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  368  www.anesthesia-analgesia.org   February 2013 ã  Volume 116 ã  Number 2 E  REVIEW ARTICLE Copyright © 2013 International Anesthesia Research Society DOI: 10.1213/ANE.0b013e31827ab572 I t is increasingly recognized that extubation of the difficult airway is a situation at risk of life-threatening complications, whereas criteria and guidelines to guide safe practices in airway management at extubation are still based on limited scientific evidence and of unproven effectiveness in improving outcomes. 1,2  Several authors suggest that the dissemination of the difficult airway algorithm by the American Society of Anesthesiologists (ASA) in 1993 and 2003 and the increased availability of advanced airway management tools and techniques may have contributed to a reduction in the number of severe outcomes related to tracheal intubation. 3  On the contrary, over the same period, the rate of severe airway-related adverse events occurring in the operating room (OR) or in the recovery area after tracheal extubation has not changed. 1,2,4,5  The recently published Report of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society (NAP4) identified serious airway complications occurring during anesthesia, in the intensive care unit (ICU), and in the emergency department in the United Kingdom over a 1-year period, and pointed out that one-third of the events occurred at extubation or in the recovery room. Poor airway management strategies, inadequate assessment of risk factors for airway difficulty, and overall failure to plan were frequent contributing factors to adverse events. 6,7 , a  These results confirm the importance of developing preplanned strategies for extubation of the difficult airway to improve patient safety and outcomes, as suggested by the ASA Task Force on Management of the Difficult Airway since 1993 8,9  and, more recently, by an updated analysis of the ASA Closed Claims database. 5  Substantial lack of adequate scientific evidence has prevented the creation of evidence-based tracheal extubation guidelines.In January 2012, the Difficult Airway Society (DAS) in the United Kingdom, acknowledging the absence of any large randomized controlled trial of extubation practices, released a set of guidelines for the management of tracheal extubation, mainly based on expert opinions. The goal of the society is to provide clinicians with pragmatic guidelines Extubation of the Difficult Airway and Extubation Failure Laura F. Cavallone, MD and Andrea Vannucci, MD, DEAA From the Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri.Accepted for publication October 01, 2012.Funding: None.The authors declare no conflicts of interest.Reprints will not be available from the authors.Address correspondence to Laura F. Cavallone, MD, Department: Anesthesiology, Washington University in St. Louis, Campus Box 8054, 660 South Euclid Ave, St. Louis, MO 63110. Address e-mail to cavallol@ wustl.edu. Respiratory complications after tracheal extubation are associated with significant morbidity and mortality, suggesting that process improvements in this clinical area are needed. The decreased rate of respiratory adverse events occurring during tracheal intubation since the implementation of guidelines for difficult airway management supports the value of education and guidelines in advancing clinical practice. Accurate use of terms in defining concepts and describing distinct clinical conditions is paramount to facilitating understanding and foster-ing education in the treatment of tracheal extubation-related complications. As an example, understanding the distinction between extubation failure and weaning failure allows one to appreciate the need for pre-extubation tests that focus on assessing airway patency in addition to evaluating the ability to breathe spontaneously. Tracheal reintubation after planned extuba-tion is a relatively rare event in the postoperative period of elective surgeries, with reported rates of reintubation in the operating room and postanesthesia care unit between 0.1% and 0.45%, but is a fairly common event in critically ill patients (0.4%–25%). Conditions such as obesity, obstructive sleep apnea, major head/neck and upper airway surgery, and obstetric and cervical spine procedures carry significantly increased risks of extubation failure and are frequently associated with difficult airway management. Extubation failure follows loss of upper airway patency. Edema, soft tissue collapse, and laryngospasm are among the most frequent mechanisms of upper airway obstruction. Planning for tracheal extubation is a critical compo-nent of a successful airway management strategy, particularly when dealing with situations at increased risk for extubation failure and in patients with difficult airways. Adequate planning requires identification of patients who have or may develop a difficult airway, recognition of situ-ations at increased risk of postextubation airway compromise, and understanding the causes and underlying mechanisms of extubation failure. An effective strategy to minimize postextu-bation airway complications should include preemptive optimization of patients’ conditions, careful timing of extubation, the presence of experienced personnel trained in advanced airway management, and the availability of the necessary equipment and appropriate postextubation monitoring. (Anesth Analg 2013;116:368–83) a Available at: http://www.rcoa.ac.uk/nap4. Accessed on April 26, 2012. CME  Extubation of the Difficult Airway February 2013 ã  Volume 116 ã  Number 2 www.anesthesia-analgesia.org 369 easily applicable in daily practice. 10  It will be interesting to see how these guidelines will be received and implemented  by clinicians, and whether they will have a measurable impact on patient outcome.While further studies are needed to support most recom-mendations concerning airway management 11  and evaluate the usefulness of the guidelines issued so far, 12  the aim of this narrative review is to identify meaningful information on airway complications after tracheal extubation, and to elucidate epidemiology, outcomes, mechanisms, predictors, and possible preventive strategies of postextubation failure.On the basis of these findings, a set of practical recom-mendations is also summarized and presented. These rec-ommendations are in agreement with the criteria for the formulation of a “strategy for extubation of the difficult airway” contained in the 2003 ASA Practice Guidelines for Management of the Difficult Airway. 9  Although some of our findings may also apply to the pediatric population, investi-gating issues related to extubation failure in that population is beyond the scope of this review. DEFINITIONS To avoid confusion and ambiguity, it is important to pro-vide the reader with a few commonly used definitions. Difficult Airway In the 2003 ASA Practice Guidelines for Management of the Difficult Airway, difficult airway is defined as, “the clinical situation in which a conventionally trained anesthesiolo-gist experiences difficulty with face mask ventilation of the upper airway, difficulty with tracheal intubation, or both.” 9 Extubation Failure Extubation failure has been defined as “the inability to toler-ate removal of the translaryngeal tube,” 13  and it is generally treated with tracheal reintubation. Su et al. 14  suggest that investigating extubation failure requires “to focus on the removal of the artificial airway, rather than on the removal of the mechanical support.” Mechanisms of “extubation failure” include all causes of airway obstruction, such as laryngospasm, upper airway edema, bleeding either lead-ing to hematoma compressing the airway externally or clots internally obstructing the airway, accumulation of respira-tory secretions, tracheal collapse due to tracheomalacia, and upper airway soft tissue collapse secondary to the effects of anesthetics, opioids, and muscle relaxants. These mech-anisms leading to extubation failure are also frequently described as “extubation-related airway complications” 6,7,15  or “airway-related adverse events at extubation.” 5–7 Weaning Failure “Weaning failure is the inability to tolerate spontaneous  breathing without ventilatory support,” 13  and its treatment includes tracheal reintubation and invasive ventilation or, in selected patients, noninvasive ventilation. 16,17  Assessing the adequacy of weaning variables and predictors of air-way patency, as well as confirming the integrity of airway reflexes, are important preparatory steps for a successful extubation. This concept is particularly relevant in the ICU setting, where patients may successfully pass a weaning trial but fail extubation due to airway obstruction. 18,19  In fact, commonly used weaning trials do not reliably assess “airway patency” or “airway competence,” (the latter being defined as the ability to generate a strong cough and expec-torate endotracheal secretions 18 ) and weaning variables do not predict extubation failure. 20 “At-Risk” Extubation “At-risk” extubation is a situation in which the ability of a patient to maintain airway patency and/or oxygenation after tracheal extubation is uncertain. 10  This definition was recently proposed and follows a risk stratification process  based on airway-related factors and general clinical condi-tions. Potentially difficult reintubation and/or general risk factors such as “full stomach, unstable cardiovascular phys-iology, acid-base derangement, or temperature control” characterize this condition. 10 Difficult Extubation A “difficult extubation” in the sense of a “difficult decan-nulation of the airway” is a rare situation that depends on mechanical factors related to patient, surgery, or anesthe-sia. For example, patient-related conditions include unrec-ognized subglottic stenosis or severe edema physically preventing removal of the endotracheal tube (ETT); 21  a sur-gery-related factor might be an erroneously placed surgical stitch anchoring the ETT to the tracheal wall. Incomplete deflation of the ETT cuff, either because of ETT cuff mal-function or negligence, may be considered an anesthesia-related cause. 15 EPIDEMIOLOGY AND OUTCOMES OF EXTUBATION FAILURE Extubation and weaning failure are generally observed within 72 hours of extubation. 13,18,22–26  Although some authors consider any intubation within this postoperative time frame as “early,” 27  for the purposes of this review, the term “early reintubation” will apply to the immediate postextubation period (within minutes and up to 6 hours after tracheal extubation), whereas the term “late reintubation” will indicate events occurring between 6 and 72 hours after extubation.Both in the ICU and in postoperative settings, rein-tubations after extubation failure occur most frequently  between 0 and 2 hours postextubation, and seldom after 24 hours. 18,25,28–32 This information is relevant to clinicians in deciding how long to monitor patients at risk of extubation failure, 13  and, in patients with difficult airway, how long to keep airway exchange catheters (AECs) in place as tools for guiding tra-cheal reintubation, if required. 25 Extubation failure rates vary depending on the popula-tion observed. We will review clinical situations and patient conditions most frequently associated with extubation failure. Emergence and Recovery from Anesthesia Early reintubation is a relatively rare event in the post-operative period of elective surgeries and after planned  E   REVIEW ARTICLE 370  www.anesthesia-analgesia.org ANESTHESIA & ANALGESIA extubation, with reported rates of reintubation in the OR and postanesthesia care unit (PACU) between 0.1% and 0.45%. Reasons for early reintubation include respiratory insufficiency, airway obstruction, bronchospasm, prolonged neuromuscular blockade, and side effects of opioids. 29,31,33 “Airway obstruction” (all causes) is the most common cause of airway-related events and need for reintubation in the early postoperative setting. 3,6,31,34,35  A frequent cause of airway obstruction leading to early extubation failure  both in anesthesia and ICU patients is laryngeal edema, 36,37  generally observed within 1 hour of extubation and rarely observed after 24 hours. 25,28,29,31,32  Fewer data are available on the causes of “late reintubation” in the postoperative set-ting; patient comorbidities, type of surgery, and postopera-tive management may all be contributing factors. 27 In a retrospective review of >13,000 consecutive PACU admissions published in 1990, Mathew et al. 29  observed 26 emergent reintubation events (0.19% rate). In this series, reintubations occurred in a heterogeneous group of patients, more frequently after head and neck surgery, and the main recognized contributing factor was inappropriate medical management. Seventy-seven percent of the reviewed events were classified as “preventable,” as the 2 most common causes of emergent reintubation were found to be persistent sedative and muscle relaxant effect, and inappropriate fluid management. Interestingly, the same investigators reported that “all 26 patients were eventually discharged from the hospital without sequelae of these events,” 29  implying a moderately severe impact of extubation failure on patients clinical course.The 1985 to 1999 ASA Closed Claims database analysis offers a very different perspective on the severity of extu- bation-related complications. Of the 26 claims from events after tracheal extubation, 21 cases (81%) resulted in either death or brain damage. Notably, the majority of the patients involved were obese (15 of 26). Over the same period, 104 claims related to events at induction of anesthesia were reported, of which 50 (48%) resulted in death or brain dam-age. Interestingly, although the authors of the analysis were able to detect a significant decrease in severe outcomes after events at anesthesia induction over the years (from 62% in 1985–1992 to 35% in 1993–1999), the same did not hold true for adverse events after extubation. 1  We recently sur-veyed the ASA Closed Claims Project database  b  and were informed that among the 47 claims for difficult intubation on anesthesia induction since 2000, 20 (43%) resulted in death or permanent brain damage. This suggests that the trend toward reduced death/brain damage reported by Peterson et al. 1  appears to be continuing. Among claims for failed extubation reported since 2000, death and permanent brain damage occurred in 15 of 16 claims (94%), and there were 8 claims with difficult airway management that occurred postextubation in the recovery period, all (100%) result-ing in death/brain damage. In evaluating data from the Closed Claim Project, it is important to remember that only litigated malpractice claims are reported in the database; therefore, failed extubations that resolved uneventfully are not captured, and the rate of events in the population of tra-cheally intubated patients undergoing general anesthesia cannot be calculated.The NAP4 study was designed to track only major airway complications as defined by the following outcomes: death,  brain damage, need for surgical airway, and unplanned ICU admission, and 38 events that occurred at emergence or during recovery from anesthesia were reported. This cor-responds to a rate of severe complications of about 0.001%  based on an estimated denominator of 2,872,600 general anesthetics performed yearly in the United Kingdom (1 major airway adverse event postextubation in 75,600 anes-thetics). 6  In this group of 38 patients whose most common comorbidities were obesity (46%), chronic obstructive pul-monary disease (34 %), and obstructive sleep apnea (OSA; 13%), the mortality rate was 5% (2 deaths), and the cumula-tive rate of death and severe morbidity (including resusci-tated cardiac arrest and brain damage) was 13%.The percentages of severe outcomes from the ASA Closed Claims database and the NAP4 are not comparable  because of the different nature of the data (closed claim ver-sus voluntary report), but in both studies, reviewers consid-ered poor outcomes frequently to be secondary to “less than appropriate care” and/or judgment (often in the presence of head and neck pathologies or postsurgical changes), to incomplete handoff communications, and to lack of ade-quate postoperative monitoring. 6,38 Overall, these data suggest that extubation failure in the early postoperative setting is rare, especially after elective surgery, but it is associated with extremely severe outcomes and litigation, even more frequently than airway-related complications occurring in other phases of anesthesia. 1  Airway obstruction is the main cause of extubation failure and need for tracheal reintubation after anesthesia. These serious adverse events are due to a combination of factors that are patient-related (obesity, OSA, chronic obstructive pulmonary disease), surgery-related (head and neck sur-gery and upper airway manipulation) and, probably more importantly, provider-related (inappropriate or incomplete planning, management, and judgment). 1,6,29,38 Tracheal Extubation in the ICU Reintubation is a fairly common event in critically ill patients (0.4%–25%) after extubation failure and weaning failure, 13,25,39  2 frequently intertwined complications in the ICU.In ICU patients, the impact of extubation or weaning fail-ure and need for reintubation on the overall outcome is often measured in terms of increased ICU and hospital length of stay and mortality. The direct association between the need for reintubation and prolonged ICU and hospital stay and mortality has been demonstrated in a variety of critically ill patients. 13,39,40  Of note, a few investigators have found that ICU patients requiring reintubation for respiratory failure have a higher mortality (30%–52.9%) than patients whose tracheas were reintubated because of airway obstruction (7%–17.4%). 24,32,41,42  This suggests that “weaning failure” may carry a higher mortality than “extubation failure.”Certainly, postextubation respiratory failure in critically ill patients may be accompanied by failure of other organs b  Personal communication from Karen Posner PhD—Laura Cheney Profes-sor in Anesthesia Patient Safety, Department of Anesthesiology, University of Washington on November 10, 2011.  Extubation of the Difficult Airway February 2013 ã  Volume 116 ã  Number 2 www.anesthesia-analgesia.org 371 and systems that independently affect mortality. 40  On the contrary, upper airway obstruction can occur in less com-promised patients and, by itself, does not appear to increase the likelihood of adverse outcomes. 41  Another hypothesis to account for this difference in outcome is that patients who fail trials of extubation because of airway obstruction are reintubated earlier than those who fail because of intrinsic respiratory complications, 41  and time to reintubation after failure has been found to be an independent predictor of hospital mortality. 13,24 Interestingly, in the NAP4 study only 1 of the 36 air-way management complications reported in ICU patients occurred at the time of tracheal extubation. It is not possible to calculate the incidence of these events because a reliable estimate of the number of patients managed in ICUs in the same 1-year observation period is missing. This is a limi-tation of the ICU portion of the study, which is otherwise an extremely interesting and useful source of information on major complications of airway management and clini-cal practices in anesthesia and intensive care at a national level. 43–45  However, other investigations show that tra-cheal reintubation, either after failed extubation or failed weaning, is a much more common occurrence in the ICU than in the postoperative setting. 25  Moreover, unplanned extubation occurs in 5% to 15% of ICU intubated patients and is associated with increased ICU morbidity and mortality. 40 CONDITIONS AND PROCEDURES AT INCREASED RISK FOR EXTUBATION FAILURE AND DIFFICULT AIRWAY MANAGEMENT Conditions such as obesity, OSA, 6,46–48  major head/neck and upper airway surgery, 6,28,35,49,50  obstetric, 51  and cervical spine procedures 52–56  carry significantly increased risks of extuba-tion failure and are frequently associated with difficult air-way management. Obesity and OSA The Centers for Disease Control and Prevention define obese individuals as those with a body mass index >30 kg/m 2 . 57  In the United States, the “heaviest” Western Country, the prevalence of obesity was 34% in 2008. 58  OSA is a syndrome characterized by periodic, partial, or complete obstruction of the upper airway during sleep. 59  Up to 71% of morbidly obese patients are affected by OSA. 60  Expert recommenda-tions and practice guidelines for the perioperative manage-ment of the obese and OSA patients largely overlap. 46–48,59 Obese patients have a higher incidence of difficult mask ventilation, 61–63  increased risk of pulmonary aspiration, air-way obstruction, and rapid oxygen desaturation after anes-thesia induction. 48  Difficult intubation has been reported in 7.5% of morbidly obese patients. 64  In reports investigat-ing major airway complications, the prevalence in obese patients is often higher than in the general population. Sixty-five of the 156 (42%) perioperative airway events in the 2005 ASA Closed Claim data analysis (data from 1985 to 1999) 1  and 77 of 184 (42%) complications in the NAP4 report 6  involved obese patients. In the time periods corresponding to the ASA Closed Claim and NAP4 data collections, preva-lence of obesity in the United States ranged between 10% and 25% c  (from 1985 to 1999); and in England, the preva-lence of obesity was 22% for men and 24% for women (2009 data). d  According to recent studies, this relatively high prevalence does not necessarily result in increased hospital stay and higher mortality, 65–67  especially for the subgroup of moderately obese patients. 68  However, these statistics do suggest that obese patients present a higher risk of airway management-related complications compared with the gen-eral population. Important postoperative concerns in the management of both obese and OSA patients include: (1) increased susceptibility to the respiratory-depressant effects of opioids and anesthetics; (2) increased risk of hypoxia that may require the use of continuous positive airway pres-sure treatment; (3) attention to patient positioning, which should be “nonsupine”; and (4) appropriate monitoring for early detection of respiratory and cardiovascular impair-ment (such as continuous pulse oximetry, capnography, and telemetry). 46–48,59 Of note, in OSA patients undergoing upper airway sur-gery for the treatment of OSA, the incidence of postopera-tive airway complications, including obstruction leading to severe oxygen desaturation, may be as high as 5%. 46,69 Head and Neck Pathology, Maxillofacial and Major Neck and Upper Airway Surgery In the presence of head and neck pathology and after max-illofacial and major neck surgery, rates of tracheal reintu- bation between 0.7% and 11.1% have been reported. 29,35  This also applies to endoscopic upper airway surgery, after which 4.2% of the patients whose tracheas were extubated in the OR needed to be reintubated in the PACU. 28 In the NAP4 report, 72 of the 184 adverse airway events (39.1%) involved patients with acute or chronic head and neck pathologies. Of these 72, 55 events were anesthesia-related (41.3% of the 133 anesthesia-related events), and the rest occurred in the ICU and emergency department. Of the 55 anesthesia-related events, 13 (23.6%) occurred at the time of tracheal extubation or during the recovery period. These adverse events in patients with head and neck patholo-gies accounted for 34.2% of all events during emergence or recovery. 6 Patients with active head and neck pathology, or who have undergone surgical or radiation treatment for head and neck cancer, are also at an increased risk of adverse airway events when presenting for other types of surgeries. In a 4-year observational study on prediction of impossible mask ventilation and outcomes, Kheterpal et al. 63  examined more than 50,000 attempts at mask ventilation over more than 94,000 anesthetics and found that neck radiation changes were the most significant clinical predictor of impossible mask ventilation. Besides critical difficulties with mask ventilation, radiation therapy induces extreme neck rigidity and modification of normal airway anatomy that may cause significant difficulty with tracheal intubation and makes it extremely challenging to perform an emergency c Available at: http://www.cdc.gov/obesity/data/trends.html. Accessed on November 27, 2011. d  NHS, the Information Centre: Statistics on Obesity, Physical Activity and Diet: England, 2011. Available at:http://www.ic.nhs.uk/statistics-and-data-collections/health-and-lifestyles/obesity. Accessed on November 27, 2011.
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