Traumatic Brain Injury and Drug Induced Coma

Question 1

What is a coup injury?

Answer 1

The initial injury when someone’s head is hit, the trauma of the brain hitting of the skull

Contrecoup injury is the secondary damage of the brain bouncing back of the opposite side of the hit.

Question 2

What happens to axons when there is brain trauma?

Answer 2

Contusion
The axons are pulled a little damaging them

Shear
Some axons get completely sheared

Question 3

What are some examples of primary insult on the brain?

Answer 3

Haematoma
Contusions
Haemorrhage
Diffuse axonal injury

Question 4

How does head trauma lead to brain injury?

Answer 4

Disruption of tight junctions of the blood brain barrier

• Increased permeability
• Things can enter the brain more easily

Injury leads to oxidative stress
And inflammatory mediators
Which head to the site of injury
Along with an increase in coagulability
Which can lead to clots in microvascular structures

Possible changes in expression of ion channels

Question 5

What is the Monro-Kellie hypothesis?

Answer 5

It is the pressure volume relationship between intracranial pressure, the volume of blood, brain and CSF and the cerebral perfusion pressure (CPP)

Question 6

How can the intracranial space compensate to avoid an increase in ICP?

Answer 6

There is the ability to move around the venous volume and CSF to make room for an increase in pressure from either the arterial blood, Brain, mass or oedema

But only up to a point, after that it goes into a decompensated state and the ICP rises

Question 7

Tell me about perfusion in the brain.

Answer 7

Cerebral perfusion pressure (CPP) is equal to the mean arterial pressure (MAP) minus Intracranial Pressure (ICP)

CPP=MAP-ICP

Question 8

Why do we induce comas?

Answer 8

Because in a coma a persons Cerebral metabolic requirement of O2 reduces and so if they have a problem leading to a reduced CPP then it can help them, and hopefully the brain can start to repair itself

Question 9

Name some drugs we give when inducing a coma.

Answer 9

Propofol (Decrease CMRO2 - dose dependant hypotension)

Thiopentone (Decrease CMRO2 - dose dependant hypotension)

Opioids - Pain relief for injuries, reduces stress response, reduce cough (can exacerbate hypotension)

Ketamine

Neuromuscular blocking agents

Mannitol (osmotic diuretic/ helps pull water out of brain)

Vasopressors (Can help adjust BP in anaesthetic induced drops)

Question 10

How do we measure someone in a coma?

Answer 10

EEG
Physiological markers (wakefulness)
ITU Nurse