Umbilical artery flow velocity waveforms during acute hypoxemia and the relationship with hemodynamic changes in the fetal lamb

Article Abstract:

Growth-retarded fetuses are thought to result from inadequate flow of blood through the placenta, the organ of fetal nutrition. The oxygen supply to the fetus is compromised, producing small fetuses. The small arteries of the placenta can be studied to determine the velocity of the flow of blood through specific arteries. Doppler ultrasonography, the use of high frequency sound to visualize internal structures, was used to determine the waveforms created by the flow of blood through the umbilical cord arteries, the pulsality index. A diminished supply of oxygen to the fetus, fetal hypoxia, was artificially induced in sheep by interrupting the blood supply of a major artery in the mother. This simulated a deceleration of the fetal heart rate and caused a condition of fetal hypoxia. It was found that the resistance of the blood vessels in the placenta, placental vascular resistance, was not altered after fetal hypoxia. The noted increased pulsality index was instead the result of changes in the fetal heart rate.

Usage, Ultrasound imaging, Maternal-fetal exchange, Company sales and earnings, Fetal anoxia

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The T/QRS ratio of the electrocardiogram does not reliably reflect well-being in fetal lambs

Article Abstract:

Changes in the electrocardiogram (ECG) wave tracing fail to correlate with severe oxygen lack in the lamb fetus. This suggests that adding ECG analysis to electronic fetal monitoring will not improve diagnostic capability. Two medications with potential protective effects proved ineffective. Surgery was performed on 47 pregnant ewes to install sensors and catheters in the ewe and the fetus. After recovery from surgery, oxygen lack was induced in the fetus by gradually blocking uterine blood flow. Oxygen levels were reduced to about one-third of normal and maintained at that level for one hour. Sixteen animals were pretreated with R-75231 and 12 animals with flunarizine, both drugs with the potential of minimizing asphyxial injury. Half the animals died. EEG analysis showed that normal variation among animals was greater than the effect of oxygen lack nor did changes within a single animal correlate with severity of effect on fetal metabolism or on survival. The drugs showed no positive effects.

Analysis, Electrocardiogram, Electrocardiography, Fetal monitoring

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Absence of neuronal damage after umbilical cord occlusion of 10, 15, and 20 minutes in midgestation fetal sheep

Article Abstract:

Fetal sheep may experience lack of oxygen but not nervous system damage after the umbilical cord is experimentally shut off. Researchers occluded the umbilical cords of fetal sheep in mid-pregnancy for 10, 15, or 20 minutes. Evaluation of the fetuses three days after experimental occlusion showed no damage to neurons or brain. Occlusion did cause low blood pressure, slow heartbeat, pH imbalance, lack of oxygen, and high levels of carbon dioxide. None of the fetuses died. The results may not apply to human fetuses as the human brain is much larger than the sheep's.

Physiological aspects, Asphyxia neonatorum, Nervous system diseases

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