Lancet 2001;358:19-23
Commentary also in Lancet 2001;358:2.

Authors: COMET Study Group UK  (Comparative Obstetric Mobile Epidural Trial)

Reviewer:  DC Mayer  9/10/01

This prospective randomized study may have significant implications for anesthesiologist in the conduct of regional  analgesia for labor.  It addresses both epidurals and combined spinal epidural (CSE’s), and demonstrates that dilute epidural solutions,  like the one we use here at UNC,  are probably better than more older , more concentrated  regimens.  The outcome measured was the normal vaginal delivery rate in nulliparous women.

Methods:

• Prospective randomization of nulliparous women at 2 UK maternity units desiring regional analgesia were assigned to receive traditional epidurals (TRAD E), a low-dose combined spinal epidural (CSE), or a low-dose epidural infusion (LOW E). Over 300 were enrolled in each group.
• Prehydration.  TRAD E had an epidural test dose with 3ml of 2% lidocaine, then 10ml of 0.25% bupivacaine dosing.  Subsequent top ups were done as needed, but not more frequently than every hour with 10ml of 0.25% bupivacaine. The other two groups (mobile groups)  used 0.1% bupivacaine with 2 mcg/ml of fentanyl for the epidural solution. CSE patients received 1ml 0.25% bupivacaine with 25ug fentanyl through a Sprotte needle. After the spinal dose wore off, they received 15ml of solution, with other 10ml doses up to every 30 minutes as needed for pain relief down the road. LOW E patients received 15ml of solution for the induction, then received 10ml/hr for maintenance.  Breakthrough pain was treated with epidural fentanyl or increasing concentrations of bupivacaine.
• Data collection.  The primary outcome measured was mode of delivery. Secondary outcomes included progress of labor, efficacy of pain relief, effect on neonate, ability to push(subjective) and use of oxytocin. Statistical analysis used chi-squared for discrete variables, and Mann-Whitney U test for VAS. Odds ratios with 95% CI were calculated for the primary outcomes.

Results:

• TRAD E group had 353 pts, CSE group had 351 pts, and LOW E had 350 pts.
• The normal vaginal delivery rate increased by 7.6% in the CSE group and by 7.8% in the LOW E group when compared to the TRAD E group.
• Odds ratios for having a normal vaginal delivery were 1.55 for the CSE group and 1.62 for the LOW E group compared to TRAD E group.
• The c-section rate was similar for all 3 groups, as was the indication for cesarean section being failure to progress.
• Oxytocin use was similar.
• The LOW E group had the highest percentage of women pushing for less than 60 minutes, and also had the highest percentage of women perceiving full motor power and ability to push.
• Pain scores were similar in all groups.
• The LOW E and CSE  groups had a higher percentage of neonates with a  5” APGAR score of less than seven
• The LOW E group had the highest percentage of neonates requiring higher-level resuscitation.
• Overall outcomes and need for NICU care were not different.
• More than a third of women in both the LOW E and CSE groups actually walked or stood.
• The mean amount of bupivacaine used for labor was not different between TRAD E and LOW E, but was significantly less in the CSE group. The mean fentanyl dose was 107 mcg for the CSE group and 179.5 mcg for the LOW E group.

• This study demonstrates the clear advantages of the low dose technique compared to traditional ones. No compromise of pain relief with a clear improvement in the normal vaginal delivery rate occurred.
• The total dose of fentanyl was highest in the LOW E group which may be the cause for a higher level of neonatal resuscitation. Further work on the potential fetal effects is suggested by this study.