Brain perfusion monitoring with frequency-domain and continuous-wave near-infrared spectroscopy: a cross-correlation study in newborn piglets.

The newborn piglet brain model was used to correlate continuous-wave (CW) and frequency-domain (FD) near-infrared spectroscopy. Six ventilated and instrumented newborn piglets were subjected to a series of manipulations in blood oxygenation with the effects on brain perfusion known to be associated with brain hypoxia-ischaemia. An excellent agreement between the CW and FD was demonstrated. This agreement improved when the scattering properties (determined by the FD device) were employed to calculate the differential pathlength factor, an important step in CW data processing.

Role of frequency domain optical spectroscopy in the detection of neonatal brain hemorrhage--a newborn piglet study.

OBJECTIVE: Inability of continuous wave (CW) optical spectroscopy to measure changes in scattering, and the use of an arbitrary rather than an actual baseline, makes the CW method highly susceptible to errors that can lead to a false-positive or false-negative diagnosis. Our objective was to assess whether, and to what extent, the use of quantitative frequency domain spectroscopy would improve our ability to detect and monitor the development of brain hemorrhage. METHODS: A dual-channel frequency-domain tissue spectrometer (Model 96208, ISS, Inc., Champaign, IL) was used to monitor the development of experimental subcortical and periventricular-intraventricular hemorrhage (IVH) in 10 newborn piglets (blood injection model). The multidistance approach was employed to calculate the absorption and reduced scattering coefficients and hemoglobin changes from the ac, dc, and phase values acquired at four different source-detector distances and at 752 nm and 830 nm. RESULTS: There were significant absorption and scattering changes in the subcortical hematoma (n = 5) and the IVH groups (n = 5). The smallest detectable amount of blood in the brain was 0.04 ml. Changes associated with subcortical hematoma were several times higher than those associated with IVH, and correlated better with the estimated cross-sectional area of the hematoma than with the volume of the injected blood. As opposed to IVH, there was a significant absorption difference between the injured (subcortical hematoma) and normal side of the brain, probably because in case of IVH a significant volume of the injected blood had accumulated/spread beyond the reach of the probe. CONCLUSION: Clearly, frequency-domain spectroscopy cannot increase our ability to quantify the volume (size) or the oxygenation of the injected blood, especially in the case of IVH. However, the ability to quantify the baseline tissue absorption and scattering would significantly improve diagnostic performance, and may allow for early identification and treatment of neonatal brain hemorrhage.

Real-time optical imaging of experimental brain ischemia and hemorrhage in neonatal piglets.

Our objective was to study the development of experimental brain ischemia and hemorrhage by real-time optical imaging. Optical imaging is based on the ability of near infrared light to non-invasively penetrate through the intact scalp and skull and measure brain concentrations of oxy- and deoxyhemoglobin, dominant brain absorbers. Optical imaging was performed in 7 anesthetized, instrumented, and ventilated newborn piglets subjected to the injection of 0.3 cc of saline followed by 2 cc of blood into the left frontal subcortical brain region via a needle inserted through the skull with stereotactic guidance. The image-acquisition rate of 5.26 images per sec allowed for real-time imaging. The detection threshold of the imager at the estimated depth of 1-1.5 cm was approximately 70 microL for saline and approximately 40 microL for blood. The imager readily detected five subcortical hematomas and two large bilateral subarachnoid hemorrhages. The imager detected a global decrease in brain absorption associated with the volume-injection-related increase in intracranial pressure in the surrounding ipsilateral and contralateral brain. Any decrease in brain absorption is an equivalent to brain ischemia. This study demonstrates the capability of optical imaging in detecting brain ischemia and hemorrhage in real-time with high temporal and spatial resolution.

Transabdominal chorionic villus sampling at 9.5-12 weeks' gestation. Placental vascular resistance and fetal cardiovascular responses.

Pregnancies subjected to chorionic villus sampling (CVS) have been associated with transverse limb reduction defects. This study was designed to examine the possible fetal cardiovascular responses to transabdominal CVS. We examined 42 patients referred for CVS between 9.5 and 12 weeks' gestation. CVS was performed transabdominally under ultrasonic guidance with a 20-gauge needle. Placental vascular resistance was evaluated by means of the umbilical artery pulsatility index. Fetal heart rate was ascertained automatically from two successive flow velocity waveforms. Paired t test, regression analysis, power analysis and normal distribution analysis were performed, and statistical significance was set at P < or = .05. Fetal heart rate increased with increasing amounts of tissue, but placental vascular resistance did not change. The earlier the gestation, the larger the amount of tissue obtained. Multiple regression analysis demonstrated that the fetal heart rate change was influenced by neither gestation nor placental vascular resistance after CVS. Analysis of the change (difference before and after CVS) in placental resistance and fetal heart rate according to gestational age and amount of tissue did not change the above findings. Although statistically significant fetal cardiovascular responses can be elicited in relation to the amount of chorionic villi obtained during transabdominal CVS, the clinical significance of these findings remains unclear, given the fact that all the fetuses in this group of patients were normal. These responses may be secondary to various degrees of placental hemorrhage and may represent part of or the total fetal response to various degrees of fetal blood loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Compliance-weight deficit index. Combining umbilical artery resistance and growth deficit for predicting intrauterine growth retardation and poor perinatal outcome.

One hundred sixty-six patients underwent examination of the umbilical artery (UA) by continuous wave Doppler ultrasound one week prior to delivery. The UA compliance deficit (CD) and weight deficit (WD) were combined into an index (CWDI) by a formula based on the Pythagorean Theorem. CWDI represents the hypotenuse, and CD and WD represent the two perpendicular lines of a triangle: (CWDI = square root of CD2 + WD2). Perinatal outcomes were evaluated by the number of perinatal deaths, delivery for fetal indications prior to 37 weeks' gestation, five-minute Apgar score < 7, neonatal intensive care unit (NICU) admission and the presence of intrauterine growth retardation (IUGR). A CWDI value of > or = 20 was the most discriminatory in identifying fetuses with poor outcomes. Fetuses with CWDI > or = 20 were more likely to be premature (P < .001) or growth retarded (P < .001) or have lower Apgar scores (P < .005) and longer NICU stays (P < .001). Seven of the eight perinatal deaths occurred in patients with abnormal CWDI (P < .001). The sensitivity of an abnormal CWDI was 95% for IUGR, 60% for preterm delivery, 82% for NICU admission, 90% for Apgar score < 7 at five minutes, 87% for perinatal mortality and 68% for overall poor perinatal outcomes. CWDI is a sensitive index for the identification of fetuses with IUGR and poor perinatal outcome.

Small-for-menstrual-age infants: different subgroups detected using individualized fetal growth assessment.

Our purpose was to study the individual fetal growth patterns of infants who were born small-for-menstrual-age. Growth in the second and third trimester was assessed in 98 small-for-menstrual-age infants, using individual fetal growth curves generated by the growth model: P = c(t)k+s(t). Growth indices were compared with those previously reported for that method in infants with normal growth. The small-for-menstrual-age infants were distributed into four growth patterns, ie, infants with either normal or decreased second-trimester growth indices, who, by the time of birth, succeed or fail in fulfilling their individual growth potential. These four growth patterns appear to be associated with different pathophysiological mechanisms and incidences of perinatal complications. Individual fetal growth assessment identifies differences in genetically determined growth and differentiates between fetuses who achieve their growth potential and those with growth failure who are at greater risk for fetal compromise.

Prenatal diagnosis of fetal pelvic kidney. A case report.

Published experience on prenatal diagnosis of pelvic kidney is limited. We present the ultrasonographic characteristics of a case of ectopic pelvic kidney and discuss the significance of prenatal diagnosis.

Functional asymmetry of the human myometrium documented by color and pulsed-wave Doppler ultrasonographic evaluation of uterine arcuate arteries during Braxton Hicks contractions.

OBJECTIVE: We hypothesized that arcuate arteries supplying placental and nonplacental myometrial portions would respond with different degrees of change in their resistance during Braxton Hicks contractions. STUDY DESIGN: We examined 20 healthy pregnant women between 18 and 24 weeks' gestation with pulsed-wave and color-flow Doppler during focal Braxton Hicks contractions identified by real-time ultrasonography by means of the characteristic thickening of the myometrium. Systolic/diastolic ratio was used as an expression of resistance. Statistical analysis was performed by Wilcoxon signed-ranks and Mann-Whitney test. RESULTS: When the contractions are localized in the subplacental myometrium, the resistance of the arcuate artery did not differ during and after the contraction. In contrast, when the contraction involved only nonplacental myometrium, the resistance during the contraction was significantly higher and in some patients there was complete absence of flow during the diastolic phase. During subplacental myometrial contractions, the main uterine artery resistance was not affected. When the contraction involved the nonplacental myometrium, the resistance of the main uterine artery increased with more pronounced changes when the contraction involved the lateral myometrial wall ipsilateral to the uterine artery under examination. CONCLUSION: We speculate that the differences in the degree of resistance change are the result of different degrees of contractility exhibited by the subplacental and nonplacental myometrium. We conclude that the intact human myometrium manifests functional asymmetry and our Doppler findings confirm previous in vitro studies.

Atrial natriuretic factor concentrations during pregnancy and in the postpartum period.

Atrial natriuretic factor (ANF) is a hormone that regulates fluid and electrolyte homeostasis. Increased intra-atrial pressure or atrial distention, which might occur secondary to intravascular volume expansion, stimulate the secretion of ANF by human atrial myocytes. During normal human pregnancy, there is a progressive increase in total intravascular fluid volume. Thus, we asked the following question: Does this physiologic adaptation to pregnancy result in an increase in ANF concentrations? Concentrations of alpha-human ANF (alpha-hANF) were measured by a specific radioimmunoassay in venous blood samples obtained longitudinally in the first, second, and third trimesters of pregnancy, during the intrapartum period, in the early postpartum period, and 6 to 8 weeks postpartum from 11 normal women who had no antepartum, intrapartum, or postpartum complications. Maternal circulating alpha-hANF levels were not different from those seen in the nonpregnant state. However, higher alpha-hANF concentrations were noted in the early postpartum period. Although the hypervolemia of normal pregnancy is not associated with higher alpha-hANF concentrations, other possibilities (such as increased ANF clearance, dilutional effects) need to be investigated. Finally, the etiology for the transient increase in alpha-hANF levels in the early postpartum period remains to be elucidated.

Comparison of fetal cerebellar measurements by two different techniques.

We examined 53 fetuses between 15 and 40 weeks of gestation with transverse and coronal sections of the head in order to evaluate the accuracy and reproducibility of the coronal cerebellar diameter. Intraobserver coefficient of variation was less than or equal to 2.2% and the mean interobserver difference was 2.2% (range, 0 to 6%). A positive linear correlation exists between transverse and coronal measurements (coronal diameter = 1.02 x transverse diameter - 0.48; R2 = 0.99; P less than 0.0001). We conclude that the coronal cerebellar diameter is reproducible and accurate and when indicated clinically can be used instead of the transverse cerebellar diameter when the latter is not obtainable because of fetal position.

Intraoperative amniocentesis and indomethacin treatment in the management of an immature pregnancy with completely dilated cervix.

We performed cervical cerclage on a completely dilated and effaced cervix after decompression of the amniotic sac with intraoperative amniocentesis. Indomethacin was used for tocolysis and to maintain mild oligohydraminios (amniotic fluid index 5-7 cm). The pregnancy was prolonged by 12 days and a viable infant was delivered at 25 weeks' gestation.

Effect of measurement variability on Rossavik growth model specification and prediction of growth outcome at birth.

We have studied how variability in second-trimester ultrasound measurements affects the process of fetal growth evaluation based on individual fetal growth curve standards specified by Rossavik growth models. The head and abdominal short axes of two second-trimester scans of a patient with normal fetal growth were increased or decreased by increments ranging from 0.1 cm to values equal to the two standard deviations of the interobserver variability for these measurements--i.e., 0.3 cm for head short axis and 0.4 cm for abdominal short axis. The largest increments affected the Growth Potential Realization Index for weight at birth by 1% to 13% when applied to head short axis, and by 2% when applied to abdominal short axis. In contrast, the same increments had little effect (1%) on the Growth Potential Realization Indices for head and abdominal circumferences. Whereas 0.1-cm increments had no effect on any of the individual growth models or predicted birth characteristics, some combinations of these small errors involving both head and abdominal short axes changed the Growth Potential Realization Index for weight by as much as 15%, and those for head and abdominal circumferences by 3% and 8%, respectively. Under some scenarios, fetal growth status could be falsely classified as normal or abnormal. These results show that the reliability of individualized growth assessment depends to a great extent on excellent ultrasound technique, at least for certain parameters.

Uteroplacental Doppler flow velocity waveform indices in normal pregnancy: a statistical exercise and the development of appropriate reference values.

In a prospective cross-sectional study, we examined 154 normal pregnant women and measured the systolic to diastolic (S/D) ratio and resistance index (RI) in the umbilical artery and both uterine arteries. Placental location with respect to laterality was determined by real-time ultrasound. In patients with unilateral placental location, each uterine artery was evaluated according to its relationship with the placenta. Doppler flow velocity waveforms were obtained by a continuous wave Doppler device. Kolmogorov D tests revealed that RI values follow gaussian distribution, but that S/D values were markedly skewed to the right. There was a significant negative linear relationship between gestational age and umbilical artery RI and a significant negative curvilinear relationship between gestational age and umbilical artery (S/D (r = 0.83, p less than 0.001; and r = -0.79, p less than 0.001, respectively). Confidence bands for umbilical artery RI were developed based on the linear model with gestational age (fitted umbilical artery RI = 0.97199 - 0.01045*gestational age). Confidence bands for umbilical artery S/D were derived from the corresponding RI values by means of the functional relationship S/D = 1/(1 - RI). The RI and S/D values of the uterine arteries declined until 24 to 25 weeks' gestation and remained unchanged thereafter. This relationship, however, was not statistically significant (r = -0.10, p = 0.22). The placental uterine artery is different from the nonplacental quantitatively and qualitatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelationship and clinical significance of increased resistance in the uterine arteries in patients with hypertension or preeclampsia or both.

OBJECTIVES: This study was designed to evaluate the clinical significance of the Doppler flow velocity waveform analysis of the two uterine arteries on an individual basis and in combination expressed as the mean uterine artery. STUDY DESIGN: We evaluated uterine artery resistance by means of continuous wave Doppler ultrasonography in 123 pregnant women with chronic hypertension, preeclampsia, or both. The placental location was determined by real-time ultrasonography. Clinical outcomes were compared according to uterine artery abnormalities. The Doppler flow studies were not used in patient management. RESULTS: In patients with unilateral placentas (n = 67) the placental uterine artery was found to be a better predictor of poor pregnancy outcome than the nonplacental artery and the mean of the two arteries. There was a strong degree of correlation between abnormal nonplacental uterine artery and abnormal mean of uterine artery (r = 0.75, p less than 0.001), and there was a moderate degree of correlation between abnormal placental uterine artery and abnormal mean uterine artery (r = 0.46, p less than 0.001). Uterine artery discordance (left-right uterine artery systolic/diastolic ratio) was mostly the result of an abnormal nonplacental uterine artery (r = 0.74, p less than 0.0001) and not the result of an abnormal mean uterine artery (r = 0.44, p less than 0.003); the degree of discordance did not relate to pregnancy outcome. Unilateral placental location was associated with longer stays in neonatal intensive care units and more perinatal deaths. CONCLUSION: Because of the differences between the two uterine arteries, we conclude that for proper interpretation of uterine artery flow velocity waveforms, the placental location should be known and each vessel analyzed individually.

Treatment of fetal supraventricular tachycardia with flecainide acetate after digoxin failure.

Transplacentally administered digoxin is the drug of choice for the treatment of fetal supraventricular tachycardia. We describe a case of fetal supraventricular tachycardia associated with fetal hydrops that did not respond to digoxin treatment because of a lack of transplacental passage. In contrast, flecainide acetate crossed the placenta and cured the fetus. The clinical implications of this new treatment are discussed.

Uteroplacental Doppler flow velocity waveform analysis correlates poorly with glycemic control in diabetic pregnant women.

We examined 65 pregnant women with gestational (n = 31) and insulin dependent (n = 34) diabetes mellitus in order to evaluate the clinical usefulness of Doppler flow velocity waveform analysis in these pregnancies. Umbilical and uterine artery flow velocity waveforms were obtained during the third trimester with a continuous wave Doppler device. Quality of maternal glycemic control was evaluated by hemoglobin (Hb) A1 measurements at the time of delivery in 61 patients and by mean capillary blood sugars during the third trimester of pregnancy in four patients. There was no difference in various clinical and Doppler parameters between patients with good glycemic control and those with poor control. In contrast, the same clinical and Doppler parameters were significantly different in patients with preeclampsia than in those without preeclampsia, regardless of glycemic control. There was a poor positive linear correlation (r = 0.30, p less than 0.02) between maternal HbA1 and umbilical artery flow velocity waveforms (systolic/diastolic ratio). Proteinuria correlated better with umbilical artery systolic/diastolic ratio (r = 0.49, p less than 0.001). We conclude that Doppler flow velocity waveform analysis may be clinically useful only in diabetic pregnancies complicated by preeclampsia.

Detection of macrosomia by the individual fetal growth curve assessment method.

The value of the Rossavik growth model [P = c(t)k + s(t)] was evaluated in 39 patients with singleton pregnancy who had neonatal weight outcome above the 90th percentile of our birth weight distribution for gestational age. Individual fetal growth curve standards for head and abdominal circumferences, femur diaphysis length, and weight were determined from the data of two scans obtained before 26.1 weeks' gestation and separated by an interval of at least 5 weeks. Projected crown-heel lengths were calculated from projected femur diaphysis length values. Comparisons between actual and predicted birth characteristics were expressed by the Growth Potential Realization Index (GPRI) and Neonatal Growth Assessment Score (NGAS). Excessive growth at birth was seen in almost all cases as indicated by high GPRI for weight and abdominal circumference and abnormal NGAS values. In eight of the 33 patients who delivered after 38 weeks, excessive growth was detected only by comparing birth characteristics to their predicted values at 38 weeks' gestation. Our data suggest that individual growth curve standards may identify several patterns of excessive fetal growth that could represent different pathophysiologic mechanisms, ie, failure to terminate growth after 38 weeks versus a defect in a still unknown growth regulator. The individual fetal growth curve standards method gives additional information and discriminates well between normal and excessive fetal growth.

Umbilical vessel flow velocity waveforms in cord entanglement in a monoamnionic multiple gestation. A case report.

An unusual flow velocity waveform pattern was seen in a case of cord entanglement in a monoamnionic multiple pregnancy. The umbilical artery systolic:diastolic ratio was abnormally high (greater than 95th percentile for gestation), and diastolic notching was present. The umbilical vein flow velocity waveform was pulsatile, with flow absent during the diastolic phase of the cardiac cycle. The presence of that pattern strongly suggested a severe cord accident and mandated an immediate evaluation of fetal well-being.