Transcranial Doppler Pulsatility Index: What it is and What it Isn’t

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 i...

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Bibliographic Details
Published in:Neurocritical care 2012-08, Vol.17 (1), p.58-66
Main Authors: de Riva, Nicolás, Budohoski, Karol P., Smielewski, Peter, Kasprowicz, Magdalena, Zweifel, Christian, Steiner, Luzius A., Reinhard, Matthias, Fábregas, Neus, Pickard, John D., Czosnyka, Marek
Format: Article
Language:English
Subjects:
Adolescent
Adult
Aged
Blood pressure
Brain Injuries - diagnostic imaging
Brain Injuries - physiopathology
Carbon dioxide
Cerebral blood flow
Cerebrovascular Circulation - physiology
Cohort Studies
Compliance
Critical Care Medicine
Databases, Factual
Female
Flow velocity
Fourier transforms
Heart rate
Hemodynamics
Humans
Hyperventilation
Hypocapnia - diagnostic imaging
Hypocapnia - physiopathology
Intensive
Internal Medicine
Intracranial pressure
Intracranial Pressure - physiology
Investigations
Male
Mathematical models
Medicine
Medicine & Public Health
Middle Aged
Models, Cardiovascular
Neurology
Original Articles
Perfusion
Physiology
Pulsatile Flow - physiology
Software
Traumatic brain injury
Ultrasonography, Doppler, Transcranial - methods
Ultrasound
Vascular Resistance - physiology
Veins & arteries
Waves
Young Adult
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Summary: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  
ISSN:1541-6933
1556-0961
DOI:10.1007/s12028-012-9672-6