Abstract
Airway management and failed intubation in the pregnant woman present unique challenges which differ from the non-pregnant patient. The provision of general anaesthesia in the obstetric population requires additional considerations of the physiological changes in pregnancy, environmental factors and the safe outcome of mother and baby. Appropriate team planning, preparation and performance of rapid sequence induction should be carried out in order to help to reduce adverse airway events. The OAA/DAS guidelines are designed to help to standardise teaching, reduce the incidence of failed intubation and give guidance on further management should failed intubation occur.
Introduction
‘Physiological changes in pregnancy, active labour and isolated location increase the complexity of management of airway complications when they occur.’ This was one of the key learning points from the 4th National Audit Project (NAP4) of the Royal College of Anaesthetists (RCoA) and Difficult Airway Society (DAS). The presence of the fetus means that severe hypoxia during difficult airway management can potentially compromise two lives. Many anaesthetists worry about the airway in obstetrics and this worry goes back over many years to the high number of cases of difficult and failed intubation and/or failed ventilation that regularly used to feature in the Reports on Confidential Enquiries into Maternal Deaths. Since the early 1980s, such incidences have reduced considerably and this is partly as a result of better training, staffing, equipment and facilities, and partly through greater use of regional anaesthesia in obstetrics. However, the risk of failed intubation remains and there is concern that changes in anaesthetic training as well as reduced number of general anaesthesia for caesarean sections have led to reduced exposure of trainees to general anaesthesia for caesarean section. A recent UK report on maternal mortality stated that effective management of failed tracheal intubation is a core anaesthetic skill which should be taught and rehearsed regularly and strongly recommended the use of simulation for teaching and rehearsing failed intubation. Recent publication of the obstetric difficult airway guidelines by the Obstetric Anaesthetists Association (OAA) and DAS includes an algorithm for ‘Safe obstetric general anaesthetic’. This algorithm is designed to be used as a teaching tool to update and standardise the conduct of general anaesthesia for the pregnant woman.
Incidence of Morbidity and Mortality
Failed intubation in obstetrics is still higher than failed intubation in the general population and has remained unchanged over three decades at 1:390 for obstetric general anaesthetics (GAs) and 1:443 GAs for caesarean sections. Morbidity and mortality following failed intubation are similarly higher in the obstetric patient than the general population. Maternal mortality from failed intubation is approximately 2.3 per 100,000 GAs for caesarean section (1 death per 90–102 failed intubations) compared with 0.6 per 100,000 GAs for the general population in the NAP4 report. The incidence of front of neck airway (FONA) procedures was similarly higher at 3.4 per 100,000 compared with 2 per 100,000. When there is failed intubation during anaesthesia for caesarean section, it is very difficult to separate the effects on the fetus of the failed intubation from the underlying compromise that might be the reason for the caesarean section. However, in a large UK study, neonatal intensive care unit (ICU) admission was higher in the failed intubation group (34%) than in those who underwent uncomplicated general anaesthesia (20%), though this was not statistically significant. Multivariate analysis identified failed intubation and the lowest maternal oxygen saturation as independent predictors of neonatal ICU admission. The key message is that maternal hypoxia during airway difficulty may influence neonatal outcome.
Airway Assessment in Obstetrics
Prediction of difficult airway is notoriously inaccurate and is covered in detail in Chapter 5. While factors that predict difficulty in pregnancy are the same as for non-pregnant patients, the airway should be reassessed during labour because repeated straining during contractions, oxytocin and intravenous fluids may all cause airway oedema.
Pregnant women with a potentially difficult airway should be identified as early as possible in pregnancy so that the anaesthetist can formulate an airway management and anaesthetic plan. Many obstetric units have antenatal anaesthetic clinics and each unit should have a checklist to assist midwives and obstetricians to identify women who should be referred to the anaesthetic clinic. Good communication and documentation are extremely important to ensure details of any airway management plan are available to the team involved in the final care of the patient.
Causes of Difficult Airway in the Obstetric Patient
These can be classified into anatomical and physiological changes of pregnancy, training issues and situation/human factors and are listed in Table 22.1.
Table 22.1 Factors contributing to difficulty with the airway in pregnancy
Anatomical and physiological changes of pregnancy
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Training issues
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Situation and human factors
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General Anaesthesia
It has long been recognised that the obstetric rapid sequence induction (RSI) is outdated and that it needed to reflect current practice in the non-pregnant population. The OAA/DAS obstetric difficult airway guidelines provide an algorithm to support a modern safe approach to general anaesthesia in the obstetric patient (Figure 22.1).
