Anaesthesia, 1990, Volume 45, pages 285-288

Epidural fentanyl and 0.5% bupivacaine for elective Caesarean section

M. J. KING, M . I. BOWDEN

AND

G. M . COOPER

Summary

Either 100 pg fentanyl or 2 ml saline was added to 0.5% bupivacaine administered epidurally for elective Caesarean section in 30 patients, in a double-blind randomised study. Bupivacaine 0.5% was administered until a complete sensory block was established extending to the 4th thoracic dermatome. One of the patients who received epidural fentanyl required intravenous alfentanil and Entonox and another, Entonox only briefy during surgery, compared with seven in the control group who required intravenous aljentanil and Entonox and one who required Entonox only. Postoperative analgesia was of longer duration in those who received epidural fentanyl ( p < 0.01). There were no deleterious efSects on neonatal or maternal outcome.

Key words

Anaesthetic techniques, regional; epidural. Analgesics, narcotic; fentan yl.

Epidural anaesthesia has clear advantages over general anaesthesia for the management of elective Caesarean section. The anaesthetist can avoid manipulation of the maternal airway, the neonate avoids the depressant effects of general anaesthetics and the mother can participate in the birth of her child, encouraging early bonding. However, even with an apparently good block, the mother may experience some discomfort o r even pain during surgical manipulations which may mar the experience for her or worse, necessitate the rapid conversion to general anaesthesia with its inherent risks. Two per cent of patients require conversion of epidural anaesthesia to general anaesthesia despite effective blockade from S,-T4.' Epidural opioids have been widely investigated for labour and postoperative pain in obstetrics, but are not used routinely for Caesarean section. Morphine was administered, in a Scandinavian study,* after the delivery of the baby at Caesarean section, and it was noted that, when this was given in combination with bupivacaine, the discomfort from stretching and dragging of the tissues was less intense. Epidural fentanyl,' in a dose of at least 50 pg again administered after the delivery of the baby, was effective in relief of intra-operative discomfort, which occurred despite blockade from S, to T,.

Some discomfort can occur at the time of delivery and any drug administered subsequently takes a finite time to be effective. The onset of action of epidural fentanyl is faster than most opioids, but there is still a latency of 10-15 minute^,^ favouring early administration. The use of opioid administration before delivery at Caesarean section is inhibited by the fear of neonatal ventilatory depression. This fear has been allayed to an extent by results of s t u d i e P that show low maternal and placental cord blood concentrations of fentanyl after maternal epidural administration. Gaffud et al.' have given epidural fentanyl before delivery a t Caesarean section and found effective analgesia in their assessment of pain at 15-minute intervals. Further study appeared to be indicated so we investigated the efficacy, at specific events during surgery, of the administration of 100 pg fentanyl epidurally before the start of Caesarean section in a randomised double-blind manner. Methods

We studied 30 healthy patients scheduled to undergo elective Caesarean section at a gestation of 36 weeks or greater. Routine antacid prophylaxis (30 ml mist. mag.

M.J. King, MB, FFARCS, Senior Registrar, M.I. Bowden, MB, ChB, Registrar, G.M. Cooper, MB, ChB, FFARCS, Senior Lecturer, Department of Anaesthetics, Birmingham Maternity Hospital, Queen Elizabeth Medical Centre, Birmingham B15 2TG. Accepted I3 September 1989. 0003-2409/90/040285

+ 04 $03.00/0

@ 1990 The Association of Anaesthetists of G t Britain and lrcland

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M . J . King, M.I. Bowden and G.M. Cooper

L

2

5 Z

5

Skin incision

Stretching Peritoneal rectl incision

Delivery

Suture uterus

Manual exploration

Pack removal

.,

Peritoneal closure

Fig. 1. Number of patients in group A (fentanyl) and group B (saline) who experienced mild, moderate or

severe pain at eight operative events. 0 ,mild pain (no treatment); a,moderate pain (entonox); pain (alfentanil).

trisilicate) was the sole premedication. All patients gave consent and the study was approved by the Hospital Ethics Committee. An epidural catheter was inserted via either the L,!, or L,, interspace, with the exception of one patient who had a marked lumbar lordosis that required placement of the catheter in the L,jzinterspace. Bupivacaine 3 ml 0.5% was injected through a Millipore filter as an epidural test dose. A further 7 ml 0.5% bupivacaine was subsequently injected in divided doses over 5 minutes. The maternal circulation was preloaded with 1 litre of compound sodium lactate solution, and maternal arterial blood pressure (Dinamap Critikon) and fetal heart pattern were continuously monitored. Sitting, lateral or wedged to the right positions were maintained throughout. The mothers were randomly allocated to receive the next epidural top-up in divided doses over 10 minutes of, either 8 ml 0.5% bupivacaine plus 100 pg fentanyl (group A) or 8 ml 0.5% bupivacaine plus 2 ml 0.9% saline (group B). These solutions were made up by an independent anaesthetist and neither the anaesthetist involved in the study, nor the patient was aware of whether fentanyl or saline was administered. The level of anaesthesia attained was tested with ethyl chloride spray a t 5-minute intervals. Additional increments (up to 5 ml) of 0.5% bupivacaine were administered until a bilateral sensory block to T, was attained. The total volume injected epidurally and the time taken to attain block to T, were recorded. Intra-operative pain was assessed by the author (M.K. or M.B.) conducting the anaesthetic. The mothers were asked to rank any pain as absent, mild, moderate or severe at eight stimulating events; skin incision, stretching of the recti muscles, peritoneal incision, delivery, suturing the uterus, manual exploration, removal of the pack and peritoneal closure. Mild pain was regarded as discomfort that did not require treatment. Patients were offered Entonox to breathe, if they appeared in more discomfort, and if satisfactory analgesia was provided the pain was confirmed as moderate. Any pain that required intravenous alfentanil in addition to Entonox was classified as severe. Mothers were continually observed for side effects including nausea, vomiting, pruritus, hypotension, sedation and clinical evidence of ventilatory depression (respiratory rate < 12 breaths per minute). Hypotension was defined as a decrease in systolic pressure of 20% or greater. This was treated with further intravenous fluid or ephedrine to maintain normotension throughout the procedure. All patients received syntocinon 10 IU intravenously after delivery.

severe

Neonatal outcome was assessed by Apgar scores at 1 and

5 minutes and umbilical arterial and venous blood gas analysis. All mothers were observed on a recovery unit after operation and subsequently returned to the ward. The next day all were visited by one of the authors and the time of administration of postoperative analgesia recorded. Patients were asked when the sensory and motor blocks had worn off and if they were satisfied with their operation and anaesthesia, and how they perceived the memory of intra-operative discomfort. Patient data and the duration of analgesia were analysed by unpaired t-teat and the requirement for additional intraoperative analgesia and the incidence of complications were compared by Chi-squared test with Yates’ correction for small numbers.

Results Maternal eflects There were no significant differences in maternal age or weight among the 15 mothers in each group, nor in the volume of epidural bupivacaine 0.5% required to produce blockade to T,, nor in the speed of onset of block (Table 1). Figure I shows the number of patients at each surgical event who experienced mild, moderate or severe pain. No patient experienced discomfort at skin incision and those

Table 1. Maternal data and volume of epidural 0.5% bupivacaine, time to achieve block to T, from administration of epidural fentanyl or saline and duration of sensory and motor blocks, mean (SD).

Age, years Weight, kg Volume of bupivacaine administered, ml Time to achieve block to T,, minutes Duration of sensory block, minutes Duration of motor block, minutes *p

Epidural fentanyl and 0.5% bupivacaine for elective caesarean section.

Either 100 micrograms fentanyl or 2 ml saline was added to 0.5% bupivacaine administered epidurally for elective Caesarean section in 30 patients, in ...
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