Chapter 6 Few clinical scenarios are as critical as when a patient’s airway cannot be controlled with traditional endotracheal (ET) intubation. Although cricothyroidotomy is rarely required,1–4 the incidence of surgical airways has decreased even further since the advent of adjunctive intubation techniques.5,6 The conditions accompanying an airway emergency are often stressful and chaotic and require the emergency department (ED) physician to be intimately familiar with this procedure. Identify the cricothyroid membrane between the previously mentioned structures as a shallow depression measuring about 9 mm longitudinally and 30 mm transversely. If the depression is obscured by soft tissue swelling, estimate the location of the cricothyroid membrane at about 2 to 3 cm inferior to the laryngeal prominence or four fingerbreadths above the sternal notch.7–9 The area overlying and immediately adjacent to the cricothyroid membrane is relatively avascular and free of other significant anatomic structures. The cricothyroid arteries branch from the superior thyroid arteries and may form a small anastomotic arch traversing the superior aspect of the cricothyroid membrane. The external branch of the superior laryngeal nerve runs along the lateral aspect of the larynx and innervates the cricothyroid muscles inferior to the membrane. The isthmus of the thyroid gland most often overlies the second and third tracheal rings, although an aberrant pyramidal lobe of the gland may extend just superior to the cricothyroid membrane. The anterior attachments of the vocal cord structures are protected by the thyroid cartilage10,11 (Fig. 6-1). In children, the larynx is positioned more superiorly than in adults.12 There is also more overlap between the thyroid cartilage and the cricoid cartilage, thus making the cricoid membrane proportionally smaller13 (Fig. 6-2). The chief indication for surgical cricothyrotomy is an inability to secure the airway with less invasive techniques in a patient with impending or ongoing hypoxia.14 Surgical cricothyrotomy, like any invasive procedure, is associated with significant complications and should not be attempted until less invasive measures have failed. No simple algorithm fits all cases. When time and the clinical situation allow, it may be appropriate to attempt to intubate multiple times with traditional laryngoscopy or to try alternative intubation techniques. Emergency decisions are subject to controversy and differ on a case-by-case analysis, but alternatives to cricothyrotomy include bag-valve-mask ventilation, the gum elastic bougie, and laryngeal mask airways. At some point, further attempts at intubation become futile and the benefits of a surgical airway outweigh the risks associated with ongoing hypoxia.15 When approaching a patient with a compromised airway, the clinician must have a clear potential algorithm in mind with a well-defined plan that shifts the airway approach from laryngoscopy to alternative techniques to cricothyrotomy.16 The first step in deciding whether cricothyrotomy is indicated is anticipating a possible difficult intubation.17 Several studies in the anesthesia and emergency medicine literature have attempted to identify predictors of a difficult airway. A Mallampati score can be determined in cooperative patients who are able to sit upright. It classifies the degree that the faucial pillars, soft palate, and uvula can be visualized (Fig. 6-3). A higher score predicts a more difficult ET intubation.18 A Mallampati score can be obtained only in a limited number of ED patients requiring intubation.19 A modified LEMON score, when excluding the Mallampati score, is more easily applied to ED patients for prediction of more difficult ET intubation20 (Fig. 6-4). Additional indicators of a difficult airway include obesity, oropharyngeal edema, hemorrhage, and laryngospasm21–24 (Box 6-1). Cricothyrotomy is indicated when a difficult airway becomes a “failed airway,” and this is somewhat difficult to define in emergency medicine. The American Society of Anesthesiologists suggests defining a failed airway as an inability to maintain oxygen saturation greater than 90%, signs of inadequate ventilation (cyanosis, absent breath sounds, hemodynamic instability) with positive pressure bag-mask ventilation, or more than three failed attempts at ET intubation or failure to intubate after 10 minutes by an experienced operator.25 As more rescue airway adjunctive devices such as the laryngeal mask airway, gum elastic bougie, or lighted stylet become available, it is reasonable to continue beyond three attempts at ET intubation if adequate ventilation and oxygen saturation greater than 90% can be maintained.26,27 Because of the anatomic differences between children and adults, including a smaller cricothyroid membrane and a rostral, funnel-shaped, and more compliant pediatric larynx, surgical cricothyrotomy has been contraindicated in infants and young children. The exact age at which surgical cricothyrotomy can be done is controversial and not well defined. Various textbooks list the lower age limit from 5 years28 to 10 years29 or 12 years.30 The advanced cardiac life support (ACLS) and pediatric advanced life support (PALS) define an infant airway as age up to 1 year and a child airway as age 1 to 8 years. Some authors also identify tracheal transection or low tracheal obstruction (below the cricoid) as absolute contraindications to cricothyrotomy because of the need to secure the airway below the injury31 (Box 6-2). The equipment necessary to perform a traditional surgical cricothyrotomy includes a scalpel with a No. 11 blade, a Trousseau dilator, a tracheal hook, and a tracheostomy tube or modified ET tube (see Review Box 6-1). Bent 18-gauge needles may substitute for tracheal hooks. In addition, the sterile tray may include a syringe and lidocaine with epinephrine for local anesthesia, sterile drapes or towels, antiseptic preparation solution, 4 × 4-cm sterile gauze, scissors, hemostats, and suture material. The average adult’s cricothyroid membrane is about 9 mm longitudinally and 30 mm horizontally. Familiarity with the dimensions of several standard tracheostomy and ET tubes is essential when selecting the appropriate size for surgical airways. Cuffed tracheostomy tubes are recommended, and they come in various sizes. Shiley tracheostomy tubes are commonly available in most EDs. The No. 4 tube has an inner diameter (ID) of 5.0 mm and an outer diameter (OD) of 9.4 mm, and the No. 6 tube has an ID of 6.4 mm and an OD of 10.8 mm. Shiley tracheostomy tubes come with three parts: a cuffed outer cannula, a removable inner cannula, and a removable obturator that is solid and removed after insertion (Fig. 6-5). ET tubes are often used temporarily in place of a tracheostomy tube. With respect to ID, ET tube OD can vary with the manufacturer. As an example, the Mallinckrodt TaperGuard Evac Endotracheal Tube with IDs of 6.0 and 8.0 mm have ODs of 9.0 and 11.8 mm, respectively.32 Although a No. 11 scalpel blade is most commonly used, a No. 20 blade is recommended in some variations of the technique. Commercially available kits include the Melker Cricothyrotomy Kit (Cook Critical Care, Bloomington, IN) for percutaneous cricothyrotomy, which uses the Seldinger technique to insert a cuffed or uncuffed airway catheter. Positioning plays a critical role in success, but the ideal patient position may be impossible because of clinical parameters. For example, hypoxic patients often cannot recline. Ketamine anesthesia does not suppress the respiratory drive and may aid in patient cooperation and positioning. When feasible, use the supine position with the neck exposed. Unless the patient has a known or suspected cervical spine injury, it is important to hyperextend the neck to more readily identify the landmarks. Surgical cricothyrotomy can safely and successfully be performed with minimal cervical spine movement.33 Preoxygenate the patient by bag-mask ventilation. Prepare the skin of the anterior aspect of the neck with antiseptic solution and create a sterile field with the use of drapes or towels. If the patient is awake or responding to pain, give a subcutaneous and translaryngeal injection of lidocaine with epinephrine as a local anesthetic. Test the integrity of the balloon on the tracheostomy or ET tube by injecting it with 10 mL of air. Wear sterile gloves and take standard precautions by wearing a mask, goggles, and gown. All preparatory steps are optional and depend on the urgency of the procedure. The “traditional” (open) cricothyrotomy technique (Fig. 6-6) has changed little since the original description of elective cricothyroidotomy by Brantigan and Grow in 1976.34 McGill and colleagues35 described the addition of a tracheal hook for emergency cricothyrotomy in 1982. In a follow-up report in 1989, Erlandson and colleagues36 emphasized the importance of making an initial vertical skin incision and using a relatively small (No. 4 Shiley) tracheal tube. These modifications have generally been accepted and are commonly described as part of the traditional technique.37 If you are right hand dominant, stand on the patient’s right side. Stabilize the larynx with the nondominant hand by grasping both sides of the lateral thyroid cartilage with the thumb and middle finger. Palpate the depression over the cricothyroid membrane with the index finger. Control the larynx throughout the procedure by stabilizing it in this manner (Fig. 6-6, step 1). If the laryngeal landmarks are not easily identifiable because of obesity or swelling, bedside ultrasonography may assist in identifying the cricothyroid membrane38,39 (Fig. 6-7). While holding the scalpel with a No. 11 blade in the dominant hand, make an approximately 2- to 3-cm vertical incision through the skin and subcutaneous tissue (Fig. 6-6, step 2). With the index finger of the nondominant hand, palpate the cricothyroid membrane through the incision. It is important to understand that the remainder of the procedure should be performed by palpation of the anatomy, not visualization, because bleeding may obscure the field and there is no time to delay while trying to achieve hemostasis. If the cricothyroid membrane cannot be palpated, extend the initial incision superiorly and inferiorly and try to palpate again. Using the stabilizing index finger as a guide, make a horizontal incision of less than 1.0 cm in length through the cricothyroid membrane (Fig. 6-6, step 3). Note that the skin incision is vertical but the membrane incision is horizontal. Place the index finger into the stoma momentarily to exchange the scalpel for the tracheal hook.40 Using the dominant hand, place the tracheal hook into the opening in the cricothyroid membrane. Rotate the handle cephalad while grasping the inferior border of the thyroid cartilage with it. Ask an assistant to provide upward traction or provide traction yourself by passing the handle of the hook to the nondominant hand (Fig. 6-6, step 4). Use the tracheal hook to stabilize the larynx and keep it in place throughout the remainder of the procedure. With the dominant hand, place the tips of the Trousseau dilator into the opening in the membrane with the spreading action oriented initially in the longitudinal or vertical plane so that the handle is facing horizontal or perpendicular to the direction of the neck (Fig. 6-6, step 5). This instrument works opposite that of most ordinary instruments, such as hemostats. Squeezing the handles opens rather than closes the blades. This can be confusing the first time you use this instrument, and it is worth practicing before you need it in an emergency. If this instrument is not available in an emergency, Mayo scissors, a hemostat, or even the blunt end of a scalpel handle can be used to dilate the incision in the cricothyroid membrane.41 Dilate the incision vertically with the Trousseau dilator. Hold the handles of the Trousseau dilator with the nondominant hand and rotate the handle 90 degrees until the handle is vertical or parallel to the neck (Fig. 6-6, step 6). Perform this rotation because if the dilator is still horizontal, the blades of the dilator prevent passage of the tracheostomy tube into the trachea. Prepare the tracheostomy tube by testing the balloon, removing the inner cannula, and inserting the solid white obturator. While holding the dilator with the nondominant hand, take the tube in the dominant hand and insert it between the blades of the dilator until the flanges rest against the skin of the neck (Fig. 6-6, step 7). Keep the thumb on the obturator throughout the procedure. Carefully remove the Trousseau dilator (Fig. 6-6, step 8). Remove the obturator and insert the inner cannula. Inflate the balloon (Fig. 6-6, step 9). Remove the tracheal hook while being especially careful to not puncture the cuff.42,43 If a tracheostomy tube is not available or if there is difficulty placing the tracheostomy tube into the opening in the cricothyroid membrane, try using a 6-0 cuffed ET tube cut to a shorter length. The ID/OD ratios of tracheostomy tubes are comparable to those of ET tubes. Use of a gum elastic bougie may facilitate and even hasten placement of an ET tube through the cricothyroid membrane into the trachea.44 The advantage of using the bougie is that you can get immediate confirmation that the device is inside the trachea because of the “washboard” vibration that the curved tip makes as it contacts the tracheal rings.45 Modify the ET tube by cutting the distal end and replacing the adapter to the cut end (Fig. 6-8). Be careful to not cut the pilot balloon or inflation port. If the ET tube is shortened, it is less likely to kink once it is attached to a ventilator. Advance the ET tube only about 5 cm from the tip to avoid main stem intubation. Keep in mind that standard ET tubes do not have centimeter markings at the distal end. Inserting the ET tube so that the distal cuff is about 2 cm beyond the cricothyroid membrane usually ensures proper placement. Confirm proper placement in the same manner as with ET tube placement: end-tidal CO2, bilateral chest movement, and breath sounds. Secure the tracheostomy tube with a circumferential tie around the neck or with sutures (Fig. 6-6, step 10). Order a postprocedure portable chest radiograph. Brofeldt and colleagues46 developed a rapid four-step technique (RFST) to decrease the amount of time required to establish an airway and reduce complications of hypoxia. It combines aspects of traditional cricothyroidotomy and ET intubation. For right hand–dominant operators, stand at the bedside to the patient’s left. Palpate the depression over the cricothyroid membrane with the nondominant hand (Fig. 6-9, step 1). With the dominant hand, make a single horizontal stab incision with a No. 20 scalpel blade approximately 1.5 cm in length through the skin, subcutaneous tissue, and cricothyroid membrane (Fig. 6-9, step 2). With the scalpel blade as a guide, pick up the cricoid cartilage with the tracheal hook and provide traction in the caudal direction to stabilize the trachea (Fig. 6-9, step 3). Place a No. 4 cuffed tracheostomy tube or a 6-0 cuffed ET tube through the opening (Fig. 6-9, step 4). Because this technique omits dilating the stoma with the Trousseau dilator, it may be more difficult to pass a tracheostomy tube. A gum elastic bougie, using the Seldinger technique, may assist in this step.46 Bair and colleagues47 modified this technique further by introducing a new device called a “Bair Claw” to replace the tracheal hook. The technique is similar to the four-step method except for positioning the operator at the head of the bed instead of the patient’s side and the use of a double-hook device rather than a single hook. By replacing the single hook with the double hook, they found a decrease in the incidence of cricoid ring fractures in cadavers (Fig. 6-10). Preparation for this technique is similar to that for the other techniques. Palpate the cricothyroid membrane with the nondominant hand. With the dominant hand, attach the needle to the syringe and insert it through the cricothyroid membrane pointing caudally at a 45-degree angle relative to the skin surface (Fig. 6-11, step 1). Be careful to not advance the needle too far because this may result in perforation of the posterior aspect of the trachea. To help recognize when the trachea has been entered, place a small amount of saline in the syringe before the procedure. Apply gentle negative pressure while advancing the syringe. When the membrane is pierced and the trachea is entered, air will be aspirated into the syringe and air bubbles will appear in the saline.
Cricothyrotomy and Percutaneous Translaryngeal Ventilation
Anatomy
Surgical Cricothyrotomy
Indications and Contraindications
Equipment
Procedure
Traditional Technique
Rapid Four-Step Technique (Brofeldt)
Melker Percutaneous Cricothyrotomy Technique
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Cricothyrotomy and Percutaneous Translaryngeal Ventilation
