Assessment of dynamic cerebral autoregulation based on spontaneous fluctuations in arterial blood pressure and intracranial pressure

Panerai, Ronney B.; Hudson, Valera L; Fan, Lingke; Mahony, P.; Yeoman, P; Hope, Thomas A.; Evans, D.H.

doi:10.1088/0967-3334/23/1/306

Cited by 62 publications

(52 citation statements)

References 35 publications

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“…The classical CBFV step response for changes in ABP (Fig. 3) is in very good agreement with previous estimates (9, 11, 29 -31), including studies where ABP was recorded with intravascular catheters (27,32). One interesting consequence of expressing dynamic CA with the linearized model in Fig.…”

Section: Discussionsupporting

confidence: 88%

Multiple coherence of cerebral blood flow velocity in humans

Panerai¹,

Eames²,

Potter³

2006

American Journal of Physiology-Heart and Circulatory Physiology

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The coherence function has been used in transfer function analysis of dynamic cerebral autoregulation to assess the statistical significance of spectral estimates of gain and phase frequency response. Interpretation of the coherence function and choice of confidence limits has not taken into account the intrinsic nonlinearity represented by changes in cerebrovascular resistance due to vasomotor activity. For small spontaneous changes in arterial blood pressure (ABP), the relationship between ABP and cerebral blood flow velocity (CBFV) can be linearized, showing that corresponding changes in cerebrovascular resistance should be included as a second input variable. In this case, the standard univariate coherence function needs to be replaced by the multiple coherence, which takes into account the contribution of both inputs to explain CBFV variability. With the use of two different indicators of cerebrovascular resistance index [CVRI ϭ ABP/CBFV and the resistance-area product (RAP)], multiple coherences were calculated for 42 healthy control subjects, aged 20 to 40 yr (28 Ϯ 4.6 yr, mean Ϯ SD), at rest in the supine position. CBFV was measured in both middle cerebral arteries, and ABP was recorded noninvasively by finger photoplethysmography. Results for the ABP ϩ RAP inputs show that the multiple coherence of CBFV for frequencies Ͻ0.05 Hz is significantly higher than the corresponding values obtained for univariate coherence (P Ͻ 10 Ϫ5 ). Corresponding results for the ABP ϩ CVRI inputs confirm the principle of multiple coherence but are less useful due to the interdependence between CVRI, ABP, and CBFV. The main conclusion is that values of univariate coherence between ABP and CBFV should not be used to reject spectral estimates of gain and phase, derived from small fluctuations in ABP, because the true explained power of CBFV in healthy subjects is much higher than what has been usually predicted by the univariate coherence functions. cerebral autoregulation; coherence function; transfer function analysis; multivariate modeling; transcranial Doppler ultrasound TRANSFER FUNCTION ANALYSIS (TFA) is a useful technique to study physiological systems whose properties are characterized by linear or quasi-linear dynamic relationships between two or more physiological time series (6, 36). One area that has benefited from this approach is the study of dynamic cerebral blood flow (CBF) autoregulation in humans (27,28,40). Aaslid et al. (2) have extended the classical concept of "static" autoregulation (20) by showing that a sudden change in arterial blood pressure (ABP) leads to a relatively fast recovery of CBF to its original level. This transient response of the autoregulatory mechanisms is what is now termed "dynamic" cerebral autoregulation (CA) (2). TFA of dynamic CA was initially proposed by Giller (13), who modeled CA as an input-output relationship between beat-to-beat values of ABP and CBF, as estimated by transcranial Doppler ultrasound (TCD) recordings of CBF velocity (CBFV). The many contributions that followed...

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Section: Discussionsupporting

confidence: 88%

Multiple coherence of cerebral blood flow velocity in humans

Panerai¹,

Eames²,

Potter³

2006

American Journal of Physiology-Heart and Circulatory Physiology

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“…Thus, the question is whether the trauma induces phase shift changes, which interrupt the assumed linearity for coherence found in the controls. Other possible explanations for incongruent results include input power problems 18 ; an inhomogeneous population in which patients without CA disturbances are included with those with loss of CA and the number of investigations for statistical analysis is low; or a loss of linear stability of the system, a condition assumed to be observed by Panerai et al,23 who demonstrated that the system behaved completely differently in TBI patients with ICP Ͼ20 mm Hg compared with TBI patients with ICP Ͻ20 mm Hg. Finally, the impressive phase shift changes must be reconsidered when other mathematical models emerge.…”

Section: Discussionmentioning

confidence: 99%

Changes in Linear Dynamics of Cerebrovascular System After Severe Traumatic Brain Injury

Müller

Bianchi

Erülkü

et al. 2003

Stroke

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Background and Purpose-We sought to describe the dynamic changes in the cerebrovascular system after traumatic brain injury by transfer function estimation and coherence. Methods-In 42 healthy volunteers (meanϮSD age, 37Ϯ17 years; range, 17 to 65 years), spontaneous fluctuations of middle cerebral artery blood flow velocity and of finger blood pressure (BP) were simultaneously recorded over a period of 10 minutes under normocapnic and hypocapnic conditions to generate normative spectra of coherence, phase shift, and gain over the frequency range of 0 to 0.25 Hz. Similar recordings were performed in 24 patients with severe traumatic brain injury (Glasgow Coma Scale score Յ8; meanϮSD age, 50Ϯ20 years) serially on days 1, 3, 5, and 8 after trauma. Cranial perfusion pressure was kept at Ͼ70 mm Hg. Each blood flow velocity/BP recording was related to the presence or absence of middle cerebral artery territory brain parenchyma lesions on cranial CT performed within a close time frame. Results-In

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Section: March 2016mentioning

confidence: 99%

“…Undoubtedly, the pathophysiology of ICH may also involve mechanisms that directly hamper autoregulation, for example, increased intracranial pressure, 24 inflammation response, 25 and edema formation. 24,25 In a pilot study, an invasive assessment was applied to examine autoregulation and brain metabolism in the perihematomal zone of ICH, and a local disturbed autoregulation in edema was recorded. 26 Although the hematoma remained stable or was absorbed in the following days, the perihematomal edema always reaches its maximum between 10 and 20 days after ictus, 27 which may explain the more evident autoregulatory dysfunction on days 10 to 12 in our study.…”

Section: March 2016mentioning

confidence: 99%

Temporal Course of Dynamic Cerebral Autoregulation in Patients With Intracerebral Hemorrhage

Hanson

Guo

Jia³

et al. 2016

Stroke

110

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Reports of dCA in patients with ICH group are scarce, yet diverse. In a case-control study, a higher gain was observed within 3 days of ICH onset when compared with the healthy controls, indicating a less effective dCA during the acute stage. 7 In a recent study, researchers obtained serial measurements and stated that a higher bilateral gain could last 5 days Background and Purpose-Cerebral autoregulation is crucial in patients with intracerebral hemorrhage. Dynamic cerebral autoregulation is probably altered in acute intracerebral hemorrhage; however, the temporal course of dynamic cerebral autoregulation and its correlation with clinical factors and outcomes are poorly understood. Methods-Forty-three acute supratentorial intracerebral hemorrhage patients (53.7±10.0 years old, 30 men) were enrolled for serial measurements performed on days 1 to 2, 4 to 6, 10 to 12, and 30 days after ictus. Noninvasive continuous cerebral blood flow velocity and arterial blood pressure were recorded simultaneously using transcranial Doppler and a servocontrolled plethysmograph, respectively. Transfer function analysis was used to derive the autoregulatory parameters, including phase difference (PD), gain, and the rate of recovery of cerebral blood flow velocity. Results were compared with healthy controls and correlated with clinical factors and the 90-day outcome. Results-PD did not differ between affected and unaffected hemispheres over time. A significant lower PD (indicating dynamic cerebral autoregulation impaired) was found in bilateral hemispheres on days 1 to 2, 4 to 6, and 10 to 12, followed by later recovery on day 30. Lower bilateral PD on days 1 to 2 was associated with poorer Glasgow Coma Scale score at that time. Lower affected-side PD on days 4 to 6 was an independent predictive value for a poorer modified Rankin Scale at 90 days. Conclusions-In patients with supratentorial intracerebral hemorrhage, dynamic cerebral autoregulation is bilaterally impaired lasting at least 10 to 12 days and recovers within a month. Individual PD value is associated with clinical status at acute stage and affected-side PD on days 4 to 6 can be an independent predictor for clinical outcome. after ictus, whereas a higher gain value was not associated with any clinical factors or outcome. 14 Serial index Mx (reflecting both static and dynamic CA) was also derived within 5 days after ICH onset. Although it was not generally impaired on the first day, a secondary decline between days 3 and 5 could possibly occur mainly on the affected side, and this may be associated with poorer clinical status and outcomes.15 Yet, the above studies all garnered attention toward the early stage after ICH, while ignoring the subacute and recovery stages. This left unresolved whether, when, and to what extent could the altered dCA be restored.Thus, in the present study, we sought to (1) investigate the time course of dCA in ICH patients with serial follow-ups, including 1 to 2 days after ictus and 3 additional time points within a month, and (2) explore th...

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Assessment of dynamic cerebral autoregulation based on spontaneous fluctuations in arterial blood pressure and intracranial pressure

Cited by 62 publications

References 35 publications

Multiple coherence of cerebral blood flow velocity in humans

Multiple coherence of cerebral blood flow velocity in humans

Changes in Linear Dynamics of Cerebrovascular System After Severe Traumatic Brain Injury

Temporal Course of Dynamic Cerebral Autoregulation in Patients With Intracerebral Hemorrhage

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