‘Composite Airway Failure’

It is essential to understand that in a patient in whom one airway technique fails, the risk of failure of other techniques is increased – so called ‘composite failures’.

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  After failed face mask ventilation intubation failure increases more than 10-fold.

  
  
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  After failed intubation, face mask ventilation fails in approximately 1 in 10.

  
  
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  After SGA insertion the risk of difficult mask ventilation rises threefold.

To minimise the risk of complications, when one technique is predicted to be difficult it is important to focus carefully on assessing the likely ease of other techniques that may be used for rescue.

Key Points from NAP4

NAP4 was a 1-year national registry of major airway complications during anaesthesia and in ICU or ED. It only included cases leading to

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  death

  
  
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  brain damage

  
  
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  emergency front of neck airway (eFONA)

  
  
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  ICU admission or prolongation of ICU stay

As such it only captured the airway events with the worst outcomes, the very ‘tip of the iceberg’ – lesser complications or ‘rescued events’ were not captured.

A concurrent denominator survey enabled a national incidence of events to be calculated (Table 3.3). NAP4 studied the complications of approximately 3 million anaesthetics. There were 133 anaesthesia events, 36 in ICU and 15 in ED.

Amongst ≈3 million general anaesthetics, there were 16 airway-related deaths and 3 cases of persistent brain damage. Incidences are reported in Tables 3.3 and 3.4 according to the degree of injury. The rarity of such events is noteworthy and is a key reason why assessing safety in airway management is so difficult – no individual’s or department’s practice is likely to shed light on high level safety and this is also true for almost any randomised clinical trial (RCT).

Important themes identified in NAP4 included:

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  Omitting an assessment of potential airway difficulty and risk of aspiration, and the failure to tailor the anaesthetic technique appropriately, contributed to poor outcomes.

  
  
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  Poor planning and ‘failure to plan for failure’ were common in events. Responses to unexpected difficulty and failure were unstructured. Airway managers started with only a single plan. Airway strategies were advocated; a logical sequence of plans, designed to manage failure at each step and to achieve oxygenation, ventilation and prevent aspiration.

  
  
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  Difficult or failing techniques were regularly managed with repeated attempts, especially tracheal intubation. This was associated with deterioration from a ‘cannot intubate, can oxygenate’ to a ‘cannot intubate, cannot oxygenate’ (CICO) situation. NAP4 strongly advocates adopting a limited number of attempts as part of any strategy.

  
  
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  Decisions made and techniques chosen were sometimes illogical, including using routine care in cases of known difficulty and avoiding awake intubation when strongly indicated. Lack of judgement, skills, experience, confidence and equipment all contributed.

  
  
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  Anaesthetists often used ‘their usual technique’ when this was not in the patient’s interest. Best care may require involvement of colleagues with other skill sets.

  
  
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  Quality of care was judged to be ‘poor’ or ‘good and poor’ in three quarters of cases. In a secondary study, human factors were identified in all cases (mean of four factors per case). Poor judgement, education and training were the most common contributory factors.

  
  
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  Delayed, difficult or failed intubation was the primary event in almost half of reports and intubation difficulty and failure likely occurred at some point in all cases.

  
  
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  SGAs (most often first generation) were used in the face of high aspiration risk or marked obesity and aspiration followed. Use by junior doctors and accepting a poorly functioning airway were themes in non-aspiration SGA events. Use of an SGA to avoid anticipated difficult tracheal intubation, without a rescue plan or strategy, was followed by problems: unstructured management of difficulty followed and some of these patients died. Fatalities would likely have been avoided by an awake intubation technique or tracheal intubation through the SGA (see Chapter 13).

  
  
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  Obese and morbidly obese patients were over-represented throughout NAP4. This finding has been replicated and reinforced in other important studies (see Chapter 24).

  
  
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  Head and neck cases accounted for 40% of all anaesthesia cases and the need for multidisciplinary communication and senior anaesthetic and surgical involvement was emphasised.

  
  
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  Many reported cases involved the obstructed airway. CICO was common in these. Human factors were plentiful including poor planning, communication, equipment, teamwork and situation awareness. Awake tracheostomy was too infrequently considered. When problems occurred transition to eFONA was often slow, even when part of the strategy.

  
  
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  Transition to eFONA when required was often delayed and eFONA often failed.

  
  
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  In anaesthesia events aspiration was the commonest cause of death (51% of reports of death or brain damage). Half of these cases involved tracheal intubation. Poor judgement and ignoring risk assessment were causative in many cases.

  
  
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  Unrecognised oesophageal intubation occurred in all locations and accounted for 1 in 16 cases. It was emphasised that harm from oesophageal intubation is preventable by capnography, even in cardiac arrest. (This is discussed further below.)

  
  
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  One quarter of events took place during emergence and recovery: all were associated with airway obstruction and many with post-obstructive pulmonary oedema. Blood in the airway and a suboptimal airway during maintenance were common precipitants.

ED and ICU

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  A quarter of airway events occurred in the ICU or ED. Estimates are that the rate of events leading to death or brain damage were, compared with anaesthesia, 35-fold higher in ED and 55-fold higher in ICU.

  
  
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  Permanent harm or death followed 61% of ICU reports, 33% of ED reports and 14% of anaesthesia reports.

  
  
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  In the ICU, much morbidity and mortality followed airway displacement, especially of tracheostomy and in obese patients. Delayed recognition and lack of a structured plan for such an event was prominent (see Chapter 28).

  
  
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  In the ED, most complications followed rapid sequence induction.

  
  
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  Suboptimal care, including preventable deaths, was especially common in ICU and ED reports. Issues included not recognising at-risk patients; poor planning; inadequate or inaccessible skilled staff and equipment; slow recognition of problems; unstructured responses; and poorly prepared institutional and individual strategies for managing predictable airway complications.

  
  
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  Failure to use capnography in ventilated patients or to interpret it correctly (and consequent failure to identify airway displacement or misplacement) contributed to more than 70% of ICU-related deaths.