Transient Fetal Bradycardia Research Articles

Cord involvement bradycardia

SummaryA relationship has been established between the occurrence of transient fetal bradycardia at the height of a uterine contraction, with a sudden dip of at least 40 beats per minute and rapid return, and cord entanglement round the baby. In 28 cases with ‘cord involvement bradycardia’ fetal cardiotocographs, 17 of the babies were found to have cord entanglement at birth.This type of episode of bradycardia was not consistently associated with meconium staining of amniotic fluid, the use of oxytocic drugs or low Apgar scores for the babies. Some of the patients with cord involvement bradycardia proceeded to develop ‘variable decelerations’

Relationship of fetal bradycardia to maternal administration of lidocaine in sheep

The casual relationship between the use of lidocaine and fetal bradycardia and the effect of the drug on maternal and fetal hemodynamics were studied on 13 chronically instrumented pregnant sheep. Lidocaine was infused intravenously to the mother for 60 minutes during arterial lidocaine concentrations were maintained at 2 to 5 microgram per milliliter in the mother and at less than 2 microgram per milliliter in the fetus. A decrease in uterine blood flow and an increase in uterine vascular resistance and uterine activity occurred immediately following the administration of lidocaine to the ewe. These changes were followed by a transient fetal bradycardia in 12 out of 17 experiments, accompanied by a decrease in fetal PaO2 values. These phenomena were seen in the absence of such predisposing conditions as maternal hypotension and fetal acidosis. It would appear that the mechanism responsible for a transient fetal bradycardia following regional obstetric anesthesia, particularly paracervical block anesthesia, in the initially nonasphyxiated fetus may in part be related to a brief decrease in perfusion of intervillous spaces. The bradycardia can occur at low lidocaine concentrations in both the maternal and fetal blood in a range similar to that observed in clinical practice.

Oral prostaglandin E2 for labor induction in high-risk pregnancy

Oral prostaglandin E2 (PGE2) was used alone or synergistically with intravenous oxytocin to induce labor in 84 women whose pregnancies were at high risk. A control group of 84 similar high-risk pregnancies where labor was induced with intravenous oxytocin alone was studied to compare the safety and efficacy of the two regimens. Oral PGE2 administration, combined with the synergistic effect of intravenous oxytocin, is safe for induction of labor in gravid women whose fetuses are at risk. Uterine polysystole, which is potentially dangerous, especially to the high-risk fetus, was not commonly encountered and only once was associated with transient fetal bradycardia. Uterine hypertonus was not encountered with PGE2; however, it did occur with oxytocin stimulation. Nausea and vomiting occurred in one third of the women treated with PGE2 but were well tolerated and required discontinuation of the drug in only one instance. There was no apparent advantage of using the combination PGE2 regimen in patients whose cervices were more favorable for induction of labor (Bishop score, 5 to 9). However, oral PGE2, used either alone or synergistically with oxytocin, appears twice as effective in inducing labor than was oxytocin alone in women in whom labor was considered to be “difficult to induce” (Bishop score, 0 to 4).

External cephalic version under tocolysis.

We currently consider the external version of the fetus from a breech to a vertex presentation near term the best solution to the disadvantages of a breech delivery for mother and child. Version at such a late time in gestation is only possible with the aid of the tocolytic relaxation of the uterus as recommended by us. This method offers two important advantages over the conventional method of external version, the performance of which after the 34th week of gestation has been discouraged because of the poor chance for success: 1. Because of the relatively decreased intrauterine space during the last month of pregnancy the fetus will revert less readily to a breech. 2. In the event of a complication during external version the immediate operative delivery of the mature infant near term is possible. After the presentation of the fetus has been diagnosed by ultrasound the mother is given 20-50 micrograms Fenoterol (Partusisten) intravenously simultaneously with an inhalation analgesia. The version itself is effected by positioning the hands of the operator against the fetal forehead and by turning the infant as in a backwards roll. If this fails, the dose of the tocolytic agent may be increased. In cases with extended legs the chances for success appear to be decreased. The completed version should be confirmed with an ultrasound examination and the undisturbed status of the fetus should be documented with a cardiotocogram immediately after the version. The following results were achieved: The external version was successful in 43 of 57 pregnant women (75%). If the material is selected more critically, over 80% of the attempted versions should be successful. We have now delivered 40 infants as vertex presentations after a previously diagnosed breech presentation. The frequency of breech deliveries in our hospital has decreased by 2.6% from 5.4% to 2.9% since the introduction of version. The decrease is statistically significant. Convincing evidence that version has decreased fetal risk from breech delivery is found in a comparison of the newborn status. The decrease in the percentages of clinically depressed and acidotic newborns is also statistically significant. The failure rate does not appear to increase with increasing gestational age. There is no correlation between parity and failure or between maternal age and failure. So far we have seen no serious complications. In 5 of 24 cardiotocograms recorded a transient fetal bradycardia occurred immediately after the version which disappeared after a few minutes of maternal lateral position.

Fetal bradycardia after paracervical block.

Three aspects of PCB were studied: a) technic, b) functional signs of nerve block and the earliest signs of toxicity, c) measurements of the anesthetic agent in maternal and fetal blood. Inadvertent infiltration of the myometrium was a frequent cause of transient fetal bradycardia, which was associated with decreased uterine contractility, an action similar to that of adrenalin. Functionally, the decrease in uterine contractility, with or without initial hypertonicity, was associated with a transient decrease in placental blood volume, a slight change in fetal blood pH and transient deceleration of fetal heart rate (FHR). The earliest sign of potential fetal toxicity to PCB is the change in uterine contractility with or without FHR alteration. Measurements of the anesthetic agent are impractical for clinical purposes. Simple monitoring of contractility and FHR, however, may serve as important indicators of drug action on the myometrium and may prevent serious toxicity to the fetus during subsequent blocks.