29 Jan 2020

The Difficult Airway: Implications for General Anesthesia

Airway management is crucial to an anesthesia provider’s practice, as patients often need assisted ventilation while under general anesthesia.1 Airway management includes intubation and mask ventilation, and requires tools such as laryngoscopes and supraglottic devices.2 Intubation is a procedure that entails placing a tube into the trachea (i.e., windpipe) to keep the airway open and protect the lungs from aspiration of any contaminants.3 An endotracheal tube can be placed orally, nasally, through the front of the neck or, rarely, through the floor of the mouth.3 Several devices can be used to intubate, such as flexible scope,4 and intubation may occur at various times in the perioperative period.5 Facemask ventilation, another important part of airway management, is used to provide gases to the patient and aid in oxygenation.6 Some patients may present with difficult airways due to anatomical or physiological differences, thus making intubation or mask ventilation more complex.7 Improper airway management can lead to grave complications, such as brain damage or death;5 in fact, 25 to 46 percent of anesthesia-related deaths are associated with difficult airways.8 Anesthesia providers can take steps before and during surgery to avoid airway-related morbidity in patients with difficult airways.

            When possible, preoperative identification of a difficult airway can help in the preparation for intubation or mask ventilation.1 The incidence of difficult intubation ranges from one to 8 percent, while the incidence of difficult mask ventilation ranges from 1.4 to 7.5 percent.8 In order to avoid an unexpected difficult airway, anesthesia providers can preoperatively assess patients’ health histories to identify potential issues. According to a study by Shah and Sundaram, snoring, obstructive sleep apnea, retrognathia (underbite), micrognathia (undersized jaw), macroglossia (large tongue), edentulism (missing teeth) and being overweight predicted difficult mask ventilation, among other technical factors.9 Additionally, they found that difficult intubation was two to three times more common in patients with difficult mask ventilation than patients without difficult mask ventilation.9 Predictors of difficult intubation include history of difficult intubation, limited neck range of motion, small mouth opening, obesity and inability to protrude the lower jaw.8 For patients who present with risk of having a difficult airway, anesthesia providers may consider using other types of anesthesia, such as conscious sedation,10 or special video laryngoscopes.11 Regardless, a preoperative assessment is vital to anticipating difficulty in mask ventilation or intubation.7

            Even with an adequate preoperative assessment, a patient who does not present with risk factors may prove to have a difficult airway during the procedure.7 Anesthesia providers may use a video laryngoscope, which allows for easy monitoring of airway management, to smoothly and safely introduce an endotracheal tube to a difficult airway.1 Additionally, jaw lifting, proper neck position and continuous positive airway pressure can make intubation and mask ventilation easier.1 Anesthesiology practitioners should be ready for the unexpected difficult airway, which includes having a pre-formulated strategy for airway management.5 The number of attempts to intubate or place a mask and number of devices used should be standardized.7 As stated by Law et al., multiple attempts at tracheal intubation can harm the patient.12 The authors suggest a maximum of three attempts with a chosen device before switching to “Plan B.”2 Whether airway difficulty is predicted or not, anesthesia providers should work with other professionals—including other anesthesiology practitioners13 and surgeons14—to make the best decision for the patient.

            The American Society of Anesthesiologists (ASA) defines a difficult airway as problems with facemask ventilation, tracheal intubation or both.6 Anesthesia providers should conduct a thorough perioperative assessment to determine a patient’s risk level for a difficult airway. During surgery, anesthesiology practitioners must be prepared for unexpected airway difficulties. They should use proper positioning and tools to make the airway more accessible and prevent complications. In the future, groups like the ASA should establish clear standards for dealing with predicted and unpredicted airways, particularly with regard to number of intubation attempts.7

1.         Richtsfeld M, Belani KG. Anesthesiology and the difficult airway –Where do we currently stand? Annals of Cardiac Anaesthesia. 2017;20(1):4–7.

2.         Law JA, Broemling N, Cooper RM, et al. The difficult airway with recommendations for management – Part 2 – The anticipated difficult airway. Canadian Journal of Anesthesia/Journal canadien d’anesthésie. 2013;60(11):1119–1138.

3.         The Regents of the University of California. Intubation. Airway Techniques 2013; https://aam.ucsf.edu/intubation.

4.         Hagberg CA, Artime C. Flexible scope intubation for anesthesia. In: Crowley M, ed. UpToDate. Web: Wolters Kluwer; September 13, 2018.

5.         Rosenblatt WH, Artime C. Management of the difficult airway for general anesthesia in adults. In: Crowley M, ed. UpToDate. Web: Wolters Kluwer; October 30, 2019.

6.         Apfelbaum JL, Hagberg CA, Caplan RA, et al. Practice Guidelines for Management of the Difficult Airway: An Updated Report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology: The Journal of the American Society of Anesthesiologists. 2013;118(2):251–270.

7.         McNicholl DJ. The Difficult Airway. In: Aglio LS, Urman RD, eds. Anesthesiology: Clinical Case Reviews. Cham: Springer International Publishing; 2017:287–296.

8.         Ye Y, Feng T, Doyle DJ. Using Regional Anesthesia in Difficult Airway Patients. Anesthesiology News. Web: McMahon Publishing; September 3, 2018.

9.         Shah PN, Sundaram V. Incidence and predictors of difficult mask ventilation and intubation. Journal of Anaesthesiology, Clinical Pharmacology. 2012;28(4):451–455.

10.       Javid MJ, Khademian G. Dissociative conscious sedation versus airway regional blocks in patients with predicted difficult airway: Advantages and disadvantages. Archives of Anesthesiology and Critical Care. 2016;2(1):161–164.

11.       Vargas M, Pastore A, Aloj F, Laffey JG, Servillo G. A comparison of videolaryngoscopes for tracheal intubation in predicted difficult airway: A feasibility study. BMC Anesthesiology. 2017;17(1):25.

12.       Law JA, Broemling N, Cooper RM, et al. The difficult airway with recommendations for management – Part 1 – Difficult tracheal intubation encountered in an unconscious/induced patient. Canadian Journal of Anesthesia/Journal canadien d’anesthésie. 2013;60(11):1089–1118.

13.       Paix AD, Williamson JA, Runciman WB. Crisis management during anaesthesia: Difficult intubation. Quality and Safety in Health Care. 2005;14(3):e5.

14.       Ezri T, Szmuk P, Evron S, Geva D, Hagay Z, Katz J. Difficult Airway in Obstetric Anesthesia: A Review. Obstetrical & Gynecological Survey. 2001;56(10):631–641.