Head Trauma

Question 1

What are the indications for ICP monitoring?

Answer 1

Patients with head injury, GCS 8 or less after CPR, and:

1. Abnormal admitting CT brain scan, or:
2. Normal admitting CT but with 2 or more of the following: a) age >40; b) SBP <90mmHg; c) unilateral or bilateral decerebrate or decorticate posturing.

Question 2

How is CPP calculated?

Answer 2

CPP = MAP - ICP. N.B.: actual pressure of interest is the mean CAROTID pressure, which can be approximated with the transducer zeroed at the level of the foramen of Monro.

Question 3

What is normal adult CPP?

Answer 3

50mmHg.

Question 4

What is cerebral autoregulation?

Answer 4

The physiological mechanism whereby CPP is maintained at a relative constant over a broad range of systemic blood pressure.

Question 5

After head injury, above what level of CPP provides no extra protection against ICP elevations above 20mmHg?

Answer 5

60mmHg.

Question 6

What are the normal intracranial constituents?

Answer 6

1. Brain volume approx 1400mL;
2. Cerebral blood volume 150mL;
3. CSF 150mL.

Question 7

What is the normal ICP range for adults?

Answer 7

10-15mmHg. Young children = 3-7mmHg, term infants 1.5-6mmHg.

Question 8

What may contribute to raised ICP after head injury?

Answer 8

1. Cerebral oedema;
2. Hyperaemia, vasomotor paralysis;
3. Surgical mass lesions (extradural or subdural haematoma etc);
4. Hydrocephalus;
5. Hypoventilation and hypercarbia;
6. Systemic hypertension;
7. Venous sinus thrombosis;
8. Increased muscle tone causing increased venous pressure;
9. Status epilepticus.

Question 9

What features make up Cushing’s triad?

Answer 9

1. Hypertension;
2. Bradycardia;
3. Respiratory irregularity.
   Triad only seen in 33% of cases of raised ICP.

Question 10

Name two contraindications for ICP monitoring.

Answer 10

1. Awake patient;

2. Coagulopathy.

Question 11

What is the risk of iatrogenic haemorrhage following insertion of an ICP monitoring device?

Answer 11

Approximately 1.4% for all types. Higher with parenchymal monitors than for ventricular drains, essentially zero risk for subarachnoid monitors.

Question 12

What is the risk of haematoma resulting from ICP monitor insertion requiring surgical evacuation?

Answer 12

0.5-2.5%.

Question 13

What are the risk factors for EVD infection?

Answer 13

1. ICP >20mmHg;
2. Duration of monitoring: controversial. Likely a non-linear increase for first 12 days, then rate diminishes rapidly;
3. Neurosurgical operation;
4. Irrigating the system;
5. Leakage around the EVD;
6. Open skull fracture(s);
7. Other systemic infections.

Question 14

What factors are NOT associated with EVD infection?

Answer 14

1. Insertion in ICU c.f. theatre;
2. Previous EVD;
3. Drainage of CSF;
4. Use of steroids.

Question 15

What makes up the normal ICP waveform?

Answer 15

1. Small pulsations transmitted from the systemic blood pressure (large arterial systolic peak, followed by a peak corresponding to the right atrial ‘A’ wave);
2. Slower, superimposed respiratory waves.

Question 16

What are the three Lundberg pathological ICP waveforms?

Answer 16

1. A waves, or plateau waves: elevations >50mmHg for 5-20 mins;
2. B waves, or pressure pulses: 10-20mmHg for 30 secs to 2 mins;
3. C waves: frequency of 4-8/min. Low amplitude (Traube-Hering waves) may sometimes be normal, high amplitude may be pre-terminal.