Airway Management And Sedation
Airway
management in the Emergency Department is more challenging than in the operating
room as patients presenting to the Emergency Department must be assumed to be
non-fasted, may be physiologically unstable, and may have head, neck or facial
injuries.
Oxygenation and ventilation
Oxygenation is ensuring that the body has enough O2;
ventilation is ensuring that there is sufficient airflow to remove CO2.
Oxygen consumption is markedly increased in the acutely unwell patient, and
giving high concentrations of oxygen supports the metabolic demands of the body
in acute illness. However, high levels of oxygen may paradoxically make some
ischaemic injury worse, e.g., brain/ heart due to vasoconstriction. A normal
‘Hudson’ O2 mask can give inspired oxygen (FiO2)
concentrations of up to 60%. They should not be used with O2 <4
L/min to prevent CO2 build-up. A mask with a reservoir bag or a
self-inflating bag-valve-mask can increase FiO2 to about 90% with
high flow (>10 L/min O
Venturi mask gives accurate low FiO2 e.g.
28%. Nasal prongs give a variable amount of O2 approx 25–30% but
should only be used with low flow rates (2 L/min O2).
Ventilatory failure
Under normal circumstances, an increased level of CO2
is the main driver to breathe. Patients with chronic lung disease, usually
COPD, become immune to this drive. For these ‘blue bloater’ patients, a low
blood O2 level drives breathing: their CO2 level will be
high.
If high FiO2 is given to these patients, it
reduces their respiratory drive, increasing their CO2 levels
further, making them sleepy, which further decreases their drive to breathe,
etc. An oxygen saturation target of 91% in these patients balances the need for
tissueion against that for ventilation.
Suction
A Yankauer suction catheter is used to suction blood,
vomit or secretions in the oropharynx. To avoid causing the patient to vomit,
do not suction the oropharynx if the patient is conscious, and ‘only suck where
you can see’.
Airway support
The jaw thrust, head tilt, oropharyngeal and
nasopharangeal airways are illustrated opposite. The oropharyngeal airway is
sized as the distance between the patient’s teeth and the angle of the
mandible. The nasopharyngeal airway should be the same length as the distance
between the tip of the nose and the tragus of the ear.
Laryngeal mask airway
Emergency Department patients are not fasted and the
laryngeal mask airway (LMA) does not prevent stomach contents being aspirated,
nor can high ventilation pressures be achieved, as might be necessary in
asthmatic patients. For these reasons the LMA is not a ‘definitive’ airway and
is not normally used in the Emergency Department.
Endotracheal tube
The most common means to provide a definitive airway,
the endotracheal tube (ETT), is a plastic tube that is inserted through the
mouth (or rarely the nose) into the trachea. There is a cuff that is inflated
to seal against the tracheal mucosa, and a radio-opaque line to indicate
position on X-ray. The ETT should be secured, e.g. with tape, and the position
checked by CO2 monitoring and a chest X-ray.
Endotracheal tubes are sized by their internal diameter:
7.0 mm for an adult female, 8.0 mm for a male. There are markings indicating
distance from the tip: this is to avoid the tube being pushed too far, e.g.
down the right main bronchus, which is larger and straighter than the left.
The decision that the patient needs intubation is the
responsibility of the doctor managing the airway. Factors indicating need for
intubation include:
•
Airway instability: bleeding
into airways, airway burns.
•
Coma: Glasgow Coma Scale (GCS) <
9, deteriorating level of consciousness, loss of protective laryngeal reflexes.
•
Inadequate oxygenation: despite
high inspired O2 (FiO2).
•
Inadequate ventilation: patient
tired/drowsy.
•
Therapeutic reasons: control
seizures, hypothermia.
•
Pragmatic reasons: combative
patient, need for transport.
A laryngoscope is needed to insert the ETT. In
some countries, straight (Miller) blades are used; in others, curved
(Macintosh) blades. These have a light to enable sight of the larynx.
McGill’s forceps have a
‘kink’ in them to avoid the operator’s hands obstructing the field of vision.
They are useful for removing loose items in the oropharynx, and manipulating
the ETT.
Surgical airway
Rarely, a situation occurs when it is not possible to
intubate or ventilate a patient. In this situation, there are two options:
•
A needle cricothyroidotomy will
provide short-term oxygenation, but is not a definitive airway, and CO2
levels will build up.
•
A surgical airway through
the cricoid membrane using a 6.0 mm cuffed ETT provides a definitive airway.
Procedural sedation
Procedural sedation is often performed in the Emergency
Department to allow relocation of dislocations or for short painful procedures.
The person performing the sedation needs appropriate skills and experience
to manage any potential situation, including the need for intubation.
The procedure should be carried out in a resuscitation
bay with full monitoring, oxygen and suction equipment. Two doctors should be
present at all times to ensure that the doctor administering the sedation has
their full attention on the patient’s airway. The patient should be fasted for
at least 4 hours, should give formal consent, and the doctor should stay with
the patient until they are consistently responsive.
After sedation patients should not drive for a day and
should be sent home in the care of a responsible adult with instructions to
return if unwell.
•
Propofol is a short-acting anaesthetic induction drug, but is used for
sedation by giving as a series of small boluses, titrating for effect. Large
doses of propofol abolish protective airway reflexes and may stop the patient
breathing. Propofol has no analgesic properties so may need to be given with an
analgesic, e.g. fentanyl.
•
Midazolam, a short-acting benzodiazepine, may be used in combination with an
opiate to provide sedation.
•
Ketamine is a safe and predictable drug that is often used for paediatric
sedation. It can be used for sedation and analgesia in adults, and may be
combined with a short-acting benzodiazepine to minimise unpleasant emergence
phenomena, e.g. hallucinations.
