The effect of epidural anesthesia on uterine activity and blood pressure.

Because of the unresolved controversy regarding the effect of epidural anesthesia upon uterine contractility, it was decided to study its effect on a small number of patients. Intrauterine and intra-arterial continuous pressure, continuous fetal heart rate, and maternal heart rate recordings were obtained from at least 20 minutes before administration of the epidural anesthic until complete dilatation in these patients. Nineteen patients were in spontaneous labor, and 18 had labor stimulated with oxytocin. Plain lidocaine, 1 or 1.5%, was used in 12 patients (30 observations), and lidocaine with epinephrine, 1:200,000 was used in 26 patients (51 observations). Uterine contractions were calculated in Montevideo units for 60 minutes following the epidural anesthetic. The changes, if any, were compared in both groups. There was a significant decrease in uterine activity when epinephrine was added to the anesthetic solution, mainly a lessening of intensity. There were comparable decreases in systolic/diastolic blood pressure in both groups and compensatory tachycardia. In one case, severe hypertension was observed following administration of lidocaine epinephrine. It was concluded that the addition of epinephrine to the anesthetic solution predictably produces diminution of uterine activity, and it does not give "cardiovascular support" to the laboring patient.