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).
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.
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’.
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.
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.
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 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.