Evidence is important: safety considerations for emergency catheter cricothyroidotomy

Abstract

It is an unarguable truth that providing appropriate training and equipment leads to improved outcomes in emergencies. Unfortunately, all too often the training and equipment are suboptimal and designed without sufficient attention to current evidence or an appreciation of the context of the emergency. Perhaps the starkest of these examples is in the provision of equipment and training for performance of the emergency surgical airway. A large, nationwide, year-long audit in the United Kingdom has shown that success rates for emergency cricothyroidotomy are highly variable.1 Singled out for particular criticism has been the catheter or “needle” method of accessing the airway and this is likely to be almost solely due to a lack of appropriate equipment and training. This commentary will outline the elements of safe practice of catheter cricothyroidotomy based on evidence from clinical and animal studies. The equipment, technique, and potential complications will be reviewed. The provision of oxygen via a catheter placed through the front of the neck into the trachea was first described by Jacoby and colleagues some 60 years ago.2 Although an inherently risky technique, in the past decade the technique has been scrutinized and refined based on data from elective head and neck surgery, animal, and mannequin-based simulation studies such that complication rates are now significantly lower.3, 4 Catheter cricothyroidotomy provides some advantages over scalpel techniques in terms of lower psychological barriers to perform them and the ability to proceed to other more aggressive techniques should they fail.5 In the hands of appropriately trained practitioners it is likely that failure rates of emergency scalpel and catheter techniques for airway access are similar.6 Only large-bore catheters should be used for access to the airway as they are more resistant to occlusion and provide a more reliable flow of oxygen. A detailed analysis of intravenous catheters shows that smaller gauge devices are more likely to be compressed and to fail during emergency rescue techniques.1, 7 In the UK's 4th National Audit Project (NAP4) of airway management complications, failure occurred in 12 of the 19 attempts at rescue using cricothyroid membrane puncture with a narrow-gauge catheter (<2-mm diameter, equivalent to catheters smaller than 14 gauge).1 Kinking of the device is the commonest complication of percutaneous approaches to the trachea. To prevent kinking the physical properties of the catheter that determine its “memory” (the property of the plastic to return to its original, straight, patent shape after kinking occurs) in addition to the size of the catheter need to be taken into account.7 The use of an InSyte 14-gauge intravenous catheter (Becton Dickinson) as suggested by Heard and colleagues8 has shown to have a lower incidence of occlusion than some purpose made catheters such as the Ravussin (VBM Medizintechnik GmbH-Germany) because of its ability to return to its original shape. Lower-pressure devices such as connection to self-inflating bags provide insufficient pressure to reliably deliver enough oxygen to the alveoli. The success of any attempt at a catheter technique requires that the equipment for high-pressure oxygen insufflation is easy to assemble and predictable for the user. Hospitals in Australia and New Zealand are increasingly stocking prepackaged “can't intubate, can't oxygenate” (CICO) kits in critical care areas such as operating rooms and emergency departments. These kits include a cheap, easy to use device for oxygen delivery such as the RapidO2 (Meditech Systems Ltd) or Enk oxygen flow modulator (Cook Medical). Importantly, these devices also allow venting of insufflated gas via the catheter, even when the upper airway is completely obstructed, provided that adequate time is allowed between each insufflation.8 The conventional caudal angulation of the catheter is advocated for cricothyroid puncture as it has been recognized for many years that angulation of the catheter from the cricothyroid membrane in a cephalad direction leads to a significant chance of damage to the vocal cords from the catheter. In a cadaveric model, vocal cord damage was seen in 8% (3/37) of retrograde intubations and the figure in live patients is estimated to be substantially higher.9 Placement of the catheter must be undertaken using an aspiration technique to ensure the catheter is within the trachea before insufflation occurs. Aspiration of air through a syringe half-filled with saline is preferred during and after placement of the catheter. This minimizes the chance of insufflation of gas into the tissues that will make further attempts at tracheal access more difficult.7 The ability of gas to leave the airway and lungs is of critical importance to prevent barotrauma during catheter insufflation. An oxygen flow of 15 L/min equates to the insufflation of 250 mL/sec making the time required to produce dangerously high intr