Clinical significance of fetal heart rate patterns during labor

The effect of maternal magnesium sulfate treatment on fetal heart rate variability (FHRV) was evaluated by comparing the maternal serum magnesium level drawn during labor to the degree of FHRV seen concurrently on fetal rate heart monitor strips. The records of 57 patients treated with intravenous magnesium sulfate for hypertensive disorders of pregnancy were studied. Fetal heart rate variability was measured by both subjective assessment and objective measurement. The difference in beats/min between the average high and low fetal heart rates, at the time the magnesium level obtained, was used as the objective measurement. Labor records were reviewed and neonatal outcome recorded. Data from individual patients not treated with analgesics were analyzed separately in addition. Statistical methods used included analysis of variance, Student's t-test, and Chi square analysis. The range of magnesium levels was 2.3-7.4 mEq/L. Thirty-four women had single determinations of magnesium levels and 23 had multiple determinations. Statistical analysis showed no significant change in FHRV with increasing maternal magnesium levels. In addition, no significant effect of maternal magnesium level on FHRV was noted in the group that did not receive meperidine, morphine, or epidural anesthesia. Neonatal outcome, assessed by Apgar scores, did not vary with maternal magnesium level. We conclude that maternal magnesium sulfate treatment, in the therapeutic ranges normally obtained, does not significantly affect fetal heart rate variability.The effects of maternal magnesium sulfate on fetuses and neonates are reported to range from severe neurologic depression, including death, 1 -2 to virtually no effects at all 3 -6 to actual benefits in primate fetuses. 7 Previous reports have analyzed the effect of maternal magnesium sulfate treatment on fetal heart rate variability (FHRV) without reporting magnesium levels. We evaluated the effect of maternal magnesium sulfate treatment on FHRV by comparing the concurrent FHRV recorded on fetal monitoring records wil ‡i maternal serum magnesium levels. The fact that FHRV is probably one of the best methods available for evaluating fetal wellbeing stresses the importance of studies of the effects of commonly used prepartum medications on heart rate variability. MATERIALS AND METHODSSelected patients admitted to the labor and delivery unit of the University of Arizona Health Sciences Center from 1981 to 1983 who received magnesium sulfate therapy for hypertensive disorders of pregnancy were studied. Upon admission, patients underwent either external fetal monitoring or internal fetal monitoring for fetal heart rate in beats per minute and uterine contractions (mm Hg) until the time of transfer to either the delivery room or the operating room. Labor flow sheets were reviewed that correlated the clinical course of each patient with the fetal heart rate monitor. The times of medication, phlebotomy for magnesium levels, examinations, change of positions, and unusual monitor re-

Section: Discussionsupporting

confidence: 91%

Effect of Maternal Magnesium Sulfate Treatment on Fetal Heart Rate Variability

Canez¹,

Reed²,

Shenker³

1987

“…Both deaths reported by Sibai et al 5 had anemia and hydrops and the amplitude of the sine waves was 40 bpw in both cases. The deaths reported by Cibils 8 and Basket and Koh 9 were both associated with sine waves of increased amplitude (40 to 50 bpm). The case reported by Cruikshank 10 did not fit the strict definition of SHR in that variability was present.…”

Section: Discussionmentioning

confidence: 91%

Sinusoidal Fetal Heart Rate Pattern During Labor

Egley¹,

Bowes²,

Wagner³

1991

Of 1280 consecutive fetuses monitored internally with a scalp electrode for at least 10 minutes during labor, 54 (4.2%) demonstrated the sinusoidal heart rate (SHR) pattern. Seven of these demonstrated the SHR pattern for more than 90 minutes. In six of these seven cases, the SHR pattern occurred during oxytocin administration. The SHR group did not differ from the 1226 fetuses not demonstrating the SHR pattern (NSHR group) in Apgar scores, incidence of other fetal heart rate abnormalities, or passage of meconium. The scalp pH was obtained from three fetuses in the SHR group and was above 7.30 in each. Alphaprodine administration during labor was associated with development of the SHR pattern, whereas other narcotic administration was not. The significance of "atypical" SHR pattern with increased amplitude is discussed, along with the need to adhere to strict definition of the SHR pattern.

“…Interestingly, an association between lidocaine-induced bradycardia and postmaturity has been noted. 3 Neonatal sinus bradycardia is not uncommon in term or postmature infants. Further heart rate depression in the presence of distress, however, could be more significant in these infants.…”

Section: Discussionmentioning

confidence: 99%

“…There have been many reports of lidocaine-associated fetal bradycardia, apnea, and seizures, especially after maternal paracervical block (PBC) anesthesia. 1 " 3 Since PCB anesthesia has become less popular, reports of lidocaine toxicity have decreased. We recently, however, treated an infant who manifested symptoms of lidocaine toxicity after maternal pudendal anesthesia.…”

mentioning

confidence: 99%

Lidocaine Toxicity After Maternal Pudendal Anesthesia in a Term Infant with Fetal Distress

Bozynski

Rubarth²,

Patel

1987

There have been many reports of lidocaine toxicity especially after maternal paracervical block anesthesia. We recently treated a term infant with evidence of fetal distress who presented with symptoms of lidocaine toxicity after maternal pudendal anesthesia. The infant developed apnea and bradycardia soon after birth which responded to mechanical ventilation and epinephrine. A prolonged Q-T interval was noted on day 1 which normalized by day 3. Cord blood was assayed and revealed an elevated lidocaine level. Lidocaine toxicity has been associated with fetal distress secondary to fetal ion trapping in the presence of acidosis. Although good response to supportive therapy occurred in our patient, other methods of therapy such as exchange transfusion and treatment of seizures may be required in some cases. Awareness of this now uncommon syndrome will lead to prompt diagnosis, appropriate work-up, and management.