Neurocritical Care

, Volume 17, Issue 1, pp 58–66 | Cite as

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

  • Nicolás de Riva
  • Karol P. Budohoski
  • Peter Smielewski
  • Magdalena Kasprowicz
  • Christian Zweifel
  • Luzius A. Steiner
  • Matthias Reinhard
  • Neus Fábregas
  • John D. Pickard
  • Marek Czosnyka
Original Articles

Abstract

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.

Keywords

Cerebral hemodynamics Plateau waves Transcranial doppler Traumatic brain injury 

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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • Nicolás de Riva
    • 1
    • 2
  • Karol P. Budohoski
    • 1
  • Peter Smielewski
    • 1
  • Magdalena Kasprowicz
    • 1
    • 3
  • Christian Zweifel
    • 1
    • 4
  • Luzius A. Steiner
    • 1
    • 5
  • Matthias Reinhard
    • 1
    • 6
  • Neus Fábregas
    • 2
  • John D. Pickard
    • 1
  • Marek Czosnyka
    • 1
    • 7
  1. 1.Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke’s HospitalUniversity of CambridgeCambridgeUK
  2. 2.Department of Anesthesiology, Hospital ClinicUniversitat de BarcelonaBarcelonaSpain
  3. 3.Institute of Biomedical Engineering and InstrumentationWroclaw University of TechnologyWroclawPoland
  4. 4.Department of NeurosurgeryUniversity Hospital of BaselBaselSwitzerland
  5. 5.Department of AnaesthesiaLausanne University HospitalLausanneSwitzerland
  6. 6.Department of NeurologyUniversity of FreiburgFreiburgGermany
  7. 7.Institute of Electronic SystemsWarsaw University of TechnologyWarsawPoland

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