In general, all participating centres found bupivacaine and ropivacaine to be equally effective and without significant adverse neonatal or maternal effects. Time to onset of pain relief, duration of analgesia between top-ups, pain scores, quality of analgesia, extent and duration of sensory block and delivery outcome were similar (Chapter 4).
In some centres, patients receiving ropivacaine were noted to have less motor block – however this difference was statistically significant only in the RHW group. Writer(1) performed a meta-analysis of data from all centres involved in the trial and reported significant results for ropivacaine in terms of reduced motor block, lower instrumental delivery rate and improved NACS scores.
Early comparative studies of bupivacaine and ropivacaine used10-15 ml volumes of a 0.25% solution for initiation of block, followed by either 10ml top-ups or a 6-12 ml/hr continuous infusion for maintenance. However, by the time ropivacaine appeared on the market in 1996, several aspects of its use had changed. Firstly, it was marketed as a mg/ml rather than a % solution, secondly it was released as a 2mg/ml solution (versus2.5mg/ml in initial studies. Finally and most importantly, there was a definite trend towards using lower-strength solutions of bupivacaine (0.125% or even 0.0625%) in combination with a narcotic (fentanyl) for epidural labour analgesia. Also, CSE (combined spinal epidural) analgesia was also emerging as a useful technique.
Using ropivacaine, therefore, was no longer a matter of simply switching from one anaesthetic solution to the other while administering the same volume as before. Moreover, many anaesthetists were satisfied with the quality of analgesia and patient acceptance of these low-dose bupivacaine solutions and saw no reason to change
At the RHW in 1996, for routine labour analgesia, most anaesthetists were using 0.25% bupivacaine with 75-100 mcg fentanyl for initiation of block, followed by an infusion of 0.125% with fentanyl 5mcg/ml. Having already witnessed the efficacy of ropivacaine first hand, in particular its reduced motor block, most of our anaesthetists switched to the new agent (2mg/ml) as soon as it became available. It is now used routinely by eight of our nine specialists and all of our registrars.
Initially, ropivacaine used without fentanyl, but patients seemed to require more frequent top-ups. We then began adding fentanyl, which improved the quality of the analgesia. As there have been few reports in the literature on the use of low-dose ropivacaine + fentanyl – our current regimens have evolved by trial and error. Each anaesthetist has his or her own preference for dosage and volume used. Some examples of regimens currently in use are provided in tables below.
| Drug | Test Dose | Loading Dose | Infusion |
| Lignocaine 2% + adr | 3 mls | - | - |
| Ropivacaine 2mg/ml | - | 12 mls | 47 mls |
| Fentanyl | - | 50 mcgs | 150 mcgs |
(Infusion equivalent to ropivacaine 1.88mg + fentanyl 3 mcg/ml in 50 mls)
| Drug | Test Dose | Loading Dose | Infusion |
| Lignocaine 2% + adr | 6 mls | - | - |
| Ropivacaine 2mg/ml | - | 7 mls | 56 mls |
| Fentanyl | - | - | 200 mcgs |
(Infusion equivalent to ropivacaine 1.87mg + fentanyl 3.3 mcg/ml in 60mls)
| Drug | Test Dose | Loading Dose | Infusion |
| Lignocaine 2% + adr | 3 mls | - | - |
| Ropivacaine 2mg/ml | - | 12 mls | 40 mls |
| Fentanyl | - | 50 | 150 mcgs |
| Normal Saline | - | - | 7 mls |
(Infusion equivalent to ropivacaine 1.6 mg/ml + fentanyl 3 mcg/ml in 50 mls)
Note:
1) Commence infusion at 8ml/hr. Increase up to 12 ml/hr. Cease infusion when preparing for delivery. Pump rate adjustments to be made by midwife.
2) 12.5 mls ropivacaine 2mg/ml is equivalent to 10mls bupivacaine 0.25% or 20mls 0.125% Larger volumes of ropivacaine are required than those you may be accustomed to using with bupivacaine (up to 20 mls if lignocaine is not used for a test dose).
3) Pain usually subsides within 3-4 contractions. Consider using a more potent agent or subarachnoid injection of opioid/local anaesthetic (CSE) if patient in extreme pain.
4) The level of block should be assessed hourly by the midwife. Patients receiving infusions may need to change sides every few hours to prevent unilateral block.
5) ‘Breakthrough pain’ is invariably due to a low level of block on one side and usually responds to a bolus via the infusion pump. Persistent low back pain or deep perineal pain remain a challenge.
6) This agent is suitable for ventouse or low forceps delivery, but consider using a more potent agent for mid-cavity forceps.
7) If the patient requires a caesarean section, discontinue the infusion. Check the level of the block and add 10-12 mls of a more potent agent in increments.
8) Ropivacaine infusions have been used successfully for 1 year now at the Prince of Wales Private Hospital, where midwives do top-ups and infusion syringe changes.
In summary, at the RHW we have found ropivacaine to be an excellent analgesic agent for routine labour. In our experience it is as effective as bupivacaine and more cost-effective. Its increased margin of safety with regard to cardiotoxicity is also appealing.
We have been impressed by the agent’s motor-sparing effect – a feature very well received by patients and midwives. Patients are advised that although they cannot ambulate, they can still move about in bed and should have sufficient motor power to push effectively.
Anecdotally, in both our institutions we have recently observed a reduction to approximately 30% in the instrumental delivery rate of patients receiving ropivacaine epidurals (compared with up to 60% in the bupivacaine patients). Note that in his meta-analysis of the original ropivacaine studies Writer(1) also reported a significant reduction in instrumental delivery rate from 40% to 27%.
We are about to commence offering ambulatory epidurals to our patients. Two regimens will be used, low-dose bupivacaine and low-dose ropivacaine, both in combination with fentanyl.