Association of umbilical venous with inferior vena cava blood flow velocities

Article Abstract:

Abnormalities in blood flow from the placenta through the umbilical arteries can indicate problems with the fetus, especially growth retardation. A previous study of fetuses with abnormal umbilical arterial blood flow velocities and growth retardation also found abnormal velocities in a blood vessel known as the inferior vena cava, which drains blood returning from the lower part of the body into the fetal heart. This abnormality was also seen in fetuses with abnormally fast or slow heart rates. It is thought that abnormal inferior vena cava blood flow velocities are indicative of heart problems in the fetus. Blood flow velocities through the umbilical vein, which returns blood from the fetus to the placenta, vary with fetal breathing patterns. This study examined if there was a relationship between umbilical venous and inferior vena cava blood flow velocities and whether abnormalities in one vessel would indicate abnormalities in the other. Ultrasound studies were performed on 74 fetuses, 15 that were normal and 59 that were abnormal, including those that had an abnormal heart rate (27 fetuses) or that had no blood flow velocity through the umbilical artery measurable at the end of diastole, the resting phase of the heartbeat (21 fetuses). Umbilical venous velocities did not vary with heart rate in any of the normal fetuses, but were lower in 11 of the 21 fetuses with no end-diastolic velocities. These variations in velocities, or venous pulsations, were also seen in fetuses with abnormal heart rates. In fetuses with these pulsations, abnormalities in inferior vena cava blood flow velocities were also found. Reversed blood flow averaged 27.5 percent in the fetuses with pulsations and 7.5 percent in the fetuses without the pulsations. These results reveal that abnormal umbilical venous blood flow velocities associated with the fetal heart beat are related to abnormal inferior vena cava blood flow velocities, which may indicate abnormalities of the fetal heart. (Consumer Summary produced by Reliance Medical Information, Inc.)

Abnormalities, Physiological aspects, Fetal blood, Umbilical cord, Prenatal ultrasonography, Vena cava, Venae cavae, Ultrasonics in obstetrics

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Maternal and fetal catecholamines and uterine incision-to-delivery interval during elective cesarean

Article Abstract:

Women undergoing elective (planned) cesarean sections receive anesthesia via spinal (injected into the canal in which the spinal cord lies) or epidural routes (anesthesia injected just outside the dura mater, the thick membrane that surrounds the spinal cord). When an interval longer than three minutes occurs between the uterine incision and the delivery of the infant, Apgar scores (an indication of physical status taken immediately after birth and again five minutes later) are lower and the acidity of the infant's body fluids increases (a decrease in pH). The fetus responds to intrauterine stress by producing higher levels of catecholamines, substances with several kinds of biological action, including vasoconstriction (blood vessel constriction) and increased heart rate. To determine whether fetal catecholamine levels are correlated with the length of the incision-to-delivery interval under spinal and epidural anesthesia, 54 women were studied (28 with spinal anesthesia). Results showed that infants delivered after longer uterine incision-to-delivery intervals had lower pH values in the blood in their umbilical arteries and higher levels of norepinephrine, regardless of the type of anesthesia used. When spinal anesthesia was used, higher doses of the anesthetic agent were associated with higher epinephrine levels in the infant's umbilical artery. Such a correlation was not found for those who received epidural anesthesia. It is likely that longer uterine incision-to-delivery intervals lead to fetal distress as a result of disruption of the uteroplacental blood flow. This, in turn, activates the fetal sympathetic system, resulting in increased output of catecholamines. In general, regardless of the type of anesthesia used, a short interval is most desirable, especially for cases associated with impaired blood flow between the uterus and placenta for any other reason. (Consumer Summary produced by Reliance Medical Information, Inc.)

Methods, Catecholamines

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Effect of epidural anesthesia for cesarean delivery on maternal femoral arterial and venous, uteroplacental, and umbilical blood flow velocities and waveforms

Article Abstract:

Epidural anesthesia is administered into the space outside the dura, the fibrous covering of the spinal cord. Its effect on 13 women undergoing elective cesarean section and on their fetuses was assessed. Of specific concern were the effects on uteroplacental (from uterus to placenta) and fetal umbilical (between placenta and fetus) circulation. Doppler and other ultrasound techniques were used to evaluate circulation in these vessels, as well as in the maternal femoral artery and vein, the large vessels of the thigh, during cesarean delivery. Several variables relevant to blood flow were calculated, including peak flow velocity, vessel diameter, blood pressure and related variables. Results indicated that maternal heart rate increased after anesthesia, with no change in systolic blood pressure (pressure during the active phase of the heart's contraction) and a slight drop in diastolic pressure (measured during the passive phase). Resistance to flow of blood in the uteroplacental circulation increased after anesthesia, as did indices of pulsatility (another measure of adequate circulation). Such findings are consistent with impaired circulation in these vessels, although systolic blood pressure remained constant. Measurements from the umbilical artery circulation indicated no changes. Changes noted in the maternal vessels suggested that sympathetic tone (a measure of activity of the sympathetic nervous system, which causes constriction of vessels) had decreased in smaller vessels. The diameters of the femoral artery and vein did not change, however. The results indicate that blood flow to the leg of the women undergoing cesarean section increases after anesthesia and that some impairment of uteroplacental circulation occurs. (Consumer Summary produced by Reliance Medical Information, Inc.)

Femoral artery, Umbilical arteries

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