topics / مواضيع: Airway Management

Airway Management

Theresa M. Schwab, MD

Key Points

• Rapid-sequence intubation (RSI) is the preferred method

for endotracheal tube placement in the emergency

department.

• The decision to intubate should always be made on

clinical grounds. Time permitting, assess for factors

predictive of a difficult airway before RSI.

INTRODUCTION

Successful airway management depends on the prompt

recognition of an inadequate airway, the identification of

risk factors that may impair successful bag-valve-mask

(BVM) ventilation or endotracheal t ube (ETT) placement,

and the use of an appropriate technique to properly secure

the airway. The decision to intubate is a clinical one and

should be based on the presence of any 1 of 3 major conditions: an inability to successfully protect one's airway

against aspiration/occlusion, an inability to successfully

oxygenate the blood (hypoxemia), or an inability to successfully clear the respiratory byproducts of cellular

metabolism (hypercapnia). Additional indications including the desire to decrease the work of breathing (sepsis),

the need for therapeutic hyperventilation (increased intracranial pressure [ICP]), and the need to obtain diagnostic

imaging in noncooperative individuals (altered mental

status) should be taken into account on a patient-bypatient basis.

Techniques for the management of unstable airways

range from basic shifts in patient positioning to invasive

surgical intervention. Standard basic life support recommendations such as the head-tilt chin-lift maneuver may

open a previously occluded airway. Oropharyngeal and

nasal airway adjuncts are both simple to use and highly

• General criteria for endotracheal intubation include a

failure to protect the airway, a failure to adequately

oxygenate, and a fa ilure to expire accumulating co r

• Pursue alternative techniques (eg, cricothyrotomy) in

patients when the in itial airway intervention has fa iled

and the patient cannot be adequately ventilated.

effective in this setting, but are unfortunately often underutilized. Failure to respond to these measures warrants the

placement of an ETT. Rapid-sequence intubation (RSI)

combines the careful use of pretreatment interventions with

the administration of induction and paralytic agents to create the ideal environment for ETT placement and is the

preferred method in the emergency department (ED).

A patient who cannot be intubated within 3 attempts is

considered a failed airway. This scenario occurs in -3-5%

of all cases. Numerous alternative devices including laryn

geal mask airways (LMA), introducer bougies, and fiberoptic instruments have been developed to facilitate airway

management in these situations. That said, these methods

are not failsafe, and roughly 0.6% of patients will require a

surgical airway. Emergent cricothyrotomy is the preferred

surgical technique for most ED patients.

CLINICAL PRESENTATION

.... History

The need for immediate airway intervention in emergency

situations always supersedes the need for a comprehensive

history and physical exam. Time permitting, perform a

rapid airway assessment to identify any risk factors predictive of a difficult airway, inquire about any current

CHAPTER 11

medication use and known drug allergies, and try to ascertain the immediate events leading up to ED presentation.

Risk factors predictive of a difficult airway include

those that impair adequate BVM ventilation and those that

preclude successful placement of an ETT. Examples of the

former include patients with facial trauma and distorted

anatomy, obese patients with excessive cervical soft t issue,

and asthmatic patents with excessively high airway resistances. Examples of the latter include patients with a his

tory of degenerative changes of the spine that limit cervical

mobility ( eg, rheumatoid arthritis, ankylosing spondylitis),

patients with underlying head and neck cancers that distort the normal cervical anatomy, and those with excessive

swelling of the airway and surrounding tissues (eg,

angioedema).

..... Physical Examination

Rapidly examine the airways of all critically ill patients.

Always consider the presence of concurrent cervical spine

injury in victims of trauma and immobilize as appropriate.

Carefully examine the face, noting any signs of significant

facial trauma and the presence of a beard, both of which

frequently impair adequate BVM ventilation. Inspect the

oropharynx, noting the presence of dentures; the size of

the teeth and presence of a significant overbite; visibility of

the soft palate, uvula, and tonsillar pillars (ie, Mallampati

classification); and the presence of significant airway swelling. The pooling of blood or secretions in the oropharynx

indicates an inability to properly protect the airway. A good

adage to remember when assessing the airway is the 3-3-2

rule. The inability to open the mouth 3 finger breaths, a

distance from the tip of the chin to the base of the neck less

than 3 finger breaths, or a distance between the mandibular floor and the prominence of the thyroid cartilage of less

than 2 finger breaths all predict more difficult ETT place

ment. Assess the range of motion of the cervical spine,

provided there is no concern for occult injury.

DIAGNOSTIC STUDIES

..... Laboratory

Although abnormalities on either blood gas analysis (hypercapnia) or pulse oximetry (hypoxemia) may be indicative of

an inadequate airway, normal values on either of these studies should not j ustify the delay of definitive intervention in

the appropriate clinical scenario. Progressive abnormalities

on serial testing (increasing PaC02

, decreasing Pa02

) in

patients who are clinically decompensating indicates the

need for airway intervention.

..... Imaging

Imaging studies should not be used to predict the need for

airway intervention. Obtain a chest x-ray (CXR) in all

patients after intubation to confirm proper ETT placement.

The tip of the ETT should be visualized approximately

2 em above the carina. Deeper insertion results in placement into the right mainstem bronchus.

MEDICAL DECISION MAKING

Consider all rapidly reversible causes of airway compromise

(eg, hypoglycemia, opioid overdose) before pursuing endotracheal intubation. Proper intervention may transform a

comatose patient with a rather tenuous airway into an awake

coherent individual with adequate airway protection.

Identify patients who are likely to present a difficult airway

and those who require specialized approaches ( eg, head

trauma precautions, hypotension, cervical spine injury) and

proceed accordingly (Figure 1 1-1).

PROCEDURES

..... Bag-Valve-Mask Ventilation

Proper BVM ventilation requires an open airway and an

airtight seal between the mask and the patient's face. Use

the head-tilt chin-lift technique (jaw-thrust maneuver in

trauma victims) to open the airway and insert oropharyngeal or nasal adjuncts as necessary to maintain patency.

Avoid the use of oral adjuncts in patients with intact gag

reflexes and nasal adjuncts in patients with significant

mid-face trauma. With proper technique and a high-flow

oxygen source, this method can provide an Fi02 of

approximately 90% ( Figure 1 1-2).

..... Rapid-Sequence Intubation

Preoxygenate all patients with a high-flow oxygen source

(eg, nonrebreather [NRB] mask) for several minutes as

time permits before RSI. Avoid positive pressure ventilation

(eg, BVM) to prevent insufflation of the stomach, which

can increase the patient's risk for aspiration. Use this time

to prepare and check your equipment. Ensure adequate N

access and proper function of the suction device. Remove

patient dentures, significant loose teeth, and any oral debris.

Choose the appropriate size ETT. Tube sizes range in diameter from 2.5-9 mm. A size 7.5- or 8.0-mm tube is appropriate for most adult female and male patients respectively.

Inflate the balloon to check for leaks and insert a stylet.

Uncuffed ETTs have been historically preferred in patients

younger than 8 years of age as the narrowest portion of

their airways lies inferior to the vocal cords at the level of

the cricoid ring. That said, most practitioners now prefer

cuffed ETTs for all patients. To determine the appropriate

size of the ETT in pediatric patients, either use the formula

Size = (Age/4) + 4 for uncuffed tubes or (Age/4) + 3 for the

cuffed variety, or use a tube that is equal in diameter to the

child's fifth finger .

Check the light on your laryngoscope blade to ensure

that it works. Laryngoscope blades range in size from 0-4

and come in 2 major varieties. The Macintosh blade is

curved in shape and meant to indirectly lift the epiglottis

away from the vocal cords. It is also designed with a special

AIRWAY MANAGEMENT

Airway management indicated:

Failure to oxygenate, venti late, or

protect the airway

Rapid airway eva luation to identify

findings indicative of a difficult airway

Difficult airway

predicted

No difficult airway

predicted

Modified approach including:

• "Awake look" intubation

• Difficult airway adjuncts

(LMA, bougie, fiberoptics, etc.)

Figure 1 1-1. Airway diag nostic algorithm. LMA, laryngeal mask airways; RSI, rapid-sequence intubation.

ridge meant to sweep the tongue to the side during insertion

to improve visualization of the vocal cords. The Miller blade

is straight in appearance and meant to directly lift the

Figure 1 1-2. Proper method of BVM ventilation.

epiglottis away from the vocal cords. It is of particular benefit in patients with very anterior airways and those with a

large "floppy" epiglottis. A size 3 or 4 Macintosh blade is

appropriate for most adult ED patients (Figure 1 1-3).

Certain clinical scenarios warrant unique modifications to standard RSI to attenuate the adverse physiologic

responses to endotracheal intubation. Pretreat head injury

patients with lidocaine (1.5 mg/kg) and a "defasciculating"

dose of a nondepolarizing neuromuscular blocker ( eg,

pancuronium 0.01 mg/kg) to limit the potential spike in

ICP that may accompany ETT placement. Pretreat most

pediatric patients with an anticholinergic agent ( eg, atro

pine 0.02 mg/kg) to prevent reflex bradycardia. Pretreat

patients in whom rapid elevations in either blood pressure

or heart rate would be catastrophic (eg, aortic dissection)

with an opioid analgesic ( eg, fentanyl 3 meg/kg) to limit

excessive catecholamine surges. Of note, the clinical utility

of many of these pretreatment regimens has recently come

under considerable debate.

Outside of the pretreatment agents listed previously,

the remaining RSI medications can be divided into either

CHAPTER 11

Figure 1 1-3. Equi pment needed for orotracheal

intubation in an adu lt. From left to right, laryngoscope

handle attached to Macintosh 3 blade, Maci ntosh

4 blade, Miller 4 blade, end-tidal C02 detector,

1 0-ml syringe, and endotracheal tube with stylet.

induction agents or paralyzing agents. Induction agents are

designed to elicit extremely rapid sedation to facilitate ETT

placement. A variety of medications are available, including etomidate (0.3 mg/kg), propofol (1 mg/kg), ketamine

(2-3 mg/kg), and midazolam (0.05-0. 1 mg/kg). Of these,

etomidate is used most frequently in the ED because of its

rapid onset and offset and relative hemodynamic neutrality. Avoid the use of benzodiazepines and propofol in

hypotensive patients and ketamine in patients with paten

tial traumatic brain injury.

Paralytic agents can be divided into depolarizing and

nondepolarizing categories. Succinylcholine ( 1.5 mg/kg) is

the lone agent in the depolarizing class and the most commonly used paralytic for RSI because of its rapid onset and

short duration of activity. Most patients achieve r elaxation

within 1 minute, complete paralysis by the 2- to 3-minute

mark, and a return of motor function within 10 minutes.

Avoid succinylcholine in patients with known hyperkale

mia and those with pathologically denervated tissues (eg,

spinal cord injuries, burns) as it can precipitate life-threatening ventricular dysrhythmias. Given the longer duration

of paralysis for most nondepolarizing agents (eg, atracurium), their use is generally avoided in RSI.

Certain patients predicted to have difficult airways may

benefit from intubation via the use of lower than normal

doses of induction agents without concurrent paralytics.

Also known as the "awake look;' this limits the all too real

potential for creating the scenario of a paralyzed and,

therefore, not breathing patient who cannot be intubated.

Finally, apneic patients or those in cardiac arrest are not

Vocal cords

.6. Figure 1 1-4. Laryngoscopic view. (Reproduced with

permission from Kempe CH, Si lver HK, O'Brien 0,

(editors): Current Pediatric Diagnosis Er Treatment. 4th ed.

lange, 1 976.)

candidates for RSI. Their condition does not allow time for

either preoxygenation or pretreatment, and being unconscious, they do not require RSI medications to facilitate

ETT placement. Temporize these patients with BVM venti

lation pending their emergent intubation.

To visualize the vocal cords, hold the laryngoscope in

the left hand and carefully insert the blade into the oropharynx directed downward along the tongue and into the

throat. Gentle upward traction should lift the epiglottis

from tl1e larynx and reveal the vocal cords (Figure 1 1-4).

Concurrent external laryngeal manipulation may shift the

patient's vocal cords into better view. Keep in mind that

pediatric airways are typically more anterior than those of

adults and that their relatively large tongues and floppy

epiglottis often necessitate the use of a Miller blade.

Insert the ETT and maintain visualization until the balloon has clearly passed the vocal cords. Advance the ETT

until the depth (at the teeth) is at 3 times the diameter of the

tube. Keep in mind this is only an estimate, and all patients

require a postprocedural CXR to document the depth of

ETT placement. Proper insertion can be inlmediately con firnled at the bedside by auscultating for Synlffietric bilateral

breath sounds and via the use of color-change capnography.

Gentle downward pressure applied to the cricoid cartilage (Sellick's maneuver) at the onset of induction and

paralysis has been historically advocated to limit the potential for aspiration. A growing body of literature has begun to

question the utility of this maneuver as it not only fails to

prevent aspiration but can limit adequate visualization of

the vocal cords and impair successful insertion of the ETT. If

cricoid pressure is applied, release inlmediately if the patient

begins to vomit to prevent secondary esophageal rupture.

� Difficult Airway Adjuncts

Multiple devices have been designed to assist with the

management of difficult airways. Laryngeal mask airways

AIRWAY MANAGEMENT

Figure 1 1-5. Schematic demonstrati ng use

of bougie.

(LMA) conform to the natural curvature of the oropharynx and are designed for blind insertion into the supraglottic region. Proper insertion creates an airtight seal over

the larynx, allowing for mechanical ventilation. LMA

insertion does not prevent aspiration, though, and is not

considered a definitive airway.

Introducer bougies are very useful in patients whose

vocal cords cannot be adequately visualized. They are

essentially long flexible rubber sty lets with a distal curve at

their tip, which, when blindly inserted along the inferior

margin of the epiglottis, will naturally angle upward into

the larynx and through the vocal cords. Successful endotracheal placement can be detected as the tip of the bougie

skips along the tracheal rings. The ETT is then inserted

blindly over the bougie and into the airway (Figure 1 1-5).

Cricothyrotomy is performed by making a percutane

ous incision in the cricothyroid membrane through which

a tracheostomy or small ETT can be placed (Figure 1 1-6).

This can be a life-saving intervention in the crashing

patient when less invasive techniques to secure the airway

have failed. Common indications include massive facial

trauma and angioedema. Cricothyrotomy is contraindi

cated in children <8 years of age and should be replaced

with needle cricothyrotomy.

Additional difficult airway adjuncts include blind nasatracheal intubation, lighted stylets, Combitubes, fiberoptic

intubation, retrograde wire-guided tracheal intubation,

and percutaneous translaryngeal ventilation.

DISPOSITION

Admit all patients who require airway management to an

intensive care unit setting.

Figure 1 1-6. Cricothyrotomy. A. An 11 blade

scalpel is used to cut the cricothyroid membrane. B. A

skin hook opens the incision and lifts the thyroid

carti lage su periorly so that the tracheostomy tube or

ETT can be inserted into the ai rway. (Reprinted with

permission from Bai l itz J, Bokhari F, Scaletta TA, et al.

Emergent Management of Trauma. 3rd ed. New York:

McGraw-Hill Education, 201 1 .)

topics / مواضيع

Translate

Search This Blog

الصفحات

Airway Management

No comments:

Post a Comment

الصفحات

mcq general

Search This Blog

Labels