Difficult and Failed Intubation in Pregnancy
In this article Dr Georgia Knight, Obstetric Anaesthesia Fellow and Dr Mary C Mushambi, Consultant Obstetric Anaesthetist at University Hospitals of Leicester, UK and author of the OAA/DAS Obstetric Difficult Intubation Guidelines, explore how to manage the difficult or failed intubation on the labour ward.
This article is primarily aimed at care of the patient undergoing caesarean section, but many of the principles can be used for the obstetric patient undergoing non-obstetric surgery.
Airway management and failed intubation in the pregnant woman present many unique challenges which differ from the non-pregnant patient. Failed intubation occurs almost 10 times more frequently in the obstetric population than the non-obstetric population (~1 in 390 vs ~1 in 2000). Incidence of failed intubation at Caesarean section (CS) is approximately 2.3 per 100.000 general anaesthetics and if this occurs, the mortality increases to 1:901 .
The consequences of a failed intubation in the obstetric patient may not only impact on the patient themselves but also on the foetus; this can influence the choice of whether to proceed with surgery or not.
Anticipation and Prevention:
The following opportunities should be taken to prevent a failed intubation scenario:
- Women who are predicted or known to have difficult airways should be referred to an antenatal anaesthetic clinic to allow the opportunity for a thorough airway assessment and appropriate planning.
- Full airway assessments should be carried out to predict global airway management difficulty (including mask ventilation, supraglottic airway insertion, cricothyroidotomy and extubation) and not just laryngoscopy and intubation.
- Anaesthetists should ideally attend all delivery suite ward rounds, to make themselves aware of high risk patients and plan appropriately. Planning an early epidural in labour for the high risk patients and ensuring a reliable neuraxial block which can be topped up to provide anaesthesia is highly recommended.
- In patients who require a surgical intervention, the WHO checklist should be used to highlight concerns and make the airway plan known by all team members .
- There should be a low threshold to seek help from a senior colleague if a difficult airway is anticipated or encountered.
OAA/DAS Safe obstetric general anaesthetic algorithm
Planning and preparation
It is important to always have a plan of whether to wake the patient up or proceed with the operation should failed intubation occur. This decision depends on several factors outlined in Table 1 and it should be a shared decision with the obstetric team and communicated clearly with all members of the theatre team before induction of general anaesthesia.
Unless it is safe or necessary to proceed with surgery the patient should be woken up. Strong indications for waking the patient up include no foetal or maternal compromise, having an obstructed airway (identified by noisy breathing, an obstructed capnography trace, or hypoxaemia secondary to hypoventilation), complex surgery, anticipation of major haemorrhage, or if the patient is unfasted. If however, there is adequate ventilation, further intubation attempts are discouraged and continuing with surgery may be prudent particularly if there are other reasons to proceed with surgery such as maternal or fetal compromise, and failed neuraxial or awake intubation attempts previously. However, although the decision is influenced by factors in Table 1 which relate to the woman, foetus, staff and clinical situation, the exact combination will be unique in each individual situation.
The likelihood of intubation success should be maximised by appropriate preparation of the patient before induction, including:
- Optimisation of patient position: Head up position, with ramping pillows utilised for obese patients.
- Pre-oxygenation to an end-tidal oxygen concentration of 0.9. Nasal cannulae are recommended for the administration of apnoeic oxygenation
- Apnoeic oxygenation using either 5 - 15L oxygen with nasal cannulae or 60-70L of high flow humidified nasal oxygen prolongs the safe apnoea period. If only mask pre-oxygenation is carried out, gentle facemask ventilation (peak pressure <20cmH2O) can be used to maintain oxygenation .
- A pre-calculated dose of sugammadex should be available if rocuronium is used as the muscle relaxant of choice
At induction it is important that appropriate doses of induction agents and muscle relaxants are given; it is advisable to have a spare syringe of induction agent to prevent awareness in cases of unexpected difficult intubations. As we heard about in Antje’s story, there is an argument in favour of using propofol as the induction agent of choice in obstetrics for reasons which include ease of drawing up, familiarity, availability and the reduction of errors from the mix up of thiopentone with antibiotics.
Videolaryngoscopes offer improved laryngoscopy view and should be considered as first line for laryngoscopy provided one is available and the anaesthetist is appropriately trained in its use. If the initial laryngoscopy is not optimal, cricoid pressure should be released or reduced to try and improve the view. Airway problems should be communicated after the first failure to intubate, and help should be called for early.
A maximum of two attempts at intubation should be a performed, with the third attempt reserved for a different and more experienced anaesthetist.
Failed intubation should be declared after two unsuccessful attempts at intubation, and help should be sought. Oxygenation of the patient is now the priority and this can be maintained by using a supraglottic device (ideally a second generation SAD), or using facemask ventilation (Algorithm 2). A maximum of two attempts at inserting the supraglottic device should be performed, in order to minimise trauma to the airway, potentially worsening the scenario. Cricoid pressure should be released in order to allow for successful placement of the supraglottic device. If facemask ventilation is used, cricoid pressure may also need to be released, and a two handed technique may be required in order to aid ventilation.
If adequate oxygenation cannot be obtained using these techniques, a ‘can’t intubate can’t oxygenate’ situation should be declared, and front-of-neck airway (eFONA) performed. ENT and ITU help should be sought and laryngospasm should be excluded by ensuring neuromuscular blockade. Awareness should be avoided with maintenance of anaesthesia using intravenous induction agents. The Difficult Airway Society recommend using a scalpel cricothyroidotomy as the technique of choice for front of neck access, as discussed in Week 2.
Management of the patient after failed intubation
There must be a combined obstetric and anaesthetic plan for whether or not to proceed with surgery after a failed intubation. This discussion would have occurred before induction of anaesthesia, but once the failed intubation has occurred, Table 1 should be referred to again and a final decision made. If the airway is secured using eFONA, a decision may again need to be made whether to proceed with surgery (in extreme cases of maternal or foetal compromise) or wake the mother. There is an increased risk of neonatal admission to the neonatal intensive care unit after a failed intubation of the mother, and therefore the neonatal team must be aware that it has occurred. Table 2 in the DAS guidelines describes how to manage the patient on either path of waking the patient up, or proceeding with surgery after failed intubation.
As we learnt about in Week 3 NAP4 showed that 28% of all adverse airway events occurred at the end of anaesthesia and in the recovery. Extubation of the obstetric patient with or without a difficult airway falls in the ‘At risk’ extubation category of the DAS Extubation Guideline and should be managed accordingly.
Human factors and non-technical skills are as important as technical skills in the management of the difficult airway. Poor communication and teamwork all predispose to loss of situation awareness, fixation error and poor decision making. Multidisciplinary simulation based training is recommended to improve unanticipated difficult airway management outcome.
The provision of general anaesthesia in the obstetric population requires unique considerations due to the physiological changes in pregnancy, environmental factors and urgency of surgery which requires a rapid decision making process that takes into account the safe outcome of mother and baby.
Appropriate team planning and preparation for an RSI on the labour ward should be carried out in order to help to reduced adverse airway events. The OAA/DAS Guidelines are designed to help standardise teaching, reduce the incidence of failed intubation and give guidance on further management should failed intubation occur.
It is important to hold regular airway management training sessions for the whole multidisciplinary team in the obstetric setting.
Have you ever been involved in a case of a failed intubation on labour ward? Did surgery continue or was the mother woken up? Had the plan been discussed beforehand? Please do share your stories with fellow learners but please do ensure all discussions remain confidential.
You can then move on to the next activity on “Airway Management in the Obese Patient”.
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9. Frerk C, Mitchell VS, McNarry AF et al. Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults. Brit J Anaesth 2015; 115: 827-48. https://das.uk.com/guidelines/das_intubation_guidelines. Accessed 29th march 2019.
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