Neurotrauma Flashcards
What are the most common types of traumatic injuries seen in ED?
Head injuries
Why is the primary goal of treatment of patients with a suspected TBI is to prevent secondary injury to the brain?
Moderate and severe TBIs are associated with significant morbidity and mortality
What does the brain consist of?
Cerebrum, brain stem and cerebellum
What is the cerebellum composed of?
Right and left hemispheres, separated by the falix cerebri
What does the left hemisphere contain?
The language centres
What does the frontal lobe control?
Executive function, emotions, motor function and on the dominant side, expression of speech
What does the parietal lobe direct?
Sensory function and spatial orientation
What does the temporal lobe regulate?
Certain memory functions
What is the occipital lobe responsible for?
Vision
What is the brain stem composed of?
The midbrain, pons and medulla
What does the midbrain and upper pond contain?
The reticular activating system which is responsible for the state of alertness
What resides in the medulla?
Vital cardiorespiratory centres
What is the cerebellum responsible for?
Coordination and balance, projects posteriorly in the posterior fossa and connects the spinal cord, brain stem and cerebral hemispheres
What are the ventricles in the brain?
A system of CFS filled spaces and aqueducts within the brain
Where is CSF constantly produced?
The ventricles
What is absorbed over the surface of the brain?
CSF
What can impair the reabsorption of CSF in the brain, resulting in increased intracranial pressure?
Blood
What separates the brain into regions?
Tough meninges partitions
What divides the intracranial cavity into the supratentorial and ifratentorial compartments?
Tentorium cerebelli
The mid brain passes through an opening called?
The tentorial hiatus or notch
What runs along the edge of the tentorium and may become compressed against it during temporal lobe herniation?
The oculomotor nerve / cranial nerve 3
Why does a patient get pupillary dilation or a ‘blown pupil’?
Parasympathetic fibres that constrict the pupils lie on the surface of the third cranial nerve and during herniation these fibres can become compressed causing this change, due to unopposed sympathetic activity
What is the tentorial notch?
The medial part of the temporal lobe known as the uncus
What is the part of the brain that is most likely to herniate?
The uncus/tentorial notch
What is caused by uncal herniation?
Compression of the corticospinal tract in the mid brain
What reduces cerebral perfusion causing or exacerbating ischemia?
Raised intracranial pressure
What is a normal ICP?
Approximately 10 mmHg
ICPs greater than 22 mmHg are associated with what?
Poor outcomes
What is the Monroe-Kellie doctorine?
It explains the dynamics of ICP. The total volume of intracranial contents must remain the same because the cranium is rigid that is incapable of expanding. When normal intracranial volume is exceeded ICP rises.
Why can ICP remain stable immediately after injury whilst a mass, such as a haematoma, can grow?
Venous blood and CFS can be compressed out of the cranium providing some degree of pressure buffering?
What happens to a patients ICP once the limit of displacement is reached?
It rapidly increases
What can diffuse axonal injuries range from?
Mild concussions to severe hypoxic, ischemic injuries
What are severe diffuse injuries often a result of?
A hypoxic ischemic insult on the brain, due to prolonged shock or impact brain apnoea
Where are diffuse injuries often seen in a head CT?
In the boarders between the great and white matter and are associated with poor outcomes
What is a grade 1 category diffuse axonal injury and what is the mortality %?
No visible intracranial injury, 10%
What is a grade 2 category diffuse axonal injury and what is the mortality %?
Cisterns present 0-5 mm midline shift and small, high or mixed density lesions, 14%
What is a grade 3 category diffuse axonal injury and what is the mortality %?
Cisterns compressed or absent + grade 1 or 2, 34%
What is a grade 4 category diffuse axonal injury and what is the mortality %?
Midline shift greater than 5 mm and grade 1,2 or 3, 56%
Where are extradural haematomas commonly located?
The temporal or temporoparietal regions
What are extradural haematomas often a result of?
A tear in the middle meningeal artery due to a fracture, disruption of a major venous sinus or bleeding from a skull fracture
How do patients who have a extradural haematoma typically present?
Following a period of lucidity post injury with rapid deterioration later on
What are subdural haematomas commonly a result of?
Shearing of small surface or bridging vessels of the cerebral cortex
Why is the damage underlying a subdural haematoma more severe than that of an extradural haematoma?
The presence of concomitant parenchymal injury
Can the primary injury/initial insult that has caused a TBI be reversed?
No
What is the management of a TBI aimed at?
Avoiding secondary injury caused by hypoxia and hypotension through the maintenance of adequate cerebral blood flow and the prevention of hypoxia
What do patient who have had a severe TBI require and why?
Mechanical ventilation to maintain arterial PO2 to about 11kP and PCO2 between 4.5 and 5 kPa
Why is it important to make sure that patients who have TBI have adequate sedation?
It minimises pain, anxiety and agitation
Reduces cerebral metabolic rate of oxygen consumption
Facilitates mechanical ventilation
Why is midazolam a commonly used sedation drug for patients with TBI and what is it’s downside?
It’s used due to its effectiveness as a sedative and anticonvulsant but accumulation may be an issue
Why is propofol a commonly used sedation drug for patients with TBI and what is it’s downside?
It’s superior metabolic suppressive effects and short half life however in hypothermic patients it has a tendency to accumulate and precipitate hyperlipidaemia. It has also been associated with cardiovascular collapse and the propofol infusion syndrome
What is the propofol infusion syndrome?
Acidosis, rhabdomyolysis and bradycardia
Why are neuromuscular blocks utilized for TBI patients?
To minimise coughing and straining
What drug is administered to provide neuromuscular block?
Rocuronium or atracurium
What does a reduction or PaCO2 cause?
Cerebral vasoconstriction, reducing cerebral blood volume and consequently ICP
If hyperventilation is utilised for TBI patients, what must be maintained?
A balance between the beneficial effects of ICP and potentially deleterious effects of cerebral blood flow
Following a TBI what can compound cerebral ischemia in the first 24 hours?
Induced hyperventilation
Why are TBI patients prone to haemodynamic instability?
Associated injuries may lead to intravascular volume depletion and trauma to the myocardium which can result in pump failure
What can brain stem injuries directly effect?
Cardiovascular stability
Why must hypotension be avoided at all costs for TBI patients?
It causes a reduction in cerebral blood flow and is likely a result of cerebral ischemia
Intravascular volume for TBI patients should be maintained with a target central venous pressure of 5-10 mmHg using what?
Isotonic crystalloids
What is a key intervention in the management of cerebral oedema and raised ICP?
Hyperosmolar therapy, such as mannitol or hypertonic saline
How does mannitol work?
- plasma expanding effect and improved blood rheology due to a reduction of haemocrit
- establishes an osmotic gradient between plasma and brain cells, reducing cerebral oedema by drawing water across areas of intact blood brain barrier into the vascular compartment
Why does repeated administration of mannitol become problematic?
It’s effect on serum osmolarity
Severe intravascular volume depletion
Hypotension
Hyperkalaemia
Rebound increase in ICP
How does hypertonic saline work?
It produces a reduction in cerebral oedema by moving water out of cells, reducing tissue pressure and cell size, resulting in a decrease in ICP
What drug improves cerebral blood flow, independently of ICP, by decreasing endothelial cell volume, increasing diameter of capillary lumen and reducing erythrocyte size thereby improving blood rheology?
Hypertonic saline
Why is hypertonic saline preferred over mannitol for patients with TBI?
Has proven efficacy in controlling ICP in patients refractory to mannitol and is also effective as a volume expander without causing hyperkalaemia and impaired renal function
