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).
The cranium encloses a fixed-volume space that holds three components: blood, cerebrospinal fluid (CSF), and very soft tissue (the brain). While both the blood and CSF have poor compression capacity, the brain is easily compressible.
Every increase of ICP can cause a change in tissue perfusion and an increase in stroke events.
From resistanceedit
CPP can be defined as the pressure gradient causing cerebral blood flow (CBF) such that
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:
(if ICP is higher than JVP)
or
(if JVP is higher than ICP).
Physiologically, increased intracranial pressure (ICP) causes decreased blood perfusion of brain cells by mainly two mechanisms:
FLOW Ranging from in white matter to in grey matter.
Autoregulationedit
Under normal circumstances a MAP between 60 and 160 mmHg and ICP about 10 mmHg (CPP of 50-150 mmHg) sufficient blood flow can be maintained with autoregulation.[1][2] Although the classic 'autoregulation curve' suggests that CBF is fully stable between these blood pressure values (known also as the limits of autoregulation), in practice spontaneous fluctuations can occur.[3]
Outside of the limits of autoregulation, raising MAP raises CBF and raising ICP lowers it (this is one reason that increasing ICP in traumatic brain injury is potentially deadly). In trauma some recommend CPP not go below 70 mmHg.[4][5] Recommendations in children is at least 60 mmHg.[4]
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.[3]
Footnotesedit
^ abSteiner, LA; Andrews, PJ (2006). "Monitoring the injured brain: ICP and CBF". British Journal of Anaesthesia. 97 (1): 26–38. doi:10.1093/bja/ael110. PMID 16698860.
^Duschek, S; Schandry, R (2007). "Reduced brain perfusion and cognitive performance due to constitutional hypotension". Clinical Autonomic Research. 17 (2): 69–76. doi:10.1007/s10286-006-0379-7. PMC1858602. PMID 17106628.
^ abvan Beek, AH; Claassen, JA; Rikkert, MG; Jansen, RW (June 2008). "Cerebral autoregulation: An overview of current concepts and methodology with special focus on the elderly". Journal of Cerebral Blood Flow & Metabolism. 28 (6): 1071–85. doi:10.1038/jcbfm.2008.13. hdl:2066/80163. PMID 18349877.
^ abTolias, C; Sgouros, S (2003). . Emedicine.com. Archived from the original on March 2, 2007. Retrieved 2007-03-19.
Sanders, MJ; McKenna, K (2001). "Ch. 22: Head and Facial Trauma". Mosby's Paramedic Textbook (2nd revised ed.). Mosby.
Walters, FJM (1998). . Physiology (8, Article 4). Archived from the original on 2011-05-14. Retrieved 2011-02-10.
December 15, 2023
cerebral, perfusion, pressure, pressure, gradient, causing, cerebral, blood, flow, brain, brain, perfusion, must, maintained, within, narrow, limits, because, little, pressure, could, cause, brain, tissue, become, ischemic, having, inadequate, blood, flow, muc. 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 Contents 1 Definitions 1 1 From resistance 1 2 By intracranial pressure 2 Autoregulation 3 Footnotes 4 ReferencesDefinitions editThe cranium encloses a fixed volume space that holds three components blood cerebrospinal fluid CSF and very soft tissue the brain While both the blood and CSF have poor compression capacity the brain is easily compressible Every increase of ICP can cause a change in tissue perfusion and an increase in stroke events From resistance edit CPP can be defined as the pressure gradient causing cerebral blood flow CBF such that C B F C P P C V R displaystyle CBF CPP CVR nbsp where CVR is cerebrovascular resistanceBy intracranial pressure edit An alternative definition of CPP is 1 C P P M A P I C P displaystyle CPP MAP ICP nbsp where MAP is mean arterial pressure ICP is intracranial pressure JVP is jugular venous pressureThis 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 C P P M A P I C P displaystyle CPP MAP ICP nbsp if ICP is higher than JVP or C P P M A P J V P displaystyle CPP MAP JVP nbsp if JVP is higher than ICP Physiologically increased intracranial pressure ICP causes decreased blood perfusion of brain cells by mainly two mechanisms Increased ICP constitutes an increased interstitial hydrostatic pressure that in turn causes a decreased driving force for capillary filtration from intracerebral blood vessels Increased ICP compresses cerebral arteries causing increased cerebrovascular resistance CVR FLOW Ranging from 20 mL 100 g min displaystyle 20 textrm mL 100 textrm g cdot textrm min nbsp in white matter to 70 mL 100 g min displaystyle 70 textrm mL 100 textrm g cdot textrm min nbsp in grey matter Autoregulation editUnder normal circumstances a MAP between 60 and 160 mmHg and ICP about 10 mmHg CPP of 50 150 mmHg sufficient blood flow can be maintained with autoregulation 1 2 Although the classic autoregulation curve suggests that CBF is fully stable between these blood pressure values known also as the limits of autoregulation in practice spontaneous fluctuations can occur 3 Outside of the limits of autoregulation raising MAP raises CBF and raising ICP lowers it this is one reason that increasing ICP in traumatic brain injury is potentially deadly In trauma some recommend CPP not go below 70 mmHg 4 5 Recommendations in children is at least 60 mmHg 4 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 3 Footnotes edit a b Steiner LA Andrews PJ 2006 Monitoring the injured brain ICP and CBF British Journal of Anaesthesia 97 1 26 38 doi 10 1093 bja ael110 PMID 16698860 Duschek S Schandry R 2007 Reduced brain perfusion and cognitive performance due to constitutional hypotension Clinical Autonomic Research 17 2 69 76 doi 10 1007 s10286 006 0379 7 PMC 1858602 PMID 17106628 a b van Beek AH Claassen JA Rikkert MG Jansen RW June 2008 Cerebral autoregulation An overview of current concepts and methodology with special focus on the elderly Journal of Cerebral Blood Flow amp Metabolism 28 6 1071 85 doi 10 1038 jcbfm 2008 13 hdl 2066 80163 PMID 18349877 a b Tolias C Sgouros S 2003 Initial evaluation and management of CNS injury Emedicine com Archived from the original on March 2 2007 Retrieved 2007 03 19 Czosnyka M Pickard JD 2004 Monitoring and interpretation of intracranial pressure Journal of Neurology Neurosurgery and Psychiatry 75 6 813 21 doi 10 1136 jnnp 2003 033126 PMC 1739058 PMID 15145991 References editSanders MJ McKenna K 2001 Ch 22 Head and Facial Trauma Mosby s Paramedic Textbook 2nd revised ed Mosby Walters FJM 1998 Intracranial Pressure and Cerebral Blood Flow Physiology 8 Article 4 Archived from the original on 2011 05 14 Retrieved 2011 02 10 Retrieved from https en wikipedia org w index php title Cerebral perfusion pressure amp oldid 1170996397, wikipedia, wiki, book, books, library,
