Correlation between hemodynamic characteristics or dynamic cerebral autoregulation and postoperative hyperperfusion in patients undergoing carotid endarterectomy / 中华超声影像学杂志

Objective:To investigate the hemodynamic characteristics and dynamic cerebral autoregulation(dCA) of patients with severe carotid stenosis before carotid endarterectomy(CEA), and to analyze their correlations with hyperperfusion after CEA.Methods:A total of 63 patients with unilateral severe carotid artery atherosclerotic stenosis who underwent CEA were consecutively recruited prospectively in Xuanwu Hospital, Capital Medical University from January 2021 to August 2021. According to postoperative hyperperfusion, patients were divided into hyperperfusion group (13 cases) and non-hyperperfusion group (50 cases). The general clinical data and hemodynamic parameters were compared between the two groups. The dCA was evaluated by the transfer function analysis that measured the fluctuation amplitude of mean cerebral blood flow velocity(CBFV) with blood pressure change, the time difference of phase with blood pressure change, and the correlation between mean CBFV and blood pressure change. The value of dCA for predicting postoperative hyperperfusion was analyzed through the ROC curve and the area under the curve(AUC).Results:①The proportion of hypertension in hyperperfusion group was higher than that in non-hyperperfusion group ( P<0.05). ②The peak systolic velocity (PSV) at the stenosis lesion of the internal carotid artery, the end-diastolic velocity (EDV) at the stenosis lesion of the internal carotid artery and the ratio of PSV at the stenosis lesion of the internal carotid artery to the distal internal carotid artery in the hyperperfusion group were higher than the non-hyperperfusion group.And the PSV of the ipsilateral middle cerebral artery in the hyperperfusion group was lower than the non-hyperperfusion group (all P<0.05). ③In the very low-frequency and low-frequency region, the phase in the hyperperfusion group was lower than that in the non-hyperperfusion group (all P<0.05), while there was no significant difference in the high-frequency regions( P>0.05). In the three regions of very low-frequency, low-frequency and high-frequency, there were no significant differences in the gain and coherence between the two groups(all P>0.05). ④The best cutoff value of phase in the very low-frequency was 33.28 for predicting hyperperfusion after CEA (AUC=0.766, 95% CI=0.629-0.904, P=0.03), with the specificity of 0.700, and sensitivity of 0.846. Conclusions:There are differences in hemodynamics and dCA between the hyperperfusion group and the non-hyperperfusion group after CEA. The impaired preoperative dynamic cerebral autoregulation is an independent predictor of postoperative hyperperfusion.

Cerebral Autoregulation in Patients with Unilateral Carotid Artery Stenosis / 中国医学科学院学报

To investigate cerebral autoregulation(CA)in patients with severe unilateral carotid artery stenosis by near infrared spectroscopy. Thirty patients who underwent general anesthesia in our hospital from January 2015 to February 2017 were enrolled in this study.The stenosis group included 15 patients with severe unilateral internal carotid artery stenosis,and the control group included 15 patients without carotid artery stenosis.Both groups were matched in sex and age.Cerebral tissue oxygenation index(TOI)and mean arterial pressure were recorded continuously under stable general anesthesia.The Pearson correlation coefficient()was calculated to judge the CA status. TOI was not significantly different between the stenosis side and the non-stenosis side in the stenosis group(66.52±6.50 65.23±4.50;=0.93, =0.368)or between the stenosis side in the stenosis group and the stenosis side in the control group(66.52±6.50 64.22±3.87;=1.18, =0.248).The values of stenosis side and non-stenosis side in the stenosis group were 0.36±0.12 and 0.17±0.11,respectively,and the values of the stenosis side in the stenosis group and the stenosis side of the control group were 0.36±0.12 and 0.13±0.08,respectively.In the stenosis group,5 patients had transient ischemic attack and 2 patients had a history of stroke within 3 months before operation.When an value of 0.342 was used as the judgment point of CA abnormality,the sensitivity and specificity were 0.625 and 0.909,respectively. Within the range of normal blood pressure fluctuation,cerebral blood flow is linked to blood pressure at the stenosis side in patients with severe unilateral carotid artery stenosis.

Head-up and body positioning might impair dynamic cerebral autoregulation in patients with silent cerebral small vessel disease. Protocol and operational definitions / El posicionamiento elevado de cabeza y cuerpo podrían afectar la autorregulación cerebral dinámica en pacientes con enfermedad silente de pequeño vaso cerebral. Protocolo y definiciones operacionales

ABSTRACT Background: Cerebral autoregulation (CA) is the ability of intracranial vessels to maintain a constant cerebral blood flow (CBF) during changes of cerebral perfusion pressure (CPP) related to fluctuations in blood pressure, postural changes or increased metabolic demands. It has been suggested that individuals with silent cerebral small vessel disease (SVD) may have impaired CA, but information is inconclusive. We describe the protocol of a study aimed to assess the association between white matter hyperintensities (WMH) of presumed vascular origin and poor dynamic CA, and to determine the effects of head-up and body positioning in patients with this condition. Methods: Using a case-control study design, we will assess the relationship between severity of WMH and dynamic CA, measured by continuous transcranial Doppler assessment of CBF velocities in the middle cerebral arteries (MCAs) combined with beat-to-beat blood pressure monitoring. Dynamic CA will be analyzed by calculating the mean flow index as the ratio of median arterial pressure and mean flow velocities of the MCAs. Participants will be categorized as case-patients if the MRI shows moderate-to-severe WMH. For every case-patient, an age- and sex-matched healthy individual with no neuroimaging evidence of SVD will be selected as a control. Comment: This study will assess whether head-up and body positioning impairs dynamic CA in the setting of diffuse subcortical damage related to SVD, providing further evidence on the importance of CPP in maintaining the CBF. If positive, the study will provide evidence favoring the stop of aggressive hypertensive therapy or interventions promoting orthostatic hypotension to reduce the risk of further ischemic brain damage in these cases.

RESUMEN Antecedentes: La autorregulación cerebral (CA) es la capacidad de los vasos cerebrales de mantener un flujo sanguíneo constante durante cambios en la presión de perfusión cerebral (PPC) relacionados con fluctuaciones de la presión arterial, cambios posturales o aumento de las demandas metabólicas. Se ha sugerido que las personas con enfermedad de pequeño vaso cerebral pueden tener CA deteriorada, pero la información no es concluyente. Describimos el protocolo de un estudio cuyo objetivo es evaluar la asociación entre hiperintensidades de substancia blanca y CA dinámica deficiente, para determinar los efectos del posicionamiento de cabeza y cuerpo en estos pacientes. Métodos: Utilizando un diseño de caso-control, evaluaremos la relación entre la severidad de las hiperintensidades de substancia blanca y la CA dinámica, mediante Doppler transcraneal continuo de las velocidades de flujo en las arterias cerebrales medias (ACM) combinadas con monitoreo de la presión arterial. La CA dinámica se analizará calculando el índice de flujo medio y la relación entre la presión arterial media y las velocidades medias de flujo de las ACM. Los participantes se clasificarán como casos si la IRM muestra hiperintensidades de substancia blanca. Para cada caso, se seleccionará a un individuo sin evidencia de enfermedad de pequeño vaso como control. Comentario: Este estudio evaluará si el posicionamiento de la cabeza hacia arriba afecta la CA dinámica en el contexto del daño subcortical difuso relacionado con enfermedad de pequeño vaso, proporcionando evidencia adicional sobre la importancia de la PPC en el mantenimiento del flujo en estos sujetos. El estudio proporcionará evidencia sobre el uso de terapia hipertensiva agresiva o intervenciones que promueven la hipotensión ortostática para reducir el riesgo de daño cerebral isquémico.

Application of near-infrared spectroscopy in monitoring in the neurocritical care unit / 中华神经科杂志

The field of monitoring in neurocritical care has long been lacking a non-invasive monitoring technique that can be real-time evaluated at the bedside. In recent years, near-infrared spectroscopy has drawn attention in neurocritical care. The feasibility of using this technique to monitor cerebral autoregulation, perfusion, oxygenation and intracranial pressure dynamically has been noticed. We reviewed the basic principle of near-infrared spectroscopy and its application in adult neurocritical care patients, and discussed the shortcomings of this technique. More clinical researches are needed in the future to evaluate this promising monitoring technology.

Cerebral Hemodynamics in Premature Infants

Extremely low birth weight infants remain at increased risk of intraventricular hemorrhage from the fragile vascular bed of the germinal matrix; the roles of hypotension (ischemia) and reperfusion (hyperemia) in the development of intraventricular hemorrhage are still debated. Cerebrovascular pressure autoregulation protects the brain by maintaining constant cerebral blood flow despite changes in blood pressure. The ontogeny of cerebrovascular pressure autoregulation has not been well established and uncertainty remains about the optimal arterial blood pressure required to support brain perfusion. Another important aspect of premature cerebral hemodynamics is the critical closing pressure––the arterial blood pressure at which cerebral blood flow ceases. Interestingly, in premature infants, the critical closing pressure approximates the mean arterial blood pressure. Often in this unique population, cerebral blood flow occurs only during systole when the diastolic arterial blood pressure is equal to the critical closing pressure. Moreover, the diastolic closing margin, a metric of cerebral perfusion that normalizes diastolic arterial blood pressure to the critical closing pressure, may be a better measure than arterial blood pressure for defining cerebral perfusion in premature infants. Elevated diastolic closing margin has been associated with intraventricular hemorrhage. This review summarizes the current state of understanding of cerebral hemodynamics in premature infants.

Effects of different surfactant administrations on cerebral autoregulation in preterm infants with respiratory distress syndrome / 华中科技大学学报（医学）（英德文版）

To treat respiratory distress syndrome, surfactant is currently delivered via less invasive surfactant administration (LISA) or INtubation SURfactant Extubation (INSURE). The aim of this study was to compare the effect of the two delivery methods of surfactant on cerebral autoregulation. Near infrared spectroscopy monitoring was carried out to detect cerebral oxygen saturation (ScO), and the mean arterial blood pressure (MABP) was simultaneously recorded. Of 44 preterm infants included, the surfactant was administrated to 22 via LISA and 22 via INSURE. The clinical characteristics, treatments and outcomes of the infants showed no significant differences between the two groups. The correlation coefficient of ScOand MABP (r) 5 min before administration was similar in the two groups. During surfactant administration, rincreased in both groups (0.44±0.10 to 0.54±0.12 in LISA, 0.45±0.11 to 0.69±0.09 in INSURE). In the first and second 5 min after instillation, rwas not significantly different from baseline in the LISA group, but increased in the first 5 min after instillation (0.59±0.13, P=0.000 compared with the baseline in the same group) and recovered in the second 5 min after instillation (0.48±0.10, P=0.321) in the INSURE group. There were significant differences in the change rates of rbetween the two groups during and after surfactant administration. Our results suggest that cerebral autoregulation may be affected transiently by surfactant administration. The effect duration of LISA is shorter than that of INSURE (<5 min in LISA vs. 5-10 min in INSURE).

Two levels of the inspired oxygen fraction in propofol-anesthetized dogs with high intracranial pressure: cardiopulmonary function / Dois níveis de fração inspirada de oxigênio em cães anestesiados com propofol e com pressão intracraniana elevada: função cardiopulmonar

In the initial stage of traumatic brain injury, the use of 1.0 inspired oxygen fraction (FiO2) is indicated. However, high FiO2 has been correlated with atelectasis. Thus, the effects of FiO2 = 1.0 and FiO2 = 0.6 on the cardiopulmonary function in propofol-anesthetized dogs with high intracranial pressure (ICP) were evaluated. Eight dogs were anesthetized on two occasions, receiving, during controlled ventilation, an FiO2 = 1 (G100) or an FiO2 = 0.6 (G60). Propofol was used for induction (10mg.kg-1) followed by a continuous rate infusion (0.6mg.kg-1.minute-1). An increase in the ICP was induced by temporary obliteration of the right jugular vein (OJv) 50 minutes after induction of anesthesia. The measurement was taken twenty minutes after OJv (T0) and then at 15-minute intervals (T15 to T60). Alveolar oxygen partial pressure in G60 was lower than in G100 during the whole procedure. Alveolar-arterial oxygen gradient in G100 was greater than in G60 at T0 and at T60. No differences were observed for arterial oxygen partial pressure/inspired oxygen fraction ratio, arterial-to-alveolar oxygen pressure ratio, respiratory index, venous admixture, oxygen delivery, oxygen consumption, oxygen extraction, heart rate, mean pulmonary arterial pressure, pulmonary arterial occlusion pressure, cardiac index, stroke index and systemic vascular resistance index. In G100, mean arterial pressure at T0 was higher than at T45. In dogs with high ICP, the cardiopulmonary function was not influenced by the different FiO2 used...

No estágio inicial do trauma encefálico, o emprego de fração inspirada de oxigênio (FiO2) de 1,0 é indicado. Todavia, altas FiO2 têm sido correlacionadas com atelectasia. Assim, avaliaram-se os efeitos das FiO2 = 1.0 e FiO2 = 0.6 sobre a função cardiopulmonar em cães com pressão intracraniana (PIC) elevada e anestesiados com propofol. Oito animais foram anestesiados em duas ocasiões e receberam, durante a ventilação controlada, FiO2 = 1(G100) ou FiO2 = 0,6 (G60). Propofol foi usado para indução (10mg.kg-1) e seguido por infusão contínua (0,6mg.kg-1minuto-1). O aumento da PIC foi induzido pela obliteração temporária da veia jugular (OJv). As mensurações foram realizadas 20 minutos após OJv (T0) e em intervalos de 15 minutos (de T15 a T60). A pressão parcial de oxigênio alveolar no G60 foi menor do que no G100 durante todo o procedimento. O gradiente alveolar-arterial no G100 foi maior do que no G60, em T0 e T60. Não foram observadas diferenças para: relação pressão parcial de oxigênio/fração inspirada de oxigênio, relação arterioalveolar, índice respiratório, mistura arteriovenosa, oferta de oxigênio, consumo de oxigênio, taxa de extração de oxigênio, frequência cardíaca, pressão da artéria pulmonar média, pressão de oclusão da artéria pulmonar, índice cardíaco, índice sistólico e índice de resistência vascular sistêmica. No G100, a pressão arterial média em T0 foi maior do que em T45. Em cães com alta PIC, a função cardiopulmonar não foi influenciada pelas diferentes FiO2 empregadas...

Cerebral hemodynamics: concepts of clinical importance / Hemodinâmica encefálica: conceitos de importância clínica

Cerebral hemodynamics and metabolism are frequently impaired in a wide range of neurological diseases, including traumatic brain injury and stroke, with several pathophysiological mechanisms of injury. The resultant uncoupling of cerebral blood flow and metabolism can trigger secondary brain lesions, particularly in early phases, consequently worsening the patient's outcome. Cerebral blood flow regulation is influenced by blood gas content, blood viscosity, body temperature, cardiac output, altitude, cerebrovascular autoregulation, and neurovascular coupling, mediated by chemical agents such as nitric oxide (NO), carbon monoxide (CO), eicosanoid products, oxygen-derived free radicals, endothelins, K+, H+, and adenosine. A better understanding of these factors is valuable for the management of neurocritical care patients. The assessment of both cerebral hemodynamics and metabolism in the acute phase of neurocritical care conditions may contribute to a more effective planning of therapeutic strategies for reducing secondary brain lesions. In this review, the authors have discussed concepts of cerebral hemodynamics, considering aspects of clinical importance.

Alterações hemodinâmicas e metabólicas do encéfalo ocorrem frequentemente em diversas doenças neurológicas, principalmente em condições de traumatismo cranioencefálico e acidente vascular encefálico, com vários mecanismos patofisiológicos lesionais. O desacoplamento resultante do fluxo sanguíneo e do metabolismo encefálico pode resultar em lesões encefálicas secundárias, principalmente nas primeiras fases, e, consequentemente, no agravamento do desfecho neurológico dos pacientes. Diversos fatores influenciam o fluxo sanguíneo encefálico, entre eles, a concentração sanguínea de gases, viscosidade sanguínea, temperatura corpórea, débito cardíaco, altitude, autorregulação cerebrovascular e acoplamento neurovascular, que é mediado por óxido nítrico (ON), monóxido de carbono (CO), eicosanoides, radicais livres derivados do oxigênio, endotelinas, potássio, íons hidrogênio e adenosinas. Melhor compreensão destes fatores é fundamental para o manejo clínico dos pacientes neurológicos críticos. A avaliação hemodinâmica e metabólica do encéfalo nas lesões encefálicas agudas pode contribuir para o planejamento de estratégias de redução das lesões encefálicas secundárias. Nesta revisão, os autores discutiram princípios da hemodinâmica encefálica, considerando os aspectos de importância clínica.

Intracranial variables in propofol or sevoflurane-anesthestized dogs subjected to subarachnoid administration of iohexol / Variáveis intracranianas em cães anestesiados com propofol ou sevofluorano e submetidos à administração subaracnóidea de iohexol

The effects of subarachnoid administration of iohexol on intracranial hemodynamic in dogs anesthetized with propofol or sevoflurane were evaluated. Thirty adult animals (10.9±2.9kg) were distributed into two groups: PG, where propofol was used for induction (10±0.5mg/kg), followed by a continuous rate infusion at 0.55±0.15mg/kg/hour, and SG, where sevoflurane was administered for induction (2.5 MAC) and for anesthetic maintenance (1.5 MAC). A fiberoptic catheter was implanted on the right superficial cerebral cortex to monitor intracranial pressure (ICP). After 30 minutes, cerebrospinal fluid (CSF) was collected at the cisterna magna and iohexol was injected. The measurements were performed before CSF collection (TA), after the iohexol injection (T0), and at 10-minute intervals (T10 to T60). Intracranial pressure decreased at T0 in SG. Cerebral perfusion pressure at T0 was higher than at TA, T50 and T60 in PG, but in SG, the mean value at T0 was higher than the ones from T20 to T60. Mean arterial pressure at T0 was higher than at TA in PG, while in SG, the values from T20 to T60 were lower than at T0. The heart rate at T60 was lower than at T0 in PG. Cardiac output at TA was lower than at T60 in SG. The cerebrospinal fluid collection and administration of iohexol promoted decrease in intracranial pressure in sevolflurane-anesthetized dogs and increase in cerebral perfusion pressure in propofol-anesthetized dogs.

Avaliaram-se os efeitos da administração subaracnóidea de iohexol sobre a hemodinâmica intracraniana em cães anestesiados com propofol ou sevofluorano. Trinta e dois animais (10,9±2,9kg) foram distribuídos em dois grupos: no GP, o propofol foi usado para indução, 10±0.5mg/kg, seguido por infusão contínua, 0,55±0,15mg/kg/min; no GS, o sevofluorano foi administrado para indução, 2,5 CAM, e manutenção, 1,5 CAM, da anestesia. O cateter de fibra óptica foi implantado na superfície direita do córtex cerebral para monitorar a pressão intracraniana (PIC). Após 30 minutos, o fluido cerebroespinhal (FCS) foi coletado da cisterna magna e o iohexol injetado. As mensurações ocorreram antes da coleta do FCS (TA), depois da injeção de iohexol (T0) e em intervalos de 10 minutos (T10 a T60). A pressão intracraniana diminuiu em T0 no GS. A pressão de perfusão cerebral em T0 foi maior que em TA, T50 e T60 no GP, mas no GS, a média em T0 foi maior que as de T20 a T60. A pressão arterial média em T0 foi maior que em TA no GP, enquanto no GS, de T20 a T60, as médias foram menores que em T0. A frequência cardíaca em T60 foi menor que em T0 no GP. O débito cardíaco em TA foi menor que em T60 no GS. A coleta do fluido cerebroespinhal e a administração do iohexol promoveram a diminuição da pressão intracranina em cães anestesiados com sevofluorano e aumento da pressão de perfusão cerebral em cães anestesiados com propofol.

Cardiovascular autonomic functions & cerebral autoregulation in patients with orthostatic hypotension.

Background & objectives: Patients of orthostatic hypotension may or may not have symptoms of the cerebral hypoperfusion despite fall in the blood pressure. The present study was done to quantify autonomic functions and cerebral autoregulation in patients of orthostatic hypotension with or without symptoms. Methods: The study was conducted in 15 patients of orthostatic hypotension and 15 age, sex matched control subjects. The sympathetic reactivity was measured by diastolic blood pressure response to handgrip test (ΔDBP in HGT) and cold pressor test (ΔDBP in CPT). The parasympathetic reactivity was measured by E:I ratio during deep breathing test (DBT) and Valsalva ratio (VR) during Valsalva maneuver. The cerebral autoregulation was computed from the changes in the cerebral blood flow, cerebrovascular conductance and blood pressure measured during different time points during head-up tilt (HUT). Results: The sympathetic reactivity was lower in patients as compared to controls [ΔDBP in HGT: 10 (4 - 16) vs 18 (12 - 22) mmHg, P<0.01; ΔDBP in CPT : 10 (4-12) vs 16 (10-20) mmHg, P<0.01]. The parasympathetic reactivity was also lower in patients as compared to controls. The sympathetic and parasympathetic reactivity was comparable in the symptomatic and asymptomatic patients. The maximum fall in blood pressure during HUT was comparable between symptomatic and asymptomatic patients (29.14 ± 10.94 vs 29.50 ± 6.39 mmHg), however, the percentage fall in the cerebral blood flow was significantly higher in the symptomatic (P<0.05) compared to asymptomatics. Interpretation & conclusions: Patients with orthostatic hypotension had deficits in sympathetic and parasympathetic control of cardiovascular system. Cerebral autoregulation was present in asymptomatic patients (increase in cerebrovascular conductance) during HUT while it was lost in symptomatic patients.

Simultaneously Measured CO2 Reactivity in the Basilar and Middle Cerebral Artery: The Utilization of Power M-mode Doppler and Anterior-posterior Probes Fixating Device

BACKGROUND: Studies using a transcranial Doppler (TCD) to establish cerebral vasoreactivity (CVR) have mostly focused on the anterior circulation. The purpose of this study is not only to evaluate the feasibility of the power motion mode Doppler (PMD) with a probes fixating device, but also to simultaneously measure the CVR between the middle cerebral artery (MCA) and the basilar artery (BA) during hypercapnea simulated by the rebreathing technique. METHODS: Twenty eight healthy volunteers were enrolled. Baseline hemodynamic values (heart rate, blood pressure) were measured while volunteers sat in a comfortable position for 5 minutes. The TCD was performed in two steps. First, velocities and spectra of the MCAs were simultaneously monitored. Then, the velocities and spectra of the MCA and BA were simultaneously monitored by a headset that included an anterior-posterior probes fixating device. The equation for CVR was ([maximum mean velocity baseline mean velocity] x 100/baseline mean velocity). RESULTS: Baseline mean velocities were revealed as follows: (64.0+/-13.7, 65.0+/-11.9 cm/s in right and left MCA; p>0.05; 67.3+/-12.2, -45.3+/-7.6 cm/s in dominant MCA and BA). CVR did not differ between the dominant MCA and the BA (46.1+/-12.1, 46.0+/-15.1%; p>0.05), nor between the right and left MCAs (46.9+/-15.2, 46.4+/-14.8%; p>0.05). There was a positive linear correlation between the CVR of the dominant MCA and that of the BA (r=0.856; p<0.001). CONCLUSIONS: PMD with a probes fixating device for accurate insonation is a useful tool for evaluating the relative CVR between the MCA and BA. Our study suggests that CVR values of the BA are similar to those of the MCA.

Altered cerebral vasomotion with decreased CGRP level in pial arteries of spontaneously hypertensive rats

The study aims to identify the mechanism (s) underlying the altered vasodilatory responses of the pial artery of spontaneously hypertensive rats (SHR) under a hypothesis that calcitonin gene-related peptide (CGRP) exerts a modulator role in the autoregulation of cerebral blood flow (CBF). The animals were divided into four groups: 1) Sprague-Dawley rats (SDR), 2) Wistar rats (WR), 3) SHR with high blood pressure (BP gtoreq 150 mmHg), and 4) SHR with normotensive BP (ltoreq 150 mmHg). The lower limit of CBF autoregulation in SHR shifted to a higher BP (82.8 +/- 9.3 mmHg, P < 0.05) than that in SDR (58.9 +/- 5.7 mmHg). In SHR, whether the BP levels were high or normotensive, the vasodilator responses to a stepwise hypotension were significantly attenuated unlike with SDR and WR. When artificial cerebrospinal fluid (CSF) containing capsaicin (3 X 10-7 M) was suffused over the cortical surface, a transient increase in pial arterial diameter was observed in the SHR with high or normotensive BP. In contrast, SDR and WR showed a large increase in diameter, and the increase was sustained for over 10 minutes. In line with these results, the basal releases of CGRP-like immunoreactivity (CGRP-LI) in the isolated pial arteries from SHR with high and normotensive BP were 12.5 +/- 1.4 and 9.8 +/- 2.8 fmole/mm2/60 min (P < 0.05), while those from SDR and WR were 25.5 +/- 3.1 and 24.6 +/- 3.1 fmole/mm2/60 min, respectively. The isolated basilar arteries showed similar results to those of the pial arteries in SHR. Thus, it is summarized that, in the SHR, the reduced autoregulatory vasodilator responses to stepwise hypotension and capsaicin may be, in part, ascribed to the decreased release of CGRP from the perivascular sensory nerve fibers of the pial arteries, and that altered vasomotor activity in SHR may not be related with the hypertensive tone.

An Experimental Study on the Protective Effect of Nimodipine in the Cerebral Neuronal Injury following Cerebral Ischemia / 대한마취과학회지

Cerebral autoregulation is the mainternance of a constant cerebral blood flow over a wide range of cerebral perfusion pressure. But irreversible hypoxic brain damage may occur as a consequence of such diverse conditions as lung and heart disease, shock, seizure or an episode of severe hypotension, and is potential hazard to any patient undergoing general anesthesia. The ultimate degree of neurological recovery may range from brain death and vegetative state to minor psychiatric disturbance and even normality, and is determined by the severity of the initial stress and wheather or not adequate resuscitation was commenced before irreversible brain damage. We performed an experiment to determine the protective effect of the calcium channel blocker nimodipine on the neuronal injury following cerebral ischemia in a rat model. The result were as follows: 1) Mean arterial pressure decreased more significantly in the nimodipine-treated group than the saline-treated group (p<0.01). 2) With respect to the degree of neuronal damage following cerebral ischemia, it decreased more significantly in the nimodipine-treated group than the saline-treated group (p<0.01).