E.L. Corey

The effects of magnesium therapy on the duration of labor.

Abstract Magnesium is an accepted drug in the management of toxemia of pregnancy, and is employed by many physicians as the anticonvulsant agent of choice in the therapy of this commonly encountered gestational disease. Many modes of administration and variable dosage schedules have been evolved over the past half century, ranging from small quantities given orally to relatively large amounts introduced by the parenteral route. In a recent study conducted at the University of Virginia Hospital, 5 it was suggested that prompt, rapidly attained, and effective magnesium blood levels (7 to 8 mEq. per liter) could best be effected by introducing this agent intravenously. Therefore, during the last 30 months, pre-eclamptic and eclamptic patients admitted to the Obstetric and Gynecologic Service of the University Hospital have received magnesium intravenously in high dosages. Clinical observations carried out in our labor and delivery suites have, however, given the impression that the intravenous administration of magnesium sulfate, in sufficient concentration, results in a prolongation of labor. Inasmuch as the commonly utilized sedative drugs morphine, meperidine, and phenobarbital used in the therapy of toxemia have been seemingly exonerated of a direct uterine depressant activity, 14 and since the only departure from the customary therapeutic regimen during the past 30 months from that employed previously was the elevation of the serum magnesium level, it appeared probable that, if labor were in truth prolonged in these patients, the magnesium ion was depressant to the human myometrium during labor. It was in an attempt to clarify this point that the present study was undertaken.

Effects of anesthetic and sedative agents commonly employed in obstetric practice on isolated human uterine muscle

Abstract 1. 1. An attempt to assay the effects of commonly employed anesthetic and sedative agents on human uterine muscle tissues is described. 2. 2. All of the inhalation anesthetics tested were found to be markedly depressant to gravid and nongravid uterine muscle activity in vitro, with the single exception of trichloroethylene. 3. 3. Morphine, scopolamine, Demerol, atropine, and phenobarbital produced no significant effect on the activity and tonus of uterine muscle samples obtained from both nongravid and gravid uteri. 4. 4. Nembutal was found to be without marked effect on tissues from nongravid uteri, but to possess a depressant action on samples from the gravid uterus when in sufficiently high concentration. 5. 5. Magnesium sulfate depressed contractility and lowered tonus in muscle strips from both nongravid and gravid uteri.

An evaluation of the action of relaxin on isolated human uterine muscle and cervical tissues in vitro

Abstract 1. 1. Relaxin had no demonstrable effect on the spontaneous contractility of isolated human uterine muscle, or on the tension of cervical tissues in vitro. 2. 2. This was true for tissue samples taken from both nongravid and gravid uteri. 3. 3. It appears that the evaluation of relaxin as an adjunct to the armamentarium of the obstetrician and gynecologist must await the result of extensive clinical experience and trial.

Electromyography of the human uterus

Abstract 1. A simple, nontraumatic method for recording bioelectric potentials emanating from the human uterus in situ is described. 2. Potential shifts as recorded from the nongravid organ were predominantly monophasic, the frequency varying with the ovarian cycle. This frequency of potential change was highest just prior to and immediately following menstruation and lowest at a time approximating ovulation. 3. Potential shifts during pregnancy were characteristically and predominantly biphasic. The frequency of such potential changes remained relatively constant throughout gestation, approximating that seen during the ovulatory phase of the menstrual cycle. 4. Records from isolated uterine muscle strips were of such a character as to be interpreted as evidence that tracings secured from the uterus in situ represented true uterine electropotential changes. These records gave indication of the equipotentiality of various portions of the uterus as regards bioelectric activity. 5. Bioelectric activity is present in the human uterus until at least the age of 82 years.