Neurocritical Care Viva (WM)

Question 1

What are the equivalent doses of hydrocortisone and prednisolone to dexamethasone 0.75mg?

Answer 1

Hydrocortisone 20mg

Prednisolone 5mg

Question 2

What’s the sequence of the three phases of the triphasic response after pituitary surgery?

Answer 2

DI (axonal injury) –> SIADH (axonal necrosis with ADH release) –> DI (cell death)

Question 3

Draw the Lassen Curve? (or describe key features)

Answer 3

Y axis
CBF in ml/100g/min - 50 is usual
X axis
MAP
Autoregulation between 50 and 150mmHg
CO2
Flat with CBF of approx 25 with CO2 of 3kPa
Then goes up until CO2 of abotu 12Kpa with CBF of approx 90ml/100mg/min
PAO2 (no line until 25) then falls from CBF of about 90 until PA02 is about 10 corresponding to CBF of about 50

Question 4

What’s the CMRO2 of brain (on average and white and grey))

Answer 4

3ml/100g/min (4ml/100g/min grey, 1ml/100g/min white)

Question 5

What’s cerebral blood flow average (grey and white)

Answer 5

50ml/mg/min average (70ml/mg/min in grey and 30ml/mg/min in white)

Question 6

What values of P02, PC02 and MAP would you set to optimise a head injury for transfer?

Answer 6

O2 >13
PC02 4.5-5
MAP 80

Question 7

What are the three peaks of the ICP waveform

Answer 7

P1 (highest) - percussion, arterial pulsation
P2 (middle) - tidal wave, brain compliance
P3 (lowest) - dicrotic wave, closure of aortic valve

Question 8

How does ICP waveform change in acute brain injury

Answer 8

In acute brain injury compliance starts decreasing resulting in reversal of P1:P2 ratio

Question 9

What is PRx?

Answer 9

It the correlation coefficient between ICP and CPP over 5 mins

Question 10

Draw the PRx CPP curve

Answer 10

U shaped curve
PRx on y axis
CPP on x axis

Question 11

How can you use PRx?

Answer 11

To refine the CPP target (usually 60-70mmHg) from brain trauma foundation

Question 12

How would you manage a head injury patient?

Answer 12

ATLS
A - tube, 30 degrees head up, collar
B - SpO2 >93% PAO2>13 PAO2 PAC02 4.5-5
C - MAP 80 CPP 60-70 PRX
D - normoglycaemia - but not tight glycaemic control

Question 13

Would you give anticonvulsants in head injury? What’s the evidence

Answer 13

Reduction in early but not late seizures. Temkin 1990 NEJM Phenytoin

Question 14

Describe the Marshall classification

Answer 14

I - normal scan
II - shift of less than 5mm, basal cisterns patent, no mass lesion >25cc (diffuse injury)
III - shift less than 5mm, no lesions >25cc, basal cisterns compressed (diffuse with swelling)
IV - shift of >5mm, no lesions 25cc
V - evacuated mass lesion
VI - unevacuated mass lesion >25cc

Question 15

What bedside tests can you do for ICP compliance?

Answer 15

Jugular venous occlusion (rate of response)
Lie flat
CO2 challenge

Question 16

Describe lundberg waves

Answer 16

Lundberg A waves - steep increases in ICP lasting 5-20minutes (probably pathological)
Lundberg B waves - 30 second to 2 minutes
Lundberg C waves - 4-8 waves per minute (physiological)

Question 17

Describe adams classification for DAI

Answer 17

Adams grading
1 - grey white interface
2 - grey white + corpus callosum
3 - brain stem
Does not correlate well

Question 18

What is normal cerebral oxygen extraction fraction?

Answer 18

0.2-0.3