Failed Direct Laryngotracheal Intubation Rescue
Kenneth N. Hiller
Carin A. Hagberg
A 48-year-old woman presents for laparoscopic intra-abdominal surgery. She has a body mass index of 45 kg/m2 and a neck circumference of 42 cm with an otherwise normal airway examination. She is positioned on the OR table using a specialized obesity pillow to achieve external auditory meatus—sternal notch alignment. After induction of anesthesia and mask ventilation with an oral airway, direct laryngoscopy fails on two attempts. Mask ventilation remains easy between the attempts. The patient’s trachea is intubated with a channel-type videolaryngoscope.
1 What are the anesthetic and airway management considerations for this case?
The preoperative airway physical examination reveals a significant nonreassuring finding, a thick neck, but is otherwise normal. A combination of increasing neck circumference and Mallampati score ≥3 has been associated with problematic intubation. It is recommended that neck circumference be routinely assessed during the preoperative airway evaluation, especially in obese patients.
The anesthetic and airway management considerations for this morbidly obese patient include risk of hypoxemia, pulmonary aspiration of gastric contents, a difficult airway (DA), and difficulty obtaining emergency invasive airway access. Deleterious respiratory physiologic changes in the morbidly obese patient include increase in airway resistance, oxygen consumption, and minute ventilation. Conversely, lung volumes, pulmonary compliance, chest wall compliance, and gas flows are reduced. Decreased expiratory reserve volume and functional residual capacity decline significantly following induction of anesthesia (see Chapter 17).
Several factors increase aspiration risk in the morbidly obese patient, including increased gastroesophageal reflux, reduced lower esophageal barrier pressure, and higher gastric volumes. Interestingly, recent literature suggests that gastric emptying is not impaired in obese patients and is not a primary factor in aspiration risk.
Pharyngeal obstruction resulting from “anatomical mismatch between the craniofacial bony enclosures and the amount of soft tissue” or physical obstruction from lingual tonsil hyperplasia, can increase the likelihood of experiencing difficulty with the airway in obese patients. Face mask ventilation, laryngoscopy, and emergency invasive airway access may prove more challenging. Preoperatively, attention should be paid to the recommendations of the American Society of Anesthesiologists Airway Task Force Guidelines. The practitioner should consider awake intubation if the patient has multiple airway risk factors since alternative airway management plans will likely fail.
2 How would you manage the airway in this case?
In this scenario, direct laryngoscopy has failed twice, but face mask ventilation remains adequate. Thus, the nonemergent pathway of the DA algorithm should be followed. In such a situation, the authors would attempt videolaryngoscopy (VL), and if unsuccessful, would place an intubating LMA (ILMA). VL has a high likelihood of success even in obese patients. ILMA placement is often successful since internal adipose tissue aligns the device along the midline with the glottis. It is important for the practitioner to oxygenate the patient in between intubation attempts and actively pursue opportunities to deliver supplemental oxygen throughout the process of DA management. Upon confirmation of adequate oxygenation and ventilation with an ILMA, an FIS can be used to place a tracheal tube. If an ILMA, such as the LMA Fastrach, is used, an FIS may not be necessary as this device is designed to be used as a blind technique. If unsuccessful, an FIS can be used.