A modified technique of retrograde intubation using gastric tube – a manikin study
Department of Anaesthesiology and Intensive Therapy, Medical University of Łódz
- Fig. 1. Passing the gastric tube over the guide – the epidural catheter
- Fig. 2. Retrograde withdrawal of the gastric tube through the larynx into the oral cavity
- Fig. 3. Passing the endotracheal tube over the gastric tube
- Fig. 4. Advancing the endotracheal tube with the gastric tube towards the opening of the larynx and trachea
Background. Airway management is a critical skill that must be mastered by all emergency physicians. Retrograde intubation was first described in 1960, and since then it has been used as an alternative method when the classical approach to establish an artificial airway fails. Although it may be difficult due to anatomical and/or technical reasons, it requires limited equipment, is easy to learn, and has few contraindications
Methods. The author presents their own modification of the standard technique of retrograde intubation, using a gastric tube as a guide. After puncture of the cricothyroid membrane and passage of a guide wire (epidural catheter), a gastric tube is passed over the guide wire in a retrograde direction, through the previously dilated cricothyroid membrane, instead of via mouth. An endotracheal tube is then advanced over the gastric tube and inserted into the trachea.
Results. The method was tested and compared with a standard one on a manikin model by 38 anaesthesiologists and anaesthesia residents. The success rate was 96% for the modified method, and 65% for the standard method.
Conclusion. The retrograde passage of a guide catheter (e.g., gastric tube) through the cricothyroid membrane may be more effective than the routine method, when it is introduced though the mouth.
Retrograde intubation, described in 1960, is one of the methods of management in difficult intubation cases . It is used in patients with injuries to the cervical spine, face, head and neck, in oncology of the oral cavity, throat and larynx and in lockjaw of various origin, as an alternative method of intubation with a fiberoscope. Under such circumstances, however, proper placement of the endotracheal tube may not be easy. The main causes of failures include difficulties in passing the tube through the larynx opening and under the epiglottis. The endotracheal tube pulled over the guide tends to get caught in the hanging epiglottis; moreover, tight vocal cords additionally hinder its introduction into the trachea (vocal cords may be tight as retrograde intubation is most commonly performed in conscious patients under local anaesthesia). Thus, a variety of complications are likely to develop, including injuries to the epiglottis and vocal cords, trachea, mediastinal oedema, infections of the mediastinum, bleedings and haematomas, injuries to the pharynx, tongue and nose, and oesophagus. The contraindications for retrograde intubation include neoplastic processes within the cricoid cartilage and cricothyroid ligament and infections affecting these regions.
The available literature reported several modifications of retrograde intubation, all of which were to facilitate the introduction of the endotracheal tube under the epiglottis and to minimize the risk of shifting (slipping out) of the tube during the guide withdrawal.
The aim of the study was to compare the classical retrograde intubation and the method modified by the author.
Special training manikins were used to simulate difficult intubation (tongue oedema and immobilization of the cervical spine) and to enable puncture of the cricothyroid ligament. Before each attempt of retrograde intubation, the manikin cricothyroid membrane was changed.
After short presentation of the method and training of participants, retrograde intubations were carried out using two types of guides - epidural catheters and guides from central venous catheterization kits.
In the classical method after the puncture of the cricothyroid ligament, the guide was introduced cephalad until its tip was visible in the oral cavity. The guide was withdrawn from the mouth using Magill forceps; the endotracheal tube was then passed over the guide and inserted into the mouth, throat and trachea. Once its distal end was at the level of cricothyroid ligament (resistance felt while advancing), the guide was removed and the tube introduced deeper. Proper placement of the tube was confirmed by effective lung ventilation with a self-deflating sac.
In the modified method, the manoeuvres were identical until the introduction of the guide through the oral cavity. During next stages the opening in the cricothyroid ligament was widened using a scalpel and dilator from the venous catheterization set or a surgical instrument as in Seldinger`s conicotomy. The gastric tube was passed over the guide tip protruding from the cricothyroid ligament and withdrawn through the oral cavity. The endotracheal tube was then pulled over the gastric tube and advanced into the oral cavity, throat and trachea until resistance was felt at the level of cricothyroid ligament. The gastric tube was removed and the tracheal tube advanced into the trachea. The stages of the modified procedure were presented in Fig.1-4.
The study encompassed 38 anaesthesia residents and anaesthesiologists of various clinical experiences.
The success rate at first attempt was 65% for the standard method. In many cases, the endotracheal tube was introduced into the oesophagus, particularly when epidural catheters were used as guides. When guide-wires from central venous catheterization sets were used, the guides got often bent and the endotracheal tube could not be advanced.
The success rate for the modified method was 95%. The mean time from puncture of the cricothyroid ligament until confirmation of proper placement of the endotracheal tube by effective lung ventilation was 3.19 min.
The modified method of retrograde intubation suggested by the author was based on observations and conclusions drawn from trainings of emergency medicine students and anaesthesia residents. The major problem during its application is the insertion of the endotracheal tube under the hanging epiglottis and through the tight vocal cords. To facilitate the insertion of the endotracheal tube, the catheters passed over the guide from the oral side are used, which does not exclude the possibility of directing the catheter along the flexible guide into the oesophagus. Another method involves the insertion of the plastic MiniTrach II guide through the incision in the cricothyroid ligament . This option, like the one suggested by the author, however, has a serious drawback: the plastic guide is too short and does not reach the level of the connector of the tracheal tube inserted through the oral cavity, which may hinder the control of the way the tube passes and the depth of its placement. Moreover, the method requires cautious passing of the tube along the guide due to additional resistances associated with friction between both elements.
The method described in the present paper, with the use of a gastric tube, ensures extreme convenience leaving a substantial safety margin and enables easier introduction of the endotracheal tube without slipping it along the gastric tube. The tube is pulled from the side of incision of the cricothyroid ligament, which results in simultaneous moving of the endotracheal tube in the proper direction . Additional resistances related to friction are avoided. Moreover, a flexible bougie wire may be used instead of the gastric tube .
Retrograde intubation using the Cook Retrograde Intubation Set with Rapi-Fit is a modification of the classical method in which the endotracheal tube is moved along the plastic catheter to the trachea, which minimizes the risk of slipping. The cadaver studies showed the success rate of 69% for the classical and 89% for the modified method . The latter percentage was lower than the one obtained in our study.
Two gude-wires, one to advance properly the tube and another one to elevate the epiglottis, provide the efficacy of retrograde intubation. In this case, two punctures of the cricothyroid ligament are necessary.
Modification of retrograde intubation, thanks to a gastric guide used, makes insertion of the endotracheal tube easier since it is not “cramped” into the guide, as in the classical method. Such a modification had already been suggested by Butler and Cirillo, the authors of retrograde intubation . As in the presented modification, the gastric tube was introduced by incision of the cricothyroid membrane and directed towards the oral cavity where it was tied to the distal end of the endotracheal tube with surgical sutures. The tube was inserted into the trachea simultaneously pulling the catheter; once the level of the ligament was reached, the sutures were cut. The use of sutures was explained by frequent slipping of the tube from the gastric tube, which was rather short. Moreover, an epidural catheter was used for retrograde intubation, passed through the Murphy eye at the tracheal distal tip of the tube, which enabled its “pulling” rather than “pushing” . The methods listed above present some serious inconveniences – once the endotracheal tube is placed at the level of cricothyroid ligament, it should be detached from the guide. In some cases, this may not be easy. In the modification described, the gastric tube is not fixed in any way to the endotracheal tube thus can be easily removed.
Retrograde intubation carried out by an experienced clinician is a simple method associated with low risk of complications. Special sets are available but the procedure may also be performed using other devices, e.g. sets for continuous epidural anaesthesia or central venous catheterization. The training in retrograde intubation is easy and good effects are achieved quickly .
1. Retrograde intubation is a good method for provision of patent airways in anticipated difficult intubations.
2. The modified method of retrograde intubation is likely to increase the efficacy of procedures.
3. The manikin model is useful in trainings and easy to apply in studies providing repeatability of attempts and involvement of many physicians.
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Sekcja Przyrządowego Udrożniania Dróg Oddechowych PTAiIT,
Katedra Anestezjologii i Intensywnej Terapii UM w Łodzi
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