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cerebral_perfusion_pressure

Cerebral perfusion pressure

Insufficient cerebral perfusion pressure (CPP) after aneurysmal subarachnoid hemorrhage can impair cerebral blood flow.

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).

An alternative definition of CPP is:

The difference between the mean arterial blood pressure (MAP) and the ICP (CPP = MAP-ICP), and therefore it is a calculated variable.

where:

MAP is mean arterial pressure

ICP is intracranial pressure.


Guidelines recommend cerebral perfusion pressure (CPP) values of 50-70 mmHg and intracranial pressure lower than 20 mmHg for the management of acute traumatic brain injury (TBI). However, adequate individual targets are still poorly addressed, since patients have different perfusion thresholds 1).

A CPP > 60 mm Hg emerges as the crucial factor guaranteeing sufficient brain oxygenation. Any intervention used to further elevate CPP does not improve cerebral oxygenation, to the contrary, forced hyperventilation even bears the risk of inducing brain ischemia, but no class I evidence can currently advise the ideal CPP for any form of traumatic brain injury. 'Optimal' CPP is likely patient-, time-, and pathology-specific. Further, CPP estimation requires correct referencing (at the level of the foramen of Monro as opposed to the level of the heart) for MAP measurement to avoid CPP over-estimation and adverse patient outcomes 2) 3).

Aggressive CPP therapy should be performed and maintained even though apparently lethal ICP levels may be present. Further study is needed to support these encouraging results 4).

Management protocol

1)
Dias C, Silva MJ, Pereira E, Monteiro E, Maia I, Barbosa S, Silva S, Honrado T, Cerejo A, Aries MJ, Smielewski P, Paiva JA, Czosnyka M. Optimal Cerebral Perfusion Pressure Management at Bedside: A Single-Center Pilot Study. Neurocrit Care. 2015 Jan 8. [Epub ahead of print] PubMed PMID: 25566826.
2)
Kirkman MA, Smith M. Intracranial pressure monitoring, cerebral perfusion pressure estimation, and ICP/CPP-guided therapy: a standard of care or optional extra after brain injury? Br J Anaesth. 2014 Jan;112(1):35-46. doi: 10.1093/bja/aet418. Epub 2013 Nov 28. PubMed PMID: 24293327.
3)
Unterberg AW, Kiening KL, Härtl R, Bardt T, Sarrafzadeh AS, Lanksch WR. Multimodal monitoring in patients with head injury: evaluation of the effects of treatment on cerebral oxygenation. J Trauma. 1997 May;42 (5 Suppl):S32-7. PubMed PMID: 9191693.
4)
Young JS, Blow O, Turrentine F, Claridge JA, Schulman A. Is there an upper limit of intracranial pressure in patients with severe head injury if cerebral perfusion pressure is maintained? Neurosurg Focus. 2003 Dec 15;15(6):E2. Review. PubMed PMID: 15305838.
cerebral_perfusion_pressure.txt · Last modified: 2017/11/29 12:23 by administrador