Part 1 - Maladaptive Changes of TBI Flashcards
Adults - What is Raised ICP?
Raised ICP is when there is an increase in volume in the limited space of the cranial cavity (Story, 2017).
Adults - What happens when ICP is raised?
Raised pressure, compresses the structures of the brain, usually vascular and this leads to a decrease in the nutrient and oxygen-rich blood flow getting to the cells of the brain (neurons and neuroglia) this impairs the removal of waste products such as carbon dioxide. (Cook et al. 2022).
Adults - What causes raised ICP?
caused by an accumulation of blood from the haematoma, or cerebral oedema
Adults - what happens to CPP and CBF as ICP rises?
When ICP rises, cerebral perfusion pressure (CPP) and cerebral blood flow (CBF) falls and leads to an ischaemic injury.
Ischaemia results in permanent neurological injury or death
Adults - How does the brain compensate?
The adult brain tries to compensate for an increase in ICP by reducing the amount of Cerebral Spinal Fluid (CSF)
Children - what is different about an immature brain?
Newborn babies have raised fontanelles and open skull sutures, which act as pressure release valves and allow for some expansion, allowing them to tolerate an increase in ICP.
However, Anderson and Yates (2010) suggest that the younger brain has a higher water content and is less compressible, which means that the younger brain is more susceptible to elevations in ICP
The bridging cortical vein is also thinner and more fragile in children, making it more susceptible to the acceleration / deceleration injuries
Geriatric - What changes occur in the older brain?
Changes associated with normal ageing cause the cerebral blood vessels to become more fragile, the subdural space becomes enlarged and the supportive tissues of the meninges decrease - making them more vulnerable to intracranial bleeding (Caroline, 2014).
Brain atropy can help to compensate for the haematoma, as there is more space in the cranial cavity for the haematoma to fill (Cook, et al. 2022).
Geriatric - what happens to ICP?
Wilson et al. (2023) suggests that ICP tends to decrease with age, possibly due to cerebral atrophy.
Raised ICP –> Cerebral Ischaemia
What causes ischaemia?
When ICP is raised and there is damage to cerebral perfusion, the lack of perfusion, blood flow and oxygen, results in ischamia.
Delayed ischaemia can be as a result of the secondary injury cascade
How does the body adapt to Ischaemia?
Autoregulation
How do autoregulatory mechanisms respond?
Autoregulatory mechanisms respond by dilating cerebral blood vessels to increase blood flow to the affected areas. However, this is only a short-term response.
How does the brain increase o2 levels with autoregulation?
The brain increases its ability to extract oxygen from the blood allow the brain tissue to make better use of the limited oxygen available. However this is not possible with severe ischaemia as the oxygen levels are too low.
What metabolic adaptions occur as a result of Autoregulation?
Brain cells switch to anaerobic metabolism to produce ATP. however this is far less efficient.
How does the body respond to a decrease in CPP as a result of Autoregulation?
the brain responds to a decrease in CPP by increasing the MAP - which results in cerebral vasodilation and increase in CBD, however as this increases there is a further rise in ICP. (Caroline, 2014).
As ICP rises the CBF is forced from the cranium into the spinal cord.
Children and autoregulation
