Effect of antihypertensive agents on cerebral blood flow and flow velocity in acute ischaemic stroke: systematic review of controlled studies

Leukoaraiosis: Epidemiology, Imaging, Risk Factors, and Management of Age-Related Cerebral White Matter Hyperintensities

Leukoaraiosis (LA) manifests as cerebral white matter hyperintensities on T2-weighted magnetic resonance imaging scans and corresponds to white matter lesions or abnormalities in brain tissue. Clinically, it is generally detected in the early 40s and is highly prevalent globally in individuals aged >60 years. From the imaging perspective, LA can present as several heterogeneous forms, including punctate and patchy lesions in deep or subcortical white matter; lesions with periventricular caps, a pencil-thin lining, and smooth halo; as well as irregular lesions, which are not always benign. Given its potential of having deleterious effects on normal brain function and the resulting increase in public health burden, considerable effort has been focused on investigating the associations between various risk factors and LA risk, and developing its associated clinical interventions. However, study results have been inconsistent, most likely due to potential differences in study designs, neuroimaging methods, and sample sizes as well as the inherent neuroimaging heterogeneity and multi-factorial nature of LA. In this article, we provided an overview of LA and summarized the current knowledge regarding its epidemiology, neuroimaging classification, pathological characteristics, risk factors, and potential intervention strategies.

The NADPH Link between the Renin Angiotensin System and the Antioxidant Mechanisms in Dopaminergic Neurons

The renin angiotensin system (RAS) has several components including signaling peptides, enzymes, and membrane receptors. The effort in characterizing this system in the periphery has led to the approval of a class of antihypertensives. Much less is known about RAS in the central nervous system. The production of RAS peptides and the expression of several RAS enzymes and receptors in dopaminergic neurons of the substantia nigra has raised expectations in the therapy of Parkinson's disease, a neurodegenerative condition characterized by lack of dopamine in the striatum, the motor control region of the mammalian brain. On the one hand, dopamine production requires reducing power. On the other hand, reducing power is required by mechanisms involved in REDOX homeostasis. This review focuses on the potential role of RAS in the regulation of neuronal/glial expression of glucose-6-phosphate dehydrogenase, which produces the NADPH required for dopamine synthesis and for reactive oxygen species (ROS) detoxification. It is known that transgenic expression of the gene coding for glucose-6-phosphate dehydrogenase prevents the death of dopaminergic nigral neurons. Signaling via angiotensin II G protein-coupled receptors, AT1 or AT2, leads to the activation of protein kinase A and/or protein kinase C that in turn can regulate glucose-6- phosphate dehydrogenase activity, by Ser/Thr phosphorylation/dephosphorylation events. Long-term effects of AT1 or AT2 receptor activation may also impact on the concentration of the enzyme via activation of transcription factors that participate in the regulation of gene expression in neurons (or glia). Future research is needed to determine how the system can be pharmacologically manipulated to increase the availability of NADPH to neurons degenerating in Parkinson's disease and to neuroprotective glia.

Effect of drug interventions on cerebral hemodynamics in ischemic stroke patients

The ischemic penumbra is sensitive to alterations in cerebral perfusion. A myriad of drugs are used in acute ischemic stroke (AIS) management, yet their impact on cerebral hemodynamics is poorly understood. As part of the Cerebral Autoregulation Network led INFOMATAS project (Identifying New Targets for Management and Therapy in Acute Stroke), this paper reviews some of the most common drugs a patient with AIS will come across and their potential influence on cerebral hemodynamics with a particular focus being on cerebral autoregulation (CA). We first discuss how compounds that promote clot lysis and prevent clot formation could potentially impact cerebral hemodynamics, before focusing on how the different classes of antihypertensive drugs can influence cerebral hemodynamics. We discuss the different properties of each drug and their potential impact on cerebral perfusion and CA. With emerging interest in CA status of AIS patients, either during or soon after treatment when timely reperfusion and salvageable tissue is at its most critical, the properties of these pharmacological agents may be relevant for modelling cerebral perfusion accuracy and for setting individualised treatment strategies.

Age corrected changes in intracranial hemodynamics after carotid endarterectomy

BACKGROUND

Transcranial Doppler ultrasound (TCD) is a frequently used method to monitor brain perfusion during and following carotid endarterectomy (CEA). Our aim was to define the normally occurring changes of intracranial hemodynamics in patients undergoing CEA measuring recently developed TCD parameters.

METHODS

A retrospective, single-center cohort study was performed. Patients undergoing CEA were evaluated pre- and postoperatively from day 0 to day 3 measuring middle cerebral artery flow velocity (MCAFV). The following parameters were analyzed: the first systolic peak (Sys1), the second systolic peak (Sys2) and diastolic flow velocity at a fixed time after heartbeat onset (Dias@560). These parameters linearly decrease with age and were, therefore, transformed to Z-scores.

RESULTS

Three hundred eighteen patients were included with a mean age of 70.8 years. Most patients were male (71%). Compared to preoperatively, the Z-scores of Sys1 and Sys2 were larger on postoperative day 3: +1.12 standard deviation (SD) or 16.0 cm/s (CI: 0.93 to 1.32; P<0.001) and +0.55 SD or 7.8 cm/s (CI: 0.35 to 0.74; P<0.001), respectively. The Z-score for Dias@560 was smaller than preoperatively: -0.23 SD or -1.9 cm/s (CI: -0.41 to -0.05, P=0.015).

CONCLUSIONS

Under normal circumstances Sys1 profits more from CEA than Sys2, whilst diastolic flow velocity decreases. This indicates a return to normal arteriolar vascular resistance. Carefully describing normal changes in MCAFV, may in future enable discrimination of abnormalities, such as hyperperfusion syndrome.

The Hazard of Negative (Not Neutral) Trials on Treatment of Acute Stroke: A Review

Importance

While there are a limited number of beneficial treatments for acute stroke (eg, stroke units, reperfusion, aspirin, hemicraniectomy), there are more negative (as opposed to neutral) interventions spanning multiple different mechanisms of action. To reduce the risk of future negative studies, it is vital to understand why previous interventions appeared to cause harm.

Observations

The limited number of beneficial treatments for acute ischemic stroke are far outnumbered by negative (not neutral) interventions that worsened outcomes in randomized clinical trials (RCTs), including those with putative neuroprotectant, anticoagulant, anti-inflammatory, free radical-scavenging, hemorrhagic, or vasoactive activity. Other agents reduced thrombolytic efficiency or exhibited neuropsychiatric or cardiac toxicity. In intracerebral hemorrhage, platelet transfusion was hazardous. Although reperfusion treatments should be given as soon as possible, very early intervention with other strategies may instead be hazardous, as has been seen with physical therapy and vasodepressors.

Conclusions and Relevance

The lessons learned from negative stroke RCTs are vital for designing future studies. Multicenter preclinical studies are necessary, and animals that die must be included in analyses. Randomized clinical trials must assess multiple neurological, vascular, cardiac, and general safety effects, whether these are on target or off target. All preclinical trials and RCTs must be published in full. Learning from the past will help to reduce the number of negative stroke RCTs in the future.

Nitroglycerin Is Not Associated with Improved Cerebral Perfusion in Acute Ischemic Stroke

OBJECTIVE

The study was conducted to test the hypothesis that nitroglycerin (NTG) increases cerebral perfusion focally and globally in acute ischemic stroke patients, using serial perfusion-weighted imaging (PWI) magnetic resonance imaging measurements.

PATIENTS AND METHODS

Thirty-five patients underwent PWI immediately before and 72 h after administration of a transdermal NTG patch or no treatment. Patients with baseline mean arterial pressure (MAP) > 100 mmHg (NTG group, n = 20) were treated with transdermal NTG (0.2 mg/h) for 72 h, without a nitrate-free interval. Patients with MAP ≤ 100 mmHg (untreated group, n = 15) were not treated. The primary outcome measure was absolute cerebral blood flow (CBF) in the hypoperfused region at 72 h.

RESULTS

The mean baseline absolute CBF in the hypoperfused region was similar in the NTG group (33.3 ± 10.2 ml/100 g/min) and untreated (32.7 ± 8.4 ml/100 g/min, p = 0.4) groups. The median (IQR) baseline infarct volume was 10.4 (2.5-49.3) ml in the NTG group and 32.6 (8.6-96.7) ml in the untreated group (p = 0.09). MAP change in the NTG group was 1.2 ± 12.6 and 8 ± 20.7 mmHg at 2 h and 72 h, respectively. Mean absolute CBF in the hypoperfused region at 72 h was similar in the NTG (29.9 ± 12 ml/100 g/min) and untreated groups (24.1 ± 10 ml/100 g/min, p = 0.8). The median infarct volume increased in untreated (11.8 (5.7-44.2) ml) than the NTG group (3.2 (0.5-16.5) ml; p = 0.033) on univariate analysis, however, there was no difference on regression analysis.

CONCLUSION

NTG was not associated with improvement in cerebral perfusion in acute ischemic stroke patients.

Aging reduces cerebral blood flow regulation following an acute hypertensive stimulus

Aging increases arterial stiffness, which has a negative impact on cerebral blood flow (CBF) regulation (decreases CBF and increases CBF pulsatility). The association between arterial stiffness and CBF pulsatility may, in part, explain the relationship between elevated blood pressure (BP) fluctuations and end-organ disease with aging. To understand the mechanisms by which large BP alterations influence cerebral blood flow regulation in both young and old, we examined the effects of age on central and cerebral blood flow regulation following an acute hypertensive stimulus [resistance-exercise (RE)]. Measurements were obtained pre and immediately, 5, and 30 min post-RE in young (n = 35) and older (n = 26) adults. Measurements included cerebral blood velocity (CBv), CBv pulsatility, central pulse-wave velocity (PWV), beta-stiffness index (β), and carotid blood flow pulsatility. Central hemodynamics and BP were continuously recorded. Mean CBv increased immediately post-RE only in the young and decreased below baseline at 5 min post-RE in both groups (interaction, P < 0.05). Older adults had a greater increase in CBv pulsatility immediately post-RE compared with the young (interaction, P < 0.05). Mean BP was higher and carotid pulsatility was lower in the older group and increased immediately post-RE in both groups (P < 0.05). PWV increased immediately post-RE (P < 0.05). There were no changes in β. In conclusion, with aging, greater central arterial stiffness leads to a greater transmission of pulsatile blood velocity from the systemic circulation to the cerebral circulation following an acute hypertensive stress.NEW & NOTEWORTHY Reductions in cerebral blood flow and increases in flow pulsatility with aging are associated to cerebrovascular disease; however, little is known about how an acute hypertensive stimulus effects cerebral blood flow regulation in an aged population. Following the hypertensive stimulus, older adults elicit an attenuated increase in cerebral blood velocity and greater transmission of pulsatile velocity to the brain compared with young adults, demonstrating reduced cerebral blood flow regulation to elevated blood pressure responses with aging.

Blood pressure reduction in hypertensive acute ischemic stroke patients does not affect cerebral blood flow

The effect of blood pressure (BP) reduction on cerebral blood flow (CBF) in acute ischemic stroke is unknown. We measured regional CBF with perfusion-weighted MRI before and after BP treatment in a three-armed non-randomized prospective controlled trial. Treatment arm assignment was based on acute mean arterial pressure (MAP). Patients with (MAP) >120 mmHg (n = 14) were treated with intravenous labetalol and sublingual (SL) nitroglycerin (labetalol group). Those with MAP 100-120 mmHg (n = 17) were treated with SL nitroglycerin (0.3 mg) ('NTG Group') and those with baseline MAP<100 mmHg (n = 18) were not treated with antihypertensive drugs (untreated group). Forty-nine patients (18 female, mean age 65.3 ± 12.9 years) were serially imaged. Labetalol reduced MAP by 12.5 (5.7-17.7) mmHg, p = 0.0002. MAP remained stable in the NTG (6.0 (0.4-16, p = 0.3) mmHg and untreated groups (-0.3 (-2.3-7.0, p = 0.2) mmHg. The volume of total hypoperfused tissue (CBF<18 ml/100 g/min) did not increase after labetalol (-1.1 ((-6.5)-(-0.2)) ml, p = 0.1), NTG (0 ((-1.5)-4.5) ml, p = 0.72), or no treatment 0.25 ((-10.1)-4.5) ml, p = 0.87). Antihypertensive therapy, based on presenting BP, in acute stroke patients was not associated with an increased volume of total hypoperfused tissue.

Effects of vasodilating medications on cerebral haemodynamics in health and disease: systematic review and meta-analysis

Objectives:

Vasodilating antihypertensives prevent stroke and potentially cerebral small vessel disease but their effects on cerebrovascular haemodynamics beyond blood pressure lowering are unclear.

Methods:

We searched PubMed, Medline, Embase, Cinahl, Psychinfo, Health Business Elite and Health Management Information Consortium for randomized studies of vasodilating medications, compared to no treatment or nonvasodilators, that reported effects on cerebral blood flow (CBF), mean blood flow velocity (MFV) or cerebrovascular reactivity. Absolute and standardized mean differences (SMD) were combined by inverse-variance weighted fixed or random-effects meta-analysis stratified by study design, population characteristics and vasodilator class.

Results:

In 35 studies reporting 57 comparisons, there was a reduction in SBP (−4.13 mmHg, −7.55 to −0.71, P = 0.018) but no change in MFV (ΔMFV 1.11, confidence interval −0.93 to 3.14, P = 0.29, 23 comparisons). MFV increased in patients with underlying conditions (3.41, 0.24 to 6.57, P = 0.04) but not in healthy study participants (−1.27, −5.18 to 2.64, P = 0.68), with no differences by vasodilating drug class. Cerebral pulsatility index was reduced across all studies (Δ pulsatility index −0.04, −0.07 to −0.02, P = 0.001; Δ pulsatility index -SMD −0.32, −0.47 to −0.16, P < 0.001), except in studies reporting responses to single drug doses (Δ pulsatility index 0.00, −0.09 to −0.08, P = 0.93). Despite evidence of reporting and publication bias, there was an apparent consistent reduction in CBF with vasodilators (CBF-SMD −0.24, −0.46 to −0.02, P = 0.03) with a significant increase in cerebrovascular reactivity-SMD (0.48, 0.13–0.83, P = 0.007).

Conclusions:

Despite reducing SBP, vasodilators did not significantly impair absolute CBF but improved cerebrovascular pulsatility and reactivity, suggesting therapeutic potential in preventing stroke and cerebral small vessel disease.

Blood Pressure and Early Clinical Outcome Among Acute Ischemic Stroke Patients

Objectives:

The association between blood pressure (BP) and short-term clinical outcome of acute ischemic stroke is inconclusive. We investigated the association between BP in the first 72 hours following admission and death in-hospital and neurologic deficiency at discharge among patients with acute ischemic stroke.

Methods:

A total of 2675 acute ischemic stroke patients confirmed by a computed tomography scan or magnetic resonance imaging were included in the present study. Blood pressure in the first 72 hours after admission and other study variables were collected for all ischemic stroke patients. Neurological functions National Institute of Health Stroke Scale (NIHSS) were evaluated by trained neurologists at discharge. The study outcome was defined as death in-hospital and neurologic deficiency (NIHSS≥10) at discharge.

Results:

Systolic and diastolic BP were significantly and positively associated with odds of study outcome in acute ischemic stroke. For example, compared to those with a systolic BP<140 mmHg, multiple-adjusted odds ratio (95% confidence interval) of study outcome was 3.29(1.22, 8.90) among participants with systolic BP of 180-219 mmHg,P<0.05; compared to those with a diastolic BP<90 mmHg, multiple-adjusted odds ratio of study outcome was 7.05(1.32, 37.57) among participants with diastolic BP ≥ 120 mmHg,P<0.05.

Conclusion:

Systolic BP≥180 and diastolic BP≥120 were significantly and positively associated with death in-hospital or neurologic deficiency at discharge among patients with acute ischemic stroke.

The impact of hypertension on cerebral perfusion and cortical thickness in older adults

Hypertension may increase risk for dementia possibly because of its association with decreased cortical thickness. Disturbed cerebral autoregulation is one plausible mechanism by which hypertension impacts the cerebral structure, but the associations among hypertension, brain perfusion, and cortical thickness are poorly understood. The current sample consisted of 58 older adults with varying levels of vascular disease. Diagnostic history of hypertension and antihypertensive medication status was ascertained through self-report, and when available, confirmed by medical record review. All participants underwent arterial spin labeling and T1-weighted magnetic resonance imaging to quantify total and regional cortical perfusion and thickness. Analysis of covariance adjusting for medical variables showed that participants with hypertension exhibited reduced temporal and occipital brain perfusion and total and regional cortical thickness relative to those without hypertension. The effects of hypertension on total brain perfusion remained unchanged even after adjustment for age, although no such pattern emerged for cortical thickness. Decreased total brain perfusion predicted reduced thickness of the total brain and of the frontal, temporal, and parietal lobe cortices. Antihypertensive treatment was not associated with total cerebral perfusion or cortical thickness. This study provides initial evidence for the adverse effects of a diagnostic history of hypertension on brain hypoperfusion and reduced cortical thickness. Longitudinal studies are needed to investigate the role of hypertension and its interaction with other contributing factors (e.g., age) in the manifestation of cerebral hypoperfusion and reduced cortical thickness.

High blood pressure on admission in relation to poor outcome in acute ischemic stroke with intracranial atherosclerotic stenosis or occlusion

BACKGROUND

Intracranial atherosclerotic stenosis is common in Asian, black, and Hispanic individuals. However, the management of blood pressure (BP) in the setting of acute stage in these patients is controversial. The present study aims to explore the relationship between BP on admission and outcomes in acute ischemic stroke patients with intracranial atherosclerotic stenosis or occlusion.

METHODS

We prospectively registered consecutive cases of acute ischemic stroke from September 01, 2009, to August 31, 2011. Patients with severe intracranial stenosis or occlusion were included. Death or disability was followed up at the end of the third month. The multivariate logistic regression model was used to analyze the relationship between BP on admission and clinical outcomes.

RESULTS

We included 215 cases, which accounted for 22.7% (215 of 946) of the total registered cases. The mean age was 60.44±13.23 years. The median time of symptoms onset to admission was 72 hours (2-270 hours). Patients with systolic blood pressure (SBP) of 120-159 mm Hg or diastolic BP of 70-89 mm Hg had the lowest death or disability. After adjustment of confounders, SBP of 160 mm Hg or more on admission was the independent predictor of death or disability at the third month (relative risk [RR], 2.89; 95% confidence interval [CI], 1.20-6.91). SBP less than 120 mm Hg on admission had a trend of increasing death or disability (RR, 1.96; 95% CI, .60-6.33).

CONCLUSIONS

Higher BP on admission was associated with an increased risk of death or disability in patients with symptomatic intracranial artery stenosis or occlusion. It is reasonable that further studies on the effects of BP lowering in acute stroke include these patients.

Effect of Telmisartan on Cerebral and Systemic Haemodynamics in Patients with Recent Ischaemic Stroke: A Randomised Controlled Trial

High blood pressure (BP) is common in acute stroke and is independently associated with a poor outcome. Lowering BP might improve outcome if cerebral blood flow (CBF) is unaffected in the presence of dysfunctional autoregulation. We investigated the effect of telmisartan on systemic and cerebral haemodynamics in patients with recent stroke. Patients with ischaemic stroke (<5 days) were randomised to 90 days of telmisartan (80 mg) or placebo. CBF (primary outcome) was measured using xenon CT at baseline and 4 hours. BP and transcranial doppler (TCD) were performed at baseline, 4 hours after-treatment, and on days 4, 7, and 90. Cerebral perfusion pressure and zero filling pressure (ZFP) were calculated. Of a planned 24 patients, 17 were recruited. Telmisartan significantly accentuated the fall in systolic and diastolic BP over 90 days (treatment-time interaction p=0.047, p=0.003, resp.) but did not alter BP at 4 hours after treatment (171/99 versus 167/87 mmHg), CBF, or CBF velocity. ZFP was significantly lower in the treatment group (p=0.018). Impairment at 7 days and dependency at 90 days did not differ between the groups. In this underpowered study, telmisartan did not significantly alter BP or CBF after the first dose. Telmisartan reduced BP over the subsequent 90 days and significantly lowered ZFP. This trial is registered with ISRCTN 41456162.

Unsolved issues in the management of high blood pressure in acute ischemic stroke

High blood pressure is common in acute stroke patients. Very high as well as very low blood pressure is associated with poor outcome. Spontaneous fall of blood pressure within the first few days after stroke was associated both with neurological improvement and impairment. Several randomized trials investigated the pharmacological reduction of blood pressure versus control. Most trials showed no significant difference in their primary outcome apart from the INWEST trial which found an increase of poor outcome when giving intravenous nimodipine. Nevertheless, useful information can be extracted from the published data to help guide the clinician's decision. Blood pressure should only be lowered when it is clearly elevated, and early after onset, reduction should be moderate but may be achieved rapidly. No clear recommendations can be given on the substances to use; however, care should be taken with intravenous calcium channel blockers and angiotensin receptor antagonists. Two ongoing randomized trials will help to solve the questions on blood pressure management in acute stroke.

Elevated blood pressure in the acute phase of stroke and the role of Angiotensin receptor blockers

Raised blood pressure (BP) is common after stroke but its causes, effects, and management still remain uncertain. We performed a systematic review of randomized controlled trials that investigated the effects of the angiotensin receptor blockers (ARBs) administered in the acute phase (≤72 hours) of stroke on death and dependency. Trials were identified from searching three electronic databases (Medline, Cochrane Library and Web of Science Database). Three trials involving 3728 patients were included. Significant difference in BP values between treatment and placebo was found in two studies. No effect of the treatment was seen on dependency, death and vascular events at one, three or six months; the cumulative mortality and the number of vascular events at 12 months differed significantly in favour of treatment in one small trial which stopped prematurely. Evidence raises doubts over the hypothesis of a specific effect of ARBs on short- and medium-term outcomes of stroke. It is not possible to rule out that different drugs might have different effects. Further trials are desirable to clarify whether current findings are generalizable or there are subgroups of patients or different approaches to BP management for which a treatment benefit can be obtained.

Elevated blood pressure management in acute ischemic stroke remains controversial: could this issue be resolved?

A transient elevated arterial blood pressure is common in acute ischemic stroke and is often associated with a poor prognosis. The underlying mechanisms of blood pressure elevation are not well understood and its management is still unresolved. This article focuses on pathophysiology and management of elevated blood pressure in acute ischemic stroke. There is evidence that the main causes of a transient blood pressure elevation in acute ischemic stroke are the focal cerebral hypoperfusion and the stress responses with neuroendocrine systems activation. Clinical trials have reported that blood pressure lowering in acute ischemic stroke may have detrimental effect, probably because of impaired cerebral autoregulation. However, quantitative assessment of cerebral perfusion has not been performed during emergency blood pressure reduction in acute ischemic stroke. We suggest that ultrasound carotid artery disease evaluation and cerebral hemodynamics monitoring using bilateral transcranial ultrasonography, during blood pressure management in acute ischemic stroke might contribute to maintaining of an adequate penumbral perfusion and prevent infarct enlargement. Such an approach could individualize the antihypertensive treatment in acute ischemic stroke and improve functional outcome. Prospective studies are needed to confirm such a treatment strategy.

Impaired cerebral autoregulation is associated with brain atrophy and worse functional status in chronic ischemic stroke

Dynamic cerebral autoregulation (dCA) is impaired following stroke. However, the relationship between dCA, brain atrophy, and functional outcomes following stroke remains unclear. In this study, we aimed to determine whether impairment of dCA is associated with atrophy in specific regions or globally, thereby affecting daily functions in stroke patients.

We performed a retrospective analysis of 33 subjects with chronic infarctions in the middle cerebral artery territory, and 109 age-matched non-stroke subjects. dCA was assessed via the phase relationship between arterial blood pressure and cerebral blood flow velocity. Brain tissue volumes were quantified from MRI. Functional status was assessed by gait speed, instrumental activities of daily living (IADL), modified Rankin Scale, and NIH Stroke Score.

Compared to the non-stroke group, stroke subjects showed degraded dCA bilaterally, and showed gray matter atrophy in the frontal, parietal and temporal lobes ipsilateral to infarct. In stroke subjects, better dCA was associated with less temporal lobe gray matter atrophy on the infracted side ( = 0.029), faster gait speed ( = 0.018) and lower IADL score (0.002). Our results indicate that better dynamic cerebral perfusion regulation is associated with less atrophy and better long-term functional status in older adults with chronic ischemic infarctions.

Autoregulation after ischaemic stroke

OBJECTIVES

Absent outcome data from randomized clinical trials, management of hypertension in acute ischaemic stroke remains controversial. Data from human participants have failed to resolve the question whether cerebral blood flow (CBF) in the peri-infarct region will decrease due to impaired autoregulation when systemic mean arterial pressure (MAP) is rapidly reduced.

METHODS

Nine participants, 1-11 days after hemispheric ischaemic stroke, with systolic blood pressure more than 145 mmHg, underwent baseline PET measurements of regional CBF. Intravenous nicardipine infusion was then used to rapidly reduce mean arterial pressure 16 +/- 7 mmHg and CBF measurement was repeated.

RESULTS

Compared with the contralateral hemisphere, there were no significant differences in the percent change in CBF in the infarct (P = 0.43), peri-infarct region (P = 1.00) or remainder of the ipsilateral hemisphere (P = 0.50). Two participants showed CBF reductions of greater than 19% in both hemispheres.

CONCLUSION

In this study, selective regional impairment of CBF autoregulation in the infarcted hemisphere to reduced systemic blood pressure was not a characteristic of acute cerebral infarction. Reductions in CBF did occur in some individuals, but it was bihemispheric phenomenon that likely was due to an upward shift of the autoregulatory curve as a consequence of chronic hypertension. These results indicate individual monitoring of changes in global CBF, such as with bedside transcranial Doppler, may be useful to determine individual safe limits when MAP is lowered in the setting of acute ischaemic stroke. The benefit of such an approach can only be demonstrated by clinical trials demonstrating improved patient outcome.

Effects of antihypertensive treatment after acute stroke in the Continue or Stop Post-Stroke Antihypertensives Collaborative Study (COSSACS): a prospective, randomised, open, blinded-endpoint trial

BACKGROUND

Up to 50% of patients with acute stroke are taking antihypertensive drugs on hospital admission. However, whether such treatment should be continued during the immediate post-stroke period is unclear. We therefore aimed to assess the efficacy and safety of continuing or stopping pre-existing antihypertensive drugs in patients who had recently had a stroke.

METHODS

The Continue or Stop Post-Stroke Antihypertensives Collaborative Study (COSSACS) was a UK multicentre, prospective, randomised, open, blinded-endpoint trial. Patients were recruited at 49 UK National Institute for Health Research Stroke Research Network centres from January 1, 2003, to March 31, 2009. Patients aged over 18 years who were taking antihypertensive drugs were enrolled within 48 h of stroke and the last dose of antihypertensive drug. Patients were randomly assigned (1:1) by secure internet central randomisation to either continue or stop pre-existing antihypertensive drugs for 2 weeks. Patients and clinicians who randomly assigned patients were unmasked to group allocation. Clinicians who assessed 2-week outcomes and 6-month outcomes were masked to group allocation. The primary endpoint was death or dependency at 2 weeks, with dependency defined as a modified Rankin scale score greater than 3 points. Analysis was by intention to treat. This trial is registered with the International Standard Randomised Controlled Trial Register, number ISRCTN89712435.

FINDINGS

763 patients were assigned to continue (n=379) or stop (n=384) pre-existing antihypertensive drugs. 72 of 379 patients in the continue group and 82 of 384 patients in the stop group reached the primary endpoint (relative risk 0.86, 95% CI 0.65-1.14; p=0.3). The difference in systolic blood pressure at 2 weeks between the continue group and the stop group was 13 mm Hg (95% CI 10-17) and the difference in diastolic blood pressure was 8 mm Hg (6-10; difference between groups p<0.0001). No substantial differences were observed between groups in rates of serious adverse events, 6-month mortality, or major cardiovascular events.

INTERPRETATION

Continuation of antihypertensive drugs did not reduce 2-week death or dependency, cardiovascular event rate, or mortality at 6 months. Lower blood pressure levels in those who continued antihypertensive treatment after acute mild stroke were not associated with an increase in adverse events. These neutral results might be because COSSACS was underpowered owing to early termination of the trial, and support the continuation of ongoing research trials.

FUNDING

The Health Foundation and The Stroke Association.

Effect of Telmisartan on Functional Outcome, Recurrence, and Blood Pressure in Patients With Acute Mild Ischemic Stroke

Background and Purpose— High blood pressure (BP) is common in acute ischemic stroke and associated independently with a poor functional outcome. However, the management of BP acutely remains unclear because no large trials have been completed.

Methods— The factorial PRoFESS secondary stroke prevention trial assessed BP-lowering and antiplatelet strategies in 20 332 patients; 1360 were enrolled within 72 hours of ischemic stroke, with telmisartan (angiotensin receptor antagonist, 80 mg/d, n=647) vs placebo (n=713). For this nonprespecified subgroup analysis, the primary outcome was functional outcome at 30 days; secondary outcomes included death, recurrence, and hemodynamic measures at up to 90 days. Analyses were adjusted for baseline prognostic variables and antiplatelet assignment.

Results— Patients were representative of the whole trial (age 67 years, male 65%, baseline BP 147/84 mm Hg, small artery disease 60%, NIHSS 3) and baseline variables were similar between treatment groups. The mean time from stroke to recruitment was 58 hours. Combined death or dependency (modified Rankin scale: OR, 1.03; 95% CI, 0.84–1.26; P =0.81; death: OR, 1.05; 95% CI, 0.27–4.04; and stroke recurrence: OR, 1.40; 95% CI, 0.68–2.89; P =0.36) did not differ between the treatment groups. In comparison with placebo, telmisartan lowered BP (141/82 vs 135/78 mm Hg, difference 6 to 7 mm Hg and 2 to 4 mm Hg; P <0.001), pulse pressure (3 to 4 mm Hg; P <0.002), and rate-pressure product (466 mm Hg.bpm; P =0.0004).

Conclusion— Treatment with telmisartan in 1360 patients with acute mild ischemic stroke and mildly elevated BP appeared to be safe with no excess in adverse events, was not associated with a significant effect on functional dependency, death, or recurrence, and modestly lowered BP.

Is lowering blood pressure hazardous in patients with significant ipsilateral carotid stenosis and acute ischaemic stroke? Interim assessment in the 'Efficacy of Nitric Oxide in Stroke' trial

BACKGROUND

High blood pressure (BP) in acute stroke patients is both common and associated with a poor outcome, although best management remains unclear. Particular uncertainty exists in patients with carotid stenosis in whom lowering BP might reduce cerebral perfusion and worsen outcome.

METHODS

Efficacy of Nitric Oxide in Stroke (ENOS) is an international, randomized controlled trial investigating the effect of lowering BP with glyceryl trinitrate in 5000 patients with acute stroke. This analysis is based on patients with ischaemic stroke for whom information on the carotid status was available. Neurological impairment (Scandinavian Stroke Scale) and rate of recurrent stroke were assessed on day 7, and the functional outcome (modified Rankin score) was determined on day 90. ENOS is ongoing, therefore analyses are blinded to treatment.

RESULTS

At the time of analysis, 565 patients with ischaemic stroke had been randomized into ENOS and data on carotid status were available in 394 (70%) of these patients. Ipsilateral stenosis > or =50% was present in 50 patients (13%). Six of 344 (2%, 95% confidence interval: 0.7, 4%) patients with ipsilateral stenosis <50% had a recurrent stroke by 7 days as compared with none of 50 patients (0%, 95% confidence interval: 0, 9%) (P=0.73) with stenosis > or =50%. No significant difference in impairment was present on day 7; mean Scandinavian Stroke Scale with stenosis 38.3 versus no stenosis 43.2 (P=0.48). Adjusted functional outcome after 90 days was worse in those with a baseline carotid stenosis > or =50%; median modified Rankin score 3.0 versus 2.0 (P=0.03).

CONCLUSION

Interim data provide reassurance that it is reasonable to continue including patients with carotid stenosis into trials of acute BP lowering (such as ENOS).

Drug interactions at the blood-brain barrier: fact or fantasy?

There is considerable interest in the therapeutic and adverse outcomes of drug interactions at the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). These include altered efficacy of drugs used in the treatment of CNS disorders, such as AIDS dementia and malignant tumors, and enhanced neurotoxicity of drugs that normally penetrate poorly into the brain. BBB- and BCSFB-mediated interactions are possible because these interfaces are not only passive anatomical barriers, but are also dynamic in that they express a variety of influx and efflux transporters and drug metabolizing enzymes. Based on studies in rodents, it has been widely postulated that efflux transporters play an important role at the human BBB in terms of drug delivery. Furthermore, it is assumed that chemical inhibition of transporters or their genetic ablation in rodents is predictive of the magnitude of interaction to be expected at the human BBB. However, studies in humans challenge this well-established paradigm and claim that such drug interactions will be lesser in magnitude but yet may be clinically significant. This review focuses on current known mechanisms of drug interactions at the blood-brain and blood-CSF barriers and the potential impact of such interactions in humans. We also explore whether such drug interactions can be predicted from preclinical studies. Defining the mechanisms and the impact of drug-drug interactions at the BBB is important for improving efficacy of drugs used in the treatment of CNS disorders while minimizing their toxicity as well as minimizing neurotoxicity of non-CNS drugs.

Impaired cerebral autoregulation in obstructive sleep apnea

Obstructive sleep apnea (OSA) increases the risk of stroke independent of known vascular and metabolic risk factors. Although patients with OSA have higher prevalence of hypertension and evidence of hypercoagulability, the mechanism of this increased risk is unknown. Obstructive apnea events are associated with surges in blood pressure, hypercapnia, and fluctuations in cerebral blood flow. These perturbations can adversely affect the cerebral circulation. We hypothesized that patients with OSA have impaired cerebral autoregulation, which may contribute to the increased risk of cerebral ischemia and stroke. We examined cerebral autoregulation in patients with and without OSA by measuring cerebral artery blood flow velocity (CBFV) by using transcranial Doppler ultrasound and arterial blood pressure using finger pulse photoplethysmography during orthostatic hypotension and recovery as well as during 5% CO2 inhalation. Cerebral vascular conductance and reactivity were determined. Forty-eight subjects, 26 controls (age 41.0±2.3 yr) and 22 OSA (age 46.8±2.3 yr) free of cerebrovascular and active coronary artery disease participated in this study. OSA patients had a mean apnea-hypopnea index of 78.4±7.1 vs. 1.8±0.3 events/h in controls. The oxygen saturation during sleep was significantly lower in the OSA group (78±2%) vs. 91±1% in controls. The dynamic vascular analysis showed mean CBFV was significantly lower in OSA patients compared with controls (48±3 vs. 55±2 cm/s; P <0.05, respectively). The OSA group had a lower rate of recovery of cerebrovascular conductance for a given drop in blood pressure compared with controls (0.06±0.02 vs. 0.20±0.06 cm·s−2·mmHg−1; P <0.05). There was no difference in cerebrovascular vasodilatation in response to CO2. The findings showed that patients with OSA have decreased CBFV at baseline and delayed cerebrovascular compensatory response to changes in blood pressure but not to CO2. These perturbations may increase the risk of cerebral ischemia during obstructive apnea.