Emergency percutaneous airway

January 8, 2012 by  
Filed under All Updates, EMS, ICU, Resus

Comments Off

An excellent thorough review of emergency needle and surgical cricothyroidotomy – collectively described as ‘emergency percutaneous airway’ – reveals a number of pearls.

Regarding anatomy:

  • 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:

  • Include the Quicktrach II and Portex cricothyroidotomy kit
  • Sometimes require considerable force to push the device through the cricothyroid membrane, risking compression of the airway and damage or perforation of the posterior tracheal wall.

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

Saving Lives Through Failure

November 17, 2011 by  
Filed under All Updates

Think about what you would do if faced with the following situation:

You sedate and paralyse a patient with severe injuries in order to intubate them. You are unable to intubate due to a poor view and massive orofacial haemorrhage. An iGel provides temporary oxygenation while you prepare for a surgical airway.

Your first surgical airway attempt fails due to insertion of the bougie through a false (too superficial) passage. You spot your mistake and re-do the procedure successfully with a deeper incision. The patient’s airway is secure and there is good oxygenation and ventilation.

You discover that a colleague has videoed the procedure on his iPhone. However he only captured the first, unsuccessful attempt. The patient is not identifiable in the close up video. It’s late at night and only he and you know of the existence of the video. He asks you what you want him to do with it.



Do you…

(a) Ask your colleague to delete the video?

(b) Watch the video with him and look for learning points, and then delete it?

(c) Ask him for a copy of it and request that he doesn’t show it to anyone else?

(d) Other course of action

Consider your course of action given this situation, and then click below to reveal what my colleague did recently in exactly the same scenario…


(d) He did something else entirely: he got a copy of the video, burned it onto a CD, and left it on his boss’s desk!

It takes a certain kind of practitioner to risk embarrassment and criticism in the pursuit of the greater educational good.

He had already ascertained what he would need to do differently next time, so had nothing personal to gain from his chosen action.

Instead, he believed that sharing the video would help prevent his colleagues from repeating the same mistake, and help his supervisors review their cricothyroidotomy training in order to better prepare their team for the procedure. Ultimately, this gesture was directed towards the good of our patients.

His actions may have saved more than one life that evening.

Needle crike: low rate and allow exhalation

December 9, 2010 by  
Filed under All Updates, EMS, ICU, Resus

Comments Off

Two dedicated devices for transtracheal oxygen delivery through a cricothyroidotomy needle are available, the ENK Oxygen Flow Modulator (ENK) and the Manujet. Both maintain oxygenation, but the ENK is thought to achieve better ventilation (as previously shown in a pig model) because of a continuous flow that provides CO2 washout between insufflations. Very little is known concerning the lung pressures generated with these 2 devices, so a study using a simulated trachea and artificial lung model sought to determine oxygen flow, tidal volumes, and airway pressures at different occlusion rates and during both simulated partial and complete upper airway obstruction.

Manujet

Gas flow and tidal volume were 3 times greater with the Manujet than the ENK (approximately 37 vs 14 L/min and 700 vs 250 mL, respectively) and were not dependent on the respiratory rate. In the absence of ventilation, the ENK delivered a 0.6+/-0.1 L/min constant gas flow. In the totally occluded airway, lung pressures increased to 136 cm H2O after 3 insufflations with the Manujet, whereas the ENK, which has a pressure release vent, generated acceptable pressures at a low respiratory rate (4 breaths/min) (peak pressure at 27.7 +/-0.7 and end-expiratory pressure at 18.8+/- 3.8 cm H2O). When used at a respiratory rate of 12 breaths/min, the ENK generated higher pressures (peak pressure at 95.9 +/- 21.2 and end-expiratory pressure at 51.4+/- 21.4 cm H2O). In the partially occluded airway, lung pressures were significantly greater with the Manujet compared with the ENK, and pressures increased with the respiratory rate with both devices. Finally, the gas flow and tidal volume generated by the Manujet varied proportionally with the driving pressure.

The authors asset that this study confirms:

  • the absolute necessity of allowing gas exhalation between 2 insufflations and
  • maintaining low respiratory rates during transtracheal oxygenation.

In the case of total airway obstruction, the ENK may be less deleterious because it has a pressure release vent. Using a Manujet at lower driving pressures may decrease the risk of barotrauma and allow the safe use of higher respiratory rates

ENK

Oxygen delivery during transtracheal oxygenation: a comparison of two manual devices
Anesth Analg. 2010 Oct;111(4):922-4