Search PubMed⌕ Search

Biomedical subjects

B J Trudinger

Publications and source records attributed to B J Trudinger.

At least 55 records · Page 3Linked to original sources
PubMed1988

Different umbilical artery flow velocity waveforms in one patient.

Serial studies of umbilical artery flow velocity waveforms in one patient revealed two quite distinct waveforms at each study. The mean systolic/diastolic ratio difference between the studies was 2.2 units. After delivery, the placenta was seen to include a large infarcted lobule supplied by only one of the umbilical arteries. The finding of two very dissimilar umbilical artery flow velocity waveforms at the time of study should raise the suspicion of placental infarction, but management decisions should be based on the most normal study.

Adult↗
PubMed1987

Umbilical artery flow velocity waveforms in high-risk pregnancy. Randomised controlled trial.

300 patients at high fetal risk (mean gestational age 34 wk) were randomised to a group for antenatal doppler umbilical artery waveform studies and a control group. The timing of delivery was similar in the control and doppler-report-available groups overall. However, in the report group obstetricians allowed the pregnancies of those not selected for elective delivery to continue longer. There was no difference in the rates for elective delivery (induction of labour or caesarean section) in the two groups, whereas among those who went into labour (induced or spontaneous) emergency caesarean section was more frequent in the control group (23%) than in the report group (13%). Fetal distress in labour was also more common in the control group. Babies from the control group spent longer in neonatal intensive care (level 3) and needed more respiratory support than did those in the report group. The findings indicate that the availability of doppler studies leads to better obstetrical decision making.

Blood Flow Velocity↗
PubMed1987

Umbilical artery flow velocity waveforms and placental resistance: the effects of embolization of the umbilical circulation.

Embolization of the umbilical placental circulation in fetal lambs was carried out to occlude the small vessels of the placental vascular bed and to observe the effect on the umbilical artery flow and flow velocity waveforms. Thirteen singleton fetuses were studied from day 120 of pregnancy. Embolization was achieved by injecting approximately 9 X 10(6) microspheres of 15 micron diameter into the fetal placental cotyledons along the umbilical arteries over 9 days. Umbilical and uterine flows were measured by radioactive microsphere counting. The umbilical placental resistance was increased (0.25 to 0.35 mm Hg.ml.min-1) by embolization, and there was an increase in the umbilical artery systolic/diastolic ratio. Embolization produced a significant fall in umbilical flow expressed either as total flow (312 to 237 ml.min-1) or when normalized by reference against splanchnic flow (3.36 to 1.53). We conclude that the umbilical artery flow velocity waveform systolic/diastolic ratio measures the reflection coefficient at the peripheral vascular bed (the "resistance vessels") of the placenta.

Animals↗
PubMed1987

The effect of epidural anaesthesia for caesarean section on maternal uterine and fetal umbilical artery blood flow velocity waveforms.

The blood flow resistance in the maternal uteroplacental and fetal umbilical artery circulation was studied in eight otherwise normal patients undergoing elective lower segment caesarean section. The systolic/diastolic A/B ratio (the ratio of peak systolic to least diastolic flow velocity) for the uteroplacental and fetal umbilical circulation was determined from the artery blood flow velocity-time waveform and used as an index of blood flow resistance. Each patient received a 1 litre intravenous crystalloid infusion before an epidural bupivicaine injection. Both crystalloid infusion and epidural anaesthesia resulted in a significant decrease in the maternal uteroplacental systolic/diastolic (A/B) ratios, associated with a decrease in fetal umbilical artery A/B ratio. This study suggests a beneficial fetal effect from the improved maternal uterine perfusion after epidural anaesthesia.

Anesthesia, Epidural↗
PubMed1987

A survey of the management of premature labour by Australian obstetricians.

A survey of the practices of obstetricians in the management of premature labour was carried out. A questionnaire consisting of 16 clinical problems was drawn up. All Fellows and Members of the RACOG resident in Australia were surveyed by mail and 707 (74.3% of those in active practice) returned completed questionnaires. Results were analysed by State, seniority and practice size. The survey revealed many differences in management even in situations tested by clinical trials (e.g. premature rupture of membranes, use of steroids). There was uncertainty about when to attempt inhibition with tocolytics. Obstetricians had a more pessimistic view concerning neonatal survival than recent published neonatal results indicate. The role of chorioamnionitis seemed undervalued. There were many differences when results were analysed by State and seniority.

Adrenergic beta-Agonists↗
PubMed1986

A comparison of Doppler ultrasound waveform indices in the umbilical artery--I. Indices derived from the maximum velocity waveform.

Various Doppler waveform indices have been used for assessment of the fetal circulation. Comparisons were made to show what relations exist between the indices, and to identify any differences or difficulties which might arise from using one as opposed to another in clinical practice. Both normal pregnancy and cases of fetal growth failure were studied. Indices were obtained from the maximum velocity envelope of the umbilical artery waveform using a curve fitting technique. The values were very reproducible for all indices. The FHR, which varied over the entire normal range, did not significantly affect the values of any index. The downstream impedance indices calculated included the AB ratio, pulsatility index (PI) and Pourcelot ratio. These all gave very closely correlated results for normals but discrepancies occurred in the at risk group, where values were elevated. This could be attributed to differences in the underlying distributions. The indices suggested for cardiac contractility were not as closely related to each other, and moreover the differences between them showed no clear pattern. None of the indices varied independently of the others. The rising slope, which is by definition related to the PI, was more highly correlated with the downstream indices than the relative flow rate index.

Blood Flow Velocity↗
PubMed1986

A comparison of Doppler ultrasound waveform indices in the umbilical artery--II. Indices derived from the mean velocity and first moment waveforms.

Umbilical artery Doppler recordings in both normal pregnancy and cases of fetal growth failure were processed by computer. Representative waveforms for the maximum velocity, mean velocity and first moment were obtained after ensemble averaging and correction for thump filtering. The same set of indices, which included the AB ratio, pulsatility index, rising slope and relative flow rate index, were calculated for each of the waveforms. The results were compared to identify differences which might arise in clinical practice if a waveform other than the usual (maximum velocity) was used. The ratio of the mean to the maximum velocity, which gives an indication of the velocity profile, was shown to be very error prone. The reproducibility of the mean velocity and first moment indices was inferior to that of the maximum velocity indices. The results from the different waveforms were highly correlated for normals for most indices. However, in the growth retarded group there was a tendency for the mean velocity and first moment indices to classify as normal studies classified as abnormal by the maximum velocity index. The values of indices derived from the first moment waveform were generally larger than the maximum and mean velocity values. For the relative flow rate index, where results were often different to the general trend, the values were more nearly equal.

Blood Flow Velocity↗
PubMed1986

A comparison of fetal heart rate monitoring and umbilical artery waveforms in the recognition of fetal compromise.

Antenatal fetal heart rate monitoring was compared with the study of umbilical artery flow velocity waveforms for the recognition of fetal compromise in 170 patients considered at high fetal risk. In 53 patients the infant had a 5-min Apgar score of less than 7 and/or a birthweight less than 10th centile of weight for gestation. Fetal heart rate traces were classified as reactive or non-reactive and also assessed with a modified Fischer score. The systolic/diastolic A/B ratio was measured in the umbilical artery waveform. Fetal compromise was more efficiently recognized by study of the umbilical artery waveforms. The sensitivity of assessment by umbilical artery waveforms was 60% compared with 17% and 36% respectively, for the two methods of scoring fetal heart rate traces. This was not associated with an increase in false-positive results as the predictive value of both positive (64% compared with 69 and 58%) and negative (83% compared with 72 and 75%) results was similar when umbilical artery waveform analysis was compared with the two methods of scoring fetal heart rate traces. Specificity was also similar (85% compared with 97 and 88%).

Blood Flow Velocity↗
PubMed1986

Fetal volume blood flow and umbilical artery flow velocity waveform analysis: a comparison.

The estimation of fetal umbilical vein and aortic volume blood flow was compared with umbilical artery flow velocity-time waveform analysis in 42 pregnancies. The volume blood flow measurements were made with a combined linear array B-mode and pulsed Doppler ultrasound system. The umbilical artery flow velocity-time waveform analysis was made with either pulsed or continuous wave 2 MHz Doppler ultrasound and the systolic/diastolic (A/B) ratio was used as an index of flow resistance. There was no difference when continuous wave was compared to pulsed Doppler ultrasound as a method of recording flow velocity waveforms. Analysis of the umbilical artery flow velocity-time waveform was more sensitive (100%-50%) than the measurement of umbilical vein volume blood flow (ml/kg/min) in the detection of the small-for-gestational age (SGA) fetus. The predictive value of a positive test was higher (71%-45%) while specificity was similar (88%-81%). Descending aortic volume flow was reduced in only one SGA fetus. The increase in umbilical placental downstream resistance (high systolic/diastolic ratio) was associated with a reduction in the percentage of fetal aortic blood flow directed to the umbilical placental circulation.

Adult↗
PubMed1986

Umbilical cord whole blood viscosity and the umbilical artery flow velocity time waveforms: a correlation.

The possibility was examined of an association between umbilical cord whole blood viscosity and umbilical artery flow velocity time waveforms obtained with continuous wave Doppler ultrasound. The cord blood viscosity was measured at both high (100 s-1) and low (0.1 s-1) shear rates with a concentric cylinder viscometer. Plasma viscosity and fibrinogen were also measured. An abnormal pattern in the umbilical artery flow velocity waveform (high A/B ratio) indicative of high resistance was associated with an increase in whole blood viscosity at high shear (which may reflect a change in red cell rigidity). Viscosity at low shear (reflecting red cell aggregation and rouleaux formation) did not differ. There was a significant association between the small-for-gestational age fetus and abnormal umbilical artery waveform study (P less than 0.002) but not abnormal whole blood viscosity at high (P = 0.09) or low (P = 0.08) shear.

Blood Flow Velocity↗
PubMed1985

Flow velocity waveforms in the maternal uteroplacental and fetal umbilical placental circulations.

A simple continuous-wave Doppler ultrasound system was used to record arterial flow velocity time waveforms from branches of the maternal uterine artery in the placental bed and the fetal umbilical arteries. The systolic-diastolic ratio of flow velocities was measured as an index of peripheral resistance. In normal pregnancy both circulations exhibit high diastolic flow velocities caused by low resistance. The study group consisted of 172 pregnancies with high fetal risk of which 53 resulted in delivery of a small-for-gestational age infant. The last study-to-delivery interval was less than 10 days. In the small-for-gestational age fetuses in whom both umbilical and uterine studies were normal there was good fetal outcome (19 cases). Neonatal morbidity occurred among those with abnormal umbilical studies with low diastolic flow velocities, indicating high resistance. Of these studies there were two subgroups. An abnormal uterine study (13 cases) indicated a primary maternal uteroplacental lesion and a normal study (21 cases) a primary fetal lesion. In cases of severe maternal hypertension, abnormal uterine artery waveforms were associated with abnormal umbilical artery waveforms.

Adult↗
PubMed1985

Umbilical waveforms in twin pregnancy.

Continuous wave Doppler ultrasound was used to study the twin fetus in 76 multiple pregnancies. The technique is not difficult and allowed the identification of the small for gestational age twin in both intrauterine growth failure and twin to twin transfusion syndrome.

Birth Weight↗
PubMed1985

Fetal umbilical artery flow velocity waveforms and placental resistance: clinical significance.

Since the umbilical arteries carry fetal blood to the placenta we studied flow velocity waveforms in these vessels with a simple continuous wave Doppler system to assess placental blood flow. The ratio of peak systolic to least diastolic (A/B) flow velocity was measured as an index of placental flow resistance. In 15 normal pregnancies there was a small but significant decrease in this ratio through the last trimester. The A/B ratio was measured on 436 occasions in 168 high-risk pregnancies. In 32 of 43 fetuses subsequently shown to be small for gestational age there was an increase in placental flow resistance with reduced, absent or even reversed flow in diastole. This finding was also present in the one fetus which died in utero. Serial studies in patients with fetal compromise indicated increasing flow resistance, a reverse of the normal trend. These results were not available to the clinician yet of 24 fetuses born before 32 weeks 13 had a high A/B ratio, and all of them were born electively. Maternal hypertension was associated with an increase in fetal placental flow resistance. The umbilical artery A/B ratio provides a new and non-invasive measure of feto-placental blood flow resistance.

Adult↗
PubMed1985

Fetal umbilical artery flow velocity waveforms and placental resistance: pathological correlation.

Placental microvascular anatomy was correlated with antenatal assessment of the umbilical circulation in 106 patients to further validate the measurement of the A/B ratio (the ratio of peak systolic to least diastolic flow velocity) of the umbilical artery flow velocity time waveforms as an index of blood flow resistance. Three groups of patients were studied: a normal group of 38 uncomplicated pregnancies, a control group of 33 potentially 'at risk' pregnancies with a normal A/B ratio matched by risk factors and gestation with the third group of 35 pregnancies with a high A/B ratio. Placental arterial resistance was quantitated by counting the number of small muscular arteries (less than 90 micron diameter) in the tertiary stem villi in a standard microscopic field (mean 18.5 fields/placenta). The modal small arterial vessel count was shown to be significantly less in the group with a high fetal risk and a high A/B ratio (1-2 arteries/field) than in both the normal and control groups (7-8 arteries/field). The tertiary villus count did not vary between groups. Antenatal studies of umbilical artery flow velocity waveforms with Doppler ultrasound identify a specific microvascular lesion in the placenta characterized by obliteration of small muscular arteries in the tertiary stem villi.

Arteries↗
PubMed1985

Uteroplacental blood flow velocity-time waveforms in normal and complicated pregnancy.

A simple continuous wave Doppler ultrasound system for recording arterial flow velocity waveforms in branches of the uterine artery in the placental bed is described. Twelve normal pregnancies were studied serially from 20 weeks to delivery. The diastolic flow velocity expressed as a percentage of the systolic provides an index of downstream vascular bed resistance and perfusion. This always exceeded 50% in normal pregnancy and there was a small increase with gestational age indicative of a decreasing flow resistance. Of the 91 complicated pregnancies, studied because of potential uteroplacental insufficiency and fetal risk, 25 resulted in the birth of an infant small-for-gestational-age. In 15 the uterine artery flow velocity waveform revealed a pattern of low diastolic flow velocity. It is postulated that these represent a subgroup of growth-retarded fetuses in whom there is reduced uterine artery perfusion. Reduced uterine artery diastolic flow velocity in these patients was associated with reduced umbilical artery diastolic flow velocity on the fetal side of the placenta. In contrast the 10 small-for-gestation infants associated with normal uterine artery waveforms suggest a primary fetal cause. Twelve patients with severe hypertensive disease of pregnancy were studied. Nine were associated with reduced uterine artery diastolic flow velocity (reduced uterine artery perfusion) consistent with vasospasm in the branches of the uterine artery in the placental bed.

Arteries↗
PubMed1985

Fetal umbilical artery flow velocity-time waveforms in twin pregnancies.

The umbilical artery flow velocity-time waveforms were studied in 76 twin pregnancies. The ratio of peak systolic (A) to least diastolic (B) velocity was calculated for each fetus as an index of umbilical placental flow resistance. Seventy-one sets of twins were studied within 14 days before delivery. In 65 cases both twins were alive at the time of study. In 32 pregnancies both fetuses were of birthweight appropriate for gestational age (AGA) and had A/B ratios within the normal singleton range. In 33 pregnancies one or both of the liveborn infants were small for gestational age (SGA) and in 78% of these at least one fetus had an elevated A/B ratio. Discordancy in birthweight and A/B ratio was associated with growth retardation. Clinically manifest twin-to-twin transfusions occurred in five of the ten pregnancies resulting in an SGA infant (eight with discordant weight) associated with a normal and concordant A/B ratio. Two twin-to-twin transfusions were associated with perinatal death. The placentas were examined in 61 patients. In 43 dichorionic pairs the A/B ratio was elevated in 12 of the 18 where there was at least one SGA infant. There was a greater incidence of growth retardation in the monochorionic pairs (12 of 18). Only seven of these were identified by an elevated A/B ratio. In 10 of these 18 pairs vascular anastomoses were demonstrated on placental inspection and in a further two there was evidence of twin-to-twin transfusion by haemoglobin discrepancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Birth Weight↗