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Biomedical subjects

N M Fisk

Publications and source records attributed to N M Fisk.

At least 145 records · Page 8Linked to original sources
PubMed1995

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.

Adult↗
PubMed1995

Prenatal diagnosis of cerebral arteriovenous malformation using color Doppler ultrasonography: case report and review of the literature.

Aneurysms of the vein of Galen are rare, representing less than 1% of all intracranial arteriovenous malformations. In the fetus, however, almost all cerebral arterial malformations involve the vein of Galen, usually presenting in the neonatal period with severe cardiac failure leading to neonatal death. In this report we present a case of arteriovenous malformation involving the vein of Galen detected prenatally at 35 weeks with the use of color Doppler ultrasonography. The literature is reviewed in an attempt to delineate the role of prenatal ultrasonography in the diagnosis and its impact on perinatal outcome.

Adult↗
PubMed1995

Uptake of meta-analytical overviews of effective care in English obstetric units.

OBJECTIVE: To establish the current availability of meta-analytical overviews of effective care in perinatal medicine, in the form of Effective Care in Pregnancy and Childbirth and the Oxford Database of Perinatal Trials, in English obstetric units and to find out how obstetricians without either one keep up to date. DESIGN: Standardised telephone questionnaire. SUBJECTS: The consultant obstetrician deemed to be the Royal College of Obstetricians and Gynaecologists' administrative contact in each of the 24 teaching hospitals, and in 74 of 173 (43%) district general hospitals in England. MAIN OUTCOME MEASURES: Knowledge and use of Effective Care and the Oxford Database in the obstetric unit. RESULTS: Thirty-seven percent of units did not have access to either Effective Care or the Oxford Database, with significant differences between district general hospitals and teaching hospitals in lack of availability (33/74 (45%) versus 3/24 (12%) respectively, P = 0.02). Effective Care was available in 51% of district general hospitals and 79% of teaching hospitals, compared with the availability of the Oxford Database which was only available in 16% and 62%, respectively. Reasons given for not obtaining either included non-awareness, expense, and perceived lack of need. The consultants with neither Effective Care nor the Oxford Database claimed to keep up to date by various methods, usually as information from colleagues. CONCLUSIONS: These results reflect both inefficient dissemination of medical knowledge in obstetrics and the reluctance of obstetricians to consider adapting their practice as a result of evidence from meta-analyses of randomised controlled trials. Although Effective Care is more widely available than the Oxford Database, its datedness renders it inferior to the database as a means of facilitating effective care in obstetrics.

Clinical Competence↗
PubMed1995

Fetal telemedicine: interactive transfer of realtime ultrasound and video via ISDN for remote consultation.

Current referral practice for ultrasonically detected fetal abnormalities contributes to parental anxiety, inconvenience to patients, diagnostic inaccuracy, and general service inefficiency. To determine whether telemedicine would reduce these disadvantages, we established a 30-channel ISDN link between a district general hospital on an island and a subspecialty referral centre approximately 120 km away on mainland Britain. Live ultrasound images of the fetus were transmitted in realtime from a commercial scanner in the hospital using a total data transfer rate of 2 Mbit/s. After decompression at the receiving end, there was almost no perceptible loss of picture quality or frame rate. This report describes the technical aspects of the link and our preliminary experience with it. In the first two months of its operation, the link worked well and the consultants who used it found themselves confidently making diagnoses and carrying out counselling over it. If confirmed, the success of this technology has implications for future referral practice in fetal medicine.

Artifacts↗
PubMed1994

Fetal plasma cortisol and beta-endorphin response to intrauterine needling.

The purpose of this study was to investigate whether the fetus mounts a hormonal stress response to a potentially painful procedure, intrauterine needling. Cortisol and beta-endorphin concentrations in fetal plasma obtained during uncomplicated fetal blood sampling or intrauterine transfusions by needling the fetal intra-abdominal portion of the umbilical vein (intrahepatic vein) were compared to hormone concentrations in fetal plasma obtained by the conventional technique of needling the placental cord insertion, which is not innervated. Cortisol and beta-endorphin concentrations did not increase within 10 minutes of fetal abdominal needling (n = 15). However, more prolonged needling during transfusion at the intrahepatic vein was associated with an increase in fetal plasma cortisol (median increase 48 nmol/L; 95% Cl, 23-86) and beta-endorphin (207 pg/mL; 113-307) concentrations compared to transfusion at the placental cord insertion (p < 0.005 for both hormones). The magnitude of rise in hormone increased linearly with the duration of needling (cortisol, r = 0.80; beta-endorphin, r = 0.88, p < 0.05 for both). These data suggest that the fetus mounts a hormonal stress response to invasive procedures. They raise the possibility that the human fetus feels pain in utero, and may benefit from anaesthesia or analgesia for invasive procedures.

Analgesia↗
PubMed1994

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.

Journal Article↗
PubMed1994

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.

Blood Flow Velocity↗
PubMed1994

The influence of operator transducer pressure on ultrasonographic measurements of amniotic fluid volume.

OBJECTIVE: Our purpose was to study the effect of operator transducer pressure on amniotic fluid index and single deepest pool measurements and their intraobserver and interobserver variability. STUDY DESIGN: Forty subjects in the third trimester with intact membranes were studied by two observers at three predetermined operator pressures. Pressure was measured by interfacing a flexible water-filled reservoir connected to a manometer between the maternal abdomen and the ultrasonography transducer. The amniotic fluid index and single deepest pool were measured on screen by another operator, and data were analyzed by calculating components of variance. RESULTS: Compared with medium pressure, low pressure resulted in a 13% increase in amniotic fluid index (p < 0.001), and high pressure resulted in a 21% fall in amniotic fluid index (p < 0.001). The single deepest pool was less sensitive to pressure, with a 11% increase at low pressure (p < 0.001) and a 16% fall at high pressure (p < 0.001). Intraobserver error was 17% for amniotic fluid index and 18% for single deepest pool when operator pressure was controlled at medium pressure; this increased to 28% and 24%, respectively, when pressure was not controlled (p < 0.01). Interobserver error was consistently very low. CONCLUSION: Both techniques are highly sensitive to the pressure applied to the maternal abdomen during scanning. The reproducibility of amniotic fluid index and single deepest pool is comparable. The use of the same observer for serial measurements of amniotic fluid index would appear to be less important than careful attention to transducer pressure.

Amniotic Fluid↗
PubMed1994

Erythropoietic suppression in fetal anemia because of Kell alloimmunization.

OBJECTIVE: Our purpose was to test the hypothesis that maternal anti-Kell alloimmunization produces fetal anemia by erythroid suppression. STUDY DESIGN: Erythropoiesis in 11 anemic fetuses from maternal anti-Kell alloimmunization was compared with that in 11 fetuses where the mother was alloimmunized to RhD; each was matched for hematocrit, gestational age, hydrops, and perinatal outcome. Comparisons of the difference were performed by either paired t or Wilcoxon tests. RESULTS: The anti-Kell group had reduced reticulocytosis (p = 0.007) and erythroblastosis (p = 0.045) and lower amniotic fluid bilirubin concentrations (p = 0.02) in comparison with the anti-D group. No correlation was found between hematocrit and reticulocytosis in the anti-Kell group, whereas the anti-D group had a significant linear relationship (r = 0.63, p < 0.05), indicating a progressive reticulocytosis in response to the degree of anemia. CONCLUSION: These findings suggest that erythroid suppression, rather than hemolysis, is the predominant mechanism in producing fetal anemia related to maternal Kell alloimmunization. Fetal blood sampling is the investigation of choice in the evaluation of anemia related to maternal Kell alloimmunization, because reduced hemolysis means amniotic fluid bilirubin concentrations correlate poorly with anemia.

Erythroblastosis, Fetal↗
PubMed1994

Clinical utility of fetal RhD typing in alloimmunized pregnancies by means of polymerase chain reaction on amniocytes or chorionic villi.

OBJECTIVE: Our purpose was to describe the clinical utility of a deoxyribonucleic acid amplification method for determining fetal RhD status in alloimmunized pregnancies STUDY DESIGN: Six RhD-negative women with alloimmunized pregnancies and heterozygous partners underwent amniocentesis (n = 5) or chorionic villus sampling (n = 1). Fetal RhD type was determined by polymerase chain reaction and results disclosed to the attending physicians. RESULTS: Knowledge of the fetal RhD status avoided further invasive procedures in two pregnancies and facilitated the timing or performance of intrauterine transfusions in the remainder. CONCLUSIONS: In alloimmunized pregnancies the ability to RhD-type the fetus in amniotic fluid avoids the risks of fetomaternal hemorrhage and increased sensitization associated with fetal blood sampling or chorionic biopsy. This allows more rational pregnancy management, avoiding invasive procedures in the presence of an RhD-negative fetus, or planning therapeutic interventions or offering termination of pregnancy in the presence of an RhD-positive fetus.

Amniotic Fluid↗
PubMed1994

Direct volume measurement at midtrimester amnioinfusion in relation to ultrasonographic indexes of amniotic fluid volume.

OBJECTIVE: Our purpose was to investigate the relationship between amniotic fluid volume and semiquantitative ultrasonographic assessment of amniotic fluid in the midtrimester. STUDY DESIGN: Sixteen pregnancies between 16 and 28 weeks with minimal amniotic fluid (severe oligohydramnios or anhydramnios) and intact membranes were studied at the time of clinically indicated amnioinfusion. The amniotic fluid index and deepest pool measurement were determined before and immediately after the procedure. Correlations were sought by means of standard regression techniques with amniotic fluid volume (i.e., volume infused) on the basis of the assumption that amniotic fluid volume before amnioinfusion was effectively nil. RESULTS: There was a significant linear relationship between amniotic fluid index and volume infused (y = 7.336 + 0.015x; R2 = 0.30, p < 0.05). However, no correlation with the deepest pool measurement technique was found (R2 = 0.11, p > 0.05). CONCLUSION: Amniotic fluid index is preferable to deepest pool measurement in assessing amniotic fluid volume in the second trimester of pregnancy. The low variance (30%) suggests that better predictors of amniotic fluid volume are still required.

Amniotic Fluid↗
PubMed1994

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.

Amniocentesis↗