 2

Contraindications and Special Considerations

• ICP monitoring is not recommended if the initial CT scan is strictly normal without evidence of clinical severity 1, 2
• The incidence of elevated ICP is particularly low (0-8%) when the initial CT scan is normal 1, 2
• Risk-benefit assessment does not support invasive ICP monitoring in patients with severe TBI with strictly normal initial CT scan 1, 2

Complications of ICP Monitoring

• Catheter placement failure (10%) 1, 2
• Infection (10% for intraventricular drains and 2.5% for intraparenchymal fiberoptic devices) 1, 2
• Intracerebral hemorrhage (2-4% for intraventricular drains and 0-1% for intraparenchymal devices) 1, 2

Technical Considerations

• Intraparenchymal probes are generally preferred over intraventricular drains due to better risk-benefit profile 1, 2
• ICP monitoring allows calculation of cerebral perfusion pressure (CPP), which should be maintained between 60-70 mmHg 2
• ICP values >20-40 mmHg are associated with higher mortality risk (3.95 times higher) 1
• ICP values >40 mmHg are associated with 6.9 times higher mortality risk 1

Duration of Monitoring

• Consider removal of invasive ICP monitoring after 72 hours of normal ICP values 3
• Earlier removal may be justified if CT scan is normal (with minimal or no signs of injury) and neurological examination is possible 3
• Follow-up CT scans should be performed based on clinical deterioration or increased ICP values rather than as routine practice 4

Important Caveats

• Despite widespread use, the BEST-TRIP randomized controlled study found no difference in neurological outcome between ICP monitoring and clinical surveillance with repeated CT scans 1, 2
• Non-invasive monitoring methods (e.g., optic nerve sheath diameter measurement, transcranial Doppler) may be considered for follow-up after invasive ICP probe removal or when invasive monitoring is contraindicated 3
• ICP monitoring provides valuable information beyond just pressure values, including data on cerebral compliance, autoregulation, and waveform analysis that can guide individualized treatment 5, 6