An excellent thorough review of emergency needle and surgical cricothyroidotomy – collectively described as ’emergency percutaneous airway’ – reveals a number of pearls.
- The cricothyroid menbrane has an average height of 10 mm and a width of 11 mm
- Transverse incision in the lower half of the cricothyroid membrane is recommended to avoid the cricothyroid arteries and the vocal cords
Regarding oxygenation / ventilation via a cricothyroid needle:
- High pressure source ventilation via a needle (eg. by Sanders injector or Manujet) may cause laryngospasm, so a neuromuscular blocking agent should be considered
- Barotrauma may result from an obstructed upper airway, so efforts should be made to maintain upper airway patency where possible (eg. with a supraglottic airway)
- A device has been manufactured that provides suction-generated expiratory ventilation assistance (using oxygen flow and the Bernoulli principle) – the Ventrain
- The Fourth National Audit Project reported a much lower success rate and described several complications of attempted re-oxygenation via a narrow-bore cricothyroidotomy
- Where there is no kink-resistant cannula or suitable high-pressure source ventilation device readily available, it is probably safer to perform a wide-bore cannula puncture or surgical cricothyroidotomy.
Wide-bore cannula-over trocar devices:
Seldinger cricothyroidotomy kits:
- Separate the puncture and dilatation steps, minimising the risk of trauma
- Include the Melker emergency cricothyroidotomy set, available in sizes 3.0–6.0 mm ID
- Tend to be preferred by anaesthetists over the surgical and wide-bore cannula-over-trocar techniques
- Seldinger technique in human cadavers and manikin studies by those well trained, inexperienced operators have low success rates and a long performance time
What about after?
- High-pressure source ventilation may aid subsequent intubation by direct laryngoscopy as bubbles may be seen emerging from the glottis.
- The Seldinger technique has been recommended to convert a narrow-bore cannula into a cuffed wide-bore cricothyroidotomy
- While conversion of cricothyroidotomy to tracheostomy within 72 h has been advocated because of the increased risk of developing subglottic stenosis with prolonged intubation through the cricothyroid membrane, this risk may be much lower than previously believed
- The risk of conversion, although less well examined, may also be appreciable
Which technique is best?
- The recent NAP4 audit reported a success rate of only 37% for narrow-bore cannula-over-needle cricothyroidotomy, 57% for wide-bore cannula techniques and 100% for surgical cricothyroidotomy
- Simulation studies show conflicting results about whether seldinger or surgical technique is faster.
- Reported success rates of the different techniques (in simulations) also vary widely and range for surgical cricothyroidotomy from 55% to 100%, for wide-bore cannula-over-trocar from 30% to 100%, and for Seldinger technique from 60% to 100%.
The one area of some consensus is that conventional (low-pressure source) ventilation should not be used with a narrow-bore cannula; a high-pressure oxygen source and a secure pathway for the egress of gas are both mandatory to achieve adequate ventilation.
Complications may be related to technique:
- Complications of narrow-bore cannula techniques are ventilation-related and include barotrauma, subcutaneous emphysema, pneumothorax, pneumomediastinum and circulatory arrest due to impaired venous return; Cannula obstruction due to kinking also occurs.
- Seldinger technique may be complicated by kinking of the guidewire, which increases the risk of tube misplacement
- Bleeding and laryngeal fracture may complicate the surgical method, and long-term complications include subglottic stenosis, scarring and voice changes.
Equipment and strategies for emergency tracheal access in the adult patient
Anaesthesia. 2011 Dec;66 Suppl 2:65-80