Abstract
Labour analgesia is a crucial aspect of obstetric anaesthesia, aiming to alleviate pain during childbirth while ensuring maternal and foetal safety. Over the past decade, advancements in labour analgesia techniques have evolved, impacting initiation, maintenance, and outcomes. We emphasize the longstanding importance of epidural analgesia while recognizing the growing significance of combined spinal-epidural and dural puncture epidural techniques for labour initiation. Analgesia maintenance is optimally achieved with an epidural bolus regimen, either manual boluses, programmed intermittent boluses or patient-controlled epidural analgesia. Utilizing high-volume, low-dose combinations of local anaesthetics with lipophilic opioids demonstrates synergistic effects, facilitating dose reduction and minimising adverse effects. Adjuvants can play a role in specific clinical contexts. The increasing significance of ultrasound guidance for procedural precision is highlighted. The intricate nature of labour pain management underscores the importance of both patient and clinician involvement in decision-making processes. Future advancements in this field have the potential to enhance the well-being of women as well as their newborns.
1
Introduction
Labour pain during childbirth represents one of the most intense forms of pain endured by women, making satisfactory analgesia a fundamental human right as advocated by guidelines set forth by the World Health Organisation (WHO) [ ]. Neuraxial techniques have consistently emerged as the gold standard in labour pain management, offering unparalleled efficacy compared to alternative modalities. Contemporary neuraxial techniques not only ensure effective pain relief but also uphold excellent safety profiles for both mother and child. While alternatives such as nitrous oxide and systemic opioids exist, they are often utilised as substitutes for neuraxial analgesia or in scenarios where neuraxial techniques are contraindicated [ , ]. Although additional non-pharmacological methods, including relaxation and breathing techniques, are available, they fall beyond the scope of this review. Recognizing the multifaceted nature of the labour experience, a comprehensive approach to pain management is needed, considering factors beyond mere pain intensity [ ]. Therefore, open communication between patients and healthcare providers is paramount in order to adequately discuss risks, benefits, and alternatives of labour analgesia and ensure personalised care that addresses all aspects of childbirth.
2
Initiation of neuraxial labour analgesia
Initiation of neuraxial labour analgesia can be achieved by using various techniques. The most frequently used methods include conventional epidural, combined spinal-epidural (CSE), and dural puncture epidural (DPE) [ ]. Other approaches, such as single-shot spinal, continuous spinal infusion, or caudal block, are not routinely utilized anymore and will not be further discussed.
For a conventional labour epidural technique, a 16–18 G hollow bevelled-tip epidural needle (such as Tuohy, Weiss, or Hustead) is carefully placed at the L3-L4 or L4-L5 intervertebral space. The epidural space is identified using the loss of resistance (LOR) technique, in which either saline or air is used to detect the passage through the ligamentum flavum, indicating entry into the epidural space. The choice of saline over air is often favoured due to its potential to mitigate adverse effects, such as a decreased incidence of postdural puncture headache (PDPH) and lower likelihood of uneven block distribution [ ]. Following successful identification of the epidural space, a catheter is carefully threaded through the needle and positioned within the epidural space before retracting the needle. Subsequently, the catheter is withdrawn slightly to ensure it remains positioned 3–5 cm within the epidural space. An aspiration test for cerebrospinal fluid (CSF) or blood is then performed using a 2 mL syringe, to confirm proper catheter placement, after which the catheter is fixed in place. Following these procedural steps, the patient is positioned supine with left lateral tilt. Administration of first epidural bolus follows to initiate analgesia ( Fig. 1 ).
For the combined spinal-epidural (CSE) technique, the identification of the epidural space is identified as described. Once the epidural space is successfully located and prior to threading the epidural catheter, a 25 to 29 G spinal pencil point needle (such as Whitacre or Sprotte) is carefully inserted through the epidural needle and advanced into the subarachnoid space to administer a single dose of medication. Following the intrathecal administration, an epidural catheter is carefully threaded into the epidural space via the epidural needle. Notably, there is a deliberate delay in the administration of the first epidural bolus, as the pharmacological effects of the spinal component manifest ( Fig. 2 ).
Dural puncture epidural (DPE) represents a modification of the CSE technique. For the DPE technique, the epidural space is identified and a 25 to 29-gauge pencil-point spinal needle is inserted through the epidural needle as with a CSE technique. No intrathecal dose is administered for the DPE. Instead, a small aperture is created, then the epidural catheter is threaded through the epidural needle and left in place ( Fig. 3 ).
2.1
Choice in technique
The lumbar epidural technique is widely utilised in high-income countries and endorsed by the WHO [ ]. However, the CSE technique is increasingly favoured for its rapid onset of profound pain relief, particularly during advanced stages of labour [ ]. This method typically achieves analgesia within 2–10 min, compared to the 15–20 min required by traditional epidural analgesia [ , ]. Moreover, interpatient variability in onset time is small with the CSE technique, whilst it is much larger with conventional epidural analgesia. Furthermore, CSE offers more uniform sensory blockade and enhanced coverage of the sacral dermatomes [ , ]. While some studies suggest increased maternal satisfaction because of more sense of control with CSE, meta-analyses do not consistently support these findings [ ]. Experts have raised concerns regarding the delayed confirmation of correct epidural catheter placement following CSE analgesia; however, evidence suggests that CSE technique is less prone to failure, potentially due to improved confirmation of midline needle placement in the epidural space through CSF visualisation [ , ]. A large cohort study by Booth et al. in 2016 showed that CSE technique had a significantly lower risk of overall epidural catheter failures than the epidural technique, without delaying the recognition of epidural catheter failure [ ]. The CSE technique may also lower the incidence of unilateral anaesthesia compared to the epidural technique [ ]. Nevertheless, CSE is associated with maternal hypotension, opioid-induced pruritus, and foetal heart rate changes [ , ]. DPE analgesia offers a promising alternative. This technique facilitates quicker analgesic onset and better sacral spread than the epidural technique while potentially reducing side effects associated with CSE [ ]. DPE analgesia may be suitable for patients with suspected difficult airways or failed epidural labour analgesia, enabling confirmation of proximity to the dura with the dural puncture and spinal fluid return, but not eliciting adverse effects associated with CSE dosing [ ]. Concerns about postdural puncture headache (PDPH) associated with creating a hole in the dura have led to hesitancy in some to use either the CSE or DPE techniques. However, such concerns may not be well-founded, as evidenced by a study in nearly 20,000 women conducted in 2004 by Pan et al. They found that CSE or epidural technique had a similar need for an epidural blood patch [ ]. While we can infer that a similar safety profile will exist for the DPE technique, optimal protocols for the DPE technique remain elusive and warrant further research [ , ]. Table 1 gives an overview of the different initiation techniques.
| Parameter | Epidural | Combined-spinal epidural | Dural puncture epidural |
|---|---|---|---|
| Quality of labour analgesia | |||
| – Onset time of analgesia (min) | 10-25, higher interpatient variability | 4-10, lower interpatient variability | Intermediate between epidural and CSE |
| – Lowest visual analogue scale scores (mm) | 0-30, more variability | 0-10, less variability | / |
| – Maternal satisfaction | Higher due to fast onset of analgesia and more symmetrical blocks | Higher due to more symmetrical blocks | |
| – Breakthrough pain | More frequent | Less frequent | Less frequent |
| – Reliability of the epidural catheter | Less reliable | More reliable | More reliable |
| – Duration of initial analgesia (min) | 90–150 | Similar to epidural | Similar to epidural |
| – Local anaesthetic consumption | 20–30% higher than CSE | 20–30% lower than epidural | / |
| Side effects | |||
| – Pruritus, with neuraxial opioids | Less frequent | More frequent, but mild | Less frequent |
| – Nausea | Yes, but rare | Yes, but rare | Yes, but rare |
| – Hypotension | Mild, later onset | Mild, earlier onset | Mild, less than CSE |
| – Respiratory depression | Rare | Rare | Rare |
| – Motor block | Higher rate, more pronounced | Lower rate, less pronounced | Lower rate |
| – Foetal heart rate changes | Less, because of the absence of intrathecal opioids and slower onset of analgesia | More, most case with high dose intrathecal opioids and more rapid onset of analgesia | Less than CSE |
| – Post dural puncture headache | <1% | <1% | <1% |
| – Neurological deficit (i.d. trauma to the cord) | Rare | Rare, but increased risk if lumbar interspace above L3-L4 is used | Rare, but increased risk if lumbar interspace above L3-L4 is used |
| – Infection (e.g. meningitis) | No difference | No difference, but theoretically higher risk | / |
| Manual bolus (when compared to infusion pumps) | CEI (when compared to manual bolus) | PCEA + CEI (when compared to CEI alone) | PIEB + PCEA (when compared to PCEA + CEI) | |
|---|---|---|---|---|
| Advantages | – Safer as mispositioning could be noticed with pain on infusion | – Improved safety profile – Improved quality of analgesia – Less breakthrough pain | – Improved analgesia consistency – Less motor block – Less need for intervention | – Less breakthrough pain – Less consumption of LA – Less motor block – Less need for intervention |
| Disadvantages | – Labour intensive – Frequent breakthrough pain | – Increased motor block – Less patient contact | – Increased instrumental vaginal deliveries – Risk for unrecognized high neuroblockade (after migration of the epidural catheter to the intrathecal space) | – Increased risk for unrecognized high neuroblockade |
2.2
Choice in local anaesthetic: drug, concentration, and dose
There are three clinically relevant local anaesthetics: bupivacaine, levobupivacaine and ropivacaine. The primary mechanism of action for all three is the blockade of voltage-gated sodium channels. Key properties determining onset time and duration include ionisation constant, lipophilicity, and degree of protein binding. Potency is closely linked to lipid solubility, with more lipid-soluble compounds easily permeating neuronal membranes. Studies indicate a correlation between potency and neurotoxicity, with equipotent local anaesthetic doses inducing equitoxic effects [ ]. Bupivacaine remains the most popular worldwide, although ropivacaine and levobupivacaine have been recognised for potential lower systemic toxicity and lower risk of motor block [ , , , ].
Traditionally, epidural solutions for labour analgesia employed highly concentrated local anaesthetic solutions, which often resulted in increased motor blockade and reduced maternal satisfaction. However, the shift towards more dilute local solutions has yielded promising outcomes. Studies have consistently shown that using lower concentrations of local anaesthetics is associated with a lower incidence of assisted vaginal deliveries, less motor block, greater ambulation, and a shorter second stage of labour compared to high concentration solutions [ ]. This reduction in motor block while maintaining effective analgesic levels enhances motor function, and may facilitate more effective pushing and patient engagement in the second stage of labour. Several studies have demonstrated comparable analgesic efficacy with lower concentrations of local anaesthetics, allowing for further dose reduction without compromising labour analgesia. For instance, in a study by Lyons et al., bupivacaine at 0.125% concentration was compared to 0.25%, revealing equivalent analgesia with a 50% increase in volume and a 25% reduction in dose. Such studies have enabled modification of labour epidural dosing to reduce the risk of toxicity, improve safety profiles, and increase patient satisfaction [ ].
2.3
Choice in adjuvant
2.3.1
Opioid adjuvant
Neuraxial opioids play a crucial role in labour analgesia, exhibiting a synergistic effect when combined with local anaesthetic. This combination enhances analgesic effects, allowing a reduction in local anaesthetic dosing and consequently lowering the risk of systemic toxicity [ , ]. The addition of a lipophilic opioid such as fentanyl or sufentanil has shown promise, potentially reducing the local anaesthetic requirements by up to four-fold [ ]. This combined approach not only minimises the required dose for each agent, thus limiting toxicity, but also extends the duration of analgesic effects, diminishes motor block, and enhances patient satisfaction when compared to the use of local anaesthetic alone [ ]. As pointed out by a multicentre study by Gogarten et al., quality of analgesia of ropivacaine 0.175% combined with sufentanil is superior compared to ropivacaine 0.2% alone, with lower local anaesthetic consumption and less motor block observed [ ]. Extensive evidence supports the use of high-volume, low-concentration dosing of local anaesthetic in combination with a lipophilic opioid for epidural labour analgesia. This approach ensures comprehensive coverage from Th10 to S3 with less motor block and better labour outcomes [ ]. Termed low-dose epidural analgesia, this method has gained popularity in the past two decades, aiming to optimise pain relief while minimising side effects [ , ]. Meta-analyses endorse the use of low-concentration local anaesthetic solutions, such as ≤0.1–0.15% bupivacaine, which pose no increased risk of assisted vaginal delivery compared to non-epidural analgesia [ , ]. As advocated by the American Society of Anesthesiologists (ASA) guidelines, it is now standard practice to use dilute concentrations of local anaesthetics with lipophilic opioids to achieve minimal motor block. Typically, this involves the administration of 1–3 μg/mL fentanyl or 0.5–1 μg/mL sufentanil. For intrathecal dosing, recommended amounts are 10–25 μg fentanyl or 2–5 μg sufentanil [ ].
2.3.2
Non-opioid adjuvants
- 1.
Clonidine and dexmedetomidine
Both α 2 -receptors agonists exert their analgesic effects through the α 2 -receptors located in the spinal cord. While research on dexmedetomidine is limited, clonidine has been extensively investigated for neuraxial administration. Intrathecal clonidine dosing ranges from 15 to 45 μg, with a study from Missant et al. demonstrating the potential for stronger and prolonged analgesia, although with a trade-off of significant refractory hypotension [ ]. Most interestingly, both oral and intravenous administration of clonidine and dexmedetomidine have been found to prolong the anaesthetic effect of intrathecal local anaesthetics [ , ]. For epidural administration doses of 30–150 μg have shown a good analgesic effect. However, doses of 75 μg and higher may lead to sedation, hypotension, and bradycardia, and alterations in foetal heart rhythm. This necessitates adequate hemodynamic monitoring and warrants reserved use in selected cases, such as for treating breakthrough pain, rather than as a standard practice [ , ].
- 2.
Epinephrine
Epinephrine also acts through α 2 -receptors, although vasoconstrictive effects might be involved as well. It can contribute to epidural administration by significantly reducing the minimum local analgesic concentration (MLAC) of bupivacaine, thereby improving quality of analgesia. However, this advantage comes with the increased incidence maternal motor deficit, possible prolongation of labour duration, and the need for pre-prepared solutions, complicating storage and raising drug prices [ ]. A systematic review of epinephrine for intrathecal analgesia showed a prolongation of analgesia and motor block by 60 min, but its beneficial effect in the context of labour epidural analgesia remains uncertain [ ].
- 3.
Neostigmine
Neostigmine exhibits its effect as an indirect parasympathomimetic by inhibiting cholinesterase, thereby prolonging and enhancing the effect of acetylcholine on muscarinic and nicotinic receptors. While it can be administered intrathecally or epidurally with good analgesic effect, it is associated with severe nausea and vomiting which precludes recommendation for its routine use [ , ].
- 4.
Others
Other medications such as dexamethasone, midazolam, ketamine, and magnesium sulphate have not been sufficiently investigated for neuraxial administration in well-founded studies to date. Consequently, routine use is not recommended [ ].
3
Ultrasound-guided techniques for neuraxial anaesthesia
Traditional palpation of bony landmarks is the most common method for determining the site for epidural insertion, but it can pose challenges, particularly in patients with obesity, scoliosis, or a history of spine surgery. Studies have shown that correct interspace identification is achieved in only 29% of cases, with many placements being higher than predicted, thereby increasing the risk of neurological injury [ ]. This challenge is further compounded in obstetric patients due to the effect of a gravid uterus, which pulls the lower spine forward limiting lumbar flexion and enhancing lordosis. Such downward traction by the gravid uterus may alter typical vertebral process localisation relative to the iliac crests, rendering Tuffier’s line (an imaginary line drawn between iliac crests that usually falls at the L4 lumbar vertebra or L4-L5 interspace) a less reliable anatomical landmark at term gestation. Preprocedural ultrasound has emerged as a valuable tool for identifying specific intervertebral spaces and determining the depth of epidural and intrathecal spaces. Several meta-analyses have investigated its use, demonstrating a reduction in procedural failure and needle passes, particularly for obstetric epidurals and CSE. Provided the operator is well-trained, ultrasound guidance has also been associated with improved first-pass success rates and reduced incidence of vascular puncture. Additionally, it reduces the risk of failed epidural and traumatic insertion, as well as the need for catheter replacement for operative delivery during labour analgesia [ ]. Guidelines from the National Institute for Health and Care Excellence (NICE) have endorsed the use of pre-procedural ultrasound in this context since 2008 [ ]. Ultrasound is increasingly being used as a rescue method when a patient with difficult anatomy is encountered [ ].
4
Maintenance of neuraxial labour analgesia
Strategies for maintenance of labour epidural analgesia aim to optimise pain relief while minimising adverse effects and complications. Historically, anaesthesiologists or midwives administered manual boluses of local anaesthetic through the epidural catheter as needed, which was labour-intensive. The evolution of continuous epidural infusions (CEI) using automated pumps limited the need for intermittent top-ups, reducing clinician workload substantially. However, the use of CEI alone resulted in a high rate of motor block. This phenomenon can be explained by the pharmacodynamics of nerve blocks, where continuous infusion in the extraneural space establishes a diffusion gradient, leading to an equilibrium between intraneural and extraneural concentrations and subsequent blockade of both sensory and motor nerve fibers [ ]. Patient-controlled epidural analgesia (PCEA) pumps gained popularity in the late eighties, allowing women to self-administer medication boluses. The combination of PCEA with CEI as a background infusion improved analgesia consistency, but increased the risk of anaesthetic consumption and the risk of instrumental vaginal delivery [ , ]. Since the early 2000s, programmed intermittent epidural bolus (PIEB) has been utilised to achieve a wider sensory block and better homogeneous distribution, often in conjunction with CEI or PCEA [ ]. Emerging techniques such as computer-integrated PCEA (CIPCEA) allow for adaptive maintenance based on usage patterns, providing flexible analgesia adjustments over time. Research in this area remains limited. Table 2 presents a chronological overview of the improvements and side effects associated with maintenance techniques.
4.1
Choice in technique
When comparing these maintenance techniques, factors such as analgesia quality and side effects must be considered. Studies comparing CEI alone to PCEA with a background CEI demonstrated reduced total local anaesthetic doses, motor block, and need for intervention, along with improved pain relief and patient satisfaction [ ]. Combining PCEA with CEI has been a preferred option in many countries for this reason [ ]. Wong et al. investigated the combination of CEI and PCEA versus PIEB and PCEA. Their PIEB regiment showed a reduction in total local anaesthetic consumption, improved maternal satisfaction, decreased the need for intervention with top-ups, decreased maternal motor blockade and decreased instrumental vaginal deliveries [ ]. Meta-analysis demonstrates reduced local anaesthetic usage and improved maternal satisfaction with PIEB, as well as potentially lower instrumental delivery rates and less frequent need for intervention with top-ups with PIEB compared to CEI [ ]. A quality improvement study by McKenzie et al., in 2016, changing their regimen from CEI and PCEA to PIEB and PCEA, demonstrated a reduced need for intervention, less incidence of unilateral sensory blockade, and lower peak pain scores [ ].
Further studies have been done to optimise the regimen for PIEB + PCEA. Li et al. found that a higher volume of 10 ml every hour for PCEA provided superior analgesia compared to 5 mL every half hour [ ]. A systematic review compared different doses and intervals for PIEB to find that PIEBs of 5 mL every 30 min or 10 mL every 60 min were optimal to decrease cumulative dose requirement, 5 mL every 30 min yielded lowest pain scores, and 10 mL every 60 min was best for minimising the need for rescue analgesia [ ].
The rate of bolus delivery seems to impact effectiveness, with high velocity injections being favourable [ ], although this may increase the risk of hypotension and motor block [ , ].
Ultimately, the optimal dosing regimen and pump infusion settings for PIEB with PCEA remain uncertain. Individualised approaches are necessary, with the PIEB establishing a baseline level of analgesia for every patient, and the PCEA allowing each patient to individualise additional dosing for breakthrough labour pain. Variability in pain perception, labour stage, and individual preferences must be considered. Further research is needed to evaluate medication solutions, concentrations, dosage, timing interval, and the lockout times to develop an ideal maintenance regimen tailored to each patient’s needs.
5
Summary
The evolution of obstetric analgesia over the past fifty years marks a significant milestone in improving efficiency and safety. Contemporary neuraxial analgesia incorporates a combination of local anaesthetics, lipophilic opioids, and other adjuvants, characterized by a low concentration (<0.125% or less) and a high volume. The use of an initial spinal dosage offers distinct advantages in specific clinical indications. Maintenance of analgesia through an epidural catheter, with protocols such as PCEA and PIEB, further enhances patient comfort and satisfaction.
Practice points
- –
Neuraxial techniques, particularly combined spinal-epidural (CSE) analgesia, are preferred due to their rapid onset of analgesia and efficacy.
- –
While not routinely adopted, dural puncture epidural (DPE) offers some benefits of epidural and other benefits of CSE initiation strategies.
- –
The use of low-concentration, high-volume local anaesthetics combined with lipophilic opioids is essential for optimising labour analgesia.
- –
For maintenance of labour analgesia, the programmed intermittent epidural bolus (PIEB) technique confers benefit compared to CEI for lower analgesic requirement and less need for top-ups.
Research agenda
- –
Investigate the role and efficacy of dural puncture epidural (DPE) in various clinical scenarios to determine its optimal application.
- –
Explore different regimens for programmed intermittent epidural bolus (PIEB) administration to identify the most effective and safest approach.
- –
Evaluate potential variations in programmed intermittent epidural bolus (PIEB) effectiveness based on the method of initiation to optimise labour pain management strategies.
- –
Investigate the feasibility and benefits of utilizing smart pumps in administering epidural analgesia to enhance safety and efficiency.
During the preparation of this work the author(s) used ChatGPT in order to improve language and readability. After using this tool/service, the author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the publication.
CRediT authorship contribution statement
Marie-Camille Vanderheeren: Writing – original draft, Visualization, Project administration, Methodology, Investigation, Formal analysis, Data curation. Marc Van de Velde: Validation, Supervision, Conceptualization. Eva Roofthooft: Supervision.
Declaration of competing interest
None.
Acknowledgements
None.
References
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