Print version ISSN 0256-9574
SAMJ, S. Afr. med. j. vol.100 no.5 Cape Town May 2010
Caesarean section wound infiltration with local anaesthetic for postoperative pain relief - any benefit?
Anthony Akinloye BamigboyeI; George Justus HofmeyrII
IFCOG (SA). Department of Obstetrics and Gynaecology, University of the Witwatersrand, and Sandton Medi-Clinic, Johannesburg, and Visiting Consultant Gynaecologist, University Teaching Hospital, Ado Ekiti, Nigeria
IIMRCOG. Effective Care Research Unit, University of the Witwatersrand, Johannesburg, and University of Fort Hare, East London, E Cape
Delivery by caesarean section (CS) is becoming more frequent. Childbirth is an emotion-filled event, and the mother needs to bond with her baby as early as possible. Any intervention that leads to improvement in pain relief is worthy of investigation. Local anaesthetics have been employed as an adjunct to other methods of postoperative pain relief, but reports on the effectiveness of this strategy are conflicting. This review attempted to assess the effects of local anaesthetic agent wound infiltration and/or abdominal nerve blocks on pain after CS and the mother's well-being and interaction with her baby.
METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (April 2009).The selection criteria were randomised controlled trials of local analgesia during CS to reduce pain afterwards. Twenty studies (1 150 women) were included.
RESULTS: Women who had wound infiltration after CS performed under regional analgesia had a decrease in morphine consumption at 24 hours compared with placebo (morphine dose -1.70 mg; 95% confidence interval (CI) -2.75 to -0.94). Women who had wound infiltration and peritoneal spraying with local anaesthetic after CS under general anaesthesia (1 study, 100 participants) had a reduced need for opioid rescue (risk ratio (RR) 0.51; 95% CI 0.38 to 0.69). The numerical pain score (0 -10) within the first hour was also reduced (mean difference (MD) -1.46; 95% CI -2.60 to -0.32). Women with regional analgesia who had local anaesthetic and non-steroidal anti-inflammatory cocktail wound infiltration consumed less morphine (1 study, 60 participants; MD -7.40 mg; 95% CI -9.58 to -5.22) compared with those who had local anaesthetic control. Women who had regional analgesia with abdominal nerve blocks had decreased opioid consumption (4 studies, 175 participants; MD -25.80 mg; 95% CI -50.39 to -5.37). For outcome in terms of the visual analogue pain score (0 - 10) over 24 hours, no advantage was demonstrated in the single study of 50 participants who had wound infiltration with a mixture of local analgesia and narcotics versus local analgesia.
CONCLUSIONS: Local anaesthetic infiltration and abdominal nerve blocks as adjuncts to regional analgesia and general anaesthesia are of benefit in CS by reducing opioid consumption. Non-steroidal anti-inflammatory drugs may provide additional pain relief.
Delivery by caesarean section (CS) is becoming more frequent and is one of the most common major operative procedures performed worldwide. In the USA a CS rate of 26% for all births is reported.1 The rate approaches 25% in Canada and is over 20% in England, Wales and Northern Ireland.2 In the private health sector in South Africa, one study noted a much higher figure of 57%.3
Childbirth is an emotional experience for a woman and her family. The mother needs to bond with the new baby as early as possible and initiate early breastfeeding, which helps to contract the uterus and accelerates the process of uterine involution in the postpartum period.4 Any form of intervention that leads to improvement in pain relief can positively impact on early breastfeeding. Prompt and adequate postoperative pain relief is therefore an important component of caesarean delivery that can make the period immediately after the operation less uncomfortable and more emotionally gratifying.
Postoperative pain after CS is usually managed with opioids in combination with other forms of analgesics.
CS is performed under spinal anaesthesia, spinal epidural, epidural block or general anaesthesia. Short- or medium acting sedatives, narcotics and local anaesthesia have been employed during the operation as an adjunct to anaesthesia or to alleviate postoperative pain. Local anaesthetics cause reversible blockade of impulse propagation along the nerve fibres by preventing the influx of sodium ions through the cell membrane of the fibres. Several studies have reported on use of pre-emptive local anaesthetics (local anaesthetic given during the operation to prevent or reduce pain afterwards) to relieve postoperative pain, with results ranging from being beneficial5,6 to conferring no benefit.7,8
The local anaesthetic may be administered by pre- or postincisional abdominal nerve block (local anaesthetic injected to block the nerves before cutting the skin at the beginning of the operation, or after closing the skin at the end9) or pre- or post-incisional abdominal wound infiltration.5,10 It may also be administered by continuous wound irrigation.11 Commonly used local anaesthetic agents have side-effects, although these are very rare, ranging from allergy to cardiovascular and central nervous system effects. Local anaesthetics eventually get absorbed systemically and secreted in breastmilk, but their effects on breastfed babies have not yet been documented. This is in sharp contrast to morphine or pethidine, both of which have significant transfer to breastmilk and may have a sedative effect on the baby.4
It is also important to consider the cost implications of local anaesthetic administration. Should it prove to be of benefit, the actual cost of the local anaesthetic and the additional time needed to carry out the procedure may be justified, considering the long-term sequelae of pain and immobility immediately after CS.
The objectives of the study were to assess the effects of local anaesthetic agent wound infiltration/irrigation and/or abdominal nerve blocks on pain relief after CS, on the mother's physical, social and mental well-being, and on her ability to meet the physical, psychological and nutritional needs of the baby.
Prospective randomised controlled trials in women undergoing CS, either electively or as an emergency, were considered for inclusion in the review.
The types of interventions that were sought were local anaesthetic agent wound infiltration versus placebo/no infiltration, ilio-inguinal/iliohypogastric nerve block versus placebo/no treatment, local anaesthetic agent versus other methods of pain relief, and comparisons of different local anaesthetic agent techniques. Outcome measures assessed included postoperative pain scores, postoperative analgesia requirement, time to first rescue analgesia, postoperative fever, duration of CS, onset of mobilisation, onset of breastfeeding, duration of breastfeeding, duration of exclusive breastfeeding, side-effects of the local anaesthetic, duration of hospital stay, postoperative wound infection, women's satisfaction with regard to pain relief, occurrence of postnatal depression or neurotic/psychotic disorders, chronic pelvic pain, and caregiver satisfaction.
Studies were searched for and identified through the Cochrane Pregnancy and Childbirth Group's Trials Register by contacting the Trials Search Co-ordinator (April 2009). Details of the search strategies for CENTRAL and MEDLINE, the list of hand-searched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the 'Specialized Register' section in the editorial information about the Cochrane Pregnancy and Childbirth Group.12 There was no language restriction. We assessed for inclusion all potential studies we identified via the search strategy, and designed a form to extract data. No major discrepancies were identified. We used the Review Manager software13 to double-enter all the data, assessed the validity of each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions,14 and described methods used for generation of the randomisation sequence for each trial.
For each individual study we described the method used to generate allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups. We assessed the method as either adequate (any truly random process, e.g. random number table; computer random number generator), inadequate (any non-random process, e.g. odd or even date of birth; hospital or clinic record number), or unclear. Method of allocation concealment (checking for possible selection bias), blinding, completeness of data and selective reporting bias were all assessed.
We carried out statistical analysis using the Review Manager software.13 We used fixed-effect meta-analysis for combining data in the absence of significant heterogeneity if trials were sufficiently similar. When heterogeneity was found, we used random-effects analysis. For dichotomous data, we presented results as summary risk ratios (RRs) with 95% confidence intervals (CIs), and for continuous data we used the mean difference if outcomes were measured in the same way between trials. We used the standardised mean difference to combine trials that measured the same outcome but used different methods.
We applied tests of heterogeneity between trials, if appropriate, using the I2 statistic. In the event of significant heterogeneity, we used a random-effects meta-analysis as an overall summary if we determined that this was appropriate. Subgroup analysis was for women who had general anaesthesia versus regional analgesia. We excluded studies of poor quality (those rating B, C or D) in order to assess for any substantive difference to the overall result.
We identified 40 studies. Twenty studies, involving 1 150 women, carried out in both developed and developing countries and spanning almost two decades, met the inclusion criteria (Table I). The outcome of interventions is shown in Table II.
Wound infiltration with local anaesthetics only v. control
Women who underwent CS under regional anaesthesia and had wound infiltration had a decrease in morphine consumption at 24 hours (3 studies, 126 participants; standardised mean difference (SMD) -1.70 mg; 95% CI -2.75 to -0.94) compared with placebo. There was no difference in visual analogue pain.
Peritoneal spraying/instillation and abdominal wound infiltration involving all layers
Women who underwent CS under general anaesthetic, who had the wound infiltrated and peritoneal spraying with local anaesthetic (1 study, 100 participants), had a reduced need for opioid rescue (RR 0.51; 95% CI 0.38 to 0.69). The numerical pain score (0 - 10) within the first hour was reduced (MD -1.46 mg; 95% CI -2.60 to -0.32).
The amount of oral Tramacet (375 mg paracetamol + 150 mg tramadol) consumed was reduced in the local anaesthetic group compared with controls who received saline (MD -2.35 mg; 95% CI -3.62 to -1.08).
Local anaesthetic v. local anaesthetic and nonsteroidal anti-inflammatory drug (NSAID) mixture
Women operated on under regional anaesthesia and who had a local anaesthetic and NSAID cocktail wound infiltration consumed less morphine in the first 18 hours (1 study, 60 participants; MD -7.40 mg; 95% CI -9.58 to -5.22) compared with controls who received a local anaesthetic only. There was no difference in the occurrence of vomiting or reduction in anti-emetic use (RR 1.40 mg; 95% CI 0.90 to 2.16).
Anterior abdominal nerve block with local anaesthetic v. control
Women who had regional anaesthesia and an abdominal nerve block had decreased opioid consumption (4 studies, 175 participants; MD -25.80 mg; 95% CI -50.39 to -5.37) but no difference in visual analogue pain score (0 - 10) (2 studies, 83 participants; MD -1.82 (95% CI -2.74 to -0.90)).
Local anaesthetics v. local anaesthetics + narcotics
In terms of the visual analogue scale over 24 hours, no advantage was demonstrated in the single study of 50 participants who had wound infiltration with a mixture of local anaesthetic and narcotics versus local anaesthetic.
Local anaesthetics v. local anaesthetics + ketamine
Addition of ketamine to the local anaesthetic in women receiving regional anaesthesia does not confer any advantage in terms of narcotic consumption or patient satisfaction (1 study, 50 participants).
Minimising pain after CS is best achieved using a multimodal approach. Local anaesthetics, from lidocaine to the more recent ropivacaine, have been used as pre-emptive analgesics since the 1980s. Clinical trials were only published in the early 1990s. Local anaesthetic has been used in women receiving general anaesthesia and regional anaesthesia, and rarely local anaesthesia alone has been used when other anaesthesia was unavailable or unsafe. Various routes of administration have been tested, such as subcutaneous wound infiltration, infiltration through all layers of the abdomen, continuous wound instillation or iliohypogastric/ilio-inguinal nerve blocks. Ultrasound-guided nerve blocks may soon be explored. Local anaesthesia has been used alone and in combination with NSAIDs or ketamine.
This review showed that women undergoing CS under regional analgesia who had local anaesthetic infiltration or abdominal nerve block had a reduced need for postoperative opioids. Addition of NSAIDs to the local anaesthetic for wound infiltration conferred additional advantage, perhaps because these analgesics have a different mode of action. Opioid consumption may not be the optimal method of pain assessment because of being influenced by patient fear of dependency, but this effect is balanced by the randomisation process. Significant results must be regarded with caution because of testing at multiple times, and the results are mostly based on single trials involving few women. None of the trials addressed chronic pelvic pain or cost implications.
In general, we conclude that local anaesthesia is of benefit in women having a CS because it reduces opioid consumption. It can be recommended as part of the multimodal approach to pain relief, but in terms of affordability a cost-benefit analysis is needed as theatre time will be increased and there is a cost attached to the local anaesthetic and accessories. This cost increase may be offset by less use of postoperative analgesia. A pharmacokinetic study of local anaesthetic absorption after wound and peritoneal infiltration is necessary. Ultrasoundguided direct block of the anterior abdominal wall nerves in CS should be explored. An important field of investigation will also be the effect of the intervention on chronic pelvic pain.
The authors acknowledge support from the Postgraduate School and Effective Health Care Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, and University of Fort Hare, East London.
After a pre-publication editorial process by the Cochrane Pregnancy and Childbirth Group, the review was published in its full format in the Cochrane Library.31
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Accepted 28 September 2009.
Corresponding author: A A Bamigboye (email@example.com)