Middle Cerebral Artery Transcranial Doppler Research Articles

Exploring Cerebral Perfusion Transcranial Doppler Parameters in Patients Admitted to Combined Medical Surgical Intensive Care Unit

Introduction: Encephalopathy, a common complication in Intensive Care Unit (ICU) patients, is often linked to poor outcomes. Transcranial Doppler (TCD), a non-invasive tool assesses cerebral perfusion via the Pulsatility Index (PI), Resistivity Index (RI), and Time-Averaged Peak (TAP) or Mean Flow Velocity (MFV). These parameters may offer insights into cerebral perfusion and outcomes in encephalopathic patients. Aim: To describe the PI, RI of the Middle Cerebral Artery (MCA), and MFV or TAP measured by TCD in patients admitted to the ICU, comparing those with and without encephalopathy at the time of admission. Materials And Methods: This cross-sectional observational study was conducted from January 2019 to November 2020, in a combined medical-surgical ICU of a tertiary care hospital, involving 45 enrolled patients. Patients were evaluated within 24 hours of admission and subsequently every 24 hours until ICU discharge, death, or discharge against medical advice. Bilateral Middle cerebral artery TCD studies were conducted using a 1-5 MHz phased array probe or TCD mode through the transtemporal window. The PI, RI, and MFV were measured on both sides, with the higher value used for analysis, and all statistical analyses were performed using Statistics and Data 13 software. Results: In the present study, 88% (n=40) of patients had encephalopathy (GCS<15 and RAAS less than or more than 0). The mean APACHE II score was 19 (14-25), indicating severe illness with a predicted mortality of 30-40%. Patients with encephalopathy had significantly higher APACHE II scores compared to those without (19.5 (16-25) vs 10 (4-19)). Although there was a trend towards a higher Pulsatility Index in encephalopathic patients at admission (1.11±0.378 vs 1.07±0.12, p=0.81), PI, RI, and TAP values did not significantly differ in non-survivors (1.12±0.49 vs 1.11±0.33, p=0.750). Persistent encephalopathy was associated with a trend towards higher PI at admission (1.05±0.24 vs 1.16±0.46; p=0.756), and a moderate correlation was found between decreasing PI and improvement in GCS (rho=-0.489, p=0.001). Conclusions: PI, RI, and TAP at the time of admission were not found to be associated with occurrence and recovery of encephalopathy as well as mortality. The trend of change in PI moderately correlated with improvement in GCS suggesting the importance of trends rather than absolute values.

Transcranial Doppler Sonography in Children with Congenital Heart Disease Undergoing Cardiac Catheterization

Background Children with congenital heart disease (CHD) are at high risk for neurodevelopmental disabilities. Acute neurologic complications, such as seizures, transient ischemic attack, intracranial hemorrhage, and ischemic stroke might occur in the setting of cardiac surgery and cardiac catheterization. Cardiac catheterization is important in the diagnosis and assessment of hemodynamic function in children with congenital heart disease. The incidence of neurologic complications (occurring within 48 hours) in interventional cardiac catheterization is significantly higher than those in diagnostic. Objective The Aim of this study is to evaluate the effect of cardiac catheterization on TCD Commented [RM1]: transcranial doppler (TCD) in children with congenital heart disease. Methods This is a prospective study. 40 children were enrolled; at Children’s hospital, Ain Shams University over 6 months. TCD parameters, clinical data, neurologic examination were done before and after cardiac catheterization. Results In the present study, 33 patients (82.5%) had interventional catheter and 7 (17.5%) had diagnostic catheter. Middle cerebral artery TCD parameters of the patients in the diagnostic group showed lower peak systolic (PS), and time average mean of the maximal velocities (TAMX), also called mean velocity, before catheterization and lower PS, end diastolic (ED), and TAMX post catheterization. All patients showed statistically significant lower TAMX post catheterization. Conclusion Cardiac catheterization lower middle cerebral artery time average mean of the maximal velocities in children with congenital heart disease. This impairment in blood flow might be a risk for cerebrovascular diseases in this population.

Vascular function in women: when studying perimenopause is peri important.

Vascular function in women: when studying perimenopause is peri important.

Effect of Progesterone Therapy in Traumatic Subarachinoid Haemorrhage on Clinical Outcome, Resistive Vasculer Indices of Middle Cerebral Artery Transcranial Doppler and Thromboelastometry. A Promising Layout

Effect of Progesterone Therapy in Traumatic Subarachinoid Haemorrhage on Clinical Outcome, Resistive Vasculer Indices of Middle Cerebral Artery Transcranial Doppler and Thromboelastometry. A Promising Layout

Cerebrovascular Risk in Restless Legs Syndrome: Intima-Media Thickness and Cerebral Vasomotor Reactivity: A Case-Control Study.

PurposeAlthough some studies have suggested an association between cardiovascular disease and restless legs syndrome (RLS), the mechanisms underlying this relationship remain unclear. The intima-media thickness (IMT) and vasomotor reactivity are two simple, non-invasive tools to investigate preclinical atherosclerosis and microangiopathy, respectively. The aims of this study were to evaluate carotid IMT and to explore vasomotor reactivity in idiopathic RLS (iRLS) patients.Patients and MethodsWe enrolled 44 iRLS after exclusion of patients with secondary causes of RLS, history of vascular events, known uncontrolled vascular risk factors and other neurological disorders. Forty-four age and sex matched controls were therefore recruited. No significant differences in demographic data and vascular risk factors were found between the two groups. Carotid IMT was measured with a high-resolution B-mode ultrasound on the far-wall of common carotid artery, 10 mm and 30 mm to the carotid bulb. Vasomotor reactivity to hypo- and hypercapnia was assessed, by right middle cerebral artery transcranial Doppler, accordingly to the changes in peak systolic velocity, peak diastolic velocity and mean blood flow velocity.ResultsMean IMT was significantly increased in patients with iRLS when measured immediately proximally to carotid bifurcation (0.73; sd=0.17), versus controls (0.65; sd=0.13); p=0.035. Patients showed higher cerebrovascular flow velocities (CBFVs) compared to controls. After multivariate analysis, age, hypertension and iRLS proved to be independent IMT predictors.ConclusionIncreased IMT and higher CBFVs in iRLS support the association of iRLS with vascular damage, possibly through enhanced atherogenesis and sympathetic hyperactivity. However, to clarify a causal relationship, further longitudinal assessment of these parameters is needed, trying to control all their physiological modifying factors.

Neuropathophysiology of preeclampsia and eclampsia: A review of cerebral hemodynamic principles in hypertensive disorders of pregnancy.

Preeclampsia and eclampsia are hypertensive disorders of pregnancy associated with abnormal placental vascular development. The systemic angiogenic imbalance, endothelial dysfunction and proinflammatory state caused by abnormal placental development results in abnormalities in renal, hepatic, pulmonary and neurologic function. Neurosensory symptoms related to pregnancy induced hypertension (PIH), the most devastating of which are intracranial hemorrhage and seizure, are among the leading causes of maternal and perinatal morbidity and mortality globally, yet risk stratification strategies and targeted therapies remain elusive. Current treatment for preeclampsia with severe features is limited to delivery, antihypertensive therapy, and magnesium sulfate seizure prophylaxis. Magnesium sulfate reduces seizure rates among severe preeclamptics, but predisposes patients to weakness, uterine atony, pulmonary edema and respiratory depression. Therefore, this drug should ideally be administered only to the subset of preeclamptics who are at increased risk for neurologic complications. While there are no objective methods validated to predict eclampsia, we hypothesize that measurement of optic nerve sheath diameters, optic disc height and middle cerebral artery transcranial doppler resistance indices may be useful in identifying subclinical cerebral edema, potentially allowing us to recognize those patients at highest risk for seizures. This summary of the current literature provides an initial framework for developing more sophisticated and noninvasive methods for identifying, monitoring and treating parturients who are at highest risk for neurologic complications from preeclampsia.

The age‐related reduction in cerebral blood flow affects vertebral artery more than internal carotid artery blood flow

Ageing reduces cerebral blood flow (CBF), while mean arterial pressure (MAP) becomes elevated. According to 'the selfish brain' hypothesis of hypertension, a reduction in vertebral artery blood flow (VA) leads to increased sympathetic activity and thus increases MAP. In twenty-two young (24±3years; mean±SD) and eleven elderly (70±5years) normotensive men, duplex ultrasound evaluated whether the age-related reduction in CBF affects VA more than internal carotid artery (ICA) blood flow. Pulse-contour analysis evaluated MAP while near-infrared spectroscopy determined frontal lobe oxygenation and transcranial Doppler middle cerebral artery mean blood velocity (MCA Vmean ). During supine rest, MAP (90±13 versus 78±9mmHg; P<0·001) was elevated in the older subjects while their frontal lobe oxygenation (68±7% versus 77±7%; P<0·001), MCA Vmean (49±9 versus 60±12cm s-1 ; P=0·016) and CBF (754±112 versus 900±144mlmin-1 ; P=0·004) were low reflected in VA (138±48 versus 219±50mlmin-1 ; P<0·001) rather than in ICA flow (616±96 versus 680±120mlmin-1 ; P=0·099). In conclusion, blood supply to the brain and its oxygenation are affected by ageing and the age-related decline in VA flow appears to be four times as large as that in ICA and could be important for the age-related increase in MAP.

Abstract TMP88: Prevalence of Right-to-left Cardiac Shunt in the Greek Population is High and Impacts on the Interpretation of the Risk of Paradoxical Embolism (RoPE) Score

Introduction: The RoPE score calculates the probability that patent foramen ovale (PFO) is causally related to stroke (PFO attributable fraction, PFO-af), based on PFO prevalence in patients with cryptogenic stroke compared with that in control subjects. The latter has been estimated at 25%; however, PFO prevalence in nonselected populations varies widely. Since PFO prevalence in Greeks remains unknown, we aimed to define it and to calculate PFO-af stratified by RoPE score in a cohort of patients with embolic stroke of undetermined source (ESUS). Methods: Right-to-left cardiac shunt (RLS) was detected according to the international consensus criteria in healthy subjects (H, n=115, women=65) and patients with ESUS (n=84, women=42) ≤55 years old. Each subject underwent unilateral middle cerebral artery transcranial Doppler (TCD) recording (Sonaratek, Natus) with a 2-MHz probe after infusion of agitated saline, at rest and after a controlled Valsalva maneuver. We characterized RLS as large (&gt;20 microbubbles or curtain), moderate (10&lt;x≤20) and minimal (≤10). Statistical comparisons were performed using the Fisher’s exact test. We dichotomized patients with ESUS and PFO into high (&gt;median) and low (≤median) RoPE score groups and calculated the corresponding PFO-af. Results: RLS was detected in 43.5% (50/115) of H and 50% (42/84) of ESUS. Large RLS tended to occur more often in ESUS compared to H [29.8% (25/84)] vs 18.3% (21/115); p=0.06]. The RoPE score median in patients with ESUS and RLS was 8 (interquartile range: 7,9). Patients with high RoPE score (9-10) had PFO-af of 64.4 whereas patients with low score (0-8) had PFO-af of 4.4. For any individual stratum up to RopE score 6, the PFO-af was null. Conclusions: The prevalence of RLS in Greeks is quite higher than the average used by the RoPE study. Despite a 50% chance of having RLS of any size, patients with ESUS have large RLS at least 60% more often than the general population. We suggest that optimal calculation of the PFO-af corresponding to RoPE score strata relies on the accurate estimation of PFO prevalence in national/ethnic populations. The proposed RoPE score cutoff of &gt;6 for having a probable PFO-related stroke may overestimate the probability in patients deriving from populations with high RLS prevalence.

A13661 Cerebral circulation and cognitive functions in arterial hypertension, optimization of diagnosis and treatment

Objectives: To investigate cerebral circulation in controlled arterial hypertension patients 2 stage of working age with mild and moderate cognitive disorders (CD), to determine the effectiveness of fixed combination of nootropic agent (phenibutum) and anticholinergic drug (ipidacrinum). Methods: Observed 67 patients with controlled hypertension 2 stage and CD. The median age − 57,3 ± 8,91 years. The average duration of hypertension was 11,5 ± 6,2 years. Cognitive functioning was assessed by MoCA scale. Blood flow in the middle cerebral artery (MCA) was studied by transcranial Doppler (TCD) on the HDI 7, Philips, USA with functional respiratory hypo- and hypercapnic ventilation tests to assess the integrative index of vasomotor reactivity: IVMR = [(Vapnea–Vhyper)/V0]•100%,Vapnea – the average maximum velocity of blood flow after 20 s of apnea (cm/s), Vhyper – the average maximum velocity of blood flow after 20 s of hyperventilation (cm/s), V0 — the average maximum velocity at rest (cm/s)). All patients received a personalized antihypertensive therapy and were randomized in two groups; 30 of the main group of treatment were added fixed combination of phenibutum 300 mg and ipidacrinum 5 mg x 3 times a day. Timing of treatment and surveillance was 45 days. Results: Only the patients of the main group decreased CD by 2.39 ± 0.75 points according to data MoCA scale on the base of improvements of cerebral blood flow. As to the data of TCD MCA monitoring of respiratory tests during involvement time a significant improvement of IVMR by 22%, (p > 0,05) in that group were achieved. Conclusion: Functional respiratory tests can be used for control the early brain damage. Additional prescription of fixed combination of nootropic agent and anticholinergic drug is adequate for correction cognitive disorders in hypertension patients.

23. Role of trans-cranial Doppler in children with acute liver failure – A prospective observational pilot study

Background and Aims: Early detection of raised intracranial pressure improves outcome in acute liver failure (ALF). We evaluated role of bedside transcranial doppler (TCD) in ALF children for feasibility, correlation with severity of hepatic encephalopathy (HE) and predicting outcome. Methods: 28 ALF children [24 boys, 11 (5–18 years)] with HE (grade I–II = 9, III–IV = 19) and 47 healthy controls [30 boys, 11 (5–18 years)] were prospectively enrolled. Demographic, clinical and laboratory parameters were recorded. Expert radiologist performed TCD of middle cerebral artery (MCA) with 2 MHz probe through temporal window. Peak systolic velocity (Vs), end diastolic velocity (Vd), mean flow velocity (mFV), pulsatility (PI) and resistive index (RI) were calculated by electronic calipers. PI ≥ 1.2 was suggestive of raised ICP. Results: TCD could be performed in all patients and healthy controls except one with poor window. TCD parameters in controls and ALF with grade I–II HE and III–IV HE are shown in Table 1. The peak systolic velocity, PI and RI showed an increasing trend from controls to HE grade I–II to grade III–IV (Table 1). ALF children with HE grade III–IV had significantly higher peak systolic velocity, PI and RI as compared to controls. However, the difference in peak systolic velocity, PI and RI in ALF patients with HE grade I-II versus controls and ALF with HE I-II versus III-IV was not statistically significant. ALF children with PI ≥ 1.2 (n = 7) more often had severe grade (III-IV) of HE (7/7 vs. 12/21; p = 0.03) and poorer outcome (0/7 vs. 8/21 survival without transplantation; p = 0.05) than those with PI < 1.2 (n = 21). Conclusions: Transcranial doppler is feasible in ALF children. The PI, RI and peak systolic velocity of MCA are higher in ALF with grade III-IV HE then controls but they do not differentiate between grades of HE. PI ≥ 1.2 is a predictor of poor outcome. The authors have none to declare.

Support Vector Machine Based Monitoring of Cardio-Cerebrovascular Reserve during Simulated Hemorrhage.

Introduction: In the initial phase of hypovolemic shock, mean blood pressure (BP) is maintained by sympathetically mediated vasoconstriction rendering BP monitoring insensitive to detect blood loss early. Late detection can result in reduced tissue oxygenation and eventually cellular death. We hypothesized that a machine learning algorithm that interprets currently used and new hemodynamic parameters could facilitate in the detection of impending hypovolemic shock.Method: In 42 (27 female) young [mean (sd): 24 (4) years], healthy subjects central blood volume (CBV) was progressively reduced by application of −50 mmHg lower body negative pressure until the onset of pre-syncope. A support vector machine was trained to classify samples into normovolemia (class 0), initial phase of CBV reduction (class 1) or advanced CBV reduction (class 2). Nine models making use of different features were computed to compare sensitivity and specificity of different non-invasive hemodynamic derived signals. Model features included: volumetric hemodynamic parameters (stroke volume and cardiac output), BP curve dynamics, near-infrared spectroscopy determined cortical brain oxygenation, end-tidal carbon dioxide pressure, thoracic bio-impedance, and middle cerebral artery transcranial Doppler (TCD) blood flow velocity. Model performance was tested by quantifying the predictions with three methods: sensitivity and specificity, absolute error, and quantification of the log odds ratio of class 2 vs. class 0 probability estimates.Results: The combination with maximal sensitivity and specificity for classes 1 and 2 was found for the model comprising volumetric features (class 1: 0.73–0.98 and class 2: 0.56–0.96). Overall lowest model error was found for the models comprising TCD curve hemodynamics. Using probability estimates the best combination of sensitivity for class 1 (0.67) and specificity (0.87) was found for the model that contained the TCD cerebral blood flow velocity derived pulse height. The highest combination for class 2 was found for the model with the volumetric features (0.72 and 0.91).Conclusion: The most sensitive models for the detection of advanced CBV reduction comprised data that describe features from volumetric parameters and from cerebral blood flow velocity hemodynamics. In a validated model of hemorrhage in humans these parameters provide the best indication of the progression of central hypovolemia.

Lessons from altitude: cerebral perfusion insights and their potential translational clinical significance

What is the topic of this review? The long-held assumption that transcranial Doppler middle cerebral artery velocity is a surrogate for cerebral blood flow has been questioned in certain circumstances, particularly where tissue oxygenation changes. What advances does it highlight? Cerebral venous outflow restriction appears to be implicated in the development of high-altitude cerebral oedema. Rapid ascent to high altitude commonly results in acute mountain sickness and, on occasion, potentially fatal high-altitude cerebral oedema. The exact pathophysiological mechanisms behind these syndromes remain to be determined. One of the main theories to explain the development of acute mountain sickness is an increase in intracranial pressure. Vasogenic (extracellular water accumulation attributable to increased permeability of the blood-brain barrier) and cytotoxic (intracellular) oedema have also been postulated as potential mechanisms that underlie high-altitude cerebral oedema. Recently published findings derived from a very challenging field study (obtained at altitudes of up to 7950m), substantiated by sea-level hypoxic magnetic resonance angiography studies, have given new insights into the maintenance of cerebral blood flow at altitude. This report provides new perspectives and potential mechanisms to account for the maintenance of cerebral oxygen delivery at high and extreme altitude. In particular, the long-held assumption that transcranial Doppler middle cerebral artery velocity is a surrogate for cerebral blood flow has been shown to be incorrect in certain circumstances. The emerging evidence for a potential third mechanism, namely the restrictive venous outflow hypothesis, in the development of high-altitude cerebral oedema, over and above the accepted vasogenic and cytotoxic hypotheses, is also appraised.

Magnetic resonance imaging/angiography and transcranial Doppler velocities in sickle cell anemia: results from the SWiTCH trial

AbstractThe Stroke With Transfusions Changing to Hydroxyurea (SWiTCH) trial compared standard (transfusions/chelation) to alternative (hydroxyurea/phlebotomy) treatment to prevent recurrent stroke and manage iron overload in children chronically transfused over 7 years before enrollment. Standardized brain magnetic resonance imaging/magnetic resonance angiography (MRA) and transcranial Doppler (TCD) exams were performed at entry and exit, with a central blinded review. A novel MRA vasculopathy grading scale demonstrated frequent severe baseline left/right vessel stenosis (53%/41% ≥Grade 4); 31% had no vessel stenosis on either side. Baseline parenchymal injury was prevalent (85%/79% subcortical, 53%/37% cortical, 50%/35% subcortical and cortical). Most children had low or uninterpretable baseline middle cerebral artery TCD velocities, which were associated with worse stenoses (incidence risk ratio [IRR] = 5.1, P ≤ .0001 and IRR = 4.1, P < .0001) than normal velocities; only 2% to 12% had any conditional/abnormal velocity. Patients with adjudicated stroke (7) and transient ischemic attacks (19 in 11 standard/8 alternative arm subjects) had substantial parenchymal injury/vessel stenosis. At exit, 1 child (alternative arm) had a new silent infarct, and another had worse stenosis. SWiTCH neuroimaging data document severe parenchymal and vascular abnormalities in children with SCA and stroke and support concerns about chronic transfusions lacking effectiveness for preventing progressive cerebrovascular injury. The novel SWiTCH vasculopathy grading scale warrants validation testing and consideration for use in future clinical trials. This trial was registered at www.clinicaltrials.gov as #NCT00122980.

Cerebro vascular reactivity (CVR) of middle cerebral artery in response to CO25% inhalation in preeclamptic women

Objective: To compare the cerebro vascular reactivity (CVR) of middle cerebral artery (MCA) in response to CO25% inhalation between preeclamptic and normotensive pregnant women, also, between mild and severe preeclampsia.Study design: A comparative study was performed on 61 women with preeclampsia and 65 normotensive pregnant women who were in the third trimester of gestation. MCA transcranial Doppler ultrasound was used to measure CVR in response to CO25% inhalation. Pulsatility index (PI), resistance index (RI), blood pressure, maternal age, gestational age and gravidity were also recorded.Results: Baseline PI and RI were lower in the preeclamptic group (p < 0.05). Inhalation of CO25% caused significant increase in CVR among normotensive pregnant women in comparison with preeclamptic group (1.006 ± 0.229 versus 0.503 ± 0.209, p = 0.0001). Significantly, more cerebral vasodilatation was found among mild preeclamptic women in comparison with severe preeclamptic women (0.583 ± 0.193 versus 0.383 ± 0.173, p = 0.0001). The receiver operating characteristics curve analysis revealed acceptable difference between CO2 stimulation test of preeclamptic and normotensive women (Area under curve = 0.973, p = 0.0001).Conclusion: CVR in response to CO25% is less in preeclamptic pregnant women than normotensives, also, in severe preeclampsia, it is less than mild preeclampsia.

Validation of Transcranial Doppler with Magnetic Resonance Angiography in Acute Cerebral Ischemia

Transcranial Doppler (TCD) is often used as a screening tool for detecting intracranial stenosis. Since TCD results may vary among laboratories and sonographers, it requires validation against an imaging modality. We evaluated diagnostic accuracy of TCD performed in our laboratory against time-of-flight (TOF) magnetic resonance angiography (MRA) in detecting intracranial stenosis in patients with acute cerebral ischemia. Consecutive patients with acute (<24 hours) cerebral ischemia and intracranial arterial stenosis on MRA underwent both TCD and MRA within 5 hours of each other. TCD was performed by credentialed neurosonologists according to standardized protocol. An independent neuroradiologist interpreting MRA was blinded to TCD findings. We evaluated TCD peak systolic velocities (PSV) in proximal intracranial arteries as predictive of moderate (>50%) and severe (>70%) stenosis on TOF-MRA. One hundred and fifty patients (74% males; mean age 53 years) underwent neurovascular evaluation with TCD and MRA. Twenty-two (14.6%) patients were excluded due to absent temporal acoustic windows. Middle cerebral artery TCD PSV values of >140 cm/s and >180 cm/s were found to predict a >50% and >70% focal stenosis, respectively. Optimal cut-off PSV values for other major proximal intracranial arteries were also established. TCD performed in our laboratory shows satisfactory agreement with TOF-MRA in diagnosis and grading of proximal intracranial stenosis in patients with acute cerebral ischemia.

The effects of sevoflurane on cerebral blood flow autoregulation and flow-metabolism coupling during cardiopulmonary bypass

previous studies on non-cardiac surgical patients have shown that cerebral pressure-flow autoregulation and cerebral flow-metabolism coupling are maintained with sevoflurane. The effects of sevoflurane on cerebral blood flow (CBF) autoregulation and flow-metabolism coupling during cardiopulmonary bypass (CPB) have not been studied previously. the effects of sevoflurane-induced burst suppression, monitored with electroencephalography (EEG), on cerebral blood flow velocity (CBFV), cerebral oxygen extraction (COE) and flow autoregulation, were studied in 16 patients undergoing cardiac surgery. The experimental procedure was performed during non-pulsatile CPB with mild hypothermia (34 degreesC) in fentanyl/droperidol-anesthetized patients. Middle cerebral artery transcranial Doppler flow velocity, right jugular vein bulb oxygen saturation and jugular venous pressure were measured continuously. Autoregulation was tested during changes in the mean arterial pressure (40-90 mmHg), induced by sodium nitroprusside and norepinephrine before (control), and during additional sevoflurane administration, in a dose that resulted in an EEG burst-suppression level of 4-6/min. sevoflurane, at an inspired concentration of 3.36 ± 0.03%, induced a 17% decrease in CBFV (P<0.05) and a 22% decrease in COE (P<0.05) compared with the control. The slope of the positive relationship between CBFV and cerebral perfusion pressure was steeper with sevoflurane (p<0.01) compared with control measurements, as was the slope of the negative relationship between cpp and coe (p<0.01). burst-suppression doses of sevoflurane exert an intrinsic cerebral vasodilatory effect, which impairs CBF autoregulation during mildly hypothermic CPB. Furthermore, during sevoflurane administration, CBF is in excess relative to oxygen demand, indicating a partial loss of the cerebral flow-metabolism coupling.

Lateralization of cerebral blood flow in juvenile absence seizures

Cerebrovascular blood flow in absence seizures and flow patterns during the ictal period have not been thoroughly investigated. We aimed to evaluate cerebral blood flow changes in typical juvenile absence seizures during the ictal and postictal phases. Seizures were recorded in three patients (mean age: 21 +/- 1 years) with multiple daily typical absence seizures. Simultaneous video electroencephalography and bilateral middle cerebral artery transcranial Doppler ultrasonography recordings were conducted during seizures. Basal, ictal, and postictal blood flow velocities were recorded bilaterally, and offline analyses were performed in relation with generalized spike and wave discharges. Total of 43 seizures were recorded. Ictal increase and postictal decrease of cerebral blood flow velocities were significant for both sides (P < 0.001). The interhemispheric asymmetry in the ictal velocity increase was significant (P < 0.05). The interhemispheric asymmetry in the postictal velocity decrease was not significant (P > 0.05). The blood flow velocity increase after seizure onset indicates a vascular coupling mechanism. A sudden and then a gradual decrease in blood flow velocity, which lasted even after the seizure ceased, might suggest a preventive mechanism to avoid excessive seizure duration or even an absence status epilepticus. Significant asymmetries in increase and a symmetrical decrease may support the cortical focus theory.

Foam sclerotherapy: cardiac and cerebral monitoring

To investigate and review collected and reported transcutaneous ultrasound, transthoracic echocardiography (TTE) and transcranial Doppler (TCD) data obtained during ultrasound-guided foam sclerotherapy (USGFS) of incompetent saphenous, tributary and perforating veins of the lower extremities. TTE and/or middle cerebral artery TCD were performed during USGFS. Ultrasound (US) findings and adverse events were recorded. Existing literature was reviewed. Ultrasound detected emboli circulating in superficial, perforating, communicating and deep veins and into the central circulation. TTE detected bright echoes in the right heart after every injection and in the left heart in up to 65% of selected patients. TCD high-intensity transient signals (HITS) were detected in 14-42% of the patients. Incidence of HITS was higher than patient reports of adverse events. Incidence of HITS was independent of foam volumes injected. Echogenic signals were detected in non-treated veins, in heart chambers and in the cerebral circulation by transcutaneous US, TTE and TCD. Pathological consequences of such findings remain to be investigated.

The Effects of Hypocapnia and the Cerebral Autoregulatory Response on Cerebrovascular Resistance and Apparent Zero Flow Pressure During Isoflurane Anesthesia

Simultaneous recordings of arterial blood pressure (ABP) and middle cerebral artery blood velocity can be used to calculate the apparent zero flow pressure (aZFP). The inverse of the slope of the pressure-velocity relationship is known as resistance area product (RAP) and is an index of cerebrovascular resistance. There is little information available regarding the effects of vasoactive drugs, arterial carbon dioxide (Paco(2)), and impaired cerebral autoregulation on aZFP and RAP during general anesthesia. During isoflurane anesthesia, we investigated the effects of hypocapnia and the effects of a phenylephrine infusion, on aZFP and RAP. Radial ABP and transcranial Doppler middle cerebral artery blood velocity signals were recorded in 11 adults undergoing isoflurane anesthesia. A phenylephrine infusion was used to increase ABP and ventilation was adjusted to control Paco(2). Cerebral hemodynamic variables were compared at two levels of mean ABP (approximately 80 and 100 mm Hg) and at two levels of Paco(2): normocapnia (Paco(2) 38-43 mm Hg) and hypocapnia (Paco(2) 27-34 mm Hg). Two aZFP analysis methods were compared: one based on linear regression and one based on Fourier analysis of the waveforms. At the lower ABP, aZFP was 23 +/- 11 mm Hg and 30 +/- 13 mm Hg (mean +/- sd) with normocapnia and hypocapnia, respectively (P < 0.001) and RAP was 0.76 +/- 0.97 mm Hg x s x cm(-1) and 1.16 +/- 0.16 mm Hg x s x cm(-1) with normocapnia and hypocapnia, respectively (P < 0.001). Similar effects of hypocapnia were seen at the higher ABP. With normocapnia, isoflurane impaired cerebral autoregulation and aZFP did not change with the increase in ABP. With hypocapnia, cerebral autoregulation was not significantly impaired and increasing ABP was associated with increased aZFP (from 30 +/- 13 to 35 +/- 13 mm Hg, P < 0.01) and increased RAP (from 1.16 +/- 0.16 to 1.52 +/- 0.20 mm Hg x s x cm(-1), P < 0.001). Calculation of the relative contributions of aZFP and RAP to the cerebral hemodynamic responses indicated that changes in RAP appeared to have a greater influence than changes in aZFP. The mean difference between the two methods of determining aZFP (Fourier-regression) was 0.5 +/- 3.6 mm Hg (mean +/- 2sd). During isoflurane anesthesia, two interventions that increase cerebral arteriolar tone, hypocapnia and the autoregulatory response to increasing ABP, were associated with increased RAP and increased aZFP. The effect of changes in RAP appeared to be quantitatively greater than the effects of changes in aZFP. These results imply that arteriolar tone influences cerebral blood flow by controlling both resistance and effective downstream pressure.

Dantrolene Mediates Vasorelaxation in Cerebral Vasoconstriction: A Case Series

Cerebral vasoconstriction syndromes such as vasospasm after subarachnoid hemorrhage (SAH) and trauma, or Call-Fleming syndrome are difficult to treat, and can lead to substantial disability and death. Dantrolene, a ryanodine receptor antagonist, inhibits intracellular calcium release from the sarco-endoplasmic reticulum. We examined the effect of dantrolene on middle cerebral artery (MCA) blood flow velocities as measured by transcranial Doppler (TCD). Three consecutive patients with elevated MCA TCD velocities receiving dantrolene (2.5 mg/kg i.v. q6h) were retrospectively reviewed. Average MCA peak systolic, mean flow velocities, and the pulsatility index (PI) before and after the dantrolene infusion were compared within patients. Systemic physiological parameters (blood pressure, heart rate, central venous pressure, intracranial pressure, body temperature, and cooling water temperature) were retrospectively collected 6 h before and after the dantrolene infusion. MCA peak systolic velocities (mean +/- SE) for the three patients were 297 +/- 3, 248 +/- 8, and 268 +/- 19 cm/s before dantrolene and 159 +/- 9, 169 +/- 8, and 216 +/- 12 cm/s after dantrolene. Average mean flow velocities showed the same trend. Interestingly, the PI increased slightly from 0.6, 0.52, and 0.67 before dantrolene, to 1.17, 0.71, and 0.77 after dantrolene. Systemic physiological parameters remained stable in all three patients. Dantrolene attenuated cerebral vasoconstriction as measured by TCD without altering systemic physiological parameters. This suggests that intracellular calcium release from ryanodine channels in smooth muscle might play a role in vasospasm. A prospective study is underway to test this hypothesis.