|
|
| Line 1: |
Line 1: |
| '''Cerebral perfusion pressure''', or '''CPP''', is the net [[pressure]] gradient causing [[cerebral blood flow]] to the brain (brain [[perfusion]]). It must be maintained within narrow limits because too little pressure could cause brain tissue to become [[ischemic]] (having inadequate blood flow), and too much could raise [[intracranial pressure]] (ICP).
| | Irwin Butts is what my wife enjoys to call me although I don't really like being known as like that. To collect cash is what his family and him appreciate. My working day occupation is a meter reader. Puerto Rico is where he and his wife reside.<br><br>Also visit my web blog - [http://immbooks.com/blogs/post/44599 std testing at home] |
| | |
| ==Definitions==
| |
| The cranium is a box with three components, Blood, Cerebral Spinal Fluid, and very soft tissue (brain). While both the blood and CSF have poor compression capacity, the brain is easily compressible.
| |
| Every increase of ICP can change a change in tissue perfusion and an increase in stroke events.
| |
| Comparisons of the relation between brain and body weights among extant mammals show that brain sizes have not increased as much as body sizes.http://www.sciencemag.org/content/220/4603/1302
| |
|
| |
| ===From resistance===
| |
| CPP can be defined as the pressure gradient causing [[cerebral blood flow]] (CBF) such that
| |
| | |
| : <math>CBF = CPP/CVR </math>
| |
| where:
| |
| :CVR is cerebrovascular resistance
| |
| | |
| ===By intracranial pressure===
| |
| An alternative definition of CPP is:<ref>{{cite doi|10.1093/bja/ael110}}</ref>
| |
| | |
| : <math>CPP=MAP-ICP</math>
| |
| | |
| where: | |
| :MAP is [[mean arterial pressure]]
| |
| :ICP is [[intracranial pressure]]
| |
| | |
| This definition may be more appropriate if considering the circulatory system in the brain as a [[Starling resistor]], where an external pressure (in this case, the intracranial pressure) causes decreased blood flow through the vessels. In this sense, more specifically, the cerebral perfusion pressure can be defined as either:
| |
| : <math> CPP = MAP - ICP </math> (if ICP is higher than JVP)
| |
| orL
| |
| : <math> CPP = MAP - JVP </math> (if JVP is higher than ICP).
| |
| | |
| Physiologically, increased [[intracranial pressure]] (ICP) causes decreased blood perfusion of [[brain cell]]s by mainly two mechanisms:
| |
| *Increased ICP constitutes an increased [[interstitial hydrostatic pressure]] that, in turn, causes a decreased [[Starling equation|driving force for capillary filtration]] from intracerebral blood vessels.
| |
| *Increased ICP compresses cerebral arteries, causing increased cerebrovascular resistance (CVR).
| |
| | |
| FLOW
| |
| Ranging from 20ml 100g-1 min-1 in white matter to 70ml 100g-1 min-1 in grey matter.
| |
| | |
| ==Autoregulation==
| |
| Static autoregulation: Under normal circumstances (MAP between 60 to 150 mmHg and ICP about 10 mmHg), average cerebral blood flow (e.g. the average recorded over 5 minutes or over hours) is relatively constant due to protective autoregulation.<ref name="Steiner">{{cite journal
| |
| | author=Steiner LA, Andrews PJ
| |
| | title=Monitoring the injured brain: ICP and CBF
| |
| | journal=[[British Journal of Anaesthesia]]
| |
| | volume=97 | issue=1 | year=2006 | pages=26–38
| |
| |url=http://bja.oxfordjournals.org/cgi/content/full/97/1/26
| |
| | pmid = 16698860
| |
| | doi=10.1093/bja/ael110
| |
| }}</ref><ref>{{cite journal | author=Duschek S, Schandry R | title=Reduced brain perfusion and cognitive performance due to constitutional hypotension
| |
| | journal=[[Clinical Autonomic Research]]
| |
| | volume=17 | issue=2 | year=2007 | pages=69–76 | pmid = 17106628 | doi=10.1007/s10286-006-0379-7 | pmc=1858602
| |
| }}</ref>
| |
| However, although the classic 'autoregulation curve' proposed by Lassen et al. suggests that CBF is fully stable between these blood pressure values (known also as the limits of autoregulation), in fact CBF may vary as much as 10% below and above its average within this range.<ref name="ReferenceA">van Beek AH, Claassen JA, Rikkert MG, Jansen RW. Cerebral autoregulation: an overview of current concepts and methodology with special focus on the elderly. J Cereb Blood Flow Metab. 2008 Jun;28(6):1071-85</ref>
| |
| Outside of the limits of autoregulation, raising MAP raises CPP and raising ICP lowers it (this is one reason that increasing ICP in [[traumatic brain injury]] is potentially deadly). CPP is normally between 70 and 90 [[mmHg]] in an adult human, and '''cannot go below 70 mmHg''' (interruption production of Cerebral Spinal Fluid) for a sustained period without causing [[ischemia|ischemic]] [[brain damage]],<ref name="Tolias and Sgouros">Tolias C and Sgouros S. 2003. [http://www.emedicine.com/med/topic3216.htm "Initial Evaluation and Management of CNS Injury."] Emedicine.com. Retrieved on March 19, 2007</ref><ref>{{cite journal
| |
| | author=Czosnyka M, Pickard JD
| |
| | title=Monitoring and interpretation of intracranial pressure
| |
| | journal= [[Journal of Neurology, Neurosurgery, and Psychiatry]]
| |
| | volume=75 | issue=6 | year=2004 | pages=813–821
| |
| | url=http://jnnp.bmj.com/cgi/content/full/75/6/813
| |
| | pmid = 15145991
| |
| | doi=10.1136/jnnp.2003.033126
| |
| | pmc=1739058
| |
| }}</ref>
| |
| although some authorities regard 50-150 mmHg as a normal range for adults.<ref name="Steiner"/>
| |
| Children require pressures of at least 60 mmHg.<ref name="Tolias and Sgouros"/>
| |
| | |
| Within the autoregulatory range, as CPP falls there is, within seconds, vasodilatation of the cerebral resistance vessels, a fall in cerebrovascular resistance and a rise in cerebral-blood volume (CBV), and therefore CBF will return to baseline value within seconds (see as ref. Aaslid, Lindegaard, Sorteberg, and Nornes 1989: http://stroke.ahajournals.org/cgi/reprint/20/1/45.pdf). These adaptations to rapid changes in blood pressure (in contrast with changes that occur over periods of hours or days) are known as dynamic cerebral autoregulation.<ref name="ReferenceA"/>
| |
| | |
| ==References==
| |
| {{Reflist}}
| |
| | |
| === Others ===
| |
| *Sanders MJ and McKenna K. 2001. ''Mosby’s Paramedic Textbook'', 2nd revised Ed. Chapter 22, "Head and Facial Trauma." Mosby.
| |
| * {{Cite journal
| |
| | author = Walters, FJM.
| |
| | year = 1998
| |
| | url = http://www.nda.ox.ac.uk/wfsa/html/u08/u08_013.htm
| |
| | title = Intracranial Pressure and Cerebral Blood Flow
| |
| | journal = [[Physiology (journal)|Physiology]]
| |
| | issue = 8, Article 4
| |
| | accessdate = 10 February 2011
| |
| }}
| |
| | |
| [[Category:Medical terminology]]
| |
| [[Category:Neurology]]
| |
| [[Category:Neurotrauma]]
| |
| [[Category:Physiology]]
| |
Irwin Butts is what my wife enjoys to call me although I don't really like being known as like that. To collect cash is what his family and him appreciate. My working day occupation is a meter reader. Puerto Rico is where he and his wife reside.
Also visit my web blog - std testing at home