Linee guida SIAARTI

Verso le Linee Guida SIAARTI per il controllo delle vie aeree in area critica e in emergenza intraospedaliera: il ruolo dell’endoscopia e strumentario
Petrini F. (1), Frova G.
(1) Anestesia, Rianimazione e Terapia del Dolore P.O.Clinicizzato SS.Annunziata- ASL Chieti
Università G.D’Annunzio, Chieti-Pescara

Literature reports that almost 30% of anaesthesia-related critical incidents occur as a consequence of airway management difficulty (1, 2).
Difficult airways may be considered as an important epidemiological problem: it is really difficult to assess the real dimension of the problem, for several reasons. The lack of common definitions, the large differences occurring in the different surgical Specialties or in the different clinical settings (elective and emergency, in-hospital and out-of-hospital), the difficulty to locate a “difficult airway event” in a statistical model and the practical problems of randomized controlled trials in this field of investigation make it really difficult to obtain precise numbers, and represent a great challenge for epidemiologists.
Furthermore we must not forget the importance of subjective experience and the  matter of “near-accidents” (especially whenever a problem is overstepped, so that it comes forgotten) or, even worse, a certain reluctance to report accidents.
According to recent data incidence of difficult mask ventilation is ranging from less than 0,03% up to 5 % according to the definition used (3). Similarly difficult intubation occurs between 1 and 20 cases over 100 patients, while difficult laryngoscopy occurs from 1 to 8% in North America (4,5), from 1 to 4,9% in the UK (6,7) 6,8% in Asia (8), 10.4% in Italian data (9) and 7,6% in a Greek study (10).
Failed intubation or procedure abandon is less frequent than difficult intubation ranging from 0,05% (31) to 0,5% (11). The actual situation should account on larger numbers, according to the anaesthesist tendency to an early withdrawal in case of non emergency failed intubations and thanking to the availability of a large number of extraglottic devices whenever intubation is not mandatory.
The incidence of more severe clinical scenarios as the can’t intubate can’t ventilate patient (CICV) is probably very low for  OR (elective anaesthesiological situations) but not for emergency department: the CICV scenario and the failed intubation leading to cricothyrotomy occur in 0,56% of difficult airway management  situation in emergency wards, and are much more rare in elective situations (12,13).
The choice of a careful strategy of difficult airway prediction is the best way to afford the problem If on one hand there is the problem of definitions and incidence, in fact,  on the other it is possible to affirm that  at least 70% of difficult airways problems may be predictable and anticipated, thus avoided, even if we must not forget that prediction is not a error-proof science.
About 90% of difficult intubations may be revealed with preoperatory evaluation (high sensibility), but only half of them result in a real difficulty and thus in a correct prediction (low specificity), and in any case a certain percentage, ranging from 0.65 to 8% remains unpredicted or unpredictable (14-17)
All the recently published Guidelines, from the 1993 ASA Guidelines (19) and reviewed in 2003 to the National Airways Societies documents (20,21), up to the 1998 SIAARTI Guidelines (22) recently reviewed (23), suggest important strategies for predicted or unexpected difficult airway management. The most important concept emerging is that in case of (severe) predicted difficulty or whenever a patient with unexpected severe difficulty may be delayed and awakened, a key role for patient’s safety and for procedure’s success is played by fiberoptic intubation. In the following sections the role of fibrescope and of new fiberoptic-like alternative devices will be briefly discussed.

The role of fibrescope (FOB) in all difficult airway management algorithms is clear and standardized: British Guidelines for  diagnostic flexible broncoscopy (24) clearly introduced some important rules for fiberoptic devices uses and management and recently ASA underline the role of FOB in trauma patients (19). No valid alternatives to FOB may be considered in a patient whose mouth opening is limited, or in which several previous intubation attempts have failed: the choice of awake FOB intubation secures airways and allows the maximum safety for the patient. In experienced hands and in presence of adequate ventilation devices and solutions (dedicated face masks, dedicated trumpets and airways) also FOB intubation in anaesthetized patient represents a safe technique, even if in some cases a more prudential awake intubation allows larger safety conditions. FOB is an extremely important device for airways management in ICU, and also represents the gold standard for tube position confirmation in cases of difficult intubation, and in pediatric difficult airway management, especially in young children or newborns, FOB intubation alone or in combination with LMA for ventilation and pathway establishment, is the most safe and successful solution (25)
For all these reasons in the recent SIAARTI Recommendations its availability wherever anaesthesia is performed is considered mandatory (23).
On the other hand FOB may have some important well known limitations and pitfalls (26): there are optical problems due to secretions and temperature (27), patient’s compliance and airway topicalization  play a key role for awake FOB intubation success, while serious difficulties may be encountered during anaesthetized patient FOB intubation. Even expert FOB users may encounter the pitfall of “hang on” phenomenon, with severe difficulty in tracheal tube advancing because of  arytenoids impingement (28), while some dedicated tube should limit this phenomenon (29).
In this setting dangerous situation of undiagnosed tube misplacement or ventilation difficulties may be encountered, such as Langeron and Coworkers suggest in a recently published paper comparing FOB and Intubating LMA (30). Last but not least FOB represent an interesting example of teaching  difficulty in the field of Anaesthesia: a constant feedback and a certain skill development and maintenance are considered necessary for a correct and safe FOB use (31,32). Finally, if FOB represents the best choice for anticipated difficulty, where a detailed planning of all available strategies and possible complications is possible, it is absolutely contraindicated in emergency situations, neither in skilled hands.

Glidescope (TM) and videolaryngoscopes
Glidescope is a videolaryngoscope (33) with a peculiarly shaped blade and  an integrated video system which allows optimal view of glottic opening with high intubation success rates using a semirigid stylet. There is a growing number of papers in Literature suggesting an important role for this device both for teaching and for difficult airways management. It provides good glottic view if compared with conventional laryngoscopy (34-36), and future developments seem to be very promising both for awake intubation (37) or as an aid for difficult FOB intubation (38). In expert hands, Glidescope may represent a valid alternative in emergency  situation before patient’s awakening or if surgery is mandatory. Other videolaryngoscopes actually allow an external view of what happens at the blade’s tip, without significant improvements of glottic view like Glidescope does.

Bonfils Laryngoscope (TM) and other rigid devices
Bonfils laryngoscope is a rigid fiberoptic device designed to perform oral intubation made up with a thin straight cylindrical body with a 40 degree curve a few centimeters from its distal end (39). Preliminary data seem to show interesting results, with an acceptably  low traumatism and  faster than ILMA in a recent comparison paper (40,41). Similarly WU-Scope (TM) a tubular fiberoptic laryngoscope, seems to have interesting features and future developments. (42,43). The pitfall for these devices may be represented by the skill necessity and by the risk of soft tissues or tracheal lesions because of devices’ rigidity.
Intubating fiberoptic stylets
Optical stylets, which incorporate flexible fibreoptic imaging elements in an intubation stylet, have become available in the last decade. More than 10 new optical stylet devices have been introduced since 1995, showing that combining viewing capability with the familiar handling of a stylet is an appealing concept. Liem and Coworkers provided a complete review on this topic (44), in which there is still an important lack of published papers support.

C-Trach (TM)
C-Trach represents a recent evolution of Intubating LMA designed by A. Brain in 1998. It provides the view of the glottic opening by adding to the classic ILMA an integrated video system with a built-in 3.5” display, a light source and a modified epiglottis elevator bar (TM). No studies are actually available, except for some abstracts (45), but promising development may come from this device, that, independently on the possibility of obtaining a good glottic view, intubation possibility and, over all, ventilation possibility are almost always granted. This may represent ai important help for emergency situations and out-of-operatory room setting or in unanticipated difficult intubation in which FOB is contraindicated.

Continuous and rapid technologic development provides a larger number of devices for difficult airways management, with fascinating possibilities in terms of airways structures vision. Anaesthesia and Intensive Care is a field in which, often, only seeing is believing; anyway we must never forget that eyes see what mind knows.


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