Hydrostatic and osmotic pressure gradients produce manifestations of fetofetal transfusion syndrome in a computerized model of monochorial twin pregnancy

OBJECTIVE

In spite of recent advances in the assessment and treatment of fetofetal transfusion syndrome, its underlying mechanism remains controversial. We aimed to determine whether the clinical features of fetofetal transfusion syndrome could be explained by unidirectional or bidirectional intertwin transfusion along placental vascular anastomoses.

STUDY DESIGN

We constructed a dynamic computerized model of monochorial twin fetoplacental units on the basis of numerous interrelated hemodynamic, osmotic, and metabolic physiologic variables. The circulations were then linked by various combinations of direction and number of arteriovenous anastomoses.

RESULTS

With unidirectional anastomoses disease severity, characterized by disparity in blood solids, depended on donor arterial pressure but not on the number of anastomoses. In the chronic state water movement resulting from raised osmotic pressure in the recipient and reduction in the donor produced hydroosmotic pressure equilibrium, reducing anastomotic flow to near zero. Atrial natriuretic peptide-driven urine production was markedly increased in the recipient because of the raised vascular hydrostatic pressure component. With bidirectional anastomoses recirculation between twins reduced discordancy in colloids and hematocrit, and the clinical picture was determined by the degree of asymmetry in the number of connections.

CONCLUSIONS

Severe manifestations of fetofetal transfusion syndrome can be explained by unidirectional intertwin transfusion and lesser degrees by asymmetric bidirectional transfusion.

Discordant blood flow velocity waveforms in left and right brachial arteries in growth-retarded fetuses

OBJECTIVE

To determine if the increase in cerebral blood flow ("brain-sparing" effect) with fetal hypoxemia is associated with discordant hemodynamics in the upper extremities.

METHODS

We studied 12 fetuses with severe growth retardation, absent or reverse end-diastolic blood flow in the umbilical artery, and low pulsatility index (PI) in the middle cerebral artery, and 12 appropriately grown control fetuses with normal fetoplacental Doppler studies. The right and left brachial arteries were identified by high-resolution color Doppler ultrasonography, and the PI was measured in each brachial artery.

RESULTS

All growth-retarded fetuses had lower impedance indices in the right than in the left brachial artery (mean delta PI 1.0, 95% confidence interval [CI] 0.7-1.3, P < .001). No differences in the brachial artery impedance indices were found in control fetuses matched for gestational age (mean delta PI 0.0, 95% CI -0.2 to 0.2).

CONCLUSIONS

Left and right brachial artery blood flow velocity waveforms are discordant in fetuses with growth retardation and cerebral vasodilation. Because the right arm receives its blood supply from the same source as the brain (brachiocephalic artery) and given the proximity of the left subclavian artery to the ductus arteriosus, we speculate that this might be the result of increased blood flow into the brachiocephalic circulation and/or functional differences in the distribution of left and right ventricular output within the aortic arch in response to fetal hypoxemia.

Follicular fluid levels of midazolam, fentanyl, and alfentanil during transvaginal oocyte retrieval

OBJECTIVE

To investigate the time course of changes in follicular fluid (FF) concentrations of midazolam (Roche Products Ltd., Welwyn Garden City, United Kingdom), fentanyl (Janssen Pharmaceuticals Ltd., Wantage, United Kingdom), and alfentanil (Janssen Pharmaceuticals Ltd.) during ultrasound-guided transvaginal oocyte collection.

STUDY DESIGN

Forty-five patients with tubal infertility were randomized to receive a bolus IV dose of midazolam, fentanyl, or alfentanil for sedation during ultrasound-guided transvaginal oocyte collection. Paracervical block with lignocaine was given for analgesia. Simultaneous blood and FF samples were drawn at 5-minute intervals after the bolus dose for analysis of drug levels.

RESULTS

Data were obtained on 15 women receiving midazolam and fentanyl and on 13 women receiving alfentanil. Plasma levels of all agents rose to a peak and then fell in an exponential fashion as was expected. The FF levels of the agents continued to rise significantly to 25 minutes after the bolus dose, although the absolute level was low when compared with the blood level. There were no significant differences in fertilization or pregnancy rates in the three groups, but patient numbers were small.

CONCLUSION

We conclude that midazolam, fentanyl, and alfentanil are found in FF after a single IV dose, but further investigation needs to be undertaken to investigate any potential influence on fertilization and implantation rates.

Acute maternal hydration in third-trimester oligohydramnios: effects on amniotic fluid volume, uteroplacental perfusion, and fetal blood flow and urine output

OBJECTIVE

Our purpose was to determine whether acute maternal hydration in pregnancies with third-trimester oligohydramnios (1) increases amniotic fluid index and hourly fetal urine production rate and (2) alters uteroplacental perfusion and fetal blood flow.

STUDY DESIGN

Ten women with third-trimester oligohydramnios (amniotic fluid index < or = 5 cm) and 10 controls with normal amniotic fluid volume (amniotic fluid index > 7 cm) were prospectively recruited for this study. Maternal plasma and urine osmolality, amniotic fluid index, hourly fetal urine production rate, and Doppler flow velocimetry of maternal uterine artery and fetal umbilical, descending aorta, middle cerebral, and renal arteries were determined before and after oral hydration by having the patient drink 2 L of water over 2 hours.

RESULTS

There was a significant reduction in maternal plasma (p < 0.05) and urine osmolality (p < 0.0001) in both groups after short-term oral hydration. Hydration increased amniotic fluid volume in women with oligohydramnios (mean change in amniotic fluid index 3.2 cm, 95% confidence intervals 1.1 to 5.3; p < 0.02) but not in those with normal amniotic fluid volume (mean change in amniotic fluid index -2.0, 95% confidence intervals -4.1 to +0.2). The hourly fetal urine production rate, however, did not increase in either group (mean change in hourly fetal urine production rate 3.5 ml/hr, 95% confidence intervals -11.7 to +18.7 and -6.8 ml/hr, 95% confidence intervals -2.9 to -10.7, respectively). Hydration was associated with an increase in uterine artery mean velocity in the oligohydramnios group (mean change in mean velocity 16.7 cm/sec, 95% confidence intervals 8.0 to 25.3; p < 0.006) but not in controls (mean change in mean velocity 1.2 cm/sec, 95% confidence intervals -19.7 to +22.1). There was no change in pulsatility index or in velocity in any of the fetal vessels studied in either group.

CONCLUSIONS

Short-term maternal oral hydration increases the amniotic fluid index in women with third-trimester oligohydramnios. Although the mechanism for this effect remains unclear, it could not be accounted for by fetal urination in this study but instead was associated with improved uteroplacental perfusion.

Ablation of acardiac twin by alcohol injection into the intra-abdominal umbilical artery

BACKGROUND

Twin reversed arterial perfusion sequence is a rare complication of monochorionic twinning, in which the normal pump twin perfuses the abnormal acardiac twin in a reversed fashion via an artery-to-artery placental anastomosis. Mortality in the normal twin exceeds 50% as a result of preterm labor, polyhydramnios, and congestive heart failure.

CASE

A twin pregnancy complicated by the twin reversed arterial perfusion sequence developed early hemodynamic decompensation in the pump twin with increasing size of the acardiac twin. Ablation of the acardiac twin at 23 weeks' gestation was achieved successfully by injecting 1 mL of absolute alcohol into the intra-abdominal portion of the single umbilical artery.

CONCLUSION

Direct ultrasound-guided intravascular injection of absolute alcohol is an easy and straightforward technique to occlude circulation to the acardiac twin. This vessel can be identified easily by color Doppler ultrasonography away from the main venous trunk. Selection of this target, rather than occlusion at the level of the umbilical cord, could reduce the risks of cord accidents and inadvertent intravenous injection of the ablative material.

Early prenatal diagnosis of holoprosencephaly: the value of transvaginal ultrasonography

Holoprosencephaly is a rare condition characterized by different degrees of fused ventricles resulting from the failure of the prosencephalon to cleave during embryonic life. In this report we present a case of alobar holoprosencephaly diagnosed prenatally at 15 weeks' gestation in a woman with a family history of open neural tube defect. The diagnosis was initially missed because only suboptimal views of the fetal brain were obtained with transabdominal ultrasonography due to fetal position; however, a better depiction of brain anatomy was obtained using the transvaginal approach, allowing the detection of a single ventricle and fused thalami. We conclude that transvaginal ultrasonography is not only important for the early prenatal diagnosis of central nervous system abnormalities but also for enhancing brain visualization when transabdominal examination of the fetal head is limited due to maternal and fetal factors.

Recovery and relapse in adolescents with bipolar affective illness: a five-year naturalistic, prospective follow-up

OBJECTIVE

This study was a 5-year naturalistic prospective follow-up of 54 consecutive admissions of adolescents to a university inpatient service with a diagnosis of bipolar I affective illness.

METHOD

Subjects received structured clinical evaluations every 6 months after entry to establish time to recovery and subsequent relapse. Regression models were used to identify predictors of differential course.

RESULTS

Rate of recovery varied by polarity of episode at time of entry, with quick recovery observed in subjects with pure mania or mixed states, and a protracted index episode in subjects with pure depression. Multiple relapses were most often seen in subjects with mixed or cycling episodes at intake.

CONCLUSIONS

Polarity of illness may have utility in identifying bipolar adolescents with a more recurrent illness. Comparison with adult data suggests that recurrence risks may vary as a function of age at onset or stage of the disease process.

Cloning and characterization of the Bacillus subtilis birA gene encoding a repressor of the biotin operon

The Bacillus subtilis birA gene, which regulates biotin biosynthesis, has been cloned and characterized. The birA gene maps at 202 degrees on the B. subtilis chromosome and encodes a 36,200-Da protein that is 27% identical to Escherichia coli BirA protein. Three independent mutations in birA that lead to deregulation of biotin synthesis alter single amino acids in the amino-terminal end of the protein. The amino-terminal region that is affected by these three birA mutations shows sequence similarity to the helix-turn-helix DNA binding motif previously identified in E. coli BirA protein. B. subtilis BirA protein also possesses biotin-protein ligase activity, as judged by its ability to complement a conditional lethal birA mutant of E. coli.

Postoperative analgesia with transdermal fentanyl following lower abdominal surgery

In a randomised, placebo-controlled, double-blind study involving 81 patients undergoing total abdominal hysterectomy, the postoperative analgesia provided by transdermal fentanyl given at 25, 50, or 75 micrograms.h-1 for 72 h was compared with a placebo group. The efficacy of the Transdermal Therapeutic System was related to the rate of fentanyl delivery, higher rates being associated with significantly lower visual analogue pain scores (24, 20, 17 and 13, for placebo, 25, 50 and 75 micrograms.h-1 respectively) and reduced patient controlled analgesia morphine requirements (44, 38, 33 and 31 mg respectively). Patients' overall sedation scores were not increased by transdermal fentanyl, but respiratory rates decreased with higher transdermal fentanyl dosage.

True knot of the umbilical cord: a difficult prenatal ultrasonographic diagnosis

We examined retrospectively the use of ultrasonography in 18 cases in which a true knot of the umbilical cord was found at delivery. All women had a normal second-trimester scan in which no cord abnormality was detected. Thirteen (72%) also had third-trimester color Doppler ultrasonography, at which time the cord anomaly was again missed. In one of these cases the diagnosis could have been made with color flow imaging, but the abnormal pattern was mistaken instead for multiple loops of cord. On the other hand, the diagnosis of true knot was considered prenatally in two cases, but not confirmed at delivery, when only a prominent false knot was found in one and a normal cord in the other. We conclude that true knots of the umbilical cord do not have a characteristic appearance in utero and therefore are easily missed at routine prenatal ultrasonography.

Third-trimester hyperechogenic bowel in Down syndrome

The association between second-trimester hyperechogenic bowel and Down syndrome has been well established in the literature. In this report we present a case of Down syndrome in which this finding was only detected during the third-trimester scan, after normal bowel echogenicity was documented in the second trimester. This report suggests that hyperechogenic bowel could be a late manifestation of Down syndrome.

Filtration of fentanyl is not the cause of the elevation of arterial blood pressure associated with post-bypass ultrafiltration in children

Modified ultrafiltration after cardiopulmonary bypass in children has been shown to be associated with an increase in arterial blood pressure. As part of a series of studies to investigate the possible causes of this blood pressure elevation, the hypothesis that if filtration was removing a significant amount of fentanyl, then the increase in blood pressure might be due to pain was proposed. Ten children, aged between 0.5 and 9.3 years (median 3.8 years), weighing 5.9 to 25.5 kg (median 15.7 kg), underwent corrective cardiac surgery (incorporating modified ultrafiltration). A standard anesthetic protocol was followed, with up to 78 micrograms/kg of fentanyl given prebypass for analgesia. After completion of cardiopulmonary bypass, modified ultrafiltration was commenced at 100 mL/min until a hematocrit of 35% was reached. Samples were taken of arterial blood (prefiltration, 3, 10, and 20 minutes postfiltration), the venous reservoir blood (prefiltration) and the filtrate (5 and 10 minutes into filtration). Hemodynamic data were recorded both prefiltration and postfiltration. The hemodynamic data showed the expected rise in both systemic arterial pressure and cardiac index after ultrafiltration. The plasma fentanyl concentrations did not significantly change after ultrafiltration: 1.59 to 12.39 ng/mL (median 6.27 ng/mL) prefiltration and 2.05 to 15.59 ng/mL (6.29 ng/mL) at 3 minutes, 2.22 to 12.64 ng/mL (6.87 ng/mL) at 10 minutes, and 1.83 to 11.52 ng/mL (5.85 ng/mL) at 20 minutes postfiltration.(ABSTRACT TRUNCATED AT 250 WORDS)

Discordant iliac and femoral artery flow velocity waveforms in fetuses with single umbilical artery

OBJECTIVE

The aim of this study was to investigate pelvic and femoral arterial flow velocity waveforms in fetuses with a single umbilical artery.

STUDY DESIGN

Seven fetuses with single umbilical artery and no other ultrasonographically detected anomalies were studied with color Doppler ultrasonography at a median gestational age of 24 weeks (range 18 to 34 weeks). Flow velocity waveforms from the relevant vessels were obtained as follows: (1) umbilical artery from a free loop of cord, (2) common iliac artery from both sides just below the aortic bifurcation, (3) internal iliac artery and intraabdominal portion of the umbilical artery from the vessel visualized alongside the fetal bladder, and (4) femoral artery on both sides from the upper third of the fetal thigh. The pulsatility index was measured, and comparisons were made with the paired t test. A p value < 0.05 was considered significant.

RESULTS

The pulsatility index in the umbilical artery was normal in all cases. There were highly significant differences between the common iliac arteries in each side (difference in pulsatility index 2.7, 95% confidence interval 2.0 to 3.5, p < 0.001). Significant differences between both femoral arteries were also noted (difference in pulsatility index 1.0, 95% confidence interval 0.3 to 1.7, p < 0.001). In both vessels the pulsatility index was always higher in the side that did not participate in the placental circuit.

CONCLUSION

This study demonstrates that fetuses with single umbilical artery have asymmetric arterial blood flow patterns in the pelvic and lower extremities.

Human maternal uniparental disomy for chromosome 16 and fetal development

Two severely growth-retarded fetuses found to have maternal uniparental disomy (UPD) for chromosome 16 and trisomy 16 placental mosaicism both had an unfavourable outcome. Antenatally, the first case was complicated by an unexplained raised maternal serum alpha-fetoprotein concentration, preterm premature rupture of the membranes, and growth retardation detectable at 21 weeks' gestation, whilst the other had an unexplained raised maternal serum human chorionic gonadotrophin level, a two-vessel cord on ultrasound, and cessation of growth at 25 weeks. At post-mortem, both babies had an imperforate anus. Fetal maternal UPD may explain the poor outcome that occurs in some cases of confined placental mosaicism for chromosome 16 and is also associated with specific fetal abnormalities.

Fetal hyperechogenic bowel following intra-amniotic bleeding

OBJECTIVE

To test the hypothesis that increased echogenicity of the fetal bowel at second-trimester scans results from intra-amniotic bleeding.

METHODS

We studied 726 patients undergoing second-trimester amniocentesis for advanced maternal age. Three groups were identified according to the color of the amniotic fluid (AF) obtained: clear fluid, blood-stained fluid, and dark brown fluid. Two to 4 weeks after the amniocentesis, all patients had a targeted ultrasound examination for the detection of fetal structural anomalies and markers of chromosomal abnormalities, which included a survey of the fetal bowel. The incidence of hyperechogenic bowel in each group was compared by Fisher exact test. P < .05 was considered significant.

RESULTS

In 694 cases, the AF was clear (95%), in 20 blood-stained (3%), and in 12 dark brown (2%). Hyperechogenic bowel was detected in 14 fetuses with clear fluid (2%), in two with blood-stained fluid (10%), and in three with dark brown fluid (25%). Fetuses with proven intra-amniotic bleeding (ie, dark brown or blood-stained AF at amniocentesis) had a significantly higher incidence of hyperechogenic bowel compared to those with clear AF (five of 32 [15.6%] and 14 of 694 [2.0%], respectively; P < .001, 95% confidence interval for the difference in proportions 6.3-17.6%).

CONCLUSIONS

Our study demonstrates that intra-amniotic bleeding is associated with an increased incidence of fetal hyperechogenic bowel at second-trimester ultrasound scans. This sonographic phenomenon may be due to the presence of blood in the fetal bowel caused by fetal swallowing of bloody AF.

Long-term prognosis of transient lone bilateral blindness in adolescents and young adults

We describe a group of 14 patients aged 8-38 years at presentation who had one or more sudden transient attacks of bilateral blindness. Eight patients described bilateral blindness as their only symptom whereas six others experienced some mild associated symptoms. Visual loss always developed within seconds and attacks were often precipitated by exercise, stress, or postural change. Of 13 patients available for review, none suffered a major vascular event during a mean follow up of 10 years. When adolescents and young adults present with transient bilateral blindness, investigations are unlikely to reveal a cause and the long-term prognosis appears benign.

The value of color Doppler ultrasound in the prenatal diagnosis of hypoplastic umbilical artery

The prenatal diagnosis of hypoplastic umbilical artery has recently been reported, based on the visualization of discordant size between both umbilical arteries in association with discordant umbilical artery flow velocity waveforms. In this report we present two cases of hypoplastic umbilical artery and describe the use of color flow imaging and Doppler ultrasound in the prenatal evaluation of this condition. The principal advantages of these techniques include the confirmation of blood flow within the hypoplastic artery, thus ruling out the possibility of an atrophic non-functional artery, and the demonstration of size discrepancy at the level of the intra-abdominal portion of the umbilical arteries, validating the intra-amniotic cord findings. Color Doppler ultrasound is an important tool for diagnosing and evaluating vascular anomalies affecting the umbilical cord.

Doppler ultrasound screening as part of routine antenatal scanning: prediction of pre-eclampsia and intrauterine growth retardation

OBJECTIVE

To assess the value of incorporating continuous wave Doppler ultrasound of the uterine arteries into the routine scan as a screening test in an unselected population.

DESIGN

A cross sectional study by multiple operators using continuous wave Doppler ultrasound to obtain flow velocity waveforms (FVW) from both uterine arteries of all women attending for routine anomaly scan at 18 to 22 weeks over a period of 12 months. An abnormal FVW in either uterine artery was used to predict intrauterine death, antepartum haemorrhage and three different degrees of severity of pre-eclampsia and growth retardation, singly and in combination.

SETTING

King's College Hospital, London.

SUBJECTS

Two thousand, four hundred and thirty women attending for routine anomaly ultrasound scan.

RESULTS

A total of 2430 women were scanned with a 90% follow up rate. The results demonstrate higher sensitivities than previous studies, but with a high proportion of false positive tests. By including an early diastolic notch in the definition of an abnormal FVW the prediction of pre-eclampsia is markedly improved; the relative risk to a woman with an abnormal waveform of developing moderate or severe pre-eclampsia is increased 24-fold. Although the positive predictive value for babies less than the 5th centile for gestation is only 15%, those at risk of neonatal complications may be identified.

CONCLUSION

This simple test can be performed at a routine visit and a group of women can be identified for further assessment and possible therapeutic intervention.