Fig. 6.1
Master algorithm—obstetric general anaesthesia and failed intubation. The yellow diamond represents a decision-making step. Pmax, maximal inflation pressure; CICO, “can’t intubate, can’t oxygenate”. The algorithms and tables are reproduced with permission from the OAA and DAS and are available online in pdf and PowerPoint formats
Tracheal intubations should be confirmed successful using capnography trace inspection, thorax inspection, and auscultation. Additionally, the management of failed tracheal intubation and “can’t intubate, can’t oxygenate” scenarios are detailed in the Obstetric Anaesthetist Association and the Difficult Airway Society algorithms [15]. There is a strong emphasis on the importance of a supraglottic airway device placement for proper oxygenation after two or at the most three intubation attempts. Once oxygenation is secured, tracheal intubation via the supraglottic airway device is performed, best under bronchoscopic visual control.
6.3.6 Anaesthesia Maintenance
Anaesthetic maintenance requires optimal maternal and foetal oxygenation, normocapnia, avoidance of awareness and recall, optimal surgical conditions, maternal comfort, and unimpaired uterine tone [4]. In our institution, we maintain an FiO2 of 100% until clamping of the umbilical vessels. Ventilation settings are aimed to maintain normocapnia (corresponding to a PaCO2 of 30 to 32 mmHg at term).
In 2011, a UK Obstetric Anaesthetists Association survey found that volatile halogenated anaesthetics were used in 98.8% of the cases. Experimental [34] and clinical [35] data suggest that volatile halogenated anaesthetic requirements are reduced during pregnancy. Volatile halogenated anaesthetic concentration should not exceed one minimum alveolar concentration (MAC). Higher doses of volatile halogenated anaesthetics may not be given before delivery to avoid significant foetal depression and after delivery to prevent myometrial contraction alteration [4, 36–38]. Usually administration of opioids under general anaesthesia is performed only after umbilical cord clamping to avoid foetal opioid impregnation. Recently, it has been suggested that short-acting lipid-soluble opioids like remifentanil at general anaesthesia induction may limit the stress induced with laryngoscopy in high-risk patients (e.g. severe preeclampsia) [4, 36]. However, use of this strategy must be complemented with informing the neonatological team so as to adjust their neonatal care.
The use of non-depolarizing myorelaxants is not mandatory to proceed with good surgical comfort. However, if required, they may be administered and do not cross the placenta in significant amounts. Neuromuscular transmission recovery should always be monitored, even if succinylcholine was the only myorelaxant used (to rule out plasmatic pseudocholynesterase deficiency).
After delivery, to prevent postpartum haemorrhage due to uterine atony, uterotonic medications are usually administered to the patient. In our institution we routinely administer an initial slow bolus of oxytocin after delivery followed by a continuous perfusion.
Any hypotension should be promptly treated with phenylephrine or in case of low heart rate, with ephedrine titration. The use of fluid therapy is also usually beneficial to treat hypotension. Glucose-free crystalloid solutions are preferred since they do not promote neonatal hypoglycaemia.
It is important to record the anaesthesia induction to umbilical cord clamping time interval and the hysterotomy to extraction time interval. Ideally, these intervals should stay below 30 min and 180 sec, respectively.
6.3.7 Emergence from Anaesthesia
Emergence from anaesthesia must be prepared with the initiation of postoperative analgesia taking any comorbidities into account. Paracetamol, ketoprofene, and rescue therapy with IV morphine titration during the PACU stay, and oral morphine after PACU (Post Anaesthesia Care Unit) discharge can be considered as analgesic strategies.
As part of the “End of Procedure” checklist and before initiating awakening, both the obstetrician and the anaesthesiologist should share critical information, including the absence of residual bleeding and maternal stability status.
After the patient is cleared for awakening, the appropriate reversal of all neuromuscular blocking agents should be assessed.
It must be remembered that a significant part of the anaesthesia-related complications, particularly pulmonary aspiration, may occur during extubation and postoperative care [15, 39, 40]. In case of hypertensive disorder of pregnancy and/or after a difficult intubation with several attempts, a leak test should be performed before considering extubation. Where the risk for a potentially difficult reintubation is present, an airway exchange catheter may be left in place for 2–4 h following removal of the tracheal tube [41].
After a caesarean section under general anaesthesia, the early contact with the baby, with early breast-feeding where appropriate, is an important part of the general enhanced recovery programme.
Conclusion
General anaesthesia for caesarean section is a challenging scenario that the majority of the anaesthesiologists may have to manage although its occurence became rare when compared with spinal or epidural techniques. Two different clinical vignettes can summarize the most frequent cases: the scheduled caesarean delivery for non-favourable vaginal delivery planning and the emergency caesarean procedure for severe altered foetal or maternal status. If the operational procedure for both situations is similar, the environmental system differs dramatically. The holy grail of the emergency caesarean delivery is to combine a very short decision-to-delivery time period and maximizing the safety of every procedure step. To achieve this goal, optimal teaching aims at reducing the risk of cognitive overload by mastering the different technical and non-technical skills involved. Improving the initial teaching and skill retention is particularly important given the low number of general anaesthesia for caesarean section an anesthesiologist has to give in the actual context.
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