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. 2023 Nov 17:3:102705.
doi: 10.1016/j.bas.2023.102705. eCollection 2023.

Cerebral hemodynamic monitoring combined with infusion test in hydrocephalus

Zofia Czosnyka  1 , Afroditi Lalou  1 , Adam I Pelah  1 , Alexis J Joanides  1 , Peter Smielewski  1 , Michal M Placek  1 , Czosnyka Marek  1
Affiliations

Cerebral hemodynamic monitoring combined with infusion test in hydrocephalus

Zofia Czosnyka et al. Brain Spine. .

Abstract

Introduction: Disturbance in cerebrospinal fluid (CSF) circulation may overlap with abnormality of cerebral blood flow (CBF) in hydrocephalus. Transcranial Doppler (TCD) ultrasonography is a non-invasive technique able to assess CBF velocity (CBFv) dynamics in response to a controlled rise in ICP during CSF infusion tests.

Research question: Which TCD-derived cerebral hemodynamic parameters change during controlled rise of ICP, and in which direction?

Material and methods: Infusion tests combined with TCD monitoring and non-invasive monitoring of arterial blood pressure (ABP) were conducted in 65 hydrocephalic patients. TCD-based hemodynamic variables: spectral pulsatility index (sPI), compliance of CSF space (Ci), cerebral autoregulation index (Mx), critical closing pressure (CrCP), cerebrovascular wall tension (WT) and diastolic closing margin (DCM-distance between diastolic ABP and CrCP) were calculated retrospectively.

Results: During the test ICP increased on average to 25 mm Hg (p < 0.0001), with a parallel decrease in cerebral perfusion pressure (CPP, p < 0.0003). The CBFv waveform changed, showing a rise in sPI (p < 0.0001). Ci decreased inversely proportional to a rise in ICP, and correlated well with changes of compliance calculated from the Marmarou model. CrCP increased in response to rising ICP (p < 0.001) while WT decreased (p < 0.002). DCM correlated with cerebrospinal elasticity (R = -0.31; p < 0.04). Cerebral autoregulation was worse in patients with normal CSF circulation, measured as resistance to CSF outflow (Rout): Pearson correlation between Mx and Rout was R = -0.41; p < 0.02.

Conclusion: A controlled rise in ICP affects cerebral hemodynamics in a moderate manner. Parameters like cerebral autoregulation index or DCM correlate with CSF dynamics and may be considered as supplementary variables for the diagnosis of hydrocephalus.

Keywords: Brain compliance; Cerebral autoregulation; Critical closing pressure; Pulsatility index; Transcranial Doppler.

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Conflict of interest statement

PS and MC has a financial interest in part of the licensing fee of ICM + software used for signal recording and analysis. The other authors have nothing to disclose.

Figures

Fig. 1
Fig. 1
Example of recording of original signals during infusion test: Blood pressure (ABP, units mmHg), intracranial pressure (ICP, units mmHg) and blood flow velocity in left middle cerebral artery (FVL, units cm/s). X-axis- time in hours:min. Infusion of mock CSF with a rate 1.5 ml/min started at 15:34 and finished just after 15:52 after ICP reached plateau at around 31 mm Hg. Gaps in recording are periods of artifacts in TCD signal, excluded from analysis.
Fig. 2
Fig. 2
Example of pulse waveform of ABP [mm Hg], ICP[mm Hg], FV [cm/s] and cerebral blood volume (CBV – units are volume per cross-sectional area of an insonated vessel [cm]). CBV is pulsatile, therefore its amplitude (first harmonic) can be calculated using spectral analysis along with amplitude of arterial blood pressure.
Fig. 3
Fig. 3
Example of recorded variables (ICP, blood flow velocity [cm/s]), critical closing pressure (CrCP [mm Hg]), arterial wall tension (WT[mmHg]). Spectral pulsatility index (SPI) and compliance of cerebrospinal space (Ci [cm/mmHg]) during infusion test.
Fig. 4
Fig. 4
Example of slow vasogenic waves of ICP [mm Hg] and TCD blood flow velocity in the left MCA (FVL-[cm/s]). There is a clear synchronization between slow waves in ICP and blood flow velocity.
Fig. 5
Fig. 5
Significant relationship between resistance to CSF outflow (Rout) and autoregulation index Mx.
See this image and copyright information in PMC

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