Aneurysm of a persistent primitive olfactory artery. Case report

A ruptured anterior cerebral artery (ACA) aneurysm is reported in a patient in whom an anomalous ACA arose from the internal carotid artery at the bifurcation. The aberrant artery coursed anteriorly along the ipsilateral olfactory tract and made a hairpin turn posterior to the olfactory bulb, supplying the circulation of the ACA. Persistence of the primitive olfactory artery is suggested as an embryological origin of this vascular anomaly.

Effects of thyrotropin releasing hormone on cardiac and extracardiac flows of appropriately grown and growth-retarded fetuses

The objective of this study was to establish the effect of thyrotropin releasing hormone on the fetal circulation of appropriately grown and growth-retarded fetuses. Doppler recordings were performed immediately before and 15 min after maternal administration of 400 micrograms of thyrotropin releasing hormone in 14 women with appropriately grown and 19 with growth-retarded fetuses. Furthermore, in six women with growth-retarded fetuses, serial recordings were performed at 2-hourly intervals for 8 h until a second thyrotropin releasing hormone dose was administered. Velocity waveforms were recorded from the outflow tracts, inferior vena cava, umbilical artery, middle cerebral artery and descending aorta, and different Doppler indices calculated. In appropriately grown fetuses, thyrotropin releasing hormone induced a significant increase of peak systolic velocity values in the aorta and pulmonary artery and an increase of Doppler-estimated cardiac output. In growth-retarded fetuses, these changes were more evident and associated with a significant decrease in reverse flow in the inferior vena cava during atrial contraction. No changes were observed in fetal heart rate or in the other fetal vessels investigated. In the growth-retarded fetuses followed longitudinally, these changes were evident for the following 8 h and were potentiated by the second thyrotropin releasing hormone administration. In conclusion, thyrotropin releasing hormone induces significant hemodynamic effects on the fetal heart that may temporarily improve the impaired cardiac function of growth-retarded fetuses.

Changes observed in Doppler studies of the fetal circulation in pregnancies complicated by pre-eclampsia or the delivery of a small-for-gestational-age baby. I. Cross-sectional analysis

The aim of this study was to compare changes in Doppler ultrasound studies of the fetal circulation in normal pregnancies with a group of pregnancies complicated by proteinuric pregnancy-induced hypertension (PPIH), delivery of a small-for-gestational-age (SGA) baby, or both. A total of 167 uncomplicated pregnancies with a term delivery of an appropriately grown baby (AGA) were used to define the normal range. Altogether, 123 high-risk pregnancies with a known outcome constituted the study group. A color duplex ultrasound machine was used to perform biometry and fetal Doppler studies. Measurements obtained from the fetal circulation included the umbilical artery (UA) pulsatility index (PI), the middle cerebral artery (MCA) PI and time-averaged velocity (TAV), the thoracic aorta (AO) PI and TAV. In addition, the ratio between the MCA PI and UA PI, the MCA PI and the AO PI, and the product of the MCA PI and AO TAV were used in the analysis. A total of 105 pregnancies had a complicated outcome. They were divided into three categories: PPIH only (pregnancies complicated by PPIH with the delivery of an AGA fetus, n = 17), SGA only (delivery of an SGA baby, with no evidence of PPIH, n = 55), and PPIH + SGA (pregnancies complicated by pre-eclampsia and delivery of an SGA baby, n = 37). The PPIH + SGA group represented true clinical intrauterine growth retardation. Cross-sectional reference ranges were created using the observations from the normal group. z-scores (standard deviation from the mean of the normal range) of the last observations made before delivery were calculated for each of the vessel velocimetry measurements and ratios. The statistical significance of z-score values was calculated using analysis of variance. The MCA and UA PI values showed the greatest deviation for any single-vessel parameter. The ratios of fetal Doppler indices (MCA/UA PI ratio, MCA/AO PI ratio and the MCA PI/AO TAV index) demonstrated greater deviation from normal than any individual vessel. The UA PI z-score for PPIH+SGA delivering < 34 weeks gestation (2.92) was significantly greater than the z-score for PPIH+SGA delivering > or = 34 weeks (1.20, p < 0.05). Fetal Doppler indices, in particular ratios that include measurements obtained from the cerebral circulation, help in the recognition of the small fetus that is growth-retarded. At term, evidence of fetal hemodynamic redistribution may exist in the presence of a normal umbilical artery PI. Fetal Doppler indices provide information that is not readily obtained from more conventional tests of fetal well-being.(ABSTRACT TRUNCATED AT 400 WORDS)

Doppler velocimetry of the fetal middle cerebral artery in patients with preterm labor and intact membranes

A prospective cohort study was conducted to determine whether preterm labor is associated with changes in the impedance to blood flow of the fetal middle cerebral artery. Doppler velocimetry studies were performed in 194 consecutive patients with preterm labor and intact membranes. Pulsatility indices of the middle cerebral artery and umbilical artery were determined on admission. Results were expressed as ratio of the observed pulsatility index to mean value for gestational age expressed as delta MCA PI and delta UA PI, respectively. The prevalence of preterm delivery (< 37 weeks) and delivery within 24 hours of admission was 55.2% (107/194) and 15.5% (30/194), respectively. Patients with an examination-to-delivery interval within 24 hours had significantly lower mean delta MCA PI than that of patients delivered at > or = 37 weeks and > or = 4 weeks after the examination (P < 0.01). Fetuses with a delta MCA PI at or below 0.88 had a relative risk of 2 (95% confidence interval, 1.32 to 2.9) who were delivered within 24 hours compared to controls (sensitivity 76.7%, specificity 62.8%, positive predictive value 26.7%, negative predictive value 93.5%). Stepwise logistic regression analysis indicated that the relationship between delta MCA PI and examination-to-delivery interval remained statistically significant after correcting for cervical dilatation (P < 0.001). Our data indicate that preterm parturition is associated with a decrease in the impedance to flow in the fetal cerebral circulation.

Doppler flow velocimetry of the umbilical artery, uteroplacental arteries and fetal middle cerebral artery in prolonged pregnancy

A total of 153 pregnant women, of at least 287 days' menstrual age, were studied in a prospectively designed cross-sectional trial. In addition to the non-stress test, contraction stress test, sonographic estimate of amniotic fluid and grade of placental maturation, Doppler measurements of the resistance index (RI) were taken in the umbilical artery, the uteroplacental arteries in the region of placental implantation and the fetal middle cerebral artery. Data were analyzed with regard to asphyxia and otherwise complicated fetal outcome. Furthermore, a possible relationship between grade of placental maturation, Doppler flow velocity waveforms and fetal outcome was investigated. Doppler resistance indices in the umbilical artery, uteroplacental arteries in the region of placental implantation and fetal middle cerebral artery did not change significantly with increasing gestation from 41 to 43 weeks. The grade of placental maturation on ultrasound examination was not related to fetal outcome or Doppler indices in the first two vessels. In all vessels examined in this study, the majority of Doppler measurements in pregnancies with subsequent asphyxia or otherwise complicated fetal outcome were within the 95% prediction interval for patients with normal fetal outcome. None of the patients showed absent diastolic flow in the umbilical artery. With the use of a cut-off value of RI = 0.62 in the umbilical artery, asphyxia could be predicted with 37% sensitivity and 75% specificity. Oligohydramnios and antpartum cardiotocography predicted asphyxia with 16% and 8% sensitivity and 95% and 96% specificity, respectively. Sensitivity for prediction of otherwise complicated fetal outcome by umbilical artery Doppler was only 7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal arterial Doppler studies in twin-twin transfusion syndrome

This cross-sectional study investigates the circulatory profile of the donor and recipient fetuses in pregnancies with twin-twin transfusion syndrome manifested by acute polyhydramnios during the second trimester of pregnancy. Doppler investigations of the umbilical arteries and of the fetal descending thoracic aortas and middle cerebral arteries were performed in both fetuses of 27 pregnancies with twin-twin transfusion syndrome at 18 to 25 (mean, 21.7) weeks' gestation. Significant differences from normal values were increased umbilical artery pulsatility index and decreased aortic mean velocity in both donor and recipient fetuses, decreased middle cerebral artery pulsatility index in recipients and decreased middle cerebral artery mean velocity in donors. Increased umbilical artery pulsatility index in some donor and recipient fetuses may be the consequence of abnormal placental development and polyhydramnios-related compression, respectively. Doppler findings in the fetal circulation are compatible with hypovolemia in the donor and hypervolemia with congestive heart failure in the recipient.

Concentration-dependent effects of cocaine on monoamine-induced constriction of cannulated, pressurized cerebral arteries from fetal sheep

Drugs, such as cocaine, which may alter monoamine neurotransmitter responsiveness, could adversely affect the regulation of cerebral vasculature. Cocaine exhibits at least two mechanisms that may alter vascular responsiveness: synaptic uptake inhibition, which may augment response to stimulation, and Na+ channel inhibition, which may attenuate response. To help elicit the concentration-dependent effects of cocaine, the effects of cocaine on monoamine neurotransmitter responsiveness were studied in vitro on fetal sheep cerebral arteries (120 days gestation). The changes in diameter of segments of cannulated, pressurized fetal sheep cerebral artery were measured with a videomicroscaler system. Cumulative concentration-response curves (10(-10) to 10(-4)M) were generated for two monoamines, norepinephrine and serotonin, alone and in the presence of cocaine (10(-5) or 10(-4)M). Cocaine caused concentration-dependent alteration of response. At 10(-4)M, cocaine attenuated mean maximal norepinephrine-induced vasoconstriction 46.2% (P < 0.05). At 10(-5)M, cocaine increased sensitivity to norepinephrine (log EC50 decreased -6.63 +/- 0.09 to -7.11 +/- 0.03) and to serotonin (log EC50 decreased -7.24 +/- 0.04 to -7.81 +/- 0.09) (P < 0.05). The higher concentration of cocaine (10(-4)M) did not significantly decrease log EC50 norepinephrine. Cocaine (10(-4)M) also attenuated the response to single doses of norepinephrine (10(-6)M) and serotonin (10(-6)M) by 26.5% and 40.0%, respectively (P < or = 0.05). It is concluded that cocaine has concentration-dependent effects on vasoconstriction of the fetal sheep cerebral artery in vitro. This cocaine-induced alteration of cerebral vascular responsiveness to monoamines may be important in the regulation of fetal cerebral blood flow.

Blood flow velocity waveforms of the fetal middle cerebral artery in pregnancies complicated by diabetes mellitus

Fetal blood flow velocity waveforms of the middle cerebral artery were measured by pulsed Doppler ultrasound in 43 pregnant women with diabetes mellitus (33 class B, 3 class C, 6 class D and 1 class R). The recordings were performed between 24 and 38 weeks of gestation. A total of 122 recordings were analyzed prior to establishing the resistance index (RI = peak systolic velocity minus diastolic velocity/peak systolic velocity). The mean maternal serum glucose was 124.3 mg/dl (range: 72.7 to 281.5 mg/dl), the mean hemoglobin A1c was 6.03% (range: 3.3 to 11.0%) and the mean fructosamine level was 255.97 mumol/L (range: 205 to 397 mumol/L). The resistance index did not differ between the fetuses of the diabetic mothers in our study population. Additionally, no significant correlation was noted between RI values and serum glucose levels (r = 0.03), hemoglobin A1c levels (r = 0.13) or fructosamine levels (r = 0.04) during the period of 26 to 34 gestational weeks. These data indicate that the RI within the fetal cerebral artery is unaffected by the maternal glycemic control when mean serum glucose levels are below 280 mg/dl.

[Antenatal screening for fetal well being by pulsed Doppler velocimetry]

A pulsed Doppler screening study was performed on pregnant women to investigate the ability of the test to detect adverse pregnancy outcome by following two methods. The waveforms were analyzed by calculating the resistance index (RI). Method 1.: longitudinal study: Blood flow velocity in the umbilical artery (UA) was recorded at 23, 28, 32, and 35 weeks' gestation in 726 pregnancies. Method 2.: cross-sectional study with FAS: Blood flow velocity in the UA and fetal middle cerebral artery (MCA) was recorded before and after fetal acoustic stimulation (FAS) at 35 weeks' gestation in 525 pregnancies. Result 1.: As UA-RI decreases continuously with gestational age, there was a linear correlation between them. The 726 cases were classified into three groups according to the UA-RI value. The UA-RI of the control group (n = 698) never reached mean + 2SD. The UA-RI of the +2.5D group (n = 4) increased with gestational age and was over mean +2.5SD at the last measurement. The +2SD group (n = 24) remained. There was a significant adverse pregnancy outcome in the +2.5SD group as judged by intrauterine growth retardation (SGA) (+2.5SD; 75%, +2SD; 17%, control; 10%), fetal distress (+2.5SD; 75%, +2SD; 5%; control; 9%) and pregnancy induced hypertension (+2.5SD; 75%, +2SD; 23%, control; 8%). Result 2.: The normal ranges of UA-RI and MCA-RI were calculated at 35 weeks' gestation, both before and after FAS, and women with UA-RI > +2SD or MCA-RI < -2SD were considered as abnormal.(ABSTRACT TRUNCATED AT 250 WORDS)

Embryology of the cerebral vasculature

Although much remains to be learned about the embryology of the intracranial vasculature, much of the developmental pathways of the intracranial vascular system are now apparent. Understanding these pathways offers the potential to appreciate the nature of such arterial anomalies as the azygos anterior cerebral artery and the trigeminal artery and such venous anomalies as the vein of Galen malformation and the venous angioma.

High expression on Kunitz-type protease inhibitor-containing substances in the cerebral vessels of patients with Down syndrome

Down syndrome (DS) brains, from 19 gestational weeks to 50 years of age were studied by immunohistochemical methods with a polyclonal antibody against synthetic peptide comprising part of the Kunitz-type protease inhibitor (KPI) domain of Alzheimer disease amyloid precursor protein (APP), residues 301 to 323 of APP 770. In DS, positive KPI immunoreactivity was observed in early infancy and from child to adulthood on the tunica media of the arteries in the leptomeninges, cerebral cortex and white matter, but negative or little in controls. In DS with Alzheimer type dementia, KPI immunoreactivity in the arteries was reduced, but a gross granular reactivity was noted in neurons and glial cells. The high expression of KPI in DS vessels may be one of the predisposing factors to vascular diseases and amyloid deposition associated with DS.

Doppler colour flow imaging of fetal intracerebral arteries relative to fetal behavioural states in normal pregnancy

In 14 normally developing term fetuses, the relationship between the blood flow velocity waveforms at cerebral arterial level (internal carotid artery, anterior, middle and posterior cerebral artery) and fetal behavioural states was studied using Doppler colour flow imaging. Behavioural state dependent changes in absolute flow velocities occurred in all vessels, except for the middle cerebral artery. These changes suggest preferential blood flow to the left heart resulting in increased flow to the cerebrum during fetal behavioural state 2F (active sleep) when compared with fetal behavioural state 1F (quiet sleep). The middle cerebral artery supplies the neocerebrum. This developing part of the cerebrum does not seem to take part in the regulation of fetal behaviour. In the internal carotid artery, an inverse relationship between peak systolic velocity and fetal heart rate could be established, which can be explained by a shorter rapid filling phase at raised fetal heart rate according to the Frank-Starling Law.

Mesencephalo-diencephalic angioanatomy in arteriovenous malformations. Endovascular management of transmesencephalic vs subependymal supply in 954 cases between 1982 and 1994

This report presents the arteries of the mesencephalo-diencephalic region and their different role in the supply to the cerebral structures. Among them, the authors distinguish the subependymal and transmesencephalic arteries to which they pay a special attention since these vessels present a specific angiographic aspect. The importance of their differentiation is emphasized. The authors discuss the management of subependymal and (trans)mesencephalic arteries during endovascular neuro-intervention illustrative cases.

Effects of cocaine, benzoylecgonine, and cocaine metabolites in cannulated pressurized fetal sheep cerebral arteries

Prenatal cocaine exposure has been reported to cause neurovascular complications in the developing fetus. To determine the effect of cocaine on the fetal neurovasculature, we studied the in vitro response of fetal sheep cerebral arteries to cocaine and cocaine metabolites. The change in diameter of cannulated pressurized cerebral artery segments from fetal sheep was measured using a video microscaler system. Cumulative dose-response curves (10(-12)-10(-4) M) were generated for cocaine and the major cocaine metabolites in fetal sheep cerebral artery segments. Benzoylecgonine (> 10(-10) M) also caused concentration-dependent constriction, and cerebral artery segments were significantly more sensitive to benzoylecgonine than to cocaine and the other cocaine metabolites. Benzoylecgonine-induced vasoconstriction appeared to be mediated through alpha-adrenergic stimulation, predominantly through stimulation of alpha 1-adrenergic receptor subtypes. We conclude that cocaine and benzoylecgonine cause significant fetal cerebral artery vasoconstriction in vitro. Cocaine and benzoylecgonine-induced cerebral vasoconstriction may contribute to the perinatal neurovascular complications associated with prenatal cocaine exposure.

[Evaluation of blood flow in the middle cerebral artery of the fetal brain during normal pregnancy using color doppler]

Transvaginal color Doppler ultrasonography was performed to analyze fetal cerebral blood flow in 62 singleton noncomplicated pregnancies. Pulsatility index and peripheral flow impedance index in middle cerebral artery were measured. Pulsatility and peripheral flow impedance indexes decrease was observed. Obtained values may be used as a reference for future investigation.

Regional cerebral flow velocity waveforms in the human fetus

The purpose of this study was to determine regional cerebral flow velocity waveforms in the human fetus. Flow velocity waveforms were determined at the level of the middle cerebral artery, vertebral artery, and intracerebellar arteries in 25 fetuses between 23 and 39 weeks' gestation. The pulsatility index was used to quantify the waveforms. Technically acceptable waveforms were obtained at all three vessels in 20 fetuses. The pulsatility index was lowest for the intracerebellar artery in all the fetuses studied. The pulsatility indices of the vertebral artery and middle cerebral artery were not significantly different. These data suggest that significant fetal regional cerebral blood flow differences occur in utero, with intracerebellar arterial resistance being lower than resistance in other regions of the brain.

A quantitative study on the retial arteries in the bovine fetus

The rostral epidural rete mirabile was injected with latex and the retial arteries were studied quantitatively in three groups of bovine fetuses. It was seen that the differences between the diameters of the right and left retial arteries were not significant. An interesting observation was that the diameter of the internal carotid artery decreased gradually with an increase in the gestational age, but this reduction was made up for the maxillary artery via the rostral rete branches. The proportion of the blood supply to the rete was also determined in three groups of fetuses.

Maternal plasma glucose levels and Doppler flow velocity waveforms in cerebral arteries of growth-retarded fetuses

Doppler flow studies of the intracranial internal carotid artery and middle cerebral artery performed in 17 women at 30-36 weeks of gestation, referred for evaluation of small for gestational age fetuses, resulted in abnormally low pulsatility index values (below 2 SD). These patients were investigated when fasting and 1 h after a 100-gram glucose load. Increase of 20 ml/dl or more was followed by elevation of the mean pulsatility index in the internal carotid artery from 1.03 +/- 0.09 to 1.44 +/- 0.22 (p < 0.001), and in the middle cerebral artery from 1.12 +/- 0.16 to 1.83 +/- 0.24 (p < 0.001). Pulsatility index values returned to normal (within 2 SD for gestational age) in 15 of the subjects investigated after glucose load. These findings suggest the importance of standard fasting state or determination of maternal plasma glucose levels in patients undergoing Doppler flow evaluation of growth-retarded fetuses.

[Doppler ultrasound diagnosis in post-term pregnancy]

The capability of Doppler flow velocimetry to predict intrauterine growth retardation is well known. The increased morbidity and mortality rate of postterm newborns is also well known. The aim of our study was to examine if Doppler flow velocimetry is able to indicate foetal jeopardy in the postterm period. Flow velocimetry of the foetal descending aorta, the umbilical artery, the uterine arteries and in 59 cases also the foetal middle cerebral artery was obtained from 167 pregnancies after 40 completed weeks of gestation. We found significant changes of normal values in prolonged pregnancy compared to third trimester normal values, examining the mean velocity of the foetal descending aorta and the S/D-ratio of the umbilical artery. No clinically significant changes were found examining the S/D-ratio of the uterine arteries and the pulsatility index of the foetal middle cerebral artery. Daily examinations of the foetal descending aorta were carried out in 23 and of the umbilical artery in 19 cases during the last four days before delivery, and in 11 cases of the foetal middle cerebral artery during the last three days before delivery. We did not find significant changes in the medians of the mean velocity of the foetal aorta, of the S/D-ratio of the umbilical artery and of the pulsatility index of the foetal middle cerebral artery. Measurement of sensitivity and positive predictive value of the four arteries examined showed, that Doppler ultrasound could not predict small for date infants or Caesarean section because of foetal distress.(ABSTRACT TRUNCATED AT 250 WORDS)

[Normal values of color Doppler ultrasound in pregnancy]

In addition to the flowmetrie of aorta fetalis and a. umbilicalis, color flow mapping enables the examination of the renal and middle cerebral arteries in the assessment of the fetal blood circulation. The resistance and pulsatility-indices of aorta fetalis, umbilical artery, renal artery and middle cerebral artery were calculated in a prospective examination of a normal study group of 123 pregnant women. Moreover, ratios were established from the pulsatility-indices of renal artery and aorta fetalis, renal artery and umbilical artery, middle cerebral artery and aorta fetalis, middle cerebral artery and umbilical artery. By the use of these ratios, we hope to detect more reliably changes in the fetal blood circulation.

The "brain-sparing" effect: antenatal cerebral Doppler findings in relation to neurologic outcome in very preterm infants

OBJECTIVE

Our purpose was to study the relationship between fetal cerebral circulation and neurologic outcome.

STUDY DESIGN

In 117 high-risk fetuses (gestational age 25 to 33 weeks) flow velocity waveforms were recorded from the umbilical and medial cerebral arteries. The ratio between umbilical and cerebral pulsatility indexes was calculated. A ratio above a predefined tolerance limit was used as an index for the "brain-sparing" effect. Neonatal neurosonography and neurologic examination were used as outcome parameters.

RESULTS

Antenatally raised ratios are associated with poor obstetric outcome (fetal death and fetal growth retardation). The incidence of intracranial hemorrhages and ischemic lesions was not different for infants with a normal or raised prenatal ratio. The incidence of neurologic abnormalities was the same for both ratio groups.

CONCLUSIONS

The "brain-sparing" effect is a mechanism to prevent fetal brain hypoxia rather than a sign of impending brain damage.

[Correlation between reduced amniotic fluid volume and Doppler spectra of fetal blood vessels at term]

The aim of this study was to determine, whether foetuses with reduced amniotic fluid in other-wise uncomplicated pregnancies at term show signs of redistribution of blood flow analogous to foetuses with intrauterine growth retardation. In 33 pregnancies > or = 37 gestational weeks with the largest pocket of amniotic fluid < 2 cm, flow velocity waveforms were recorded for the umbilical artery, middle cerebral artery and renal artery and compared with those of foetuses of the same gestational age and normal amniotic fluid volume. No difference was found in the resistance index (umbilical artery and middle cerebral artery), the pulsatility index (renal artery), or for the cerebral-placental ratio between these two collectives. We conclude, that Doppler examination of foetal vessels does not help to clarify the phenomenon of decreasing amniotic fluid volume during the final period of gestation. We suggest, that the decrease is not caused by renovascular changes, but has intra- or extrarenal causes.

[Value of vascular resistance in fetal circulation during normal pregnancy]

The aim of the study is to estimate the values of resistance index (RI) in the arteries of the fetus using color doppler ultrasound. Measurements have been made in aorta, umbilical and medial cerebral artery of the fetus and in arcuate artery of the pregnant women. 50 women have been examined every 4 weeks and another 50 every 6 weeks during normal pregnancy. Resistance index has been calculated based on analyses of flow waves configuration in all of the mentioned arteries. Likeness between curves obtained in women examined every 4 and 6 weeks in obvious. The examination of mean RI values shows that vascular resistance in descending aorta remains constant during the vascular resistance in descending aorta remains constant during the all the period. In arcuate artery vascular resistance falls down until 22 week of pregnancy and then settles on constant level. RI of umbilical artery decreases during pregnancy and in median cerebral artery reaches its peak in 32/34 week of pregnancy.

Cerebrovascular adaptations to high-altitude hypoxemia in fetal and adult sheep

In the fetus and infant, high-altitude hypoxemia is associated with increased cerebrovascular morbidity. To test the hypothesis that this increased morbidity involves changes in cerebrovascular endothelial and smooth muscle function, we examined middle cerebral, posterior communicating, basilar, and common carotid arteries obtained from 23 normoxic fetuses, 19 hypoxemic fetuses maintained at high altitude (3,820 m) from 30 days gestation to near term (approximately 143 days), 55 normoxic non-pregnant adults, and 24 hypoxemic nonpregnant adults maintained at the same altitude and duration as the hypoxemic fetuses. Long-term hypoxemia was associated with several significant changes in both fetal and adult arteries, including a generalized increase in base-soluble protein (5-50%), a depression of the maximum potassium-induced tensions (16-49%), and a depression of the relaxation responses to S-nitroso-N-acetylpenicillamine (1-11%), which releases nitric oxide into solution upon hydration. Altitude acclimatization significantly enhanced amine-to-potassium ratios (the ratio of tension produced by 10 microM serotonin with 20 microM histamine to that produced by 122 mM potassium) only in adult cerebral arteries (51-87%) and significantly depressed potassium-induced stresses (up to 41%) and serotonin/histamine-induced tensions (20-37%) only in fetuses. Endothelium-dependent relaxations to A23187 were significantly depressed in hypoxemic fetuses (4-11%) but were significantly enhanced in hypoxemic adults (2-14%). We conclude that chronic hypoxemia depresses both vascular smooth muscle and endothelial function to a greater extent in fetal than in adult cerebral arteries and that this effect could contribute to the greater postnatal vulnerability to asphyxic and hypertensive insults seen in hypoxemic neonates.

Doppler colour flow mapping of fetal intracerebral arteries in the presence of central nervous system anomalies

The adjunctive role of Doppler colour flow mapping in the evaluation of intracerebral morphology and arterial blood flow in the presence of normal and abnormal central nervous system morphology was determined. A total of 59 fetuses with suspected central nervous system pathology between 14 and 37 weeks of gestation was studied (median 31 weeks). One hundred and one fetuses with normal central nervous system anatomy between 14 and 37 weeks (median 19 weeks) served as controls. Visualisation of blood flow in one or more intracerebral arterial vessels was successful in more than 80% of normal fetuses. For the anterior, middle and posterior cerebral artery, the percentages were 63%, 89% and 45%, respectively, at 14-25 weeks and 74%, 100% and 55%, respectively, at 26-37 weeks of gestation. Intracerebral arterial flow identification was attempted in 52/59 (88%) affected fetuses. Identification of blood flow in one or more intracerebral arterial vessels was successful in 40/52 (77%) fetuses. End-diastolic flow velocities were present in at least one of the intracerebral arteries in 39/40 fetuses, absent in one case of hydrocephaly and raised in the presence of an intracerebral vascular tumour. Doppler colour flow mapping seems to provide only limited additional information on intracranial structural pathology.