Derangement of regional cerebral blood flow and of its regulatory mechanisms in acute cerebrovascular lesions

Whole Blood Viscosity and Cerebral Blood Flow in Acute Ischemic Stroke

Existing effective treatments for ischemic stroke restore blood supply to the ischemic region using thrombolysis or mechanical removal of clot. However, it is increasingly recognized that successful removal of occlusive thrombus from the large artery-recanalization, may not always be accompanied by successful restoration of blood flow to the downstream tissues-reperfusion. Ultimately, brain tissue survival depends on cerebral perfusion, and a functioning microcirculation. Because capillary diameter is often equal to or smaller than an erythrocyte, microcirculation is largely dependent on erythrocyte rheological (hemorheological) factors such as whole blood viscosity (WBV). Several studies in the past have demonstrated elevated WBV in stroke compared with healthy controls. Also, elevated WBV has shown to be an independent risk factor for stroke. Elevated WBV leads to endothelial dysfunction, decreases nitric oxide-dependent flow-mediated vasodilation, and promotes hemostatic alterations/thrombosis, all leading to microcirculation sludging. Compromised microcirculation further leads to decreased cerebral perfusion. Hence, modulating WBV through pharmacological agents might be beneficial to improve cerebral perfusion in stroke. This review discusses the effect of elevated WBV on endothelial function, hemostatic alterations, and thrombosis leading to reduced cerebral perfusion in stroke.

Whole blood viscosity is associated with baseline cerebral perfusion in acute ischemic stroke

Whole blood viscosity (WBV) is the intrinsic resistance to flow developed due to the frictional force between adjacent layers of flowing blood. Elevated WBV is an independent risk factor for stroke. Poor microcirculation due to elevated WBV can prevent adequate perfusion of the brain and might act as an important secondary factor for hypoperfusion in acute ischaemic stroke. In the present study, we examined the association of WBV with basal cerebral perfusion assessed by CT perfusion in acute ischaemic stroke. Confirmed acute ischemic stroke patients (n = 82) presenting in hours were recruited from the single centre. Patients underwent baseline multimodal CT (non-contrast CT, CT angiography and CT perfusion). Where clinically warranted, patients also underwent follow-up DWI. WBV was measured in duplicate within 2 h after sampling from 5-mL EDTA blood sample. WBV was significantly correlated with CT perfusion parameters such as perfusion lesion volume, ischemic core volume and mismatch ratio; DWI volume and baseline NIHSS. In a multivariate linear regression model, WBV significantly predicted acute perfusion lesion volume, core volume and mismatch ratio after adjusting for the effect of occlusion site and collateral status. Association of WBV with hypoperfusion (increased perfusion lesion volume, ischaemic core volume and mismatch ratio) suggest the role of erythrocyte rheology in cerebral haemodynamic of acute ischemic stroke. The present findings open new possibilities for therapeutic strategies targeting erythrocyte rheology to improve cerebral microcirculation in stroke.

Effect of Dexmedetomidine in Preventing Postoperative Side Effects for Laparoscopic Surgery: A Meta-Analysis of Randomized Controlled Trials and Trial Sequential Analysis (PRISMA)

Dexmedetomidine (DEX) has been used extensively for patients during surgery. Some studies found that DEX could reduce the incidence of postoperative side effects in laparoscopic surgical patients. However, no firm conclusions were made about it.The authors searched for randomized controlled trials (RCTs) in PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials testing DEX administrated in laparoscopic surgical patients and reporting on postoperative nausea, vomiting, shivering, heart rate, mean arterial pressure (MAP), or extubation time after surgery or within 1 hour in postoperative care unit. Trial sequential analysis (TSA) was used for RCTs comparing DEX with placebo or no treatment in laparoscopic surgery patients. A protocol for this meta-analysis has been registered on PROSPERO (http://www.crd.york.ac.uk/prospero) and the registration number is CRD42015020226.Fifteen studies (899 patients) were included. DEX could significantly reduce the incidence of postoperative nausea (risk ratio [RR] and 95% confidence interval [CI], 0.43 [0.28, 0.66], P < 0.0001), vomiting (RR and 95% CI, 0.36 [0.18, 0.72], P = 0.004), shivering (RR and 95% CI, 0.19 [0.11, 0.35], P < 0.00001), rescue antiemetic (RR and 95% CI, 0.18 [0.07, 0.47], P = 0.0006), and increase the incidence of dry mouth (RR and 95% CI, 7.40 [2.07, 26.48], P = 0.002) comparing with the control group. In addition, firm conclusions can be made on the results of postoperative nausea according to the TSA. Meta-analysis showed that DEX group had a significantly lower heart rate (mean difference [MD] and 95% CI, -14.21 [-18.85, -9.57], P < 0.00001) and MAP (MD and 95% CI, -12.35 [-15.28, -9.42], P < 0.00001) than the control group, and firm conclusions can be made according to the TSA. No significance was observed on extubation time between 2 groups (MD and 95% CI, 0.70 [-0.89, 2.28], P = 0.39).The results from this meta-analysis indicated that perioperative DEX decreased postoperative nausea and shivering in laparoscopic surgical patients. However, common adverse effects were lower heart rate and MAP. Firm conclusions cannot be made on postoperative shivering, rescue antiemetic, and dry mouth until more RCTs were included.

The vascular steal phenomenon is an incomplete contributor to negative cerebrovascular reactivity in patients with symptomatic intracranial stenosis

'Vascular steal' has been proposed as a compensatory mechanism in hemodynamically compromised ischemic parenchyma. Here, independent measures of cerebral blood flow (CBF) and blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) responses to a vascular stimulus in patients with ischemic cerebrovascular disease are recorded. Symptomatic intracranial stenosis patients (n=40) underwent a multimodal 3.0T MRI protocol including structural (T1-weighted and T2-weighted fluid-attenuated inversion recovery) and hemodynamic (BOLD and CBF-weighted arterial spin labeling) functional MRI during room air and hypercarbic gas administration. CBF changes in regions demonstrating negative BOLD reactivity were recorded, as well as clinical correlates including symptomatic hemisphere by infarct and lateralizing symptoms. Fifteen out of forty participants exhibited negative BOLD reactivity. Of these, a positive relationship was found between BOLD and CBF reactivity in unaffected (stenosis degree<50%) cortex. In negative BOLD cerebrovascular reactivity regions, three patients exhibited significant (P<0.01) reductions in CBF consistent with vascular steal; six exhibited increases in CBF; and the remaining exhibited no statistical change in CBF. Secondary findings were that negative BOLD reactivity correlated with symptomatic hemisphere by lateralizing clinical symptoms and prior infarcts(s). These data support the conclusion that negative hypercarbia-induced BOLD responses, frequently assigned to vascular steal, are heterogeneous in origin with possible contributions from autoregulation and/or metabolism.

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.

Autoregulation of cerebral blood flow to changes in arterial pressure in mild Alzheimer's disease

Studies in transgenic mice overexpressing amyloid precursor protein (APP) demonstrate impaired autoregulation of cerebral blood flow (CBF) to changes in arterial pressure and suggest that cerebrovascular dysfunction may be critically important in the development of pathological Alzheimer's disease (AD). Given the relevance of such a finding for guiding hypertension treatment in the elderly, we assessed autoregulation in individuals with AD. Twenty persons aged 75±6 years with very mild or mild symptomatic AD (Clinical Dementia Rating 0.5 or 1.0) underwent (15)O-positron emission tomography (PET) CBF measurements before and after mean arterial pressure (MAP) was lowered from 107±13 to 92±9 mm Hg with intravenous nicardipine; (11)C-PIB-PET imaging and magnetic resonance imaging (MRI) were also obtained. There were no significant differences in mean CBF before and after MAP reduction in the bilateral hemispheres (-0.9±5.2 mL per 100 g per minute, P=0.4, 95% confidence interval (CI)=-3.4 to 1.5), cortical borderzones (-1.9±5.0 mL per 100 g per minute, P=0.10, 95% CI=-4.3 to 0.4), regions of T2W-MRI-defined leukoaraiosis (-0.3±4.4 mL per 100 g per minute, P=0.85, 95% CI=-3.3 to 3.9), or regions of peak (11)C-PIB uptake (-2.5±7.7 mL per 100 g per minute, P=0.30, 95% CI=-7.7 to 2.7). The absence of significant change in CBF with a 10 to 15 mm Hg reduction in MAP within the normal autoregulatory range demonstrates that there is neither a generalized nor local defect of autoregulation in AD.

Effect of parenteral or oral vinpocetine on the hemorheological parameters of patients with chronic cerebrovascular diseases

INTRODUCTION

Hemorheological factors play an important role in the pathomechanism of ischemic cerebrovascular disorders. Abnormal rheological conditions in patients with chronic cerebrovascular disease predispose for recurrent strokes. Vinpocetine (VP), a synthetic ethyl esther of apovincamine, has successfully been used in the treatment of cerebrovascular diseases, in part because of its favourable rheological effects.

PATIENTS AND METHODS

The study investigates the hemorheological changes in 40 patients in the chronic stage of ischemic cardiovascular disease after administration of vinpocetine. All patients received a high dose of intravenous VP in doses gradually increased to l mg/kg/day. In addition, 20 patients (mean age: 61+/-8 years) received 30 mg VP orally for 3 months. The other 20 patients (mean age: 59+/-6 years), who received placebo tablets, served as controls. Hemorheological parameters (hematocrit, plasma fibrinogen, whole blood viscosity, red blood cell aggregation and deformability) were evaluated at 1 and 3 months.

RESULTS

The high-dose parenteral VP significantly decreased red blood cell aggregation, plasma and whole blood viscosity (p < 0.05) compared to the initial values. In patients with additional oral treatment, plasma and whole blood viscosities were significantly lower compared to the placebo patients at 3 months (p < 0.05).

CONCLUSION

Our results confirmed the beneficial rheological effects of high-dose parenteral VP (partially caused by hemodilution) observed previously, and also warrant its long-term oral admission to maintain the beneficial rheological changes.

Controlling hypertension and hypotension immediately post-stroke (CHHIPS): a randomised, placebo-controlled, double-blind pilot trial

BACKGROUND

Raised blood pressure is common after acute stroke and is associated with an adverse prognosis. We sought to assess the feasibility, safety, and effects of two regimens for lowering blood pressure in patients who have had a stroke.

METHODS

Patients who had cerebral infarction or cerebral haemorrhage and were hypertensive (systolic blood pressure [SBP] >160 mm Hg) were randomly assigned by secure internet central randomisation to receive oral labetalol, lisinopril, or placebo if they were non-dysphagic, or intravenous labetalol, sublingual lisinopril, or placebo if they had dysphagia, within 36 h of symptom onset in this double-blind pilot trial. The doses were titrated up if target blood pressure was not reached. Analysis was by intention to treat. This trial is registered with the National Research Register, number N0484128008.

FINDINGS

179 patients (mean age 74 [SD 11] years; SBP 181 [SD 16] mm Hg; diastolic blood pressure [DBP] 95 [SD 13] mm Hg; median National Institutes of Health stroke scale [NIHSS] score 9 [IQR 5-16] points) were randomly assigned to receive labetolol (n=58), lisinopril (n=58), or placebo (n=63) between January, 2005, and December, 2007. The primary outcome--death or dependency at 2 weeks--occurred in 61% (69) of the active and 59% (35) of the placebo group (relative risk [RR] 1.03, 95% CI 0.80-1.33; p=0.82). There was no evidence of early neurological deterioration with active treatment (RR 1.22, 0.33-4.54; p=0.76) despite the significantly greater fall in SBP within the first 24 h in this group compared with placebo (21 [17-25] mm Hg vs 11 [5-17] mm Hg; p=0.004). No increase in serious adverse events was reported with active treatment (RR 0.91, 0.69-1.12; p=0.50) but 3-month mortality was halved (9.7%vs 20.3%, hazard ratio [HR] 0.40, 95% CI 0.2-1.0; p=0.05).

INTERPRETATION

Labetalol and lisinopril are effective antihypertensive drugs in acute stroke that do not increase serious adverse events. Early lowering of blood pressure with lisinopril and labetalol after acute stroke seems to be a promising approach to reduce mortality and potential disability. However, in view of the small sample size, care must be taken when these results are interpreted and further evaluation in larger trials is needed.

Dexmedetomidine as an anaesthetic adjuvant in patients undergoing intracranial tumour surgery: a double-blind, randomized and placebo-controlled study †

BACKGROUND

Dexmedetomidine (DEX) has been shown to provide good perioperative haemodynamic stability with decreased intraoperative opioid requirements. It may have neural protective effects, and thus may be a suitable anaesthetic adjuvant to neurosurgical anaesthesia.

METHODS

Fifty-four patients scheduled for elective surgery of supratentorial brain tumour were randomized to receive in a double-blind manner a continuous DEX infusion (plasma target concentration 0.2 or 0.4 ng ml(-1)) or placebo, beginning 20 min before anaesthesia and continuing until the start of skin closure. The DEX groups received fentanyl 2 microg kg(-1) at the induction of anaesthesia and before the start of operation, the placebo group 4 microg kg(-1), respectively. Anaesthesia was maintained with nitrous oxide in oxygen and isoflurane.

RESULTS

The median times from the termination of N2O to extubation were 6 (3-27), 3 (0-20) and 4 (0-13) min in placebo, DEX-0.2 and DEX-0.4 groups, respectively (P<0.05 anova all-over effect). The median percentage of time points when systolic blood pressure was within more or less than 20% of the intraoperative mean was 72, 77 and 85, respectively (P<0.01), DEX-0.4 group differed significantly from the other groups. DEX blunted the tachycardic response to intubation (P<0.01) and the hypertensive response to extubation (P<0.01). DEX-0.4 group differed in the heart rate variability from placebo (93 vs 82%, P<0.01).

CONCLUSIONS

DEX increased perioperative haemodynamic stability in patients undergoing brain tumour surgery. Compared with fentanyl, the trachea was extubated [corrected] faster without respiratory depression.

No difference in emergence time and early cognitive function between sevoflurane-fentanyl and propofol-remifentanil in patients undergoing craniotomy for supratentorial intracranial surgery

Balanced anesthesia with sevoflurane-fentanyl has been widely accepted as anesthetic management for neurosurgery. Propofol-remifentanil regimen has been successfully used in various surgical settings, but a comprehensive comparison of sevoflurane-fentanyl and propofol-remifentanil anesthesia in patients undergoing craniotomy for supratentorial intracranial surgery has not yet been done. The aim of this prospective, randomized, open-label clinical trial was to compare clinical properties of sevoflurane-fentanyl with propofol-remifentanil anesthesia in patients undergoing supratentorial intracranial surgery. The primary endpoint was to compare early postoperative recovery and cognitive functions within the two groups; we also evaluated hemodynamic events, vomiting, shivering, and pain. One hundred twenty patients (64 males; age 15-75 years) were randomized to either total intravenous anesthesia (group T) or sevoflurane anesthesia (group S). Emergence and extubation times and cognitive function (Short Orientation Memory Concentration Test [SOMCT]) were compared in the two groups. Brain swelling, incidence of hypotensive and hypertensive episodes, postoperative vomiting, shivering, and pain were also analyzed. The mean emergence time (12.2 +/- 4.9 minutes for group S versus 12.3 +/- 6.1 minutes for group T; P = 0.92) and extubation time (18.2 +/- 2.3 minutes for group S versus 18.3 +/- 2.1 minutes for group T; P = 0.80) were similar in the two groups. Average SOMCT scores, both 15 minutes after extubation (25.6 +/- 4.9 in group S versus 23.9 +/- 7.5 in group T; P = 0.14) and 45 minutes after extubation (27.3 +/- 2.2 in group S versus 26.0 +/- 5.1 in group T; P = 0.07) were also comparable. Brain swelling was present in seven and five patients in groups S and T, respectively (P = 0.76). Hypotension was present in 12% (group S) and 28% (group T) of patients (P = 0.02). Hypertension was present in 17% of patients in group S and 40% of patients in group T (P = 0.0046). Shivering was present in 18% and 25% of patients in groups T and S (P = 0.37). Our study demonstrates that there is no patient benefit of using total intravenous anesthesia with an ultra-short-acting opioid over the conventional balanced volatile technique in terms of recovery and cognitive functions.

CHHIPS (Controlling Hypertension and Hypotension Immediately Post-Stroke) Pilot Trial: rationale and design

RATIONALE

High and low blood pressure (BP) levels are common following acute stroke, with up to 60% of patients being hypertensive (SBP > 160 mmHg) and nearly 20% having relative hypotension (SBP < or = 140 mmHg), within the first few hours of ictus, both conditions being associated with an adverse prognosis. At present, the optimum management of blood pressure in the immediate post-stroke period is unclear.

OBJECTIVE

The primary aim of the Controlling Hypertension and Hypotension Immediately Post-Stroke (CHHIPS) Pilot Trial is to assess whether hypertension and relative hypotension, manipulated therapeutically in the first 24 h following acute stroke, affects short-term outcome measures.

DESIGN

The CHHIPS Pilot Trial is a UK based multi-centre, randomized, double-blind, placebo-controlled, titrated dose trial.

SETTING

Acute stroke and medical units in teaching and district general hospitals, in the UK.

PATIENTS

The CHHIPS Pilot Study aims to recruit 2050 patients, with clinically suspected stroke, confirmed by brain imaging, who have no compelling indication or contraindication for BP manipulation.

STUDY OUTCOMES

The primary outcome measure will be the effects of acute pressor therapy (initiated < or = 12 h from stroke onset) or depressor therapy (started < or = 24 h post-ictus) on death and dependency at 14 days post-stroke. Secondary outcome measures will include the influence of therapy on early neurological deterioration, the effectiveness of treatment in manipulating BP levels, the influence of time to treatment and stroke type on response and a cost-effectiveness analysis.

Effect of upper airway obstruction on blood pressure variability after stroke

Approx. 60% of acute stroke patients have periods of significant UAO (upper airway obstruction) and this is associated with a worse outcome. UAO is associated with repeated fluctuation in BP (blood pressure) and increased BP variability is also associated with a poor outcome in patients with acute stroke. UAO-induced changes in BP, at a time when regional cerebral perfusion is pressure-dependent in areas of critically ischaemic brain, could explain the detrimental effect of UAO on outcome in these patients. The aim of the present study was to examine the relationship between UAO and BP variability in patients with acute stroke. Twelve acute stroke patients and 12 age-, sex- and BMI (body mass index)-matched controls underwent a sleep study with non-invasive continuous monitoring of BP to assess the impact of UAO on BP control after stroke. Stroke patients had significantly more 15 mmHg dips in BP/h than the controls (51 compared with 6.7 respectively; P<0.004). Stroke patients also demonstrated significantly higher BP variability than the controls (26.8 compared with 14.4 mmHg; P<0.001). There were significantly more 15 mmHg dips in BP/h in stroke patients who had significant UAO than those who did not (85.7 compared with 29.5 respectively; P<0.032). Furthermore, stroke patients without UAO (RDI <10, where RDI is respiratory disturbance index) had significantly more 15 mmHg dips in BP/h than the controls (29.5 compared with 6.7 respectively; P<0.037). There was a positive correlation between the severity of UAO (RDI) and 15 mmHg dips in BP/h (r=0.574, P<0.005) in stroke patients. Our results suggest that UAO alone does not explain BP variation post-stroke, but it does play an important role, particularly in determining the severity of the BP fluctuation.

Effect of upper airway obstruction in acute stroke on functional outcome at 6 months

BACKGROUND

The aim of this study was to determine whether upper airway obstruction occurring within the first 24 hours of stroke onset has an effect on outcome following stroke at 6 months. Traditional definitions used for obstructive sleep apnoea (OSA) are arbitrary and may not apply in the acute stroke setting, so a further aim of the study was to redefine respiratory events and to assess their impact on outcome.

METHODS

120 patients with acute stroke underwent a sleep study within 24 hours of onset to determine the severity of upper airway obstruction (respiratory disturbance index, RDI-total study). Stroke severity (Scandinavian Stroke Scale, SSS) and disability (Barthel score) were also recorded. Each patient was subsequently followed up at 6 months to determine morbidity and mortality.

RESULTS

Death was independently associated with SSS (OR (95% CI) 0.92 (0.88 to 0.95), p<0.00001) and RDI-total study (OR (95% CI) 1.07 (1.03 to 1.12), p<0.01). The Barthel index was independently predicted by SSS (p = 0.0001; r = 0.259; 95% CI 0.191 to 0.327) and minimum oxygen saturation during the night (p = 0.037; r = 0.16; 95% CI 0.006 to 0.184). The mean length of the respiratory event most significantly associated with death at 6 months was 15 seconds (sensitivity 0.625, specificity 0.525) using ROC curve analysis.

CONCLUSION

The severity of upper airway obstruction appears to be associated with a worse functional outcome following stroke, increasing the likelihood of death and dependency. Longer respiratory events appear to have a greater effect. These data suggest that long term outcome might be improved by reducing upper airway obstruction in acute stroke.

Post-emergency department management of stroke

All stroke patients ideally should be admitted to a stroke unit in which personnel are familiar with strategies for taking care of stroke patients. Prevention of worsening cerebral ischemia by appropriate blood pressure and serum glucose management, fever control, and supplemental oxygen for hypoxemic patients is recommended. Recognition of common complications, such as aspiration pneumonia and deep venous thrombosis, highlights the need for swallowing evaluation and the use of pneumatic compression devices or subcutaneous heparin. Patients should be monitored closely for deterioration in their neurologic status and should have complications appropriately addressed. After evaluation of stroke etiology, appropriate secondary stroke prophylaxis should be selected and initiated before hospital discharge.

Steal affecting the central nervous system

Steal is a pathophysiological process in which increased blood flow through a low-resistance vascular bed is sufficient to divert flow away from a region of the central nervous system. Three disease states in which steal may cause neurological deficits due to central nervous system ischemia are reviewed. Subclavian steal occurs when stenosis of the subclavian artery proximal to the vertebral origin causes retrograde flow in the left vertebral artery. Patients with anatomic subclavian steal usually do not develop neurological symptoms but may rarely present with posterior circulation ischemia. Arteriovenous malformations alter cerebral blood flow patterns and regional perfusion pressure. It has been hypothesized that cerebral arteriovenous malformations may cause neurological deficits due to steal and that these deficits may be cured with arteriovenous malformation treatment. Intra-arterial pressure measurements and transcranial velocity studies show regional hemodynamic alterations. However, these changes have not been correlated with presenting symptoms. Evidence from single-photon emission computed tomography does suggest a relationship between regional hypoperfusion and neurological deficits. Coarctation of the aorta may divert flow from the spinal cord circulation through intercostal arteries distal to the stenosis. This is a possible but unproven mechanism of myelopathology. Steal syndromes may be amenable to treatment by open surgical or endovascular approaches. Experimental studies of the pathophysiology of steal are strengthened by precise definitions of the measured parameters and innovative applications of technology.

Twenty-four hour systolic blood pressure predicts long-term mortality following acute stroke

OBJECTIVE

To assess the effects of acute blood pressure (BP) on long-term mortality following stroke.

DESIGN

Prospective observational study.

SETTING

Leicester Teaching Hospitals.

PATIENTS

Two hundred and nineteen consecutive patients were recruited within 24 h of acute stroke.

INTERVENTIONS

Clinic and 24 h BP levels were measured. Other risk factors previously associated with stroke mortality were recorded within 24 h of admission. No specific pharmacological interventions;were made.

MAIN OUTCOME MEASURES

The primary outcome measure was death over a median follow-up period of over 2.5 years. The hazards ratios associated with predefined variables were assessed using Cox's proportional hazards modelling, and Kaplan-Meier survival plots were also calculated.

RESULTS

On multiple variable analysis, 24 h systolic BP (> or = 160 mmHg) was associated with an increased hazards ratio of 2.41 (95% confidence intervals: 1.24-4.67) for death, compared to the reference group (140-159 mmHg). The addition of 24 h heart rate was significant, with increasing heart rate (> 83 bpm) associated with an increased mortality (P = 0.006), although this effect was not constant over time. Increasing age (> 80 years) at presentation was also associated with an increased hazards ratio of 2.53 (1.14-5.62) compared to age < or = 66 years.

CONCLUSIONS

This study provides evidence that elevated 24 h systolic BP in the acute stroke period is associated with increased long-term mortality. This may have implications in the therapeutic management of BP following stroke, though further research is required to determine the timing, nature and effect of such an intervention.

Hypertension in patients presenting with stroke

Hypertension is a major risk factor for stroke disease. There is now some international agreement on what constitutes hypertension, and at what level of blood pressure treatment is required. Large randomised controlled trials demonstrate the benefit of reducing blood pressure for the primary and secondary prevention of stroke disease. Studies have also demonstrated the benefit of particular classes of antihypertensive agents in certain patient groups. Research is beginning to elucidate the problems of hypertension in the acute phase of ischaemic stroke and the therapeutic strategies that may be helpful. Given the significant impact of stroke disease on all health services, it remains an important priority to determine the best management of hypertension in stroke.

Intensive care unit management of the stroke patient

Although the majority of patients with acute stroke do not require intensive care, it is important to recognize when admission to an intensive care unit (ICU) is warranted. Patients undergoing thrombolytic therapy, those with brainstem infarcts referable to the basilar artery, those with large space occupying hemispheric infarcts, and those with fluctuating neurological examinations should be admitted to the ICU for monitoring and treatment.

Impaired cerebral autoregulation 24 h after induction of transient unilateral focal ischaemia in the rat

Cerebral blood flow (CBF) and cerebral autoregulation have been investigated 24 h after transient focal ischaemia in the rat. Cerebral blood flow was measured autoradiographically before and during a moderate hypotensive challenge, to test autoregulatory responses, using two CBF tracers, (99m)Tc-d,l-hexamethylproyleneamine oxide and 14C-iodoantipyrine. Prior to induced hypotension, CBF was significantly reduced within areas of infarction; cortex (28 +/- 20 compared with 109 +/- 23 mL/100 g/min contralateral to ischaemic focus, P = 0.001) and caudate (57 +/- 31 compared with 141 +/- 32 mL/100 g/min contralaterally, P = 0.005). The hypotensive challenge (mean arterial pressure reduced to 60 mmHg by increasing halothane concentration) did not compromise grey matter autoregulation in the contralateral hemisphere; CBF data were not significantly different at normotension and during hypotension. However, in the ipsilateral hemisphere, a significant volume of cortex adjacent to the infarct, which exhibited normal flow at normotension, became oligaemic during the hypotensive challenge (e.g. frontal parietal cortex 109 +/- 15% to 65 +/- 15% of cerebellar flow, P < 0.01). This resulted in a 2.5-fold increase in the volume of cortex which fell below 50% cerebellar flow (39 +/- 34 to 97 +/- 46 mm3, P = 0.003). Moderate hypotension induced a significant reduction in CBF in both ipsilateral and contralateral subcortical white matter (P < 0.01). In peri-infarct caudate tissue, CBF was not significantly affected by hypotension. In conclusion, a significant volume of histologically normal cortex within the middle cerebral artery territory was found to have essentially normal levels of CBF but impaired autoregulatory function at 24 h post-ischaemia.

Delayed hypovolemic hypotension exacerbates the hemodynamic and histopathologic consequences of thromboembolic stroke in rats

Abnormalities in cerebrovascular reactivity or hemodynamic reserve are risk factors for stroke. The authors determined whether hemodynamic reserve is reduced in an experimental model of thromboembolic stroke. Nonocclusive common carotid artery thrombosis (CCAT) was produced in rats by a rose bengal-mediated photochemical insult, and moderate hypotension (60 mm Hg/30 min) was induced 1 hour later by hemorrhage. Alterations in local cerebral blood flow (ICBF) were assessed immediately after the hypotensive period by 14C-iodoantipyrine autoradiography, and histopathologic outcome was determined 3 days after CCAT. Compared to normotensive CCAT rats (n = 5), induced hypotension after CCAT (n = 7) led to enlarged regions of severe ischemia (i.e., mean ICBF < 0.24 mL/g/min) in the ipsilateral hemisphere. For example, induced hypotension increased the volume of severely ischemic sites from 16 +/- 4 mm3 (mean +/- SD) to 126 +/- 99 mm3 (P < 0.05). Histopathologic data also showed a larger volume of ischemic damage with secondary hypotension (n = 7) compared to normotension (22 +/- 15 mm3 versus 5 +/- 5 mm3, P < .05). Both hypotension-induced decreases in ICBF and ischemic pathology were commonly detected within cortical anterior and posterior borderzone areas and within the ipsilateral striatum and hippocampus. In contrast to CCAT, mechanical ligation of the common carotid artery plus hypotension (n = 8) did not produce significant histopathologic damage. Nonocclusive CCAT with secondary hypotension therefore predisposes the post-thrombotic brain to hemodynamic stress and structural damage.

The effect of reperfusion therapy on cerebral blood flow in acute stroke

The effect of reperfusion therapy on cerebral blood flow (CBF) in acute cerebral ischemia was studied using xenon-enhanced computed tomography (XeCT). The XeCT CBF studies of 10 patients were evaluated before and after thrombolytic therapy. CBF evidence of reperfusion was evaluated in relation to the angiographic results and the clinical outcomes. Six patients had occlusions of the middle cerebral artery and four of the internal carotid artery. The mean CBF of the ischemic areas before attempted reperfusion was 9 +/- 3 mL/100g/min compared with 34 +/- 9 mL/100g/min in the contralateral asymptomatic region (P<.001). Intra-arterial-thrombolysis was performed in nine patients, and in one patient the intravenous route was used. Reperfusion of the ischemic region was shown in 9 of 10 patients, both angiographically and with the XeCT CBF studies (the mean CBF increased from 9 +/- 3 mL/100g/min to 32 +/- 10 mL/100g/min, P<.001). Among the nine successfully reperfused patients, seven were neurologically improved, one was unchanged, and one died. The mean National Institutes of Health stroke scale in the eight reperfused survivors was 12 on admission and decreased to 6 on discharge. XeCT CBF measurements are correlated with the angiographic results and can assist in the understanding of the effects of thrombolytic therapy on CBF in acute stroke. Re-establishment of CBF is associated with an improved clinical outcome but exceptions can be found. Reperfusion can occur in ischemic brain regions even with very low CBF (approaching 0 mL/100g/min) although it is not associated with prevention of infarction.

Management of hypertension in acute intracerebral hemorrhage

Hypertension commonly occurs in the acute period following spontaneous intracerebral hemorrhage. Management of this hypertension is controversial. Some advocate lowering blood pressure to reduce the risk of bleeding, edema formation, and systemic hypertensive complications, whereas others advocate allowing blood pressure to run its natural course as a protective measure against cerebral ischemia. This article reviews the pertinent clinical and experimental data regarding these issues and briefly discusses the use of antihypertensive agents commonly administered in this setting.

Vertebrobasilar thrombosis: diagnosis, management, and the use of intra-arterial thrombolytics

OBJECTIVES

To review the diagnosis and management of vertebrobasilar thrombosis and to discuss the use of thrombolytics in the treatment of this disease.

DATA SOURCES

Selected references discussing epidemiology, anatomy, pathophysiology, diagnosis, therapy, and rehabilitation of vertebrobasilar occlusive disease.

STUDY SELECTION

Studies addressing acute intervention and outcome in the therapy of vertebrobasilar thrombosis were reviewed.

DATA EXTRACTION

Only those studies with angiographic documentation of arterial thrombosis and, in the case of thrombolysis, recanalization, were considered valid.

DATA SYNTHESIS

Thrombosis of the vertebrobasilar system is a highly fatal disease and should be treated as a neurologic emergency. The key to effective management depends on early recognition of the symptom complex and a thorough understanding of the anatomy and pathophysiology of the disease process.

CONCLUSIONS

A timely, integrated, multidisciplinary approach to the patient with vertebrobasilar thrombosis can improve outcome. The use of thrombolytics in the treatment of vertebrobasilar occlusion holds promise but the benefits have not yet been proven in a controlled, randomized study.

Postprandial and orthostatic cardiovascular changes after acute stroke

BACKGROUND AND PURPOSE

Large falls in blood pressure after meals have been demonstrated in fit and frail elderly subjects; these changes may be associated with an increased incidence of stroke. Postprandial falls in BP may be particularly deleterious after acute stroke, when normal baroreflex mechanisms and cerebral autoregulation are already impaired, resulting in stroke progression. Therefore, the postprandial hemodynamic responses to orthostasis were examined in nine acute stroke subjects and eight age-, sex-, and blood pressure-matched control subjects after an oral energy load.

METHODS

All subjects were studied on two occasions in a randomized, double-blind, crossover trial after administration of either oral glucose (1 g/kg body wt) or equivalent isovolumic, isosmotic xylose (0.83 g/kg). Measurements of blood pressure, pulse rate, and forearm blood flow were recorded for 30 minutes preprandially and 90 minutes postprandially. Hemodynamic responses to 60 degrees tilt, along with plasma glucose and insulin changes, were measured at baseline and at 30-minute intervals postprandially.

RESULTS

Supine mean arterial and diastolic blood pressures fell significantly after glucose but not xylose ingestion in control subjects (P < .03) but not stroke subjects, whereas supine pulse rate increased in stroke subjects (P < .04) only. No significant changes in forearm vascular resistance were recorded in either control or stroke subjects. After tilt, stroke subjects showed a fall in mean arterial pressure compared with control subjects preprandially (P = .03) and at 30 (P < .005) and 90 (P < .03) minutes postprandially, although no differences were observed between the xylose and glucose phases. Orthostatic tolerance was maintained in control subjects throughout both phases of the study. Pulse rate increased significantly to tilt at all time intervals in both groups, although there were no significant changes in forearm vascular resistance.

CONCLUSIONS

Acute stroke subjects are not at significantly greater risk of blood pressure falls in response to an oral energy load than age-, sex-, and blood pressure-matched control subjects. Unlike control subjects, the stroke group had an increased pulse-rate postprandially, which could result in a compensatory rise in cardiac output as a result of increased sympathetic nervous system activity in the poststroke period. Although orthostatic blood pressure control is impaired after acute stroke, these changes are unaffected by meals.

Cerebral ischemic attack caused by postprandial hypotension

BACKGROUND

Food ingestion sometimes induces systemic hypotension (postprandial hypotension). Although the possibility of stroke occurring postprandially has been suggested, no cases have been reported until now.

CASE DESCRIPTION

A 78-year-old man experienced repeated transient ischemic attacks after almost every ingestion of food and showed orthostatic and postprandial hypotension. An angiogram revealed occlusion of his left carotid artery and stenosis of his right middle cerebral artery.

CONCLUSIONS

Postprandial as well as orthostatic hypotension can be a risk factor for stroke in patients with severe occlusive cerebrovascular disease.

Acute hemispheric stroke: correlation between three-dimensional transcranial Doppler, MR-angiography, CT and clinical findings

We examined 50 ischemic stroke patients and 67 controls free of vascular disease, intra- or extracranial. We assessed all subjects clinically by neurological examination (quantified on the Canadian Neurological Scale or CNS), by three-dimensional transcranial Doppler sonography (TCD-3D) and by computed tomography (CT) within 24 h of the acute event, repeating CT 15 days later. 15 patients also underwent magnetic resonance angiography (MRA) and digital subtraction angiography (DSA). We used the following Doppler parameters: interhemispheric asymmetry index (AI), mean flow velocity (mV) and pulsatility index (PI) for the middle cerebral artery (MCA). The difference between patients and controls on analysis of the variance (ANOVA) in respect of AI was significant: F = 50.8, p < 0.0001. The CNS-AI correlation was equally valid: r = -0.56, p < 0.001. The CNS-CT correlation proved to be highly significant: r = -0.72, p < 0.0001. TCD-3D allowed quantitative evaluation of the hemodynamic changes and of the collateral blood supply and proved to be a sound method for the investigation of ischemic stroke, correlating well with the clinical findings, MRA and lesion size on CT.

Influence of erythrocyte aggregability and plasma fibrinogen concentration on CBF with aging

The influence of the rheological properties of the blood on cerebral perfusion is still unresolved. Data on normal subjects are lacking and difficulties arise regarding the effect of blood viscosity owing to its close relationship with hematocrit. For these reasons we have studied the relationship between two rheological hematocrit-independent parameters and CBF in normal subjects of various ages. 36 normal volunteers, aged 20-74, free from risk factors, have been studied. CBF was measured by the Xenon inhalation method. Erythrocyte aggregability was expressed as Mean Erythrocyte Aggregation Index (MEA). Plasma fibrinogen concentration was evaluated by the coagulative method in 26 subjects. No correlation was found between CBF and MEA or fibrinogen in the subjects under the age of 45. A significant negative correlation was found between CBF and MEA (p = 0.015) and between CBF and fibrinogen (p = 0.011) in the subjects over 45. These data show that cerebral perfusion is influenced by the rheological properties of the microcirulation only with aging. We suggest that a "rheological autoregulation" exists and that it works properly in youth, only to be lost with physiological aging. This finding can be of significance in the pathogenesis of cerebrovascular disease processes in humans.

Improved carotid hemodynamics with vertebral reconstruction

This study tests the hypothesis that vertebral artery reconstruction improves carotid distribution hemodynamics during carotid occlusion. Twelve patients with vertebrobasilar symptoms underwent either direct (9) or indirect (3) vertebral reconstruction. There were six proximal vertebral to common carotid reimplantations, one proximal carotid-vertebral bypass and two distal carotid-vertebral bypasses, all with saphenous vein. Three patients with carotid-subclavian or axillo-axillary bypasses performed for symptomatic vertebral steal were studied at the time of carotid endarterectomy. During temporary ipsilateral carotid occlusion, vertebral reconstruction increased carotid back pressure from 39.3 +/- 10.2 mmHg to 46.8 +/- 9.5 mmHg (p less than 0.0001), increased cerebral perfusion pressure from 33.4 +/- 10.8 mmHg to 41.0 +/- 9.1 mmHg (p less than 0.0001), decreased the carotid collateral resistance to cerebral vascular resistance ratio from 1.68 +/- 0.90 to 1.24 +/- 0.64 (p less than 0.001), and increased the ratio of carotid back pressure to mean systemic arterial pressure from 0.452 +/- 0.122 to 0.515 +/- 0.118 (p = 0.0005). These results are presumed due to increased posterior-to-anterior blood flow in the posterior communicating arteries. Direct or indirect vertebral reconstruction may be a consideration in patients with cerebral ischemic symptomatic and nonreconstructible carotid occlusive disease.

Three-dimensional transcranial Doppler in acute ischemic stroke in the territory of the middle cerebral artery: clinical and CT correlation

We studied 34 patients with acute ischemic stroke in the territory of the middle cerebral artery (MCA) by three-dimensional transcranial Doppler (TCD-3D). The parameters analyzed were: mean blood flow velocity, systolic and diastolic velocities; indices of pulsatility, hemisphere asymmetry and pulsatility transmission. Of the 34 patients 11 presented marked slowing of flow velocity in the MCA on the infarct side with an asymmetry index (AI) of over 40%, 8 patients with slightly reduced flow velocity in the MCA and an AI of 25-40%, 2 patients in whom there was indirect evidence of collateral circulations in the anterior cerebral artery distribution together with slowing of MCA flow; 5 patients had stenosis of the MCA, 9 patients showed no alterations of the Doppler parameters. The correlation between neurological symptom pattern and AI was significant (r = 0.76). Noninvasive, easy to perform, performable at once and reliable, TCD-3D is a great improvement on traditional transcranial Doppler and is especially useful in assessing the hemodynamics of the cerebral circulation in ischemic stroke.

Safety of hypercapnic challenge: cardiovascular and neurologic considerations

The hemodynamic, cerebrovascular, and neurologic effects of hypercapnia with 4% and 6% CO2 were retrospectively reviewed in 217 patients referred for regional CBF (rCBF) procedures. Inhalation of CO2 significantly increased rCBF, blood pressure, and pulse from baseline. The findings suggest a higher incidence of side effects with 6% CO2 concentration and an equivalent vasoreactivity to 4%. We recommend the use of 4% CO2 for hypercapnic stimulation, and present safety guidelines for its use.

Induced hypertension as an approach to treating acute cerebrovascular ischaemia: possibilities and limitations

As, after an stroke, the autoregulation of the cerebral vessels in the ischaemic region is disturbed to a high degree, it is, on principle, possible to improve the blood flow particularly in the zone surrounding the infarct (penumbra) by raising the systemic blood pressure. During a basic treatment with low-molecular dextrans (infukoll M40), 37 patients with an acute ischaemic cerebral stroke multiply underwent elevations in blood pressure up to systolic values of about 210 to 220 mmHg. A comparison with a control group (n = 44) who were treated with low-molecular dextrans revealed no differences in lethality on the 21st day after the stroke. However, a very good acute effect in terms of a short-term improvement was remarkable a result that is noteworthy also in future.

Autoregulation of cerebral blood flow in experimental focal brain ischemia

The relationship between systemic arterial pressure (SAP) and neocortical microcirculatory blood-flow (CBF) in areas of focal cerebral ischemia was studied in 15 spontaneously hypertensive rats (SHRs) anesthetized with halothane (0.5%). Ischemia was induced by ipsilateral middle cerebral artery/common carotid artery occlusion and CBF was monitored continuously in the ischemic territory using laser-Doppler flowmetry during manipulation of SAP with I-norepinephrine (hypertension) or nitroprusside (hypotension). In eight SHRs not subjected to focal ischemia, we demonstrated that 0.5% halothane and the surgical manipulations did not impair autoregulation. Autoregulation was partly preserved in ischemic brain tissue with a CBF of greater than 30% of preocclusion values. In areas where ischemic CBF was less than 30% of preocclusion values, autoregulation was completely lost. Changes in SAP had a greater influence on CBF in tissue areas where CBF ranged from 15 to 30% of baseline (9% change in CBF with each 10% change in SAP) than in areas where CBF was less than 15% of baseline (6% change in CBF with each 10% change in SAP). These findings demonstrate that the relationship between CBF and SAP in areas of focal ischemia is highly dependent on the severity of ischemia. Autoregulation is lost in a gradual manner until CBF falls below 30% of normal. In areas without autoregulation, the slope of the CBF/SAP relationship is inversely related to the degree of ischemia.

Acetazolamide effects on cerebral blood flow in acute reversible ischemia

Cerebral blood flow (CBF) was studied in 4 patients with acute reversible ischemia (RIND). To test the ischemic areas' vasoreactivity, CBF was measured by the Xenon-133 inhalation method, before and after acetazolamide injected intravenously. At the baseline CBF study, 3 patients presented hypoperfused areas while one patient had increased CBF over the affected hemisphere. The acetazolamide test, showed in this latter case a "steal phenomenon" while in the other 3 an increase of perfusion was evidenced, in areas of normal flow, as well as in areas with reduced flow. These results suggest that in the acute phase of patients with RIND, when brain regions of hypoperfusion and neurological signs are still present, the vasomotor response may be preserved.

Treatment of intraoperative hypertensive emergencies in patients with intracranial disease

In patients with neuropathologic processes leading to disturbed cerebrovascular autoregulation, sudden increases in arterial blood pressure may lead to a sudden elevation in cerebral blood flow and intracranial pressure. Therefore, sudden increases in arterial pressure should be assiduously avoided in the perioperative period. Hypertensive episodes may occur at any time during anesthesia, but are more likely to occur (1) during laryngoscopy and intubation, (2) at the time of skin incision, (3) at extubation, and (4) during awakening. In patients with cardiovascular disease, such hypertensive episodes may also cause deterioration of the cardiovascular situation. Catecholamines are the principal mediators of such intraoperative hypertensive reactions. There are 2 options available to the anesthesiologist: (1) attempt to suppress this response after it has occurred, or (2) prevent its occurrence at the outset. Treatment of hypertension often relies on agents that relax vascular smooth muscle. In patients with compromised intracranial compliance, however, cerebral vasodilation must be avoided because it leads to an increase in cerebral blood volume. This, in turn, may raise intracranial pressure and result either in herniation of brain contents or a decrease in cerebral perfusion pressure leading to brain ischemia. Different pharmacologic means of preventing or suppressing such intraoperative hypertensive reactions are reviewed. Many of the drugs reviewed resulted in adverse effects that could preclude their use in patients with reduced intracranial compliance. Alpha- and beta-adrenergic receptor blockers can safely be administered to such patients.

Improvement of cerebral blood flow following stereotactic surgery in patients with putaminal haemorrhage

Changes in cerebral blood flow (CBF) after CT guided stereotactic aspiration of putaminal haematoma were investigated in 13 patients with Xe-133 inhalation and single photon emission computed tomography. The interval from onset to operation ranged from 13 to 82 days (mean 30 days). The mean estimated haematoma volume ranged from 20 to 50 ml (mean 31.9 ml). The percentage of haematoma aspirated ranged from 75 to 98% (mean 86.8%). Postoperative CBF in two thirds of the patients was improved even though all cases were operated on in the subacute stage. Both the mean hemispheric and regional CBF in the anterior territory of the middle cerebral artery and in the region of the thalamus and basal ganglia in the affected hemisphere were increased postoperatively. Also in the nonaffected hemisphere, regional CBF in the region of the thalamus and basal ganglia was improved.

Noninvasive assessment of CO2-induced cerebral vasomotor response in normal individuals and patients with internal carotid artery occlusions

To evaluate the CO2-induced vasomotor reactivity of the cerebral vasculature, relative changes of blood flow velocity within the middle cerebral artery were measured by transcranial Doppler ultrasonography during normocapnia and various degrees of hypercapnia and hypocapnia. We studied 40 normal individuals and 40 patients with unilateral and 15 patients with bilateral internal carotid artery occlusions. When blood flow velocity changes as percent of normocapnic values were plotted against end-tidal CO2 volume percent, a biasymptotic curve (a tangent-hyperbolic function) gave the best fit of the scattergram. The distance between the upper and lower asymptotes was defined as cerebral vasomotor reactivity. In the normal individuals, mean +/- SD vasomotor reactivity was 85.63 +/- 15.96%. In patients with internal carotid artery occlusions, vasomotor reactivity was significantly lower than normal on both the occluded (mean 45.2%, median 50.4%; p less than 0.0001) and the nonoccluded (mean +/- SD 67.7 + 13.3%, p less than 0.01) sides in the unilateral group and on both sides (mean +/- SD 36.6 +/- 15.9% and 44.9 +/- 24.6%, p less than 0.0001) in the bilateral group. The difference between vasomotor reactivity for symptomatic and asymptomatic unilateral occlusions was also highly significant (mean 37.6% and 62.9%, p less than 0.006). Vasomotor reactivity was also significantly lower in patients with low-flow infarctions on computed tomography than in patients with normal scans (mean +/- SD 36.7 +/- 25% and 60.2 +/- 16.9%, p less than 0.008). A striking association of low-flow infarctions, ischemic ophthalmopathy, and hypostatic transient ischemic attacks was found with vasomotor reactivities of less than 34% or even paradoxical reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilateral hemispheric reduction of cerebral blood volume and blood flow immediately after experimental cerebral hemorrhage in cats

Acute cerebral circulatory changes following experimental cerebral hemorrhage were investigated in eight cats. The cerebral hemorrhage was produced in the right basal ganglia by introducing arterial blood via a thin catheter, using the systemic arterial blood pressure of the cat as a driving force. Local cerebral blood volume was measured continuously in the bilateral parietotemporal cortexes employing photoelectric apparatuses. Carbon black dilution curves were recorded from the regions, and the mean transit time of blood was calculated. Local cerebral blood flow was estimated from mean transit time and cerebral blood volume. Intracranial pressure was monitored continuously in the right parietal epidural space. Five minutes after cerebral hemorrhage, intracranial pressure increased by 24.0 +/- 6.1 mm Hg, while mean arterial blood pressure increased by only 2.9 +/- 2.0 mm Hg. Cerebral blood volume decreased by 1.60 +/- 0.24 vol% in the hemorrhagic and 1.14 +/- 0.30 vol% in the nonhemorrhagic hemisphere. Cerebral blood flow decreased by 30.0 +/- 4.5 ml/100 g brain/min in the hemorrhagic (initially 64.5 +/- 13.6) and by 30.3 +/- 7.5 ml/100 g brain/min in the nonhemorrhagic (initially 60.9 +/- 6.9) hemisphere. Increased intracranial pressure appeared to be the main cause of the observed cerebral blood volume/flow reduction shortly after experimental hemorrhage in the basal ganglia. Several other factors and mechanisms involved are discussed.

Changes in cerebral blood flow pattern after carotid endarterectomy

A comparison was made between pre- and postoperative cerebral blood flow measurements in 20 patients who underwent endarterectomy. Most patients showed no difference between both studies. However in 4 of the series an increase in blood flow was observed while in another 4 patients a decrease occurred. Especially patients with a low preoperative flow seemed to have profited from the endarterectomy.

Ischemic cortical lesions after permanent occlusion of individual middle cerebral artery branches in rats

Our study describes the anatomy of the middle cerebral artery (MCA) in 65 Sprague-Dawley rats and the spatial distribution of ischemic cortical lesions caused by occluding major MCA branches. The rats characteristically had at least two major MCA branches, frontal and parietal. Many rats had additional branches supplying the pyriform and temporal cortexes. Permanent occlusion of the frontal or parietal branches combined with 30 minutes of bilateral carotid artery occlusion produced visible Evans blue dye uptake by ischemic cortical areas after 24 hours. No lesions distal to the occlusion were apparent in 38% and 43% of rats with frontal and parietal branch occlusions, respectively; small lesions contiguous with the occlusion site were observed in 38% and 32% of the rats. Only 6% of the frontal and 7% of the parietal branch occlusions produced isolated distal infarcts as expected if these branches were end-arteries. Blood flow was reversed in arteries distal to the occlusion. We conclude that extensive collateral connections of the frontal and parietal MCA branches with other arterial systems protect the anterior and posterior cortical regions. In contrast, occlusions of the pyriform branch of the MCA invariably caused infarcts in the frontopyriform region. In about one third of the rats, frontal or parietal branch occlusions produced lesions involving much of the proximal MCA territory; the frontopyriform region was most consistently affected. Combined, these data suggest that the pyriform MCA branch is an end-artery and that the cortical region it supplies is prone to ischemic damage resulting from any reduction of blood flow through the main MCA trunk.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral hemispheric and contralateral cerebellar hypoperfusion during a transient ischemic attack

We studied a 79-year-old woman within 3 h of the onset of a motor aphasia and a right hemiparesis. Single photon emission computed tomography (SPECT) showed a 24% decrease in the perfusion of the left middle cerebral artery territory and a 16% reduction in the perfusion of the right cerebellum. A mild naming difficulty was the neurological deficit at the end of the SPECT examination, and complete recovery was achieved within 24 h. Repeated SPECT study 10 days later was normal. This is the first report of focal hemispheric and contralateral cerebellar hypoperfusion in transient cerebral ischemia.

Can raising cerebral blood flow improve outcome after acute cerebral infarction?

Cerebral blood flow correlates poorly with outcome after stroke, and most therapies aimed at increasing cerebral perfusion have not succeeded in predictably reducing neurological deficit. Newer approaches such as hemodilution and thrombolysis may prove to be more effective but might be most advantageous if combined with efforts to correct postischemic disturbances in cellular metabolism.

Physostigmine induced reversal of ischemia following acute middle cerebral artery occlusion in the rat

Cerebral cortical ischemia was induced in anesthetized rats by occlusion of the middle cerebral artery (MCA). Cerebral blood flow (CBF) was measured with the H2 clearance technique in the center and periphery of the ischemic territory. A decrease of CBF to about 50% of pre-occlusion values was observed in both areas. Administration of Physostigmine, a cholinesterase inhibitor, at a dose of 0.15 mg/Kg by intravenous route, induced an increase of CBF in the ischemic cortex. This change in CBF reached 120% of pre-occlusion level in the periphery and 80% of pre-occlusion value in the center of the area of distribution of the occluded artery. Although Physostigmine induced an increase in arterial blood pressure, the cerebral hyperemia observed both in normal and ischemic cortex could still be demonstrated after blockade of the pressor effect by bleeding or Phentolamine administration.

Regional cerebral blood flow after occlusion of the middle cerebral artery

Occlusions of the middle cerebral artery (MCA) are mostly of embolic origin (appr. 80%) and give rise to about one third of all ischemic strokes, most of these being major strokes. MCA occlusions lasting for less than 1/2 h are tolerated without occurrence of permanent tissue damage. Occlusions lasting between 1/2 h to 4-8 h lead to permanent tissue damage and neurological deficits that are proportional to the duration of occlusion. Maximal tissue damage is obtained after 4-8 h occlusion. A cerebral blood flow of 8-23 ml/100 gr/min is sufficient for cellular viability but insufficient for normal tissue function ("ischemic penumbra"). Cellular function is completely abolished in the interval 8-16 ml/100 gr/min and flow at that level is tolerated only for 1-3 h before neuronal death ensues. In the interval 18-23 ml/100 gr/min there is some functional activity although it is reduced. Experimental and clinical evidence suggests that flow in this interval may be tolerated for several days, months or even longer ("chronic ischemic penumbra"). After MCA occlusion the blood flow falls below 8 ml/100 gr/min in most cases and permanent MCA occlusion always leads to relatively large areas of frank infarction. The ischemic infarcts may be surrounded by collaterally perfused areas where the blood flow is pressure-dependent (impaired autoregulation) and quite commonly insufficient for normal neuronal function (below 23 ml/100 gr/min). Such collaterally perfused areas may include a "chronic ischemic penumbra". Emboli causing MCA occlusions commonly disintegrate and/or migrate more peripherally within the first few weeks post stroke. This leads to reperfusion and changes of ischemic infarcts into hyperemic infarcts where flow is severely increased. The vascular reactivity is completely abolished in hyperemic infarcts and the hyperemic state lasts for about two weeks. Probably, anemic infarcts are equivalent to ischemic infarcts while the hemorrhagic variety is equivalent to hyperemic infarcts. The "partial infarct" with selective neuronal necrosis occurs in experimental animals after MCA occlusions of less than four h but not after permanent MCA occlusion. The significance of partial infarction in human stroke is not clarified. The extent of irreversible tissue damage can be reduced only if therapy sets in within 4-8 h after the occlusion. If a "chronic penumbra" exists the extension of reversible tissue damage can be reduced if therapy aimed at increasing the blood flow in the penumbra sets in within weeks or even months after the stroke.(ABSTRACT TRUNCATED AT 400 WORDS)

Photochemically induced cortical infarction in the rat. 1. Time course of hemodynamic consequences

Alterations in local CBF (LCBF) were assessed autoradiographically in the rat at several time points following photochemically induced cortical infarction. Cortical infarction of consistent size and location was produced by irradiating the brain with green light through the intact skull for 20 min following the systemic injection of rose bengal. A consistent pattern of altered LCBF was recorded in both ipsilateral and contralateral brain regions over the course of the study. At 30 min, a severely ischemic zone surrounded by regions of cortical hyperemia was apparent. LCBF was also depressed relative to control values in ipsilateral cortical regions remote from the irradiated area, while contralateral cortical structures were mildly hyperemic. By 4 h, the zone of severe ischemia had enlarged and its margins were no longer hyperemic. Ipsilateral cortical and some subcortical structures demonstrated significantly depressed levels of LCBF. At 5 days, LCBF throughout both ipsilateral and contralateral cortices was depressed compared with control values. By 15 days, LCBF had returned to control levels in most brain structures shown histopathologically not to be irreversibly damaged. The temporal sequence and magnitude of these hemodynamic alterations are consistent with findings in clinical studies in which repeated measurements of CBF have been carried out in patients with acute stroke. The ability to produce a cortical infarct that results in a consistent pattern of altered CBF should facilitate the investigation of stroke mechanisms responsible for these hemodynamic abnormalities.