Fetal Umbilical Venous Research Articles

Uptake of Halothane and Isoflurane by Mother and Baby During Caesarean Section

Twenty-three patients undergoing Caesarean section received either 0.5% halothane or 0.8% isoflurane to supplement nitrous oxide-oxygen anaesthesia. We studied the rate of uptake of the agents by the mother and fetus by measuring partial pressures in maternal arterial (Pa) and fetal umbilical venous (Puv) blood. Mean induction-delivery interval did not differ between the halothane (10.8 min) and isoflurane (11.7 min) groups. There were no differences in maternal heart rate, arterial pressure, pH and blood-gas tensions and fetal pH, blood-gas tensions or Apgar scores between the two groups. Isoflurane uptake by the mother was more rapid than halothane; at delivery, mean Pa of isoflurane as a fraction of the inspired partial pressure (Pl) was 0.44 compared with 0.35 for halothane (P < 0.05). Mean Puv as a fraction of maternal Pa at delivery was 0.71 for both agents; thus placental transfer was the same for both agents. Consequently mean Puv/Pl was greater for isoflurane (0.32) than halothane (0.26) (P < 0.05). We conclude that both halothane and isoflurane are suitable agents for general anaesthesia for Caesarean section. The rate of uptake of isoflurane by the mother during Caesarean section was more rapid than halothane. The rate of uptake by the fetus from the mother was the same for halothane and isoflurane, so that fetal partial pressure as a fraction of the inspired partial pressure was greater for isoflurane than halothane.

Uptake of halothane and isoflurane by mother and baby during Caesarean section

Twenty-three patients undergoing Caesarean section received either 0.5% halothane or 0.8% isoflurane to supplement nitrous oxide-oxygen anaesthesia. We studied the rate of uptake of the agents by the mother and fetus by measuring partial pressures in maternal arterial (Pa) and fetal umbilical venous (Puv) blood. Mean induction-delivery interval did not differ between the halothane (10.8 min) and isoflurane (11.7 min) groups. There were no differences in maternal heart rate, arterial pressure, pH and blood-gas tensions and fetal pH, blood-gas tensions or Apgar scores between the two groups. Isoflurane uptake by the mother was more rapid than halothane; at delivery, mean Pa of isoflurane as a fraction of the inspired partial pressure (Pl) was 0.44 compared with 0.35 for halothane (P < 0.05). Mean Puv as a fraction of maternal Pa at delivery was 0.71 for both agents; thus placental transfer was the same for both agents. Consequently mean Puv/Pl was greater for isoflurane (0.32) than halothane (0.26) (P < 0.05). We conclude that both halothane and isoflurane are suitable agents for general anaesthesia for Caesarean section. The rate of uptake of isoflurane by the mother during Caesarean section was more rapid than halothane. The rate of uptake by the fetus from the mother was the same for halothane and isoflurane, so that fetal partial pressure as a fraction of the inspired partial pressure was greater for isoflurane than halothane.

Fetal and maternal plasma endothelin levels during the second half of pregnancy

OBJECTIVE: Our objective was to evaluate maternal and fetal endothelin concentrations in uncomplicated pregnancies across the second half of pregnancy. STUDY DESIGN: Paired ( n = 64) maternal venous and fetal umbilical venous or arterial samples were obtained during cordocentesis. In addition, eight neonatal umbilical vein samples were obtained immediately after delivery. Samples were assessed for hematocrit and pH, and concentrations of endothelin were measured by sensitive enzyme immunoassay. RESULTS: No significant correlation was found between either fetal or maternal endothelin levels and gestational age ( r = 0.01, p = 0.91 and r = 0.07, p = 0.5, respectively). Fetal plasma endothelin concentrations were significantly lower than neonatal umbilical vein endothelin levels [median 2.5 pg/ml (range 0.9 to 5.73) vs 15.77 pg/ml (8.12 to 19.58), respectively; p < 0.0001] but significantly higher than maternal levels [1.3 pg/ml (0.8 to 3.25): p < 0.0001]. In addition, endothelin values were higher in the umbilical artery than in the umbilical vein, but this difference failed to achieve statistical significance [2.89 pg/ml (1.61 to 5.73) vs 2.29 pg/ml (0.9 to 5.70), respectively; p = 0.06]. No correlation was noted between fetal and maternal endothelin levels ( r = 0.12, p = 0.36). CONCLUSION: Fetal endothelin levels were significantly higher than maternal levels, but neither correlated with gestational age across the second half of pregnancy.

Does amniotic fluid analysis reflect acid-base balance in fetal blood?

The purpose of the study was to examine whether the acid-base balance in amniotic fluid reflects the acid-base state in fetal blood. The pH, PCO2, PO2, bicarbonate, and base excess concentrations were measured in umbilical venous, umbilical arterial, and maternal venous blood and in amniotic fluid samples obtained at fetoscopy. This was performed before intraamniotic termination of 16 normal pregnancies (mean gestation 19.4 weeks), as well as in 14 red blood cell isoimmunized pregnancies (mean gestation 28.4 weeks) undergoing fetoscopy for the diagnosis and treatment of fetal anemia. In normal pregnancies, amniotic fluid pH and bicarbonate were significantly lower than umbilical venous and umbilical arterial blood concentrations, and this was due to the high concentration of base deficit in amniotic fluid. Whereas amniotic fluid PCO2 did correlate significantly with fetal umbilical venous PCO2 values, there was no correlation between other acid-base characteristics. Simultaneous sampling of human fetal umbilical blood and amniotic fluid under the acute conditions of this study did not show significant correlations in acid-base values.

Normal values for human umbilical venous and amniotic fluid pressures and their alteration by fetal disease

Umbilical venous and amniotic fluid pressures were measured in 68 human pregnancies at the time that cordocentesis was performed. Normal umbilical venous pressure was unrelated to gestational age and remained within a tight range (5.3 ± 2.3 mm Hg, mean ± SD). Fetuses with an elevated umbilical venous pressure had disorders consistent with either hepatomegaly or congestive heart failure. Umbilical venous pressure was significantly increased before treatment in two fetuses with immune hydrops; it rapidly declined with treatment. Neither gestational age nor umbilical venous pressure was significantly different in the groups that received and did not receive pancuronium. There was a strong relationship between amniotic fluid pressure and gestational age in normal pregnancy (r = 0.54, p < 0.0001). Women with hydramnios had amniotc fluid pressures greater than control subjects (p = 0.0007). This investigation documents normal human amniotic fluid and fetal umbilical venous pressures. These measurements are altered by disease and may prove to be of diagnostic and therapeutic value in the future.

Reevaluation of Nonstress Test by Umbilical Venous Blood Profile Using Cordocentesis

Fetal blood sampling by cordocentesis was performed in 85 cases of fetuses with either nonimmune hydrops fetalis, anomalies, intrauterine growth retardation, maternal immunological disorders, Rh incompatibility, hydronephrosis, polyhydramnios, maternal preeclampsia or fetal tumor. Fetal heart rate monitoring was also recorded before cordocentesis. We evaluated the usefulness of the nonstress test (NST) with regard to fetal hematologic gas profiles including pH, pO2 and pCO2. When the acceleration was classified into reactive and nonreactive group, pH and pO2 were significantly higher in the reactive group than in the nonreactive group. pCO2 was significantly lower in the former than the latter. However, the sensitivity and specificity of the reactive NST predicting fetal umbilical venous pO2 over 20 mm Hg was 79.7 and 68.7%, respectively. The false-positive rate of nonreactive NST predicting hypoxemia below 20 mm Hg pO2 was 44%. As a consequence, we cannot always rely on the NST, and should perform fetal blood sampling to assess fetal condition for further management.

Umbilical cord acid base changes associated with perinatal cardiac failure

Two infants delivered by emergency cesarean section because of fetal distress are described, and the umbilical blood acid-base findings are discussed. One fetus was stillborn, the other died in the immediate neonatal period, and both showed signs of cardiac dilation and failure on postmortem examination. Umbilical cord blood gas determination at the time of delivery showed almost normal values of pH, Pco2. and Po2 in the umbilical vein but acidotic pH with high Pco2 and low Po2 values in the umbilical artery samples. These findings are probably the result of a prolonged umbilical blood circulation time because of fetal cardiac failure. This sluggish perfusion allows the equilibration of fetal blood with maternal intervillous blood, and the findings in the fetal umbilical vein approximate maternal uterine venous values. Umbilical cord acid-base determinations in perinatal surveillance are commonly recommended without specific details. Umbilical artery samples must be obtained to properly assess the metabolic status of the fetus at the time of birth.

UPPER/LOWER BODY GLUCOSE CONCENTRATION DIFFERENCES WITH ADVANCING GESTATION

Glucose levels in arterial blood reaching the fetal upper body are greater than in blood supplying the lower body(J Devlop Physiol 6:431, 1984). Since fetal body proportions change towards term, we evaluated whether distribution of glucose within the fetus changes. 13 sheep were prepared at 103-128 days, with maternal arterial(MA), and fetal carotid(CA), femoral arterial(FA)and umbilical venous(UV)catheters. Studies were done at 110 to 142 days on healthy fetuses(FA>pH 7.301, ≥3 days postop and ≥ 2 days before delivery. Whole blood, simultaneously drawn from all vessels, was analyzed for glucose and O2 content. Glucose was 35% lower in older animals, due to lower MA levels(58.5 ±1.8mg/dl at 110-119 days vs 53.4±0.8 at>130, p FA in all studies. While the absolute CA-FA fell, the % difference between vessels was stable af∼10%. In contrast, there was no change in fetal O2 content in any vessel nor in the CA-FA O2 difference;CA O2 was 6.23±0.32ml/dl(n=12)at 110-119 vs 5.77 0.50 at> 130 days and CA-FA for O2 was 0.90±0.76ml/dl(n=12)at 110-119 vs 1.16±0.62 at 130. We conclude:the proportional distribution of glucose is stable over the third trimester, but changes in UV glucose will alter the absolute CA-FA difference.

Antenatal measurement of fetal umbilical venous flow by pulsed Doppler and B-mode ultrasonography.

In this study, 163 normal fetuses of between 25 and 41 weeks' gestational age were examined sonographically using B-mode and Doppler equipment to measure umbilical vein diameter, umbilical venous flow amount (UVFA) and velocity (UVFV), and abdominal area (AA). A total number of 230 examinations were performed. The relationships between gestational age and umbilical vein diameter, UVFA, UVFV, and the UVFA/AA ratio were analyzed. Throughout pregnancy, the umbilical venous blood flow velocity remained relatively constant, whereas the umbilical venous blood flow amount increased steadily with gestational age and was proportional to abdominal area.

Placental Transfer of Ranitidine During Steady-State Infusions of Maternal and Fetal Sheep

The placental transfer of ranitidine was studied at pharmacokinetic steady state in anesthetized, full-term, pregnant sheep. Ranitidine was administered to the ewe in three preparations and to the fetus in three other sheep. In all experiments, dose size was based on the combined maternal-fetal weight. Steady-state plasma levels were reached within 4hr by using an initial intravenous bolus dose followed by continuous infusion. Following maternal dosage, the mean maternal (jugular vein) steady-state concentration (CMss) at 4hr was 842 ± 66 ng/ml (SEM) the mean fetal (carotid artery) steady-state concentration (CFss ) was 26.5 ± 4.2 ng/ml, and the mean fetal umbilical venous steady-state concentration was 28.9 ± 3.5 ng/ml. Both the fetal and umbilical plasma concentrations were significantly less than the maternal plasma concentration (p <0.01). With fetal dosage, mean CMss was 414 ± 42 ng/ml at 4hr and was significantly less than the mean CFss value at the same time, which was 6890 ± 360 ng/ml (p <0.005). Ranitidine was not bound extensively to plasma proteins in the ewe or the fetus (range 12-55% bound). The reversal of the CMss∕CFss gradient with the change from maternal to fetal administration and the low binding of the drug shows that the gradient following maternal dosage cannot be explained by ion-trapping or differential plasma protein binding. As active placental transport is considered unlikely, the low fetal plasma concentrations are probably due to the presence of significant fetal elimination of ranitidine. Furthermore, the substantial gradient between maternal and umbilical venous plasma concentrations suggests that placental elimination of ranitidine should also be considered.

Fetal umbilical venous flow measured in utero by pulsed Doppler and B-mode ultrasound: I. Normal pregnancies

Umbilical venous blood flow was measured with a pulsed Doppler unit, which was used in combination with a B-mode ultrasonic imaging system to permit location of the umbilical vein and measurement of its cross-sectional area. The accuracy and limitations of the method are discussed. Forty-seven normal fetuses with gestational ages ranging from 22 weeks to term were studied on a total of 61 occasions. Flow increased with gestational age until 36 weeks, was maximal between 37 and 38 weeks, then decreased during the last 2 weeks of pregnancy. Flow per unit of fetal weight was constant during pregnancy until 36 to 37 weeks, when a reduction occurred.

Acetate as a metabolic substrate in the fetal lamb.

Fetal acetate metabolsim was studied in chronically catheterized fetal lambs of 110-141 days' gestation. Acetate concentration was measured enzymatically in whole blood drawn simultaneously from maternal and fetal pre- and postplacental vessels. The oxygen content of the fetal blood samples was also measured. Fetal umbilical venous acetate concentration was found to be proportional to the maternal arterial acetate concentration and had a mean value of 0.366 mM. Fetal blood acetate increased significantly, by a mean of 0.081 mM, during circulation through the placenta. This increase was proportional to both the maternal acetate concentration and the concentration gradient of acetate across the placenta. The mean maternal arterial acetate concentration was 1.153 mM. Maternal blood lost significant amounts of acetate, 0.112 mM, during circulation through the uterus and appeared to be the source of the acetate being gained by the fetus. It is estimated that a total of 23 mmol of acetate/kg of fetal weight is being taken up by the fetus each day, providing it with 0.560 g of carbon/kg. Comparisons of acetate uptake with fetal oxygen uptake indicate 10% of the daily fetal oxygen consumption would be required to completely oxidize the acetate being gained by the fetus.

A simplified method for estimation of estriol in pregnancy plasma

A fluorometric method for determination of estriol in pregnancy plasma has been established. The procedure includes hydrolysis in a boiling water bath, use of unconjugated radioactive estriol to determine methodologic losses, solvent extractions, and the Ittrich-Kober reaction with the use of tetrachloroethane for extraction of the Kober chromogens. The method is sensitive, reproducible, and rapid. A number of drugs routinely used in obstetric care caused no interference. Serial determinations in 20 patients have been performed, in addition to over 300 isolated determinations. The values ranged from 10 to 58 μg per 100 ml. of plasma between the thirty-seventh and fortieth weeks of uncomplicated pregnancies. Fetal umbilical venous and arterial values were comparable but were severalfold higher than maternal levels. The method has been applied to amniotic fluid, and the results were contrasted with levels in plasma.