Central-block techniques for reliet of labour pain

Abstract

Access to effective pain relief is today a natural part of modem obstetrics. When epidurals for relief of labour pain were introduced during the 1970s, local anaesthetics in high concentrations were used. This caused extensive motor block, affecting propulsive ability during second stage, with increased risk of caesarean and instrumental delivery. There has since been substantial improvement in the technique, with reduced doses and the addition of fat-soluble opioids. The present project sought to investigate and improve techniques concerning central blocks for of labourpain relief.

Dose study: The side-effects of sufentanil are mainly pruritis and sedation. In high doses it has negative effects on the new-born, and it was important to find the lowest effective dose. In a prospective doubleblind study 243 patients were randomised to sufentanil 0.5, 0.75 and 1 µg/mI respectively, in combination with bupivacaine. The analgesic effect was similar in the three groups. While no lowest possible dose was found, the study showed no reason to exceed 0.5 µg/ml in this setting. PCEA study: Patient controlled epidural analgesia, PCEA, is an attractive method in obstetrics, where individual drug requirement varies widely. Some studies show lower drug-consumption when using PCEA than compared to continuous epidural infusion, CEI. We investigated whether this was true for an ultra-low-dose regimen. In a prospective randomised study 80 parturients used ropivacaine 1 mg/ml with sufentanil 0,5 µg/ml, in PCEA, 4 mI bolus dose and 20 minutes lockout, or CEI, 6 ml/hour. Extra dosing was permitted to the same possible maximum dose, 12 ml/hour. The PCEA group used 33 % less drug totally and 25% less drug per hour than the CEI group. Both groups had equally satisfactory analgesia and there was no difference in side-effects.

Spinal study: Epidural analgesia is less effective during second stage and has a rather slow onset. Therefore - and also because of the higher risk for accidental dural puncture in this situation - clinicians may hesitate to perform an epidural if the parturient is entering second stage. Spinal analgesia has a quick onset and a profound analgesic effect when used in combination with epidural. Our descriptive study investigated whether singleshot spinal analgesia is a possible alternative when an epidural is less suitable. Forty multiparae with a rapid labour course, who in late labour requested effective analgesia, received spinal analgesia with sufentanil 7.5 µg and bupivacaine 2 mg. Analgesia was rapid and effective. Seventy-seven percent of the parturients rated the method as excellent. Side effects such as hypotension and pruritis were more pronounced than with low dose epidurals, but easily managed. Active obstetric management is necessary since the duration of block is limited. The obstetrician has to be aware of the risk of a non-reassuring foetal heart rate episode following spinal block.

Population study: There is disagreement whether epidural analgesia affects obstetric outcome. Early studies showed an increase in caesarean and instrumental deliveries when using epidurals. The issue is complex and clinical studies have had problems with selection bias, cross-over and study size. Large studies have shown that low-dose epidurals have less impact on obstetric outcome than traditional epidurals do. We used the Swedish Medical Birth Register in a population-based study of 94,217 nulliparae who gave birth 1998-2000. The frequencies of epidural block in this population were estimated for each delivery unit. The outcomes studied were non-elective caesarean section and instrumental delivery. Delivery units with the lowest (20-29%) and the highest (60-64%) relative frequencies of epidural block had the lowest proportion of caesarean section (9. 1 %). For the other groups the proportion varied between 10.3 % and 10.6%. Instrumental deliveries were most common, 18.8%, in delivery units with 50-59% frequency of epidural block use. The lowest incidence (14.1%) was seen in units using epidurals in 30-39%. In the other groups (20-29%, 4049% and 60-64%) the proportion varied between 15.3 and 15.7 %. There is no association between epidural use and caesarean section and no clear tendency relating epidural use to instrumental delivery. It is not reasonable to abstain from epidural analgesia in pain relief during childbirth with the intention of reducing caesarean section rate.