To the Editor:—
Lenfant et al.1
are to be congratulated on their study comparing two techniques for retrograde orotracheal intubation using the cricothyroid approach in cadavers. Their modified technique is similar to that reported by Tobias,2
although he used a fiberscope as a catheter through the endotracheal tube into the trachea before removing the guide wire.
The authors report 22 failures with the classic technique versus 8 with the modified technique. It is not clear whether esophageal intubation occurred in all of these cases or whether there was supraglottic placement in some. Also, there is no mention of the size or type of endotracheal tube used in the study.
It is crucial that the tip of the endotracheal tube is positioned beneath the vocal cords for subsequent successful passing of the catheter into the trachea. Although passing a thin catheter over the guide wire is easier, resistance may be encountered while advancing the endotracheal tube over the catheter, especially at the level of the glottis. Similar difficulty with the advancement of the endotracheal tube over a fiberscope3
or a bougie4
is well documented and is related to the size and type of endotracheal tube and the position of the bevel. It would be interesting to know the incidence of such “hanging-up” phenomenon and the requirement for any maneuver to overcome the same in the current study. It is important to understand the dynamics of failed retrograde intubations to improve the success rate.
The authors comment that the subcricoid approach may be more dangerous than the cricothyroid approach. Literature on the use of the subcricoid approach for retrograde intubation is sparse. Subcutaneous emphysema, minor skin bleeding, and incorrect positioning are the reported complications (10%) with percutaneous minitracheostomy using the subcricoid approach in 50 patients.5
On the contrary, it is shown that retrograde intubation using the cricothyroid approach has more potential to cause vocal cord trauma than the subcricoid approach.6
Various complications, including pneumomediastinum, have been reported after the cricothyroid approach.7
The area from the cricoid cartilage to the lower border of the first ring of the trachea is devoid of major blood vessels or nerves,8
whereas the cricothyroid membrane is crossed by the cricothyroid artery superiorly.9
The subcricoid approach of retrograde intubation using the cricotracheal membrane seems relatively safe, with the advantage of improved success rate.6,8
Senthil K. Nadarajan, M.D., F.R.C.A.
Colchester General Hospital, United Kingdom. email@example.com
1. Lenfant F, Benkhadra M, Trouilloud P, Freysz M: Comparison of two techniques for retrograde tracheal intubation in human fresh cadavers. Anesthesiology 2006; 104:48–51
2. Tobias R: Increased success with retrograde guide for endotracheal intubation. Anesth Analg 1983; 62:366–7
3. Johnson DM, From AM, Smith RB, From RP, Maktabi MA: Endoscopic study of mechanisms of failure of endotracheal tube advancement into the trachea during awake fiberoptic orotracheal intubation. Anesthesiology 2005; 102:910–4
4. Dogra S, Falconer RF, Latto IP: Successful difficult intubation: Tracheal tube placement over a gum-elastic bougie. Anaesthesia 1990; 45:774–6
5. Van Heurn LW, Van Geffen GJ, Brink PR: Percutaneous subcricoid minitracheostomy: Report of 50 procedures. Ann Thorac Surg 1995; 59:707–9
6. Lleu JC, Forrler M, Forrler C, Pottecher T: Retrograde orotracheal intubation [in French]. Ann Fr Anesth Reanim 1989; 8:632–5
7. Bowes WA III, Johnson JO: Pneumomediastinum after planned retrograde fiberoptic intubation. Anesth Analg 1994; 78:795–7
8. Shantha TR: Retrograde intubation using the subcricoid region. Br J Anaesth 1992; 68:109–12
9. Dover K, Howdieshell TR, Colborn GL: The dimensions and vascular anatomy of the cricothyroid membrane: Relevance to emergent surgical airway access. Clin Anat 1996; 9:291–5
© 2006 American Society of Anesthesiologists, Inc.