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SummaryThe effects of 0.08% (Group A ) and0.25% (Group B) Maintenance of epidural analgesia by continuous pump infusion of local anaesthetic into the epidural space has been shown to be effective and safe, and to offer advantages over intermittent top-up procedures. '.* The main advantages for the patient are uninterrupted analgesia and greater safety. For the anaesthetist there is less requirement for time consuming top-up injections.Concentrations selected for infusion epidurals have ranged from 0.0625% to 0.375%, at dose rates from 6.25 mg to over 20 mg/hour of bupivacaine.'-' Recently, it has been shown that a solution of bupivacaine a t a concentration of 0.08% infused at 25 ml/hour is able to provide long periods of uninterrupted analgesia in labour.6 Sixty per cent of the mothers required no supplementary top-ups. It was proposed that increasing the volume infused extended the liquid sleeve of local anaesthetic in the epidural space and caused more dermatomes to remain blocked.

Correspondence procedure,' only 21% of mothers required no top-up, whereas in our series of longer duration, 60% of mothers required no top-up during the infusion. Any reduction in the number of top-ups will improve safety.With regard to the incidence of hypotension in our series, it can be seen that all but one of the top-up related episodes followed the initial bolus injection. We have caused misunderstanding by using the term top-up to include the initial bolus injection as well as subsequent bolus injections. Hypotension, not related to top-ups, occurred in only two patients in either Group A or B; (A, 0.08%. 8, 0.25% bupivacaine at 20 mg/hour). We do not routinely preload all our patients with an intravenous infusion of Hartmann's solution.We believe that the safest way to administer epidural analgesia in labour is by continuous pump infusion. Bupivacaine 0.08% delivered up to a maximum rate of 25 mlihour continues in our experience to be very satisfactory. In Dr Ewen's series, the 25 patients in Group A received 0.08% bupivacaine at 20 mg/hour. There were 12 hypotensive episodes in this group. Eight of these 25 patients had bilateral segmental analgesia above T,.Approximately 50% of Group A patients had severe motor weakness. Only five out of 25 deliveries were spontaneous (and seven out of the total 53 patients). Such intensity and extent of blockade is surely not necessary for analgesia of the labouring mother, and calls into question the safety of the dose regimen. It is worrying that one of the four mothers in Group A (and two out of 10 in Group B) who required Caesarean section had such profound blockade that surgery was performed without supplemental top-up. Ewen et al. have shown that increasing the volume infused extended the blockade, but at a dose rate of 20 mg/hour using 0.08% in a third of the patients the block was surely too extensive.Like Li et d.,* we have found that an infusion of 0.125% bupivacaine at 10 ml/hour is optimal. We studied 45 patients receiving such an infusion during labour, after the establishment of an epidural using 3 ml (test dose) plus 12 ml 0.25% bupivacaine plain. Eighty percent of patients required none or only one top-up of infusion for a mean infusion time of 7 hours until delivery (range 3-13.5 hours); top-up = 10 ml bolus of infusate. Twenty-five patients had good pain relief with the infusion alone for a mean infusion time of 6.5 hours until delivery (range 3-12.5 hours). There were no hypotensive episodes (blood pressure was monitored and recorded using a Datascope Accutor initially at 5-minute and then 30-minute intervals.) No patient had motor blockade intense enough to prevent them turning themselves; this is an advantage which contributes to maternal well-being and is labour-saving. Sixteen of our 45 patients had spontaneous vaginal deliveries; no patient had blockade as high as T,.The safety of such a regimen has already been stressed by Li et al. and they have shown that increasing the dose rate above this confers no additional advantage.2 In the interests...