Search PubMed⌕ Search

Biomedical subjects

D S Richards

Publications and source records attributed to D S Richards.

At least 37 records · Page 2Linked to original sources
PubMed1995

Prenatal diagnosis of fetal disseminated intravascular coagulation associated with umbilical cord arteriovenous malformation.

BACKGROUND: Congenital disseminated intravascular coagulation (DIC) has been reported in a variety of clinical settings, but to our knowledge, it has never been documented before birth. We describe prenatal identification of an umbilical cord vascular tumor and echogenic foci in the fetal liver leading to the diagnosis of fetal DIC by funipuncture. CASE: A large vascular tumor of the umbilical cord was identified using prenatal sonography. At 31 weeks' gestation, echogenic areas, which were thought to represent infarcts or thrombi, were seen in the liver. When funipuncture revealed florid fetal DIC, delivery was accomplished by cesarean to prevent intracranial bleeding. Pathologic examination of the umbilical cord tumor showed it to be a large arteriovenous malformation. CONCLUSION: Arteriovenous malformations may cause fetal coagulopathy. This case illustrates that funipuncture may be used to diagnose this condition and that timely cesarean delivery may contribute to a favorable outcome.

Adult↗
PubMed1995

Maternal and umbilical serum concentrations of granulocyte colony-stimulating factor and its messenger RNA during clinical chorioamnionitis.

OBJECTIVE: To determine whether women with chorioamnionitis developed elevated serum granulocyte colony-stimulating factor (G-CSF) concentrations and, if so, whether the G-CSF crossed to the fetus. METHODS: We quantified G-CSF before, during, and after delivery and in the cord blood of 12 women with clinical chorioamnionitis and 12 matched controls. We also measured G-CSF messenger RNA (mRNA) transcripts in mononuclear cells isolated from maternal and cord blood at delivery. RESULTS: At study entry, G-CSF concentrations were much higher in women with chorioamnionitis (1397 +/- 950 pg/mL, mean +/- standard error of mean) than in controls (17 +/- 5 pg/mL, P < .05). At delivery, concentrations had increased in both groups (2752 +/- 1100 pg/mL in the chorioamnionitis group, 165 +/- 61 pg/mL in controls; P < .05). After delivery, G-CSF concentrations had diminished to 839 +/- 594 pg/mL in women with chorioamnionitis and to 83 +/- 16 pg/mL in controls (P < .05). Concentrations in the cord blood were 2729 +/- 974 pg/mL for the chorioamnionitis group and 51 +/- 17 pg/mL for controls (P < .05). Granulocyte colony-stimulating factor mRNA transcripts were more abundant in women with chorioamnionitis than in controls but were scarce in all matched cord blood samples tested. CONCLUSION: Serum G-CSF concentrations were elevated during clinical chorioamnionitis, and similar levels were found in maternal and cord serum. Because G-CSF mRNA levels were very low in cord mononuclear cells, the G-CSF in cord serum might be maternal in origin.

Adult↗
PubMed1994

Sonographic visualization of the fetal upper airway.

Laryngeal obstruction is a life-threatening condition which can sometimes be diagnosed by prenatal ultrasound examination. Dilatation of the fetal trachea is an important finding in these cases. Sonographic studies to evaluate the fetal upper airway were performed in 120 consecutive patients. The diameters of the trachea and pharynx were measured and our ability to visualize the trachea and the larynx was evaluated. The diameter of the trachea increased from a mean of 2.4 mm at 18 weeks to 4.6 mm at 38 weeks. The mean diameter of the pharynx increased from 4.4 mm at 18 weeks to 8.8 mm at 38 weeks. The fetal larynx was adequately visualized in 67%) of the cases, while the entire trachea was seen in 47% of the cases. Our success in visualizing the larynx and trachea was best between 20 and 30 weeks' gestation. This study shows that it is possible to obtain excellent views of the fetal airway in a high percentage of cases and reports the range of normal values for tracheal diameter. Early visualization of a diluted trachea may allow better management of a fetus with laryngeal obstruction.

Journal Article↗
PubMed1994

Modification of an intrauterine shunt catheter to reduce the incidence of spontaneous displacement.

OBJECTIVE: To determine which of four types of catheters would be the least likely to become displaced spontaneously when employed as a fetoamniotic shunt, by testing the force required to remove the catheters from a lamb's bladder. METHODS: The catheter designs tested were unfeathered straight, unfeathered pig-tailed, superficially feathered, and deeply feathered. The catheters were placed percutaneously into the urinary bladders of recently euthanized newborn lambs. The force required to withdraw the catheters was determined, employing nine measurements for each catheter design. RESULTS: The mean force required to remove the straight catheter was 12 g (95% confidence interval [CI] 2-21 g), the pig-tailed catheter 22 g (95% CI 13-32 g), and the superficially feathered catheter 149 g (95% CI 139-160 g). Extracting the deeply feathered catheter consistently required a force greater than 300 g, which was the upper limit of detection for our instruments. CONCLUSION: Feathering the catheter increases the force required to extract it from a fetal viscus. We believe that use of feathered catheters will significantly reduce the incidence of unwanted spontaneous displacement.

Amnion↗
PubMed1994

Effect of altitude on the amniotic fluid index.

The effect of altitude on amniotic fluid volume has not been studied previously. We sought to determine whether there is such an effect by measuring the amniotic fluid index (AFI) in pregnant women at low and high altitudes. We compared populations of pregnant women at two institutions, one located at low elevation (100 ft) and the other at relatively high altitude (6,000 ft). Uncomplicated singleton pregnancies between 20 and 42 weeks' gestation with adequate dating criteria were studied. Patients were excluded if any condition known to alter amniotic fluid volume was present. Data were stratified by gestational age at two-week intervals for analysis. The pregnant women at high altitude (n = 364) had a significantly increased (P < .001) AFI throughout gestation as compared to the low-altitude group (n = 514). The mean difference in the AFI between the two populations for the two-week intervals was 1.5 cm (95% confidence interval, 1.0-2.0). As compared to the low-altitude group, the high-altitude population had a greater proportion of women with polyhydramnios (5.8% versus 1.0%, P < .001) and fewer patients with oligohydramnios (2.5% versus 5.6%, P < .001) after categorization of AFI values utilizing previously established nomograms. This finding suggests that there is an association between high altitude and an increase in the AFI. The mechanism and clinical significance of this effect are unknown.

Altitude↗
PubMed1993

Antenatal sonographic findings associated with unilateral pulmonary agenesis.

BACKGROUND: Unilateral pulmonary agenesis is a rare anomaly that has a relatively frequent association with other congenital malformations. Prognosis depends in part upon associated anomalies and whether the right or left lung is involved. The prenatal sonographic findings of this defect share some similarities with those of other intrathoracic lesions or congenital diaphragmatic hernia. CASE: Our patient had a twin gestation complicated by early discordant growth and hydramnios. The smaller fetus had cardiac dextroposition, abnormally echogenic left lung tissue, and a flattened but clearly visible left hemidiaphragm. No abdominal viscera were seen in the thoracic cavity. Postnatally, this infant was found to have agenesis of the right lung, a tracheoesophageal fistula, and pyloric stenosis. CONCLUSION: The diagnosis of unilateral pulmonary agenesis should be considered in a fetus with the sonographic findings of a shift of the mediastinal structures, echogenic lungs, and an intact diaphragm.

Abnormalities, Multiple↗
PubMed1992

The perinatal management of severe laryngeal stenosis.

BACKGROUND: Conditions that completely occlude the fetal larynx are rare. We describe the perinatal course of an infant with severe congenital subglottic stenosis, for whom the prenatal recognition of airway occlusion led to enhanced neonatal management. CASE: Serial ultrasound examinations from 23-37 weeks' gestation led to the diagnosis of upper airway obstruction in the fetus of a 29-year-old woman. Significant findings included fetal ascites, echogenic enlarged lungs, and a dilated fluid-filled trachea. The infant was delivered in a level III hospital with a neonatologist and anesthesiologist in attendance. The cord was not clamped until a tracheostomy was secured. CONCLUSION: Upper-airway obstruction can be diagnosed prenatally by the presence of secondary manifestations. Infant survival may depend on foreknowledge of the pathology and prompt, directed efforts at bypassing the airway obstruction.

Adult↗
PubMed1992

Sound levels in the human uterus.

OBJECTIVE: We sought to determine the degree to which noises and voices are attenuated or enhanced as they pass into the uterus. METHODS: In eight parturients, a hydrophone in the uterus was used to measure sound pressure levels for externally generated one-third-octave band noises, male and female voices, and the subject's voice. RESULTS: Low-frequency sounds (0.125 kHz) generated outside the mother were enhanced by an average of 3.7 dB. There was a gradual increase in attenuation for increasing frequencies, with a maximum attenuation of 10.0 dB at 4.0 kHz. Sound attenuation was slightly less if the insonation was from in front of the woman rather than behind. Intrauterine sound levels of the mother's voice were enhanced by an average of 5.2 dB, whereas external male and female voices were attenuated by 2.1 and 3.2 dB, respectively. The effect of frequency on attenuation, the differences between front and back insonation, and the differences between speakers in attenuation were all statistically significant. CONCLUSIONS: The intrauterine environment is rich with externally generated sounds. This may imply fetal risk from maternal noise exposure and may aid in understanding fetal imprinting from prenatal exposure to voices.

Acoustics↗
PubMed1991

Effects of vibration frequency and tissue thickness on intrauterine sound levels in sheep.

Pure-tone sinusoidal mechanical vibratory stimuli ranging in frequency from 4 to 4000 Hz were applied to the ventral abdominal wall of pregnant ewes, and intrauterine sound pressure levels were recorded with a hydrophone 5, 10, 15, and 20 cm from the surface. There were significant decreases in sound pressure levels with increasing frequencies (p less than 0.0001) and increasing depth (p = 0.01). There was no significant interaction between these two variables. An electronic artificial larynx was also activated on the abdominal wall, resulting in quite high sound pressure levels (mean, 119 dB) measured 5 cm from the surface, with a significant decrease in sound pressure levels as the thickness of the intervening maternal tissues increased (p = 0.005). These results suggest that the frequency of vibratory stimulus used and the thickness of the maternal abdominal wall could influence fetal response to the vibroacoustic stimulation test by affecting intrauterine sound pressure levels.

Acoustic Stimulation↗
PubMed1991

A platform for biological sequence comparison on parallel computers.

We have written two programs for searching biological sequence databases that run on Intel hypercube computers. PSCANLIB compares a single sequence against a sequence library, and PCOMPLIB compares all the entries in one sequence library against a second library. The programs provide a general framework for similarity searching; they include functions for reading in query sequences, search parameters and library entries, and reporting the results of a search. We have isolated the code for the specific function that calculates the similarity score between the query and library sequence; alternative searching algorithms can be implemented by editing two files. We have implemented the rapid FASTA sequence comparison algorithm and the more rigorous Smith-Waterman algorithm within this framework. The PSCANLIB program on a 16 node iPSC/2 80386-based hypercube can compare a 229 amino acid protein sequence with a 3.4 million residue sequence library in approximately 16 s with the FASTA algorithm. Using the Smith-Waterman algorithm, the same search takes 35 min. The PCOMPLIB program can compare a 0.8 million amino acid protein sequence library with itself in 5.3 min with FASTA on a third-generation 32 node Intel iPSC/860 hypercube.

Algorithms↗