Τρίτη, 14 Ιανουαρίου 2020

Aairway management

NAP4 Report and findings of the 4th National Audit Project of The Royal College of Anaesthetists ■ ■ ■ ■ ■
Executive Summary
While it is generally accepted that airway management may
sometimes be problematic and that complications occur, it
was not known how frequently these occur or the nature of
the events. NAP4 sets out to address this.
The 4th National Audit Project of the Royal College of
Anaesthetists and the Difficult Airway Society (NAP4) was
designed to answer the questions;

■ What types of airway device are used during anaesthesia
and how often?
■ How often do major complications, leading to serious
harm, occur in association with airway management
in anaesthesia, in the intensive care units and in the
emergency departments of the UK?
■ What is the nature of these events and what can we
learn from them, in order to reduce their frequency and
consequences?
Phase one of the project established that approximately
three million patients are anaesthetised in the UK each
year in the NHS and delineated the airway devices used to
manage these.
Phase two sought to identify all cases of major
complications of airway management in the same
population as in phase one, but also in ICUs and emergency
departments. Each reported case was reviewed by an
expert panel to ensure the correct cases were included and
to maximise the amount that could be learnt. In total 186
cases met inclusion criteria and were reviewed in detail.
We acknowledge that it is very likely that not all relevant
cases were reported to the project and this is discussed in
detail in Chapter 5. We estimate that the project might
have detected as few as one in four relevant cases.
Major findings
This report is an in-depth analysis of the reviewed cases.
Each chapter includes a final section enumerating learning
points and recommendations. The recommendations
are extensive in number and breadth, reflecting the
unique opportunity this project offers to examine airway
management in the UK.
This summary does not reproduce or cover all findings in
the report but highlights the major themes running through
the report. Those with a responsibility for organising airway
management policy and for carrying out airway management
are encouraged to read the relevant parts of the report in full,
including detailed recommendations. The recommendations
are reproduced in a single document in Appendix 5.
■ Approximately 2.9 million general anaesthetics are
administered in the United Kingdom National Health
Service each year. In approximately 56% of these cases
the airway management is with a supraglottic airway
device (SAD), 38% with a tracheal tube and 5% with a
face mask.
Clinical themes
■ Poor airway assessment contributed to poor airway
outcomes. This was due to omission, incomplete
assessment or a failure to alter the airway management
technique in response to findings at assessment.
Assessment to predict both potential airway difficulty
and aspiration risk were equally important.
■ Poor planning contributed to poor airway outcomes.
When potential difficulty with airway management
is identified a strategy is required. An airway plan
suggests a single approach to management of the
airway. A strategy is a co-ordinated, logical sequence
of plans, which aim to achieve good gas exchange and
prevention of aspiration. Anaesthetists should approach
airway management with strategies rather than plans.
■ Failure to plan for failure. In some circumstances when
airway management was unexpectedly difficult the
response was unstructured. In these cases outcome
was generally poor. All anaesthetic departments should
have an explicit policy for management of difficult or
failed intubation and for impossible mask ventilation
(e.g. formal adoption of the Difficult Airway Society
guidelines as departmental policy) and for other airway
emergencies. Individual anaesthetists should use such
strategies in their daily practice.
■ The project identified numerous cases where awake
fibreoptic intubation (AFOI) was indicated but was
not used. The project methods did not enable us to
determine why AFOI was not used but there were
cases suggesting, lack of skills, lack of confidence, poor
judgement and in some cases lack of suitable equipment
being immediately available. This latter problem was
prevalent on ICU. Awake intubation should be used
whenever it is indicated. This requires that anaesthetic
departments and individual anaesthetists ensure such a
service is readily available.
■ Problems arose when difficult intubation was managed
by multiple repeat attempts at intubation. The airway
problem regularly deteriorated to a 'can't intubate can't
ventilate' situation (CICV). It is well recognised a change
of approach is required rather than repeated use of a
technique that has already failed.
■ There was a high failure rate of emergency cannula
cricothyroidotomy, approximately 60%. There were
numerous mechanisms of failure and the root cause
was not determined; equipment, training, insertion
technique and ventilation technique all led to failure.
In contrast a surgical technique for emergency surgical
airway was almost universally successful. The technique
of cannula cricothyroidotomy needs to be taught
and performed to the highest standards to maximise
the chances of success, but the possibility that it is
intrinsically inferior to a surgical technique should
also be considered. Anaesthetists should be trained to
perform a surgical airway.
■ Aspiration was the single commonest cause of death
in anaesthesia events. Poor judgement was the likely
root cause in many cases which included elements
of poor assessment of risk (patient and operation)
and failure to use airway devices or techniques that
would offer increased protection against aspiration.
Several major events occurred when there were clear
indications for a rapid sequence induction but this was
not performed.
■ Failure to correctly interpret a capnograph trace led to
several oesophageal intubations going unrecognised
in anaesthesia. A flat capnograph trace indicates lack of
ventilation of the lungs: the tube is either not in the trachea
or the airway is completely obstructed. Active efforts
should be taken to positively exclude these diagnoses.
This applies equally in cardiac arrest as CPR leads to an
attenuated but visible expired carbon dioxide trace.
■ One third of events occurred during emergence or
recovery and obstruction was the common cause in
these events. Post-obstructive pulmonary oedema
was described in one in ten reports. This phase of
anaesthesia, particularly when the airway was difficult
at intubation or there is blood in the airway, needs to be
recognised as a period of increased risk and planned for.
■ The commonest cause of the events reported to NAP4,
as identified by both reporters and reviewers, appeared
to be poor judgement. While this assessment is made
with hindsight it was a consistent finding. The next most
common contributory factor was education and training.
Choosing the safest technique for airway management
may not necessarily be the anaesthetist's most familiar.
It may be necessary to seek the assistance of colleagues
with specific skills, for example in regional anaesthesia
or airway management.
■ Events were reported where supraglottic airway
devices were used inappropriately. Patients who were
markedly obese, often managed by junior trainees,
were prominent in the group of patients who sustained
non-aspiration events. Numerous cases of aspiration
occurred during use of a first generation SAD in patients
who had multiple risk factors for aspiration and in
several in whom the aspiration risk was so high that
rapid sequence induction, should have been used.
■ SADs were used to avoid tracheal intubation in some
patients with a recognised difficult intubation. There
was often no evidence of a back-up plan. Under these
circumstances if the airway is lost (e.g. due to oedema or
mechanical displacement) this becomes an anaesthetic
emergency. Awake fibreoptic intubation or fibreoptic
intubation through a SAD before surgery may offer
a lower risk alternative to SAD use in cases of known
difficulty with tracheal intubation.
■ Anaesthesia for head and neck surgery featured
frequently in cases reported to NAP4. These cases
require careful assessment and co-ordinated planning by
skilled anaesthetists and surgeons. Excellent teamwork
is required as when any part of this process fails the risk
of adverse outcomes is high.
■ Management of the obstructed airway requires
particular skill and co-operation between anaesthetist
and surgeon. This is best performed in a fully equipped
environment with full surgical, anaesthetic and nursing
support. An operating theatre is the ideal location.
Tracheostomy under local anaesthesia may offer a
safer alternative to tracheal intubation after induction
of anaesthesia, and it should be actively considered.
When surgical airway performed by a surgeon is the
back-up plan, preparation should be made so this is
instantly available.
■ The proportion of obese patients in case reports
submitted to NAP4 was twice that in the general
population, this finding was even more evident in the
morbidly obese. Too often obesity was not identified
as a risk factor for airway difficulty and the anaesthetic
technique was not modified. Particular complications
in obese patient included an increased frequency of
aspiration and other complications during the use
of SADs, difficulty at tracheal intubation and airway
obstruction during emergence or recovery. When rescue
techniques were necessary in obese patient they failed
more often than in the non-obese. Obesity needs to be
recognised as a risk factor for airway difficulty and plans
modified accordingly.
Many of the events and deaths reported to NAP4 were
likely to have been avoidable. Despite this finding,
the incidence of serious complications associated with
anaesthesia is low. This is also true for airway management
in ICU and the emergency department, though it is
likely that a disproportionate number of airway events
occur in these locations. The aim of this report is that
detailed attention to its contents and compliance with the
recommendations will make airway management safer.
Many of the findings of NAP4 are neither surprising nor
new, but the breadth of the project, covering the whole
of the UK for a full year, will hopefully provide impetus
to changes that can further improve the safety of airway
management in the UK in anaesthesia, intensive care and
the emergency department. Our goal should be to reduce
serious complications of airway management to zero.
Dr Tim Cook, Dr NickWoodall, Dr Chris Frerk
■ In more than a third of events from all sources; during
anaesthesia, in ICU and the emergency department,
airway management was judged to be poor. More
often there were elements of both good and poor
management. In approximately one fifth of cases
airway management was judged to be exclusively good.
ICU and the emergency department
■ At least one in four major airway events reported to
NAP4 was from ICU or the emergency department.
The outcome of these events was more likely to lead to
permanent harm or death than events in anaesthesia.
Analysis of the cases identified gaps in care that
included: poor identification of at-risk patients, poor
or incomplete planning, inadequate provision of
skilled staff and equipment to manage these events
successfully, delayed recognition of events and failed
rescue due to lack of or failure of interpretation of
capnography. The project findings suggest avoidable
deaths due to airway complications occur in ICU and the
emergency department.
■ Failure to use capnography in ventilated patients
likely contributed to more than 70% of ICU related
deaths. Increasing use of capnography on ICU is the
single change with the greatest potential to prevent
deaths such as those reported to NAP4.
■ Displaced tracheostomy, and to a lesser extent
displaced tracheal tubes, were the greatest cause of
major morbidity and mortality in ICU. Obese patients
were at particular risk of such events and adverse
outcome from them. All patients on ICU should have an
emergency re-intubation plan.
■ Most events in the emergency department were
complications of rapid sequence induction. This was
also an area of concern in ICU. RSI outside the operating
theatre requires the same level of equipment and
support as is needed during anaesthesia. This includes
capnography and access for equipment needed to
manage routine and difficult airway problems.
Airway management is a fundamental anaesthetic
responsibility and skill; anaesthetic departments should
provide leadership in developing strategies to deal with
difficult airways throughout the entire organisation.

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