THE CLINICAL CHALLENGE
Extubation is an uncommon procedure in emergency medicine. However, certain scenarios, such as a rapidly recovering polysubstance overdose patient may make extubation desirable. The fourth National Audit Project found that nearly one-third of reported major airway complications occurred at extubation, which has led the Difficult Airway Society guidelines (see Evidence section). Although these guidelines focus on perioperative medicine, many of the principles of a comprehensive planned approach to extubation apply.
With the changing scope of practice, emergency medicine physicians may be involved increasingly in the process of extubating patients. The recognition of the potentially difficult extubation, creation of an extubation strategy, and execution of a safe extubation procedure are all important elements that emergency physicians should be familiar with.
Although extubation is a vital component in airway management, it receives significantly less attention than endotracheal intubation. A recent Medline search comparing the ratio of intubation to extubation articles found the ratio to be 57:1. The same meticulous planning and communication involved with endotracheal intubation should also be practiced with removal of the endotracheal tube (ETT). Similar to intubation, recognition of the potentially difficult extubation is instrumental in the planning process. Despite these important factors, the body of literature on extubation is significantly less comprehensive than intubation. On a positive note, this deficit in the literature is an opportunity for extubation research and publication, especially in emergency medicine.
PLANNING FOR EXTUBATION
A morbidly obese 55-year-old restrained driver is brought into the ED from a single-passenger, single-vehicle incident 30 minutes prior during severe winter weather. He was intubated in the field because of decreased level of consciousness. Four attempts using both direct and video-based laryngoscopy were required prior to intubation success secondary to a cervical collar, short neck, and redundant soft tissue.
• FIGURE 42-1. Intubated morbidly obese 55-year-old restrained driver brought into emergency department.
CT scan reveals a single lung contusion but no flail segment or other significant injuries. The patient’s hemodynamics are within normal limits and aside from a high blood alcohol level, initial and repeated blood work results are stable. It is now 8 hours after the incident and the patient remains in the ED. He is responsive to command, moving all extremities, and is becoming more agitated. He now requires 4-point restraints in addition to escalating doses of sedation. His tongue is large and bruised. Some bruising was noted over the anterior chest on secondary survey. A total of 2 L of crystalloid has been infused, but no blood products. An arterial blood gas on minimal vent settings (pressure support with an FIO2 of 30%) shows a PO2 of 100 mm Hg, O2 saturation of 98%, PCO2 of 43 mm Hg.
The nurses would like to know if you would like to extubate him, or continue to escalate his sedation (Fig. 42-1). How should you proceed?
EXTUBATION CRITERIA
Fortunately, there are defined general principles to follow when considering a patient for extubation. Unlike intubation, extubation is always an elective procedure. In a busy ED environment, there are always the pressures of time and bed-space. It is helpful to have a written “checklist approach” to allow bedside nurses and other health care workers to assess a patient’s readiness for extubation prior to physician attendance for the final decision making. Table 42-1 highlights minimal recommendations to consider when evaluating a patient for extubation. Some institutions have implemented evidence-based checklists and have reduced the incidence of extubation failure. Having a consistent, predictable approach should be the overall goal of the airway provider and emergency system.
RISK STRATIFICATION
Once the decision to extubate has been made, focus shifts to the identification of which airways may be at increased risk. The Difficult Airway Society recommends risk-stratifying of patients into low risk vs. high risk of extubation failure (see Tables 42-2 and 42-3). This helps to narrow the focus to the at-risk group in order to identify those patients who require additional planning. Some of the general risk factors that are highlighted in the at-risk group for extubation are listed in.
Special attention should be placed on the airway risk factors section because this can be difficult to identify prior to extubation. Interventions since intubation, such as extensive fluid resuscitation, may have resulted in airway edema and could predispose the airway to extubation failure because of obstruction. Anticipated course of disease also plays a role; burns or infection to the face or neck may be more difficult to reintubate than initially recorded.
Extubation Criteria |
Reversal of underlying process | ■ No further need for mechanical ventilation identified ■ No expected need in immediate hospital course |
Level of consciousness | ■ Alert patient ■ Sedation medications discontinued |
Ability to oxygenate | ■ Spontaneous breathing ■ Tidal volume > 5–7 mL/kg ■ SpO2 > 92 with FIO2 30 |
Ability to ventilate | ■ PEEP < 8 mm Hg ■ Peak voluntary negative pressure >20 cm H2O |
Predictors of impending airway loss | ■ Protecting own airway ■ Reversal of neuromuscular blockade (TOF > 90) ■ PEF > 60 L/min (cough assessment) ■ Difficult intubation? ■ Difficult bag-mask ventilation? |
Pulmonary secretions | ■ Oropharyngeal secretions minimal ■ Risk of aspiration minimal |
DAS Risk Stratification |
Low risk | ■ Fasted? ■ Uncomplicated airway ■ No general risk factors |
At risk | ■ Ability to oxygenate uncertain ■ Reintubation potentially difficult ■ General risk factors (Table 42-3) |
From Mitchell V, Dravid R, Patel A, et al. Difficult Airway Society Guidelines for the management of tracheal extubation. Anaesthesia. 2012;67(3):318–340.
General Risk Factors |
Airway risk factors | ■ Known difficult airway ■ Airway deterioration (trauma, edema, bleeding) ■ Restricted airway access ■ Obesity/OSA ■ Aspiration risk |
General risk factors | ■ Cardiovascular ■ Respiratory ■ Neurologic ■ Metabolic ■ Special surgical requirements ■ Special medical requirements |
Failure of extubation is usually due to one of two issues, or both: upper airway obstruction or respiratory failure. Upper airway obstruction, including laryngospasm, is associated with immediate respiratory distress and hypoxia. On the other hand, respiratory failure, or a gradual decline in the ability of the patient to breathe on his/her own without support, is a much more common issue in the ICU. Immediate upper airway collapse and obstruction is more common in the postoperative setting than in the ICU, but gradual respiratory failure remains the most common cause of the need to reintubate the patient. In emergency medicine, the characteristics of patients failing extubation are unknown.
ADDITIONAL TESTING
If a patient is identified as having an at-risk airway, the emergency physician must first decide whether extubation should even be attempted in the ED. If extubation remains part of the plan after taking into consideration the patient’s high-risk features, intubation history, and availability of difficult airway tools and specialty support, then additional testing may be needed in order to determine whether conditions are safe enough to extubate. If suspicious for the possibility of upper airway obstruction, a cuff leak test may be performed (see Box 42-1). What does a cuff leak, or lack thereof, really predict? A cuff leak test predicts postextubation stridor in children intubated for croup. Cuff leak does not necessarily predict success of extubation, but can be used with a number of other criteria to judge the likelihood of success (see Evidence section). Adding to this is the use of the terms “negative” and “positive” cuff leak test. Both terms have been used when there is a cuff leak present, and when there isn’t, creating confusion. The authors believe the terms positive and negative should be abandoned. Communicating that a cuff leak is present or absent is much clearer.
Cuff leak test.
What is the Cuff Leak Test? The cuff leak test is used to predict the population that may be at increased risk of postoperative stridor. It is a measurement of the cuff leak volume, which is equal to the difference between the inspiratory tidal volume and the average expiratory tidal volume while the cuff around the endotracheal tube is deflated.
How is it performed? There are variable methodologies described in the literature. The most common is to set the assist control mode with the fixed tidal volumes of 10 to 12 mL per kg. The inspiratory tidal volume with the cuff inflated is then measured. The cuff is then deflated and a brief period of coughing usually proceeds. Following the resolution of coughing, four to six breaths are given, and the average value of the three lowest expiratory tidal volumes is computed. The difference between the inspiratory tidal volume with the cuff inflated and the averaged expiratory tidal volume with the cuff deflated is used to calculate the cuff leak volume.
Application to practice: The cuff leak volume of <130 mL is generally accepted as indicating a cuff leak is absent (positive test) and places the patient at risk for postextubation stridor and extubation failure. The absence of a cuff leak should therefore alert the airway manager to the potential for a postextubation complication and a plan should be devised accordingly.
An absent cuff leak should alert the airway manager to the potential for postextubation stridor and, therefore, the potential for airway obstruction. The airway can be evaluated by direct laryngoscopy, videolaryngoscopy, or nasopharyngoscopy. Nasopharyngoscopy can be achieved with pediatric bronchoscope or nasopharyngoscope and 3 to 4 sprays of 4% lidocaine nasally. If nasopharyngoscopy is chosen, the patient should be sitting up and asked to flex his or her neck forward (“like a chicken”) to maximally open the hypopharyngeal space and allow for best visualization. The ETT cuff can be deflated, and breathing around the ETT can be assessed by direct inspection. Videolaryngoscopy has the advantage of creating a “shared mental model,” with health care professionals taking care of the patient being able to also visualize the airway. Topicalization of the posterior pharynx including the vallecula is usually required for either video or direct laryngoscopy. Sedation may also be required. Assessment of cough can also be completed by performing a peak expiratory flow. Values of less than 60 L per minute have been associated with an increased incidence of extubation failure.
PROCESS OF EXTUBATION
General Extubation
Extubation is an elective procedure that should be planned and prepared well. Overall, the goal should be maintenance of oxygenation, maintenance of ventilation, and a well-laid-out plan in the event extubation failure occurs. An awake, spontaneously breathing patient can accomplish several of the overall goals during extubation independently. They are able to protect their airway, maintain patency with muscular tone, and facilitate gas exchange with spontaneous breathing. This is significantly different to the heavily sedated patient. For this reason, extubation is generally recommended in an awake state. This corresponds well with the extubation criteria highlighted in Table 42-1. The general process of extubation in a low-risk situation follows the stepwise process described in Table 42-4.
Complications
The majority of low-risk extubation procedures are completed without significant complications. However, vigilance during this period of transition from a controlled situation is imperative as hypoxic insults are not uncommon during this time. This was further highlighted by the fourth National Audit Project from the United Kingdom where approximately one-third of the major airway incidences occurred at extubation (Evidence section). Complications that can occur during extubation are listed in Table 42-5. A component in the planning process for extubation is to mitigate the risk factors that lead to complications. Even with the low risk, one should still be able to handle the complications of extubation should they occur (Box 42-2 and Table 42-6).
General Steps |
1. Extubation criteria met (Table 42-1) |
2. Deliver 100% oxygen |
3. Suction of airway |
4. Insert soft bite block |
5. Position patient with head up |
6. Untie/tape tube |
7. Deflate cuff |
8. Apply positive pressure while removing ETT |
9. Transfer to facemask |
10. Confirm continued ventilation/oxygenation |
Extubation Complications |
Hypoventilation |
Upper airway obstruction |
Laryngospasm (Box 42-2) |
Bronchospasm |
Vocal cord damage |
Negative pressure pulmonary edema |
Pulmonary aspiration |
Coughing |
Hemodynamic alterations (tachycardia, hypertension, dysrhythmias, ACS) |
ADJUNCTS TO EXTUBATION
Airway Exchange Catheter
Patients deemed at high risk of extubation failure may require adjuncts added to the airway plan. A common technique is the use of an airway exchange catheter (AEC) for maintenance of continuous access to the airway. AECs are thin, hollow tubes with a blunt end located distally. They are supplied with a 15 mm connector compatible with a breathing circuit as well as a luer lock connectors for high-pressure (jet) ventilation (Fig. 42-2). The most commonly available AECs are made by Cook Medical (Bloomington, Indiana, www.cookmedical.com). The Cook 11F and 14F AECs are commonly used in adults, are tolerated well in the awake patient, and are compatible with ETTs with internal diameters greater than 4 mm and 5 mm, respectively; 19F AECs are also available, but are only tolerated in awake patients 50% of the time and depends on keeping the tip of the AEC above the very sensitive carina. Therefore, the numbers on the AEC should be aligned with the ETT numbers accordingly. No lidocaine is required through or around the AEC as this has not been shown to increase tolerance of the device. Patients can phonate with an 11F or 14F AEC in place. The method for using an AEC is highlighted in Table 42-7 and Figure 42-3.
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