Wayne L. Johnson

Transfer of ampicillin into fetus and amniotic fluid from maternal plasma in late pregnancy

Abstract 1. 1. The transfer of ampicillin, a new semisynthetic penicillin, into fetal serum and amniotic fluid in therapeutic concentrations has been demonstrated. 2. 2. Maternal serum levels of ampicillin disappear relatively rapidly after intravenous infusion of sodium ampicillin and are almost gone within 2 hours. 3. 3. Ampicillin is demonstrable in fetal serum 30 minutes after maternal infusion, reaching equilibration with maternal serum in 1 hour. 4. 4. The concentration of ampicillin in amniotic fluid of normal gravidas continues to rise up to 8 hours and then slowly declines over the next 19 hours. 5. 5. A low level of ampicillin appears in amniotic fluid of dead fetuses and reaches maximum concentration at 6 hours, which is approximately one fifth of the maximal concentrations of normal pregnancy with a live fetus. 6. 6. Active participation by the fetus is suggested as a mechanism in establishing higher levels of ampicillin in amniotic fluid of viable pregnancies, probably by fetal urinary excretion. 7. 7. Ampicillin shows promise as a useful drug in the treatment of amnionitis and intrauterine fetal sepsis.

Isolation of Mycoplasma hominis, T-strains, and cytomegalovirus from the cervix of pregnant women

Abstract Mycoplasma hominis was isolated from 37 of 199 cervical cultures from women attending the prenatal clinic at the University Hospital in Seattle. The isolation rate was higher among Negroes (32 per cent), than among Caucasians (16 per cent). T-strains were isolated from 56 per cent of the pregnant Caucasian women and 75 per cent of the pregnant Negro women. Nearly all (92 per cent) of those who carried M. hominis also carried T-strains. No adverse effect of pregnancy or on the infant from the presence of either M. hominis or T-strains was observed. Both organisms were transmitted to infants of positive mothers (M. hominis to 2 of 11 such infants and T-strains to 4 of 15 such infants). Cytomegalovirus (CMV) was isolated from cervical cultures of 5 of 140 pregnant women. Congenital cytomegalovirus disease or transmission to the infant was not seen in any of these 5 patients. On the other hand, the presence of CMV in the cervix was associated with lower than average birth weight.

Transplacental passage of methicillin and dicloxacillin into the fetus and amniotic fluid

Abstract The transfer of methicillin and dicloxacillin from maternal blood to fetal blood and amniotic fluid was studied in 105 patients. Significant levels of methicillin were detected in fetal serum within 30 minutes after discontinuing the maternal infusion, with equilibration between maternal and fetal serum levels within one hour. Dicloxacillin is associated with lower levels of antibiotic activity in the fetal serum and insignificant levels in the amniotic fluid. Equilibration between maternal and fetal levels did not occur. Protein binding of antibiotics results in a reduced rate of transfer from the maternal to the fetal compartment.

Stress relaxation in human uterine muscle

Abstract The passive stress relaxation behavior of human uterine muscle was investigated. Specimens were stretched at four elongation rates to a nominal peak tension of 5 Gm. per square millimeter and allowed to relax. The stress relaxation behavior was described by the parameters,S d /S o and time, where S d was the decay in stress after a certain period of relaxation, t, and S o was the initial peak stress which occurred at the time elongation was stopped or at t=0. The stress relaxation behavior, described by curves ofS d /S o versus time (time plotted on a log scale), exhibited four characteristic stages. The position of theS d /S o versus time curve was proportional to approximately13/R, where R was the elongation rate in millimeters per minute. Also investigated were the effects of glycerination, temperature changes, site of the specimen in the uterus, aging, pregnancy, trypsin, and pronase on the stress relaxation behavior. From these experiments it was concluded that stress relaxation is the result of a physical process in the tissue and the mechanism responsible was located primarily in the connective tissue framework. Aging did not cause a significant change in the normal stress relaxation behavior. Pregnancy slowed down the rate of stress relaxation about 5 per cent. This type of mechanical, passive characteristic of uterine muscle was discussed in relationship to its functional importance in pregnancy.

Effect of pudendal, spinal, and peridural block anesthesia on the second stage of labor☆

Abstract The second stage of labor was studied in 42 patients before and after conduction anesthesia. Intrauterine pressure and superimposed voluntary effort were measured and compared before and after induction of anesthesia. Voluntary effort increased progressively during the second stage in patients receiving pudendal block. Patients having peridural block showed a slight drop in voluntary effort. Patients with spinal block had a mean reduction in voluntary effort after the block. Patients receiving peridural block showed a mean decrease in uterine contraction intensity, but no change was seen in contraction intensity after pudendal or spinal block. Record review of 3,265 primigravid term patients revealed an increased length of the second stage and an increased incidence of forceps deliveries in patients with spinal and peridural anesthesia when compared with pudendal anesthesia.

Effects of intra-amniotic injection of hypertonic saline on uterine activity, blood and amniotic fluid volumes, and electrolyte concentrations

Abstract Intraovular injection of hypertonic saline successfully initiated labor in 16 patients. There was a net increase in amniotic fluid volume associated with a decreased blood volume within 2 to 4 hours following injection. The sodium chloride in the amniotic sac is diluted by the influx of water and is lost into the maternal circulation where increased serum sodium and chloride concentrations were observed. Amniotic fluid pressures were continuously monitored. Uterine activity increases shortly after injection and continues to increase until delivery is accomplished.

Passive stretch relationships in human uterine muscle

Abstract The passive length-tension relationship was studied using human myometrium. The strips of muscle were extended by step pulls of 3 mm. per extension and the tension recorded after the first or rapid stage of stress relaxation had occurred. The cross-sectional area was measured at the narrowest point of the muscle and tension was computed as grams per square millimeter. The material from pregnant patients gave curves which were flatter and rose less steeply than those from the nonpregnant. The alteration in the passive length-tension properties due to the pregnant state was also found to be present when 20 mm. strips were compared to 30 mm. strips from nonpregnant patients. This comparison was necessary due to what appeared to be elastic recoil in the excised muscle from pregnant patients. The passive length-tension relationship in the nonpregnant patient material was not altered by age, previous parity, or phase of the menstrual cycle. There were no differences noted in strips taken from various sites in the pregnant uterus. Histologic counts of the relative amounts of muscular and nonmuscular tissue between the pregnant and nonpregnant material could not account for the differences in the passive length-tension curves. The relative amounts of muscle and connective tissue were the same in all categories.

Comparison of spontaneous, oxytocin-stimulated, and hypertonic saline-induced labor by different methods of record analysis

Abstract Intrauterine pressure recordings were made during the active phase of labor in 64 patients. On-line electronic integration of the area under the pressure curve was used as a measure of uterine activity. A total of 204 hours of labor including 4,224 individual contractions were analyzed by (1) average pressure (integrator method), (2) Montevideo units, (3) Alexandria units, and (4) frequency distribution. Comparisons were made between spontaneous labor, oxytocin-stimulated labor, and hypertonic saline-induced labor. Oxytocin-stimulated labor and hypertonic saline-induced labor show increases in amplitude and frequency of contractions when compared with spontaneous labor. Concomitant increases in total uterine activity were noted by all methods of measurement. In this series, both hypertonic saline-induced and oxytocin-stimulated labor are different from spontaneous labor whether measured in Montevideo units, Alexandria units, or average pressure. Electronic integration of the pressure signal is recommended as a method of measuring uterine activity in physical units (mm. Hg).

Observations of placental blood flow with a Doppler flowmeter

The Doppler flowmeter is a sensitive indicator of fetal life in early pregnancy. Characteristic placental sounds can also be detected with this instrument as a rushing wind or whirlwind sound. A series of 111 patients had placental localization by manual exploration at delivery compared to placental sounds in late pregnancy detected with the Doppler flowmeter. Placental localization using this instrument is currently limited, as only about 20 per cent of the placentas were heard; nearly all of these were located on the anterior uterine wall. The placental sound is fetal in origin as it is continuous through uterine contraction, is associated with a fetal arterial sound, and is interrupted by umbilical cord clamping.

The effect of pregnancy and norethynodrel with mestranol (Enovid) on length-tension relationship in the rabbit aorta☆

Abstract Length-tension responses of the rabbit aorta were tested by constantly stretching spiral aortic strips, and continuously recording the tension produced. No differences were found between control nonpregnant animals, pregnant animals, and animals treated with Enovid.