Obstetric difficult airway

Difficult airway in
obstetrics

Dr Mark Porter | consultant obstetric anaesthetist
Airway refresher day, 20 October 2021

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How it used to be – methods

1950s inhalational anaesthesia
•Facemask; nitrous oxide, ether; cyclopropane
•Crawford 1959: “Dominant opinion in Britain is probably still in favour of ether as

the mainstay in obstetric practice”

Challenges (among others):
•Awareness
•Acid aspiration syndrome

1959 BJA Hamer Hodges method
•Head up, thiopentone, succinylcholine, intubation, oxygen, nitrous oxide technique

1961 Sellick’s manoeuvre
•Cricoid pressure

Challenges:

•Intubation under pressure

Only a few years ago

ME Tunstall 1976 Deaths continued to
Failed intubation drill occur; stress and
Anaesthesia 31; 850 fear remained with
the obstetric
anaesthetist

Coping with
the

challenges

Ranitidine and 21st century –
omeprazole awareness that new
SGADs had a place
introduced in the
1980s

How it used to be – deaths due to
anaesthesia

Triennium Maternities Caesareans Deaths due Rate per

(thousands) (thousands) to 100,000

anaesthesia maternities

1964-66 2,600 88 50 1.92

1982-84 1,884 190 19 1.00

2000-02 1,997 425 7 0.35

2014-16 2,302 514 1 0.04

2016-18 2,235 577 1 0.05

1973-75 David Levy, Anaesthesia for caesarean section, BJA CEPD
2001

• “There were 13 deaths due to the inhalation of stomach contents”
• “There were 7 deaths in which the immediate precipitating factor was difficulty with endotracheal intubation”

1982-84

• “There were ten deaths primarily due to difficulty with endotracheal intubation”

Obstetric anaesthesia today Indications

for GA

Spinal Urgency
anaesthesia has precludes
become dominant neuraxial block
since the 1980s

9% of caesarean Conversion from
births done under failed neuraxial
Neuraxial block
GA
50% category 1 is
caesarean contraindicated
sections done Neuraxial block
under GA
is refused

Difficult airway associations

Pressure to High risk of Emergency Rapid onset Difficulty
avoid HIE regurgitation presentation hypoxaemia inserting
& aspiration laryngoscope

Poor view at Oedematous, Hasty Reduced
laryngoscopy friable induction focus and
airways vigilance

NAP4 –
major complications
of airway
management

NAP4 recommendations

Maintain your •Despite the relative infrequency of general anaesthesia for caesarean
skills section, obstetric anaesthetists need to maintain their airway skills
including strategies to manage difficult intubation, failed intubation and
CICV

Use 2nd gen •Obstetric anaesthetists should be familiar and skilled with supraglottic
SADs for rescue airway devices for rescuing the airway: particularly those designed to
protect from aspiration and to facilitate ventilation and or intubation

Fibrescopes •A flexible fibrescope may have several roles in the obstetric setting.
available Anaesthetic departments should provide a service where the skills and
equipment are available to deliver awake fibreoptic intubation whenever
it is indicated

Trained •All staff working in the recovery area of a delivery suite including
recovery staff midwifery staff must be competency trained

•Skills must be regularly updated



OAA DAS guidelines
2015

A master algorithm Algorithm 1 gives a Algorithm 2 summarises Algorithm 3 covers the
provides an overview framework on how to the management after management of the
optimise a safe general declaring failed tracheal ‘can’t intubate, can’t
anaesthetic technique in
the obstetric patient intubation oxygenate’ situation and
Table 1 gives a structure Table 2 gives practical emergency front-of-neck
considerations of how to
for assessing the awaken or proceed with airway access
individual factors
relevant in the decision surgery
to awaken or proceed
should intubation fail



OAA DAS guidelines – key messages

Teachable Preoxygenation Cricoid pressure Failed intubation Front of neck access More comprehensive
Standardised Reduce or remove Declare incident Continue to give guidance on
algorithm for Nasal cannulas at to facilitate Mask ventilation oxygen
2-5 L min-1? intubation decision to wake or
obstetric general Facemask Remove for SAD continue
anaesthesia Safe management
ventilation during without
apnoeic period endotracheal tube
<20 cm H2O
Use of THRIVE Use NMB first to Is it necessary and
devices exclude safe to continue?

laryngospasm

Supraglottic airway
device insertion

transnasal
humidified rapid-
insufflation

ventilatory exchange



Incidence of failed obstetric tracheal
intubation

Literature review found
incidence to be about 1:400

One FONA per 60 failed
intubations

One death per 90 failed
intubations

Failed intubation and
desaturation are independent
predictors of NICU admission

Maternal mortality reports Human
factors

Prolonged Airway problems Aspiration Obesity Failed
hypoventilation Worsened by Small bowel intubation
during or following fixation error
obstruction + Cat
GA 3 CS
Obese
The choice of endotracheal tube for
Severe pregnant women should start at size
bronchospasm 7.0mm and proceed to smaller tube
after induction selections if needed (size 6.0mm and
5.0mm). It is recommended that all
Following resuscitation carts used in maternity
extubation + long units should include endotracheal tubes
delay before re-
no larger than 7.0mm and include
intubation smaller sizes such as 6.0mm and

5.0mm.

A case in point

A woman was undergoing Two more senior anaesthetists
intrapartum caesarean birth under arrived rapidly
spinal anaesthesia when massive
They immediately induced general
obstetric haemorrhage anaesthesia as their first
supervened treatment step.

Her anaesthetist recognised this
and called for help to manage the

MOH

Neither anaesthetist was able to This incident led to the
intubate the patient for about 20 development of UHCW guidelines

minutes on using second-generation
She carried on bleeding and SGADs in difficult intubation
These replaced the 1970s Tunstall
ended up on ICU
failed intubation drill.

Keeping focus on the task at hand

Another case in point

A woman was being assessed for an On questioning, she had a clear, coherent,
intrapartum caesarean birth under spinal and terrifying recollection of all events
during the management of the difficult
anaesthesia intubation
In great distress, she told her anaesthetist
that she was terrified of anaesthesia owing This had developed in the weeks after her
delivery
to what happened last time
•During this extended process, she had
•In her previous caesarean two years not been given any hypnotic or muscle
before, she had become apparently relaxant drugs
unconscious at delivery After intubation, nitrous oxide and
isoflurane was administered
•Her anaesthetists attempted to intubate
her, but it was very difficult. In the end,
they inserted an LMA, and then an ET
tube through the LMA

Accidental awareness

Risk Risk factors Induction Maintenance Emergence
include:

1:19,000 Use of 50% of AAGA 30% of AAGA 20% of AAGA
general thiopental Should we be Poor
withholding Reduced
1:8,000 with Emergencies, volatiles and management
NMBs and also RSI opioids? of NMB
1:670 Use of NMBs Beware N2O
Patient female antibiotic Perhaps some
caesarean syringes resistance to
sections ± young ± Have spare IV
obese hypnotic drugs.

OOH case

Obstetric Junior The 64 recommendations to
anaesthesia is anaesthetist mitigate AAGA include always
overrepresented by a Prolonged practising well and carefully,
factor of 10x and basing patient consent on
airway
management incidence information
Swift start to

surgery

DREAMY study – direct reporting of
awareness in maternity patients

4 patients had
PTSD

Direct Incidence Associates:
questioning 1:256;
about •BMI extremes
awareness •for CS, 1:212 •OOH
•ketamine or
thiopental
•(NMB, RSI etc)

Study:

•3000 patients
•2017-18
•UK

“Action is needed to reduce this very high risk
and national consensus guidelines would
help to ensure consistency of anaesthesia

practice.”

Obese parturients Plan for
success

Assess women
with booking
BMI > 40 kg m-2
Avoid airway
problems with

neuraxial
analgesia
Acquire specialised
equipment e.g.,
Oxford pillow,
ramped position
Afterwards –
extubation

The developing consensus for change

Videolaryngoscopy Propofol instead of Rocuronium instead No consensus on
as standard thiopental of suxamethonium stress response

• It does not take • Familiarity • Contention over • Short-acting
longer • Avoidance of intubating opioids
conditions
• Direct and indirect AAGA • Other drugs e.g.,
modes • No confusion with • COVID-19 & cough lidocaine
• Significant cost of
• Still need to other drugs
optimise insertion • Suppression of sugammadex
conditions • Contention over
airway reflexes
anaphylaxis

Key message – planning

Key message – training

Practical advice points

Preparation Focus Basics Believe two things at once
•Keep your patient well
•Equipment and practice •Do not focus on getting •It's just a GA; it’s my job;
•Consider universal an ET tube in oxygenated, relaxed, and I can do it
unconscious.
videolaryngoscopy •Instead, focus on •Have a friend present
preventing the maternal except in the most
and fetal morbidity and pressing emergencies
mortality that can follow
failed intubation

Obstetric difficult airway
Risk and mitigation summary - ‘the last slide’

Reduced oxygen Increased oxygen Left tilt reducing Anatomy: Rapid sequence
reserve – FRC consumption effectiveness of shortened neck, induction done
cricoid pressure airway oedema,
enlarged breasts hastily

Greater Isolated location Psychological Active labour
prevalence of pressure of
expectation
obesity

Planning and training Antacid premedication DAS recommendations for Focus on your task
RSI
•Anticipate the difficulties •PO ranitidine 150 mg or •Control your environment
– fixed and modifiable PO omeprazole 20 mg •Nasal cannulas to •Anaesthetise the patient
augment preoxygenation •Make sure she gets
•The right equipment – •IV ranitidine 50 mg or IV
polio laryngoscope, omeprazole 40 mg if no •Facemask ventilation oxygen, relaxants, and
suction, SADs, time before intubation hypnotics
videolaryngoscope,
ramping •IV metoclopramide •Nasal cannulas to
10 mg continue during
•Training and equipment intubation
for front-of-neck rescue •PO sodium citrate 0.3M,
30 mL oral •Reduce or remove
•Good communication cricoid pressure if
with the operating difficult or SGAD
theatre team

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