What are the considerations for using a subdural catheter for Intracranial Pressure (ICP) monitoring?

Considerations for Using a Subdural Catheter for ICP Monitoring

Intraparenchymal probes are generally preferred over subdural catheters for ICP monitoring due to their better risk-benefit profile, though subdural catheters may be considered in specific clinical scenarios. 1

Indications for ICP Monitoring

• ICP monitoring is indicated primarily in patients with severe traumatic brain injury (TBI) with abnormal CT scan or when neurological assessment is not feasible 2
• Specific indications include:
  • Glasgow Coma Scale ≤8 with abnormal CT scan 2
  • Patients with normal CT but with inability to perform adequate neurological assessment 2
  • After evacuation of post-traumatic intracranial hematoma (subdural, epidural, or intraparenchymal) with at least one of the following criteria:
    • Preoperative GCS motor response ≤5
    • Preoperative anisocoria or bilateral mydriasis
    • Preoperative hemodynamic instability
    • Preoperative severity signs on imaging
    • Intraoperative cerebral edema
    • Postoperative appearance of new intracranial lesions 1, 2

Subdural Catheter Compared to Other ICP Monitoring Devices

Advantages of Subdural Catheters:

• Lower risk of blockage (2.7%) compared to Richmond screws (16%) 3
• May be easier to place than ventricular catheters in certain situations 3
• Particularly useful in small children and neonates when other methods are technically challenging 4

Disadvantages of Subdural Catheters:

• Less accurate than ventricular catheters, which remain the gold standard 5, 6
• Cannot drain CSF therapeutically unlike ventricular catheters 5
• Current guidelines suggest intraparenchymal probes may be preferred over other methods when considering risk-benefit balance 1

Complications of ICP Monitoring

• Ventricular catheters:

  • Infection rate: approximately 10% 1, 2
  • Intracerebral hemorrhage: 2-4% 1, 2
  • Catheter placement failure: 10% 1, 2

• Intraparenchymal devices:

  • Infection rate: approximately 2.5% 1, 2
  • Intracerebral hemorrhage: 0-1% 1, 2

• Subdural catheters:

  • Generally lower risk of hemorrhage compared to ventricular catheters 3
  • May have lower infection rates than ventricular catheters 3

Management Goals After ICP Monitor Placement

• Maintain cerebral perfusion pressure (CPP) between 60-70 mmHg in the absence of multi-modal monitoring 1, 2
• Avoid CPP >70 mmHg routinely as it may increase risk of respiratory distress syndrome without improving neurological outcomes 1
• Avoid CPP <60 mmHg as it is associated with poor outcomes 1, 2
• Avoid CPP >90 mmHg as it may worsen neurological outcomes by aggravating vasogenic cerebral edema 1, 2
• ICP should be maintained below 20-25 mmHg if possible 1

Important Considerations and Caveats

• The benefit of ICP monitoring on patient outcomes has not been clearly demonstrated in controlled trials 1
• The BEST-TRIP randomized controlled study found no difference in neurological outcome between ICP monitoring and clinical surveillance with repeated CT scans 1
• Risk-benefit assessment should be individualized, especially in patients with normal initial CT scan 1
• When ICP monitoring is indicated, the reference point to measure mean arterial pressure should be placed at the external ear tragus 1
• In patients with altered cerebral autoregulation, an ICP-based protocol with CPP around 60 mmHg may be more beneficial than higher CPP targets 1

Technical Considerations for Subdural Catheters

• Subdural catheters can be placed percutaneously in some cases, particularly in small children 4
• While less accurate than ventricular catheters, they may still provide clinically useful information when ventricular catheterization is not feasible 5, 6
• Continuous monitoring allows for immediate treatment initiation when increased ICP is observed 4