48.3.1 Is Active Airway Intervention Required in This Case?
The first question to be answered is whether or not this patient requires intubation. For the following reasons, the answer is "yes":
- Hypoxemia, as demonstrated by persistent low oxygen saturation in spite of maximum supplemental oxygen, contributes to secondary brain injury.
- A GCS score of less than or equal to 8 is commonly regarded as an indication for intubation to ensure adequate airway protection.24-26
- A depressed level of consciousness frequently results in hypoventilation or apnea, and resultant hypercarbia can contribute to secondary brain injury and increased intracranial pressure.
- This patient will require multisystem evaluation including potentially prolonged diagnostic imaging of both plain radiography and computed tomography (CT), and airway patency must be assured throughout.
- Depending on local policies, this patient may require transfer to a pediatric trauma center. The ability to protect the airway and provide oxygenation and ventilation is facilitated by endotracheal intubation.
In practice, this means that the airway practitioner physically positions themselves at the head of the patient and begins the process of denitrogenation. In a patient with adequate, spontaneous respirations, this may be done with a nonbreather face mask over 3 minutes. However, for this patient with persistent hypoxemia, despite maximum supplemental oxygen, 1 minute of positive pressure ventilation with a bag-mask has been shown to be an effective and more rapid alternative.27 For the spontaneously breathing child, the airway practitioner should coordinate gentle assisted breaths with the child's respiratory efforts, to avoid inflation of the stomach.
A methodical evaluation of the airway, including the potential for difficult airway may now be carried out.
48.3.2 What Challenges Do We Face in Managing This Child's Airway?
This patient does not have a crash airway (see Chapter 2, Figure 2-3) therefore immediate intubation is not indicated. The next priority is evaluating the patient for a potentially difficult airway and the suitability of rapid-sequence induction (RSI). The algorithms and mnemonics introduced in Chapters 1 and 2 are designed to guide the evaluation of the airway in such a way that important features known to predict a difficult airway are not overlooked. Although specific elements of the mnemonics may not be applicable in children, the principles remain the same. Employing the strategies for evaluating the airway for difficulty presented in Chapter 1:
- Will bag-mask-ventilation (BMV) of this patient be difficult (MOANS, see Section 1.6.1)? Mask seal is not anticipated to be difficult. This child is described as having noisy breathing which may signify some degree of upper airway obstruction. Given the depressed mental status, this is likely a result of an obstructing tongue which can be easily overcome with a simple jaw thrust or using oral or nasal airways. Obviously, this patient is not aged (older than 65), is not edentulous, and is not stiff (increased resistance or reduced compliance). However, the potential for acute gastric dilation to compromise thoracic compliance exists and must be addressed as indicated. So, evaluation using MOANS does not indicate any likely difficulties with bag-mask-ventilation.
- Will the insertion of an extraglottic device (EGD) be difficult (RODS, see Section 1.6.3)? Mouth opening can be limited by neck immobilization. However, this can be easily addressed by opening the front of the hard collar and maintaining in-line stabilization. Airway obstruction at or above the glottis is not suspected. There is no airway distortion to prevent a seal with an EGD, although the inability to move the neck may hinder seal characteristics of an LMA. Stiffness was evaluated with MOANS.
- Will a surgical airway be difficult (SHORT, see Section 1.6.4)? A 7-year-old has a small cricothyroid membrane. Therefore, a surgical cricothyrotomy will rarely be successful and should not be attempted in most circumstances. The surgical procedure of choice will be a transtracheal cannula. (see also Chapter 42). Ventilation through the transtracheal catheter may be performed manually with a bag-mask unit, with a jet ventilation device attached to a wall outlet with the initial pressure reduced to 20 lb per square inch (PSI), or with an Enk Flow Modulator (Cook Critical Care, see Chapter 59 for contact information) attached to a wall flowmeter at 7 L·min−1 (1 L·min−1 for each year of age).28 This particular patient would not be expected to have any other potential problems with a surgical airway, that is, no prior neck surgery, no hematoma or infection over the anterior neck, no obesity, no radiation therapy, and has no tumor in the airway.
- Will it be difficult to perform laryngoscopy or intubation in this patient (LEMON, see Section 1.6.2)? Looking at the patient reveals no gross features that might predict a difficult laryngoscopy or intubation. The evaluation (3-3-2) of the geometry of his mandible and the position of his larynx (using the patient's own fingers) is normal. Mouth opening is adequate, although one is unable to evaluate a Mallampati score in this obtunded patient. There is no significant upper airway obstruction. The neck (cervical spine) is treated as if there could be a potential injury and therefore in-line stabilization is maintained. However, this is not of sufficient concern that an awake intubation is indicated.
Thus, in the absence of a difficult airway, the decision is made to proceed with a rapid-sequence intubation (RSI) as per Figure 2-3 in Chapter 2. Plan A is routine RSI. Plan B is an EGD such as an LMA. The use of the Combitube™ for this patient would not be appropriate as the patient has yet to reach 48 in (approximately 120 cm) in height. Plan C is a transtracheal cannula approach.
48.3.3 How Exactly Does One Proceed with an RSI in This Patient?
Reflecting the previous discussion, several factors will influence how RSI is accomplished:
- This patient has an acute severe head injury with the potential for elevated intracranial pressure (ICP).
- Prior to clearing the cervical spine with appropriate radiologic procedures, in-line stabilization is provided by a trained individual dedicated entirely to this task.
- A full stomach and acute gastric dilation are assumed.
- Hemodynamic compromise is possible, as indicated by persistent tachycardia.
Equipment for Plans A, B, and C are assembled and tested. Drugs are drawn up as per the Broselow-Luten System (Vital Signs, Inc., Totowa, NJ). A functioning suction with a Yankauer catheter should be readily available given the potential for blood or secretions in the hypopharynx, and the risk of regurgitation of gastric contents.
Bag-mask-assisted ventilation is already underway.
The efficacy of lidocaine in attenuating the rise in ICP during laryngoscopy and intubation is controversial.29-32 However, if it is to be effective, it should be given a minimum of 2 to 3 minutes prior to intubation and at a dose of 1.5 mg·kg−1 or 45 mg for this patient.33,34 Fentanyl has not been shown to effectively blunt increases in ICP during intubation in children, and is specifically omitted as hemodynamic instability is suspected. Reduced muscle mass in children translates to less concern for fasciculations affecting ICP; therefore defasiculating doses with nondepolarizing neuromuscular-blocking (NMB) agent are not needed. Atropine has historically been used to prevent bradycardia related to succinylcholine use. However, recent studies have suggested this may be unnecessary.35 Atropine use is considered optional in children less than 1 year of age who are at increased risk of bradycardia related to laryngoscopy. For older children such as this patient, it is recommended that atropine be available for rapid administration if bradycardia develops during intubation.
184.108.40.206 Potential Cervical Spine Injury
In-line stabilization is maintained throughout.
220.127.116.11 Induction and Paralysis
Since hemodynamic instability is suspected, a reduced dose of etomidate from 0.3 to 0.2 mg·kg−1 or 6.0 mg is selected as the induction agent and is administered rapidly. Ketamine 1.0 to 2.0 mg·kg−1 is an effective induction agent that has recently gained favor in hemodynamically compromised patients because of resultant release of endogenous catecholamines. However, this pressor response has raised questions about worsening ICP in head-injured patients. Recent suggestions are that ketamine can safely be used in head-injured patients who do not exhibit obvious hypertension.36 Succinylcholine 1.5 mg·kg−1 or 45 mg for this patient is administered rapidly after the induction agent is injected. Unlike the induction agent, the dose of the NMB agent is never tailored to the hemodynamic status.
18.104.22.168 Protection Against Aspiration
Cricoid pressure is applied with care taken to:
- Avoid stimulation of gag during induction
- Avoid cervical spinal motion
- Not obstruct or deform the relatively compliant airway of the child
Although artificial ventilation in this child is risky due to the potential for gastric insufflation and regurgitation, there is little choice but to perform careful BMV in order to maintain normal arterial carbon dioxide levels and mitigate increases in ICP. In addition, appropriately applied cricoid pressure decreases the risk of further gastric insufflation.37,38
22.214.171.124 Placement of the Endotracheal Tube
The placement of the endotracheal tube is performed under direct laryngoscopy as delicately and atraumatically as possible to attenuate any increase in blood pressure, heart rate, and ICP. Tracheal tube placement is confirmed with end-tidal CO2 detection and a complete clinical evaluation, including auscultation. Immediately after intubation, the blood pressure is assessed. If the child is hypertensive for age, this can be managed with appropriate sedation and analgesia with opioids and benzodiazepines or with small bolus doses of propofol. Conversely, if hypotension is noted, volume infusion, up to 20 mL·kg−1 of balanced salt solution should be rapidly administered.
If the endotracheal tube is inadvertently placed in the esophagus, the tube may be immediately removed and intubation reattempted. Alternatively, one of the following two maneuvers may be employed, depending on the oxygen saturation:
- Oxygen saturation greater than 90%: move the incorrectly positioned tube to the left corner of the mouth and reattempt intubation with a second tube, with careful attention to the relative position of the known esophageal tube.
- Oxygen saturation less than 90%: quickly inflate the balloon of the ETT with as much air as it will accommodate without breaking (ordinarily 5.0-15 mL depending on the size of the ETT). Compress the epigastrum to empty as much air and liquid stomach contents as possible. Deflate the balloon and remove the ETT while suctioning the hypopharynx. Perform BMV to recover the oxygen saturations and reattempt orotracheal intubation.
If at any point oxygen saturation becomes unacceptable and cannot be corrected, a failed airway has supervened and the appropriate algorithm should be followed.
126.96.36.199 Postintubation Management
Maintaining hemodynamic stability with acceptable blood gases (Paco2 35-40 mm Hg) should become a priority after successful tracheal intubation. Routine hyperventilation is no longer advised due to decreased cerebral blood flow and resultant ischemia.39 Neuromuscular blockade should be continued using longer-acting nondepolarizing agents such as rocuromium (0.6-1.2 mg·kg−1), vecuronium (0.1 mg·kg−1), or pancuronium (0.1 mg·kg−1) provided repeated neurological examinations are not essential. Sedation with bolus doses of midazolam 0.5 to 1.0 mg per dose may be required from time to time, the need dictated by a rising heart rate and/or blood pressure. Opioids such as fentanyl 1.0 μg·kg−1 may be necessary if pain is suspected. One must pay particular attention to the effect of small doses of sedative hypnotics and opioids on the hemodynamic stability of the patient. Gastric decompression using an orogastric or nasogastric tube is indicated.
48.3.4 What If the Trachea Cannot Be Intubated after Three Attempts?
Failure to successfully intubate after three attempts constitutes a failed airway. There are two types of failed airways:
- Cannot intubate, can ventilate—A situation in which three attempts at conventional intubation have failed but gas exchange is possible and saturations acceptable (eg, BMV, or EGD such as an LMA). In this situation, there is time to use alternative nonsurgical techniques, such as video laryngoscopy or flexible bronchoscopy, recognizing the ongoing risk of regurgitation and aspiration.
- Cannot intubate, cannot ventilate—A situation in which neither intubation nor ventilation is possible. In such a case, there is no time for further intubation attempts and a surgical airway must be performed. In this case, an LMA may be attempted as preparations are made to insert a transtracheal catheter, but not instead of preparing to insert one, that is, these activities are concurrent not sequential.