Clinical aspects of cerebral perfusion and intercranial pressure

Question 1

what are the main pathophysiological processes in a case of raised ICP?

Answer 1

haemorrhage - “mass effect”
disruption of blood brain barrier - raised ECF
membrane failure - influx of calcium - cellular swelling
influx of inflammatory mediators

Question 2

what are some secondary effects of raised ICP?

Answer 2

herniation syndromes

decreased cerebral perfusion

Question 3

what is the monro kellie doctrine?

Answer 3

volume of:
CSF
Blood
Brain
Other cranial contents
constitute the volume of the intracranial space and that must remain CONSTANT

Question 4

what determines the cerebral perfusion pressure?

Answer 4

Mean arterial pressure minus the ICP

Question 5

what is the normal value of CPP?

Answer 5

80mmHg

Question 6

what is the normal value for MAP?

Answer 6

90mmHg

Question 7

what is the normal ICP?

Answer 7

5-15mmHg

Question 8

what determines the MAP?

Answer 8

diastolic BP plus 1/3 pulse pressure

Question 9

what type of respiration does the brain use to produce virtually all of its ATP?

Answer 9

aerobic

Question 10

what happens if the brain is deprived of oxygen?

Answer 10

energy dependent processes cease, leading to irreversible cellular injury within 3-8 minutes

Question 11

what are some factors that regulate cerebral blood flow?

Answer 11

autoregulation
cerebral metabolism
carbon dioxide and oxygen
neurohumoral factors

Question 12

what is the response of vascular smooth muscle to an increase in wall tension in blood vessels?

Answer 12

constricts

Question 13

what cortex is affected in subfalcine herniation?

Answer 13

medial motor cortex

Question 14

what structures are affected in uncal herniation?

Answer 14

3rd CN

ipsilateral corticospinal tracts

Question 15

what structures are affected in foramen magnum herniation?

Answer 15

brain stem centres

Question 16

what drug is given to treat raised ICP?

Answer 16

mannitol

Question 17

how is a patient with raised ICP managed in ITU?

Answer 17

head position - 30 degress up
nothing to impede venous drainage
CO2 maintained in low normal range
intermittent boluses of mannitol when ICP raised
fully sedated and paralysed

Question 18

why is the pupil fixed and dilated in head trauma?

Answer 18

compression of the parasympathetic supply to the eye (edinger westphal nucleus of oculomotor nerve and disruption of the ciliary ganglion) leads to uncontested sympathetic innervation