Thomas C. Key

Hemodynamic effects of intravenous cocaine on the pregnant ewe and fetus

Cocaine is a potent vasoconstrictive agent that is currently the subject of widespread drug abuse. Because little is known of the physiologic responses to cocaine in pregnancy, the effects of intravenous cocaine on uterine blood flow and other maternal and fetal cardiovascular parameters were studied. Eight ewes in late pregnancy were equipped with electromagnetic flow probes around both uterine arteries and catheters were placed in the maternal and fetal inferior vena cavae and aortas. Bolus intravenous infusion of 0.5 and 1.0 mg/kg of maternal body weight achieved peak plasma cocaine levels similar to those observed in human subjects after abuse of the drug (mean level = 229 to 400 ng/ml, n = 8). After bolus infusion of 0.5 or 1.0 mg/kg of cocaine, mean maternal arterial pressure increased 32% and 37%, respectively (p less than 0.005). Fetal blood pressure rose 12.6% after a dosage of 0.5 mg/kg of cocaine. These cocaine infusions significantly decreased uterine blood flow by 36% and 42% for a duration of 15 minutes (p less than 0.005). Analysis of maternal catecholamine responses demonstrated a significant (210%) rise in plasma norepinephrine levels after cocaine infusion. These studies demonstrate that cocaine, when administered in doses that produce plasma levels observed in humans, significantly decreases uterine blood flow for a duration of greater than or equal to 15 minutes while inducing a hypertensive response in the pregnant ewe and fetus.

Predictive value of early pregnancy glycohemoglobin in the insulin-treated diabetic patient

The influence of early pregnancy glycemic control as measured by hemoglobin A1c concentration and the incidence of congenital anomalies and spontaneous abortions were evaluated in women presenting for prenatal care with insulin-treated diabetes in a population whose glycemic control was poor. Thirty-one abnormal outcomes were seen in 83 pregnancies (37%). There were 22 spontaneous abortions and nine major congenital anomalies. No woman with an early pregnancy hemoglobin A1C value less than 9.5% had an infant with a congenital anomaly and a single woman experienced a spontaneous abortion (4%). Conversely, in women with an early pregnancy hemoglobin A1C value greater than or equal to 9.5%, congenital anomalies occurred in 24% and spontaneous abortion in 35%. Outcomes of pregnancies in type 1 and type 11 diabetic women were comparable. A strong statistical relationship between hemoglobin A1C and adverse pregnancy outcomes was demonstrated. These results strongly suggest that poor glycemic control during early pregnancy adversely influences pregnancy outcomes; the greater the degree of poor control, the greater the impact on pregnancy outcome. The data further justify the need for preconceptional control in diabetic woman and for careful evaluation of the fetus during pregnancy in the woman with insulin-treated diabetes.

Successful pregnancy after cardiac transplantation

Summary A case report of a successful pregnancy after cardiac allotransplantation is presented. The patient underwent transplantation for an inoperable cardiac tumor 5 years before conception. Cardiac function before and during all stages of pregnancy was normal. Maintenance immunosuppressive therapy consisting of prednisone and azathioprine was continued through gestation. The pregnancy was complicated by a primary herpes virus infection requiring parenteral acyclovir treatment and a single episode of preterm labor that was successfully treated. The infant was born at term, weighed 3278 gm, and has developed normally during the first 3 years of life. The patient died 5 months after delivery as a result of an acute immunologic rejection 5 months post partum caused by self-initiated discontinuation of immunosuppressive therapy. Preconceptional counseling and pregnancy care guidelines are discussed. (Am J Obstet Gynecol 1989;160:367-71.)

The effects of maternally administered magnesium sulfate on the neonate

The effects of parenterally administered magnesium sulfate on maternal and neonatal calcium and magnesium metabolism in nonasphyxiated, term pregnancies complicated by pregnancy-induced hypertension were studied prospectively. In addition, the neurobehavioral effects of neonatal hypermagnesemia were investigated by means of a neonatal assessment scale that specifically measures reflex activity and both passive and active muscle tone. Maternal magnesium sulfate infusion was associated with maternal and neonatal hypermagnesemia when compared with that of control subjects (1.8 +/- 0.10 to 3.6 +/- 0.5 mg/dl, p less than 0.001, and 1.75 +/- 0.2 to 3.6 +/- 0.5 mg/dl, p less than 0.005, respectively). Maternal serum calcium levels fell with magnesium therapy (9.3 +/- 0.18 to 7.9 +/- 0.1 mg/dl, p less than 0.001), while neonatal calcium levels were unaffected (10.8 +/- 0.44 to 10.5 +/- 0.38 mg/dl, p less than 0.05). Neurological status examinations in the neonate were similar in both the control and treatment groups. In addition, neurological performance of the neonate did not correlate with cord magnesium levels or to the total dose of magnesium administered.

Evaluation of the use of continuous lumbar epidural anesthesia for hypertensive pregnant women in labor

The use of continuous lumbar epidural anesthesia in women with pregnancy-induced hypertension remains controversial. We retrospectively reviewed the charts of 285 women with pregnancy-induced hypertension who were delivered in a 2-year period. Among 185 vaginally delivered patients who received continuous lumbar epidural or local anesthesia, there were no significant differences in the incidence of maternal hypotension, abnormal fetal heart rate tracings, low Apgar scores, or neonatal intensive care unit admissions. Of 100 patients delivered by cesarean section, the incidence of low Apgar scores, depressed umbilical cord pH values, and neonatal intensive care unit admission was increased among those who received general anesthesia (p less than 0.05). However, general anesthesia patients were more likely to have abnormal fetal heart rate tracings (27% versus 4%) requiring urgent delivery. Thus differences in outcome probably reflect poorer fetal condition prior to anesthesia induction rather than a specific anesthetic effect. These results demonstrate that continuous lumbar epidural anesthesia is safe and effective for both the fetus and the mother with pregnancy-induced hypertension.

The ultrasonographic estimation of fetal weight in the very low-birth weight infant

Abstract The clinical estimation of fetal weight is notoriously inaccurate, especially when the fetus is very small. However, the ability to obtain easily an accurate estimate of the fetal weight is vital in the comprehensive evaluation and management of a pregnancy in which the delivery of a very low-birth weight infant is imminent. Recent ultrasonographic techniques have provided clinically useful assessments of fetal weight, but the ability of the techniques to estimate the birth weight of infants accurately in the highly critical, very low-birth weight range has not been established. In a prospective study of 50 consecutive pregnancies of women delivered prematurely of infants weighing 500 to 1,500 gm, estimates of fetal weight by means of ultrasonographic mensuration of the fetus and mathematical extrapolation to birth weight were compared with neonatal weights. Each composite ultrasound measurement and mathematical relationship was compared statistically with neonatal measurements in 20 infants. The mean error of the estimated fetal weight was −15.1 ± 71.5 gm and the absolute error was 52.3 ± 48.5 gm. The mean percentage error was −0.8 ± 6.1. Estimates of birth weight were within 10% of the neonatal weight in 92% of the pregnancies studied, within 5% in 70%, and within 2.5% in 34%. The accuracy of the technique was uniform throughout the weight range studied with a mean absolute error of 5.0% ± 3.6%. All composite ultrasonographic measurements accurately predicted neonatal measurements. The accuracy of the technique was unaffected by the fetal presentation, the amount of amniotic fluid, or placental location. The technique is one that can be used by the obstetrician with basic real-time ultrasound skills on the labor and delivery service.

Ritodrine inhibition of hypoxic pulmonary vasoconstriction

The effect of ritodrine hydrochloride on hypoxic pulmonary vasoconstriction (HPV), the normal control mechanism for shunting blood flow away from nonventilated areas of the lung, was studied in nonpregnant dogs equipped with central monitors and electromagnetic flow probes. The systemic infusion of ritodrine at a dose of 4 micrograms/kg/min resulted in a 66.4% +/- 4.6% decrease in the HPV response, whether administered before or after the induction of isolated lobar hypoxia. These findings have significant implications for the patient who develops pulmonary edema during ritodrine therapy, in which inability to bypass nonventilated areas of the lung would serve to aggravate further the ventilation/perfusion inequalities that already exist.

Maternal cardiovascular response to caffeine infusion in the pregnant ewe

The effect of maternal caffeine infusion on uterine blood flow and fetal oxygenation was studied in chronically catheterized pregnant sheep equipped with electromagnetic flow probes. The systemic administration of caffeine in doses of 8 and 24 mg/kg of body weight resulted in peak maternal serum levels of 16.7 +/- 0.9 and 38.5 +/- 2.1 micrograms/ml and fetal serum levels of 10.9 +/- 0.7 and 34.9 +/- 4.5 micrograms/ml, respectively. While no significant effects were noted at the 8 mg/kg dose, administration of 24 mg/kg was associated with a 5% reduction in uterine blood flow (p less than 0.05) and a 7% increase in mean arterial pressure (p less than 0.05). No significant alteration in maternal or fetal oxygenation occurred at either dose. These findings suggest that any adverse effects on fetal development attributed to caffeine are not likely exerted by influencing uterine blood flow.

Life-threatening effects of intravascular absorption of PGF2 alpha during therapeutic termination of pregnancy.

A case of inadvertent intravascular injection of PGF2alpha during induction of labor by intraamniotic injection for fetal demise involving alternating extreme hypotension and hypertension is described. The woman was a 29-year old in late 2nd trimester with oligohydramnios but no other related history. She was given epidural anesthesia 7.5 mg midazolam and 5 mg morphine S04 for anxiety. Because of oligohydramnios 300 ml Ringers lactate was instilled to dilute the PG. A test dose of 1 mg PGF2alpha was tolerated well. 80 g urea and 20 mg PGF2alpha were injected over 10 minutes. A few minutes later contractions began followed by complaints of burning on face and chest and dyspnea. Oxygen was given by mask. Systolic pressure fell to 70 mm by cuff; peripheral pulses could not be palpated but the patient remained alert and oriented. She was given 35 mg ephedrine and increased iv fluids. She remained dyspneic her extremities became mottled and she complained of chest pressure severe headache and severe breast tenderness. Blood pressure rose to 220/135 mm Hg; pulse to 95 and respiratory rate to 44. Pulse oximetry detectable at the earlobe only was 94% saturation. After 50 mg labetalol blood pressure fell to 134/77 but symptoms remained. For 2 hours blood pressure swung between 76/50 and 225/125 until delivery of the fetus. An arterial line could not be started because of extreme vasoconstriction. Central venous pressure was 13 cm H20. After artificial rupture of the membranes and removal of remaining PG blood pressure stabilized. Delivery was accomplished without incident. The symptoms and labile blood pressure were considered to be due to intravascular injection of PGF2alpha caused by repeated bolus injection at each uterine contraction. In case of PG induction for fetal demise it is recommended that anesthesiologists be prepared to treat intravascular collapse hypertension and bronchoconstriction.