2.5.1 Why Do These Algorithms Work Best in Emergency Situations?
The following Emergency Airway Management Algorithms adhere to the design elements of effective algorithms and are specifically intended to be applied in crisis situations in which actions must be intuitive and automatic to increase the changes of a good outcome. They are derived in a similar fashion to the ASA algorithm and are based on the same evidence. They describe a logical progression of thinking and doing when faced with the crash situation, the difficult airway, and the failed airway. An algorithm dealing with extubation of the difficult airway is also presented.
These algorithms are shown in Figures 2-3, 2-4, 2-5, and 2-6. The reader is encouraged to refer to the figures while reading the text descriptions below. The Emergency Airway Algorithms do not address the indications for intubation and do not deal with the decision to intubate. Therefore, the entry point for each one is immediately after the decision to intubate has been made.
Airway management overview.
Emergency Difficult Airway Algorithm.
These algorithms, though consistent with the thinking imbedded in the ASA algorithm, are tailored for urgent and emergency clinical situations and adhere to the principles fundamental to such clinical situations. They are meant to guide the development of response strategies to high threat/low-frequency events for which one has not developed automatic responses. Importantly, the algorithms presented in this chapter are not meant to be memorized and followed slavishly, as with a recipe. They are the ways of rapidly thinking through urgent clinical situations and helping to make crucial decisions and actions.
The practitioner may fail to appreciate the failed airway and subsequently fail to move quickly to a salvage strategy or to secure a surgical airway. It must be emphasized that there ought to be no hesitation in performing a surgical airway or cricothyrotomy in the face of airway management failure.
2.5.2 the Overview Algorithm
The Overview Algorithm (Figure 2-3) presents the way most practitioners approach the issue of airway management. Most of the time, it is routine, elective, controlled, and deliberate. Most intubations are not crash or emergency situations. So the first real question faced in daily practice is, "Is this a difficult airway?" If not, it is handled in a routine fashion as preferred by the individual.
If it is deemed to be difficult (based on a nonreassuring airway examination, an awkward environment, poor patient condition, etc), an awake intubation procedure may be indicated depending on the judgment of the airway practitioner. There are a number of considerations that will inform and influence this decision.
- If direct laryngoscopy is deemed likely to be difficult, is the airway practitioner skilled in an alternative technique that is likely to be effective in the situation, or is the skill set limited to direct laryngoscopy? If the latter statement most accurately describes the situation, then awake intubation is likely the most prudent course. If the former statement most accurately describes the case, consideration may be given to induction of anesthesia, with or without muscle paralysis, followed by tracheal intubation using an alternate strategy, provided there is no anticipated difficulty in ventilation using BMV or an EGD.
- Is there a need to protect the airway from gastric contents? If so, it should be recognized that the ability to protect the airway with cricoid pressure is limited;44-51 and that multiple attempts at direct laryngoscopy over a prolonged period of time are associated with regurgitation and aspiration.23 The combination of difficult laryngoscopy and a full stomach in a cooperative patient may best be managed with an awake intubation (see Chapters 3 and 5).
In the event the patient is unresponsive or near death, a crash intubation is indicated and the Crash Algorithm is employed. "Unresponsive" means that the patient does not respond adversely to oral laryngoscopy (the newly dead or nearly dead).
Failure to meet the criteria for a crash intubation does not mean that the intubation is not an emergency. Intubation is urgently indicated in the event when a patient is unable to:
- Maintain reasonable oxygenation
- Protect the airway
- Maintain the airway
- Is faced with intubation to manage some other condition, or neuromuscular blockade is to be instituted.
Once the decision is made that this is an urgent or emergency intubation, the next question is "Will this be a difficult intubation?" This decision must be made quickly, and Chapter 1 presents efficient strategies for assessing the airway quickly for difficulty. If the urgent/emergency intubation is not judged to be difficult, a Rapid Sequence Induction/Intubation (RSI) is indicated as the method most likely to rapidly and safely secure the airway.
In the event the airway is judged difficult, the Emergency Difficult Airway Algorithm should be employed. Should any of these approaches fail, the Failed Airway Algorithm is used to rapidly and definitively gain control of the airway.
Four algorithms emerge from this conceptual approach to the airway and its management:
Difficult Airway Extubation Algorithm.
2.5.3 the Crash Airway Algorithm
Entry at this point requires an unconscious, unresponsive patient with immediate need for airway management. The first step in the crash algorithm is to attempt oral intubation immediately by direct laryngoscopy without pharmacologic assist. If the oral intubation is successful, then the practitioner proceeds with postintubation management. If oral intubation is not initially successful with direct laryngoscopy, then a decision point is reached and several questions must be asked.
220.127.116.11 Is BMV Successful?
If BMV is successful, then one has time and further attempts at oral intubation are possible. If BMV is difficult and one is certain in this unresponsive patient that an EGD such as an LMA would resolve the issue, it may be reasonable to try it.
In the event that BMV is unsuccessful in the context of a failed oral intubation with a crash airway, then a failed airway is present. BMV should be optimized with the use of oral and nasal airways and include maneuvers such as jaw thrust, chin lift, or a head tilt if appropriate. A two-hand mask hold may improve mask seal. Additionally, if cricoid pressure is being applied, consideration should be given to relaxing the force being applied or temporarily discontinuing it and assessing airway patency in its absence. One further attempt at intubation may be indicated, but no more than one, because intubation has failed and the failure of BMV places the patient in serious and immediate jeopardy. This is a CICV situation, and in such circumstances, the Failed Airway Algorithm (Figure 2-6) mandates immediate surgical airway management. If surgical airway management is not immediately possible, temporizing methods, such as the placement of an EGD (eg, LMA or Combitube™), should be attempted, but such attempts should not delay preparation for, and the creation of, a surgical airway. The successful use of an EGD in permitting adequate gas exchange may obviate the need for a surgical airway.
18.104.22.168 Is the Patient Completely Relaxed and Flaccid?
During the first attempt at orotracheal intubation in the unconscious, unresponsive patient, the patient is assessed for degree of relaxation to permit intubation. If the impression is one of absolute, complete skeletal muscle relaxation, then further intubation attempts are indicated. If the patient is felt to be exhibiting any resistance whatsoever to intubation, then a single dose of succinylcholine, 2.0 mg·kg−1, should be given and oral intubation attempted again. Usually, only one dose is indicated. It should be noted that this dose of succinylcholine is higher than the 1.0 to 1.5 mg·kg−1 recommended elsewhere. However, there is compelling evidence that excellent intubating conditions are achieved in virtually 100% of patients at 60 seconds with 2 mg·kg−1 of succinylcholine.19
22.214.171.124 Have There Been Three Attempts at Intubation by an Experienced Airway Practitioner?
If the answer to this question is yes, then consistent with the definition above, the situation represents a "failed airway" (Figure 2-6). The futility of further attempts may be evident after the first attempt dictating an immediate move to a different device or technique. If fewer than three attempts have been made by an experienced airway practitioner, and it is the opinion of the practitioner that it is possible to be successful by this route, a repeat attempt at oral intubation is justified. No more than three attempts at direct laryngoscopy can be supported,42 and some would say two.1,23
As detailed above, the evidence suggests that there is a low likelihood of success with persistent use of the direct laryngoscope after three failed attempts and an increased likelihood of patient morbidity and cardiac arrest. Between each intubation attempt, defined by a single laryngoscopy, the patient should receive ventilation and oxygenation through a bag-mask.
126.96.36.199 Is It Appropriate to Repeat Laryngoscopic Intubation until Three Attempts Have Failed?
As stated above, it is often apparent after a single attempt that further attempts at orotracheal intubation will be futile. In such cases, move to Plan B if oxygenation can be maintained, the Failed Airway Algorithm if it cannot be maintained.
188.8.131.52 Were Repeated Efforts Successful?
If intubation is achieved, then proceed to postintubation management; if not, cycle back to make another attempt or to proceed to the failed airway algorithm, depending on the number of attempts which have already been made. The failure of three attempts indicates a very low likelihood of ultimate success with oral intubation. There is a diminishing return with subsequent attempts and an increased risk of hypoxia, aspiration, and cardiac arrest. After three attempts, efforts to ensure oxygenation should be the priority while preparations are being made to perform a surgical airway.
184.108.40.206 Postintubation Management
This is undertaken in the event of a successful intubation.
2.5.4 the Emergency Difficult Airway Algorithm
This algorithm (Figure 2-5) is specifically designed to guide airway management in an emergency. Decisions are binary by design. It incorporates the notion of the failed airway. Though a fairly busy-appearing figure with 13 boxes, in reality it simply poses a series of four simple questions:
Is the airway difficult (MOANS, LEMON, RODS, and SHORT)? (See Sections 1.6.1-1.6.4.)
Do I have time (is the oxygen saturation within a normal range)? Or can I make time (with BMV)?
On reconsideration, is an RSI technique reasonable?
Failing that, what is my best option?
Bear in mind that patients presenting in an emergency should almost always be considered having a full stomach.
220.127.116.11 Is a Difficult Airway Predicted?
If, for whatever reason, airway management is predicted to be difficult, nothing should be taken from the patient that the airway practitioner cannot replace. This refers particularly to the administration of paralytic drugs. Furthermore, the ability to protect the airway with cricoid pressure is limited, and multiple attempts at laryngoscopy over a prolonged period of time have been associated with regurgitation and aspiration.23 Therefore, careful consideration should be given to awake intubation in the setting of dual concerns of difficult airway and full stomach.
18.104.22.168 Is BMV or EGD Ventilation Predicted to Be Successful (MOANS and RODS)? (See Sections 1.6.1 and 1.6.3)
In other words, if intubation fails, will BMV or rescue with some other device (commonly an EGD) be possible? These are the only other airway methods possible aside from a surgical airway. So careful consideration is warranted and one must have a high degree of certainty that this question is answered in the affirmative, particularly if the use of one of neuromuscular blocking (NMB) drugs is contemplated. Planning for and being prepared to undertake rescue maneuvers (Plans B and C) are crucial, as is the preemptive evaluation for difficulty. For example, if one is planning to perform a rapid cricothyrotomy (Plan B) should induction and paralysis (Plan A) fail, then an evaluation for difficult cricothyrotomy must be performed (SHORT, see Section 1.6.4) before embarking on Plan A.
22.214.171.124 Is Intubation Deemed Reasonably Likely?
The decision to proceed with an RSI technique in the patient with a predicted difficult airway must be associated with the likelihood that it will be successful. Airway practitioners must be confident in their abilities and must possess a broad array of equipment and skills to rescue the airway in the event that conventional direct vision orotracheal intubation fails.
126.96.36.199 Should an Awake Look Employing Topical Anesthesia and Sedation Be Attempted to Assist in Decision Making?
A variety of techniques are available to obtund the airway, the patient, or both, without burning any bridges. The condition of the patient and the clinical situation will dictate the aggression of this maneuver (ie, how much does one need to see?). It may be that the airway practitioner simply needs to verify that the epiglottis is in the midline to make the decision to back off and move to a rapid-sequence technique. At other times, it may indicate that an awake intubation is appropriate.
The value of the awake look as a maneuver to reassure oneself that oral intubation is likely to be possible following the administration of induction and NMB medications ought to be tempered by the findings of Sivarajan and Fink.52 These authors measured the position of larynx in lateral radiographs of necks taken in human volunteers when they were awake, and after the induction of general anesthesia with muscle paralysis. They found that the hyoid bone and epiglottis shifted anteriorly and the vestibule of the larynx enlarged with the onset of general anesthesia and muscle paralysis. In addition, the larynx also stretched longitudinally with wide separation of the vestibular and vocal folds. The authors concluded that consciousness is associated with tonic muscular activity that folds the larynx and partially closes it and that onset of general anesthesia and muscle paralysis widens the larynx and shifts it anteriorly. This may make visualization of the larynx difficult during direct laryngoscopy in some patients. Remember: bad things sometime happen with induction after successful awake looks.
2.5.5 the Failed Airway Algorithm
The failure to intubate is rarely accompanied by the failure to ventilate and oxygenate. This situation has variously been termed CICV or "can't intubate, can't oxygenate" (CICO), the latter being the more precise term. It is a clinical emergency of such magnitude that it leads to neurologic compromise and death if not rectified rapidly. Decisive action in selecting a technique most likely to lead to a secure airway (ie, an emergency surgical airway) is essential to success in such a situation. It cannot be overemphasized that a failing technique (eg, direct laryngoscopy) cannot be considered as an appropriate salvage technique and there is no defence for persistent attempts with a failing technique.
Most often the failure to intubate is associated with some degree of success with BMV oxygenation, giving the airway practitioner time to consider alternative techniques. This CICV/O situation is amenable to nonsurgical rescue techniques. In this scenario, practiced alternatives to the direct laryngoscope such as the lighted stylet, or a rigid or flexible endoscope, may be used or an EGD may be placed to provide a more secure, bridging airway. In the latter case, these EGDs may be used to facilitate intubation (eg, LMA-Fastrach™, Cook ILA) or provide time to prepare for a more definitive solution (surgical airway).
The Failed Airway Algorithm is presented in Figure 2-6. The essential message from this algorithm is that the decision to move to a surgical airway must be taken early once the failure to maintain oxygenation is recognized. Wasting valuable time attempting a variety of devices or techniques is to be avoided at all costs, unless it is while the practitioner is concurrently preparing to perform a surgical airway. There is little or no value at this time in making attempts with tools or techniques with which the practitioner has no experience.
188.8.131.52 Have Failed Airway Criteria Been Met?
This is the entry point to the Failed Airway Algorithm. The criteria are either three failed attempts at intubation via oral laryngoscopy by an experienced practitioner or a single failed attempt at oral intubation with inability to maintain SpO2 ≥90% using a bag-mask. A mandated intubation in a patient with a difficult or crash airway in whom BMV has failed represents a failed airway. As with the difficult airway, it is advisable to call for assistance when a failed airway has occurred.
184.108.40.206 Is BMV Possible and Adequate?
In the circumstance of a failed airway, if BMV is not adequate, then immediate cricothyrotomy is mandatory. Simultaneously with preparations for a cricothyrotomy, the immediate placement of an EGD is attempted. If successful in rescuing the airway, cricothyrotomy may be averted.
Further attempts at intubation or use of alternate devices will merely prolong the patient's hypoxemic state. If surgical airway management is itself relatively contraindicated (in a life and death situation all contraindications to cricothyrotomy are relative), then alternative methods may be tried first. For example, if the patient has known laryngeal pathology in the area of the anticipated surgical intervention, such as a tumor or hematoma, then alternative techniques may be preferred. However, if these methods are not immediately successful, cricothyrotomy should be performed, even in the presence of relative contraindications. SHORT (see Section 1.6.4) identifies conditions that present difficulty and should not be thought of as contraindications.
220.127.116.11 Consider Combitube™, Flexible Endoscopes, I-LMA, Lighted Stylet, trans-Tracheal Jet Ventilation, Retrograde, Rigid Video-Optic Devices, or Some Other Method
If ventilation and oxygenation by bag-mask can maintain acceptable SpO2 values (≥90% or some acceptable number), then a number of different devices and procedures may be attempted to rescue the patient with the failed airway. At all times, the patient must be monitored for adequate oxygenation. If oxygenation becomes inadequate at any time and cannot be restored via BMV, then cricothyrotomy is mandatory. Likewise, if there is failure of each of the techniques considered appropriate, then cricothyrotomy should be undertaken. Videolaryngoscopic (eg, the Glidescope®, Storz C-MAC) and flexible endoscopic methods, and the rigid video laryngoscopes (eg, Shikani, Bonfils, Bullard) have all been shown to be effective and safe rescue techniques. The choice of the tool should be governed primarily by the practitioner's experience and expertise. The application of a tool with which the practitioner has little experience is difficult to defend as a prudent intervention.
18.104.22.168 Enough Time for Successful Airway Rescue?
If there is sufficient time to achieve oxygenation and ventilation using one of these devices or techniques, proceed down the main path of the algorithm. If not, cricothyrotomy is mandated.
22.214.171.124 Was an Endotracheal Tube Placed?
If an endotracheal tube is successfully placed at any time, postintubation management may be undertaken. If another method of gas exchange (eg, EGD) has been employed successfully, then the airway should be considered to be temporary at best and arrangements for a definitive airway be made. If the airway placed is unable to provide adequate ventilation and oxygenation, then immediate cricothyrotomy is indicated.
2.5.6 the Extubation Algorithm
The Extubation Algorithm (Figure 2-7) is specifically intended to be employed in those situations in which reintubation, if needed, is judged to be difficult or impossible (eg, the patient was initially intubated awake because intubation was judged to be impossible).53,54 At the core of the algorithm is a trial of extubation over a tube exchanger (TE) (eg, Cook Endotracheal Tube Exchange Catheter). It needs to be emphasized that the airway practitioner needs to be absolutely certain that patient is awake and cognitively responsive before removing tube in a difficult extubation setting! Agitation is not responsiveness.
It is important to note that a failure to reintubate should be immediately followed by an assessment of the ability to maintain oxygen saturations. If oxygen saturation can be maintained by some form of ventilation through the catheter or by BMV, there is likely some time to use alternative methods of intubation, such as lightwands and flexible bronchoscopes. On the other hand, the failure to maintain oxygen saturation should be immediately followed by attempts to employ rescue devices such as a Combitube™, intubating laryngeal mask, and trans-tracheal ventilation while preparations are undertaken to perform a surgical airway.