Cerebral blood flow

Some brain-specific figures:

• 1400g by weight
• 15% of cardiac output
• 20% of total basal oxygen consumption

NB:

• Total cardiac output = 5L/min
• Total basal oxygen consumption = 250mL/min
• O2 content of arterial blood = 20mL per 100mL blood

Cerebral blood flow (CBF)

CBF
= 15% of cardiac output
= 750mLs blood/min
= 50-54mLs/min/100g

Thus, O2 flux = 150mL O2/min delivered

Cerebral metabolic rate of oxygen consumption

(i.e. CMRO2)

CMRO2
= 20% of total basal oxygen consumption
= 50 mLs O2/min
= 3-3.5mLs O2/min/100g

NB:

• Grey matter uses 70mLs O2/min
• White matter uses 20mLs O2/min

O2 extraction ratio in brain

= CMRO2/O2 flux

= 50/150

= 33%