Serial changes in static and dynamic cerebral autoregulation after acute ischaemic stroke

BACKGROUND: The longitudinal changes in static and dynamic cerebral autoregulation (CA) following acute ischaemic stroke are unknown and were assessed in this study. METHODS: Fifty-four ischaemic stroke patients were studied within 96 h of ischaemic stroke and again 7-14 days later, using transcranial Doppler techniques to measure CA. Results were compared to an age-, sex- and blood pressure (BP)-matched control group. Static BP pressor stimulus was produced by thigh cuff inflation and dynamic stimulus by rapid thigh cuff release. RESULTS: Dynamic, but not static, CA was globally impaired at initial (mean dynamic CA index 3.9 +/- 3.1 vs. 6.2 +/- 2.3, p < 0.005) and follow-up studies (dynamic CA 3.9 +/- 2.8 vs. 6.2 +/- 2.3, p < 0.01) in stroke patients compared to controls. Static CA was similar in stroke patients and controls and was unchanged during follow-up. CONCLUSIONS: Dynamic, but not static, CA is impaired after acute ischaemic stroke and remains abnormal for at least 1-2 weeks post ictus. These changes are present in both the affected and non-affected hemispheres and are unrelated to previous antihypertensive treatment, baseline BP levels or BP changes after stroke, age or stroke type.     

Dynamic but not static cerebral autoregulation is impaired in acute ischaemic stroke

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.     

Impaired dynamic cerebral autoregulation in middle cerebral artery stenosis

BACKGROUND AND PURPOSE: Analysis of dynamic cerebral autoregulation during transient falls in blood pressure is considered a sensitive and convenient method for evaluating patients with carotid artery stenosis. To this point, there have been few reports on the efficacy of using the thigh cuffs technique to analyse middle cerebral artery (MCA) stenosis. If it could be determined whether cerebral blood flow can be maintained (autoregulated) during sudden falls in arterial blood pressure (ABP), then it might be possible to identify patients with MCA stenosis who are at risk of stroke. METHODS: We used the thigh cuff technique to estimate dynamic cerebral autoregulation in 57 patients with MCA stenosis and 72 normal controls. After a stepwise fall in arterial blood pressure, we determined the rate of the rise of MCA blood velocity and compared it with the rate of the rise of arterial blood pressure. In this manner, the dynamic cerebral autoregulation of 11 patients undergoing MCA M1 stent angioplasty was estimated both pre- and post-operation. RESULTS: The autoregulatory index (ARI) was significantly reduced in patients with stenosed/occluded MCA (3.24 +/- 1.52), as compared with normal controls (5.25 +/- 1.39; p<0.001) (results reported as mean +/- SD). Poor ARI values are usually observed in patients with a higher degree of stenosis and particularly in patients with insufficient collateral compensation. ARI was significantly reduced in severe stroke patients (modified ranking scale>or=1), as compared with asymptomatic or TIA patients (p<0.05). After MCA stent angioplasty was performed, there was a significant improvement in ARI in 11 subjects, which caused a mean increase in ARI from 2.08 +/- 1.10 to 3.80 +/- 1.36 (p=0.008). CONCLUSIONS: Dynamic cerebral autoregulation is impaired in patients with middle cerebral artery stenosis. Assessing dynamic cerebral autoregulation may allow a subgroup of patients with MCA stenosis who are at risk of hemodynamic stroke to be identified. Dynamic cerebral disautoregulation in patients with severe MCA stenosis is mostly remedied by stent angioplasty.     

Bendrofluazide fails to reduce elevated blood pressure levels in the immediate post-stroke period

INTRODUCTION: Blood pressure (BP) levels, beat-to-beat blood pressure variability, dynamic cerebral autoregulation and cardiac baroreceptor sensitivity are frequently abnormal following acute stroke and are associated with an adverse short- and long-term prognosis. Thiazide diuretics are effective antihypertensive agents in preventing primary and secondary stroke, but their hypotensive and cerebral autoregulatory effects in the immediate post-stroke period have not been studied. METHODS: Thirty-seven hypertensive neuroradiologically proven ischaemic stroke patients were randomized in a double-blind, placebo controlled, parallel group study to bendrofluazide 2.5 mg daily or matching placebo, within 96 h of stroke onset, for a 7-day period. Casual and non-invasive beat-to-beat arterial BP levels, cerebral blood flow velocity, ECG and transcutaneous carbon dioxide levels were measured within 70 +/- 20 h of cerebral infarction and again 7 days later. Dynamic cerebral autoregulatory indices, pulse interval, BP variability and cardiac baroreceptor sensitivity were also calculated. RESULTS: Small, non-significant falls were seen in casual and beat-to-beat BP levels over the 7-day period in both active and placebo-treated patients with no differences between treatments. No significant changes were seen in dynamic cerebral autoregulation or in cardiac baroreceptor sensitivity during the follow-up in either group. CONCLUSION: Following acute ischaemic stroke, the standard dose of bendrofluazide at 2.5 mg daily in this study sample did not lower systemic BP levels over the subsequent 7-day period. There was no evidence that bendrofluazide significantly altered cerebral autoregulation or improved cardiac baroreceptor sensitivity post-ictus. Bendrofluazide appears to be an ineffective hypotensive agent at the standard dosage in the initial post-stroke period.     

Impaired dynamic cerebral autoregulation in middle cerebral artery stenosis

Abstract

Background and purpose: Analysis of dynamic cerebral autoregulation during transient falls in blood pressure is considered a sensitive and convenient method for evaluating patients with carotid artery stenosis. To this point, there have been few reports on the efficacy of using the thigh cuffs technique to analyse middle cerebral artery (MCA) stenosis. If it could be determined whether cerebral blood flow can be maintained (autoregulated) during sudden falls in arterial blood pressure (ABP), then it might be possible to identify patients with MCA stenosis who are at risk of stroke.

Methods: We used the thigh cuff technique to estimate dynamic cerebral autoregulation in 57 patients with MCA stenosis and 72 normal controls. After a stepwise fall in arterial blood pressure, we determined the rate of the rise of MCA blood velocity and compared it with the rate of the rise of arterial blood pressure. In this manner, the dynamic cerbral autoregulation of 11 patients undergoing MCA M1 stent angioplasty was estimated both pre- and post-operation.

Results: The autoregulatory index (ARI) was significantly reduced in patients with stenosed/occluded MCA (3.24 ± 1.52), as compared with normal controls (5.25 ± 1.39; p<0.001) (results reported as mean ± SD). Poor ARI values are usually observed in patients with a higher degree of stenosis and particularly in patients with insufficient collateral compensation. ARI was significantly reduced in severe stroke patients (modified ranking scale≥1), as compared with asymptomatic or TIA patients (p<0.05). After MCA stent angioplasty was performed, there was a significant improvement in ARI in 11 subjects, which caused a mean increase in ARI from 2.08 ± 1.10 to 3.80 ± 1.36 (p=0.008).

Conclusions: Dynamic cerebral autoregulation is impaired in patients with middle cerebral artery stenosis. Assessing dynamic cerebral autoregulation may allow a subgroup of patients with MCA stenosis who are at risk of hemodynamic stroke to be identified. Dynamic cerebral disautoregulation in patients with severe MCA stenosis is mostly remedied by stent angioplasty.     

Blood pressure management in acute stroke: a long-standing debate

Although elevated blood pressure (BP) levels are a common complication of acute stroke, whether of ischaemic or haemorrhagic type, a long-standing debate exists regarding the management of post-stroke hypertension. In the absence of solid, randomised data from controlled trials, the current observational evidence allows different approaches, since theoretical arguments exist for both lowering BP in the setting of acute stroke (reduce the risk of stroke recurrence, of subsequent oedema formation, of rebleeding and haematoma expansion in patients with cerebral bleeding) as well as leaving raised BP levels untreated (avoid reduction in cerebral perfusion pressure and blood flow to viable ischaemic tissue in the absence of normal autoregulation). The present review will summarize the evidence for and against the therapeutic manipulation of BP in acute stroke provided by the currently available observational studies and randomised trials, consider the ongoing clinical trials in this area and address the present recommendations regarding this conflicting issue.     

Dynamic cerebral autoregulation: A marker of post-operative delirium?

ObjectiveWe investigated the potential association of cerebral autoregulation (CA) with postoperative delirium (PD), a common complication of cardiac surgery with cardiopulmonary bypass (CPB).MethodsIn patients undergoing coronary artery bypass graft (CABG) surgery with CPB, cerebral blood flow velocity (CBFV) and blood pressure (BP) were continuously recorded during 5-min preoperatively (T1), after 24 h (T2), and 7 days after procedure (T3). Prospective multivariate logistic regression analysis was performed to determine the independent risk factors of PD. Autoregulation index (ARI) was calculated from the CBFV response to a step change in BP derived by transfer function analysis.ResultsIn 67 patients, mean age 64.3 ± 9.5 years, CA was depressed at T2 as shown by values of ARI (3.9 ± 1.7), compared to T1 (5.6 ± 1.7) and T3 (5.5 ± 1.8) (p < 0.001). Impaired CA was found in 37 (55%) patients at T2 and in 7 patients (20%) at T3. Lower ARI at T1 and T2 were predictors of PD (p = 0.003).ConclusionDynamic CA was impaired after CABG surgery with CPB and was a significant independent risk factor of PD.SignificanceAssessment of CA before and after surgery could have considerable potential for early identification of patients at risk of PD, thus reducing poor outcomes and length of stay.Clinical trials registration: www.clinicaltrials.gov (NCT02143544, April 30, 2014).     

Dynamic cerebral autoregulation in subjects with Alzheimer's disease, mild cognitive impairment, and controls: evidence for increased peripheral vascular resistance with possible predictive value

Cerebrovascular dysfunction plays a role not only in vascular causes of cognitive impairment but also in Alzheimer's disease (AD). We hypothesized that cerebral autoregulation is impaired in patients with AD compared to subjects with mild cognitive impairment (MCI) and controls. Dynamic cerebral autoregulation (dCA) was investigated in 17 AD patients, 19 MCI subjects, and 20 controls (C). Groups were matched for age, gender, and level of education. Electrocardiogram and non-invasive finger arterial blood pressure were measured and transcranial doppler ultrasonography was used to measure cerebral blood flow velocity in right and left middle cerebral artery (MCA). Cerebrovascular resistance index (CVRi) was also computed. dCA in supine position was quantified based on spontaneous blood pressure variations by computation of the linear transfer function between arterial blood pressure and MCA cerebral blood flow velocity. dCA gain and phase were evaluated for different frequency bands. Results were also evaluated using a 3-parameter windkessel model (WKM). CVRi was significantly higher in AD (2.9 ± 0.2) compared to both MCI (2.3 ± 0.1, p = 0.02) and C (2.1 ± 0.1 mmHgs/cm, p = 0.002). Five MCI patients who converted to AD during the course of the study also had higher CVRi compared to non-converters (2.8 ± 0.6 versus 2.1 ± 0.5 mmHgs/cm, p < 0.05). No significant differences in dCA gain and phase were found. In terms of the WKM approach, in the order C→MCI→AD groups showed about equal arterial resistance and peripheral compliance, but increased peripheral vasculature resistance (26 ± 2 versus 36 ± 3 mmHgs/ml in C resp. AD, p = 0.004). In conclusion, AD patients compared to MCI patients and controls have increased CVRi, whereas dCA parameters do not seem to differentiate AD patients. For MCI patients, CVRi might have predictive value in developing AD.     

Cerebral autoregulation and ageing.

Little is known about the effects of ageing on cerebral autoregulation (CA). To examine the relationship between age and CA in adults, we conducted a prospective study using a non-invasive protocol without external stimuli. We studied 32 subjects, aged 23-68 years. They were assigned to a young group (28+/-5 years) and an old group (54+/-8 years). The groups were sex-matched. Transcranial Doppler ultrasonography (TCD) was used to record bilateral middle cerebral artery flow velocities (CBFV, cm/sec). Noninvasive beat-to-beat tonometric arterial blood pressure (ABP) measurement of the radial artery was used to record spontaneous blood pressure fluctuations. The Mx, an index of dynamic cerebral autoregulation (dCA), was calculated from a moving correlation between ABP and CBFV. We did not find a correlation between age and Mx. No statistically significant difference in the Mx between the groups (0.27+/-0.23, young, vs. 0.37+/-0.24, old) was demonstrated. Age does not affect dynamic cerebral autoregulation assessed by the Mx index in healthy adult subjects. This study supports findings from previous papers wherein CA was measured with protocols which require external stimuli. Further studies are needed to determine CA in subjects above 70 years of age.     

Cerebral critical closing pressure and resistance-area product: the influence of dynamic cerebral autoregulation,age and sex

Instantaneous arterial pressure-flow (or velocity) relationships indicate the existence of a cerebral critical closing pressure (CrCP), with the slope of the relationship expressed by the resistance-area product (RAP). In 194 healthy subjects (20–82 years, 90 female), cerebral blood flow velocity (CBFV, transcranial Doppler), arterial blood pressure (BP, Finapres) and end-tidal CO₂ (EtCO₂, capnography) were measured continuously for five minutes during spontaneous fluctuations of BP at rest. The dynamic cerebral autoregulation (CA) index (ARI) was extracted with transfer function analysis from the CBFV step response to the BP input and step responses were also obtained for the BP-CrCP and BP-RAP relationships. ARI was shown to decrease with age at a rate of −0.025 units/year in men (p = 0.022), but not in women (p = 0.40). The temporal patterns of the BP-CBFV, BP-CrCP and BP-RAP step responses were strongly influenced by the ARI (p < 0.0001), but not by sex. Age was also a significant determinant of the peak of the CBFV step response and the tail of the RAP response. Whilst the RAP step response pattern is consistent with a myogenic mechanism controlling dynamic CA, further work is needed to explore the potential association of the CrCP step response with the flow-mediated component of autoregulation.     

Changes in cerebral autoregulation,stroke-related blood biomarkers,and autonomic regulation after patent foramen ovale closure in severe migraine patients

Aims

This study aimed to investigate changes in dynamic cerebral autoregulation (dCA), 20 stroke-related blood biomarkers, and autonomic regulation after patent foramen ovale (PFO) closure in severe migraine patients.

Methods

Patent foramen ovale severe migraine patients, matched non-PFO severe migraine patients, and healthy controls were included. dCA and autonomic regulation were evaluated in each participant at baseline, and within 48-h and 30 days after closure in PFO migraineurs. A panel of stroke-related blood biomarkers was detected pre-surgically in arterial-and venous blood, and post-surgically in the arterial blood in PFO migraineurs.

Results

Forty-five PFO severe migraine patients, 50 non-PFO severe migraine patients, and 50 controls were enrolled. The baseline dCA function of PFO migraineurs was significantly lower than that of non-PFO migraineurs and controls but was rapidly improved with PFO closure, remaining stable at 1-month follow-up. Arterial blood platelet-derived growth factor-BB (PDGF-BB) levels were higher in PFO migraineurs than in controls, which was immediately and significantly reduced after closure. No differences in autonomic regulation were observed among the three groups.

Conclusion

Patent foramen ovale closure can improve dCA and alter elevated arterial PDGF-BB levels in migraine patients with PFO, both of which may be related to the preventive effect of PFO closure on stroke occurrence/recurrence.     

Integrative physiological assessment of cerebral hemodynamics and metabolism in acute ischemic stroke

Restoring perfusion to ischemic tissue is the primary goal of acute ischemic stroke care, yet only a small portion of patients receive reperfusion treatment. Since blood pressure (BP) is an important determinant of cerebral perfusion, effective BP management could facilitate reperfusion. But how BP should be managed in very early phase of ischemic stroke remains a contentious issue, due to the lack of clear evidence. Given the complex relationship between BP and cerebral blood flow (CBF)—termed cerebral autoregulation (CA)—bedside monitoring of cerebral perfusion and oxygenation could help guide BP management, thereby improve stroke patient outcome. The aim of INFOMATAS is to ‘identify novel therapeutic targets for treatment and management in acute ischemic stroke’. In this review, we identify novel physiological parameters which could be used to guide BP management in acute stroke, and explore methodologies for monitoring them at the bedside. We outline the challenges in translating these potential prognostic markers into clinical use.     

The Effect of Valsartan versus Non-RAAS Treatment on Autoregulation of Cerebral Blood Flow

Background: Cerebral autoregulation (CA) is a protective mechanism which maintains the steadiness of the cerebral blood flow (CBF) through a broad range of systemic blood pressure (BP). Acute hypertension has been shown to reduce the cerebrovascular adaptation to BP variations. However, it is still unknown whether CA is impaired in chronic hypertension. This study evaluated whether a strict control of BP affects the CA in patients with chronic hypertension, and compared a valsartan-based regimen to a regimen not inhibiting the renin-angiotensin-aldosterone system (non-RAAS). Methods: Eighty untreated patients with isolated systolic hypertension were randomized to valsartan 320 mg or to a non-RAAS regimen during 6 months. The medication was upgraded to obtain BP <140/90 mm Hg. Continuous recordings of arterial BP and CBF velocity (transcranial Doppler) were performed during periods of 5 minutes, at rest, and at different levels of alveolar CO(2) pressure provided by respiratory maneuvers. The dominant frequency of CBF oscillations was determined for each patient. Dynamic CA was measured as the mean phase shift between BP and CBF by cross-spectral analysis in the medium frequency and in the dominant CBF frequency. Results: Mean ambulatory 24-hour BP fell from 144/87 to 127/79 mm Hg in the valsartan group and from 144/87 to 134/81 mm Hg in the non-RAAS group (p = 0.13). Both groups had a similar reduction in the central BP and in the carotido-femoral pulse wave velocity. The average phase shift between BP fluctuations and CBF response at rest was normal at randomization (1.82 ± 0.08 s), which is considered a preserved autoregulation and increased to 1.91 ± 0.12 s at the end of study (p = 0.45). The comparison of both treatments showed no significant difference (-0.01 ± 0.17 s vs. 0.16 ± 0.16 s, p = 0.45) for valsartan versus non-RAAS groups. The plasmatic level of glycosylated hemoglobin decreased in the valsartan arm compared to the non-RAAS arm (-0.23 ± 0.06 vs. -0.08 ± 0.07%, p = 0.07). Conclusions: In elderly hypertensive men with isolated chronic systolic hypertension, CA seems efficient at baseline and is not significantly affected by 6 months of BP-lowering treatment. This suggests that the preventive effects of BP medication against stroke are not mediated through a restoration of the CA.     

Dynamic cerebral autoregulation is compromised in ischaemic stroke of undetermined aetiology only in the non-affected hemisphere

Background and purposeTo assess dynamic cerebral autoregulation (CA) in patients with acute ischaemic stroke of undetermined aetiology, within 72 h of stroke onset.Materials and methodsIn 6 patients with ischaemic stroke of undetermined aetiology (aged 66 ± 9 years, National Institutes of Health Stroke Scale [NIHSS] score on admission: 4.0, range: 4–11), selected based on screening of 118 consecutive ischaemic stroke patients and in 14 volunteers (aged 62 ± 10 years), we continuously monitored RR intervals (RRI), mean arterial pressure (MAP) by means of photoplethysmography, mean cerebral blood flow velocity (CBFV) using transcranial Doppler ultrasonography, end-tidal CO₂ (ETCO₂) and respiration during 2-min deep breathing paced at 6 min⁻¹ (0.1 Hz). To assess CA, we evaluated the impact of breathing-induced MAP oscillations on fluctuations of CBFV in the hemispheres with stroke, the non-involved hemispheres and randomly selected hemispheres of controls by applying cross-spectral analysis and calculating coherence, transfer function gain (CBFV–MAP gain) and phase shift angle between the two oscillating signals.ResultsPhase shift angle between MAP and CBFV oscillations showed values >0 and was significantly reduced in the hemispheres without stroke as compared to controls (0.39 ± 0.95 vs. −1.59 ± 0.33 rad, p = 0.015), whereas in the hemispheres with stroke, phase shift angle did not differ significantly from that observed in the control hemispheres. Clinical status of stroke patients significantly improved at discharge from the hospital (NIHSS: 2.0, range: 1–8, p = 0.028).ConclusionsDuring the first days of ischaemic stroke of undetermined aetiology, dynamic cerebral autoregulation is compromised in the non-affected hemisphere, but not in the hemisphere with ischaemic lesion.     

Effect of perindopril on cerebral and renal perfusion on normotensives in mild early ischaemic stroke: a randomized controlled trial

BACKGROUND AND PURPOSE: Blood pressure reduction is central to secondary prevention after stroke, but the optimal time to start therapy is unknown. Cerebral autoregulation is impaired early after ischaemic insult, and any changes in systemic blood pressure may be reflected in cerebral perfusion. However, early initiation in hospital may better assure continued long-term treatment. We have investigated the effect of the angiotensin-converting enzyme inhibitor perindopril on blood pressure, global and focal cerebral blood flow (CBF) and glomerular filtration rate (GFR) in a normotensive acute stroke population. METHODS: Twenty-five patients within 4-8 days of mild ischaemic stroke/transient ischaemic attack and with diastolic blood pressure 70-90 mm Hg were randomized to receive perindopril 2 or 4 mg daily versus placebo according to estimated GFR. Mean arterial blood pressure (MABP), internal carotid artery (ICA) flow and middle cerebral artery velocity (MCAv) were measured prior to dosing, over the following 24 h and at 2 weeks. Brain hexamethyl propylene amino oxide single photon emission computed tomography (SPECT) was performed before dosing and at estimated time of peak drug effect (6-8 h after first dose). GFR measurement using a (51)Cr-ethylene diamine tetraacetic acid technique was undertaken prior to medication and repeated at 2 weeks. RESULTS: MABP was reduced throughout the first 24 h with a mean MABP reduction of 9.3 mm Hg (95% CI 7.4-11.3 mm Hg), maximal placebo corrected fall of 12.5 mm Hg at 10 h post-dose, p = 0.005. No significant change occurred in ICA flow, MCAv or CBF measured by SPECT: change from baseline in symptomatic hemisphere CBF was -0.02 (SD 3.11) ml/100 g/min (treated group) compared with 0 (SD 3.01) (placebo group). Similarly, no significant change was observed in cortical CBF. Mean within-group change in GFR was 2.7 +/- 10.1 in the treated group and -4.3 +/- 6.7 in the placebo group (p = NS). DISCUSSION: Antihypertensive therapy with perindopril may be introduced in the first week after mild ischaemic stroke in normotensive patients without affecting global or regional CBF or affecting GFR.     

Action site of ketanserin enhancing baroreflex function is within the rostral ventrolateral medulla in anesthetized rats

In our previous studies, it was found that ketanserin enhanced baroreflex sensitivity (BRS) in rats and this effect was not blood pressure dependent. The present work was designed to investigate the effects of ketanserin on BRS within the nucleus tractus solitarus (NTS) and the rostral ventrolateral medulla (RVLM). In anesthetized rats, BRS were evaluated by the changes in depressor action of aortic nerve stimulation and bradycardiac response to rapid pressor action of intravenous phenylephrine. It was found that bilateral injection of ketanserin (250 pmol for each side) into the NTS not only significantly increased blood pressure, but also attenuated baroreflex function. Interestingly, when ketanserin was bilaterally injected into RVLM, a significant enhancement of BRS was found and there were no modifications in basal blood pressure and heart period. The present study demonstrates that ketanserin-induced enhancement of BRS mainly occurred within the RVLM, which might contribute to the systemic effects of ketanserin on BRS.     

Serum levels of intercellular adhesion molecule-1 and E-selectin in patients with acute ischaemic stroke

To investigate the role of circulating intercellular adhesion molecule-1 (ICAM-1) and E-selectin in ischaemic stroke, serum levels of ICAM-1 and E-selectin were measured by ELISA in 51 patients with acute ischaemic stroke within 24 h, and in 25 age-matched healthy controls and 10 young healthy volunteers. Carotid Doppler ultrasonography showed a significant stenosis (>50%) of the carotid or vertebrobasilar artery in 11 of 51 stroke patients. Serum levels of ICAM-1 [mean (SE)] were higher (P <0.01) in patients with ischaemic stroke [381 (30) ng/ ml] than in age-matched controls [271 (27) ng/ml] and young controls [246 (6) ng/ml]. There was no significant difference in serum E-selectin levels [mean (SE)] among stroke patients, age-matched and young controls [47 (6), 39 (3), and 41 (3) ng/ ml, respectively; P = NS]. The leucocyte count [mean (SD)] was higher (P < 0.01) in patients with ischaemic stroke [8310 (2800)] than in age-matched controls [6040 (930)]. Serum levels of ICAM-1 and E-selectin did not significantly differ between patients with or without abnormal carotid or vertebrobasilar artery disease. In conclusion, serum ICAM-1 level and leucocyte count were elevated in acute ischaemic stroke within 24 h, while the E-selectin level did not change significantly. This finding suggests that adhesion molecules may play an important role in the post-rolling process of leucocyte-endothelial cell interaction in acute ischaemic stroke. Received: 14 September 1995 Received in revised form: 7 June 1996 Accepted: 26 June 1996     

下肢袖带释放实验在脑血流自动调节评估中的应用现状

下肢袖带释放实验（thigh c uffs r elease t est，TCRT）是由Rune A aslid于1989年首先提出， 在双侧大腿绑上袖带，先充气，后快速放气，使血液重新汇集于双侧大腿，造成动脉血压（arterial blood pressure，ABP）与脑血流速度（cerebral blood flow velocity，CBFV）急骤下降，同时记录ABP和 CBFV的变化，进而评估dCA，是评估dCA常用诱发方法之一。目前临床上TCRT多应用于急性缺血性卒中、 头外伤、重度子痫等的dCA评估。该方法具有价廉、简便、无创、可重复等优势。本文就TCRT在dCA评估 中的应用现状做一简要综述。     

The influence of food ingestion on blood pressure in stroke patients

We aimed to investigate whether and how often changes in blood pressure (BP) were occurring in relation to eating in a large sample of acute stroke patients. BP was measured non-invasively at 5-min intervals from 10 min before the meal, throughout the meal and for 10 min after completion of the meal while the patient was seated. Stroke patients (n = 93) had a higher BP at baseline than both elderly (n = 49) and young controls (n = 20), which was statistically significant. There were no significant differences in the magnitude of change of BP during the meal between the three groups. Compared with the average baseline BP recordings, stroke and elderly control patients, but not young healthy control subjects, had a significant fall in average BP recordings by 3-4 mm Hg. Falls of >/=10 mm Hg in systolic BP immediately after finishing the meal were observed in a similar frequency of stroke (26%) and elderly patients (22%) and in a small number of young controls (10%). These data suggest that acute stroke and elderly patients have similar changes in BP during and immediately after eating. Although reassuring, these results may have greater implications in patients with acute ischaemic stroke, although it is unclear whether changes in BP of this magnitude and duration might influence the fate of the penumbral brain tissue and thus the clinical outcome after stroke.     

Cerebral autoregulation in patients with obstructive sleep apnea syndrome during wakefulness

Background and purpose:  Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for stroke. Impairment of cerebral autoregulation may play a potential role in the pre-disposition to stroke of OSAS patients. In this study, we aimed to assess dynamic cerebral autoregulation (DCA) during wakefulness in OSAS patients and a group of matched controls.
Methods:  Patients and controls were examined in the morning after an overnight complete polysomnography. Mean cerebral blood flow velocity (CBFV) in the middle cerebral artery and mean arterial blood pressure (ABP) were continuously recorded using transcranial Doppler and Finapres. DCA was assessed using the Mx autoregulatory index. Mx is a moving correlation coefficient between mean CBFV and mean ABP. More positive value of Mx indicates worse autoregulation.
Results:  Eleven OSAS patients (mean age ± SD; 52.6 ± 7.9) and 9 controls (mean age ± SD; 49.1 ± 5.3) were enrolled. The mean apnea–hypopnea index (AHI) in the OSAS group was of 22.7 ± 11.6. No significant difference was found between the two groups as for age, body mass index, mean ABP and endtidal CO₂ pressure. Cerebral autoregulation was impaired in OSAS patients compared with controls (Mx index: 0.414 ± 0.138 vs. 0.233 ± 0.100; P  = 0.009). The severity of autoregulation impairment correlated to the severity of the sleep respiratory disturbance measured by the AHI ( P  = 0.003).
Conclusion:  Cerebral autoregulation is impaired in patients with OSAS during wakefulness. Impairment of cerebral autoregulation is correlated with the severity of OSAS.