The bupivacaine paracervical block in labor and its effect on quantitative uterine activity.

This study utilized internal fetal monitoring and an on-line voltage control oscillator for measurement of uterine activity unit (UAU) determination in patients who received a paracervical block (PCB) with the use of bupivacaine hydrochloride (Marcaine). The total dose of 25 mg (5 cc/side) of 0.25% bupivacaine used for PCB in 32 patients produced no ill effects to the fetus, as reflected by baseline fetal heart rate (FHR), beat-to-beat variablity, or Apgar scores. No adverse maternal effects were noted, and anesthesia was rated good or excellent in 81% of patients. Rate of cervical dilation remained the same or increased in 29 of 32 patients. Quantitative UAUs showed a significant decrease in the third 10-minute interval after block in primiparas, but no significant change in multiparas or in the group taken as a whole. Total UAUs before versus after PCB for either group or taken together were not statistically different. A decreasing trend in UAUs after PCB versus a positive regression line from activity prior to the block was noted.