Time for a #factcheck on cerebral autoregulation.
1/10
"Cerebral autoregulation is the mechanism that keeps cerebral blood flow (CBF) stable across a wide range of perfusion pressure".
WRONG. But widespread... This is only true for very slow changes in blood pressure (BP).
1/10
"Cerebral autoregulation is the mechanism that keeps cerebral blood flow (CBF) stable across a wide range of perfusion pressure".
WRONG. But widespread... This is only true for very slow changes in blood pressure (BP).
2/10 For faster changes in BP, CBF changes almost as much as BP. E.g. the 10-20% drop in BP when we stand up leads to a 10-20% drop in CBF. Autoregulation can not prevent this drop, it only makes sure CBF recovers before BP does.
3/10 Slow BP changes: examples are treatment of hypertension, or gradual decline in BP during sepsis. Indeed, here CBF is maintained more or less stable. Fast changes: seconds to minutes: standing up, or an acute dose of nitroglycerine, or a Valsalva. CBF is NOT held stable here.
4/10 "Cerebral autoregulation involves vascular, metabolic and neural mechanisms"
WRONG. But also widespread. 'Neural mechanisms': people mean neurovascular coupling. That is a different mechanism. You 'could' call it autoregulation, because CBF adapts to local neural demand..
WRONG. But also widespread. 'Neural mechanisms': people mean neurovascular coupling. That is a different mechanism. You 'could' call it autoregulation, because CBF adapts to local neural demand..
5/10 But neurovascular coupling stands apart from cerebral autoregulation, which is autoregulation to changes in BP and has, to date, no strong evidence for neural involvement.
'Metabolic' also refers, really, to neurovascular coupling. Or it confuses carbon dioxide reactivity.
'Metabolic' also refers, really, to neurovascular coupling. Or it confuses carbon dioxide reactivity.
6/10 CBF has a strong response to changes in carbon dioxide, so 'metabolic'. But I would not call this autoregulation. Again, a carbon dioxide reactivity is a CBF mechanism on its own.
7/10 So for whoever is writing the next paper or chapter on autoregulation: please do NOT start your introduction with these widespread but incorrect statements. Autoregulation can NOT always keep CBF completely stable, and NO it does not involve neural and metabolic mechanisms.
8/ Further reading 1: our review in Physiological Rev:
doi.org/10.1152/physre…
@Pat_Brassard's opinion piece on the dogmatic view on autoregulation in Phys Rep: doi.org/10.14814/phy2.…
doi.org/10.1152/physre…
@Pat_Brassard's opinion piece on the dogmatic view on autoregulation in Phys Rep: doi.org/10.14814/phy2.…
9/ Further reading 2
@RyanLeoHoiland's review on CO2 reactivity doi.org/10.1002/cphy.c…
@costantinoiade1 comprehensive review on neurovascular coupling doi.org/10.1016/j.neur…
@RyanLeoHoiland's review on CO2 reactivity doi.org/10.1002/cphy.c…
@costantinoiade1 comprehensive review on neurovascular coupling doi.org/10.1016/j.neur…
10/10 and to end in #10tweetsaboutautorregulation, a picture. 
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