Assessing dynamic cerebral autoregulation after stroke using a novel technique of combining transcranial Doppler ultrasonography and rhythmic handgrip

Kwan, Joseph; Lunt, M. J.; Jenkinson, Damian

doi:10.1097/00126097-200402000-00002

Cited by 35 publications

(45 citation statements)

References 31 publications

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“…One important finding, reported by Reinhard et al (2004), was that the phase returned to approximately normal values following carotid endarterectomy or stenting of the carotid artery. It is still not clear if other conditions, like stroke for example (Kwan et al 2004), can show similar recovery of dynamic CA. Nevertheless, the results of Reinhard et al (2004) demonstrate the potential of dynamic CA modelling for patient monitoring and followup.…”

Section: Studies Based On Arimentioning

confidence: 99%

Cerebral Autoregulation: From Models to Clinical Applications

2007

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Short-term regulation of cerebral blood flow (CBF) is controlled by myogenic, metabolic and neurogenic mechanisms, which maintain flow within narrow limits, despite large changes in arterial blood pressure (ABP). Static cerebral autoregulation (CA) represents the steady-state relationship between CBF and ABP, characterized by a plateau of nearly constant CBF for ABP changes in the interval 60-150 mmHg. The transient response of the CBF-ABP relationship is usually referred to as dynamic CA and can be observed during spontaneous fluctuations in ABP or from sudden changes in ABP induced by thigh cuff deflation, changes in posture and other manoeuvres. Modelling the dynamic ABP-CBFV relationship is an essential step to gain better insight into the physiology of CA and to obtain clinically relevant information from model parameters. This paper reviews the literature on the application of CA models to different clinical conditions. Although mathematical models have been proposed and should be pursued, most studies have adopted linear input-output ('black-box') models, despite the inherently non-linear nature of CA. The most common of these have been transfer function analysis (TFA) and a second-order differential equation model, which have been the main focus of the review. An index of CA (ARI), and frequency-domain parameters derived from TFA, have been shown to be sensitive to pathophysiological changes in patients with carotid artery disease, stroke, severe head injury, subarachnoid haemorrhage and other conditions. Non-linear dynamic models have also been proposed, but more work is required to establish their superiority and applicability in the clinical environment. Of particular importance is the development of multivariate models that can cope with time-varying parameters, and protocols to validate the reproducibility and ranges of normality of dynamic CA parameters extracted from these models.

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Section: Studies Based On Arimentioning

confidence: 99%

Cerebral Autoregulation: From Models to Clinical Applications

2007

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“…Six studies had follow-up measurements between 3 days and 3 months after stroke. In 9 studies, the initial stroke severity was not reported, [25][26][27][28][29][30][31][32][33] and 8 studies failed to provide information about other clinical conditions (such as arrhythmias, diabetes mellitus, and carotid pathology) associated with impaired cerebral autoregulation. 25,30,[32][33][34][35][36][37] All studies allowed hypertensive patients to be included.…”

Section: Literaturementioning

confidence: 99%

“…25,[27][28][29]40 Novak et al 39 only detected changes in the affected hemisphere of minor stroke patients, although the same group detected impaired dynamic autoregulation in both hemispheres during the Valsalva maneuver in 15 minor stroke patients using a nonlinear frequency shift method. 40 Gommer et al, 26 studying first-ever lacunar infarct, found TFA values and cerebrovascular reserve capacities in the normal range when examining their patients after Ն3 months.…”

Section: Chronic Phase Of Stroke and Steady-state And Dynamic Autoregmentioning

confidence: 99%

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Cerebral Autoregulation in Stroke

Aries

Elting

Keyser

et al. 2010

Stroke

301

148

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Background and Purpose-Cerebral autoregulation may become impaired after stroke. To provide a review of the nature and extent of any autoregulation impairment after stroke and its course over time, a technique allowing repeated bedside measurements with good temporal resolution is required. Transcranial Doppler (TCD) in combination with continuous blood pressure measurements allows noninvasive continuous bedside investigation with high temporal resolution of the dynamic and the steady-state components of cerebral autoregulation. Therefore, this review focuses on all TCD studies on cerebral autoregulation in the setting of documented ischemic stroke. Methods-PubMed and EMBASE were searched for studies of stroke, autoregulation, and TCD. Studies were either acute phase (Ͻ96 hours after index stroke) or chronic phase (Ͼ96 hours after index stroke) autoregulation studies. Quality of studies was studied in a standardized fashion. Results-Twenty-three studies met the inclusion criteria. General agreement existed on cerebral autoregulation being impaired, even after minor stroke. Bilateral impairment of autoregulation was documented, particularly after lacunar stroke. Studies showed progressive deterioration of cerebral autoregulation in the first 5 days after stroke and recovery over the next 3 months. Impaired cerebral autoregulation as assessed by TCD was related to neurological deterioration, the necessity for decompressive surgery, and poor outcome. Synthesis of the data of various studies was, however, limited by studies not meeting key methodological criteria for observational studies. Conclusions-TCD

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“…1,2 The advent of instrumentation that allows continuous noninvasive monitoring of cerebral blood flow (CBF) and ABP, with excellent temporal resolution, has caused a shift in our understanding of CA dynamics. 3 Instead of relying on vasoactive drugs to induce large stable changes in ABP, as required by the traditional 'static' approach, 1,4 the dynamic CA response can be identified using different maneuvers such as the sudden release of compressed thigh cuffs, 3 rhythmic hand grip, 5 Valsalva maneuver, 6 changes in posture, 7,8 and others that can induce transient alterations in ABP. Most of these maneuvers are difficult to implement in a clinical setting owing to the need for patient cooperation, parallel increases in sympathetic activity, or safety of protocols in vulnerable patients.…”

Section: Introductionmentioning

confidence: 99%

Detection of Impaired Cerebral Autoregulation Improves by Increasing Arterial Blood Pressure Variability

Katsogridakis

Bush

Fan

et al. 2012

J Cereb Blood Flow Metab

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Although the assessment of dynamic cerebral autoregulation (CA) based on measurements of spontaneous fluctuations in arterial blood pressure (ABP) and cerebral blood flow (CBF) is a convenient and much used method, there remains uncertainty about its reliability. We tested the effects of increasing ABP variability, provoked by a modification of the thigh cuff method, on the ability of the autoregulation index to discriminate between normal and impaired CA, using hypercapnia as a surrogate for dynamic CA impairment. In 30 healthy volunteers, ABP (Finapres) and CBF velocity (CBFV, transcranial Doppler) were recorded at rest and during 5% CO 2 breathing, with and without pseudo-random sequence inflation and deflation of bilateral thigh cuffs. The application of thigh cuffs increased ABP and CBFV variabilities and was not associated with a distortion of the CBFV step response estimates for both normocapnic and hypercapnic conditions (P ¼ 0.59 and P ¼ 0.96, respectively). Sensitivity and specificity of CA impairment detection were improved with the thigh cuff method, with the area under the receiver-operator curve increasing from 0.746 to 0.859 (P ¼ 0.031). We conclude that the new method is a safe, efficient, and appealing alternative to currently existing assessment methods for the investigation of the status of CA.

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Assessing dynamic cerebral autoregulation after stroke using a novel technique of combining transcranial Doppler ultrasonography and rhythmic handgrip

Abstract: Combining TCD with rhythmic handgrip appeared to be a useful technique for assessing dynamic CA and it deserves further studies. In this pilot study, there was some evidence that CA might improve up to 3 months after ischaemic stroke.

Cited by 35 publications

References 31 publications

Cerebral Autoregulation: From Models to Clinical Applications

Cerebral Autoregulation: From Models to Clinical Applications

Cerebral Autoregulation in Stroke

Detection of Impaired Cerebral Autoregulation Improves by Increasing Arterial Blood Pressure Variability

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