FOR DIFFICULT INTUBATION AND FOR DIFFICULT AIRWAY MANAGEMENT
ITALIAN SOCIETY OF ANAESTHESIOLOGY ANALGESIA REANIMATION AND INTENSIVE CARE
(SIAARTI SOCIETA' ITALIANA DI ANESTESIA ANALGESIA RIANIMAZIONE E TERAPIA INTENSIVA)
STUDY COMMITTEE ON THE DIFFICULT AIRWAY
Difficult intubation and airway management
Coordinator: Giulio Frova
25100 Brescia, tel. 030.3995330, fax 030.3995736
Felice Agrò, Giovanni Amicucci, Gaetano Azzimonti, Gabriella Bettelli, Antonio Brienza, Alessandro Di Filippo, Renato Favero, Gabriella Giurati, Arturo Guarino, Giorgio Ivani, Gabriella Lombardo, Alessqndro Luzi, Stefano Muttini, Giampaolo Novelli, Flavia Petrini, Giovanni Rosa, Roberto Rosi, Paolo Ruju, Ida Salvo, Gianpaolo Serafini, Giorgio Servadio, Angela Sgandurra, Giuseppe Testori, Giorgio Torri, Rosalba Tufano, Sergio Vesconi, Paolo Zuccoli
1.1. Practice guidelines are general recommendations for good clinical practice drawn from a systematic analysis of the literature and designed to reduce mortality and morbidity connected with the difficult airway management. Their objective is to help the individual anaesthesiologist in making decisions on this problem and in setting up his own simplified treatment plan or algorithm to be applied in case of difficulties. These guidelines cannot be understood as binding rules and, given the diversity of possible occurrences, their application cannot guarantee constant success.
1.2. We analysed the literature over the last 15 years. We examined 670 papers on the topic and assigned to each paper a score which refers to the degree of evidence provided by the paper in reply to the formulated question; the score, denoted by the letters A, B, C, is in relation to the design of the study. The documents informative criterion was to first give the main opinions as obtained from the literature and subsequently give the recommendations by showing the facts.
1.3. This working method based on a review of the literature might not supply answers with a high degrees of evidence (and consequently especially strong recommendations) because of the low number of papers with extensive randomised trials and because of the actual characteristics of the topic: a) difficulties are rare and individual, b) only a few anaesthesiologists accumulate such a wide experience as to be truly balanced, c) fast technological developments can make a procedure obsolete even before it is widely approved, d) exact knowledge of the actual situation is prevented by an understandable reluctance to make accidents or "near accidents" public.
The topic does not lend itself to randomised perspective designs and takes into account situations and events which should be confronted with more of an attitude marked by good practice in every day clinical practice rather than with non assumptions obtained from experimental works. Therefore, in this frame of mind, even papers with a theoretically low degree of evidence, such as those based on expert opinions, become important.
1.4. The Committee has decided to use the following terminology: essential, advisable, appropriate, non advisable, in order to further grade the recommendations.
1.5. The recommendations refer to the adult patient. Regarding the paediatric patient please refer to paragraph 11. We believe that the document should be reviewed at least every five years.
2. EXTENT AND FREQUENCY OF THE PROBLEM
2.1. The frequency results reported in the literature on the difficult airway management are often contradictory because they have been affected by both the lack of unequivocal definitions up to recent times and the change in operators behaviour.
2.2. Thirty percent (30%) of accidents entirely referable to anaesthesia is due to difficult airway management; 70% of such accidents have resulted in death or permanent brain damage.
2.3. The frequency of difficult intubation is between 0.5 and 20 % and is affected by the type of surgery (general, obstetrics, otorhinolaryngology) and by its location (inside or outside the hospital). The frequency of grade 3 difficult laryngoscopy (see annex 1) is much lower, in the range of 0.05% (equal to one over 2000 cases); the unexpected grade 4 laryngoscopy is still lower. The frequency of failed intubation is a result affected by early surrender and possible choice of other techniques, today much more frequent than in the past. The frequency of difficult ventilation is not known. The frequency of failed intubation associated with difficult ventilation is in the range of 0.01% (equal to one over 10,000 cases).
3.1. DIFFICULT AIRWAY MANAGEMENT
Difficult airway management means difficult mask ventilation and/or difficult intubation.
3.2. DIFFICULT MASK VENTILATION
The Committee has adopted, in spite of its general nature, the definition proposed by the American guidelines. Difficult mask ventilation is understood as the impossibility by the anaesthesiologist to maintain 90% saturation in pure oxygen and face mask, in a patient with normal respiratory function.
3.3. DIFFICULT INTUBATION
The Committee has partially modified the American and French definitions, by establishing that difficult intubation means a procedure which was characterised by difficult laryngoscopy (3 and 4) or that it required at least 4 attempts or more than 5 minutes for its execution independently of the anaesthesiologists degree of experience. (Concerning the number of attempts, the French guidelines mention "more than 2 attempts" by an "experienced" anaesthesiologist which correspond to 3; in the frequent hypothesis of a previous attempt by a non experienced anaesthesiologist, the attempts in fact become 4. On the other hand, ASA guidelines mention more than 3 attempts without making any reference to specific experience, but indicating an anaesthesiologist with normal experience. Concerning the problem of time, the interval indicated in the other guidelines is considered to be too long and not representative of the restricted number of attempts included in the definition. Finally the committee believes that the definition cannot disregard the degree of visibility of the glottis: it is not necessary to carry out four attempts before an experienced anaesthesiologist, after 2 correctly performed laryngoscopies, can state that intubation with a grade 4 or 3 laryngoscopy is difficult or impossible.
3.4. DIFFICULT LARYNGOSCOPY
The Committee has adopted the ASA definition. Difficult laryngoscopy means the impossibility to expose the glottis with a standard curved blade laryngoscope. It corresponds to grade 3 and 4 of the Cormack and Lehane classification (see annexes), in which one can only expose the epiglottis or the tongue, respectively.
4. PREDICTION OF DIFFICULTIES
4.1. In the clinical practice the difficulty occurs unexpectedly in 15-30% of the cases.
4.2. However, with adequate preoperative evaluation, the difficulty would be predictable in over 90% of the cases.
prediction of difficulties is based on:
|a) the targeted medical history collection (congenital and acquired pathology affecting nose, tongue, teeth, temporomandibular joints, cervical column; previous interventions and intubations, etc.)|
|b) the patients front examination (short and wide neck, scars, goitre) and profile examination (maxillary prognathism and/or micrognathia)|
|c) neck palpation (anatomical finders, the characteristics of the inframandibular space, motility), d) the determination of the following data (see annexes)|
|a) interdental distance|
|b) visibility of the pharyngeal structures (Mallampatis test)|
|c) chin-thyroid (Adams apple) distance|
|d) chin-hyoid distance|
|e) maxillary prognathism and its corrigibility|
|f) chin-jugulum distance|
|g) overall neck motility|
4.4. The prediction of intubation difficulties or impossibility can be based either on a serious deviation from the normal measurement of only one of these results, or on a slight alteration of more parameters together.
|4.5. According to the literature, the following values can, even singularly, give certainty or high prediction of difficulties:|
|a) less than 20 mm for the interdental distance|
|b) marked prominence of the upper teeth with respect to the lower teeth (maxillary prognathism) that cannot be corrected|
|c) chin-thyroid distance equal to or less than 60 mm|
|d) Mallampatis test of 4|
|e) macroglossia with apparent micrognathia|
|f) fixed neck in flexion|
|g) serious scars or post-actinic outcomes affecting the lingual floor|
|4.6. The following are borderline normal values which can also mean certainty of difficulties only if taken together:|
|a) interdental distance below 35 mm|
|b) slight prognathism and retrognathia|
|c) chin-hyoid distance less than 40 mm|
|d) chin-thyroid distance equal to or less than 65 mm|
|e) Mallampatis test of 2-3|
|f) reduced head and neck flexion-extension|
|1.||In case of elective and emergency conditions, either in anticipation of general or loco-regional anaesthesia, it is advisable to collect information on the patients medical history and to perform an accurate and targeted preoperative evaluation of the airway problem. These measures will allow the prediction of a good part of the difficulties and will enable to plan out how to face up to these difficulties (B).|
|2.||It is advisable to write all the observations made in the anaesthesia clinical file (C).|
|3.||It is essential to systematically carry out at least the following: Mallampatis test, measure the interdental distance, measure the chin-thyroid distance (C).|
5. PLANNING FOR UNEXPECTED DIFFICULTIES
5.1. Most unexpected difficulties are considered to be pseudodifficulties and are attributed to inexperience in the correct execution of the intubation manoeuvre. With the help of an expert, often these difficulties can be overcome by searching for the modified Jackson position (sniffing) and manipulating the larynx (pressure towards the back, top and right side of the patient). A relatively small fraction cannot be resolved with these stratagems and it becomes necessary to repeat the attempt with alternative aids and/or different procedures from standard ones (standard procedures means the use of a curved blade laryngoscope and a tracheal tube with no mandrel).
5.2. In these cases the anaesthesiologists behaviour is affected by many factors, such as his experience, his knowledge of alternative aids and techniques, the devices available, the clinical conditions, the patients level of oxygenation and ventilation, but above all by the degree of urgency for the intervention (elective, postponable urgency, emergency) and by the actual laryngoscope vision obtained at the first correct attempt.
5.3. Many aids are commercially available as alternative options for the unexpected difficult intubation and their indications are only partially defined. A frequent distinction is between simple and complex systems, but the criteria used in establishing the simplicity of an aid are debatable, sometimes they refer to the cost and other times to the technical complexity or to learning times. A second distinction, among systems allowing direct vision of the glottis and systems with indirect vision, has no direct reference to its final use, neither with its priority of use. A more useful distinction is made between aids destined for confronting unexpected difficulties or destined for expected difficulties. Taking a highly practical approach, an additional distinction is made between aids that one should have immediately within reach and aids that are not essential in an emergency. Independently from these classifications, the term alternative options should only be referred to devices and procedures destined for intubation attempts subsequent to the first attempt and different from the standard equipment defined above.
5.4. This uncertainty in terminology is reflected in published guidelines when they suggest that a portable unit with specific equipment for airway management be always readily available. For example, without giving any indication of priority, the ASA suggests that the following aids be available as specific equipment: 1) alternative laryngoscopy blades, 2) different diameter tubes, 3) short mandrels and Magill forceps, 4) introducers and tube-exchangers, 5) retrograde intubation set, 6) laryngeal mask, 7) Combitube, 8) cricothyrotomy set, 9) CO2 analyser, 10) equipment for fiberoptic intubation. On the other hand, others believe that it would be appropriate both to distinguish strictly speaking "alternative" aids from those aids essential for any unexpected occurrence, and to be able to have them available wherever general anaesthesia is used, whereas a trolley with aids not essential for the immediate time can be made available, if necessary.
5.5. Serious intubation accidents (death or brain damage) have been attributed to the consequences of hypoxia. Except for incorrect tube positioning (oesophageal intubation), the cause of hypoxia has not always been ascribed to failed intubation, but each time has been attributed to multiplicity of attempts by several operators, repeated use of the same equipment, lack of oxygenation, vomit, and inhalation between attempts, progressive inability to ventilate due to traumatic oedema.
5.6. Unexpected difficulties in an elective situation.
|In the absence of oxygenation problems and if face mask ventilation, with or without oropharyngeal airway, is good, the fundamental steps of the course most widely recommended in the literature are as follows:|
|a) look for collaboration|
|b) quantify laryngoscopic difficulty and choose accordingly|
|c) limit the number of attempts|
|d) give up right from the start in case of difficulties which are normally considered to be insurmountable with "alternative" instruments|
|e) give up after three failed attempts by expert hands and restore spontaneous breathing and consciousness|
|f) choose between postponing the intervention, continuation with loco-regional anaesthesia, recourse to intubation with the patient awake in local anaesthesia, either immediate or postponed.|
If it becomes difficult to ventilate the patient, then it is best to switch from a face mask to a laryngeal mask (or to the Combitube). If the patient still cannot be ventilated, then an early recourse to transtracheal oxygenation is indicated.
5.7. Unexpected difficulties in a postponable urgent situation.
In these situations (e.g., caesarean section with no maternal-foetal distress), the literature offers no suggestions different from those detected in the previous paragraph. In case of grade 4 laryngoscopy, unlike elective situations, it is not possible to postpone the intervention, but only to delay it briefly. In this event, once the patient is awakened, it is possible to go ahead with a local-block anaesthesia or, if the intubation is considered to be better for carrying out the intervention, the latter is performed under local anaesthesia while the patient is awake. After taking the necessary time for intubation, induction is once again carried on. In these cases where it is impossible to intubate with a standard laryngoscopic technique, continuation with a facial mask, or with cuffed oro-pharyngeal cannula or with a laryngeal mask is considered to be potentially at risk and is kept for situations illustrated in the following paragraph.
5.8. Unexpected difficulties in a surgical emergency.
In case of clear emergency situations (e.g., caesarean section with maternal-foetal distress), the context changes where, after an impossible intubation, one chooses to carry on under narcosis without tracheal intubation. The costs-benefits balance is different and the risk of vomiting becomes of secondary importance with respect to the emergency situation one has to cope with.
Different equipment has been used to assist or control respiration without any tube: the facial mask with or without oro-pharyngeal airway was commonly used, subsequently the laryngeal mask (or as an alternative the Combitube) was introduced, and recently the cuffed oro-pharingeal cannula (COPA). Extensive literature on the laryngeal mask indicates it as the most appropriate, in spite of its not being free from reflux or inhalation risks. Whilst this role is widely accepted in an emergency situation, what still remains controversial is its use, especially in its standard version, as a way of intubating blindly or through the preliminary insertion of an introducer.
PRELIMINARY REMARKS TO THE RECOMMENDATIONS
|1) besides tube introduction, "attempt" also simply means laryngoscopy|
|2) aids and "alternative" procedures refer to intubation attempts following the first attempt carried out with standard methods; first choice are:|
|a) short mandrel and its substitutes|
|b) Magill forceps|
|c) introducer (gum elastic bougie)|
|3) other aids suggested by the literature as "alternative" ones were not considered to be first choice; the following are among them:|
|a) straight laryngoscopy blade (Millers)|
|b) McCoys laryngoscope|
|c) light wand or Trachlight|
|d) Bullards laryngoscope|
|4) we believe that a special cart with all aids, first and second choice "alternative" ones, essential and non essential, is neither necessary nor economical; therefore, it is important to distinguish between essential aids (which should be available in every operating room) and non essential aids (if necessary available upon request)|
|5) the following are considered to be essential aids:|
|a) Macintosh curved blade laryngoscope (medium and large)|
|b) different sized tracheal tubes|
|c) Magill forceps|
|d) short malleable mandrel and its substitutes|
|e) tracheal introducer, hollow if possible|
|f) laryngeal mask or Combitube|
|g) needle cannula, at least 15 G, for cricothyroid puncture|
|h) cricothyrotomy puncture set|
|6) the following are considered to be aids that can be made available subsequently upon request:|
|a) fiberscope and light source|
|b) retrograde intubation set|
|1)||It is essential that oxygenation be given absolute priority (B).|
|2)||At every intubation attempt, it is advisable for the anaesthesiologist to consider the problem of choosing a pharmacological scheme allowing fast re-establishment of consciousness and spontaneous breathing (C).|
|3)||It is advisable to refer to the laryngoscope classification by Cormack and Lehane (C).|
|4)||It is advisable to give up immediately when one is sure of grade 4 laryngoscopy (C)|
|5)||It is advisable, in other grades of laryngeal visibility, not to carry out more than three attempts after the initial laryngoscopy (C).|
|6)||It is appropriate to make the three attempts with different techniques using aids and "alternative" procedures (C).|
|7)||Before a new attempt it is essential to re-oxygenate the patient and evaluate if he can be ventilated (C).|
|8)||It is inadvisable to carry on with intubation attempts at the smallest sign of oxygenation failure (C).|
|9)||It is advisable to know the introducer technique since it is a first choice "alternative" procedure in case of grade 3 (C).|
|10)||If the emergency is declared and the intubation has failed, continuation of an intervention with the risk of vomiting, without tracheal intubation, is considered to be inevitable (C).|
|11)||Laryngeal mask application, instead of facial mask, is advisable (C). In the presence of an emergency, recourse to the facial mask should not be delayed since it can become useless because of traumatic oedema (C).|
|12)||Blind intubation through a laryngeal mask is not recommended if good ventilation has been achieved (C).|
|13)||Fiberoptic intubation with a laryngeal mask requires specific experience and cannot be considered to be a common procedure (C).|
|14)||Blind nasal intubation is not recommended (B).|
|15)||In case of unexpected difficulties, fiberoptic endoscopy is not recommended as an "alternative" procedure, unless it is carried out by an expert (C).|
|16)||It is advisable to have available in the hospital a cart with a fiberscope for expected and unexpected difficulties when the patient awakens (C).|
|17)||This consideration should also be extended to all that is necessary for carrying out a retrograde intubation (C).|
|18)||It is essential to acquire experience with different aids outside urgency-emergency situations either on a mannequin, or in the anatomy room, or in a simulated difficulty in the operating room (B).|
5.9. Different procedures are
suggested in the literature for controlling the correct
of the tube in the airway after a normal or a
difficult tracheal intubation.
These are some of the suggestions:
a) fiberoptic vision of the rings or the carina,
b) detection of multiple capnograph curves with unmistakable morphology
c) laryngoscopic vision of the arytenoids behind the tube,
d) suction with a high volume syringe or with a self-inflating bulb,
e) connection to an ultrasound source,
f) chest auscultation,
g) chemical detection of CO2 in the exhaled flow, etc.
Only the first two are believed to have a high degree of safety.
|1)||After each intubation and, particularly after a difficult intubation, it is essential to verify the correct position of the tracheal tube (B).|
|2)||It is recommended to resort to exhaled CO2 detection or to fiberoptic endoscopy (C).|
|3)||The observed capnometric curves should be repeated and with unmistakable morphology (C).|
5.10. Safe extubation
After a difficult intubation, high incidence of traumatic damages to the upper airways, and the possibility of developing a traumatic oedema of the pharynx and of the laryngeal entrance, was described; upon removal of the tube, a hardly controllable asphyxia was described. An extubation strategy was never clearly indicated. It was suggested to evaluate whether or not the patient is capable of breathing spontaneously "around" the tube (with deflated cuff and closed tube).
The procedure giving the greatest assurance that the patient can be immediately re-intubated consists in the introduction inside the tube, before its removal, of a hollow introducer or a tube-exchanger and keeping it temporarily in situ with a continuous flow of oxygen once the patient is awake.
5.11. Iatrogenic damages occurring during a difficult intubation can at the moment be underestimated and their clinical (blood smeared secretions, subcutaneous emphysema, cervical and thoracic pain, hyperthermia, etc.) and radiological signs can show up at a later time.
|1)||After difficult intubation, it is advisable to extubate the patient using an introducer or a tube-exchanger and continuous oxygen flow (C).|
|2)||It is essential to inform the patient, thoroughly and in writing, indicating the type of difficulties met, the degree of laryngoscopy and the procedure used to face up to it (C).|
|3)||After difficult intubation, it is advisable to submit the patient to a targeted postoperative clinical control. (C).|
6. PLANNING FOR EXPECTED DIFFICULTIES
6.1. If the need for tracheal intubation is known, the recommended strategy is influenced by how postponable the surgical intervention is, by the possibility of carrying out the intervention in local-block anaesthesia, by the seriousness of vomiting and inhalation risk, by the anaesthesiologists experience, by the type of equipment available in the anaesthesiology unit and in other units, by the degree of patient collaboration, by his clinical conditions and, above all, by the foreseen difficulty.
6.2. If one is sure that intubation will be impossible or if one anticipates extreme difficulties, then it has been unanimously agreed that the safest procedure is intubation whilst the patient is awake and with local anaesthesia (with or without mild sedation) because, besides ensuring that the patients spontaneous breathing and oxygenation are maintained, it allows better identification of the anatomical structures by maintaining muscular tone.
6.3. If there are only borderline prediction signs of difficulties, the literature also proposes a different approach by envisaging the induction of anaesthesia and subsequent laryngoscope evaluation, with or without preliminary myorelaxation.
7. PLANNING FOR EXPECTED SEVERE DIFFICULTIES
7.1. Awake intubation with topical anaesthesia requires the patients understanding of the procedure explanation and his collaboration in carrying out surface anaesthesia; for this reason it is more difficult to carry out this procedure in children and cannot be carried out if the patient is incapable or hostile.
7.2. Topical anaesthesia is used (oropharynx and/or epipharynx mucosa, hypopharynx, infraglottic larynx and trachea); integration with troncular anaesthesia is rarely necessary (glosspharyngeal glossal branch block, upper laryngeal block). Topical anaesthesia, especially the intranasal route, is often incomplete because drugs much more active than lidocaine are not available in Italy. What is available is a 2% solution of lidocaine or the 10% spray. The introduction of 4 ml of 2% lidocaine through the cricothyroid membrane directly into the trachea is widely used; it is avoided in emergency patients and patients at risk of inhalation where the spray as you go technique is recommended (by means of a fiberscope with narrow operating channel).
7.3. If a patients respiratory conditions are normal, and there is no fear of jeopardising the possibility of ventilating him, mild sedation is often associated. This is not necessary if intubation is carried out under local anaesthesia after re-emerging from the general anaesthesia. The literature suggests the use of a continuous infusion of propofol or midazolam or, of ketamine in case of emergency and in the hypotensive patient. The safety sedation plan is considered to be equal to or less than third degree of the Ramsay scale (response only on command).
7.4. In case of non collaborating subject, recourse to conscious intubation might be impossible; the most widely used procedure is fiberoptic endoscopy under narcosis using either the nasal or the oral route with masks and aids which simultaneously allow ventilation. In special cases and with pre-existing oxygenation deficit, preliminary cricothyrotomy and tracheotomy under local anaesthesia have been taken into consideration as safety procedures before anaesthetic induction.
7.5. Resort to direct vision laryngoscopy by means of fiberoptic fibre optic instruments is believed to be the procedure which in these situations ensures greatest success and greatest patient protection. Flexible endoscopy , especially when carried out with instruments created specifically for intubation (longer and stronger) allows, besides direct vision, the insertion inside the trachea of the distal part of the instrument which, acting as an introducer, forms the rail road for the tube. Even though the procedure can be carried out under general anaesthesia and by oral route, made easier by the application of special masks and cannulas, the nasal route in a conscious patient and with local anaesthesia is believed to be least risky and the easiest technique. In any case, it is still a procedure that requires preliminary experience, which can be acquired either by assisting an expert or by performing it on a mannequin. Since it is not a procedure destined for emergency cases, there exists a controversy in the literature as to whether every anaesthesiologist should be familiar with its use or if he should resort to other specialists.
7.6. The literature suggests two procedures for carrying out nasotracheal fiberoptic intubation:
a) preliminary nasal introduction of a small diameter tube (6-6.5) up to the oropharynx; insertion of the instrument until the glossis is visualised; entrance of the instrument in the larynx up to half way into the trachea; sliding of the tube with possible rotation at the laryngeal entrance; after induction, possible tube substitution with a higher diameter tube using a tube-exchanger,
b) insertion of the instrument into a normal or reduced size tube which is fixed to the handpiece; nasal introduction of the instrument and passage into the trachea; sedation and/or analgesia, fast passage of the tube into the nose and then into the trachea.
7.7. There are special masks that enable to administer oxygen during the procedure execution of the manoeuvre; what is also used is the oxygen insufflation in the fiberrescope operating channel, instead of using it only for suction.
7.8. The Bullard laryngoscope is an instrument with equally high success probability, but with a more restricted field of application. Under direct fiberoptic vision, it enables to insert in the larynx an introducer on which the tracheal tube can then be rail-roaded. Many recommend the Bullard laryngoscope as a first choice instrument for awake intubation in the presence of unstable fractures of the cervical spine.
7.9. Guided or retrograde intubation is an underused procedure which is an inexpensive and rapid alternative to the use of the fibrescope. However, it has a narrower range of indications than fiberoptic endoscopy, some contraindications (distorted anatomy, laryngo-tracheal pathologies), but also the advantage of not being hindered by secretions or blood which restrict visibility with the fiberscope, especially after repeated intubation attempts.
7.10. In case of even more restricting indications (fixed neck due to unstable cervical fractures and small mouth opening) the literature has also recommended the use of the luminous stylet in its more sophisticated version or Trachlight, "semi-blind" but low-cost procedure and, for this reason, experimented in conditions lacking more complex and expensive instruments.
7.11. French guidelines do not recommend the laryngeal mask application (LMA) as first choice when anticipating an impossible intubation, but there are those who have proposed the laryngeal mask application under topical anaesthesia, and with a conscious subject, when the mouth opening is sufficient for its introduction. Once the possibility of ventilating the patient is guaranteed, higher additional sedation would be possible and the use of the fiberscope would be facilitated. The recent intubation version (LMA Fastrack), would firstly guarantee oxygenation and ventilation, and would then act as an intermediary, after induction and relaxation, for subsequent blind intubation or intubation by means of the fiberscope; a high rate of failure is reported for the LMA with blind methodology.
7.12. The case of an emergency patient, with expected serious difficulties, high risk of inhalation and who is opposed to manoeuvres whilst conscious, can represent an insurmountable obstacle which can only be overcome by surgical access to the airway. In fact, the impossibility of laryngoscope intubation and the risk of vomiting are considered to be indications for awake fiberoptic intubation with no sedation. However, lack of collaboration and the condition of urgency are contraindications for the use of endoscopy.
|1)||The anaesthesiologist should give the patient detailed information and he should obtain his consent on the expected intubation program (C).|
|2)||It is advisable to face up to expected severe difficulties always without removing patients consciousness and spontaneous breathing (B).|
|3)||The procedure recommended as first choice for a collaborating adult patient is fiberoptic intubation whilst the patient is awake, with topical anaesthesia (B) and preferably through the nose (C).|
|4)||It is advisable to monitor any possible sedation and keep it within grade 3 of the Ramsay scale (C).|
|5)||In case of expected severe difficulties, it is inadvisable to carry out the surgical intervention, should it prove possible, under loco-regional anaesthesia (plexus block, peridural, subarachnoid) without any possibility of protecting the airway in case of complications (C).|
|6)||The laryngeal mask application is inadvisable as a mean for blind intubation (C); it could be suggested as preliminary to fiberoptic endoscopy.|
|7)||In the absence of patients collaboration, it is inadvisable to resort to endoscopy under general anaethesia if there is no specific experience with it (C).|
|8)||It is essential that the possibility for intubation with the fiberscope be guaranteed for every anaesthesiology unit, either by having it at ones own disposal, or by resorting to the otorhynolaryngology or endoscopy units (C). In elective conditions and in the absence of such instrumentation, it is advisable that the patient be directed to another hospital equipped with suitable equipment and with experts in the area (C).|
|9)||The use of retrograde intubation is advisable as fast and economical replacement for fiberoptic intubation (C).|
|10)||The use of retrograde intubation is inadvisable in case of asphyctic emergency (C).|
|11)||Sellicks manoeuvre (cricoid compression with neck support) is advisable in any procedure destined for the intubation of patients under narcosis and at high risk of vomiting (C).|
8. PLANNING FOR BORDERLINE DIFFICULTIES
8.1. The risk of having a patient that cannot be intubated and that can no longer be ventilated after induction, when the expected difficulties are modest, is considered to be very low. Furthermore, there has been enough time to prepare and check all equipment indicated in the paragraph dealing with unexpected difficulties, both as alternative aids and as essential aids.
Pre-oxygenation and evaluation of the possibility of ventilating the patient are by now procedures considered to be common in these situations.
8.2. Pre-oxygenation is a device considered to be more effective in the presence of spontaneous breathing and with a conscious subject than once induction has taken place and with a relaxed patient. Therefore, spontaneous ventilation with a facial mask and pure oxygen is recommended for not less than 3 minutes or the execution of 5 forced vital powers. Oxygen store, and therefore the available apnoea time, are considered to be lower in children, in pregnant women, in chronic respiratory failure and obese subjects.
8.3. Generally it is difficult to evaluate a patients possibility of being ventilated. The literature says little on this subject, except for pointing out that some of the factors which make intubation difficult (obesity, macroglossia, short neck, limited extension of the head, oropharynx and larynx pathologies, receding chin) can also be predictive of ventilation difficulties. The presence of a beard and of nasal obstruction worsens the possibility to ventilate with a facial mask. Glossoptosis subsequent to induction and myorelaxants can also make it impossible.
8.4. After the induction of narcosis, laryngoscopy is considered to be easier in the presence of pharmacological myorelaxation, but in some cases the introduction of the laryngoscope before neuro-muscular block is suggested. There is no agreement in the literature on the choice of myorelaxants, but the suggestion to choose succinylcholine is still valid when proceeding with induction under expected (modest) difficult conditions. This suggestion is always present in obstetrics flow-charts.
8.5. The laryngoscopy scale, as with all unexpected situations, guides the anaesthesiologist in his subsequent choices.
8.6. In case of a patient with expected modest difficulties, but with a suspicion of ventilating difficulties or with the risk of vomiting or in the absence of suitable equipment, intubation in the conscious patient, under topical anaesthesia, is currently preferred rather than the rapid sequence induction and intubation used in the past.
|1)||Having given the patient detailed information and obtained his consent on the intubation program, the anaesthesiologist should also work out the strategy that he intends to apply in case of failure (for instance, awaking the patient and resorting to fiberscope) (C).|
|2)||Adequate pre-oxygenation and continuous pulse-oxymetry monitoring during the manoeuvres is always essential (B).|
9. PATIENTS WHO CANNOT BE INTUBATED-VENTILATED
9.1. After several laryngoscopy and intubation attempts, the risk that the patient cannot be ventilated with a facial mask becomes high, but it is also possible that the patients likelihood of being ventilated worsens right from the start. The difficulty in maintaining oxygen saturation in a facial mask and the rapid development of asphyxia were considered to justify rapid access to the trachea. To allow the patients ventilation, the literature has then suggested as a valid alternative the insertion of a laryngeal mask or of a Combitube. The application of such devices might not entirely solve the problem if there is an obstacle at the laryngeal entrance. In this case one is faced with a dramatic situation, rapidly developing into asphyxia, which can only be corrected by direct transcervical access to the airway.
9.2. Recourse to the so-called urgent tracheostomy by the surgeon present in the operating room is no longer considered today as a first choice procedure, because specific training is not always available, because the procedure is long and not risk-free and because of the increasing opinion that emergency oxygenation falls within the realm of specific responsibility of the anaesthesiologist. Traditional tracheotomy is restricted to neoplastic obstructions that cannot be intubated and is generally carried out by the otorhinolaryngologist under local anaesthesia and in the conscious subject.
9.3. In the subject that cannot be intubated - cannot be ventilated, the procedures for rapid access to the airway described in the literature as first choice are tracheal puncture and percutaneous cricothyrotomy, with the cricothyroid membrane as the preferred entrance route.
The cricothyroid membrane is described as the most superficial point of the airway and can be easily identified in most patients. The introduction through the membrane of an appropriate diameter (14-15 G) needle cannula for venous use allows, after checking its correct position by the suction test, the connection to a high pressure oxygen source (Jet-ventilation) or low pressure oxygen source (by-pass or intermittent delivery of the anaesthesia apparatus). The literature suggests different connection modalities and points to the risk of barotrauma if discharge towards the top is in some way hindered. Some of the limitations of this procedure are the fact that, besides oxygenation, it might be impossible to ventilate and a tendency of the needle cannula towards bending or coming out. Iatrogenic damages are also described.
This procedure, also referred to as cricothyroidotomy or laryngofissure or coniotomy, used to be carried out surgically, but the percutaneous technique is more current and more widespread also because there are many commercial sets available. The procedure makes use of three different modalities: a) simultaneous introduction of a cutting needle and cannula, b) introduction of a 4 ID cannula on a curved introducer mandrel with non-Seldinger procedure, c) introduction of a 4 ID cannula with Seldinger procedure.
There is not enough data in the literature to allow a clear definition of the advantages and disadvantages of each technique, with special reference to the execution time, the iatrogenic risks of false route, the learning curve.
|1)||When intubation has failed and ventilation is difficult or impossible, early recourse to rapid tracheal access for the oxygenation of the patient is essential (B).|
|2)||It is essential that the procedures for rapid tracheal access be included in the normal acquired knowledge of an anaesthesia-reanimation specialist (C).|
|3)||It is believed that recourse to a surgeons help or delegating such procedures to him should no longer be done regularly, but should only occur in exceptional cases (C).|
|4)||Every anaesthesiologist should know the emergency oxygenation manoeuvre by tracheal puncture and/or percutaneous cricothyrotomy (C).|
|5)||Since none of these procedures are risk-free, it is advisable to acquire adequate experience with at least a percutaneous cricothyrotomy set (on a mannequin, on an artificial trachea, in the anatomy room, on a patient undergoing laryngectomy, in intensive care) (C).|
10. TEACHING AND GAINING EXPERIENCE
10.1. Even though the individual anaesthesiologist cannot necessarily be experienced in all techniques, he should at least have a theoretical knowledge of them. Because his particular task is to ensure effective oxygenation under elective and emergency conditions, the theoretical part and the practical application part in this area have inevitably become inseparable.
10.2. Teaching programmes in post-graduate schools of Anaesthesia and Reanimation include a section on the difficult airway, both the theoretical part and the practical application part as well as a plan for gradual training directly on patients under expert supervision.
10.3. Because cases of truly difficult airway management are essentially rare, it has been widely demonstrated that every day clinical practice is insufficient for a specialist to acquire adequate experience before 7-10 years of professional work. For this reason it was also found to be useful to recommend, as part of a continuous training program, specific theoretical-practical refresher courses organised according to exact methodologies and controlled by institutional organisations, such as Scientific Societies.
11. PAEDIATRIC PROBLEM
The committee believes that paediatric problems and their corresponding recommendations ought to be the subject of a separate specialist discussion.
1) Practice Guidelines for
Management of the Difficult Airway. A Report by the American
Society of Anesthesiologists Task Force on Management of the
Difficult Airway. Anesthesiology 1993; 78:597-602.
2) Société française danesthésie et de réanimation: Expertise collective, intubation difficile. Ann. Fr. Anesth. Réanim. 1996; 15:207-214.
b) suggested textbooks
1) Airway Management: Principles
and Practice. Benumof IL editor, Mosby, St. Louis, 1996.
2) Principles of Airway Management. 2nd ed, Finucane BT and Santora AH editors, Mosby, St. Louis, 1996.
3) Difficulties in Tracheal Intubation. 2nd ed, Latto IP and Vaughan RS editors, Saunders, London, 1997.
13.1. Cormack and Lehane scale
13.2 : Prediction of difficulties
The parameters indicated are understood as having been determined as follows:
a) chin-hyoid distance:
distance between the most prominent point of the mental symphysis
and the upper part of the hyoid bone with hyperextended head
b) interdental distance: distance between upper and lower incisors with wide-open mouth
c) chin-thyroid distance: distance between the most prominent point of the mental symphysis and Adams apple with hyperextended head
d) chin-jugulum distance: distance between the mental symphysis and the sternum upper margin with hyperextended head
e) Mallampatis test: vision of the pharyngeal structures with the patient sitting down or supine with wide-open mouth and tongue spontaneously protruding and without phonation
13.3 : Mallampatis scale