Fetal systolic time intervals after paracervical block during labor.
Fetal systolic  time intervals (FSTI) were recorded every 10th second (s) during uterine contractions in 25 paturients in the first stage of labor before and after paracervical block (PCB). Twentytwo patients had good or excellent relief of pain. The newborn infants were not depressed. After PCB the duration of the R--R and S1--S2 intervals increased. A close correlation was found between the R--R and S1--S2 intervals, both before and after PCB, and during early decelerations recorded before and after PCB. The S1--S2 The S1--S2 interval was prolonged after PCB, even after correction for the heart rate. The R--S1 interval and the amplitude of the first part of the first heart sound (S1a) also increased after PCB. The FSTI showed a conspicuous cyclic variation during uterine contraction. The S1a amplitude decreased after the peak of contraction, the others increased simultaneously. The results contradict the assertion that PCB causes fetal hypoxia or reduction of the maternal placental circulation. A centralization of the fetal circulation, possibly combined with a direct effect of local anesthetic on the fetal heart, would explain the changes found after PCB. The cyclic variation of the parameters during uterine contraction is probably caused by a transfer of blood between the placenta and fetus. The changes of myometrial dynamics after PCB, as shown by the alteration of the phases of the amniotic pressure curve, are compatible with this transfer of blood.
D000293:Adolescent; D000328:Adult; D000653:Amniotic Fluid; D000772:Anesthesia, Local; D000773:Anesthesia, Obstetrical; D002045:Bupivacaine / Q000494:pharmacology*; D005260:Female; D005318:Fetal Heart / Q000187:drug effects*; D005323:Fetal Monitoring; D006801:Humans; D007743:Labor, Obstetric; D011247:Pregnancy; D011312:Pressure; D013599:Systole / Q000187:drug effects; D013997:Time Factors; D014590:Uterine Contraction / Q000187:drug effects
D002045:Bupivacaine