Initiating extradural analgesia during labour: comparison of three different bupivacaine concentrations used as the loading dose.
OBJECTIVE
Potential effects of extradural analgesia on the progress of labour and obstetric outcome are still a matter of concern and the focus of ongoing debates. Despite this, little attention is paid to the initiation of extradural labour analgesia. The objective of this prospective, randomized, double-blind trial was to identify the optimal of three concentrations of bupivacaine used as a loading bolus for initiating extradural analgesia during labour.


METHODS
Sixty-seven full-term parturients requesting extradural analgesia received either bupivacaine 0.25% (group A), 0.125% (group B) or 0. 0625% (group C). Bupivacaine administration was titrated to achieve a pain score </=1.5 on a 10-cm visual analogue scale (VAS) and was limited to a maximum of 20 ml of the study drug. We recorded the time to achieve a VAS </=1.5, the total amount of local anaesthetic used, sensory level, maternal and foetal as well as neonatal side effects.


RESULTS
The probability of obtaining a VAS pain score </=1. 5 was significantly lower in group C. Although mean times to reach a VAS pain score </=1.5 were not statistically different, survival curves show a significantly lower probability for reaching this score. Significantly more parturients in group A developed a motor block >/=1 based on using a modified Bromage scoring scale. There were no differences in incidence of maternal hypotension, ephedrine requirements, foetal heart rate abnormalities, mode of delivery and neonatal outcome.


CONCLUSIONS
Of the three concentrations used in this clinical setting, 0.125% was the most suitable concentration of plain bupivacaine to initiate extradural analgesia in labour. Using 0.25% bupivacaine increased the incidence of motor block, whereas for 0.0625% plain bupivacaine the probability to achieve adequate analgesia was unacceptably low.
Harms
C
C
Department of Anaesthesia, University of Basel, Kantonsspital, Basel, Switzerland. harms@ubaclu.unibas.ch
Siegemund
M
M
Marsch
S C
SC
Surbek
D V
DV
Hösli
I
I
Schneider
M C
MC
D016362:Analgesia, Obstetrical; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects; D001034:Apgar Score; D002045:Bupivacaine / Q000008:administration & dosage* / Q000009:adverse effects; D004311:Double-Blind Method; D005260:Female; D006340:Heart Rate, Fetal; D006801:Humans; D007743:Labor, Obstetric; D011247:Pregnancy
D000779:Anesthetics, Local; D002045:Bupivacaine