Introduction
Several considerations may complicate the acquisition of a patent airway, and a significant proportion of difficult and failed intubations occur during obstetric emergencies. First, a satisfactory airway assessment cannot be completed and is linked to a failed intubation. Even diligent anesthesiologists find intubations difficult. The main concern with difficult intubation or intubation failure is to develop action to avoid such cases from becoming a failure before or during induction. As a result, providing safe anesthetic care and avoiding intubation-related injuries remains crucial. Failure to accomplish effective tracheal intubation in a maximum of three efforts, irrespective of the technique utilized, is termed failed tracheal intubation.
The definition of failed intubation tends to vary. The lowest qualification threshold is intubation which was not fulfilled with a single dose of Succinylcholine. It was defined by McKeen et al. as failed attempts during placement of an endotracheal tube into the trachea either using direct laryngoscopy or alternative intubating devices, the need to progress with surgery with a non-elective unprotected airway (bag-mask ventilation or laryngeal mask airway), or the need to abort intubation or surgery and wake up the woman before surgery.
What Are the Limits to Failed Tracheal Intubation in Oxygenated Patients?
Scientific proof continues to mount that as the number of tracheal intubation attempts increases, patient morbidity also increases. With each failed attempt, a sequential increase in the risk must be assumed so that a second or third tracheal intubation effort should occur only if a different strategy is used and there is a significant chance of success. It must justify more than three tracheal intubation attempts.
How Is Failed Intubation Managed?
Three unsuccessful attempts at tracheal intubation should be considered a failed intubation scenario. This should cause the team to pause and consider an exit strategy to avoid repeated ineffective intubation efforts that could endanger the patient.
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Awakening the Patient:
The choice of permitting the induced oxygenated patient to wake after failed tracheal intubation should be considered whenever possible. For example, in a spontaneously breathing patient, awake tracheal intubation can be attempted once the patient is awake and cooperative. Alternatively, an elective surgical procedure could be postponed or performed under regional or infiltration anesthesia. Before the patient gains consciousness from a general anesthetic effect, oxygenation should be preserved with a face mask or a supraglottic device. Especially, in an emergency, during a resuscitation procedure, or if the patient cannot engage in awake intubation, and waking patients in problematic situations. When tracheal intubation fails, this choice is supported by expert consensus to avoid worsening to a "cannot intubate, cannot oxygenate" situation.
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Proceeding with Surgery Using a Face Mask or Supraglottic Device (SGD) Ventilation:
The benefit of proceeding with surgery under a face mask or SGD ventilation must outweigh the danger of preceding tracheal intubation as an exit plan for failed tracheal intubation in the induced or unconscious patient. This will be easier to justify for minor or emergency procedures; the aspiration must be considered as the risk. If the surgery is performed with a face mask or SGD ventilation, a plan for complexity or failure of oxygenation should be in place. The critically ill non-surgical patient who is temporarily ventilated with a face mask or SGD will almost certainly require tracheal intubation or a surgical airway as soon as possible.
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Obtaining Additional Equipment or Expert Assistance for a Second Controlled Attempt at Tracheal Intubation:
There is no doubt that limiting tracheal intubation attempts is a good idea. Nonetheless, the goal of implementing an exit strategy is not necessary to restrict more than three intubation attempts but rather to serve as a reminder that additional attempts may result in increased patient harm and decreased chances of success.
As a result, an exit strategy attempt at tracheal intubation should be made only when there is a high likelihood of success and a low probability of complications. For instance, if placed in SGD after three failed tracheal intubation attempts, bronchoscopy-aided intubation could have occurred through the SGD once an appropriate flexible bronchoscope became available.
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Proceeding with Surgical Access:
After a failed tracheal intubation, it may be relevant to continue with surgical access (cricothyrotomy or tracheotomy) in the adequately oxygenated unconscious or induced patient. This may be necessary if waking the patient is not the best choice.
What Are the Emergency Strategies for Failed Oxygenation Attempted During Tracheal Intubation?
Failed oxygenation occurs after failed tracheal intubation if the patient cannot be effectively oxygenated using an optimized face mask or SGD ventilation. Three preventive actions are required: immediate recognition, a call for assistance, and planning for a surgical or transtracheal airway (cricothyrotomy in the adult patient).
Due to the rareness of this type of scenario, clinicians frequently exhibit a lack of situational awareness when faced with failed oxygenation or cannot intubate or cannot oxygenate (CICO), having become fixated on multiple unsuccessful attempts at tracheal intubation or SGD placement. Failure to recognize and respond appropriately to failed oxygenation or CICO has been shown to postpone cricothyrotomy, giving rise to cerebral hypoxia and cardiac arrest. Therefore, all members of the gathered team must be able to call for assistance or raise the need for an emergency cricothyrotomy.
If oxygenation or CICO fails, at least one attempt should be made by placing an appropriately sized SGD familiar to the operator. During the SGD attempt, a second person should prepare the equipment and the patient's neck for a cricothyrotomy. Without further trials, immediate cricothyrotomy should be performed because one of the most severe problems of cricothyrotomy insertion is an incorrect passage. The proper cannula or tube position must be objectively validated by capnography or endoscopy.
How Is Tracheal Intubation Confirmation Done?
The continuous presence of "appropriate to the clinical circumstance" expiratory carbon dioxide provides objective verification of tracheal intubation. Additional confirmation can be obtained through endoscopic observation of the subglottic airway using a tracheal tube or inspection of a tracheal tube between cords. Chest rise and auscultation, tube fogging, chest radiography, and pulse oximetry are unreliable predictors of tracheal intubation success. Prolonged capnographic monitoring has also been recommended for patients undergoing deeper levels of procedural sedation who do not receive tracheal intubation.
What Are Special Considerations for Obstetric Airways?
In many emergencies, high anesthetic experience and skills allow for efficient and rapid neuraxial anesthesia. Multiple conditions may interact and lead to parturient airway morbidity. In order to minimize these factors, obstetrical units must adequately train staff and have immediate access to air equipment of the same quality and type (for example - video laryngoscopes) as that used in the central surgical units.
Conclusion:
Despite meticulous pre-anesthetic evaluation and preparation, endotracheal intubation may fail anytime during emergencies. Its cause can be determined and assessed with detailed patient assessment and holistic reevaluation. Anesthesiologists must always have anesthetic management protocols in place to ensure patient safety in the event of a failure.
