Speed of onset of analgesia in labour and maternal satisfaction: comparison of epidural and combined spinal-epidural

Abstract

I read with great interest the study by Nickells et al. (Nickells et al. Anaesthesia 2000; 55: 17–20) that compared the speed of onset of analgesia of combined spinal epidural (CSE) with epidural alone (using a mixture of low-dose local anaesthetic and opioid). They also examined the incidence of side-effects of these techniques compatible with the concept of ‘walking epidural analgesia’ or ‘analgesia with minimal motor blockade’ that are thought not to adversely affect obstetric outcome. The end point was the occurrence of the first ‘comfortable contraction’, which reflects most women's wishes, but the onset time began only after the injection of the anaesthetic mixture through the epidural catheter or the spinal needle, as in other similar studies. We presume that what is really meaningful for women is the time lapse from their request to efficient analgesia. The complexity of CSE increases the time to perform the technique (needle through needle in this case), which would tend to reduce or reverse the small difference of 2 min found in this study in favour of CSE. Another cause for delay could be the recommendation to wear a sterile gown above all for the CSE technique [1]. Furthermore, there is no classical lidocaine–epinephrine ‘test dose’ of the catheter in this study. The value of this test is highly debated in low-dose epidural local analgesia with opioid or CSE [2, 3]. Consequently I propose to return to the original technique for peridural anaesthesia for surgery; that is to first inject an anaesthetic mixture through the Tuohy needle before the sometimes problematic placement of the catheter. I formerly reserved this method for painful labour, agitation or cervical dilatation greater than 6 cm, but now I use it more often. When the Tuohy needle is in the epidural space, the parturient is informed that she may experience slight lumbar discomfort during the first injection (in more than half the cases). Then 15–20 ml of bupivacaine 0.1% + 7.5–10 µg sufentanil are injected in 2–3 increments with intermittent aspiration (total dose depending of the case). Afterwards, the catheter is threaded into the epidural space, aspirated and secured in the conventional manner, while analgesia sets in. During this ‘first dose’, heart rate and blood pressure are monitored and parturients are questioned regarding symptoms of dizziness and altered sensation in the legs. This first injection always hastens the onset of analgesia, especially when, far from rarely, the epidural catheter is difficult to insert. This injection also facilitates introduction of the catheter and reduces the risks of venous cannulation [4], especially when using a soft catheter [5]. I have observed that this injection practically suppresses pain and movement that may occur during manipulation of catheters, and eliminating some inadvertent dural taps. The idea of examining this technique locally in a comparative prospective study (with a start time beginning when the anaesthetist enters the delivery suite) has been postponed because of other priorities. Personally, I am surprised by the ‘success story’ of CSE, where the bacteriological risk is real, just to try to gain a few seconds or minutes of quicker onset of analgesia compared with several hours of pain. Finally, in a recent prospective study the authors found that CSE ‘performed no better than equivalent epidural technique based on the views of the labouring women’[6] even with a first peridural injection through the catheter.