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Transcranial Doppler Pulsatility Index: What it is and What it Isn't.
MedLine Citation:
PMID:  22311229     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
BACKGROUND: Transcranial Doppler (TCD) pulsatility index (PI) has traditionally been interpreted as a descriptor of distal cerebrovascular resistance (CVR). We sought to evaluate the relationship between PI and CVR in situations, where CVR increases (mild hypocapnia) and decreases (plateau waves of intracranial pressure-ICP). METHODS: Recordings from patients with head-injury undergoing monitoring of arterial blood pressure (ABP), ICP, cerebral perfusion pressure (CPP), and TCD assessed cerebral blood flow velocities (FV) were analyzed. The Gosling pulsatility index (PI) was compared between baseline and ICP plateau waves (n = 20 patients) or short term (30-60 min) hypocapnia (n = 31). In addition, a modeling study was conducted with the "spectral" PI (calculated using fundamental harmonic of FV) resulting in a theoretical formula expressing the dependence of PI on balance of cerebrovascular impedances. RESULTS: PI increased significantly (p < 0.001) while CVR decreased (p < 0.001) during plateau waves. During hypocapnia PI and CVR increased (p < 0.001). The modeling formula explained more than 65% of the variability of Gosling PI and 90% of the variability of the "spectral" PI (R = 0.81 and R = 0.95, respectively). CONCLUSION: TCD pulsatility index can be easily and quickly assessed but is usually misinterpreted as a descriptor of CVR. The mathematical model presents a complex relationship between PI and multiple haemodynamic variables.
Authors:
Nicolás de Riva; Karol P Budohoski; Peter Smielewski; Magdalena Kasprowicz; Christian Zweifel; Luzius A Steiner; Matthias Reinhard; Neus Fábregas; John D Pickard; Marek Czosnyka
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-2-4
Journal Detail:
Title:  Neurocritical care     Volume:  -     ISSN:  1556-0961     ISO Abbreviation:  -     Publication Date:  2012 Feb 
Date Detail:
Created Date:  2012-2-7     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101156086     Medline TA:  Neurocrit Care     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Hills Road, Box 167, Cambridge, CB2 0QQ, UK.
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