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Dynamic cerebral autoregulation is transiently impaired for one week after large-vessel acute ischemic stroke.

ABSTRACT: Dynamic cerebral autoregulation (DCA) is the continuous counterregulation of cerebral blood flow to fluctuations in blood pressure. DCA can become impaired after acute stroke, but it remains unclear to what extent and over what interval this occurs.We included 28 patients (NIHSS = 12 ± 6.5, age = 68.4 ± 17.1, 16F) with acute large-vessel ischemic stroke in the middle cerebral artery territory and 29 healthy controls (mean age 54.9 ± 9, 16F). DCA was assessed by simultaneous measurement of blood pressure together with blood flow velocities using finger plethysmography/arterial catheter and transcranial Doppler over three 10-minute recordings on days 0-2, 3-6 and ?7 days after stroke. Transfer function analysis was applied to calculate average phase shift (PS) in the low frequency range (0.06-0.12 Hz). Less PS indicated poorer autoregulation. The affected side was compared with the unaffected side and controls. Univariate comparisons of data were performed using t tests at single time points, and generalized estimating equations with an exchangeable correlation matrix to examine the change in PS over time.At mean 1.3 ± 0.5 days after stroke the average PS in the affected hemisphere was 29.6 ± 10.5 vs. 42.5 ± 13 degrees in the unaffected hemisphere (p = 0.004). At 4.1 ± 1 days, the PS in affected and unaffected hemisphere was 23.2 ± 19.1 vs. 41.7 ± 18.5 degrees, respectively (p = 0.003). At mean 9.75 ± 2.2 days stroke there was no difference between the affected and the unaffected hemisphere (53.2 ± 28.2 vs. 50.7 ± 29.2 degrees, p = 0.69). Control subjects had an average PS = 47.9 ± 16.8, significantly different from patients' affected hemisphere at the first two measurements (p = 0.001), but not the third (p = 0.37). The PS in controls remained unchanged on repeat testing after an average 19.1 days (48.4 ± 17.1, p = 0.61). Using the last recording as the reference, the average PS in the affected hemisphere was -23.54 (-44.1, -3) degrees lower on recording one (p = 0.025), and -31.6 (-56.1, -7.1) degrees lower on recording two (p < 0.011). Changes in the unaffected hemisphere over time were nonsignificant.These data suggest that dynamic cerebral autoregulation is impaired in the affected hemisphere throughout the first week after large-vessel ischemic stroke, and then normalizes by week two. These findings may have important implications for acute blood pressure management after stroke.

SUBMITTER: Petersen NH

PROVIDER: S-EPMC4754197 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Dynamic cerebral autoregulation is transiently impaired for one week after large-vessel acute ischemic stroke.

Petersen Nils H NH Ortega-Gutierrez Santiago S Reccius Andrés A Masurkar Arjun A Huang Amy A Marshall Randolph S RS

Cerebrovascular diseases (Basel, Switzerland) 20150203 2

<h4>Background</h4>Dynamic cerebral autoregulation (DCA) is the continuous counterregulation of cerebral blood flow to fluctuations in blood pressure. DCA can become impaired after acute stroke, but it remains unclear to what extent and over what interval this occurs.<h4>Methods</h4>We included 28 patients (NIHSS = 12 ± 6.5, age = 68.4 ± 17.1, 16F) with acute large-vessel ischemic stroke in the middle cerebral artery territory and 29 healthy controls (mean age 54.9 ± 9, 16F). DCA was assessed by ...[more]

PMID: 25661277

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Project description:Breath-hold divers (BHD) experience repeated bouts of severe hypoxia and hypercapnia with large increases in blood pressure. However, the impact of long-term breath-hold diving on cerebrovascular control remains poorly understood. The ability of cerebral blood vessels to respond rapidly to changes in blood pressure represents the property of dynamic autoregulation. The current investigation tested the hypothesis that breath-hold diving impairs dynamic autoregulation to a transient hypotensive stimulus. Seventeen BHD (3 women, 11?±?9 yr of diving) and 15 healthy controls (2 women) completed two or three repeated sit-to-stand trials during spontaneous breathing and poikilocapnic conditions. Heart rate (HR), finger arterial blood pressure (BP), and cerebral blood flow velocity (BFV) from the right middle cerebral artery were measured continuously with three-lead electrocardiography, finger photoplethysmography, and transcranial Doppler ultrasonography, respectively. End-tidal carbon dioxide partial pressure was measured with a gas analyzer. Offline, an index of cerebrovascular resistance (CVRi) was calculated as the quotient of mean BP and BFV. The rate of the drop in CVRi relative to the change in BP provided the rate of regulation [RoR; (?CVRi/?T)/?BP]. The BHD demonstrated slower RoR than controls (P ? 0.001, d?=?1.4). Underlying the reduced RoR in BHD was a longer time to reach nadir CVRi compared with controls (P = 0.004, d?=?1.1). In concert with the longer CVRi response, the time to reach peak BFV following standing was longer in BHD than controls (P = 0.01, d?=?0.9). The data suggest impaired dynamic autoregulatory mechanisms to hypotension in BHD. NEW & NOTEWORTHY Impairments in dynamic cerebral autoregulation to hypotension are associated with breath-hold diving. Although weakened autoregulation was observed acutely in this group during apneic stress, we are the first to report on chronic adaptations in cerebral autoregulation. Impaired vasomotor responses underlie the reduced rate of regulation, wherein breath-hold divers demonstrate a prolonged dilatory response to transient hypotension. The slower cerebral vasodilation produces a longer perturbation in cerebral blood flow velocity, increasing the risk of cerebral ischemia.

Project description:BackgroundImpaired cerebral blood flow (CBF) autoregulation during cardiopulmonary bypass (CPB) is associated with stroke and other adverse outcomes. Large and small arterial stenosis is prevalent in patients undergoing cardiac surgery. We hypothesize that large and/or small vessel cerebral arterial disease is associated with impaired cerebral autoregulation during CPB.MethodsA retrospective cohort analysis of data from 346 patients undergoing cardiac surgery with CPB enrolled in an ongoing prospectively randomized clinical trial of autoregulation monitoring were evaluated. The study protocol included preoperative transcranial Doppler (TCD) evaluation of major cerebral artery flow velocity by a trained vascular technician and brain magnetic resonance imaging (MRI) between postoperative days 3 and 5. Brain MRI images were evaluated for chronic white matter hyperintensities (WMHI) by a vascular neurologist blinded to autoregulation data. "Large vessel" cerebral vascular disease was defined by the presence of characteristic TCD changes associated with stenosis of the major cerebral arteries. "Small vessel" cerebral vascular disease was defined based on accepted scoring methods of WMHI. All patients had continuous TCD-based autoregulation monitoring during surgery.ResultsImpaired autoregulation occurred in 32.4% (112/346) of patients. Preoperative TCD demonstrated moderate-severe large vessel stenosis in 67 (25.2%) of 266 patients with complete data. In adjusted analysis, female sex (odds ratio [OR], 0.46; 95% confidence interval [CI], 0.25-0.86; P = .014) and higher average temperature during CPB (OR, 1.23; 95% CI, 1.02-1.475; P = .029), but not moderate-severe large cerebral arterial stenosis (P = .406), were associated with impaired autoregulation during CPB. Of the 119 patients with available brain MRI data, 42 (35.3%) demonstrated WMHI. The presence of small vessel cerebral vascular disease was associated with impaired CBF autoregulation (OR, 3.25; 95% CI, 1.21-8.71; P = .019) after adjustment for age, history of peripheral vascular disease, preoperative hemoglobin level, and preoperative treatment with calcium channel blocking drugs.ConclusionsThese data confirm that impaired CBF autoregulation is prevalent during CPB predisposing affected patients to brain hypoperfusion or hyperperfusion with low or high blood pressure, respectively. Small vessel, but not large vessel, cerebral vascular disease, male sex, and higher average body temperature during CPB appear to be associated with impaired autoregulation.

Project description:RationaleDisturbances in dynamic cerebral autoregulation after ischemic stroke may have important implications for prognosis. Recent meta-analyses have been hampered by heterogeneity and small samples.Aim and/or hypothesisThe aim of study is to undertake an individual patient data meta-analysis (IPD-MA) of dynamic cerebral autoregulation changes post-ischemic stroke and to determine a predictive model for outcome in ischemic stroke using information combined from dynamic cerebral autoregulation, clinical history, and neuroimaging.Sample size estimatesTo detect a change of 2% between categories in modified Rankin scale requires a sample size of ∼1500 patients with moderate to severe stroke, and a change of 1 in autoregulation index requires a sample size of 45 healthy individuals (powered at 80%, α = 0.05). Pooled estimates of mean and standard deviation derived from this study will be used to inform sample size calculations for adequately powered future dynamic cerebral autoregulation studies in ischemic stroke.Methods and designThis is an IPD-MA as part of an international, multi-center collaboration (INFOMATAS) with three phases. Firstly, univariate analyses will be constructed for primary (modified Rankin scale) and secondary outcomes, with key co-variates and dynamic cerebral autoregulation parameters. Participants clustering from within studies will be accounted for with random effects. Secondly, dynamic cerebral autoregulation variables will be validated for diagnostic and prognostic accuracy in ischemic stroke using summary receiver operating characteristic curve analysis. Finally, the prognostic accuracy will be determined for four different models combining clinical history, neuroimaging, and dynamic cerebral autoregulation parameters.Study outcome(s)The outcomes for this study are to determine the relationship between clinical outcome, dynamic cerebral autoregulation changes, and baseline patient demographics, to determine the diagnostic and prognostic accuracy of dynamic cerebral autoregulation parameters, and to develop a prognostic model using dynamic cerebral autoregulation in ischemic stroke.DiscussionThis is the first international collaboration to use IPD-MA to determine prognostic models of dynamic cerebral autoregulation for patients with ischemic stroke.

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Dynamic cerebral autoregulation is transiently impaired for one week after large-vessel acute ischemic stroke.

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Dynamic cerebral autoregulation is transiently impaired for one week after large-vessel acute ischemic stroke.

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