Increase In Pulsatility Index Research Articles

Fetal Cardiac Natriuretic Peptide Expression and Cardiovascular Hemodynamics in Endotoxin-Induced Acute Cardiac Dysfunction in Mouse

We hypothesized that, in acute endotoxin-induced fetal cardiac dysfunction, atrial (ANP) and B-type (BNP) natriuretic peptide mRNA expressions are increased in proportion to the severity of fetal cardiovascular compromise in mouse. To investigate in vitro the effect of endotoxin-induced inflammation on cardiac natriuretic peptide expression, fetal hearts were harvested at 15-16 d of gestation and incubated for 6 h with lipopolysaccharide (LPS). To examine the relationship between fetal cardiovascular compromise and cardiac natriuretic peptide expression in endotoxin-induced cardiac dysfunction in the in vivo model, fetuses received intra-amniotically 25 microL LPS (10 microg/mL) or 25 microL of 0.9% saline. Fetal Doppler ultrasonography was performed before and six hours after the injections. In in vitro cultured fetal hearts, LPS induced the production of proinflammatory cytokines without affecting the basal expressions of natriuretic peptides. In the in vivo model, Doppler ultrasonography revealed severe cardiac dysfunction after LPS injection. No significant changes in ANP or atrial BNP mRNA were found. The fetal ventricular BNP mRNA levels were about 2.6-fold in the LPS group compared with the control group. Decreased fetal cardiac outflow mean velocity, increased proportion of isovolumetric contraction time of the cardiac cycle, and increased pulsatility indices of the descending aorta and inferior vena cava were related to elevated ventricular BNP mRNA levels. Our results show that LPS did not increase the mRNA expression of natriuretic peptides in cultured fetal hearts. In contrast, fetal ventricular BNP gene expression was increased in proportion to the severity of the hemodynamic compromise in vivo.

Uterine artery Doppler measurement and pro-inflammatory cytokines in normal pregnancy

Differences in the inflammatory response between normal pregnancy and the non-pregnant state are more marked than that between normal pregnancy and pre-eclampsia. Doppler studies of the uterine arteries in the second trimester have reported an increased pulsatility index (PI) in women at high risk for pre-eclampsia. We aimed to examine the relationship between certain pro-inflammatory cytokines and uterine artery Dopplers in normal pregnancy.

Transcranial Doppler to detect on admission patients at risk for neurological deterioration following mild and moderate brain trauma

To investigate the contribution of transcranial Doppler measurements obtained in the emergency room for detecting patients with secondary neurological deterioration after mild or moderate brain trauma. Prospective cohort study in the emergency room in a university teaching hospital. Seventy-eight adult patients admitted to the emergency room after a traumatic brain injury (TBI), including 42 patients with Glasgow Coma Score 14-15 and 36 with 9-13. All patients had transcranial Doppler measurements on both middle cerebral arteries and computed tomography on admission. Neurological outcome was assessed 7 days after trauma. Of the patients included 7 and 10 had secondary neurological deterioration after mild and moderate TBI, respectively. On admission these groups of patients had significantly more injuries on computed tomography using the Trauma Coma Data Bank classification and higher pulsatility index using transcranial Doppler than the patients having no subsequent neurological worsening. Increased pulsatility index after mild or moderate TBI is a reason for concern about the possibility of further neurological deterioration. Computed tomography and Doppler measurements could be combined to detect on admission patients at risk for secondary neurological deterioration in order to improve their initial disposition.

Prospect for vaginal delivery of growth restricted fetuses with abnormal umbilical artery blood flow.

The best mode of delivery in cases of intrauterine growth restriction (IUGR) with umbilical artery blood flow changes is not well elucidated. To evaluate outcome in IUGR with umbilical artery blood flow changes planned for vaginal delivery after a negative oxytocin challenge test (OCT). In 84 term singleton pregnancies with suspected IUGR and no unanimous indication for abdominal delivery, Doppler velocimetry and OCT were performed. Positive OCT cases were delivered by cesarean section, negative OCT cases planned for vaginal delivery. Umbilical artery Doppler velocimetry was normal in 51 cases (normal group) and abnormal in 33 cases (increased pulsatility index with maintained forward diastolic flow). Gestational age at delivery was shorter (p = 0.008), positive OCT more common (33% vs. 16%; p = 0.06), and vaginal delivery less common (40% vs. 63%; p = 0.04) in the abnormal blood flow group compared with the normal flow group. When in labor, 68% in the abnormal flow group and 76% in the normal flow group delivered vaginally (p = 0.6). One baby had a lethal malformation and another suffered meconium aspiration and pneumothorax, but was discharged home healthy. The vaginal delivery rate was significantly lower in the abnormal flow group compared with the normal flow group, but in cases finally destined for a trial of labor the vaginal delivery rates were similar. There was no indication that any fetus was exposed to detrimental hypoxia or distress.

Prognostic role of umbilical artery Doppler velocimetry in growth-restricted fetuses

Objective: To correlate umbilical artery Doppler velocimetry with perinatal outcome in a group of growth-restricted fetuses. Design: The study was a retrospective analysis of 578 singleton pregnancies with diagnosis of intrauterine growth restriction (IUGR), delivered in a single obstetric unit, at the Spedali Civili, Brescia, Italy, a university and teaching hospital with 3500 deliveries a year and neonatal intensive care unit (NICU). Methods: During 1991-99 we studied 578 pregnancies with a diagnosis of IUGR referred for Doppler velocimetry. From this population, four subsets were formed: normal umbilical artery pulsatility index (NUAPI; 334 fetuses); increased pulsatility index but with telediastolic flow (abnormal umbilical artery pulsatility index AUAPI; 137 fetuses); absent end-diastolic flow (AEDF; 70 fetuses); reverse telediastolic flow (RF; 37 fetuses). Fetal biometry, amniotic fluid and fetal-maternal Doppler velocimetry were evaluated in all patients, with biophysical profile and routine non-stress test, when indicated. The following outcomes were examined: mean gestational age at delivery, number of preterm deliveries (< 34 weeks), mean neonatal weight, Apgar score at 5 min < 7, prenatal and neonatal deaths (within the first 28 days of life), admission to the NICU and number of days spent after birth in hospital. Neonatal morbidity was analyzed, including respiratory distress syndrome (RDS), intraventricular hemorrhage (IVH, grade 2-3), necrotizing enterocolitis (NEC) and retinopathy of prematurity. Long-term neurological follow-up is still ongoing and will not be presented in this paper. Results: Out of 578 fetuses with IUGR, 547 were born alive. There were 26 neonatal deaths. The mean gestational age at delivery was 35.6 ± 4 weeks and mean birth weight 1844 ± 612 g. There were 28 intrauterine deaths and three elective terminations of pregnancy. A total of 60 cases (11%) were complicated by RDS, 13 cases (2.4%) by retinopathy of prematurity, IVH was present in nine cases (1.6%) and NEC in seven cases (1.3%). Total perinatal mortality was 9.8%; in the 26 cases of neonatal death, the mean week at delivery was 29.6 ± 4 with a mean weight of 840 ± 425 g. Patients with NUAPI had a mean week at delivery of 37 ± 3, those with AUAPI delivered at 34 ± 3.2, those with AEDF delivered at 31 ± 3 and those with RF delivered at 29 ± 2 weeks. In progressively worsening umbilical velocimetry, we observed an increase of incidence of low Apgar score. Days of admission to the NICU and incidence of perinatal mortality increased with the worsening of Doppler velocimetry. Conclusions: Our study underlines the existence of a strict correlation between umbilical Doppler velocimetry and an increased incidence of perinatal complications in IUGR fetuses.

Prognostic role of umbilical artery Doppler velocimetry in growth-restricted fetuses

Objective: To correlate umbilical artery Doppler velocimetry with perinatal outcome in a group of growth-restricted fetuses.Design: The study was a retrospective analysis of 578 singletonpregnancies with diagnosis of intrauterine growth restriction (IUGR), delivered in a single obstetric unit, at the Spedali Civili, Brescia, Italy, a university and teaching hospital with 3500 deliveriesa year and neonatal intensive care unit (NICU).Methods: During 1991-99 we studied 578 pregnancies with a diagnosis of IUGR referred for Doppler velocimetry. From this population, four subsetswere formed: normal umbilical artery pulsatility index (NUAPI; 334 fetuses); increased pulsatility index but with telediastolic flow (abnormal umbilical artery pulsatility index AUAPI; 137 fetuses); absentend-diastolic flow (AEDF; 70 fetuses); reverse telediastolic flow (RF; 37 fetuses). Fetal biometry, amniotic fluid and fetal-maternal Doppler velocimetry were evaluated in all patients, with biophysicalprofile and routine non-stress test, when indicated. The following outcomes were examined: mean gestational age at delivery, number of preterm deliveries (< 34 weeks), mean neonatal weight, Apgar scoreat 5 min < 7, prenatal and neonatal deaths (within the first 28 days of life), admission to the NICU and number of days spent after birth in hospital. Neonatal morbidity was analyzed, including respiratorydistress syndrome (RDS), intraventricular hemorrhage (IVH, grade 2-3), necrotizing enterocolitis (NEC) and retinopathy of prematurity. Long-term neurological follow-up is still ongoing and will not be presentedin this paper.Results: Out of 578 fetuses with IUGR, 547 were born alive. There were 26 neonatal deaths. The mean gestational age at delivery was 35.6 ± 4 weeks and mean birth weight1844 ± 612 g. There were 28 intrauterine deaths and three elective terminations of pregnancy. A total of 60 cases (11%) were complicated by RDS, 13 cases (2.4%) by retinopathy of prematurity, IVHwas present in nine cases (1.6%) and NEC in seven cases (1.3%). Total perinatal mortality was 9.8%; in the 26 cases of neonatal death, the mean week at delivery was 29.6 ± 4 with a mean weight of840 ± 425 g. Patients with NUAPI had a mean week at delivery of 37 ± 3, those with AUAPI delivered at 34 ± 3.2, those with AEDF delivered at 31 ± 3 and those with RF deliveredat 29 ± 2 weeks. In progressively worsening umbilical velocimetry, we observed an increase of incidence of low Apgar score. Days of admission to the NICU and incidence of perinatal mortality increasedwith the worsening of Doppler velocimetry.Conclusions: Our study underlines the existence of a strict correlation between umbilical Doppler velocimetry and an increased incidence of perinatalcomplications in IUGR fetuses.

Multicenter screening for pre-eclampsia and fetal growth restriction by transvaginal uterine artery Doppler at 23 weeks of gestation.

To determine the value of transvaginal color Doppler assessment of the uterine arteries at 23 weeks of gestation in predicting the subsequent development of pre-eclampsia and fetal growth restriction. Women with singleton pregnancies attending for routine ultrasound examination at 23 weeks in any one of seven hospitals underwent Doppler assessment of the uterine arteries. The presence of an early diastolic notch in the waveform was noted, and the mean pulsatility index of the two arteries was calculated. Screening characteristics in the prediction of pre-eclampsia and the delivery of a low birth-weight infant were calculated. Doppler examination of the uterine arteries was attempted in 8335 consecutive singleton pregnancies, satisfactory waveforms were obtained from both vessels in 8202 (98.4%) cases and complete outcome data were available in 7851 (95.7%) of these. The mean gestational age was 23 (range, 22-24) weeks. The mean uterine artery pulsatility index did not change significantly with gestation (r = -0.0078; P = 0.483); the median value was 1.04 and the 95th centile was 1.63. In 9.3% of cases early diastolic notches in the waveform from both uterine arteries were present and in an additional 11.1% of cases there were notches unilaterally. Pre-eclampsia with fetal growth restriction occurred in 42 (0.5%) cases, pre-eclampsia without fetal growth restriction in 71 (0.9%) and fetal growth restriction without pre-eclampsia in 698 (8.9%). The sensitivity of increased pulsatility index above the 95th centile (1.63) for pre-eclampsia with fetal growth restriction was 69%, for pre-eclampsia without fetal growth restriction was 24%, for fetal growth restriction without pre-eclampsia was 13%, for pre-eclampsia irrespective of fetal growth restriction was 41% and for fetal growth restriction irrespective of pre-eclampsia was 16%. The sensitivity of fetal growth restriction defined by the 5th rather than the 10th centile was higher (19% vs. 16%). The sensitivity for both pre-eclampsia and fetal growth restriction was inversely related to the gestational age at delivery; when delivery occurred before 32 weeks, the sensitivity for all cases of pre-eclampsia with fetal growth restriction, pre-eclampsia without fetal growth restriction and fetal growth restriction without pre-eclampsia increased to 93%, 80% and 56%, respectively. The sensitivity of bilateral notches in predicting pre-eclampsia and/or fetal growth restriction was similar to that of increased pulsatility index but the screen-positive rate with notches (9.3%) was much higher than that with increased pulsatility index (5.1%). A one-stage color Doppler screening program at 23 weeks identifies most women who subsequently develop severe pre-eclampsia and/or fetal growth restriction.

Relationship between fetal pulmonary artery blood flow velocity waveform and fetal lung length in pregnancies complicated by oligohydramnios

Objectives: The objective of this study is to evaluate weather there is a correlation between Doppler velocity waveform parameters obtained from fetal pulmonary artery and fetal lung length considered as one of the lung hypoplasia risk parameters in pregnancies complicated by oligohydramnios.Methods: A total of 35 singleton pregnancies between 26 and 39 weeks complicated by oligohydramnios due to premature rupture of the membranes, placental insufficiency or idiopathic etiology and 69 normal pregnancies were examined by real time ultrasonography, color and pulse Doppler. Pulse Doppler signal was obtained from the distal part of right or left pulmonary artery after visualization with color Doppler at the level of four chamber view. The systolic to diastolic ratio, resistance index and pulsatility index were used to quantify velocity waveforms. The right lung of the fetus was measured longitudinally from the apex next to clavicle to the base at the top of diaphragm. The results of fetal lung length measurements were compared with namogram given by Roberts.Results: Statistically significant difference in distal pulmonary artery pulsatility index between normal pregnancies (1.74 ± 0.23) and pregnancies complicated by oligohydramnios (2.72 ± 0.56) with decreased value of fetal lung length (below fifth percentile) was observed. The sensitivity, specificity, positive and negative predictive value of 95, 91, 93, 91%, respectively, were obtained. In the group with oligohydramnios and normal values of fetal lung length, the difference in pulsatility index in comparison with normal pregnancies was not significant. No differences in systolic to diastolic ratio and resistance index between examined groups were found.Conclusions: Strong relationship between increased pulsatility index value obtained from distal part of pulmonary artery and decreased value of fetal lung length measurement in pregnancies complicated by oligohydramnios was observed. The measurement of pulmonary artery pulsatility index enriched with fetal lung length may give additional information useful in predicting pulmonary hypoplasia risk.

Arterial Doppler ultrasound in 115 second- and third-trimester fetuses with congenital heart disease.

To assess the influence of isolated congenital heart disease (CHD) on fetal arterial Doppler blood flow velocity waveforms. Doppler flow velocimetry was performed in the umbilical artery and middle cerebral artery in 115 consecutive fetuses with antenatally diagnosed CHD. Gestational age ranged between 19 and 41 weeks. Fetuses with isolated CHD were defined as group A (n = 55), showing cardiogenic hydrops fetalis in six cases; group B included 60 cases complicated by chromosomal or non-chromosomal extracardiac malformation, uteroplacental dysfunction or non-cardiogenic non-immune hydrops fetalis. The control group comprised 100 healthy fetuses of uncomplicated pregnancies. Individual pulsatility index measurements were converted into their Z-scores (delta values) for statistical analysis. In regard to the umbilical artery pulsatility index, 115 fetuses with CHD showed a significantly greater (P < 0.001) difference from the normal mean for gestation (delta values) than the control group. However, 29 of the 33 cases with indices above the 95% reference interval were additionally associated with extracardiac malformations, uteroplacental dysfunction or non-cardiogenic non-immune hydrops fetalis. While fetuses with isolated CHD still showed significantly higher values than healthy fetuses (P < 0.01), only in 4 of 55 (7%) fetuses did the measured umbilical artery pulsatility index exceed the 95% reference interval. There was no significant difference from the control group, in which 4 of 100 cases showed an umbilical artery pulsatility index above the 95% reference interval. Elevated umbilical artery pulsatility indices were seen in only four cases of severe obstruction of the outflow tracts leading to reverse perfusion of the affected great artery and in one case of Ebstein's anomaly with pulmonary insufficiency. Although all four fetuses with isolated CHD and elevated umbilical artery pulsatility index died, 14 of 18 fetuses with lethal outcome had normal pulsatility index values in the umbilical artery. Investigations of the middle cerebral artery blood flow revealed no significant difference between fetuses with and without CHD or any subgroups. This study shows that arterial blood flow velocity waveforms in fetuses with isolated CHD do not show sufficient alterations to be of diagnostic value. Only in severe outflow tract obstructions due to a 'steal effect' or in significant insufficiencies of semilunar valves leading to an impaired 'wind-kessel function' may the special hemodynamic changes induced by CHD result in a significant increase of pulsatility index in the umbilical artery. In the majority of cases with CHD the increase of pulsatility index of umbilical arterial blood flow velocity waveforms, however, results from extracardiac anomalies, especially uteroplacental dysfunction and chromosomal abnormalities. Furthermore, umbilical artery Doppler sonography is not clinically helpful in predicting fetal outcome.

P90Growth hormone and insulin‐ like growth factor 1, in small‐for‐gestational‐age pregnancies with increased pulsatility index in the umbilical artery

BackgroundThe aim of the study was to examine some endokrinological aspects of intrauterine growth retardation and, in particular, test whether low levels of GH and IGF‐1 in maternal serum are associated with direct evidence of placental dysfunction.MethodProspectively 48 singleton pregnancies with a SGA fetus and 28 with an AGA fetus were examined with maternal serum GH, IGF‐1, IGFBP‐1 and 3, and fetal weight and umbilical artery pulsatility index at 33 weeks of gestation.ResultsSerum IGF‐1 was lower in the SGA group, which was accounted for in the subgroup of SGA with increased pulsatility index.ConclusionA decreased maternal level of IGF‐1 seems to be specifically related to placental dysfunction as diagnosed by increased Doppler flow pulsatility

Aminophylline influences cerebral hyperperfusion after severe birth hypoxia.

Doppler sonographic investigations have presented cerebral hyperperfusion in neonates after severe asphyxia. Neonates with disturbed cerebral blood flow velocity (CBFV) tend to have poor outcomes. The purpose of this clinical study was to examine the influence of aminophylline on cerebral hyperperfusion. An intravenous bolus of 4 mg/kg aminophylline was given to nine neonates with Doppler sonographic signs of cerebral hyperperfusion. CBFV was determined before, 5 min, 60 min and 120 min after aminophylline administration and on the following day. After aminophylline the mean systolic (56.5 vs. 41.6 cm/s) and end diastolic (21.0 vs. 12.3 cm/s) blood flow velocity decreased and the mean pulsatility index (0.83 vs. 1.1) increased significantly. Repeated measurements showed a decrease in blood flow velocities and an increase in pulsatility index on the following days. Heart rate, mean arterial blood pressure and pCO2 were not significantly changed. We conclude that aminophylline influences cerebral hyperperfusion in neonates with disturbed autoregulation.

Blood flow changes in the ovarian and uterine arteries in women with normal and polycystic ovaries

This review summarizes the haemodynamic changes in the ovarian and uterine arteries, as revealed by transvaginal colour Doppler ultrasonography, (i) in women with normal ovaries (group 1), (ii) in women with the polycystic ovary syndrome who ovulate in response to clomiphene citrate (group 2) and (iii) in women with polycystic ovaries who have a regular ovulatory menstrual cycle (group 3). In each group blood flow velocities in the intraovarian arteries increased during the menstrual cycle in the dominant ovary and remained high in the mid-luteal phase. There was no significant change in pulsatility index. In group 2, the longitudinal haemodynamic changes in the intraovarian arteries were similar to those seen in women with normal ovaries. However, the follicular and ovarian stromal blood flow velocities were greater in group 2 compared with the normal group. There was a significant increase in the pulsatility index of the uterine artery during the follicular phase of the menstrual cycle and a subsequent decrease into the midluteal phase. Uterine artery pulsatility index was also significantly greater at the baseline ultrasound scan in group 2. In group 3, the longitudinal haemodynamic changes in the intraovarian arteries were similar to those in group 1. Furthermore, the intraovarian vascular changes were similar to those in group 2, but velocities were significantly greater than in group 1. There was an increase in uterine artery pulsatility index during the follicular phase of the menstrual cycle and a subsequent decrease into the mid-luteal phase. The uterine artery Doppler changes were similar to those seen in group 2. In conclusion, women with polycystic ovaries have significant differences in ovarian and uterine artery haemodynamics. Increased ovarian stromal blood flow within the polycystic ovary may help to explain the increased ovarian responsiveness that women with polycystic ovaries show after administration of gonadotrophins.

Pulmonary arterial Doppler velocimetry in fetuses with lung hypoplasia

Objective: The aim of the study was to examine Doppler flow velocity waveforms in the main stems of the pulmonary arteries in fetuses with autopsy-proven lung hypoplasia and to find out whether in these conditions typical patterns can be found. Study design: Doppler spectra were derived from the main stem of the right or left pulmonary artery in fetuses at high-risk for lung-hypoplasia. The following Doppler parameters were analyzed and compared to reference ranges: peak systolic velocity, acceleration time, time velocity integral, end-systolic reverse flow, pulsatility index (PI). Pulmonary hypoplasia was found in nine cases at autopsy after termination of pregnancy (19–23 weeks). According to etiology, three groups were considered: (A) bilateral renal malformations ( n=4), (B) congenital diaphragmatic hernia ( n=2), and (C) miscellaneous malformations including heart defects ( n=3). Results: The following Doppler parameters were found: normal values in end-systolic reversal flow in all cases, decreased peak systolic velocity and acceleration time in 3/9, decreased time velocity integral in 4/9 and increased pulsatility index in 6/9. Considering the etiology of pulmonary hypoplasia the pulsatility index was found to be the most sensitive, since all fetuses in groups A and B had an abnormal PI. Conclusions: Human fetuses with renal malformations and diaphragmatic hernia associated with lung hypoplasia show as early as 19–23 weeks of gestation an abnormal Doppler spectrum in the main stems of the pulmonary arteries. Increased PI is the best parameter to detect flow abnormality in this condition. Since the Doppler spectrum depends on cardiac anatomy and function, PI in lung hypoplasia seems to be reliable only when cardiac defects are absent.

Uterine ultrasonographic changes with gonadotropin-releasing hormone agonists

Objectives: Our purpose was to assess the changes in uterine volume and uterine artery pulsatility index in response to gonadotropin-releasing hormone agonist treatment in women undergoing hysterectomy for nonfibroid-related uterine bleeding. Study Design: A double-blind, placebo-controlled randomized trial of 51 women awaiting hysterectomy in a gynecology outpatient clinic was conducted. The women were treated for 8 weeks with either leuprolide acetate depot or placebo. Vaginal ultrasonographic examinations were performed before and after treatment. The paired t test was used for statistical analysis. Results: In those allocated to therapy with gonadotropin-releasing hormone agonist the mean uterine volume decreased by 34% and the uterine artery pulsatility index increased from 2.25 to 2.7. No significant changes were seen in the placebo group. The intersonographer variability was low and there was a high correlation between uterine size as measured by ultrasonography before hysterectomy and that measured postoperatively. Conclusions: Treatment with gonadotropin-releasing hormone agonists leads to uterine shrinkage and an increase in the uterine artery pulsatility index even in the absence of uterine fibroids. (Am J Obstet Gynecol 1999;180:8-13.)

Cerebral syncope: loss of consciousness associated with cerebral vasoconstriction in the absence of systemic hypotension.

Transcranial Doppler (TCD) ultrasonography done during head-upright tilt induced neurocardiogenic syncope has demonstrated that cerebral vasoconstriction occurs concomitant with (or precedes) loss of consciousness. This article demonstrates evidence that cerebral blood flow changes alone (vasoconstriction), in the absence of systemic hypotension, may result in syncope. Five patients (4 men, 1 woman; mean age 41 +/- 17 years) with recurrent unexplained syncope were evaluated by use of an upright tilt table test for 45 minutes with or without an infusion of low dose isoproterenol. TCDoppler ultrasonography was used to assess middle cerebral artery systolic velocity (Vs); diastolic velocity (Vd); mean velocity (Vm); and pulsatility index (PI = Vs = Vd/Vmean). Syncope occurred in five patients during the baseline tilt and in one patient during isoproterenol infusion. During tilt induced syncope, at an average mean arterial pressure of 89 +/- 16 mmHg, TCD sonography showed a 2% +/- 10% increase in systolic velocity; a 51% +/- 27% decrease in diastolic velocity; and a 131% +/- 87% increase in pulsatility index. One patient underwent continuous electroencephalographic recording during tilt, which demonstrated diffuse slow wave activity (indicating cerebral hypoxia) at the time of syncope concomitant with the aforementioned TCD changes in the absence of systemic hypotension. These findings reflect an increase in cerebrovascular resistance secondary to arteriolar vasoconstriction distal to the insonation point of the middle cerebral artery, that occurred concomitant with loss of consciousness and in the absence of systemic hypotension. We conclude that in some individuals abnormal baroreceptor responses triggered during orthostatic stress may result in a derangement of cerebral autoregulation leading to cerebral vasoconstriction with resultant cerebral hypoxia in the absence of systemic hypotension.

Increase in transcranial Doppler pulsatility index does not indicate the lower limit of cerebral autoregulation.

Transcranial Doppler pulsatility index was reported clinically to increase when cerebral perfusion pressure decreased, hypothetically marking the lower limit of cerebral autoregulation. We sought to investigate the relationship between pulsatility index, cerenbrovascular resistance, and cerebral perfusion pressure in various states of autoregulation in an animal model of moderate intracranial hypertension. Eight New-Zealand White Rabbits were studied with basilar artery blood flow velocity (ultrasound Doppler) and cortical blood flow (laser Doppler) monitored continuously during subarachnoid saline infusion to increase intracranial pressure (< 55 mm Hg). Four animals demonstrated a stable cortical blood flow, and four demonstrated decreasing blood flow when cerebral perfusion pressure decreased. Pulsatility index showed the same pattern of increase when cerebral perfusion pressure decreased, independent on whether cortical blood flow was stable or falling. The percentage rate of increase in the pulsatility index was not different in autoregulating and non autoregulating animals. The rate of decrease in cerebrovascular resistance was significantly lower (p < 0.05) in non-autoregulating than in autoregulating animals. The increase in transcranial Doppler pulsatility index when cerebral perfusion pressure falls cannot be interpreted as a phenomenon able to mark the lower limit of cerebral autoregulation.

Cerebrovascular and cardiovascular measurements during neurally mediated syncope induced by head-up tilt.

This study examines changes in systemic hemodynamics and in cerebral blood velocity that occur during neurally mediated syncope (NMS) to determine whether cerebral autoregulation is intact or impaired in patients with recurrent NMS. Beat-to-beat recordings of heart rate, blood pressure (volume clamp photoplethysmography), stroke volume (impedance cardiography), and right middle cerebral artery blood velocity (transcranial Doppler sonography) were performed at rest and during 80 degrees head-up tilt. Twelve patients with NMS and 10 healthy control subjects were studied. Baseline values and the initial response to head-up tilt of control subjects and patients with NMS were similar. The mean latency to onset of syncope was 11.8 +/- 11.1 minutes. At syncope, heart rate, systolic and diastolic blood pressure, and diastolic cerebral blood velocity decreased significantly, whereas systolic cerebral blood velocity did not change. Calculated cerebrovascular resistance was significantly reduced from 1.85 +/- 0.60 to 1.32 +/- 0.27 mm Hg/cm per second, whereas the pulsatility index increased from 0.92 +/- 0.16 to 1.52 +/- 0.21. We never observed a change in cerebral blood velocity before the rapid decline in blood pressure, nor did we observe any significant change in respiratory pattern. The decrease in cerebrovascular resistance during NMS indicates that the integrity of cerebrovascular autoregulation is maintained even when syncope is imminent. The selective loss of diastolic flow during syncope and the increase in pulsatility index are likely caused by collapse of downstream vessels as diastolic blood pressure decreases below the critical closing pressure of cerebral vessels.

Évaluation du retentissement ischémique de l'hypertension intracrânienne

The main risk involved in severe intracranial hypertension is, the occurrence of cerebral ischaemia, either locally during herniation or globally as a consequence of reduced cerebral perfusion pressure (CPP). Neurological features of ischaemia occur at a late stage. A continuous monitoring of brain function with EEG or evoked potential techniques, while largely used in the operating room have not been so far fully evaluated in the intensive care setting. Therefore, ischaemic criteria based on the registration of haemodynamic or metabolic data are gaining importance in management of increased intracranial pressure (ICP). Transcranial Doppler of middle cerebral arteries allows at any time the detection of a decrease in brain perfusion. An increased pulsatility index has been repeatedly demonstrated to correlate with decreased CPP. From these reports, the lower limit of autoregulation in brain injured patients appears to be much higher (70 mmHg) than previously estimated (40 mmHg). However, therapies with a cerebral vasoconstrictor impact and associated vasospasm are to be considered for a correct interpretation of Doppler data. Moreover, as a reduced cerebral blood flow is not necessarily insufficient to meet metabolic requirements, a routine insight in cerebral oxygenation and lactate production must be available. Continuous monitoring of jugular blood oxyhaemoglobin saturation (SjO2) measures the reserve of oxygen extraction and a decrease in SjO2 below 50% is considered as to indicate an impending cerebral ischaemia. Indeed, critically reduced CPP under a 70 mmHg limit is reflected by venous desaturation episodes. Increased cerebral lactate production, routinely appraisable by serial measurements of [(a-v) lactate], may afford confirmation of an existing ischaemia. ICP and CPP monitoring remains the basis for intensive care surveillance during the phase of intracranial hypertension, with alarming settled at admitted critical values (ICP = 30 mmHg; CPP = 70 mmHg). As ischaemic threshold for cerebral blood flow may be different in patients and in normal experimental animals, the reliability of these critical values of ICP and CPP is uncertain. Therefore, transcranial Doppler, jugular metabolic monitoring and, as recently available, cortical tissue PO2 monitoring are mandatory for early detection and assessment of ischaemia.

Prädiktive Wertigkeit dopplersonographisch gemessener uteroplazento-fetaler Perfusion bei drohender Frühgeburt

Premature Labour as Measured by Doppler Ultrasound: In a prospektive study, 114 pegnant women with premature labour were examined by Doppler ultrasound. The pulsatility indices (PI) of the uterine arteries, the umbilical artery, the fetal descending thoracic aorta and the middle cerebral artery were measured, both on admission and again after 2 weeks of tocolytic therapy (n = 59). An increased pulsatility index in the uterine arteries correlated significantly with a decreased gestational age at birth, decreased ability to delay birth, decreased birth weight and decreased percentiles for gestational age. There was also an increase in adverse fetal outcomes as shown by a fetal outcome score which included preterm birth, hypotrophy, fetal hypoxia, fetal acidosis and impaired neonatal adaptation. Neither the PI values for the fetal vessels nor the combination of uterine and fetal perfusion showed any correlation with fetal outcome. Pathological PI values in the uterine and umbilical arteries cannot predict premature births or other parameters of adverse fetal outcome with enough certainty as a sensitivity of max. 50% and a positive predictive value of max. 65% show. A specificity of 70-95% and a negative predictive value of 51-96% indicate that in all probability a normal course can be expected for pregnancy and birth if the PI values are normal in threatened premature labor. The combination of uterine and fetal perfusion values in a Doppler score does not improve the prognostic value. We conclude that in premature labour, Doppler findings alone are not enough to make a reliable statement about the prognosis and therefore about the further management of the pregnancy. The multifactorial aetiology of premature birth also points to a multifactorial assessment of prognosis.

Exaggerated effects of progestogen on uterine artery pulsatility index in Turner’s syndrome patients receiving hormone replacement therapy

To investigate the effect of estrogen and progestogen on the resistance to blood flow in the uterine arteries of Turner's syndrome patients. Prospective clinical study. A tertiary infertility clinic. Five Turner's syndrome patients, six patients who had surgical castration, and five patients with idiopathic primary ovarian failure. The patients were treated with 2 mg E2 valerate to which 500 micrograms norgesterel was added for 10 days in a 28-day cycle. Transvaginal color Doppler was used to measure pulsatility index in the uterine arteries at eight regular intervals during a single cycle. Pulsatility index of the uterine arteries. The administration of norgesterel to Turner's syndrome patients resulted in an increase in pulsatility index that was significantly higher than in patients who had surgical castration (confidence interval = 0.17 to 2.42). The uterine arteries of Turner's syndrome patients are more sensitive to the tonic effect of progestogen. If manifest in cardiac arteries also this phenomenon may be partly responsible for the increased incidence of cardiovascular disease and shorter life expectancy in Turner's syndrome patients. To achieve optimal protection from cardiovascular disease, Turner's syndrome patients may benefit from hormone replacement treatment containing altered doses of estrogen and progestogen.