Surgical airway management, unlike conven- tional airway management, entails the creation of an opening into the trachea to provide oxy- genation and ventilation. Proficiency with surgi- cal airway techniques can mean the difference between life and death.
Cricothyrotomy
Cricothyrotomy is the creation of a surgical opening through the cricothyroid membrane to allow placement of an ETT or cuffed tracheostomy tube (Figure 2.17). The proximal ends of these tubes can be hooked up to a BVM for oxygenation and ventilation. A primary indication for cricothyro- tomy is the need for a definitive airway in the patient in whom orotracheal or BNTI has failed, is contraindicated or is extremely difficult. A classic example is the patient with severe facial trauma in whom conventional airway manage- ment is extremely complicated or unfeasible.
The primary contraindication to cricothyro- tomy is young age. Due to anatomic consider- ations, the procedure is extremely difficult in children 10–12 years of age and therefore generally avoided in this population. Other contraindications to cricothyrotomy include preexisting tracheal or laryngeal pathology, anatomic obliteration of the landmarks (i.e., hematoma), coagulopathy and operator inex- perience with the procedure. Complications of cricothyrotomy include incorrect airway place- ment, hemorrhage, tracheal or laryngeal injury, infection, pneumomediastinum, subglottic steno- sis and voice change.
Transtracheal jet ventilation (TTJV)
An alternative surgical airway procedure is nee- dle cricothyrotomy with percutaneous TTJV (Figure 2.18). In this technique, a transtracheal catheter is inserted through the cricothyroid membrane into the trachea and connected to a jet ventilation system which includes high-pressure tubing, an oxygen source at 50 psi, and an in-line one-way valve for intermittent administration of oxygen. 100% oxygen is then delivered at 12–20 bursts per minute. The inspiratory phase should last 1 second while the expiratory phase lasts 2–4 seconds.
Advantages of this technique include its simplicity, safety and speed. There is typically less bleeding when compared with cricothyrotomy, and age is not a contraindication, making it the preferred surgical airway in children 12 years.
During TTJV, the upper airway must be free of obstruction to allow for complete exhalation, or the patient is at risk of barotrauma from air stacking. All patients receiving TTJV should have an oral and nasal airway placed. Unlike cricothyrotomy, TTJV does not provide com- plete airway protection. Therefore, it should be considered a temporizing measure until a defini- tive airway can be established.
Airway management
Special patients
Pediatric
Though the principles of airway management in adults and children are the same, a number of age- related differences must be accounted for when managing the pediatric airway. Specific anatomic differences between adults and children and their clinical significance in airway management are summarized in Table 2.7 and Figure 2.19.
Physiologically, pediatric patients have a higher rate of O2 consumption and smaller functional residual capacity; therefore, they tend to desaturate
more rapidly than adults. Compared with adults, children tend to have a shortened period of pro- tection from hypoxia following pre-oxygenation, and infants and small children may require BVM ventilation during RSI to avoid hypoxia.
Airway equipment selection is also based on the child’s weight and length (Table 2.8). A child’s ETT size can be estimated by the size of their external naris, the diameter of their little fin- ger, or the formula ETT size 4(age in years/4).
The depth of ETT placement may be remem- bered as approximately three times ETT size or (age in years/2)12.
Thyroid notch Thyroid cartilage
Indent Trachea Cricoid cartilage Cricothyroid membrane
Figure 2.17
Surgical cricothyrotomy. Used with permission from American College of Surgeons’ Committee on Trauma, Advanced Trauma Life Support©for Doctors, Student Course Manual, 6th ed., Chicago, American College of Surgeons, 1997, page 85.
Airway management
Table 2.7 Anatomic airway differences between children and adults. Reproduced with permission from Walls RM et al, Manual of Emergency Airway Management, 2nd ed. and Companion Manual to the Airway Course
(www.theairwaysite.com), Lippincott Williams & Wilkins, 2004
Anatomy Clinical significance
Large intraoral tongue occupying relatively 1. High anterior airway position of the glottic opening compared large portion of the oral cavity with that in adults
High tracheal opening: C1 in infancy versus 2. Straight blade preferred over curved to push distensible C3–4 at age 7, C4–5 in the adult anatomy out of the way to visualize the larynx
Large occiput that may cause flexion of the Sniffing position is preferred. The large occiput actually elevates airway, large tongue that easily collapses the head into the sniffing position in most infants and children.
against the posterior pharynx A towel may be required under shoulders to elevate torso relative to head in small infants
Cricoid ring narrowest portion of the trachea 1. Uncuffed tubes provide adequate seal as they fit snugly at as compared with the vocal cords in the adult the level of the cricoid ring
2. Correct tube size essential since variable expansion cuffed tubes not used
Consistent anatomic variations with age with 2 years, high anterior fewer abnormal variations related to body 2 to 8, transition habitus, arthritis, chronic disease 8, small adult
Large tonsils and adenoids may bleed. More acute Blind nasotracheal intubation not indicated in children angle between epiglottis and laryngeal opening Nasotracheal intubation failure
results in nasotracheal intubation attempt failures
Small cricothyroid membrane Needle cricothyroidotomy difficult, surgical cricothyroidotomy impossible in infants and small children
Wall fitting High-pressure hose
Regulator Pressure guage
On–off valve
PVC tubing
Figure 2.18
Transtracheal jet ventilation. PVC: polyvinyl chloride.
Airway management
Drug dosing in children and the choice of medications for RSI is based on a child’s age and weight. Of note, the dose of SCh is higher in children (2 mg/kg) and infants (3 mg/kg) than in adults. Children younger than 5 years are not given a defasciculating dose of a nondepolarizing NMBA but are treated with atropine to prevent bradycardia from airway manipulation. Atropine should also be administered to all children10 years of age receiving SCh to prevent bradycardia.
Fentanyl should be used with caution in infants and small children, as it may lead to respiratory depression or hypotension.
Status asthmaticus
Managing the sick asthma patient in the ED can present a tremendous challenge. Fatigue from
prolonged respiratory effort in the face of severe small airway resistance commonly results in respiratory failure; approximately 1–3% of asthma exacerbations require intubation. In general, these patients are extremely difficult to pre- oxygenate due to a reduced functional residual capacity, and may be very difficult to ventilate with a BVM as a result of severe airway obstruction.
The single most important intervention in the patient with status asthmaticus and respiratory failure is early control of the airway. RSI is the method of choice (performed by the most experi- enced laryngoscopist) along with preparation for rescue cricothyrotomy. When compared with RSI, BNTI is more time-consuming, results in greater O2desaturation, and has a higher rate of complication or failure.
Adult Infant
Junction of chin and neck
Epiglottis
Vocal cords
Cricoid ring Cricoid membrane Tongue
Tongue
Figure 2.19
Anatomic airway differences between children and adults. The anatomic differences particular to children include: 1.
Higher, more anterior position for the glottic opening. (Note the relationship of the vocal cords to the chin/neck junction).
2. Relatively larger tongue in the infant, which lies between the mouth and glottic opening. 3. Relatively larger and more floppy epiglottis in the child. 4. Cricoid ring is the narrowest portion of the pediatric airway; in adults, it is the vocal cords.
5. Position and size of the cricothyroid membrane in the infant. 6. Sharper, more difficult angle for blind nasotracheal intubation. 7. Larger relative size of the occiput in the infant. Reproduced with permission from Walls RM et al, Manual of Emergency Airway Management, 2nd ed. and Companion Manual to the Airway Course (www.theairwaysite.com), Lippincott Williams & Wilkins, 2004.
Airway management Table 2.8Pediatric airway equipment selection.Reproduced with permission from Walls et al, Manual of Emergency Airway Management, 2nd ed.and Companion Manual to the Airway Course (www.theairwaysite.com), Lippincott Williams & Wilkins, 2004 Length (cm) and weight (kg) based pediatric equipment chart PinkRedPurpleYellowWhiteBlueOrangeGreen Weight (kg)6–78–910–1112–1415–1819–2323–3131–41 Length (cm)60.75–67.7567.75–75.2575.25–8585–98.2598.25–110.75110.75–122.5122.5–137.5137.5–155 ETT size (mm)3.53.54.04.55.05.56.0 cuff6.5 cuff Lip-tip length (mm)10.510.512.013.515.016.518.019.5 Laryngoscope11122223 StraightStraightStraightStraightStraightStraight or curvedStraight or curvedStraight or curved Suction catheter8F8F8F8–10F10F10F10F12F Stylet6F6F6F6F6F14F14F14F Oral airway50mm50mm60mm60mm60mm70mm80mm80mm Nasopharyngeal airway14F14F18F20F22F24F26F30F Bag-valve deviceInfantInfantChildChildChildChildChild/adultAdult Oxygen maskNewbornNewbornPediatricPediatricPediatricPediatricAdultAdult Vascular access22–24/23–2522–24/23–2520–22/23–2518–22/21–2318–22/21–2318–20/21–2318–20/21–2216–20/18–21 Catheter/butterflyintraosseousintraosseousintraosseousintraosseousintraosseousintraosseous Nasogastric tube5–8F5–8F8–10F10F10–12F12–14F14–18F18F Urinary catheter5–8F5–8F8–10F10F10–12F10–12F12F12F Chest tube10–12F10–12F16–20F20–24F20–24F24–32F24–32F32–40F Blood pressure cuffNewborn/infantNewborn/infantInfant/childChildChildChildChild/adultAdult LMA†1.51.52222–2.52.53 Directions for use:1.Measure patient length with centimeter tape, or with a Broselow tape;2.Using measured length in centimeters or Broselow tape measurement, access appropriate equipment column;3.For endotracheal tubes, oral and nasopharyngeal airways, and laryngeal mask airways (LMAs), always select one size smaller and one size larger than the recommended size, in addition to the recommended size. †Based on manufacturer’s weight-based guidelines. Mask size:11.522.53 Patient size (kg):up to 55–1010–2020–30Over 30 Permission to reproduce with modification from Lutten RC, Wears RL, Broselow J, et al.Ann Emerg Med 1992;21:900–904.
Airway management If the patient is most comfortable sitting
upright, allow him to maintain that position. All patients should be pretreated with lidocaine 1.5 mg/kg which suppresses coughing, improves ETT tolerance and reduces bronchospasm.
Ketamine 1.5 mg/kg is the induction agent of choice in status asthmaticus as it stimulates the release of catecholamines and produces bron- chodilation.
Upon loss of consciousness, the patient should be laid supine and intubated. The largest possible ETT should be used to allow for aggres- sive pulmonary toilet. The intubated asthmatic patient should then be paralyzed and sedated to facilitate oxygenation and ventilation. The patient’s clinical condition may worsen after intubation if the patient proves to be difficult to ventilate, develops a tension pneumothorax or develops hypotension; caution is warranted.
Increased intracranial pressure
The presence or suspicion of increased ICP directly affects the approach to RSI, as the techniques and medications used during RSI may further increase the patient’s ICP. There is a reflex sympathetic response to larygnoscopy that results in a systemic release of catecholamines and increased ICP. This response can be blunted through the administra- tion of fentanyl (3 mcg/kg), which is given over 30–60 seconds during the pretreatment phase of RSI. Laryngoscopy or any laryngeal stimulation (i.e., suctioning) may also increase ICP by a direct reflex mechanism unrelated to this catecholamine surge. The administration of lidocaine (1.5 mg/kg) during the pretreatment phase effectively blunts this response and may also reduce ICP.
Unlike nondepolarizing NMBAs, SCh admin- istration increases ICP. However, the administra- tion of a small “defasciculating dose” (about one-tenth the paralyzing dose) of a competitive neuromuscular blocker given during the pretreat- ment phase mitigates this response. Pancuronium (0.01 mg/kg) or vecuronium (0.01 mg/kg) administered 3 minutes before the administra- tion of SCh effectively blunts the rise in ICP.
The ideal induction agent should reduce ICP, maintain cerebral perfusion and provide some cerebral protective effect. Sodium thiopental effectively reduces ICP by decreasing cerebral blood flow, and confers a cerebroprotective effect by lowering O2 utilization within the brain.
However, thiopental is a potent venodilator and negative inotrope which can lead to hypotension,
a factor associated with significantly increased mortality in head-injured patients. Etomidate has emerged as the induction agent of choice in patients with increased ICP. It reduces ICP and confers cerebroprotection in a manner similar to thiopental but provides remarkable hemodyna- mic stability.
Suspected cervical spine injury
All patients with significant blunt trauma are assumed to be at risk for cervical spine injury.
Inadvertent movement of the neck of a patient with an unstable cervical spine injury can lead to permanent neurologic disability or death.
Accordingly, many trauma patients are trans- ported to the ED in a stiff cervical collar and immobilized to a backboard. Though providing protection of the cervical spine, immobilization places the patient at risk for aspiration and venti- latory compromise.
If the patient requires airway management, precious time should not be wasted obtaining a single lateral radiograph of the cervical spine to exclude cervical spine injury. This approach delays definitive airway management and pro- vides a false sense of security, as a single view is inadequate to exclude injury to the cervical spine.
Numerous studies have shown that the proper approach to managing these patients is RSI with in-line immobilization (Figure 2.20). Paralyzing
Figure 2.20
In-line immoblilization of the cervical spine.
the patient reduces the risk of patient movement during intubation. A second individual main- taining immobilization of the head and neck in the neutral position throughout the procedure prevents neck hyperextension during laryn- goscopy.
Pearls, pitfalls, and myths
• Learn to recognize objective signs of impending airway compromise.
• Though bedside maneuvers or airway adjuncts can reestablish airway patency, they do not provide definitive airway protection.
• A definitive airway requires an ETT in the trachea secured in place with the cuff inflated and attached to an O2-rich ventilation device.
• Competence with the bag-valve-mask is required for airway management.
• Lifesaving medications may be given via the ETT.
• Learn the 9 P’s of Rapid Sequence Intubation
• Prior to initiating RSI, prepare for intubation using the mnemonic SOAP ME.
• Adequate preoxygenation may allow the larygnoscopist several attempts for successful intubation prior to arterial O2 desaturation.
• Select your pretreatment (LOAD)
medications to mitigate the adverse effects of SCh and the act of intubation.
• NBMAs do not provide analgesia, sedation or amnesia, so always provide an induction agent prior to neuromuscular blockade.
• After any unsuccessful intubation attempt, change “something” prior to the next attempt.
• Proper ETT placement needs to be confirmed after every intubation; do not rely on only one approach as the sole means for confirming ETT placement.
• Following confirmation of ETT placement, secure the ETT, check vital signs, order a chest X-ray and provide long-term sedation and paralysis (if appropriate).
• Not every patient needs RSI. Learn the indications and techniques for awake oral intubation and BNTI.
• Every intubation should be assumed difficult, and a back-up plan should be formulated prior to proceeding.
• Be familiar with the algorithms, devices, and techniques used for the failed airway.
• Airway equipment selection and drug dosing is based on a child’s age, weight and length. A child’s ETT size 4 (age in years/4).
• Use RSI with in-line immobilization for airway management of any patient with potential cervical spine injury.
References
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Emergency Medicine: A Comprehensive Study Guide, 5th ed., McGraw Hill, 2000.
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Airway management
Cardiopulmonary and cerebral resuscitation