Calculation of cerebral perfusion pressure in the management of traumatic brain injury: joint position statement by the councils of the Neuroanaesthesia and Critical Care Society of Great Britain and Ireland (NACCS) and the Society of British Neurological Surgeons (SBNS)

Abstract

The councils of the Neuroanaesthesia and Critical Care Society of Great Britain and Ireland (NACCS) and the Society of British Neurological Surgeons (SBNS) acknowledge that there has been recent controversy regarding the evidence base for the measurement of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) and that questions regarding ICP- and CPP-directed management remain unanswered. Currently, however, monitoring and management of ICP and CPP based on the Brain Trauma Foundation Guidelines1https://www.braintrauma.org/pdf/protected/Guidelines_Management_2007w_bookmarks.pdfGoogle Scholar remains a standard of care following traumatic brain injury (TBI). This has recently been reviewed2Kirman 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; 112: 35-46Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar and previously in an editorial.3Kosty JA Kofke WA On a not-dead horse: CPP deserves more respect.J Neurosurg Anaesthesiol. 2012; 24: 1-2Crossref PubMed Scopus (3) Google Scholar The calculation of CPP is an integral part of this strategy, as described by Rosner and colleagues4Rosner MJ Rosner SD Johnson AH Cerebral perfusion pressure: management protocol and clinical results.J Neurosurg. 1995; 83: 949-962Crossref PubMed Scopus (742) Google Scholar in their seminal paper. In their article, the mean arterial pressure (MAP) used was measured in supine patients at the level of the middle cranial fossa to estimate transcranial perfusion, described by the following equation: CPP=MAP−ICP In 2013, Subhas, Wilson and Jain conducted a national survey of CPP measurement practices in Great Britain and Ireland. Their results were presented at the NACCS meeting in Cardiff and the abstract published.5Subhas K Wilson SR Jain R Survey of cerebral perfusion pressure measurement practices in Great Britain and Ireland.J Neurosurg Anaesthesiol. 2013; 25: 362Google Scholar They revealed that, in calculating CPP, 58% of neurosurgical intensive care units place the arterial transducer at the level of the heart and 42% place it at the level of the tragus. No-one routinely nursed their patients in the supine position, and 84% nursed patients 30 degrees head-up. They also demonstrated that 94% of respondents wished NACCS to endorse a consensus statement on standardization of CPP measurement practices in Great Britain and Ireland. This has been considered by the Councils of NACCS and SBNS, who wish to make the following joint statements. Councils of NACCS and SBNS recommend that all research articles relating to CPP measurement or CPP-derived variables in the management of TBI should explicitly state in their methodology where the arterial transducer was positioned (levelled) for relevant measurements. Councils endorse positioning (levelling) the arterial transducer at the level of the middle cranial fossa, which can be approximated to the tragus of the ear. Whilst not wishing to dictate local clinical practice, based on the available evidence, the Councils of NACCS and SBNS would recommend that when calculating CPP in TBI the MAP used in the equation CPP=MAP−ICP should be the mean cerebral arterial pressure estimated to exist at the level of the middle cranial fossa, which can be approximated by positioning (levelling) the arterial transducer at the tragus of the ear. They also recommend that the arterial transducer is repositioned to remain levelled with the tragus following changes in body elevation or position. Councils do not endorse positioning (levelling) the arterial transducer at heart level (phlebostatic axis) for CPP-based treatment decisions because there is a requirement for subsequent cerebral MAP to be calculated, which is dependent on the relationship: MAPbrain=MAPheart−(watercolumnbetweenheartandbrain×C) where C is a coefficient, always lower than 1, dependent on conditions of both the arterial and the venous elements of the cerebral circulation, which is not reliably predictable and is variable between individuals. Centres that wish to continue to position (level) their arterial transducers at the level of the heart for CPP-based TBI management should have explicit guidance within their TBI protocols on how they take account of this difference and its subsequent effect on individual CPP calculation for patient management. None declared. Download .zip (.0 MB) Help with zip files