By Alexander Niven, MD
Senior Associate Consultant, Division of Pulmonary/Critical Care Medicine, Mayo Clinic, Rochester, MN
Dr. Niven reports no financial relationships relevant to this field of study.
Airway management is a common, high-risk procedure in the ICU. A decade ago, ICU intubation was associated with complications in more than 50% of cases, including prolonged hypoxemia, hemodynamic instability, cardiac arrest, and death.1 Despite significant improvements in patient safety and outcomes using skilled operators, a systematic approach, and advanced airway tools, more recent publications still report a complication rate in the critically ill that remains unacceptably high. Recent evidence and guidelines help inform best airway practice in the ICU, but challenges and controversies remain.
DEFINING THE PROBLEM
Airway management in the ICU often is emergent and performed in patients with significant cardiopulmonary disease, hemodynamic instability, and upper airway abnormalities. (See Table 1.) These factors limit deliberate planning and preparation, decrease the time to perform intubation before hypoxemia develops, and reduce glottic visualization during the procedure. The result is a high incidence of difficult airways — defined as clinical factors that complicate ventilation by facemask or intubation by a skilled operator — reported to be 7-10% in this population.2,3
Current studies still report complication rates from ICU intubation of 4.2% to 22%.3-6 Hypoxemia is the most common cause of serious complications, but post-intubation hypotension also has been associated with poor patient outcomes in a large retrospective, multicenter cohort.7 ICU patients also present special management challenges for airway management, such as increased intracranial pressure and active coronary ischemia. A recent large cohort study found 47% of the critically ill patients who suffered airway complications in the Royal College of Anesthetists’ Fourth National Audit Project were obese, and the incidence of difficult intubation in this population was twice as frequent in the ICU than the OR (16.3% vs. 8.2%; P < 0.01).6,8
Multiple international studies also have documented variable staff training, limited availability of airway equipment in the ICU, and communication and teamwork errors as common causes of adverse outcomes during airway management.6,9-11 This has led some to call for anesthesiologists alone to perform intubations in the critically ill, but survey data suggest that training and performance gaps in the management of difficult airways in these patients are common, even within this specialty.12-15
A SYSTEMATIC APPROACH INCREASES SUCCESS, SAFETY
A systematic approach to airway assessment, patient and equipment preparation, and procedure planning clearly has been shown to increase the rate of intubation success. In a two-phase, multicenter, prospective study of 244 intubations, Jaber et al demonstrated that implementation of a protocolized ICU intubation bundle (see Table 2) reduced the incidence of both life-threatening and other complications by 13% and 12%, respectively.4 Implementation of a standardized, team-based approach to airway management, simulation-based airway skills and teamwork training, and a mandatory bedside procedure checklist also have been shown to improve patient safety with tracheal intubation and to reduce the need for emergent surgical airway procedures.16,17
STRATEGIES AND TOOLS TO MANAGE SUCCESS
Preoxygenation can be less effective in patients with significant cardiopulmonary disease, leaving little time for an intubation attempt before hypoxemia develops. Apneic oxygenation is the delivery of supplemental oxygen through the nasopharynx without ventilation, and has shown promise in small, nonrandomized trials examining its use in intubation outside the OR. However, in the first prospective, randomized trial to examine this issue, no difference was observed in 150 critically ill medical patients who received either 15 L/min supplemental oxygen by nasal cannula or no additional oxygen during laryngoscopy attempts. Investigators maintained a high rate of compliance with best practices of preoxygenation, patient positioning, and equipment preparation, which may have reduced the potential additional benefit of this intervention. Further, investigators also excluded patients with anticipated difficult airways, a group in whom apneic oxygenation may produce the best outcome during a prolonged intubation attempt and is recommended in current guidelines.18,19
There has been considerable interest in the use of advanced airway tools to increase the success and safety of intubation in the ICU. Videolaryngoscopy (VL), a term used to describe a wide range of intubating devices that employ a video display to provide better glottic visualization, has shown promise in small cohort studies and one randomized, controlled study. However, a recent large, prospective, randomized study comparing standard direct laryngoscopy with videolaryngoscopy in the ICU did not demonstrate a difference in the rate of first attempt success, time to intubation, or complications despite better glottic visualization in the VL group.20 Methodologic differences in this trial compared to prior positive studies included more aggressive use of neuromuscular blockade, the use of the McGrath MAC video laryngoscope instead of the GlideScope, and the exclusion of patients with anticipated difficult airways who were intubated using video or fiber optic techniques.21
Anatomic features continue performing poorly as a tool for identifying patients with a difficult airway, with the MACOCHA score the best validated tool to identify at-risk patients in the ICU.22,23 In light of this, a practical and informed approach to the unanticipated difficult airway is crucial for critical care providers. The Difficult Airway Society (DAS) published new guidelines for the management of an unanticipated difficult airway in 2015, which are summarized in Table 3.19
The guidelines emphasize the importance of adequate sedation and neuromuscular blockade to maximize glottic visualization and first pass success, preoxygenation to maximize time for intubation, and treatment at a facility with videolaryngoscopy in situations in which a difficult airway is anticipated. A gum elastic bougie also is encouraged in situations of incomplete glottic visualization, supported by its major role as a primary rescue device in prior studies.3
If initial intubation attempts are not successful, the DAS encourages early use of a second generation extraglottic airway (EGA) to preserve oxygenation, with best current evidence supporting the i-gel (Intersurgical, Wokingham, UK), the ProSeal LMA (PLMA; Teleflex Medical Europe Ltd, Athlone, Ireland), and the LMA Supreme (SLMA; Teleflex Medical Ltd). Limiting the number of EGA placement attempts to three minimizes airway trauma without reducing overall success rate. Successful placement ensures adequate oxygenation and ventilation and provides time to plan for the next step to manage the failed airway, which in the critically ill patient is most likely fiber optic intubation through the EGA or a surgical airway. For patients in whom EGA placement and repeat bag valve mask ventilation is not successful, the DAS recommends early scalpel cricothyroidotomy with placement of a wide-bore cuffed tube over a bougie as the preferred surgical airway approach.
DIFFICULT AIRWAY RESPONSE TEAMS
Some organizations have developed Difficult Airway Response Teams (DARTs) as a solution to the challenges of standardizing equipment, approach, and training in airway management in large institutions with multiple ICUs. Although DARTs offer the opportunity to deploy a multidisciplinary, well-trained airway team with standardized equipment to the bedside of an anticipated or identified difficult airway, criteria, timing, and coordination of team activation and involvement must be carefully delineated based on the volume of procedures, resources, and capabilities within the various hospital areas in which staff perform intubations. Key factors that have warranted DART activation in one institution’s experience include a history of a difficult airway, cervical spine injury or fixation, oropharyngeal and/or supraglottic angioedema, and airway bleeding.24
CONTROVERSIES AND FUTURE DIRECTIONS
The rapid evolution of airway devices and increased emphasis on sedation and neuromuscular blockade in recent airway guidelines present challenges and some controversies for many practicing intensivists. Many modern airway devices have been developed for airway management in the OR, and recent literature only further emphasizes that their appropriate roles in an airway management algorithm for the critically ill must be defined better. Although full induction doses of agents, such as propofol, that are recommended in current DAS guidelines have been shown to be safe and effective in the critically ill with preemptive vasopressor administration,24 many intensivists are less than comfortable with full-dose induction agents, neuromuscular blockers, and rapid sequence intubation protocols in critically ill patients. When and in which patients this strategy should be used also could merit further refinement.
Airway management remains a high-risk procedure in the ICU. Safety and success rates have significantly improved over the past decade with implementation of a systematic approach that emphasizes preoxygenation, appropriate patient positioning, pre-induction volume loading and vasopressor administration, teamwork and communication between skilled airway operators, and multidisciplinary teams assisting them. Recent guidelines favor early and aggressive neuromuscular blockade to maximize the chances of first-pass intubation success, along with early use of an EGA and, when necessary, scalpel cricothyroidotomy to reestablish adequate oxygenation. How best to apply these guidelines and other advanced airway tools in the critically ill still requires further study, along with an examination of the initial and maintenance training and procedural volume required for an intensivist to maintain competence in this procedure.
- Jaber S, Amraoui J, Lefrant JY, et al. Clinical practice and risk factors for immediate complications of endotracheal intubation in the intensive care unit: A prospective, multiple-center study. Crit Care Med 2006;34: 2355-2361.
- American Society of Anesthesiologists. 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 2003;98:1269-1277.
- Martin LD, Mhyre JM, Shanks AM, et al. 3,423 emergency tracheal intubations at a university hospital: Airway outcomes and complications. Anesthesiology 2011;114: 42-48.
- Jaber S, Jung B, Corne P, et al. An intervention to decrease complications related to endotracheal intubation in the intensive care unit: A prospective, multiple-center study. Intensive Care Med 2010;36:248-255.
- Simpson GD, Ross MJ, McKeown DW, Ray DC. Tracheal intubation in the critically ill: A multi-centre national study of practice and complications. Br J Anaesth 2012;108:792-799.
- Cook TM, Woodall M, Harper J, et al. Major complications of airway management in the UK: Results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 2: Intensive care and emergency departments. Br J Anaesth 2011;106:632-642.
- Green RS, Turgeon AF, McIntyre LA, et al. Post-intubation hypotension in intensive care unit patients: A multicenter cohort study. J Crit Care 2015;30:1055-1060.
- DeJong A, Molinari N, Pouzeratte Y, et al. Difficult intubation in obese patients: Incidence, risk factors, and complications in the operating theatre and in intensive care units. Br J Anaesth 2015;114:297-306.
- Porhomayon J, El-Solh AA, Nader ND. National survey to assess the content and availability of difficult-airway carts in critical-care units in the United States. J Anesth 2010;24:811-814.
- Husain T, Gatward JJ, Hambidge ORH, et al. Strategies to prevent airway complications: A survey of adult intensive care units in Australia and New Zealand. Br J Anaesth 2012;108:800–806.
- Lipshutz AKM, Caldwell JE, Robinowitz DL, Gropper MA. An analysis of near misses identified by anesthesia providers in the intensive care unit. BMC Anesthesiol 2015;15:93.
- Clarke RC, Gardner AI. Anesthesia trainees exposure to airway management in an Australian tertiary care teaching hospital. Anaesth Intensive Care 2008;36:513-515.
- Koppel JN, Reed AP, Hagberg CA, et al. Instruction of airway management skills during anesthesiology residency training. J Clin Anesth 2003;15:149-153.
- Rostenstock C, Østergaard D, Kristensen MS, et al. Residents lack knowledge and practical skills in handling the difficult airway. Acta Anaesthesiol Scand 2004;48:1014-1018.
- Ezri T, Szmuk P, Warters RD, et al. Difficult airway management practice patterns among anesthesiologists practicing in the United States: Have we made any progress? J Clini Anesth 2003;15:418-422.
- Berkow LC, Greenberg RS, Kan KH, et al. Need for emergency surgical airway reduced by a comprehensive difficult airway program. Anesth Analg 2009;109:1860-1869.
- Mayo PH, Hegde A, Eisen LA, et al. A program to improve the quality of emergency endotracheal intubation. Intens Care Med 2011;26:50-56.
- Semler MW, Janz DR, Lentz RJ, et al. Randomized trial of apneic oxygenation during endotracheal intubation in the critically ill. Am J Respir Crit Care Med 2016;193 273-280.
- Frerk C, Mitchell VS, McNarry AF, et al. Difficult Airway Society guidelines for management of unanticipated difficult airways in adults. Br J Anaesth 2015;115:824-848.
- Janz DR, Semler MW, Lentz RJ, et al. Randomized trial of video laryngoscopy for endotracheal intubation in critically ill adults. Crit Care Med 2016 June 28 [Epub ahead of print].
- Silverberg MJ, Li N, Acquah SO, et al. Comparison of video laryngoscopy versus direct laryngoscopy during urgent endotracheal intubation: A randomized controlled trial. Crit Care Med 2015;43:636-641.
- Honarmand A, Safavi M, Yaraghi A, et al. Comparison of five methods in predicting difficult laryngoscopy: Neck circumference, neck circumference to thyromental distance ratio, the ratio of height to thyromental distance, upper lip bite test and Mallampati test. Adv Biomed Res 2015;4. Published online 2015 Jun 4. doi: 10.4103/2277-9175.158033.
- De Jong A, Molinari N, Terzi N, et al. Early identification of patients at risk for difficult intubation in the intensive care unit: Development and validation of the MACOCHA score in a multicenter cohort study. Am J Respir Crit Care Med 2013;187:
- Chmielewska M, Winters BD, Pandian V, et al. Integration of a difficult airway response team into the hospital emergency response system. Anesthesiology Clin 2015;33:369-379.
- Koenig SJ, Lakticova V, Narasimhan M, et al. Safety of propofol as an induction agent for urgent endotracheal intubation in the medical intensive care unit. J Intensive Care Med 2015;30:
- Levitan RM, Heitz JW, Sweeney M, et al. The complexities of tracheal intubation with direct laryngoscopy and alternative intubation devices. Ann Emerg Med 2011;57:240-247.
- Niforopoulou P, Pantazopoulos I, Demesthia T, et al. Video-laryngoscopes in the adult airway management: A topical review of the literature. Acta Anaesthesiol Scand 2010;54:1050-1061.
- Hernandez MR, Klock PA, Ovassapian A. Evolution of the extraglottic airway: A review of its history, applications, and practical tips for its success. Anesth Analg 2012;114:349-368.