cerebral autoregulation

[Sonny Crocket]

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I am a little confused about cerebral autoregulation. The brain has autoregulation from MAPs of 60 to 160. And in a hypertensive patient the curve is shifted to the right. A few of my attending have told me to keep a hypertensive patient's MAP higher during a case as compared to a normotensive patient in order to maintain CPP.

I've read that volatile anesthetics impair autoregulation in a dose dependent manner. So if there is no autoregulation then can't we just keep MAP in the 'normal' range without it affecting CPP?

Thanks!

 

[SleepIsGood]

I am a little confused about cerebral autoregulation. The brain has autoregulation from MAPs of 60 to 160. And in a hypertensive patient the curve is shifted to the right. A few of my attending have told me to keep a hypertensive patient's MAP higher during a case as compared to a normotensive patient in order to maintain CPP.

I've read that volatile anesthetics impair autoregulation in a dose dependent manner. So if there is no autoregulation then can't we just keep MAP in the 'normal' range without it affecting CPP?

Thanks!

You got it.

As long as the MAC is kept less than 1.0 (ie supplement with opiod,etc).

In reality under GETA all that stuff is meaningless since like you said autoregulation is abolished.

I think we learn about the curves and autoregulation since we are PERIOP physicians therefore these things need to be kept in mind preop and post op in the SICU for our patients..

Other thing to realize, why this stuff isnt all that pertinent under GETA....almost all the inhalation agents will decrease CMRO2 and cerebral metabolism making the brains requirements less.

 

[Eta Carinae]

specifically at 1.5MAC, Isoflurane and Desflurane will ablate cerebral autoregulation. Propofol, however, preserves it.

furthermore sevoflurane is better at preserving cerebral autoreg than isoflurane.



Stephan et.al. Dynamic and Static Cerebral Autoregulation during Isoflurane, Desflurane, and Propofol Anesthesia. Anesthesiology:
July 1995 - Volume 83 - Issue 1 - pp 66-76

Summors et.al. Dynamic Cerebral Autoregulation During Sevoflurane Anesthesia: A Comparison with Isoflurane. Anesth Analg 1999;88:341

 

[SleepIsGood]

INhal agents will vasodil blood vessels and increase blood flow to the brain.

IV agents (propofol,etc) will decrease/maintain blood flowtothe brain...

 

[pgg]

The brain has autoregulation from MAPs of 60 to 160.

The lower limit of autoregulation (LLA) has been widely quoted as an MAP of 50 mm Hg. Although this number may be correct for some animal species, the available data argue that the LLA is considerably higher in humans.

FWIW, the 50-150 or 60-160 numbers passed down as dogma probably aren't quite right, at least on the low end. All the more reason to be even more conservative in people you think are right shifted.