Efficacy of augmentation of epidural analgesia for Caesarean section

J. C. Tortosa1, N. S. Parry2, F. J. Mercier1, J. X. Mazoit1 and D. Benhamou*,1

1 Département d’Anesthésie-Réanimation Chirurgicale, Hôpital Antoine Béclère, F-92141 Clamart Cedex, France 2 Present address: Department of Anaesthesia, Hope Hospital, Manchester M6 8HD, UK

Corresponding author. E-mail: dan.benhamou@bct.ap-hop-paris.fr

Accepted for publication: April 29, 2003


    Abstract
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Background. Extension of a labour epidural for Caesarean delivery is thought to be successful in most cases and avoids the use of general anaesthesia. However, most previous studies that have estimated the failure rate of pre-existing epidural catheters were performed in small numbers of patients.

Methods. Therefore, we undertook to retrospectively measure the failure rate of indwelling epidural catheters in a large number of patients.

Results. The anaesthetic team was available at all times and was permanently led by a senior anaesthetist specialized in obstetrics. Extension was performed using lidocaine 2% with epinephrine (mean 18 (SD 6) ml), combined in most patients with sufentanil (9 (2.2) µg) and/or clonidine (75 µg). Among 194 consecutive extensions performed in a 1-yr period, general anaesthesia was required in five patients (2.6%) while sedation and/or i.v. analgesia were used in 27 patients (13.9%). In three cases where general anaesthesia was required, the interval between decision to incision was <10 min. No factor associated with failure could be identified. Addition of a lipophilic opioid or of clonidine did not modify the efficacy of the block (i.e. general anaesthesia or supplementation were required in a similar proportion).

Conclusions. The augmentation of labour epidurals for Caesarean section using lidocaine 2% plus epinephrine is a reliable and effective technique. No factor associated with failure could be identified.

Br J Anaesth 2003; 91: 532–5

Keywords: anaesthesia, obstetric; anaesthesia, obstetric, Caesarean section; anaesthetics local, lidocaine; analgesics opioid, sufentanil


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
General anaesthesia for Caesarean section is associated with an increased risk of maternal mortality,1 2 especially as it is often carried out in an emergency situation. It is therefore standard practice to use regional anaesthesia wherever possible. However, attaining high rates of regional anaesthesia in this context depends on both organizational and technical factors.3 The use of epidurals during labour affords the possibility of rapid augmentation (i.e. injection through the catheter of a dose of a local anaesthetic of a suitable concentration for surgery) to provide anaesthesia in the case of emergency Caesarean section.

Several studies have sought to determine which local anaesthetic, at what dose, and in combination with which other agents (epinephrine, clonidine, opioids, bicarbonate) is most effective.36 Although chloropracaine 3% may have the fastest onset, this agent is not available in most European countries.7 A study by Price and colleagues8 in 1991 showed that the epidural injection of lidocaine 2%, 20 ml with epinephrine 1:200 000 reliably augmented a labour epidural within the time frame necessary for urgent Caesarean section. Indeed, they reported a 100% success rate using this method. However, because of the small number of patients (n=36) in that study, the true efficacy of this technique remains questionable.

We adopted the practice of extending labour epidurals for Caesarean section with a large dose of lidocaine in 1991. Our primary hypothesis was to verify that ‘extension’ of an epidural analgesia previously used during labour is successful in most cases and avoids the use of general anaesthesia. This retrospective study evaluates the technique by analysing the anaesthetic records of a large number of women undergoing emergency Caesarean section during labour. We have also sought to identify factors that are associated with failure of the technique in these cases.


    Methods
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
The obstetric unit at our hospital manages approximately 2500 deliveries per year and has a 20% Caesarean section rate. The institution procedure of epidural labour analgesia is based on a combination of bupivacaine 0.08% and sufentanil 0.5 µg ml–1 used as an epidural infusion after an initial bolus of 15 ml of the same solution. More than 90% of women in labour receive an epidural during labour. Top-ups during labour are also made with the same solution. All parturients receive this mixture. The anaesthetic team is available at all times and is permanently led by a senior anaesthetist specialized in obstetrics. The case notes of all non-elective Caesarean sections performed during a 1-yr period (1998) were studied. For each patient, the following sets of data were gathered:

(i) Patient characteristics: age; height; weight before pregnancy and before delivery.

(ii) Anaesthetic data: ASA grade; Mallampati score; mouth opening; previous intubations.

(iii) Data pertaining to the siting of the labour epidural: Visual analogue pain score before the epidural; grade of anaesthetist siting the epidural (senior or trainee); intervertebral space used; depth of epidural space; length of catheter left in space; complications arising.

(iv) Data pertaining to the adequacy of the epidural analgesia: Visual analogue pain score after initial bolus; right and left sensory levels after 30 min; Bromage score at 30 min; initial flow-rate of the epidural infusion; number of extra boluses needed; pain scores during labour; duration of the epidural for labour. Inadequacy of epidural analgesia was judged according to the criteria set down by Le Coq and colleagues9 (i.e. three or more interventions aimed at improving the quality of the analgesia, e.g. epidural bolus, increase of the epidural infusion flow rate).

(v) Data pertaining to the augmentation of the epidural for Caesarean section: grade of anaesthetist present (senior or trainee); sensory level (to temperature) before augmentation; volume of lidocaine 2% with epinephrine 1:200 000 used; dose of epidural sufentanil used; dose of epidural clonidine used; sensory level after augmentation; inadequate augmentation defined as when i.v. or inhaled supplementation (midazolam, opioids, volatile anaesthetics, nitrous oxide) was used, but without recourse to general anaesthesia; augmentation-incision time interval.

(vi) Obstetric data: gravidity; parity; term; fetal presentation; presence of multiple pregnancy; duration of labour; time interval between decision to perform Caesarean and incision (greater or less than 10 min).

(vii) Neonatal data: Apgar scores at 1 and 5 min; umbilical artery pH.

(viii) Failure of extension. Epidural anaesthesia was deemed to have failed if general anaesthesia became necessary.

Results are given as a mean (SD) for continuous variables and median (range) for discontinuous variables. Qualitative variables are expressed as a percentage. Statistical analysis was performed using Student’s t-test for unpaired and normally distributed variables and the {chi}2-test to compare percentages (Statview® 5.0 for Macintosh, SAS Institute Inc., NC, USA). The Mann–Whitney U-test was used to compare discontinuous data. A P-value of <0.05 was considered significant.


    Results
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
In total, 315 non-elective Caesarean sections were carried out in this 1-yr period. Of these, 35 had missing or incomplete case notes. Of the remaining 280, 194 were cases in which the anaesthetic technique initially chosen was augmentation of a pre-existing labour epidural. Within this group, general anaesthesia was used 5 times (2.6% (95% CI 0.8–5.8)). One case was attributable to ‘maternal distress caused by anxiety’, despite an adequate sensory block having been demonstrated. Four patients required general anaesthesia because of inadequate cephalic extension of the epidural block. In one patient, spread remained limited although sufficient time had elapsed after topping up. In the three other patients, the time interval available between the decision to perform a Caesarean section and incision was <10 min. When the time available between decision to perform a Caesarean section and incision was <10 min, 25% of patients required supplementation (vs 13.6% when the time available was >10 min; P=0.078).

I.V. or inhaled supplementation was necessary in 27 patients (13.9%). There was no significant difference in patient characteristics, anaesthetic data, or data pertaining to the siting and analgesic adequacy of the labour epidural between those who had (had not) adequate extension (Tables 13). There was no relationship between the use of epidural clonidine and/or sufentanil and the need for supplementation (Table 2). Trainee and senior anaesthetists provided adequate anaesthesia without supplementation in 83% and 84% of the cases respectively.


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Table 1 Patient characteristics. No significant differences. Data are mean (SD) or median (range)
 

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Table 3 Intraoperative data. No significant differences. Data are mean (SD) or median (range) unless indicated
 

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Table 2 Adequacy of labour epidural analgesia. No significant differences. Data are mean (SD) or median (range). VAPS, visual analogue pain score
 

    Discussion
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
In this study, augmentation of a labour epidural for Caesarean section failed to the point of recourse to general anaesthesia in 2.6% of patients. This confirms the efficacy of the technique. None of the factors pertaining to the experience of the anaesthetist, location of the epidural, or its analgesic efficacy during labour were found to be associated with an increased risk of failure. In three of the five failures, the time before efficient block was too long, indicating that the failure rate could have been larger had we studied only emergency situations where there is immediate threat to life of the mother or fetus.10 In the other cases, the duration was 14 (7) min, which is similar to previous reports.4 5 8

This failure rate is towards the lower end of the range of failure rates reported elsewhere. Price and colleagues8 and Gaiser and colleagues4 5 reported failure rates of zero. Others have reported rates of 5.7%,10 7%,3 8%,11 or up to 38%.6 In the largest study to date (n=827), the incidence of conversion to general anaesthesia with an epidural catheter in situ was 10.5%.12 Although almost all epidural Caesarean sections were non-elective, the exact proportion is not stated. In that study, however, excluding patients in whom top-up was not attempted, left a failure rate of 2.2%, a result very close to ours. Our results are also close to those of Tsen and colleagues,13 despite their study including elective Caesarean sections as well as emergencies. These differences in failure rates might be explained by variable (and sometimes unspecified) definitions of failure. In our study, if we had included cases in which i.v. or inhaled supplementation was necessary, the ‘failure’ rate would have risen to 16.5%.

We found no factors associated with failure (technical conditions, height, weight, depth of the epidural space, length of catheter in space, duration of labour, use of combined spinal epidural anaesthesia). Because this might have been related to the very small number of failures (n=5), analysis was performed again to search for risk factors for supplementation, but no single factor could be found (Tables 13). In contrast, Riley and colleagues11 found that the need for supplementary epidural boluses during labour and management by a non-obstetric anaesthetist were risk factors for the failure of augmentation. A major difference might be that our patients are cared for night and day by an anaesthetist specialized in obstetrics.

At our institution, we only use lidocaine to augment labour epidurals for emergency Caesarean section. Our practice is therefore similar to that of Riley and colleagues.11 The choice of agent is an important one. Establishment of a sensory block is more rapid with chloroprocaine,5 but the difference is clinically small and this agent is not available in France. Lucas and colleagues14 observed a higher success rate for augmentation of the epidural block using bupivacaine rather than lidocaine. However, the volume of bupivacaine necessary was large (20 ml). Indeed, Dickson and colleagues,6 using bupivacaine 0.5%, 10 ml observed that ~30 min were necessary to extend the block height to T4.6 This delay is incompatible with emergency Caesarean section.10 Moreover, rapid injection of high doses of bupivacaine exposes the patient to the risks of cardiotoxicity. For these reasons, we use lidocaine.

We found that the addition of opioids and/or clonidine did not decrease the need for supplementation. This is surprising given the analgesic efficacy of these substances in other clinical situations.1517 A possible explanation is that pre-existing partial conduction block, caused by the local anaesthetic agents used during labour, allows a subsequent dose to increase the density of the block very rapidly.18 Another possible explanation is the insufficient power of our study. Power calculations indicate that two groups of 293 patients each would be necessary to demonstrate any difference attributable to sufentanil. However, large numbers needed to demonstrate a difference suggest that the effect, if any, is small and possibly not relevant to clinical practice.

The augmentation of labour epidurals for Caesarean section is a reliable and effective technique. The addition of opioids and/or clonidine to the local anaesthetic does not appear to decrease failure rate or the need for supplementation.


    References
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Report on confidential enquiries into maternal deaths in England and Wales 1979–1981. Department of Health & Social Security. Report on Health & Social Subjects 11,14,26,29. London: HMSO, 1986

2 Report on confidential enquiries into maternal deaths in England and Wales 1982–1984. Department of Health. Report on Health & Social Subjects 34. London: HMSO, 1989: 95

3 Morgan BM, Magni V, Goroszenuik. Anaesthesia for emergency Caesarean section. Br J Obstet Gynaecol 1990; 97: 420–4[ISI][Medline]

4 Gaiser RR, Cheek TG, Gutsche BB. Epidural lidocaine versus 2-chloroprocaine for fetal distress requiring urgent Cesarean section. Int J Obstet Anesth 1994; 3: 208–10

5 Gaiser RR, Cheek TG, Adams HK, Gutsche BB. Epidural lidocaine for Cesarean delivery of the distressed fetus. Int J Obstet Anesth 1998; 7: 27–31[ISI]

6 Dickson MAS, Jenkins J. Extension of epidural blockade for emergency Caesarean section. Anaesthesia 1994; 94: 636–8

7 Yentis SM, Bjornestad E. Extending labour epidural analgesia for emergency Caeasrean section: a European argument for 2-chloroproacaine. Eur J Anaesthesiol 2002; 19 [Suppl. 24]: A564

8 Price ML, Reynolds F, Morgan BM. Extending epidural blockade for emergency Caesarean section. Int J Obstet Anesth 1991; 1: 13–18

9 Le Coq G, Ducot B, Benhamou D. Risk factors of inadequate pain relief during epidural analgesia for labour and delivery. Can J Anaesth 1998; 45: 719–23[Abstract]

10 Lucas DN, Yentis SM, Kinsella SM, et al. Urgency of Caesarean section: a new classification. J R Soc Med 2000; 93: 346–50[Abstract]

11 Riley ET, Papasin J. Epidural catheter function during labor predicts anesthetic efficacy for subsequent Cesarean delivery. Int J Obstet Anesth 2002; 11: 81–4[CrossRef][ISI]

12 Garry M, Davies S. Failure of regional blockade for Caesarean section. Int J Obstet Anesth 2002; 11: 9–12[CrossRef][ISI]

13 Tsen C, Pitner R, Camann WR. General anesthesia for Cesarean section at tertiary care hospital 1990–1995: indication and implications. Int J Obstet Anesth 1998; 7: 147–52[ISI]

14 Lucas DN, Ciccone GK, Yentis SM. Extending low dose epidural analgesia for emergency Caesarean section. Anaesthesia 1999; 54: 1173–7[CrossRef][ISI][Medline]

15 Yee I, Carstoniu J, Halpern S, Pittini R. A comparison of two doses of epidural fentanyl during Caesarean section. Can J Anaesth 1993; 40: 722–5[Abstract]

16 Madej TH, Strunin L. Comparison of epidural fentanyl with sufentanil. Analgesia and side-effects after a single bolus dose during elective Caesarean section. Anaesthesia 1987; 42: 1156–61[ISI][Medline]

17 Eisenach JC, De Kock M, Klimscha W. Alpha(2)-adrenergic agonists for regional anesthesia. A clinical review of clonidine (1984–1995). Anesthesiology 1996; 85: 655–74[ISI][Medline]

18 Raymond SA, Steffensen SC, Gugigo LD, Strichartz GR. The role of the length of nerve exposed to local anesthetics in impulse blocking action. Anesth Analg 1989; 68: 563–70[Abstract]





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