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Biomedical subjects

K Nicolaides

Publications and source records attributed to K Nicolaides.

At least 55 records · Page 3Linked to original sources
PubMed1995

Fetal venous, intracardiac, and arterial blood flow measurements in intrauterine growth retardation: relationship with fetal blood gases.

OBJECTIVE: Our purpose was to investigate arterial, venous, and intracardiac blood flow in growth-retarded fetuses and to relate the Doppler results to blood gases in umbilical venous blood obtained by cordocentesis. STUDY DESIGN: A cross-sectional, pulsed-wave color Doppler ultrasonographic study of 23 severely growth-retarded fetuses undergoing cordocentesis and measurement of blood gases was performed. Blood velocity waveforms were recorded from the descending thoracic aorta, middle cerebral artery, inferior vena cava, ductus venosus, and atrioventricular valves. RESULTS: The Doppler studies demonstrated evidence of redistribution in the arterial system with increased impedance to flow in the aorta and decreased impedance in the cerebral circulation. The velocity of flow in the venous system and across the atrioventricular valves was decreased, whereas pulsatility of waveforms in the inferior vena cava and ductus venosus was increased. The mean umbilical venous blood PO2 and pH were decreased, and there were significant associations between blood gases and Doppler parameters in the thoracic aorta, middle cerebral artery, and ductus venosus. CONCLUSION: In severe intrauterine growth retardation the degree of fetal acidemia can be estimated from Doppler measurements of pulsatility in both the arterial system and the ductus venosus.

Aorta, Thoracic↗
PubMed1995

Fetal venous, arterial, and intracardiac blood flows in red blood cell isoimmunization.

OBJECTIVE: To investigate the effect of anemia on fetal venous, arterial, and intracardiac blood flows. METHODS: Color flow Doppler was used to record flow-velocity waveforms from the atrioventricular valves, ductus venosus, right hepatic vein, inferior vena cava, middle cerebral artery, and descending thoracic aorta from 38 cases of red blood cell isoimmunized pregnancies. Immediately after the Doppler studies, funipuncture was performed and the fetal hemoglobin concentration was measured. RESULTS: Blood flow velocities in the thoracic aorta, middle cerebral artery, and the ductus venosus were increased compared to reference ranges established previously; however, a significant association with the degree of anemia was found only for the velocity in the thoracic aorta. Pulsatility indices in arteries and veins and the ratio of early to late atrioventricular inflow velocities were not significantly different from normal. CONCLUSIONS: Fetal anemia is associated with a hyperdynamic circulation in both arterial and venous vessels. Even in severe anemia, there is no evidence of congestive heart failure. Venous and intracardiac Doppler studies do not provide a clinically useful contribution in the management of red blood cell isoimmunization.

Anemia↗
PubMed1995

Doppler studies of the fetal circulation in twin-twin transfusion syndrome.

This cross-sectional study investigated the circulatory profile of the donor and recipient fetuses in 20 pregnancies with twin-twin transfusion syndrome presenting with acute polyhydramnios at 17-27 (mean, 22) weeks' gestation. Doppler investigations of the arterial vessels and ductus venosus, inferior vena cava, right hepatic vein, tricuspid and mitral ventricular inflow were performed in both fetuses. Mean values of most blood flow velocities on the venous side showed a significant decrease in both groups of fetuses, and a significant increase in mean values for indices describing waveform pulsatility was found in all three venous vessels in the group of recipients, whereas in the donor group this was only the case in the ductus venosus. Mean values of atrioventricular flow velocities showed a significant decrease in the donor group. The most significant findings on the arterial side were an increased mean umbilical artery pulsatility index and a decreased mean value for aortic blood flow velocity in both groups of fetuses. Five recipients and four donors had absence or reversal of blood flow during atrial contraction in the ductus venosus. All these fetuses showed pulsations in the umbilical vein. Tricuspid regurgitation was present in eight recipients. Absence or reversal of end-diastolic velocities in the umbilical artery was found in four donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1995

Morphometric analysis of the great vessels in early fetal life.

Pathological examination of the heart and great vessels was performed in 61 specimens obtained after surgical termination of pregnancy for psychosocial indications at 9-18 weeks of gestation. The aorta and pulmonary trunk were identified and external diameters were measured at the level of, and distal to the aortic valve and pulmonary valve, the level of the aortic isthmus and thoracic aorta, and the proximal and distal ductus arteriosus. All eight vessel diameters increased linearly with gestational age and the ratio of the diameter of the aortic isthmus to that of the aortic valve or the distal ductus arteriosus also increased with gestation. Early pregnancy is characterized by rapid growth of the fetal head and this may well be the consequence of a preferential distribution of left ventricular output in favour of the head due to relative narrowing of the aortic isthmus at this gestation.

Adult↗
PubMed1995

Increased nuchal translucency in trisomy 21 fetuses: relationship to narrowing of the aortic isthmus.

Pathological examination of the great vessels was performed in 34 trisomy 21 fetuses after surgical termination of pregnancy at 11-16 weeks of gestation. In each case, the external diameters of eight segments of the great vessels were measured. The aortic valve and the ascending aorta were wider than in normal fetuses, whilst the aortic isthmus was narrower. The degree of narrowing of the isthmus was significantly greater in fetuses with high nuchal translucency thickness and it is possible that there is a causal association between the two.

Aorta↗
PubMed1994

Reference ranges for fetal venous and atrioventricular blood flow parameters.

This cross-sectional study establishes reference ranges with gestation for Doppler parameters of fetal venous and atrioventricular blood flow. Color flow Doppler was used to examine 143 normal singleton pregnancies at 20-40 weeks' gestation. Flow velocity waveforms were recorded from the ductus venosus, right hepatic vein and inferior vena cava. The waveforms are triphasic, reflecting ventricular systole, early diastole and atrial contraction. Peak velocities for these parameters were measured with pulsed Doppler and a new index, the peak velocity index for veins (PVIV), was calculated. Similarly, time-averaged maximum velocities for the whole cardiac cycle were measured and the pulsatility index for veins (PIV) was calculated. Flow velocity waveforms were also recorded at the level of the atrioventricular valves and the ratios of peak velocities at early diastolic filling (E) and atrial contraction (A) were calculated. Regression analysis was used to define the association of each measured and calculated Doppler parameter with gestational age. Blood flow velocities in the fetal veins and velocities and E/A ratios across the atrioventricular valves increased significantly with gestation, whereas PVIV and PIV decreased. Blood flow velocities were highest in the ductus venosus and lowest in the right hepatic vein, and PVIV and PIV were highest in the hepatic vein and lowest in the ductus venosus. In the ductus venosus, there was always forward flow throughout the heart cycle, whereas in the inferior vena cava and hepatic vein during atrial contraction, flow was away from or towards the heart or there was no flow. Pulsatility of flow velocity waveforms in the venous system is the consequence of changes in pressure difference between the venous system and the heart during the heart cycle. The finding that PVIV and PIV decrease with gestation is consistent with decreasing cardiac afterload and maturation of diastolic ventricular function.

Journal Article↗
PubMed1994

Comparison of chorionic villus sampling and amniocentesis for fetal karyotyping at 10-13 weeks' gestation.

We did a prospective study of women with singleton viable pregnancies at 10-13 weeks' gestation who requested first-trimester fetal karyotyping because of advanced maternal age, parental anxiety, or family history of chromosomal abnormality. Women were counselled as to the available options of non-invasive screening or invasive testing by mid-trimester amniocentesis, early amniocentesis (EA), or chorionic villus sampling (CVS), or randomisation to EA or CVS at 10-13 weeks. EA was done in 731 patients (493 by choice and 238 by randomisation) and CVS in 570 (320 by choice and 250 by randomisation). Both procedures were done by transabdominal ultrasound-guided insertion of a 20-gauge needle. The rate of successful sampling was the same for both procedures (97.5%). Spontaneous loss (intrauterine or neonatal death) was significantly higher after EA (total group mean = 5.3%, 95% CI 3.8-7.2; randomised subgroup mean = 5.9%, 3.3-9.7) than after CVS (total group: mean = 2.3%, 1.2-3.9; randomised subgroup: mean = 1.2%, 0.3-3.5). The gestation at delivery and birthweight of the infants after EA and CVS were similar. In the EA group the incidence of talipes equinovarus (1.63%), was higher than in the CVS group (0.56%), but this difference was not significant.

Adult↗
PubMed1994

Maternal contamination of amniotic fluid demonstrated by DNA analysis.

DNA from 16 sets of samples comprising DNA from uncultured amniotic fluid cells, cultured amniotic fluid cells, fetal tissue, and maternal blood was analysed by the polymerase chain reaction (PCR) with AC-repeat primers. The analysis was performed to investigate the presence of contaminating maternal cells in amniotic fluid which would affect the reliability of DNA studies for prenatal diagnosis. In three sets, maternal contamination of uncultured amniotic fluid cells was detected. In one of the three sets, maternal contamination was present in both uncultured and cultured amniotic fluid cells. The use of amniotic fluid cells as a source of DNA for prenatal diagnosis should be limited to cases where the purity of the DNA can be demonstrated prior to the diagnostic test being performed. This limitation in the use of amniotic fluid DNA also extends to other forms of diagnosis relying on the purity of amniotic fluid samples, particularly the new in situ hybridization methods currently being developed.

Amniotic Fluid↗
PubMed1994

Atrial natriuretic factor concentration in normal, growth-retarded, anemic, and hydropic fetuses.

OBJECTIVE: Our purpose was to establish a reference range with gestation for plasma concentrations of atrial natriuretic factor in fetal blood and to examine whether the concentration is altered in fetal anemia, acidemia, or hydrops. STUDY DESIGN: Atrial natriuretic factor was measured in umbilical venous blood taken by cordocentesis from pregnancies complicated by red blood cell isoimmunization (n = 17), intrauterine growth retardation (n = 12), and hydrops fetalis (n = 20) and from controls (n = 66). Additionally, maternal blood atrial natriuretic factor concentration was measured in 40 uncomplicated pregnancies. RESULTS: In the control group detectable levels were found from 16 weeks onward, and the fetal plasma atrial natriuretic factor concentration did not change with gestation. In anemic, acidemic, and hydropic fetuses the concentration was higher than in controls. CONCLUSION: Fetuses are capable of producing atrial natriuretic factor under physiologic conditions, and the concentration is increased appropriately in pathologic states.

Anemia↗
PubMed1994

Artery-to-artery anastomosis in monochorionic twins.

We describe Doppler signals in artery-to-artery anastomoses of two monochorionic twin pregnancies. Flow velocity waveforms demonstrated cyclic changes in systolic velocities with intermittent reversal of end-diastolic velocities. A computer model showed that this was the result of two opposing pulsatile blood flow waveforms with different velocities and frequencies.

Arterio-Arterial Fistula↗
PubMed1994

Permeation of human chorioamniotic membranes by Escherichia coli in vitro.

OBJECTIVE: Our goal was to study the permeation of Escherichia coli through human chorioamniotic membranes in vitro. STUDY DESIGN: Medium was placed in two compartments separated by chorioamniotic membranes obtained from six cesarean sections at term. The compartment faced by the chorion was inoculated with E. coli. Both compartments were sampled over 12 hours for observation of bacterial growth. Controls were performed without membranes. RESULTS: In the compartment that was inoculated, concentration of E. coli increased from 10(6) to 10(10) colony-forming units per milliliter. In the compartment faced by amnion, bacterial growth was observed after 6 hours and reached 10(3) colony-forming units per milliliter. Permeation of E. coli was confirmed histopathologically. The change of glucose and lactate was linear. In the controls the concentration of E. coli increased to 10(7) (p < 0.001). CONCLUSIONS: E. coli organisms permeate viable chorioamniotic membranes. The membranes constitute a weak barrier against ascending infection and do not inhibit bacterial growth.

Amnion↗
PubMed1994

The pathophysiology of the insulin-like growth factor axis in fetal growth failure: a basis for programming by undernutrition?

Recent evidence suggests that a number of adulthood conditions, including non-insulin dependent diabetes mellitus (NIDDM) and lipid and cardiovascular abnormalities are associated with intra-uterine growth retardation (IUGR). It is possible that this arises from programming of endocrine axes during development as a result of an adverse intra-uterine environment. Insulin-like growth factors (IGFs) are mitogenic polypeptides which stimulate cellular proliferation and differentiation and are important in human fetal development. The functions of IGFs are modulated by specific high affinity binding proteins (IGFBPs). IGFBP-1 is antagonistic to the insulin-like and growth promoting effects of IGF-I, and IGFBP-3 holds IGFs in the circulation by associating with IGFs and an acid labile subunit to form a ternary complex. Using specific radioimmunoassays and fetal serum obtained during diagnostic cordocentesis we have investigated the role of the IGF/IGFBP axis in human fetal development. In a study of 130 singleton pregnancies we have examined levels of immunoreactive IGFs and IGFBPs in normally grown fetuses (AGA), starved small fetuses affected by uteroplacental insufficiency (UPI), and non-starved small fetuses (SGA). IGF-I was significantly lower in the UPI group (n = 14, 7.8 +/- 0.6 micrograms l-1), than in either the SGA group (n = 22, 31.4 +/- 3.5 micrograms l-1, P = 0.0001) or the AGA group (n = 94, 36.3 +/- 1.9 micrograms l-1, P = 0.0001). IGFBP-3 showed similar changes (UPI: 682.6 +/- 50.0 micrograms l-1; SGA: 831.9 +/- 55.5 micrograms l-1; AGA: 847.7 +/- 19.8 micrograms l-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Carrier Proteins↗
PubMed1994

Antenatal management of fetomaternal alloimmune thrombocytopenia--report of 15 affected pregnancies.

The recognition that spontaneous intracranial haemorrhage (ICH) may occur in utero in fetomaternal alloimmune thrombocytopenia (FMAIT) led us to attempt to prevent this in 15 pregnancies of 11 women who had previously affected infants with FMAIT due to anti-HPA-1a. The antenatal management included fetal platelet transfusions and maternal steroids and/or high-dose intravenous immunoglobulin (IVIgG). In the first pregnancy, ICH occurred between 32 and 35 weeks' gestation before any treatment had been given, emphasizing the need for earlier intervention. Five of the 14 subsequent pregnancies in this study were considered to be severely affected (severe haemorrhagic complications in a previous infant and initial fetal platelet count < 20 x 10(9)/L in this study); four were managed successfully with weekly fetal platelet transfusions started between 18 and 29 weeks and continued until delivery at 33-35 weeks, and one severely affected case who was referred at 36 weeks was managed successfully with a single platelet transfusion prior to delivery. Five pregnancies were considered to be mildly affected (previous infants were unaffected by severe bleeding and initial fetal platelet count > 50 x 10(9)/L in this study). The platelet counts were maintained in one case with steroids and in three with IVIgG without the need for repeated platelet transfusions, but in the fifth the fetal platelet count fell despite steroids and IVIgG and serial platelet transfusions were required. Four pregnancies were unsuccessful; two pregnancies were terminated after severe ICH occurred at an early stage before fetal blood sampling had been carried out, one fetus died after the mother had a severe fall despite the successful initiation of fetal platelet transfusions and one died due to a cord haematoma which occurred at the time of the initial fetal blood sampling. The optimal management of FMAIT to reduce the risk of antenatal ICH remains uncertain. Steroids and IVIgG may be effective in some mildly affected cases but serial fetal platelet transfusions are the preferred therapy for those who are severely affected.

Antigens, Human Platelet↗
PubMed1994

Fetal therapy.

Twin to twin transfusion syndrome and twin reversed arterial perfusion sequence affect up to 15% of monozygotic twin pregnancies. They can lead to miscarriage or very premature delivery, and fetal death. Intrauterine treatment is leading to an increased rate of survival of at least one twin in affected pregnancies.

Amniocentesis↗
PubMed1994

The role of cordocentesis in the diagnosis of fetal well-being.

One of the most important parameters that any antenatal testing technique is measured against is the fetal acid-base balance. Cordocentesis is a relatively safe invasive method that can be used to evaluate the fetal acid-base status directly. The knowledge of these parameters is always invaluable under research conditions and, in select instances, can contribute significantly to clinical management.

Acid-Base Imbalance↗
PubMed1994

Umbilical artery steal syndrome and distal gangrene in a case of twin-twin transfusion syndrome.

BACKGROUND: Vascular accidents in the survivor from pregnancies with twin-twin transfusion syndrome have been attributed to the release of thromboplastin from the dead fetus. CASE: In a woman presenting at 22 weeks' gestation with acute polyhydramnios due to twin-twin transfusion syndrome, endoscopic laser coagulation of the communicating vessels was performed. At endoscopy, the toes of the left foot of the recipient fetus were noted to be gangrenous. This fetus had only a left umbilical artery, which was markedly dilated, and Doppler studies demonstrated impaired perfusion of the left leg. In four control fetuses with a single umbilical artery, Doppler studies demonstrated normal waveforms in both legs. CONCLUSION: In twin-twin transfusion syndrome, fetal peripheral gangrene may occur before the death of one twin. The ischemic necrosis of the toes probably resulted from the combined effect of polycythemia and umbilical artery steal syndrome. Interruption of twin-twin transfusion syndrome caused resolution of the polycythemia and prevented further damage by removing one of the components of the peripheral ischemia.

Adult↗