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15.

DIFFICULTAIRWAY

Romina G.Ilic

CASE SCENARIO

A 48- year- old obese man is seen in the emergency department for sore throat, excessive salivation, and diculty swallowing. Physical exam reveals a portly man sitting upright breathing comfortably with excess salivation. Further imaging reveals he has a pharyngeal abscess. He is able to open his mouth with minimal tongue extrusion. Plan is for intubation and surgical drainage in the operating room.

PATIENT EVALUATION

Advance knowledge of a past dicult airway is helpful in allowing the practitioner to devise an approach that is modied from a standard intubation setup for the challenging task ahead. Atargeted patient assessment, with particular attention to the airway exam and complicating factors is vital (Box 15.1). Used together, these ndings can indicate the need for advanced airway management.3 e exam is somewhat dependent on patient cooperation, which may be problematic in the emergent setting, where patients may be obtunded or uncooperative. Of particular importance is

DIFFICULT AIRWAY ALGORITHM

identifying the patient who may present as a dicult mask

ventilation or supraglottic airway (SGA) device placement, e clinical scenario in which a practitioner is caring for a patient with a dicult airway can be a daunting experience. Adicult airway is a case in which there is diculty in bag mask ventilation, laryngoscopy, and tracheal intubation, or requiring an emergent surgical airway (cricothyrotomy). Multiple factors can contribute to this, including patient- related factors, the clinical context, and the experience of the practitioner. e initial American Society of Anesthesiology (ASA) closed claims analysis in 1990 showed that 34% of adverse anesthetic events were respiratory in origin. Inadequate ventilation was found in 38% of cases, while esophageal intubation and dicult intubation were noted in 17% and 18% of cases, respectively.1 A2005 closed claims analysis also showed that 67% of dicult airway claims arose during induction, and emergency airway management was associated with higher risk of mortality or disability.2 In 1993, the ASA Task Force on Management of the Dicult Airway published the dicult airway algorithm along with a set of practice guidelines based on literature review and expert opinion (Figure 15.1). It outlined some key elements in identifying the challenging airway and provided a systematic approach to obtaining airway access. e ASA practice guidelines were updated in 2013 with additional supportive data, however the algorithm has remained unchanged.

as these are basic techniques that are critical in maintaining

oxygenation and ventilation in scenarios where direct laryn-

goscopy (DL) has failed and alternate methods of securing

the airway are attempted (Box15.2).

An evaluation of the upper airway includes noting the size of the tongue, pharyngeal space, and extent of mouth opening (i.e., Mallampati classication), paying special attention to the interincisor distance. Asmall mouth opening may limit the space available for blade insertion or SGA positioning, while a large tongue and excess so tissue may obstruct airow during mask ventilation. Identify loose teeth, removable dentures, and presence of a prominent overbite. Assessment of the anterior mandibular space, or thyromental distance, and degree of voluntary mandibular protrusion will help determine extent of mandibular displacement during DL. In addition, examining the neck for mobility and girth will determine whether special positioning is required to obtain proper extension of the atlantooccipital joint in order to visualize the vocal cords (i.e., ramping up the shoulders). Blood or vo mitus in the airway is an important nding, as this may make visualization with video- assisted devices or beroptics challenging. If the need for a surgical airway arises, complicating factors include a large neck, previous neck or tracheal surgery, and radiation or trauma to thearea.

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Figure15.1 ASA difcult airway algorithm. Reprinted with permission.

Along with patient assessment, an evaluation of available resources should be conducted. Basic airway devices, oxygen (O2) supply, suction, and end- tidal capnography should be at hand prior to induction. Adjunct or advanced airway devices should also be readily available. Asecond provider should be at the bedside for assistance with bag mask ventilation, device management, or for a second look (if qualied). Ensure video- assisted devices are functional and ready

DIFFICULTAIRWAY 127

for use, and inform surgical colleagues that their assistance may be required if there is high suspicion for a challenging surgical airway. e ASA guidelines for dicult airway management recommend a portable storage unit with all airway assist devices included in order to avoid dispatching personnel and causing a delay while waiting for equipment.4 e SGA plays an important role in the dicult airway algorithm and should be available in dierentsizes.

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saturation values and increase the time until desaturation

BOX 15.1 PREINTUBATION PATIENT ASSESSMENT

Evaluation of the Upper Airway:

during intubation. vital capacity breaths with 100% supplemental O2 in 1 min

5,6

In a pinch, asking the patient to take 8

can provide similar benets.7 is is particularly important

– Size of tongue and pharyngeal space (i.e., Mallampati

classication)

– Dental exam— relation of maxillary and mandibular

incisors during normal jaw closure (overbite), interincisor

distance, removable dentures

during emergency situations where time for preparation is minimal.

e information gathered during patient assessment, resource availability, and degree of urgency should guide decision- making and the plan of approach. While the most expeditious means of securing an airway is a rapid

Anterior mandibular space (Thyromental distance)

Length and thickness of theneck

– Degree of neck extension and exion

sequence intubation (RSI), this may not always be the safest approach. For example, in patients with severe angioedema, relaxation of upper airway muscles may make visualization and intubation more dicult, therefore spon-

History:previous difcult intubation, obstructive sleep apnea,

radiation to face/ neck, cervical spine surger y, congenital dis-

ease with known difcult airway (i.e., Treacher- Collins, Pierre

Robin, Down syndrome)

Clinical context:emergent nature, trauma (airway distortion,

blood, C- spine immobilization), angioedema, Ludwig’s angina

taneous ventilation is an important asset. Similarly, postradiation changes, cervical spine fusion, or neck pathology causing anatomic distortion (i.e., tumor compression) can cause tissue to become immobile and may make DL more challenging.

If DL is deemed appropriate, initial blade selection should be based on the practitioner’s experience and comfort. Dierent sized endotracheal tubes (ETTs) should

BOX 15.2 PATIENT CHARACTERISTICS INDICATING

POTENTIAL DIFFICULTAIRWAY

be available in case of stenotic or edematous airways. It is important to remember that multiple attempts may cause airway edema and bleeding, which can worsen visualization

Relatively long upper incisors, maxillary incisors anterior to

mandibular incisors (prominent overbite)

and complicate further attempts. With increasing airway edema or bleeding in a patient who was previously easy to mask, ventilation may become dicult, resulting in a “can’t

Patient cannot bring mandibular incisors anterior to

maxillary incisors (prognathism)

Interincisor distance with maximal mouth opening of less

than3cm

intubate, can’t ventilate” scenario.

If obtaining an adequate view is dicult, an ETT guide or lighted stylet can be helpful (Figure 15.2). Introducers such as a gum elastic bougie (Eschmann) or Frova intubating catheter (Cook Medical) can be passed to instrument

Mallampati class>II

High arched or very narrowpalate

the trachea, allowing an ETT to be placed over the catheter. e bougie, a rigid stylet with an angled tip, helps to guide the ETT upward during intubation and can give tactile con-

Submandibular space stiff, indurated, edematous

Thyromental distance less than 3 ordinary nger breadths

rmation of the tracheal ridges on advancement. Abenet to the Cook catheter and some other guiding catheters is connectivity to an anesthesia circuit and O2 supply.

Short, thickneck

Patient cannot touch tip of chin to chest or cannot ex or

extend theneck

FOI is a valuable adjunct and is especially helpful in the patient with a small or limited mouth opening, or an immobile cervical spine. An ETT can be loaded over the bronchoscope (aer removing the ETT adaptor rst, if necessary).

INTUBATIONPLAN

AWilliams or Ovassapian oral airway is inserted into the mouth to guide the scope past the upper airway and toward the larynx. Once a view of the vocal cords is obtained, local

Preoxygenation is a critical and oen overlooked step in preparing for intubation. Studies have shown that 3 minutes of preinduction oxygenation will maintain higher O2

anesthetic may be introduced via the injection port of the scope to topicalize the vocal cords and reduce coughing. e tip of the scope should be advanced past the cords,

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Figure15.2 Trachlight lighted stylet

with endotrachealtube.

and tracheal rings should be observed to conrm the scope did not slip into the esophagus during advancement. e ETT can then be advanced over the scope into the trachea. End- tidal CO2 should be conrmed and any adjustment of depth can be made under direct vision.

Video laryngoscopy has become a popular means of airway management. Benets include improved visualization of the vocal cords with minimal cervical spine displacement and ability for others to appreciate the view of the operator while assisting or teaching. Several varieties of video laryngoscopes such as the Glidescope (Verathon Medical), C- MAC blade (Karl Storz), and McGrath MAC (Aircra Medical Ltd.) are available. ey are helpful in patients with excess so tissue of the pharynx and limited neck mobility. Patients with a small mouth opening may benet from a smaller prole blade such as the McGrath, which can also be disarticulated from the handle and placed in the mouth rst, then reattached. One drawback to the video laryngoscope is its reliance on a “clean” airway; increased secretions, bleeding, and vomitus make visualization dicult. Care must be taken in placing a rigid stylet into the oropharynx to avoid airway injury. e ETT and stylet should be observed entering the oropharynx near the blade slowly until the tip of the ETT is seen on the video monitor.

In the case where intubation is unsuccessful, an SGA device can be placed, allowing for gas exchange by displacing the so tissues of the oropharynx. ese devices can also serve as a conduit for ETT placement. Several options will allow for both ventilation and intubation. In addition, ETT guides, such as the Aintree intubating catheter (Cook Medical) can be used to facilitate intubation via SGA by creating a single entity (ETT, Aintree catheter and

beroptic scope) to be introduced through the SGA into the trachea. Many also have a gastric channel allowing for passage of an orogastric tube. e SGA can also be the primary means of airway management, especially in emergent settings. For example, an intubating LMA (LMA Fastrach, Teleex) (Figure 15.3) can be used as a stand- alone supraglottic airway as well as an intubating device. Arigid SGA, it can be inserted with minimal movement of the head and neck, a benet in the immobilized C- spine.

If awake intubation is deemed necessary, achieving adequate anesthesia is critical. Options include sedation with IV medications that support spontaneous respiration such as midazolam, dexmedetomedine, or ketamine. As ketamine can cause increased oral secretions, glycopyrrolate is oen administered rst as an antisialagogue. Fentanyl in small IV doses (25– 100 mcg ) can also be used for analgesia, however care must be taken not to depress respiratory eort. Local anesthetic can be applied via spray, nebulizer, or various solutions to the pharynx or nasal mucosa (for nasal intubation). Nebulization of lidocaine is a simple and comfortable way to prepare for airway instrumentation, but needs to be initiated 15– 30 minutes in advance. Cotton pledgets can be soaked with lidocaine and nasal trumpets lubricated with lidocaine jelly and then applied to the oral or nasal mucosa for several minutes. If nasal intubation is the preferred route, application of a vasoconstrictor such as phenylephrine nasal spray prior to topicalization and instrumentation can prevent mucosal bleeding and ensure limited systemic uptake of local anesthetic. Of note, local anesthetics can have diminished ecacy in edematous mucosa such as is found in angioedema. While a smaller- sized ETT may

DIFFICULTAIRWAY 129

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Figure15.3 LMA Fastrach.

pass more easily via the nasal passage, care must be taken to ensure the length is adequate for the balloon to reach past the vocalcords.

Airway nerve blocks are a helpful technique during awake FOI, but require some experience. Two commonly targeted nerves are the glossopharyngeal nerve and the superior laryngeal nerve. e glossopharyngeal nerve block is helpful in blunting the gag reex. Local anesthetic, approximately 2– 3 mL, is injected at the posterior tonsillar pillar bilaterally to anesthetize the nerve. Care must be taken to aspirate, as arterial injection into the carotid artery is possible. Asuperior laryngeal nerve block anesthetizes the larynx above the vocal cords. Local anesthetic, 1– 2 mL, is injected near the nerve as it emerges bilaterally, just inferior to the greater cornu of the hyoidbone.

Once the upper airway is anesthetized, a bronchoscope can be advanced via the Williams or Ovassapian airway to visualize the vocal cords. Local anesthetic can then be injected directly onto the false and true vocal cords, anesthetizing the region before the scope is advanced into the trachea. No one block supplies a complete anesthetic for awake intubation, so airway blocks and topicalization are frequently used in conjunction. A contraindication to blocks is anticoagulation or coagulopathy, but this may be relative in emergencies.

the option to wake up the patient and cancel the procedure. Unfortunately, this is not an option for emergency cases, those in which long- acting neuromuscular relaxation have been given, or in cases of inadvertent extubation where the ETT needs to be replaced. In this scenario, alternative means of securing the airway need to be expedited. If available, rigid bronchoscopy can be used as an intermediate means of ventilation, as the bronchoscope can be attached to a jet ventilator.

e fastest way to obtain access to the airway is by inserting a large- bore needle or angiocatheter (16 gauge or higher) into the airway and attaching to a high- ow O2 source at 15 liters per minute or jet ventilation. Care must be taken to identify the midline; arteries and veins lay to either side of the membrane. e needle is attached to a 3- or 5- mL saline- lled syringe and advanced while constantly aspirating for air (Figure 15.4). e needle should be inserted into the cricothyroid membrane, the tissue between the oen palpable thyroid cartilage and smaller cricoid cartilage. Once air is aspirated into the syringe, while stabilizing the needle with one hand, the syringe can be removed and the needle attached to high- ow O2. If a

7.5 ETT is available, the adapter can be disconnected from the tube and attached to a 10- mL syringe, which is then attached to the angiocatheter.9 is allows for attachment to a standard anesthesia circuit. is procedure only provides for oxygenation and a bridge to a denitive surgical

CAN’T INTUBATE, CAN’T VENTILATE

air way.

If all other airway management options have been exhausted, the nal step in the dicult airway algorithm

e most concerning airway situation is the “can’t intubate, can’t ventilate.” In the elective surgery setting, there exists

is obtaining a surgical airway. ere are several dierent methods described in the surgical literature which

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Figure15.4 Melker Emergency Cricothyrotomy kit. SOURCE:Reprinted with permission from Spiegel JE and Shah V.Surgical Management of the Failed Airway:AGuide To

Percutaneous Cricothyrotomy. 7th Annual Anesthesiology News Guide to the Airway Management. 2014– 2015;47– 51.

are beyond the scope of this chapter, as is the emergent management of the pediatric airway, which has certain implications. e most frequently performed emergent surgical airways are needle cricothyrotomy and surgical cricothyrotomy. Given these procedures are employed during emergent situations, it is not surprising that they are asso-

Since the decision to extubate is elective, care should be taken to have a comprehensive plan in place to support oxygenation and ventilation if needed. Prior to extubation, it is important to optimize conditions. Allowing sedation and neuromuscular blockade to wear o, ensuring the patient is taking adequate tidal volumes spontaneously and

ciated with high complication rates.10 When possible the cricothyrotomy should be performed by the most experienced provider.

Important complications to consider from cricothyrotomy are hemorrhage from nearby vessels, subcutaneous and/ or mediastinal emphysema, and trauma to nearby structures (vocal cords, larynx, esophagus, thyroid). As with other methods, if the airway is not secured in a reasonable amount of time there is signicant risk of hypoxic brain injury anddeath.

DIFFICULT TRACHEAL EXTUBATION

Approximately one- third of all adverse events related to anesthesia are during emergence and recovery.11 There are many reasons why a patient may not be able to maintain their airway post extubation, the most commonly encountered issues being upper airway obstruction, hypoventilation, ineffective airway reflexes, and hypoxemic respiratory failure (Box 15.3). Extubation failure is defined as the inability to tolerate the removal of an ETT, whereas liberation or weaning failure refers to the inability to maintain spontaneous ventilation without mechanical support.

12,13

Obesity, obstructive sleep apnea, and residual neuromuscular blockade may lead to postextubation failures in the recovery room, whereas in the intensive care unit multiple medical comorbidities, length of intubation, and sedation play a largerrole.

BOX 15.3 PATIENT CHARACTERISTICS INDICATING

POTENTIAL FOREXTUBATION FAILURE

Upper airway obstruction

Obesity

Obstructive sleepapnea

Airway edema, hematoma, vocal cord paralysis

Hypoventilation

Central nervous system disorders

Obesity

Neuromuscular disorders

Oversedation (medications, drugs, alcohol intoxication)

Ineffective airway reexes

Central nervous system disorders

Oversedation (asabove)

Hypoxemic respiratory failure

Pneumonia

ARDS,sepsis

Pulmonaryedema

Obstructive, restrictive lung disease

DIFFICULTAIRWAY 131

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maintaining oxygenation is imperative. Treating underlying medical pathology or active pulmonary disease (i.e., COPD, congestive heart failure, sepsis) will minimize the risk of reintubation. Patients with airway edema should be given ample time for the swelling to improve. If indicated, IV steroid treatments need to be administered at least 12 hours in advance of planned extubation. Acu leak is performed if there is any question of subglottic edema. is is done by deating the ETT cu and listening for an audible

familiarity with available airway devices, and a preestablished plan can make the dierence between a challenging airway and a well- executed intubation. While the dicult airway algorithm is helpful in the organization and stepwise progression of securing an airway, certain circumstances fall outside the realm of its guidelines. erefore, being able to identify the risks for a dicult airway and acquainting oneself with alternate techniques are key to

success in any setting. air leak. e absence of an air leak suggests swelling and should discourage extubation. Knowing what techniques were used to successfully intubate the patient is important, as these airway devices should be readily available as backup.

Several extubation techniques exist that attempt to avoid reintubation or make it easier if necessary. One common strategy is to keep the airway instrumented aer the extubation via an exchange catheter or stylet. For example, the Cook airway exchange catheter (Cook Medical), Eschmann introducer (SunMed), and Arndt exchange catheter (Cook Medical) can be placed through the ETT to midtrachea while the ETT is removed over the catheter. If the patient is maintaining an adequate airway, the catheter is then removed. Should this not occur, an ETT can be passed over the catheter into the trachea. Of note, if the patient requires oxygenation, using a mask or CPAP can still be performed with the exchange catheter in place. Some exchange catheters are hollow and allow for connection to an anesthesia circuit, Ambu bag, or jet ventilator. Caution needs to be exercised, as high pressures are required for O2 delivery via these devices, presenting a risk of barotrauma.

Supraglottic airway devices can serve as a bridge to extubation as well as reintubation. e Bailey maneuver involves placing an LMA behind the ETT prior to extubation while the patient is still sedated to avoid airway irritability on awakening.14 One can also use an exchange catheter to switch from an ETT to an SGA, such as with an LMA Classic or LMA Unique (Teleex), which can t a standard 7.0 ETT. If the patient shows signs of decompensation with an SGA device in place, an ETT can then be reinsterted with the use of a beroptic scope or an Aintree catheter, which allows the scope to be placed within the hollow of the catheter.

CASE- BASED LEARNING DISCUSSION

1. e patient in the case scenario was maintaining adequate oxygenation and was amenable to awake FOI; 0.2 mg of glycopyrrolate was administered IV. Time was taken to topicalize the upper airway with lidocaine nebulizer, followed by atomized lidocaine sprayed onto the so palate and base of tongue. What is the maximum dose of lidocaine that can be administered topically? Is that dierent from the maximum dose that can be administered intravenously? Subcutaneously? How does the metabolism of lidocaine that is administered below the vocal cords dier from the metabolism of lidocaine administered above the vocalcords?

2. Once the patient was able to tolerate a Williams airway, 2 mg of midazolam and 50 mcg of fentanyl were given via IV and the beroptic scope was inserted via the airway. What are the risks and benets of choosing this type of sedation? Would alternative medications be better? Which ones? Do you routinely draw up reversal agents if available? Why or whynot?

3. Aclear view of the vocal cords was obtained, and 2% lidocaine was sprayed onto the vocal cords via the scope. Propofol and succinylcholine were attached to the IV hub. Aer a minute, the scope was slowly advanced between the vocal cords in timing with the patient’s breathing. Once past the vocal cords, the ETT was delivered over the beroptic scope and IV induction was completed. Would patient comfort be improved and potential damage to the vocal cords be minimized if the propofol and succinylcholine are administered before the ETT is delivered over the beroptic scope? Is

CONCLUSION

the risk of failure to pass the ETT worth this potential benet? What have you seen in practice?

In managing the patient with a dicult airway, planning and preparation are essential. Patient evaluation,

132 PART IV. PULMONARY CRISES

4. e patient was transported to the operating room where the abscess was successfully drained.

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REFERENCES

8. Doyle DJ. Topical and regional anesthesia for tracheal intubation. 7th Annual Anesthesiology News Guide to the Airway

1. Caplan RA, Posner KL, Ward RJ, etal. Adverse respiratory events in anesthesia: a closed claims analysis. Anesthesiology. 1990; 72(5):828– 33.

2. Peterson GN, Domino KB, et al. Management of the dicult airway:a closed claims analysis. Anesthesiology 2005; 103:33– 9.

3. Rosenblatt WH, Sukhupragarn W. Airway management. In: Barash P, ed., Clinical Anesthesia. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:751– 92.

4. Apfelbaum JL, Hagberg CA, etal. Practice guidelines for management of the dicult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Dicult Airway. Anesthesiology. 2013;118:251– 70.

5. Videira RL, Neto PP, do Amaral RV, Freeman JA. Preoxygenation in children: for how long? Acta Anaesthesiologica Scandinavica. 1992;36:109– 11.

6. Xue FS, Tong SY, Wang XL, Deng XM, An G. Study of the optimal duration of preoxygenation in children. Journal of Clinical Anesthesia. 1995;7:93– 6.

7. Rajan S, Mohan P, Paul J, etal. Comparison of margin of safety following two dierent techniques of preoxygenation. Journal of Anaesthesiology Clinical Pharmacology. 2015;31(2):165– 8.

Management. Anesthesiology News, August 2014;9– 13.

9. Spiegel JE, Shah V. Surgical management of the failed airway: a guide to percutaneous cricothyrotomy. 7th Annual Anesthesiology News Guide to the Airway Management. Anesthesiology News, August 2014;47– 51.

10. DeLaurier GA, Hawkins ML, Treat RC, etal. Acute airway management:role of cricothyroidotomy. e American Journal of Surgery. 1990;56(1):12– 15.

11. Cook TM, Woodhall N, Frerk C, Fourth National Audit Project. Major complications of airway management in the UK :results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Dicult Airway Society. Part1:Anaesthesia. British Journal of Anaesthesia. 2011;106:617– 31.

12. Cavallone LF, Vannucci A. Review article: extubation of the difcult airway and extubation failure. Anesthsia and Analgesia. 2013;116(2):368– 83.

13. Artime CA, Hagberg CA. Tracheal extubation. Respir Care. 2014;59(6):991– 1005.

14. Dicult Airway Society Extubation Guidelines Group. Dicult Airway Society guidelines for the management of tracheal extubation. Anaesthesia. 2012;67(3):318– 40.

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16.

LARYNGOSPASM

Cory M. Furse and Matthew D.McEvoy

CLINICALCASE

of the laryngeal motor nerves, functionally closing the lar-

ynx and preventing air movement. “Adduction of the vocal A 48- year- old male with a history of hypertension and obstructive sleep apnea presents for laryngeal papilloma resection. He has had numerous resections in the past without anesthetic complications. Plan is to include insuation of anesthetic air and spontaneous ventilation, with intermittent intubation as a backup.

cords occurs, swily followed by that of the false cords. e

larynx becomes foreshortened and the false cords disappear

from view by making contact with the bulging [intralaryn-

geal portion of the epiglottic cartilage].”2 Hampson- Evans

etal. have proposed that these entities be termed “partial

laryngospasm” and “complete laryngospasm,” with the

dening characteristic being the presence or absence of air

PATHOPHYSIOLOGY OFDISEASESTATE

is section will cover both the mechanism of laryngospasm, as well as review risk factors.

movement, respectively.

RISK

e risk of laryngospasm has been repeatedly shown to vary

depending on the age of the patient, with children older

MECHANISM

e denition of “laryngospasm” is the involuntary closure of the glottic opening, through which air movement is diminished or halted. Closure of the glottic opening is mediated by the internal branch of the superior laryngeal nerve (SLN), which innervates the upper portion of the larynx down to the level of the vocal cords.1 Reex glottic closure is a response generated by the stimulation of the SLN, present most commonly during swallowing. Laryngospasm is a powerful exaggeration of this response stimulated by the presence of debris (e.g., blood or secretions) or airway devices in the airway, particularly if the patient is in a light plane of anesthesia.

In a classic paper published in 1956 in Anesthesiology, Bernard Fink detailed the mechanical nature of the anatomical structures involved in laryngospasm and proposed two separate pathways for treatment. He described what was later termed “glottic spasm,” in which strong inspiratory eort with a subsequent decrease in pressure below the vocal cords causes the cords to be pulled together with a sound characteristic of inspiratory stridor.2 is is in contrast to true vocal cord spasm that results from stimulus of the sensory nerves of the larynx and causes a response

than 6 years having an incidence twice that of adults, and children younger than 6 years having three times the incidence as compared with adults.

3– 5

Additional patient risk factors include a variety of states that result in heighted airway reexes, such as a history of reactive airway disease,4 tobacco smoke exposure,

3,4,6

and children with preexisting airway anomalies “(e.g., subglottic stenosis and cysts, laryngeal papillomatosis, cle palate, Pierre Robin syndrome, tracheal stenosis, vocal cord paralysis, laryngomalacia).”5 Many, but not all studies concerning the presence of a recent upper respiratory infection (URI) have concluded that the risk of laryngospasm is elevated for approximately 4– 6 weeks aer the resolution of symptoms.5 e most conclusive increase in risk concerns the current presence of an active URI, which increases the risk between two- and sevenfold.

7,8

ere is a higher incidence of laryngospasm with inex-

perienced anesthetists,

7,9

who may have less experience identifying and adjusting for the other factors that increase the risk as discussed herein. It has also been shown that the incidence is directly related to the number of endotracheal tube (ETT) or laryngeal mask airway (LMA) insertion attempts.10 Controversy

4,5

exists concerning the risk in rela-

tion to the type of airway management used. Traditionally

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it was taught that the least amount of airway intervention possible was the best, with the facemask (FM) being better than an LMA11 and the use of the ETT resulting in the highest incidence of adverse respiratory events.

12– 15

is notion has recently been challenged by Gharaei etal., who showed no dierence in the rate of laryngospasm in a ran-

BOX 16.1 TREATMENT STEPS FORLARYNGOSPASM

1. High- inspired oxygen concentration plusCPAP

2. Place an oral or nasalairway

3. Deepen the anesthetic with IVagent

domized trial comparing FM use versus LMA in a population of children with uncomplicatedURI.

Although controversy may exist as to the type of air-

4. If above ineffective, give succinylcholine 0.1– 4mg/ kg

5. Consider SLN blocks or transtracheal lidocaine

way management, it is clear that the rate of laryngospasm is increased during periods of light anesthesia, risk varies with type of anesthetic agent employed. As far as intravenous agents are concerned, propofol is known to be a powerful depressant of airway reexes and is therefore protective with regard to chance of laryngospasm. is is in contrast to thiopentone, which provides the greatest risk of laryngospasm,

7,17

followed by ketamine, which can not only

increase the laryngeal reactivity but also stimulate secre-

1,3,4

and that the

closure, otherwise termed complete laryngospasm.

2,3

If this condition is not treated in a timely fashion the patient will become cyanotic and show desaturation with regard to pulse oximetry. Eventually if not resolved, the patient may experience bradycardia and cardiovascular collapse. us, if laryngospasm is thought to be present, prompt action is warranted, as outlined in Box 16.1.

tions, providing a secondary risk factor.18 Inhalation agents also show diering rates of laryngospasm with desurane, at up to 50% incidence,19 as the worst oender, followed by isourane, enurane, and halothane. been shown between sevourane and halothane.

20– 22

No dierence has

Certain surgeries place the patient at an increased risk of laryngospasm, chiey removal of tonsils and adenoids, which have shown an incidence range of 21%– 27%.

4,9,23

might be expected, given the patient risk factors delineated

MANAGEMENT OFTHE PATIENT

Several algorithms

3,4

and methodologies2 have been proposed regarding the treatment of laryngospasm. Holzki etal. have reported that partial and complete laryngospasm are not separate entities,24 and therefore Al- alami et al. proposed one treatment algorithm for all cases.

above, as well as the type of anesthesia that is delivered, other upper airway procedures such as bronchoscopy also have an increasedrisk.

INITIAL TREATMENTSTEPS

It is important initially to rule out other causes of upper

ASSESSMENT OFTHE PATIENT: PRESENTING SIGNS AND SYMPTOMS

Observation of the patient plays a key role in early detection of complete or partial laryngospasm. If the patient is spontaneously breathing when laryngospasm occurs, then it will oen appear as if the patient has upper airway obstruction. e chest and abdominal movement will be asynchronous, with the abdomen rising due to the pull of the diaphragm displacing the abdominal contents, and the chest retracting or the sternal notch pulling inward due to the lack of air entry. Stridor is one of the distinguishing features between partial and complete laryngospasm,3 and is indicative of a small amount of airow, and a probable light plane of anesthesia.

Cessation of airow, as indicated by no movement at the

bag, and no end- tidal CO2 detection, results from full glottic

airway obstruction, and the initial treatment steps here are designed to help account for that possibility.

Place the patient on 100% oxygen, with CPAP and jaw

3,4

thrust.

ACPAP of 5– 15 cmH2O has been reported to help maintain oxygenation and also act as a deterrent to the laryngospasm, oen resulting in breaking of the reex vocal cord closure.

An oral or nasal airway may help ensure that the base of the tongue is not obstructing airow against the posterior pharyngeal wall,25 but caution must be exercised to ensure that the airway is not causing a noxious stimulus at the glottic opening and prolonging the spastic reex.24 is will function to treat both upper airway collapse and to mechanically elongate the cords and change the orientation of the glottis through interaction of the geniohyoid muscles and the hyoid bone.

2– 4

If early on in the course of treatment, before the patient has begun to decompensate with regard to oxygen

LARYNGOSPASM 135

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