Surgical Airway

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Chapter 31 Surgical Airway

I Introduction

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:

1 Those Responsible for Surgical Airway Management Have Limited or No Experience

Most clinicians who are responsible for airway management have either limited or no experience with these procedures. Whether in the prehospital setting, the emergency department, the operating room, the inpatient unit, or the intensive care unit, surgical airway management is simply not required very often, largely because of high proficiency with direct laryngoscopy, increasing capability of identifying difficult airways (DAs) in advance, and the multitude of sophisticated alternative intubation devices that can be used when direct laryngoscopy is not possible or unsuccessful. The progressive diminution in use of emergency surgical airway procedures over the past two decades has many causes but is primarily the result of two evolutionary changes: (1) the shift in emphasis in trauma airway management from avoidance of oral laryngoscopy to widespread acceptance of gentle, controlled, oral laryngoscopy with in-line cervical spine immobilization and (2) the growing proficiency of clinicians from multiple specialties with rapid-sequence intubation (RSI).

Contemporary emergency department studies using RSI demonstrate high success rates (97% to 99%) and an infrequent need for surgical airway rescue (0.5% to 2.0%) even though the unselected nature of the patients and the large percentage with trauma result in a high proportion of DAs compared with those seen in elective surgery.15 Despite increasing familiarity with alternative airway rescue devices (e.g., flexible and semirigid fiberoptic bronchoscopy, video laryngoscopy, retroglottic airways, supraglottic airways, retrograde intubation, lighted stylet) that further reduce the need for cricothyrotomy, the surgical airway remains the final pathway on all failed airway algorithms.6 Therein lies the dilemma. As clinicians embrace new technologies and devices that make the need for surgical airway management increasingly rare, acquisition and maintenance of the skills necessary to perform surgical airway management, which in some cases is the only method capable of sustaining a patient’s life, become increasingly elusive.

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.810 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.13,1925

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.2832

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.

II Anatomy

An understanding of the anatomy of the upper airway and the neck is required for the successful and rapid performance of a surgical airway. Most emergent surgical techniques involve surgical fields that become rapidly obscured by blood and for this reason they are, essentially, “blind” procedures. The identification of anatomic landmarks is critical.

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.

image

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.)

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.

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.

III Surgical Cricothyrotomy

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.3840 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.4143 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

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