Dynamic But Not Static Cerebral Autoregulation Is Impaired in Acute Ischaemic Stroke

Abstract

It remains unclear as to whether dynamic and static cerebral autoregulation (CA) are impaired in acute ischaemic stroke, and whether these changes are related to stroke subtype. This could have important implications with regard to post-stroke prognosis and the management of blood pressure (BP) in the acute post-ictal period. Using transcranial Doppler ultrasonography and non-invasive manipulation of BP, we compared both mechanisms in 61 patients with ischaemic stroke within 96 h of ictus, and 54 age- and sex-matched controls. There was no difference in static and dynamic CA indices between the various stroke subtypes. Combining all stroke subtypes dynamic autoregulation, as measured using thigh cuff release, was significantly impaired in both the affected and non-affected stroke hemispheres compared to controls (mean autoregulation index 4.1 ± 3.3, 4.8 ± 3.1 and 6.2 ± 2.3, respectively, p < 0.05). By comparison static autoregulation, assessed using isometric hand grip and thigh cuff inflation, was not significantly different. In conclusion, dynamic but not static CA appears to be globally impaired in acute ischaemic stroke. This deserves further study and may identify possibilities for therapeutic intervention.

Altered phase interactions between spontaneous blood pressure and flow fluctuations in type 2 diabetes mellitus: Nonlinear assessment of cerebral autoregulation

“…The time series BP and BFV were first linearly detrended and divided into 5000-point (100-sec) segments with 50% overlap. The Fourier transform of BP (S P (f)) and BFV (S V (f)) were calculated for each segment with a spectral resolution 0.01Hz, and were used to calculated the transfer function (5) where is the conjugate of S V (f); |S P (f)| 2 is the power spectrum density of BP; G(f) = |H (f)| is the transfer function amplitude (gain); and ø(f) is the transfer function phase at a specific frequency f. The amplitude and the phase of the transfer function reflect the linear amplitude and time relationship between the two signals. The reliability of these linear relationships can be evaluated by coherence that ranges from 0 to 1: (6) It has been proposed that a coherence value <0.5 indicates a nonlinear BP-BFV relationship and engagement of autoregulation [8,35].…”

“…It can be damaged by small-vessel ischemic cerebrovascular disease associated with diabetes mellitus, stroke [3][4][5] and brain injury [6,7]. Impaired cerebral autoregulation leads to dependence of blood flow on blood pressure, which may affect blood to brain when peripheral blood pressure is reduced under physiological and pathological conditions.…”

The Leicester cerebral haemodynamics database: normative values and the influence of age and sex

“…Due to the highly effective control exerted by the mechanism of pressure-autoregulation, CBF is normally maintained within narrow limits for mean blood pressures (MBP) in the range 60-150 mm Hg (Paulson, Strandgaard & Edvinsson 1990). Not surprisingly, it is the CBF autoregulation mechanism itself that has been shown to be impaired in a number of conditions such as ischaemic stroke, severe head injury, carotid artery disease, intracranial hypertension, diabetes and liver failure (Aries et al 2010, Czosnyka et al 1996, Dawson et al 2000, Hauerberg, Juhler 1994, Kim et al 2008, Lagi et al 2002, Panerai 2008, White, Markus 1997, van Beek et al 2008.…”

Optimising the assessment of cerebral autoregulation from black box models

“…However, given the complexity of the mechanisms controlling cerebral blood flow [21], one cannot be certain whether these parameters directly reflect autoregulation or some (related) physiological phenomenon. Furthermore it is possible that different clinical conditions (or CO 2 levels) have distinct effects [1] and that a single measure of CA may not be optimal for all applications [37]. Throughout this paper we have assumed (as does most of the cited literature) that the parameters used measure cerebral autoregulation, However, given the complexity of the physiology and the often poor correlation found between parameters that have all been considered to measure CA ( [38]), they may not all reflect identical phenomena of cerebrovascular control.…”

“…This regulatory mechanism is usually referred to as Cerebral Autoregulation (CA). Autoregulation is of great clinical interest as it can be impaired or lost in a number of conditions, such as stroke [1], subarachnoid haemorrhage [2] or head trauma [3].…”