Planning, Preparation and Pre-emption are three key concepts in the practice of anaesthesia. In obstetric anaesthesia specifically, these three ‘P’s are particularly relevant as parturients are commonly present the Delivery Suite for a period of time prior to requesting or requiring anaesthetic intervention. One frequently encountered example of implementing Planning, Preparation and Pre-emption by the obstetric anaesthesiologist is the recommendation of starting epidural analgesia during labour. Unless contraindicated, this is suggested or advisable in parturients with modified WHO 3 and modified WHO 4 heart disease1, in women with maternal obesity2, in active COVID-19 infection3, in the presence of certain ophthalmic pathologies4, and in laboring women with pre-eclampsia5, among others. This is to ensure labour analgesia and patient comfort; to prevent deterioration of medical conditions due to the added physiological and psychological stresses of labour; to reduce the need for further anaesthetic intervention should anaesthesia be required for a surgical procedure; and to avoid general anaesthesia wherever possible, reducing the incidence of associated complications and protecting healthcare staff from aerosol-generating procedures.
The main benefits of having an established Labour Epidural providing good epidural analgesia are: 1) the possibility of its conversion to an epidural anaesthetic in the case of an emergency Caesarean section, 2) the avoidance of disadvantages associated with removing the Epidural and using a Spinal, and 3) other considerations including cost, environmental impact, anaesthetist workload, and patient perspectives.
1. Conversion to Epidural Anaesthesia for Emergency Caesarean Section
Lumbar epidurals are regarded as the gold standard for labour analgesia6. The Obstetric Anaesthetists’ Association (OAA) in the United Kingdom estimates that only 5% of labour epidurals will not work well enough for a Caesarean section7, should it be required. In an Irish study, the rate of labour epidurals converted to spinal or general anaesthesia for Caesarean section was 9%8, the conversion rate from an Indian study was approximately 4%9, a Maltese study identified a rate of epidural conversion to spinal or general anaesthesia for Caesarean section as 0.85% and 1.5% respectively10, a Chinese publication showed a conversion rate to general anaesthesia of 3%11, while a systematic review in 2022 by authors from the United Kingdom and the United States of America including over 3000 patients showed an overall prevalence of inadequate epidural anaesthesia of around 30%12. It is however worth noting that this systematic review relates to elective caesarean section, and not emergencies, with the possibility that epidural analgesia was not established for a significant period of time prior to the procedure.
Naturally, it is important to ensure that the epidural analgesia provided during labour is satisfactory to increase chances of success of epidural anaesthesia for emergency Caesarean section13. A number of risk factors have been identified as being associated with a failure of conversion from epidural analgesia to anaesthesia and recommendations for their mitigation14, in line with the spirit of Planning, Preparation and Pre-emption, have been made. The presence of an obstetric anaesthetist has also been mentioned as a relevant factor in this regard15.
Furthermore, the time required for an epidural top up to a level adequate for surgical anaesthesia compares favourably with that required for a spinal, and in some cases, even with that required for a general anaesthetic. A 2018 retrospective cohort study showed that unadjusted median operating room-to-incision intervals were 6 minutes for general anaesthesia, 11 minutes for epidural top-up, and 13 minutes for spinal anaesthesia16. It is important to point out that when relating to clinical significance, general anaesthesia was associated with worse short term neonatal outcomes in this study, and that longer time intervals were not associated with worse neonatal outcomes16. A 2007 retrospective audit from Australia showed mean decision-to-delivery times of 17 (±6) minutes for general anaesthesia, 19 (±9) minutes for epidural, and 26 (±9) minutes for spinal17. It has also been reported that established epidural analgesia may mitigate the increased anaesthesia and surgery time required in obese obstetric patients undergoing Caesarean section18.
Finally, epidural anaesthesia for emergency Caesarean section has the benefit of being topped up as often as required to prolong the duration of the anaesthetic block. It also allows for manipulation of the time of onset of the anaesthetic, speeding it up by using lignocaine together with adjuvants such as opiates, bicarbonate, or adrenaline; or even providing a gentle onset of neuraxial anaesthetic blockade when required, for example, in patients with severe heart disease. One-shot spinal anaesthesia does not confer these benefits.
Therefore, it can be said that in over 90% of cases where a functioning labour epidural analgesia is present, this can be satisfactorily used for emergency Caesarean section anaesthesia in a timely manner. This is very promising data which encourages the anaesthesiologist to utilize epidural top ups, instead of removing the labour epidural and attempting an alternative technique.
2. Disadvantages associated with removing the Epidural and using a Spinal
The decision to remove a labour epidural for an emergency Caesarean section and opt for a spinal anaesthetic has its disadvantages. Firstly, as described above, the anaesthesiologist is losing an anaesthetic option which has a high chance of success and is negating some benefits related to Planning, Preparation and Pre-emption in obstetric anaesthesia. Secondly, the patient is being exposed to the potential complications associated with a second procedure, which may not have been justifiably necessary. In this case, there is always the possibility that a spinal anaesthetic is not possible to site due to patient anatomy, difficulty with appropriate positioning in an emergency situation, challenges resulting from the volume already present in the epidural space, and psychological stress due to the urgency felt by the multidisciplinary team, among others. This would result in the anaesthesiologist having to resort to general anaesthesia, which may further expose the patient to complications such as awareness, aspiration, and difficulty with airway manoeuvres.
Additionally, there is controversy in the literature regarding the safety of spinal anaesthesia following pre-established epidural analgesia in obstetrics. A number of authors express concerns regarding the risk of high spinal or total spinal with the injection of local anaesthetic and adjuvants into the cerebrospinal fluid once this is already compressed by the contents of the epidural space14,19. This seems to be more of an issue if a recent epidural bolus would have just been administered, as compared to an epidural infusion only19–20. Case reports of these complications have been published21–22.
3. Other considerations
When considering the choice between topping up a labour epidural or removing it and using a spinal for emergency Caesarean section, one should also factor in the issues of cost, environmental impact, anaesthesiologist workload, and patient perspectives.
It can be argued that removing a labour epidural and performing spinal anaesthesia is more costly than topping up the already-present epidural. A new sterile gown and gloves will need to be used by the anaesthesiologist, together with the opening of a new sterile pack for spinal anaesthesia. This will include consumables, such as the spinal needle, the cleaning solution and swabs; as well as the cost of cleaning, decontamination, and sterilization of any reusable items, which involves the cost of additional staff. The repeated use of personal protective equipment, utilization of consumables, and processes associated with cleaning, decontamination, and sterilization also carries an environmental impact. In a world where cost-efficiency is key, and minimization of environmental impact is important, these considerations cannot be ignored.
Choosing to remove a labour epidural and use a spinal anaesthetic for an emergency Caesarean section may also have an effect on the anaesthesiologist in terms of stress and workload. Deciding to remove a working epidural analgesia catheter before even giving it a chance to work is eliminating a realistic anaesthetic option for an emergency procedure. This limits the tools available to the anaesthesiologist as it is not usually feasible for an epidural catheter to be re-inserted in an emergency. It also requires the anaesthesiologist to explain this additional procedure to the patient and gain informed consent in a challenging situation. This extra workload i.e., explaining, gaining informed consent, and inserting a spinal anaesthetic, may be stressful for the anaesthesiologist. Also, they are now required to perform a procedure in a time-pressured and high-stakes environment. Performance anxiety may also play a part if the anaesthesiologist is very keen to avoid a general anaesthetic, for example, if they feel the patient’s airway looks particularly difficult or the patient has pre-eclampsia and would therefore be at a higher risk of complications.
Patient perspectives should also be considered. The author has found no published literature specifically relating to patient preference regarding epidural or spinal anaesthesia for emergency Caesarean section. However, it is reasonable to think that a patient who has a working labour epidural already has confidence in the technique and as a result, may feel more reassured with epidural anaesthesia for emergency Caesarean section as compared to alternatives.
In summary, labour epidurals providing satisfactory analgesia should be considered for a top up to provide epidural anaesthesia for emergency Caesarean sections. In fact, this is one of the main benefits of siting labour epidurals in patients who are at a higher risk for Caesarean section and is a strong feature of obstetric anaesthesia practice using the principles of Planning, Preparation and Pre-emption. In addition, there are disadvantages to the alternative of removing the labour epidural and using a spinal anaesthetic. Furthermore, there are cost, environmental, anaesthesiologist, and patient considerations that may support the choice of epidural anaesthesia over spinal.
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