Effective obstetric paracervical block with reduced dose of bupivacaine. A prospective randomized double-blind study comparing 25 mg (0.25%) and 12.5 mg (0.125%) of bupivacaine.

BACKGROUND

To study whether paracervical block (PCB) with 12.5 mg (0.125%) of bupivacaine is as effective as with 25 mg (0.25%) and if there are differences in fetal heart rate (FHR) patterns between the doses.

METHODS

A prospective, randomized double-blind study. Fifty-two patients received PCB with 25 mg and 45 patients with 12.5 mg of bupivacaine. Pain intensity was assessed by the patients on a horizontal visual analog scale (VAS). Fetal heart rates of the fetuses were analyzed visually concerning basal rate, variability, accelerations, bradycardia, silent pattern and decelerations.

RESULTS

The pain relief was statistically significant in both groups up to 120 min after PCB. The VAS-values were similar in both groups both before and after PCB. Fetal heart rate changes appeared in both groups more frequently after than prior to PCB. In patients receiving 25 mg of bupivacaine there appeared to be more FHR changes than in those receiving 12.5 mg.

CONCLUSIONS

Paracervical block with 12.5 mg of bupivacaine is an effective method to relieve pain during labor. Fetal heart rate changes seemed to appear less frequently with this reduced dose. It seems that by lowering the dose of bupivacaine it is possible to reduce fetal side-effects without losing analgesic effect.