Umbilical vein blood volume flow rate and umbilical artery pulsatility as 'venous-arterial index' in the prediction of neonatal compromise.

OBJECTIVE: To assess the diagnostic power of the umbilical venous-arterial index (VAI) for the prediction of poor fetal outcome. SUBJECTS AND METHODS: This was a retrospective, cross-sectional clinical study in which normalized umbilical vein blood volume flow rate (nUV) (mL/min/kg estimated body weight), umbilical artery pulsatility index (UAPI), the newly developed VAI (nUV/UAPI), and the uterine artery resistance index (UTRI) were determined in 85 fetuses once (17-41 gestational weeks) during pregnancy using standard ultrasound Doppler equipment. A risk score based on umbilical blood pH, 1-min Apgar score, birth weight, duration of gestation, type of respiratory support, and referral to the pediatric department was constructed, and fetuses were assigned to a control or a pathological group accordingly. Logistic regression and analysis of fitted receiver-operating characteristics curves were performed to evaluate the diagnostic power of nUV, UAPI, UTRI, and VAI. RESULTS: The incidence of compromised neonates was 17.6%. The area under the receiver-operating characteristics curve was larger for VAI than for UTRI or for UAPI (P < 0.002). At a cut-off value of 100 mL/min/kg, the sensitivity of VAI to predict poor neonatal outcome was 85% with a 15% false-positive rate. CONCLUSION: Determination of the VAI has a greater diagnostic power to predict poor fetal outcome than the pulsatility index in the umbilical artery or the resistance index in the uterine artery.

[Uteroplacental and fetal arterial Ultrasound Doppler Flow Velocity measurements in unselected pregnancies as a screening test at 32 to 34 gestational weeks]. / Dopplersonographische Blutflussmessungen in uterinen und fetalen arteriellen Gefässen als Screeninguntersuchung in der 32. - 34. Schwangerschaftswoche.

OBJECTIVE: We hypothesized a difference in mean values for ultrasound biometry and Doppler flow velocity measurements in uteroplacental and fetal arterial vessels between subgroups with a subsequent normal and pathological [pathological fetal heart rate tracing, operative delivery due to fetal distress, thick meconium, IUGR < 10th centile, prematurity < 37 weeks, APGAR 5' < 7, umbilical artery pH < 7.20, neonatal pediatric hospitalisation] birth result in unselected pregnancies screened at 32 to 34 gestational weeks. PATIENT CHARACTERISTICS AND METHODS: After having obtained informed consent we included 198 singleton pregnancies in an open prospective study and performed a single ultrasound assessment at 32 to 34 gestational weeks to collect biometry and Doppler flow velocity data: angle independent resistance indices (RI, PI) for uteroplacental and umbilical arteries, RI, PI and Vmean (mean blood flow velocity) after angel correction for fetal descending aorta and middle cerebral arteries, (ATL, Ultramark 9, HDI ESP, 4 - 7 MHz curved and 3 - 5 MHz phased array). After delivery, perinatal and neonatal data were collected and pregnancies were grouped accordingly (normal and pathological birth result). RESULTS: Of 198 pregnancies included, 58 fulfilled at least one of the established criteria for a pathological birth result and 17 were born growth restricted (< 10th centile) and/or prematurely (< 37 gestational weeks). Within subgroups (normal /pathological birth result) mean values only differed for uteroplacental RI (p=0.07) and aortic Vmean (p=0.04). Differences were highly significant for normally versus growth restricted/prematurely born fetuses: uteroplacental RI (p=0.01), fetal descending aorta PI (p=0.02) and Vmean (p=0.001), and middle cerebral artery PI (p=0.0008). CONCLUSION: Elevated uteroplacental Doppler flow velocity waveform indices and reduced aortic blood flow velocity might be associated with a pathological birth result and an impaired neonatal status after birth in cohorts of unselected pregnancies.

[Hypertensive disorders in pregnancy]. / Hypertensive Erkrankungen in der Schwangerschaft.

BACKGROUND: Hypertensive complications contribute to maternal and fetal morbidity. Hypertensive diseases in pregnancy comprise various disorder from transient hypertension to the dangerous preeclampsia/eclampsia. Diagnosis of these diseases requires an understanding of the normal physiological adaptations during pregnancy. PATHOGENESIS: The primary cause of preeclampsia/eclampsia is a disturbed growth of throphoblast cells, probably induced by an altered maternal immunotolerance. The consequence is a dysfunction of endothelial cells with a decrease in perfusion of the uterus and placenta. The normal balance between vasoconstrictors and vasodilators is changed in favor of vasoconstrictors. Complex changes in the renin-angiotensin system have been detected resulting in an increased angiotensin II-mediated vasoconstriction. The reduction in perfusion of the uterus and placenta eventually leads to preeclampsia/eclampsia and growth retardation of the fetus. Manifest preeclampsia/eclampsia is characterized by disturbed microcirculation of target organs such as brain, liver and kidney. An involvement of the liver causes the HELLP syndrome. THERAPY: Various pharmacological approaches to prevent preeclampsia/eclampsia showed disappointing results, but patients with a risk for the eventual development of preeclampsia/eclampsia should be identified, closely monitored, and hypertension should be treated. A systolic blood pressure > 170 mm Hg and diastolic blood pressure > 100 mm Hg should be treated. Drugs such as alpha-methyldopa and dihydralazine that are well-characterized in their fetal effects are the primary choice for the treatment of hypertension in pregnancy. ACE-inhibitors and angiotensin II receptor antagonists are absolutely, diuretics are relatively contraindicated. The causal therapy for preeclampsia/eclampsia is delivery. Gravida before the 33th week of pregnancy should be admitted, hypertension should be treated, and the fetus should be monitored by duplex ultrasound and cardiotocography. New data suggest that early treatment with glucocorticoids may prevent the manifestation of HELLP syndrome. Hypertensive pregnant patients should be treated in tertiary centers with an interdisciplinary approach involving obstetricians, neonatologists, and nephrologists.

BK(Ca) channel activation by membrane-associated cGMP kinase may contribute to uterine quiescence in pregnancy.

We investigated the influence of pregnancy on large-conductance calcium-activated potassium channel (BK(Ca)) activity (NP(o)) and on channel expression in membranes of isolated human myometrial smooth muscle cells. NP(o) in inside-out patches was higher in pregnant myometria (PM) compared with nonpregnant myometria (NPM), and the half-maximal activation potential was shifted by 39 mV to more negative potentials. This effect was not due to an enhanced BK(Ca) channel expression. In the presence of cAMP kinase (PKA) or cGMP kinase (PKG), NP(o) increased in patches from PM but decreased in those from NPM. Western blot analysis and use of a specific PKG inhibitor (1 microM KT-5823) verified the existence of a partially active membrane-associated PKG. Inhibition of PKA by 100 nM PKI, the inhibitory peptide of PKA, had no effect on NP(o). 8-p-Chlorophenylthio-cGMP (8-pCPT-cGMP) hyperpolarized cells from PM. This effect was abolished by iberiotoxin, a specific blocker of BK(Ca) channels. It is concluded that an endogenous, membrane-bound PKG in myometrial cells specifically enhances BK(Ca) channel activity during pregnancy and thus may contribute to uterine quiescence during pregnancy.

Pregnancy switches adrenergic signal transduction in rat and human uterine myocytes as probed by BKCa channel activity.

1. We used large conductance Ca2+-activated K+ (BKCa) channel activity as a probe to characterize the inhibitory/stimulatory G protein (Gi/Gs) signalling pathways in intact cells from pregnant (PM) and non-pregnant (NPM) myometrium. 2. Isoprenaline (10 microM) enhanced the outward current (Iout) in PM cells and inhibited Iout in NPM cells. Additional application of the alpha2-adrenoceptor (alpha2-AR) agonist clonidine (10 microM) further enhanced the isoprenaline-modulated Iout in PM cells but partially antagonized Iout in NPM cells. Clonidine alone did not affect Iout. The specific cAMP kinase (PKA) inhibitor H-89 (1 microM) abolished the effects of isoprenaline and clonidine. The specific BKCa channel blocker iberiotoxin (0.1 microM) inhibited Iout by approximately 80 %; the residual current was insensitive to isoprenaline. 3. Inhibition of Gi activity by either pertussis toxin or the GTPase activating protein RGS16 abolished inhibitory as well as stimulatory effects of clonidine on Iout. 4. Transducin-alpha, a scavenger of Gi betagamma dimers, converted the stimulatory action of clonidine on Iout into an inhibitory effect. Free transducin-betagamma enhanced both the stimulatory and the inhibitory effects of isoprenaline on Iout. 5. The results demonstrate that BKCa channel activity is a sensitive probe to follow adenylyl cyclase-cAMP-PKA signalling in myometrial smooth muscle cells. Both Gialpha-mediated inhibition and Gibetagamma-mediated stimulation can occur in the same cell, irrespective of pregnancy. It is speculated that the coupling between alpha2-AR and Gi proteins is more efficient during pregnancy and that Gibetagamma at high levels simply override the inhibitory action of Gi alpha.

Detection of Intramural Choriocarcinoma of the Uterus with 18F-FDG-PET. A Case Report.

We are reporting the case of a 37-year-old woman with rising beta-human chorionic gonadotropin (HCG) levels over 4 years. Curettage was performed 5 times and diagnostic laparoscopy twice, but no trophoblastic tissue was found. Vaginal ultrasound and power Doppler sonography showed a solid tumor of the anterior uterus wall with high vascularization. 18F-2-deoxy-D-glucose-positron emission tomography (FDG-PET) revealed a single focus of FDG uptake in projection of the uterus. Sonographically, the tumor of the uterus appeared like a leiomyoma. Thus focal FDG uptake was the sole indicator for a malignant trophoblastic tumor. Histological examination of the tumor revealed a choriocarcinoma.

[Recent developments in obstetric regional anesthesia. A review of experiences at the Eppendorf University Hospital]. / Aktuelle Entwicklungen der geburtshilflichen Regionalanästhesie. Eine Ubersicht am Beispiel des Universitäts-Krankenhauses Eppendorf.

OBJECTIVES: The study investigates changes of anaesthesia practice in obstetric patients of a University Hospital over a six years' period. METHODS: Between 1993 and 1998 data of 7476 deliveries were collected by the perinatal documentation system of the Obstetric Department and by computerized anaesthesia protocols of the Department of Anesthesiology. Since combined spinal-epidural anaesthesia with sufentanil was introduced in 1997, all patients with subarachnoid techniques were prospectively examined between 1997 and 1998. RESULTS: While the total number of deliveries decreased over the years, the number of patients undergoing anaesthetic treatment increased continuously. In parallel, the number of patients with regional anaesthesia increased between 1993 and 1998 from 14.3% to 34.8%. The cesarean delivery rate increased from 23.7% to 28.7% with an increasing number of patients receiving regional anaesthesia for cesarean section (1993: 25.3% vs. 1998: 62.1%). The number of emergency cesarean deliveries performed in regional anaesthesia increased to 19.3% in 1998. The number of neonates with an umbilical artery pH below 7.2 decreased from 18% in 1993 to 11% in 1998. The success rate of regional anaesthesia increased from 88.2% in 1993 to 97.5% in 1998. Combined spinal-epidural anaesthesia provided greater pain reduction when compared with epidural anesthesia (VAS -81 +/- 12 vs. -68 +/- 18). Early vasopressor administration resulted in a decrease of hypotension from 40% to 14% in spinal and from 21% to 13% in combined spinal-epidural anaesthesia. The incidence of postdural puncture headache after subarachnoid anaesthesia was 2.4%. DISCUSSION: Epidural and subarachnoid application of sufentanil appears to enhance the success rate of obstetric regional anaesthesia. Subarachnoid techniques such as spinal or combined spinal-epidural anaesthesia showed a high effectiveness, low incidence of side effects and high degree of patients' satisfaction.

Blood flow through the ductus venosus in singleton and multifetal pregnancies and in fetuses with intrauterine growth retardation.

OBJECTIVE: It is known from animal experiments that blood flow through the ductus venosus changes with fetal strain. Therefore the ratio of umbilical vein to ductus venosus flow rate in human intrauterine growth retardation and multifetal pregnancies was investigated and compared with that in control subjects. STUDY DESIGN: Blood flow rates in the umbilical vein and in the ductus venosus, as well as peak velocity, minimum velocity, mean velocity, and pulsatility index (maximum velocity envelope curve) in the ductus venosus, were measured in women with normal pregnancies (n = 55), intrauterine growth retardation (n = 20), and multifetal pregnancies (10 women with 20 fetuses) with color Doppler ultrasonography. RESULTS: Average ductus venosus blood flow rates (mean +/- SD), normalized for estimated fetal body weight, were 60 +/- 30, 69 +/- 35, and 77 +/- 28 (ml x min(-1) x kg(-1)) in control subjects, intrauterine growth retardation, and multifetal pregnancies, respectively. Umbilical vein blood flow rates amounted to 140 +/- 59, 111 +/- 54, and 141 +/- 47 (ml x min(-1) x kg(-1)). Both absolute flow rates increased with gestational age, whereas normalized flow rates decreased. The percentage of umbilical blood flow passing through the ductus venosus in the control group was 43% + 9%. It was significantly increased in both intrauterine growth retardation (62% +/- 8%) and in multifetal pregnancies (55% +/- 12%). Peak velocity, minimum velocity, mean velocity, and pulsatility index in the ductus venosus were not significantly different between groups. CONCLUSION: The increased ratio of ductus venosus blood flow to umbilical vein blood flow may indicate fetal strain.

Combining B-mode ultrasound with pulsed wave Doppler for the assessment of tubal patency.

This study was conducted to determine whether the additional use of pulsed wave Doppler improves the diagnostic capacity in assessing tubal patency by hysterosalpingo contrast sonography (HyCoSy). A total of 210 women with a history of infertility were included in this study. HyCoSy was performed after intrauterine injection of Echovist 200. For the assessment of tubal patency B-mode scanning and pulsed wave Doppler ultrasound were performed in the proximal and distal tubal segments. With the combined sonographic procedure 297 tubes (74%) were rated patent, 35 (8%) incompletely obstructed and 70 (18%) completely obstructed. A total of 252 tubes were additionally examined by laparoscopy for reference purposes. Concordant results for both methods were found in 92% of tubes, nine had been rated false negative and 10 tubes appeared to have been rated false positive. The combined sonographic specificity was found to be 85% with a sensitivity of 95%. Peritubal adhesions detected by laparoscopy were found to be the reason for false positive sonographic results in 60% of cases. In conclusion, the combined B-mode and pulsed wave Doppler examination appears to be a non-invasive and low-cost test for the assessment of tubal patency, which should be performed during diagnostic work-up for infertility.

Bleeding esophageal duplication detected in utero.

Peptic complications in duplications of the alimentary tract may occur when the duplication is lined by gastric mucosa. These complications commonly develop in the first year of life. We report a case of a bleeding esophageal duplication in a fetus.

[Normal values for relative Doppler indices. A/B ratio, resistance index and pulsatility index of the uterine artery and umbilical artery in normal pregnancy. A longitudinal study]. / Normalbereiche für die relativen Doppler-Indizes. A/B-Ratio, Resistance-Index und Pulsatilitäts-Index der Arteria uterina und Arteria umbilicalis bei ungestörter Schwangerschaft. Eine Längsschnittstudie.

37 women (of a total of 50) with an uneventful obstetric history, normal course of a singleton pregnancy and spontaneous delivery at term (> 37 weeks, birthweight > 10th centile) were studied at two to four weeks intervals in a longitudinal design using cw-Doppler velocimetry (Doptek 9013,4MHz, SPTA 30 mWcm2, high pass filter 200 Hz, Chichester, U.K.) to establish normal reference values for Doppler flow velocity waveform indices (DI) A/B ratio, RI, PI obtained from uterine and umbilical arteries from 16 to 40 weeks of gestation. Readings from the placental (p) and non-placental (np) uterine and umbilical arteries formed the database from which percentiles (5th, 50th, 95th) were calculated for weeks 16, 20, 24, 28, 32, 36 and 40 of gestation. DI consistently decreased from week 16 to term. For the uterine arteries this decrease was significant from weeks 16 to 24 with a further but insignificant decrease from 24 weeks to term. Up to 24 weeks DI values obtained from the placental side were significantly lower than those from the non-placental side. DI values from the umbilical arteries decreased continuously from 16 weeks to term with a significantly negative correlation DI values to gestational age.

[Estimating the peripheral vascular resistance of the aorta of fetal sheep by external Doppler ultrasound diagnosis]. / Abschätzung des peripheren Gefässwiderstandes in der Aorta des fetalen Schafes durch externe Dopplersonographie.

OBJECTIVE: Do external Doppler indices correlated sufficiently to the peripheral resistance? METHODS: The resistance of 7 fetal sheep was measured inductively and was correlated to external Doppler measurements. The correlation of different indices and methods was compared. RESULTS: Only bloodflow velocities and the harmonic component index (HCI) yield good correlations (r > or = 7) to the peripheral resistance. PI, RI, S/D-Ratio and Vpeak/Vmean showed r-values from .47 to .59. None of the Doppler parameters reached the values of indices derived from the inductive flow probe. CONCLUSIONS: The blood flow velocities and the HCI seem to be superior to the classical indices in estimation of blood flow in the fetal aorta.

Input impedance of the lower abdominal aorta in chronically instrumented fetal sheep.

Five fetal sheep (gestational age, 118 to 125 days) were instrumented to measure impedances of the lower abdominal aorta. Four days after surgery, flow and pressure pulses were recorded during control conditions and during infusion of norepinephrine (0.3 to 3 micrograms.min-1.kg-1 body weight) or angiotensin II (0.2 to 3 micrograms.min-1.kg-1). The protocol was repeated after injection of hexamethonium (10 mg.kg-1). Moduli and phases of impedances for the first ten harmonics were calculated by fast Fourier transformation. During control, input resistance was 4300 +/- 940 dyne.s.cm-5 (mean +/- SD) at a mean blood flow of 13.3 +/- 2.4 cm3.s-1 and pressure of 54,960 +/- 6980 dyne.cm-2. Moduli fell to 50% of input resistance between 2 and 3 Hz and, declining continuously, reached a minimum of 20% near 10 to 12 Hz, then increased slightly to 30% at about 30 Hz. At the first three harmonics, flow was always leading pressure. Infusion of angiotensin or norepinephrine increased impedance moduli significantly. Resistance increase was largest with angiotensin (19,800 +/- 11,370 dyne.s.cm-5), but no difference was detectable between angiotensin and norepinephrine when related to the same increase of input resistance. The position of the minimum seemed to be unchanged at high resistance values, but relative impedance moduli were smaller than during control, and low-frequency phases were significantly more negative. An analog of inertance, compliance, and resistance to steady flow was used to simulate impedances, and the effect of resistance increases on flow waveforms in the fetal abdominal aorta was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

[Prenatal diagnosis of malignant intracranial teratoma in the fetus]. / Pränatale Diagnostik eines fetalen malignen intrakraniellen Teratoms.

At 24 weeks of gestation, an intracranial cystic lesion of 3 cm diameter, without further associated foetal malformations, was detected by ultrasound in a 25-year old nullipara prima gravida, during routine prenatal care. Within 5 weeks, the cystic mass developed into a predominantly solid tumour located at the 3rd ventricle, showing patterns of a rapidly growing malignant intracerebral process. At 29 weeks of gestation, pregnancy was terminated by sectio parva because of a progressive hydrocephalus with a biparietal diameter of 10.2 cm. Autopsy confirmed a malignant teratoma. Foetal intracranial teratomas are rare. Diagnosis and therapy should be carried out in perinatal centres.

Perinatal outcome in fetuses with loss of end-diastolic blood flow velocities in the descending aorta and/or umbilical arteries.

Continuous- and pulsed-wave Doppler velocimetry was used as an additional method of antenatal surveillance in high-risk pregnancy care. During a 30-month period with 4,169 deliveries 226 patients (5.4%) with complicated pregnancies (intrauterine growth retardation, diabetes, hypertension) were investigated. The results had only marginal influence on obstetrical management. In 38 fetuses absence of end-diastolic blood flow velocities (AEDF) was detected in the descending fetal aorta and/or umbilical arteries. Mean birth weight of these fetuses was 1,441 +/- (SD) 690 g at a mean gestational age of 31.8 +/- 6.8 weeks at birth. Twenty fetuses (53%) were growth-retarded (less than 3rd centile). Six fetuses died in utero and 7 during the perinatal period (34% mortality). There was a significant deterioration of perinatal outcome with AEDF in the umbilical arteries at the last antenatal Doppler scan. With AEDF in the descending fetal aorta the Doppler parameter Vmean and with AEDF in the umbilical arteries the pulsatility index yielded additional prognostic information. Doppler velocimetry of the fetal and umbilical vascular system could be of additional value for antenatal surveillance in high-risk pregnancies.

[Early amniocentesis for cytogenetic diagnosis]. / Frühzeitige Amniozentese zur zytogenetischen Diagnostik.

This study was designed to assess the feasibility of amniocentesis and amnion cell culture for prenatal diagnosis in early weeks of gestation (less than 15 weeks). Within a period of 18 months (1/88-6/89) 135 diagnostic amniocenteses were performed between 10 and 14 weeks and amniotic fluid was obtained in all instances. In all cases but one, sufficient cell cultures and chromosomal analyses were achieved. In the follow up, one miscarriage (0.7%) occurred, in two cases transient amniotic fluid leakage ceased spontaneously. All of the aforementioned complications were related to amniocenteses in weeks 11 and 12. The course of the continued pregnancies as well as fetal outcome were without any further complications. Comparing specimens of early and regular (16-18 weeks) amniocenteses in terms of time required for cell culture and karyotyping as well as the quality of chromosomal banding no significant differences were found. In contrast to maternal serum AFP which increased continuously, amniotic AFP levels could be seen to increase to a peak at 13 weeks' gestation but afterwards gradually declined. Based on these first experiences and results of early amniocenteses the specific problems of this method are discussed. In summary, it is concluded, that early amniocentesis between 12 and 14 weeks of gestation is feasible with regard to both the technique of amniotic fluid retrieval and the technique of chromosomal analysis. Early amniocentesis, therefore, could fill up the diagnostic gap between chorionic villi sampling (CVS) between 9 and 11 weeks of gestation and "classical" amniocentesis during weeks 16-18.

Pulsed wave Doppler velocimetry in the descending aorta of chronically instrumented fetal sheep.

Pulsed wave Doppler sonography was used to determine peak systolic velocity (Vpeak), mean maximum velocity (Vmean) and Pulsatility Index (PI) in the descending aorta of chronically instrumented, unanesthetized fetal sheep (days 120-130 of pregnancy). Measurements were done 1-4 days after surgery using a duplex mechanical sector scanner (4.5 MHz) and offset attached pulsed wave Doppler probe (2.25 MHz) during periods of control, intrauterine cooling and rewarming. Mean values derived from the envelope curve of maximum shift frequencies were (controls): thoracic: Vmean 60.9 +/- 9.1 cm/sec, Vpeak 118.9 +/- 17.8 cm/sec, PI 1.57 +/- 0.24; abdominal: Vmean 49.6 +/- 10.9 cm/sec, Vpeak 98.9 +/- 20.4 cm/sec, PI 1.59 +/- 0.41. Vpeak was positively correlated to arterial pressure (r = 0.23) and PI showed an inverse correlation to heart rate (r = -0.22). During cold stress (reduction of fetal core temperature by 2.7 degrees C) and consecutive rewarming Vpeak and Vmean were positively correlated to fetal core temperature and arterial pressure (r = 0.2-0.26). PI revealed a weak negative dependency from core temperature and heart rate (r = -0.19 and -0.18 respectively).

Atrial natriuretic peptide and cyclic guanosine-3',5'-monophosphate in normal and pathological pregnancies.

The concentrations of atrial natriuretic peptide (ANP) and its presumed second messenger, cyclic guanosine-3',5'-monophosphate (cGMP) were determined in maternal plasma and amniotic fluid. Samples were obtained from normal and pathological pregnancies revealing hydramnios or severe Rh incompatibility between week 16 of gestation and delivery. For analysis of ANP and cGMP, radioimmunoassays were used. ANP and cGMP concentrations in maternal plasma did not differ in normal and pathological pregnancies. In amniotic fluid, we found ANP levels of about 120 pg/ml at 16 weeks of gestation which then decreased below the detection limit of 15.6 pg/ml. In contrast, cGMP levels were low at the beginning of pregnancy (4 pmol/ml) and rose significantly (14 pmol/ml), at the end of pregnancy. Pregnancies revealing severe Rh incompatibility exhibited the same levels as normal pregnancies when regular prenatal transfusions resulted in sufficient blood volume substitution. ANP, a volume-homeostasis-regulating hormone, is already produced in early pregnancy. The meaning of the presumed second messenger, cGMP, requires further investigation.

Fetal sheep temperatures in utero during cooling and application of triiodothyronine, norepinephrine, propranolol and suxamethonium.

Fetal sheep (n = 13) were chronically instrumented to measure temperatures in the maternal femoral artery (MAT), the amniotic fluid (AFT), the fetal brown adipose tissue (BFT) and the fetal arterial blood (DAT). Cooling loops were inserted into the amniotic cavity. In 4 fetuses osmotic minipumps delivering triiodothyronine (T3) were implanted subcutaneously. One to seven days after surgery the following results were obtained: 1) During control DAT was 0.59 +/- 0.2 degrees C (SD), BFT 0.60 +/- 0.24 degrees C and AFT 0.38 +/- 0.31 degrees C higher than MAT. T3 levels in treated fetuses were 3.4 +/- 1.5 micrograms/l. 2) Infusion of norepinephrine (NE) (5.2 +/- 0.9 micrograms/min per kg fetal body weight) with phentolamine (26.1 +/- 4.3 micrograms/min per kg) into a fetal vein did not change temperatures. 3) During cooling (-53 +/- 15 W) MAT decreased 0.45 +/- 0.3 degrees C, DAT 1.9 +/- 0.39 degrees C, BFT 1.61 +/- 0.52 degrees C and AFT 4.2 +/- 1.8 degrees C. 4) The amniotic fluid was cooled until steady state temperatures were achieved. Then propranolol (26.1 +/- 4.3 micrograms/min per kg) or suxamethonium (3 +/- 1 mg/kg) were introduced into the fetal vein. No consistent and significant changes of temperatures could be detected. It is concluded that 1) lowering the fetal core temperature by 1.6 - 1.9 degrees C and its ambient temperature (AFT) by 4.2 degrees C does not induce shivering or non-shivering thermogenesis suppressible by pharmacologic agents, 2) thermogenesis in fetal brown adipose tissue cannot be induced by NE (with or without supplemention of T3).(ABSTRACT TRUNCATED AT 250 WORDS)