Clinical Aspects of Cerebral Perfusion and ICP Flashcards
Pathophysiological process of raised ICP
Disruption of the blood brain barrier e.g. due to mass effect of haemorrhage
Increased ECF volume
Membrane failure, influx of calcium, cellular swelling
Influx of inflammatory mediators
Brain swelling
Raised ICP
Secondary effects of raised ICP
Anatomical e.g. herniation syndromes
Cellular e.g. decreased cerebral perfusion
Causes of raised ICP
Mass lesions Cerebral oedema Excess CSF - obstruction to CSF circulation/impaired CSF absorption Haemorrhage Swelling Aneurysm Blood pooling Trauma Infection Hydrocephalus Hypertension Stroke
Pathophysiology of raised ICP in relation to cerebral blood flow
Decreased cerebral blood flow Tissue hypoxia Increased pCO2, decreased pH Cerebral vasodilation and oedema Increased ICP
Consequences of raised ICP
Crush brain tissue Shift brain structures Contribute to hydrocephalus Brain herniation Restrict blood supple to brain
Symptoms of raised ICP
Headache Blurred vision Less alert Vomiting Behavioural changes Weakness Problems moving/talking Lack of energy/tiredness
What is the Monro-Kellie hypothesis?
Pressure-volume relationship between ICP, volume of CSF, blood and brain tissue and cerebral perfusion pressure
The cranium and its constituents create a state of
volume equilibrium
What is cerebral autoregulation?
Maintenance of constant cerebral blood flow despite changes in cerebral perfusion pressure, where CPP = MAP - ICP
How does autoregulation work?
Myogenic mechanism, vascular smooth muscle constricts in response to increase in wall tension
Autoregulation aims to
maintain adequate and stable cerebral blood flow
By means of auto regulation, the body is able to
maintain sufficient blood supply to the brain and to remove waste products
