Document Detail

Dynamic cerebral autoregulation: should intracranial pressure be taken into account?
MedLine Citation:
PMID:  17476455     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Although the inclusion of cerebral perfusion pressure (CPP) is a standard feature in static testing of autoregulation after head injury, controversy surrounds the use of CPP versus arterial blood pressure (ABP) in dynamic tests. The aim of our project was to assess the discrepancies between methods of dynamic autoregulation testing based on CPP or ABP, and study possible differences in their prognostic value.
METHOD: Intermittent recordings of intracranial pressure (ICP), ABP and middle cerebral artery blood flow velocity (FV) waveforms were made in 151 anaesthetised and ventilated adult head injured patients as part of their required care. Indices of dynamic autoregulation were calculated as a moving correlation coefficient of 60 samples (total time 3 min) of 6 s mean values of FV and ABP (Mxa) or FV and CPP (Mx). Values of Mx and Mxa were averaged over multiple recordings in each patient and correlated with outcome at 6 months post injury.
FINDINGS: Association between Mx and Mxa was moderately strong (r(2) = 0.73). However, limit of 95% accordance between both indices was +/-0.32. Mxa was significantly greater than Mx (0.22 +/- 0.22 versus 0.062 +/- 0.28; p < 0.000001). The difference between Mx and Mxa decreased with impairment of autoregulation (r = -0.39; p < 0.000001). Mean value of Mx showed a significant difference between dichotomized outcome groups (better autoregulation in patients with favourable than unfavourable outcome), while Mxa did not.
CONCLUSIONS: Although relatively similar in a large group of patients, the differences between these two methods of assessment of dynamic autoregulation may be considerable in individual cases. When ICP is monitored, CPP rather than ABP should be included in the calculation of the autoregulatory index.
P M Lewis; P Smielewski; J D Pickard; M Czosnyka
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-05-03
Journal Detail:
Title:  Acta neurochirurgica     Volume:  149     ISSN:  0942-0940     ISO Abbreviation:  Acta Neurochir (Wien)     Publication Date:  2007 Jun 
Date Detail:
Created Date:  2007-05-28     Completed Date:  2008-01-18     Revised Date:  2014-02-19    
Medline Journal Info:
Nlm Unique ID:  0151000     Medline TA:  Acta Neurochir (Wien)     Country:  Austria    
Other Details:
Languages:  eng     Pagination:  549-55; discussion 555     Citation Subset:  IM    
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MeSH Terms
Blood Flow Velocity / physiology
Blood Pressure / physiology*
Brain / blood supply*
Brain Injuries / physiopathology*,  therapy
Critical Care
Homeostasis / physiology*
Intracranial Pressure / physiology*
Middle Cerebral Artery / physiopathology
Statistics as Topic
Ultrasonography, Doppler, Transcranial
Grant Support
G0001237//Medical Research Council

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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