Transvaginal color Doppler study of middle cerebral artery blood flow in early normal and abnormal pregnancy.

Transvaginal color and pulsed Doppler sonography was performed on 106 singleton pregnant women; 75 had clinically normal pregnancies, and the remaining 31 patients had complicated pregnancies with vaginal bleeding. The gestational ages ranged from the 7th to 18th menstrual weeks. The aim of the study was to establish the earliest gestational age at which intracranial blood flow could be detected, in particular in the middle cerebral artery. The intracranial circulation becomes visible at the 8th week of gestation (7 weeks and 3 days). The end-diastolic component of blood flow is inconstantly present from the 11th to the 13th gestational week, and is always detected thereafter. A significant decrease in the pulsatility index (p < 0.05) and peripheral flow impedance index (p < 0.001) was observed during the early weeks of pregnancy in both the normal and complicated pregnancies. There was no significant difference between the groups (p > 0.05). Results suggest that Doppler studies of middle cerebral arteries in early pregnancy are unlikely to be of value in identifying fetal hemodynamic disorders in the early stages of spontaneous abortion.     

Middle cerebral artery blood flow velocimetry among healthy fetuses with a single umbilical artery.

OBJECTIVE: A single umbilical artery (SUA) is an independent risk factor for perinatal morbidity and mortality in healthy fetuses. The aims of the study were (1) to determine middle cerebral artery (MCA) blood flow velocimetric values among fetuses without structural or chromosomal anomalies with an SUA and to compare them with nomograms of patients with a 3-vessel cord and (2) to measure the pulsatility index (PI) of the umbilical artery among these patients. METHODS: The PI values of the MCA and umbilical arteries were determined prospectively among 98 healthy fetuses with an SUA. The PI values were compared with nomograms of patients with a 3-vessel umbilical cord. For the MCA, peak systolic velocity (PSV) was also measured. Patients carrying fetuses with intrauterine growth restriction or congenital anomalies were excluded from the study. Middle cerebral artery PI values below the fifth percentile and PSV values above the 95th percentile adjusted for gestational age were considered abnormal. RESULTS: Gestational age ranged between 22 and 37.9 weeks (median, 30.3 weeks). After adjusting for gestational age, no alterations in the MCA PI and umbilical PI were found in comparison with the normal range for a 3-vessel cord known in the literature. Middle cerebral artery PSV values were also within the normal range for gestational age in all patients. CONCLUSIONS: The MCA PI and PSV values among healthy fetuses with an isolated SUA were similar to nomograms for fetuses with a 3-vessel umbilical cord. Therefore, abnormal MCA PI and PSV values among fetuses with an SUA should be treated the same as in patients with a 3-vessel umbilical cord.     

Comparison of caffeine-induced changes in cerebral blood flow and middle cerebral artery blood velocity shows that caffeine reduces middle cerebral artery diameter

Changes in cerebral blood flow (CBF) can be assessed directly with xenon clearance (XeC) or indirectly by measuring changes in middle cerebral artery blood velocity (Vmca) with transcranial Doppler (TCD). The aim of this study was to compare the changes in CBF and Vmca following caffeine ingestion. Nineteen patients (age 48-86, recovering from an acute stroke) and ten controls (age 52-85) were each studied twice. Bilateral measurements of CBF and Vmca were made before and after ingestion of 250 mg caffeine or matched placebo. The percentage change in CBF and Vmca after caffeine was calculated. Full results (CBF and Vmca) were obtained from 14 patients and 9 controls. There was no significant difference between patients and controls, so results were combined. Caffeine reduced CBF by 22% (95% confidence interval (CI) = 17% to 28%) and reduced Vmca by 13% (95% CI = 10% to 17%). The fall in Vmca was significantly less than that in CBF (p = 0.0016), showing that caffeine reduces mca diameter. Analysis based on Poiseuille flow in the arterioles suggests that caffeine reduced arteriole diameter by 5.9% (95% CI = 4.6% to 7.3%) and mca diameter by 4.3% (95% CI = 2.0% to 6.6%). TCD is being used as an alternative to XeC for assessing the effect of vasoconstrictors and vasodilators on CBF. This study has demonstrated that in mca diameter can be changed by the vasoactive agents, and that changes in Vmca do not necessarily reflect changes in CBF.     

Increased middle cerebral artery blood flow impedance in fetal subdural hematoma.

This case describes the prenatal diagnosis at 30 weeks' gestation of a posterior fossa subdural hematoma. Doppler velocimetry studies of the middle cerebral artery at that time showed an abnormally high resistance pattern with reverse end-diastolic flow. Ultrasonic assessment of the fetus indicated that there was associated quadriplegia. No cause for the lesion was demonstrated. A fetal blood sample, obtained by cordocentesis, revealed a normal karyotype. Fetal blood gas analysis was also normal. The pregnancy was terminated at the parents' request.     

Fetal cerebral blood flow redistribution in late gestation: identification of compromise in small fetuses with normal umbilical artery Doppler.

OBJECTIVE: To evaluate the role of middle cerebral artery Doppler in small fetuses during the late third trimester. DESIGN: Prospective observational study of structurally normal fetuses with an estimated fetal weight < 5th percentile for gestation. Perinatal outcome was determined using a structured datasheet sent to each referring obstetrician. SUBJECTS: Structurally normal fetuses at 35 or more weeks of gestation referred during a 2-year period to the fetal growth clinic of a regional fetal medicine unit in North London. Fetuses with aneuploidy and/or major structural abnormalities were excluded. METHODS: Umbilical artery and middle cerebral artery (MCA) Doppler waveforms were recorded and considered abnormal if above 95th or below 5th percentiles, respectively. Amniotic fluid was considered reduced if the maximum vertical cord-free pool was < 2 cm. The placenta was considered mature if the Grannum grade was II or III. The head circumference (HC)/abdominal circumference (AC) ratio was considered abnormal if > 95th percentile for gestation. Fetal growth, amniotic fluid, biophysical profile score and umbilical artery Doppler were used to advise the referring obstetrician about fetal well-being and he/she independently decided both the timing and mode of delivery. RESULTS: Forty-seven fetuses fulfilled the entry criteria. Thirty-four (72%) demonstrated normal umbilical artery Doppler waveforms. Sixteen (34%) demonstrated middle cerebral artery redistribution, of which nine (56%) had normal umbilical artery Doppler waveforms. MCA blood flow redistribution was associated with an increased incidence of cesarean delivery and need for neonatal admission. Of all gray-scale parameters, an elevated HC/AC ratio has the strongest association with MCA blood flow redistribution (15/16 vs. 1/31; P < 0.01). CONCLUSIONS: MCA Doppler may be a useful tool to assess the health of small fetuses in the late third trimester. Redistribution may occur in the presence of normal umbilical artery Doppler and should be suspected when the HC/AC ratio is elevated.     

Variability of middle cerebral artery blood flow with hypercapnia in women

We examined the effect of euoxic hypercapnia on middle cerebral artery (MCA) blood flow velocity waveform parameters in pre- and postmenopausal women by exposing 24 healthy women (12 pre-, 12 postmenopausal) to hypercapnia for 20 min. MCA blood flow velocity was measured continuously by transcranial Doppler ultrasound. The data were run through an algorithm that detected the feature points of the waveforms and then analyzed for statistically significant group differences. The changes in mean blood flow velocity with euoxic hypercapnia were not significant between the two groups. However, certain feature points, particularly the velocity of the reflected shoulder (V_REFLEC), increased (89.4 ± 14.6 to 110.0 ± 20.5 cm/s and 102.3 ± 14.1 to 125.1 ± 14.9 cm/s from euoxic eucapnia to euoxic hypercapnia in pre- and postmenopausal women, respectively), as did the augmentation index (79.9 ± 10.4 to 85.9 ± 12.6% and 114.7 ± 12.8 to 119.0 ± 12.6%) and pulsatility index (0.86 ± 0.18 to 0.74 ± 0.15 and 0.71 ± 0.11 to 0.66 ± 0.11). Furthermore, while systolic peak velocity (V_SYS) was the highest point of the waveform in premenopausal women, V_REFLEC was the highest point for the postmenopausal cohort. The implications of this finding become obvious when calculating pulsatility index (PI), the values of which varied significantly for the postmenopausal women, depending on whether V_SYS or the absolute maximum was used. These findings suggest that hypercapnia increases blood flow velocity waveform reflections, and that PI calculations, particularly for older age groups, may need to be considered more carefully, since these reflections often exceed the systolic peak velocity. (E-mail: poulin@ucalgary.ca)     

Superior mesenteric artery blood flow velocimetry: cross-sectional Doppler sonographic study in normal fetuses.

Our objectives were to describe the flow velocity waveform of the fetal superior mesenteric artery and to establish a nomogram for its pulsatility index. In a cross-sectional study using color Doppler ultrasonography, superior mesenteric artery flow velocimetry was investigated prospectively in 96 healthy fetuses of between 14 and 37 weeks of gestation. In normal fetuses the pulsatility index measurements showed a slight but insignificant increase over the course of gestation (r = 0.26; P > 0.5). The lowest mean +/- standard deviation for pulsatility index in the superior mesenteric artery was 1.86 +/- 0.45 (95% confidence interval 1.67-2.06), recorded between 18 and 21 weeks' gestation. Thereafter the pulsatility index increased to 1.94 +/- 6.4 (95% confidence interval 1.74-2.8) at 22 to 25 weeks, and from weeks 26 to 29 it increased to 2.18 +/- 0.52 (95% confidence interval 1.91-2.46). During the third trimester and at term, the mean pulsatility index of 2.23 +/- 0.32 (95% confidence interval 1.43-3.03) did not change significantly with gestational age. In normal fetuses, except for the early stages, a relatively stable vascular resistance of the intestinal circulation was found. The application of this nomogram in clinical practice may facilitate evaluation of intestinal perfusion in compromised fetuses with blood flow centralization.     

Comparison of different reference values of fetal blood flow velocity in the middle cerebral artery for predicting fetal anemia.

OBJECTIVES: To compare different normal reference ranges of fetal blood flow velocity in the middle cerebral artery for predicting fetal anemia. METHODS: Eight reference ranges of either middle cerebral artery peak or time-averaged mean velocities were compared using the area under the receiver-operating characteristics (ROC) curve for 113 fetal blood samples from 60 women at risk of fetal red blood cell alloimmunization. RESULTS: The areas under the ROC curves of the different ranges were not significantly different but there were marked differences in sensitivity (range, 7.14-91.78%) and specificity (range, 31.25-96.88%) with the currently used cut-offs. Except for Mari's range, the best theoretical cut-offs, defined as those having the best sensitivity with the best specificity, differed from those in current use, especially when using time-averaged mean velocity. CONCLUSIONS: Any of the previously reported reference ranges perform well in the non-invasive prediction of fetal anemia. However, with the exception of Mari's curve, the currently employed cut-offs for predicting fetal anemia should be changed, some of them markedly, in order to provide reliable support for clinical decisions.     

不同时间对不同体位高位脊髓损伤患者大脑中动脉血流的影响

目的分析比较高位脊髓损伤患者不同体位下大脑中动脉(MCA)血流动力学随时间变化的特征.方法采用经颅彩色多普勒超声(TCCD)技术,对48例高位脊髓损伤的患者分别于斜立位30°、60°、80°条件下检测MCA的峰值流速(PSV)、舒张期末流速(EDV)及平均流速(MV),每种斜立位均于保持3 min、7 min和15 min时记录流速参数,每个体位间隔10 min,比较不同时间、不同体位变化对MCA血流动力学的影响.结果斜立30°时血压下降幅度小,脑供血参数仅EDV 3 min、7 min下降明显,与平卧位相比P＜0.05;斜立60°时血压继续下降,造成PSV、EDV、MV均下降,与平卧位相比P＜0.05或P＜0.01;斜立80°时PSV、EDV、MV进一步下降,与平卧位相比P＜0.01.结论脊髓损伤患者随时间、体位变化影响MCA血流动力学的变化.     

大鼠大脑中动脉局灶性脑缺血局部脑血流动态观察

目的:动态观察了鼠须栓塞大鼠大脑中动脉局灶性脑缺血模型局部脑血流(regionalcerebralbloodflow,rCBF)变化与时间的关系。方法:雄性Wistar大鼠12只,体重250～350g。根据缺血时间分为缺血0.5,1.0,1.5,2.0,3.0,6.0,9.0,12.0h。采用鼠须栓塞法制做大鼠大脑中动脉局灶性脑缺血模型,氢清除法测定大鼠大脑中动脉供血中心区缺血各时点大脑皮层rCBF变化。结果:12h组2只动物因吸入氢气过量致窒息死亡,其他全部动物均在规定时间内完成rCBF测定。缺血前rCBF为(149.77±6.76)ml/(100g·min),缺血30min下降至(106.94±7.21)ml/(100g·min),缺血6h降至(12.73±1.66)ml/(100g·min)。除缺血90min和2h点rCBF无统计学显著差异外,其它各时间点rCBF均存在显著差异(P<0.01)。rCBF随时间渐趋下降,回归分析示与时间呈显著相关(r=-0.77,P=0.024)。至缺血12hrCBF不能测出。结论:该研究为扩大治疗时间窗的保护性治疗提供了脑血流变化的理论依据。     

Biofeedback-assisted relaxation in migraine headache: relationship to cerebral blood flow velocity in the middle cerebral artery

OBJECTIVE: To determine if migraineurs with aura respond differently to biofeedback/relaxation than those without aura and, if so, whether the variability in outcome can be explained by blood flow velocity. Background.-The relationship between cerebral blood flow velocity and treatment response to biofeedback/relaxation in migraine with and without aura is uncertain. METHOD: Twenty migraineurs underwent 12 sessions of biofeedback/relaxation therapy, while 20 controls simply were told to relax on their own. Cerebral blood flow velocity was measured bilaterally in the middle cerebral artery with transcranial Doppler. RESULTS: The biofeedback group showed significant (P <.05) reductions in pain, depression, and anxiety compared to the control group. Patients with and without aura did equally well. There were significant (P <.05) left to right blood flow velocity differences only in the migraine with aura group. Maximum blood flow velocities were significantly higher (P <.05) in the migraine with aura group than in the cohort without aura. There was an inverse correlation between indicators of anxiety and blood flow velocity, perhaps related to hyperventilation-induced constriction in the small vessels distal to the middle cerebral artery. CONCLUSION: The positive treatment response to biofeedback/relaxation in migraine headache is not related to presence of aura, nor to changes in blood flow velocity, but may be associated with reduction in anxiety and depression.     

Reference values of fetal peak systolic blood flow velocity in the middle cerebral artery at 19-40 weeks of gestation.

OBJECTIVES: The objectives of this prospective study were (i) to establish new reference values of peak systolic blood flow velocity measurement in the fetal middle cerebral artery (MCA-PSV) following validated methodological guidelines and (ii) to develop a method to calculate Z-scores of MCA-PSV. PATIENTS AND METHODS: Cross-sectional data were obtained from 331 pregnant women between 19 and 40 weeks' gestation. Reference ranges for MCA-PSV were constructed and for each measurement linear regression models were fitted separately to the mean and standard deviations (SD) as a function of gestational age. An application to calculate Z-scores was developed. A comparison was made between the reference ranges produced in our study and those of a previous one. RESULTS: A new chart, table of centiles and regression equations of MCA-PSV are presented. Comparison of our reference ranges with ones produced in a previous study showed similar 5th centile values. However, the values for the 50th and 95th centiles between 19 and 28 gestational weeks were lower in our study. CONCLUSIONS: We have constructed reference ranges for MCA-PSV which, because they are derived from a larger number of examinations in the 15-20-week period and because the methodological flaws of the previously published study have been eliminated, we consider to be more accurate and therefore more useful for clinical practice.     

Peripheral right pulmonary artery blood flow velocimetry: Doppler sonographic study of normal and abnormal fetuses.

The knowledge of fetal lung circulation in normal and abnormal human fetuses is limited. Our objectives were to assess normal values for flow velocity waveforms in the fetal pulmonic circulation and to test the hypothesis that Doppler velocimetry can predict lung hypoplasia. In a cross-sectional study, peripheral right pulmonary artery flow velocimetry was investigated prospectively in 96 healthy fetuses between 14 and 37 weeks' gestation and four fetuses with abnormalities known to induce lung hypoplasia. The pulsatility index was used to quantify the velocity waveforms. In normal fetuses the mean pulsatility index in the peripheral right pulmonary artery was low, being equivalent to that corresponding to 14 to 17 weeks' gestation (2.89; confidence interval = 2.35 to 3.42), increasing at midgestation to 3.44, with a confidence interval of 3.04 to 3.83; P < 0.01. Thereafter, during the late second and third trimesters the mean pulsatility index did not change significantly with GA, being 3.66 (confidence interval = 3.04 to 4.04) at term. In fetuses with proven lung hypoplasia, the pulsatility index measurements were within the 95% confidence limits of those for normal fetuses. In a normal pregnancy, except for the early stages, a relatively stable high vascular resistance of the fetal pulmonary circulation was found. Our preliminary data suggest that the pulsatility index of the lung circulation cannot be used as an indicator of lung hypoplasia.     

Modulation of middle cerebral artery flow velocity waveforms by breathing movements in the normal term fetus

Breathing dependency of fetal middle cerebral artery flow velocities was studied in 10 normal pregnancies at term. Peak systolic, end-diastolic and time-averaged flow velocities and pulsatility index during fetal breathing were not significantly different from those observed during apnoea. However, the standard deviation for each flow velocity parameter was significantly increased during fetal breathing activity, indicating marked modulation of middle cerebral artery velocities.     

Coronary artery blood flow visualization signifies hemodynamic deterioration in growth-restricted fetuses.

OBJECTIVE: To determine the relationship between fetal coronary blood flow (CBF) visualization in intrauterine growth restriction (IUGR), longitudinal changes in arterial and venous flow velocity waveforms and perinatal outcome. METHODS: A total of 48 IUGR fetuses (abdominal circumference below the 5th percentile for gestational age) with absent or reversed umbilical artery (UA) end-diastolic velocity (AREDV) were examined longitudinally by echocardiography attempting CBF visualization at each examination. Doppler evaluation of the middle cerebral artery, inferior vena cava (IVC), ductus venosus (DV) and umbilical vein (UV) was performed at each examination. Doppler measurements were correct for gestational age by conversion into Z-scores (delta-indices). Doppler results and outcome from fetuses in which CBF was visualized (group 1, n = 20) and those in which CBF was never visualized (group 2, n = 28) were compared. Outcome parameters analyzed included Apgar scores, cord arterial blood gases, perinatal mortality, respiratory distress, bronchopulmonary dysplasia, intraventricular hemorrhage, necrotizing enterocolitis and postpartum circulatory failure requiring pressor support. RESULTS: There was no difference in Doppler indices between groups at study entry. CBF visualization coincides with a significant increase of UA-, IVC- and DV delta-indices. The greatest rate of change was observed for indices in the ductus venosus which occurred in the 24 h preceding CBF visualization. Group 1 fetuses required earlier delivery (median 27 + 4, vs. median 30 + 0), had lower birthweight (682 +/- 305 g vs. 936 +/- 416 g), lower cord pH (7.21 +/- 0.1 vs. 7.27 +/- 0.06) and cord pO2 (13 +/- 4.5 vs. 24.1 +/- 13.5 mmHg) compared to group 2 (all values P < 0.05). Mortality was similar (group 1 = 6/20, 30%; group 2 = 6/28, 21.4%). CONCLUSIONS: In IUGR, fetuses with AREDV and centralization are at high risk for hypoxemia, acidemia and adverse outcome. CBF visualization coincides with deteriorating venous flows. Operator dependence of CBF visualization and the strong association with abnormal venous flow stresses the importance of venous Doppler surveillance in these fetuses.     

不同孕周脐带绕颈胎儿脐动脉及大脑中动脉血流参数的变化研究

目的：观察及探讨不同孕周脐带绕颈胎儿脐动脉及大脑中动脉血流参数的变化情况。方法：选取2010年10月—2013年5月于本院进行诊治的58例脐带绕颈胎儿为观察组,并以58例正常胎儿为对照组,将两组胎儿的脐动脉及大脑中动脉血流参数进行比较,并比较观察组中不同孕周胎儿的检测结果。结果：观察组胎儿的脐动脉及大脑中动脉PI、RI及S/D水平均高于对照组胎儿,而观察组中孕周37周以上者检测结果则高于28-36周的胎儿,P均〈0.05,均有显著性差异,同时分析检测指标与脐带绕颈的相关性。结论：脐带绕颈胎儿与正常胎儿脐动脉及大脑中动脉血流参数存在明显差异,且不同孕周脐带绕颈胎儿之间也存在显著差异,其与脐带绕颈有密切的关系,对于胎儿预后的价值较高。     

Human middle cerebral artery blood velocity during sexual intercourse.

Although the augmentation of central hemodynamics during human sexual intercourse is well established, dynamic changes in human regional cerebral blood flow have not been reported. Noninvasive transcranial Doppler ultrasonography has been well validated and allows direct, continuous measurement of phasic blood velocity in the human middle cerebral artery (a linear index of regional cerebral blood flow). The middle cerebral artery supplies the premotor and primary sensorimotor cortical regions for the arms, upper and lower trunk, and head. Blood velocities in this vessel have been shown to increase significantly with sensory stimuli and physical stresses. Accordingly, we tested the hypothesis that human sexual intercourse increases middle cerebral artery blood velocity. We used noninvasive, transcranial Doppler ultrasonography (95% confidence limits for precision +/- 7%) to measure blood velocity in the left middle cerebral artery of 10 male and 10 female, sexually acquainted, healthy adults (age range, 23 to 47 years; mean, 30 years). To eliminate signal artifacts and allow complete freedom of motion, a modified low profile, temporal fossa transducer was secured by minimal unobtrusive forehead strapping. Continuous measurements of phasic blood velocity and heart rate were made in a private bedroom setting during rest (control), preexcitement, excitation, prepenetration, penetration, preorgasm, orgasm, and resolution with the untethered instrumented subject in the supine missionary position. Heart rate and blood velocity responses were similar in both sexes. During orgasm, the maximal heart rate increased significantly (P < 0.05): 49 +/- 44% in women, 65 +/- 32% in men, and 58 +/- 38% combined from a combined resting value of 77 +/- 11 standard deviations SD beats per minute. Importantly, blood velocity in the middle cerebral artery of the 20 subjects remained unchanged (P > 0.10) from a resting value of 56 +/- 15 cm/s. In conclusion, in both sexes, human middle cerebral artery blood velocity, a linear index of human regional cerebral blood flow, does not increase significantly (P > 0.10) during human sexual intercourse.     

经颅多普勒测定大脑中动脉血流速度在偏头痛中的变化

经颅多普勒（TCD）是一种具有实时性的无创的诊断工具，它可连续同时监测双侧的脑血流速度，用以反映脑血管反应性的动态方式，本文就是利用这一技术，观察偏头痛患者在视觉刺激过程中大脑中动脉（MCA）血流速度的变化，进一步阐明偏头痛的发病机制。