A General Principles

Emergency surgical airway management comprises four distinct but related techniques that gain access to the infraglottic airway. These are needle cricothyrotomy, percutaneous cricothyrotomy, surgical cricothyrotomy, and surgical tracheostomy. In emergency situations, cricothyrotomy is greatly preferred over tracheostomy because of its relative simplicity, speed, and lower complication rate. The airway is very superficial at the level of the cricothyroid membrane (CTM), separated from the skin only by the subcutaneous fat and anterior cervical fascia. The trachea moves progressively deeper in the neck as it travels caudally, making anterior access more difficult and introducing additional anatomic barriers (e.g., thyroid isthmus.) Needle cricothyrotomy with percutaneous transtracheal ventilation may provide temporary oxygenation in some patients, but the technique does not provide a secure (protected) airway and cannot support ventilation. Needle cricothyrotomy is reviewed elsewhere in this textbook (see Chapter 30). The emphasis in this chapter is on surgical and percutaneous cricothyrotomy; because the former, and in some cases the latter, places a cuffed endotracheal tube (ETT) in the trachea.

Any discussion of surgical airway management techniques must account for three important concepts:

B Historical Perspective

The surgical airway as a life-saving procedure has been appreciated for thousands of years. The first depictions of surgical tracheostomy were found on Egyptian tablets dating from 3600 BC.⁷ In the second century AD, Galen suggested tracheostomy, utilizing a vertical incision, as an emergency treatment for airway obstruction.^8–10 Vesalius later published the first detailed descriptions of tracheostomy in the 16th century, using a reed to ventilate the lungs. Ironically, his alleged resuscitation of a Spanish nobleman through tracheostomy and ventilation led to condemnation by the Spanish Inquisition and his ultimate death.¹¹ The first record of a successful tracheostomy performed in the United States was in 1852; the patient later died of airway stenosis, a common complication at that time. A paper from 1886 described a mortality rate of 50% for tracheostomy and a high incidence of stenosis, which accounted for many of the deaths.¹²

Chevalier Jackson published a landmark paper on tracheostomy in 1909, which enumerated principles still relevant today.¹³ He described a surgical mortality rate of only 3%, which he attributed to several factors: optimal airway control before surgery, use of local anesthesia rather than sedation, use of a well-designed tube, and meticulous surgical and postoperative care. Jackson achieved international recognition; however, so did his condemnation of “high tracheostomy” as the cause of subglottic stenosis. The high tracheostomy he referred to was a cricothyrotomy, which at that time involved division of the cricoid or thyroid cartilage. Modern cricothyrotomy involves incision of the CTM only. In 1921, Jackson published a study of 200 patients referred to him for postcricothyrotomy stenosis. Aside from the obvious referral bias, the indication for a surgical airway at that time was primarily inflammatory lesions of the upper airway, which probably accounted for the high incidence of subglottic stenosis.¹⁴

Although in retrospect it was the technique and the underlying condition that were largely responsible for the high rate of stenosis, fear of this complication condemned the technique of cricothyrotomy for over half a century. In the interest of developing a technique that was safer and quicker than Jackson’s open dissection, Toye and Weinstein described the first percutaneous tracheostomy in 1969.¹⁵ However, cricothyrotomy was not widely reconsidered as a surgical airway option until 1976, when Brantigan and Grow published the results of cricothyrotomy for long-term airway management in 655 patients.¹⁶ In their series, the rate of stenosis was 0.01%, no major complications were described, and the procedure was found to be faster, simpler, and less likely to cause bleeding than tracheostomy. Subsequent studies have supported their conclusion that cricothyrotomy is a safe and effective surgical airway procedure and should be the preferred technique when emergent surgical airway control is needed.^7,17,18 Contemporary case series have demonstrated that cricothyrotomy can be performed with a high success rate and a reasonably low complication rate by hospital-based physicians and other clinicians (i.e., nurses, paramedics) providing prehospital care.^13,19–25

C Definitions of the Surgical Airway

The definition of surgical airway can be so broad as to comprise all forms of airway management that require the creation of a new opening into the airway. Cricothyrotomy is the establishment of a surgical opening in the airway through the CTM and placement of a cuffed tracheostomy tube or ETT. Cricothyrotomy has also been referred to as cricothyroidotomy, cricothyroidostomy, cricothyrostomy, laryngostomy, or laryngotomy; however, cricothyrotomy is presently the preferred term. Tracheostomy differs from cricothyrotomy in the anatomic location of entry into the airway. Tracheostomy is the establishment of a surgical opening in the airway at any level including at or caudal to the first tracheal ring.

Surgical airways may be further subclassified according to the technique used: (1) surgical (sometimes referred to as “open” or “full open” or “full surgical”); (2) percutaneous (more precisely described by the actual technique, such as Seldinger); (3) dilational (a distinct percutaneous approach); and (4) transtracheal catheter.

The terms surgical cricothyrotomy and surgical tracheostomy refer to the use of a scalpel and other surgical instruments to create an opening in the airway.^26,27 This technique allows the creation of a definitive, protected airway by the insertion of a cuffed tracheostomy tube with an internal diameter sufficient for ventilation, oxygenation, and suctioning.

The percutaneous dilational technique utilizes a kit or device that is intended to establish a surgical airway without requiring a formal surgical cricothyrotomy (see Chapter 30 for a detailed discussion). Following a small skin incision, the airway is accessed by a small needle through which a flexible guidewire is passed using the Seldinger technique. The airway device is then introduced over a dilator and passed over the guidewire and into the airway in a manner analogous to that of central line placement. An alternative percutaneous technique has been used that relies on placement of an airway device using a direct puncture into the airway; an example is the Nu-Trake Adult Emergency Cricothyroidotomy Device (Smiths Medical, Keene, NH). A large-bore metal needle or a sharp trocar within the catheter is used to puncture the airway directly, without the use of a guidewire. Direct puncture devices are more hazardous and have fallen out of favor because of a higher incidence of complications and a lower success rate compared with other percutaneous techniques.^28–32

Transtracheal catheter ventilation, considered the least invasive surgical technique, involves the direct placement of a moderate-bore catheter through the CTM.³³ The small caliber of these devices does not allow adequate oxygenation without attachment to a high-pressure oxygen source or jet ventilator, except in small children, and does not support adequate ventilatory gas exchange. A 6-F reinforced fluorinated ethylene propylene, kink-resistant emergency transtracheal airway catheter (Cook Critical Care, Bloomington, IN) has been designed as a kink-resistant catheter for this purpose.

D Role of the Surgical Airway

The relative merit of percutaneous dilatational tracheostomy versus open surgical tracheostomy continues to be a subject of debate. Although formal open tracheostomies are primarily performed by surgeons, the percutaneous dilatational tracheostomy is frequently performed by anesthesiologists and other nonsurgical intensivists, particularly in the intensive care setting. This technique was originally described by Toye and Weinstein in 1969, but it did not gain popularity until the results with a modified device were reported by Ciaglia and colleagues in 1985.^12,15 There have been no clinical studies to date demonstrating the superiority of any one approach over another or of any of these devices over formal surgical cricothyrotomy.

A Bones and Cartilages

The horseshoe-shaped hyoid bone is the most cephalad rigid structure in the anterior neck, palpable approximately one finger breadth cephalad to the laryngeal prominence. It suspends the larynx during phonation and respiration by the thyrohyoid membrane and muscle.

The thyroid cartilage is the largest structure of the larynx and consists of two laminae fused in the midline to form the laryngeal prominence. The angle of this fusion is more acute in males, creating the more distinct prominence known as the Adam’s apple. The separation of the laminae superiorly forms the palpable superior thyroid notch. The laryngeal prominence of the thyroid cartilage represents the most readily and consistently identified landmark in the neck when one is performing a surgical airway. The superior and inferior cornua of the thyroid cartilage are the posterior extensions of the upper and lower edges of the lamina. The thyrohyoid ligament attaches to the superior cornu, and the posterior cricoid cartilage articulates with the inferior cornu.

The cricoid cartilage, the only complete cartilaginous ring in the upper airway, defines the inferior aspect of the larynx (Fig. 31-1). It is shaped like a signet ring, with the wider lamina posterior. Superiorly, the lamina has synovial articulations with the arytenoids and thyroid cartilage. Anteriorly, the cricoid ring is attached to the inferior thyroid cartilage by the CTM.

Figure 31-1 Surface anatomy of the larynx.

(From Walls RM, Luten RC, Murphy MF, Schneider RE: Manual of emergency airway management, ed 2, Philadelphia, 2004, Lippincott Williams & Wilkins.)

B Cricothyroid Membrane

The CTM is a fibroelastic tissue that covers the cricothyroid space, between the thyroid cartilage and the cricoid ring. It is trapezoidal in shape and in the average adult is 1 cm high and 2 to 3 cm wide. It is located in the midline, approximately 2 to 3 cm below the laryngeal prominence. The vocal cords are located 1 cm above the CTM and therefore are rarely injured during a cricothyrotomy.

Several anatomic characteristics make this membrane an ideal choice for emergency airway access. It is a subcutaneous structure located just beneath the skin, a small amount of subcutaneous fat, and the anterior cervical fascia in most patients. Accordingly, it is easily palpated as a depression inferior to the thyroid cartilage, bounded on its inferior aspect by a hard ridge, the cricoid cartilage. The ligament does not calcify with age. It has no overlying muscles, major vessels, or nerves. It is supported by the anterior cervical fascia, which is not robust at this level.

C Vascular Structures

The major arteries of the neck always lie deep to the pretracheal fascia and should not present a concern when incising the skin over the CTM. The paired superior thyroid arteries arise from the external carotid arteries, superior and lateral to the cricoid cartilage. The anterior branches of these arteries run along the upper thyroid isthmus to anastomose in the midline. The unpaired inferior thyroid artery also anastomoses with the superior thyroid artery at the isthmus. In 10% of the population, the potentially large thyroid ima artery ascends anterior to the trachea to join the anastomoses. A large venous plexus is found over the thyroid isthmus.

The right and left cricothyroid arteries are branches of the right and left superior thyroid arteries, respectively, and in most patients they cross the superior aspect of the CTM to anastomose in the midline.³⁴ Although they are at risk for injury during a cricothyrotomy, they do not appear to be clinically significant. Bleeding is often self-limited and is easily controlled with gauze packing. There is no venous plexus over the CTM.

D Thyroid Gland

The isthmus of the thyroid gland lies anterior to the trachea, generally between the second and third tracheal rings, although it may extend to the first and fourth rings. Its size and location can be variable; however, its average height and thickness are 1.25 cm. A pyramidal lobe of the thyroid gland is present in one third of the population and extends superiorly from the isthmus, over the cricoid membrane and larynx to the left of the midline.

E Anatomic Variations

In infants, the hyoid bone and cricoid cartilage are the most prominent structures in the neck. The laryngeal prominence does not develop until adolescence. The larynx also starts higher in the neck of the child; it descends from the level of the second cervical vertebra at birth to the level of the fifth or sixth in the adult.³⁵ The laryngeal prominence is more acute and therefore more prominent in adult males compared with females. This also results in longer vocal cords and accounts for the deeper voices of males.

The CTM varies in size among adults and can be as small as 5 mm in height. This space may narrow further with contraction of the cricothyroid muscle.³⁶ The CTM in the child is disproportionately smaller in area than that in the adult (Fig. 31-2). In an infant, the width of the membrane constitutes only one fourth of the anterior tracheal diameter, as opposed to three fourths in the adult. Because of this smaller area and the difficulty in identifying landmarks in children, emergency surgical cricothyrotomy is difficult and hazardous in small children and is not recommended in those younger than 10 years of age. In this age group, placement of a needle catheter with percutaneous transtracheal ventilation is the preferred method.

Figure 31-2 Anatomic differences in the pediatric compared with the adult airway: (1) higher, more anterior position for the glottic opening; (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) the cricoid ring is the narrowest portion of the pediatric airway (in the adult, the narrowest portion is the vocal cords); (5) different position and size of the cricothyroid membrane (CTM) in the infant; (6) sharper, more difficult angle for nasotracheal intubation; (7) larger relative size of the occiput in the infant. See text for details.

(From Walls RM, Luten RC, Murphy MF, Schneider RE: Manual of emergency airway management, ed 2, Philadelphia, 2004, Lippincott Williams & Wilkins.)

Identification of landmarks in the obese, edematous, or traumatized neck can be difficult. The CTM usually lies 1.5 finger breadths (using the patient’s fingers) below the laryngeal prominence. Alternatively, its location may be estimated to be three to four finger breadths above the suprasternal notch when the neck is in a neutral position.

There can be significant variation in the arterial and venous pattern in the anterior vessels of the neck, which can result in a major artery’s crossing the midline. This is rarely a problem for cricothyrotomy, because most anomalous vessels are present lower in the neck.

A Indications and Contraindictions

The primary indication for an emergent surgical airway (Box 31-1) is the failure of endotracheal intubation or alternative noninvasive airway techniques in a patient who requires immediate airway control. The American Society of Anesthesiologists (ASA) DA algorithm advocates a surgical airway as the final end point for the unsuccessful arm of the emergency pathway.^37,38 There are a number of other DA algorithms in the literature, as well as numerous modifications of the ASA guidelines; however, all comprehensive pathways include the surgical airway as the technique of choice when others have failed.^38–40 Despite the introduction of numerous alternative rescue devices, the most common error in the management of the DA is persistent attempts at laryngoscopy in a failed airway situation.^41–43 This behavior has been associated with increased morbidity and mortality.⁴¹ Identification of the CICV scenario should result in immediate consideration of surgical airway access. If alternative methods are tried despite inability to oxygenate and ventilate the patient by bag and mask, precious time may be lost in what are ultimately futile attempts, and by the time cricothyrotomy is undertaken and accomplished, delays in achieving airway control and oxygenation will have led to hypoxic brain injury.

In most circumstances, cricothyrotomy is regarded as an emergency rescue technique when other noninvasive rescue techniques, such as the laryngeal mask airway, have failed, are predicted to fail, or are unavailable.¹ There are occasions, however, when a cricothyrotomy is the primary airway of choice. An example is the patient who has such severe facial trauma that nasal or oral approaches to the airway are deemed impossible. There also has been a renewed interest in the role of elective cricothyrotomy in the operative setting. Some cardiothoracic surgeons prefer cricothyrotomy to a tracheostomy in their patients with a median sternotomy, believing that the higher location of the airway wound reduces the potential for contamination of the sternal wound.¹¹ A study described the use of elective cricothyrotomy instead of tracheostomy in the intensive care unit for trauma patients with technically challenging neck anatomy. The procedure was described as simpler with no difference in short- or long-term complications.⁴⁴

Cricothyrotomy is considered safe in trauma patients with unstable cervical spine injuries provided that cervical spine immobilization is maintained.^45,46 Although coagulopathy has been described as a relative contraindication, there are reports of successful cricothyrotomy after systemic fibrinolytic therapy for acute myocardial infarction.⁴⁷

Often, the main hurdle to performing cricothyrotomy is simply making the initial decision to forego further attempts at laryngoscopy or with other rescue devices and to proceed with a surgical airway. Noninvasive airway management methods are used so successfully that cricothyrotomy is often viewed as a procedure that will never be required. However, the single-minded pursuit of multiple noninvasive airways with resultant delay in the initiation of a surgical airway can result in hypoxic disaster, particularly if the patient is not able to be oxygenated and ventilated adequately with a bag and mask between attempts.

The decision to proceed to a surgical airway must also take into account some other important variables. The airway provider must appreciate whether the surgical airway will bypass the airway problem anatomically. For example, if the obstructing lesion is infraglottic, performing a cricothyrotomy may be a critical waste of time. The patient’s anatomy and pathology must be considered when weighing the difficulty of performing a cricothyrotomy. Placement of the initial skin incision is based on palpation of the pertinent anatomy. Adiposity, burns, trauma, or infection may make palpation difficult; they do not represent absolute contraindications, but the strategy may need to be adjusted. The operator must also consider the type of invasive technique (i.e., open surgical or percutaneous). This consideration takes into account provider preference based on experience, the patient’s presentation, and equipment availability.

Contraindications for surgical airway management are few and, with one exception, are relative. That one exception is young age. Children have a small, pliable, mobile larynx and cricoid cartilage, making cricothyrotomy extremely difficult. For children younger than 10 years, unless the larynx and cricoid cartilage are teenage or adult sized, percutaneous transtracheal ventilation should be used as the surgical airway management technique of choice. Two other situations have been proposed as absolute contraindications: tracheal transection and laryngeal fracture.⁴⁸ In either situation, tracheostomy has been recommended as the preferred method. Although anatomically and philosophically appealing, this assertion is clinically impractical. First, these injuries may not be readily apparent at the bedside. Second, there may be no other means of securing the airway in a dying patient. Third, expert surgical backup may not be readily available, and tracheostomy is a much more complicated procedure than cricothyrotomy. Therefore, these, too, should be considered relative contraindications; cricothyrotomy should be recognized as carrying significant risk in these situations and used when there is thought to be no other method to secure the airway. Relative contraindications also include preexisting laryngeal or tracheal pathology such as tumor, infections, or abscess in the area in which the procedure will be performed; hematoma or other anatomic destruction of the landmarks that would render the procedure difficult or impossible; coagulopathy; and lack of operator expertise.

The presence of an anatomic barrier in particular should prompt consideration of alternative techniques that might result in a successful airway. However, in cases in which no alternative method of airway management is likely to be successful or timely enough, cricothyrotomy should be performed without hesitation. The same principles apply for both the cricothyrotomy and percutaneous transtracheal ventilation. Percutaneous transtracheal ventilation is the surgical airway method of choice for children younger than 10 years of age. The cricothyrotomes have not been demonstrated to improve success rates or time or to decrease complication rates when compared with surgical cricothyrotomy. As with formal cricothyrotomy, experience, skill, knowledge of anatomy, and adherence to proper technique are essential for success when a cricothyrotome is used. The large size and cutting characteristics of the insertion part of the cricothyrotome are likely to cause more damage in the neck than either an open cricothyrotomy or a Seldinger-based technique.