30 Felicity Plaat Queen Charlotte’s & Chelsea Hospital, Imperial College Healthcare NHS Trust, London, UK In consultant‐led units more than 70% of obstetric patients require anaesthetic input. This includes labour analgesia, anaesthesia for caesarean delivery and other surgical interventions, input into management of patients requiring critical care, and resuscitation. Because the role of the anaesthetist has expanded, current guidelines suggest that as a minimum there should be dedicated consultant anaesthetic input during the working week, and that elective obstetric work should be separately staffed [1]. The International Association for the Study of Pain defines pain as ‘an unpleasant, subjective, sensory and emotional experience associated with real or potential tissue damage, or described in terms of such damage’. In simple terms, pain is what hurts. More than 95% of women report pain of varying intensity in labour. Melzack [2] measured pain in parturients using the McGill Pain Questionnaire and showed that although scores ranged from mild to excruciating, only pain associated with digit amputation and causalgia was equal to or greater than labour pain, which outscored cancer, post‐herpetic neuralgia and pain of fracture. Although pain may be considered the physiological consequence of normal labour, it may also be the harbinger of pathological processes, such as obstructed labour, fetal malposition, uterine hyperstimulation, uterine rupture or extant pathology such as fibromas or other tumours, haemorrhoids, and adhesions or scarring from previous surgery. Severe pain stimulates a sympathetic autonomic response the magnitude of which reflects the severity of pain, and is exacerbated by dehydration and exhaustion. It is characterized by hyperventilation, tachycardia, hypertension, increased oxygen and glucose consumption, and vasoconstriction with decreased blood flow across the placenta. Maternal plasma adrenaline and noradrenaline concentrations increase 200% and 600%, respectively, during labour without analgesia. Increased maternal catecholamine levels can be associated with dysfunctional labour [3]. In the presence of maternal disease and/or fetal compromise, such effects are undesirable and under some circumstances may even be life‐threatening. Non‐pharmacological methods of pain relief include antenatal education, aromatherapy, hypnotherapy (‘hypno‐birthing’), acupuncture, water injection, water immersion, massage and other relaxation techniques (this list is not exhaustive). A recent review suggests that continous support by a trained support person or ‘doula’ reduces analgesic requirements, shortens labour, increases satisfaction and improves outcome for the neonate. The effect is greatest if the support is provided by someone who is neither part of the woman’s social network nor part of the hospital staff. It is worth noting that the effect is greatest in units where neuraxial analgesia is not routinely available [4]. This bears out the clinical experience that neuraxial analgesia is often requested when one‐to‐one care is not available. The evidence for other techniques is generally of poor quality, although some, such as water immersion (birthing pools), are very popular and may reduce analgesia requirements. Entonox (50% N2O in oxygen) is widely used in the UK. Although 80% of women who use it would do so again, and there is evidence it is effective, it is associated with side effects such as nausea, vomiting and dizziness [5]. Although the use of sevoflurane and other inhalation anaesthetics has been studied, currently they are not part of mainstream clinical practice. Systemic opioids (pethidine and diamorphine) are almost universally available in birthing units in the UK, although evidence suggests that their effect is sedative [6] and that they have no analgesic effect in labour compared with placebo [5]. When offered this form of medication women should be informed of this. Diamorphine may be slightly more effective and may have less effect on the neonate than pethidine and is slowly replacing pethidine in some units in the UK. Patient‐controlled intravenous analgesia (PCA) is an alternative if regional analgesia is contraindicated. The ultrashort‐acting opioid remifentanil has theoretical advantages over other opioids owing to its short latency and rapid metabolism. However, respiratory depression occurs in over 30% of women and cases of hypoxic cardiac arrest have been reported. The evidence for analgesic efficacy is modest [7]. If remifentanil PCA is used for labour, pulse oximetry and the continuous presence of trained personnel is mandatory and it should only be used in units where staff are experienced in and regularly care for women with this type of analgesia [1]. There is no question that neuraxial blockade (epidural or intrathecal) provides the most effective form of pain relief in labour, and very few women cannot benefit from this form of analgesia (Table 30.1). Based on data from 70% of obstetric units in the UK in 2011, the Obstetric Anaesthetists’ Association (www.oaa‐anaes.ac.uk) estimated that the average regional analgesia rate in 2007 was 22.7%, although this varied in units that offered the service from 4.1 to 37.6%. Modern regional techniques aim to provide pain relief whilst preserving sensation, minimizing motor blockade (muscle weakness) and reducing the effects on labour. The basis for achieving this is to reduce the dose of local anaesthetic used. Such techniques are frequently referred to as ‘low‐dose’ or ‘mobile’ epidurals. In 2008, 80% of UK units were using low‐dose techniques [8]. Guidance from the National Institute for Health and Care Excellence (NICE) published in 2014 states categorically that low‐dose regimens should be used for the initiation and maintainence of analgesia [9]. Methods for reducing local anaesthetic consumption include combining the local anaesthetic with an opioid to achieve a synergistic effect (commonly fentanyl), avoiding conventional test doses (usually high concentrations of local anaesthetics) and using a combined spinal–epidural technique. The latter involves injection of the initial dose into the intrathecal space (a spinal injection) prior to placing an epidural catheter. The intrathecal dose requires one‐tenth of the amount of local anaesthetic to be effective and provides almost instantaneous pain relief. The combined spinal–epidural technique is therefore particularly useful in the later stages of labour and in multiparous women in whom rapid labour is anticipated. It may also provide more reliable analgesia throughout labour and the use of combined spinal–epidural analgesia for labour is growing (Table 30.2) [10]. Table 30.1 Contraindications to regional analgesia. Table 30.2 Single‐shot spinal, combined spinal–epidural and epidural techniques. Source: Paech M. Newer techniques of labor analgesia. Anesthesiol Clin North Am 2003;21:1–17. Reproduced with permission of Elsevier. * Single‐shot spinal anaesthesia dose is two to three times subarachnoid dose of combined spinal–epidural. † These side effects are dose‐dependent with epidural and combined spinal–epidural techniques. High ranges associated with full anaesthesia doses. There is growing evidence that the effects of regional analgesia on the progress and outcome of labour are dose related. Systematic review of randomized controlled trials comparing regional and non‐regional (opioid) analgesia shows that regional analgesia does not increase the overall risk of caesarean delivery but may be associated with increased caesarean delivery for fetal distress [11]. The effect is the same whether started early or later in labour [12]. Regional analgesia prolongs the second stage of labour (by approximately 15 min) and increases the need for augmentation and the use of instrumental vaginal delivery [11,13]. Evidence from randomized controlled studies suggests that low‐dose neuraxial regimens are associated with fewer instrumental deliveries compared with conventional epidural analgesia [14]. Concerns about impaired maternal effort in the second stage of labour have resulted in the widespread habit of discontinuing regional analgesia in late labour [15]. However, a recent review concludes that in the absence of large trials the evidence suggests that all this achieves is poor analgesia in the second stage of labour [16]. Neither is there any evidence to withhold neuraxial analgesia from women in the latent stage of labour [9]. Other side effects of regional analgesia include increased use of urinary catheterization, maternal fever (non‐infective and believed to be a result of the local anaesthetic) and pruritus due to neuraxial opioids. Ambulation in labour has not been shown to significantly affect the mode of delivery, However, mobility may decrease analgesic requirements and avoids the risks associated with prolonged recumbency. Mobilizing with regional anaesthesia has been shown to be safe and is viewed positively by women who undertake it [17]. To permit safe ambulation, all delivery unit staff must be appropriately trained and certain conditions must be met (Table 30.3). Motor and proprioceptive block must be excluded. Studies have demonstarated that women themselves can reliably tell if they can ambulate safely [18]. Results are currently awaited from a study comparing upright and recumbent positions in the second stage of labour in nulliparous women with neuraxial analgesia (ISRCTN Registry 35706297). Table 30.3 Requirements for safe ‘mobile epidurals’ in labour.
Analgesia, Anaesthesia and Resuscitation
Pain
Non‐regional analgesia for labour
Regional analgesia
Absolute
Maternal refusal
Lack of personnel/facilities
Pre‐existing coagulopathy
Local infection at insertion site
Raised intracranial pressure (risk of coning)
Drug allergy
Relative
Haemodynamic instability
Anatomical abnormalities
Neurological disorders (medicolegal implications)
Systemic infection
Single‐shot spinal*
Epidural
Combined spinal–epidural
Onset of action (min)
Fast (1–5)
Slow (10–20)
Fast (1–5)
Median pain score 60–90 min
0
0–3
0
Total drugs dose
Low
High
Low
Observable leg weakness (%)†
100
5–50
0–40
Post‐dural puncture headache (%)
1–2
0.3–1.0
0.2–0.7
Hypotension (%)†
20–80
5–10
5–10
Failure (i.e. GA is required) (%)†
1.7–6.0
2–6
0.3–0.7
Pruritus (%)†
50–80
20–80
20–80
Duration (min)
60–240
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
