College Answer

a) 
For: 
- This patient has about a 50 – 60% chance of developing raised ICP. 
- It is critical that CPP is maintained and to know the CPP need to know the ICP. 
- ICP is a strong predictor of outcome after severe TBI. 
- Several studies have shown substantial lowering of mortality after ICP monitoring and 
control was introduced. 
- Numerous studies have also shown that patients who respond to ICP-lowering therapies 
have a lower mortality compared to those who don't, allowing some prognostication. 
- Internationally accepted BTF Guidelines advise ICP monitoring in patients with severe 
TBI (GCS < 9) and an abnormal CT scan. 
- Doesn't lead to greater intensity of treatment or ICU LOS compared to no ICP 
- If EVD allows CSF drainage and analysis. 
- Early diagnosis of secondary surgically correctable lesion e.g.: delayed subdural 
haematoma.

Against: 
- Risks associated with brain injury associated coagulopathy. 
- Other risks – infection, false readings and risks of avoidable interventions (osmotherapy, 
falsely elevating CPP, deep sedation). 
- BEST TRIPPS study showing no difference in outcome. 
- May require transfer to OT for insertion. 

b) 
- Secondary injury occurs at any time after the primary injury, and thus should theoretically 
be preventable and is caused primarily by: 
o Hypoxia 
 Ensure a PaO2 > 80 and/or SpO2 > 92% 
o Hyper/hypocarbia 
 PaCO2 35 - 40mmHg 
o Hypotension 
 SBP > 90 mmHg and/MAP > 70 mmHg / CPP > 50 mmHg 
o Metabolic disturbance (Na, glucose, osmo) 
 Na+ of 140 – 150 mmol/L, glucose 6 – 10, Serum osmo 320 mOsm/L 
o Fever 
 Normothermia 
o Seizures 
 Phenytoin x 72hrs 
o Raised ICP 
 ICP lowering therapy (head up 30o, neck neutral alignment, sedation and 
paralysis, osmotherapy, drain CSF, surgical decompression) 
o Secondary surgical lesion (delayed subdural/parenchymal haemorhage) 
 Repeat CT, surgical therapy

Discussion

a) is a list of arguments for and against ICP monitoring. The debate about indications for intracranial pressure monitoring (strictly, whether there are any) is discussed in the Required Reading section.

To simplify revision, and because the author has succumbed to sloth, large greyish boxes have been lifted from that section and planted here with zero modification.

A precise definition of "secondary brain injury" is remarkably difficult to find, as occurs often with frequently used terminology of which everybody has some assumed intuitive understanding. Go on everyone, define "injury" in general. The college, in its model answer, does not define the term, but rather frames it in terms of problems and solutions.

Prevention of secondary brain injury - colloquially referred to as "neurprotective measures" - is discussed elsewhere, both as a brief summary and as a rambling dialogue. Salient points from the brief summary are lazily pasted below.

Goals of management, in summary:

Maintaining cerebral oxygen supply:

• Normoxia: keep the PaO₂ above 60 mmHg
• Normotension: measure the MAP, and keep the systolic above 90mmHg
• Intracranial Pressure monitoring: keep it under 20mmHg
• Cerebral perfusion pressure: keep it 50-70mmHg
• Cerebral oxygenation monitoring:keep the SjO₂ >50%, and PbrO₂ >55mmHg
• Managing increased intracranial pressure for which there is a variety of strategies:
  • Draining the EVD ( about 20ml/hr, max)
  • Positioning the head straight
  • Removing the C-spine collar
  • Sedation :
    • Propofol sedation to decrease distress and thus decrease ICP
    • Barbiturate coma if other methods of lowering ICP have failed
    • Analgesia to prevent increased ICP in response to suctioning and routine care
  • Paralysis
  • Osmotherapy
  • Controversial measures
    • Decompressive craniectomy
    • Hypothermia
    • Dexamethasone

Decreasing cerebral oxygen demand:

• Sedation
  • Propofol sedation to decrease distress and thus decrease ICP
  • Barbiturate coma if medical and surgical methods of lowering ICP have failed
• Analgesia - opioid selection is irrelevant, but opiate boluses increase ICP
• Seizure prophylaxis is infrequently indicated, and the course is 7 days only

Controversial measures:

• Decompressive Craniectomy
• Hypothermia
•