Pulmonary function in preeclamptic women receiving MgSO4.

Pulmonary function was studied in ten preeclamptic women in labor receiving continuous infusions of MgSO4 (group I) and six normotensive, healthy parturients in labor (group II). In group I, the forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and maximum voluntary ventilation (MVV) were measured prior to, two hours after and six hours after the start of infusions. The mean FVC decreased from a baseline value of 3.05 +/- 0.41 to 2.67 +/- 0.50 L (P less than .005) at two hours and to 2.71 +/- 0.42 L (P less than .005) at six hours; the mean FEV1 decreased from a control value of 2.50 +/- 0.41 to 2.25 +/- 0.45 L at two hours (P less than .01) and to 2.25 +/- 0.37 L at six hours (P less than .01). The mean MVV decreased from a baseline value of 93.75 +/- 15.6 to 84.4 +/- 17.1 L at two hours (P less than .01) and 83.75 +/- 13.5 L at six hours (P less than .02). There were no significant differences between the two- and six-hour values. There was no change in the percentage of FEV1: FVC at any time during the measurement. The mean serum magnesium level was 3.66 +/- 0.44 mg/dL. In the control group (group II), the FVC, FEV1 and MVV values were within normal limits, and there were no significant changes from baseline measurements at two and six hours. The results indicate a decrease in pulmonary function in preeclamptic patients in labor receiving MgSO4 infusions.

Hexoprenaline pharmacokinetics in pregnant and nonpregnant sheep.

Hexoprenaline, a beta 2-sympathomimetic agent, is used to suppress uterine contractions in the treatment of premature labor. However, little is known regarding the potential of this drug to undergo placental transfer or whether the pregnant state alters any of the pharmacokinetic parameters. Using sheep as a model, intravenous doses of 14C-hexoprenaline were administered to pregnant and non-pregnant animals. Measurable levels of radioactivity did not appear in fetal blood samples. After intravenous bolus administration, blood concentrations in the ewe could be fitted by a triexponential curve characteristic of a three-compartment pharmacokinetic model. Following intravenous infusion, a biexponential curve described the decline in blood concentrations. Mean terminal half lives for total radioactivity ranged from 2.5 to 4.2 hours. The pregnant animals tended to exhibit smaller apparent volumes of distribution and lower values for total body clearance, normalized to body weight, compared to non-pregnant sheep.

Human perinatal distribution of butorphanol.

The perinatal distribution of butorphanol was demonstrated in relation to maternal-neonatal transfer and colostrum/milk excretion in obstetric patients. Parenteral butorphanol passed the placental barrier and was found in neonatal cord serum. The mean neonatal serum concentration of butorphanol was not different from the mean maternal serum concentration of butorphanol, following a 1 or 2 mg intramuscular dose. Butorphanol was detected in the milk of lactating women following oral and intramuscular administration. Serum and milk concentrations appeared to be parallel with time. This observation was confirmed by the constancy of the mean milk-to-serum concentration ratio (0.7 intramuscular, 1.9 oral). We calculated that 4 micrograms would be the maximum amount of butorphanol, which would be expected to be present in the full daily milk output (1 L) following administration four times a day of 2 mg intramuscular or of 8 mg oral doses. An oral dose of 4 micrograms to an infant weighing 4 kg corresponds to the negligible oral dose of 0.7 mg to a 70 kg adult. The demonstrated safety and efficacy of butorphanol as an obstetric analgesic and the characteristics of the maternal-neonatal transfer and milk excretion are indicative of the potential excellence of this agent for obstetric use.

Placental transfer and other physiologic studies with intravenous butorphanol in the anesthetized pregnant ewe.

In clinical evaluation, butorphanol has been used in labor pain with analgesia and newborn outcome comparable to meperidine. Only limited placental transfer studies have been done in the human. The placental transfer and effect of intravenous butorphanol (2 mg) on avrious cardiovascular parameters were determined in anesthetized sheep. Serum butorphanol was determined by a specific radioimmunoassay. Butorphanol 2 mg intravenously did not affect the measured cardiovascular parameters in either ewe or fetus. Butorphanol could be demonstrated in the fetal circulation within one minute of administration and appeared to reach equilibrium in the maternal circulation rapidly and to remain in equilibrium thereafter. A biexponential decline of butorphanol was observed in the maternal serum with a terminal elimination half-life of 50 minutes. The data suggest butorphanol distribution in the pregment ewe can be conceptualized by the two compartment model, with the fetus as part of the peripheral compartment. These studies support the clinical finding from other studies that butorphanol appears to be a safe analgesic for use in labor pain.

Placental transfer of intravenous fluoride in the pregnant ewe.

Fluoride ion is produced with the biotransformation of two commonly used anesthetics, methoxyflurane and enflurane. Fluoride ion is added to prenatal vitamin preparations and water to prevent carious teeth. Very high levels of fluoride assailure. Previous studies of placental transfer of fluoride ion were conflicting. Our study in pregnant ewes revealed rapid transfer of the fluoride ion across the placenta with high fetal to maternal ratios as early as 1 minute.

A double-blind comparison of butorphanol and meperidine in labour: maternal pain relief and effect on the newborn.

Butorphanol tartrate 1 mg and 2 mg were compared in 80 normal mothers at term in a double-blind study with meperidine hydrochloride 40 mg and 80 mg for the relief of pain in labour. Butorphanol was found to be as effective as meperidine in relieving pain in labour. The foetal condition, as measured by ECG monitoring, Apgar scores, time to sustained respiration, umbilical venous H+ (pH) and PCO2, and a general nursery survey were comparable for meperidine and butorphanol. No psychomimetic phenomena were seen. Assays indicated that both butorphanol and meperidine crossed the placenta. The mean concentration of butorphanol in neonatal serum was 0.84 times maternal serum at 1.5 to 3.5 hours after intramuscular administration of a single or two successive doses of butorphanol 1 mg or 2 mg to the mother. The mean concentrations for meperidine in neonatal serum was 0.89 times maternal serum at 0.85 to 3.6 hours after intramuscular administration of meperidine 40 mg or 80 mg to the mother. Neither analgesic caused severe depression of the infant except for one meperidine-treated case.

Sickling dynamics of red blood cells and other physiologic studies during anesthesia.

Nineteen patients with electrophoretically proven sickle cell diseases were studied prospectively at intervals, using halothane, methoxyflurane, cyclopropane, and fluroxene. Simultaneous venous and arterial samples were taken from the same arm in heparinized syringes at the sampling intervals and analyzed for blood gases, hematocrit, and percent sickle cells. Measurements of blood pressure, pulse, temperature, tidal volume, minute ventilation, and other significant data were recorded. There were no anesthetic deaths, and the morbidity seen was an extension of pre-existing pathology. Sickling was found to be greatly reduced in both arterial and venous blood during anesthesia, with the greater reduction in venous blood. Following anesthesia, sickling returned toward, but often did not reach, pre-anesthetic levels. Blood-gas measurements reflected the slightly increased ventilation and considerably increased inspired oxygen during anesthesia. Other measurements were not remarkable.