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A Prospective Audit of Airway Code Activations and Adverse Events in Two Tertiary Hospitals

Introduction: Airway management outside the operating room can be challenging, with an increased risk of difficult intubation, failed intubation and complications. We aim to examine airway practices, incidence of difficult airway and complications associated with airway code (AC) activation. Methods: We conducted a prospective audit of AC activations and adverse events in two tertiary hospitals in Singapore. We included all adult patients outside the operating room who underwent emergency intubation by the AC team after AC activation. Adult patients who underwent emergency intubation without AC activation or before the arrival of the AC team were excluded. Data were collected and documented by the attending anaesthetists in a standardised survey form shortly after their responsibilities were completed. Results: The audit was conducted over a 20-month period from July 2016 to March 2018, during which a total of 224 airway activations occurred. Intubation was successful in 218 of 224 AC activations, giving a success rate of 97.3%. Overall, 48 patients (21.4%) suffered an adverse event. Thirteen patients (5.8%) had complications when intubation was carried out by the AC team compared with 35 (21.5%) by the non-AC team. Conclusion: Dedicated AC team offers better success rate for emergency tracheal intubation. Non-AC team attempted intubation in the majority of the cases before the arrival of the AC team. Increased intubation attempts are associated with increased incidence of adverse events. Equipment and patient factors also contributed to the adverse events. A multidisciplinary programme including the use of supraglottic devices may be helpful to improve the rate of success and minimise complications. Ann Acad Med Singap 2020;49:876-84


Introduction
Airway management outside of the operating room (OR), such as in the intensive care unit (ICU) or the emergency department (ED), poses unique challenges. 1,2 It is therefore not surprising that there is a higher incidence of failed intubation of approximately 1 in 50-100 in the ED and ICU compared with 1 in 2,000 in the elective OR setting. 2 There is also a higher risk of difficult intubation (9-10%), [3][4][5] and complications (21-39%) 3,6,7 outside the OR. 2,8 Moreover, litigation arising from airway claims are costly and forms the highest proportion of cases with poor clinical outcomes. 2 Previous studies in the UK 6,[9][10][11] and the US 4,5,8,12-14 have examined the indications for and complications associated with emergency intubations outside the OR, but such data are not available locally in Singapore. In Singapore, intubations in the ICU can be performed by intensivists or anaesthetists trained in critical care medicine. Airway training for non-anaesthetists is conducted throughout their intensive care training in the form of airway workshops. Basic airway equipment is available in the emergency cart. There is also a videolaryngoscope in every ICU.
An airway code (AC) activation is an emergency request by non-anaesthetists for the AC team to assist in airway management outside the OR. The AC team comprises an anaesthetic senior resident or associate consultant who has at least 36 months of anaesthetic experience, with or without support from an anaesthetic nurse or a respiratory therapist. The type of equipment that the AC team brings is at their discretion.
We conducted a prospective study on AC activations in 2 large tertiary hospitals in Singapore. The aims were to evaluate airway management after AC activation, in order to (1) report the indications and clinical context for AC activations; (2) report the incidence of difficult airway; (3) examine airway management practices; (4) report complications associated with airway management; and (5) identify areas for improvement.

Methods
This was a prospective study on emergency airway management outside the OR in Singapore General Hospital and Tan Tock Seng Hospital in Singapore for a 20-month period from July 2016 to March 2018. The study was approved by SingHealth Centralised Institutional Review Board and the National Health Group Domain Specific Review Board, respectively.

Inclusion and exclusion criteria
All adult patients outside the OR who underwent emergency intubation by the AC team after AC activation during the period of study were included in the study. Adult patients who underwent emergency intubation without AC activation or before the arrival of the AC team were excluded.  15 4. Details of drugs and equipment taken and used by the attending AC team. Additional airway equipment or assistance that would be considered potentially helpful to manage the AC but was not present was also noted. 5. Airway management by non-AC and AC team, as well as any complications encountered. Difficulty in face mask ventilation was graded according to Han's classification. 16 For tracheal intubation, laryngeal view grading was based on the Cormack-Lehane classification. 17 6. Adverse events related to airway management: dental trauma, oropharyngeal soft tissue bleeding or trauma, oesophageal intubation, aspiration of gastric contents, and airway obstruction. Data are presented as numbers and percentage of total AC activation cases.

Statistical analysis
Statistical analysis was performed with SPSS software version 25 (IBM Corp, Armonk, US). The continuous variables were analysed using t-test, and discrete variables were analysed using the chi-square test. A multivariate analysis using stepwise logistic regression was performed to look for significant factors, defined as those with P<0.05 in the univariate analysis. A composite variable of adverse events that included dental injury, oropharyngeal soft tissue trauma or bleeding, oesophageal intubation, aspiration of gastric contents and airway obstruction was used. Univariate analysis was used to analyse significant factors that increased the risk of adverse events encountered by both the AC and non-AC teams.

Results
During the study period, there were a total of 224 airway activations, during which patients required emergency out-of-OR tracheal intubations by the AC team. The percentages were calculated using a denominator of 224 patients (even if there were missing documented data) unless otherwise stated. Characteristics of airway code activation patients are summarised in Table 1.
Overall, 48 patients (21.4%) suffered an adverse event. Thirteen patients (5.8%) had complications when intubation was carried out by the AC team compared with 35 (21.5%) by the non-AC team. The most common adverse event encountered by the AC team was oesophageal intubation (n=4; 30.8% of AC team's adverse events), followed by dental trauma (n=3; 23.1%) and aspiration of gastric contents (n=3; 23.1%). The remaining adverse events included 2 cases of oropharyngeal trauma and 1 case of airway obstruction. For the non-AC team, the most common adverse event was oropharyngeal soft tissue bleeding or trauma (n=18; 51.4% of non-AC personnel's adverse events), followed by oesophageal intubation (n=7; 20.0%) and dental trauma (n=4; 11.4%) ( Table 3).
For AC providers, factors associated with increased risk of complications following tracheal intubation were interdental distance <3cm, prominent upper teeth and receding lower jaw. As for non-AC providers, reduced range of motion of the neck was found to be a statistically significant factor associated with increased risk of complications (Tables 4 and 5).

Discussion
Our prospective study reveals that the nature of our AC activations were similar to those of other studies. They arose mainly from the ICU (38-70%), 4,6,11 general ward (3-39%), 4,6,11 and ED (1-37%); 4,6,11 and mainly occurred during working hours (55-61%). 3,11 The most common causes for our AC activations were failed intubation by the non-AC team, respiratory distress and cardiovascular collapse. Other studies show that airway protection as an indication for emergency intubation varies, depending on the out-of-OR site: ICU (11-21%) 11,13 and ED (59-64%). 14 Respiratory failure as an indication for emergency tracheal intubation is high in ICU (61-65%). 13 The incidence of difficult intubation in patients considered to have normal airways and scheduled for elective surgery is 5.8%. 15 However, in the emergency setting outside the operating theatre, studies reveal the incidence of difficult intubation to be 6-12% in the emergency setting. [3][4][5][6]11 Our study showed a much higher incidence of almost 23%. Difficult airway related to outof-OR patients may be due to anatomical, physiological and situational causes. 18 Anatomical factors include standard difficult airway predictors; poor patient and operator positioning; blood, vomitus and secretions in the airway; facial and neck trauma; airway oedema; and cervical neck immobilisation. 13,18 Physiological factors include haemodynamic instability, hypoxaemia, acidosis, inadequate fasting and patient agitation. 13 Physiological causes identified in our study were American Society of Anesthesiologists status ≥3, hypotension and hypoxaemia, as revealed by their high incidence in the patients. Situational factors include unfamiliar sites and team members, team members not familiar with airway management, after-hours AC activations and lack of equipment. 18 The majority of airway interventions by the AC provider were direct tracheal intubation with or without videolaryngoscopy, and is similar to other studies (direct laryngoscope, 52-61%; 6 videolaryngoscope, 45%). 6 Videolaryngoscopy is increasingly being used as a first-line technique for tracheal intubation with its  many advantages over direct laryngoscopy: improved laryngeal view, decreased incidence of failed intubation, high rates of successful rescue after failure of direct laryngoscopy, less applied laryngoscopic force required, improved training of novice clinicians, improved operator ergonomics, enabling of real-time optimisation of cricoid force application and external laryngeal manipulation, and decreased airway trauma and voice hoarseness. 1,19 A systematic review found that the use of videolaryngoscopy showed no benefit when it is 'routinely used' for emergency intubation outside the OR, when compared with direct laryngoscopy. 7 However, it was associated with a greater first-pass intubation in the ICU (78.3% vs 64.3%; odds ratio 2.02), but not in the ED or in the wards, and among less experienced clinicians (81.4% vs 71.5%; odds ratio 1.95); and with a reduction in oesophageal intubations (1.5% vs 4.7%; odds ratio 0.32). It was also associated with a greater incidence of arterial hypotension (7.8% vs 5.5%; odds ratio 1.49). In critically ill patients, videolaryngoscopy should be considered for first-attempt intubation if urgent intubation is performed by less experienced operators 12 or if difficult laryngoscopy is predicted. 1 Prior to the arrival of the AC team, the non-AC team attempted twice in 19.2% of cases and thrice or more in 14.3% of cases. One study showed that even more than 1 attempt at intubation was a significant predictor of adverse events (odds ratio 7.5). 14 Difficult airway guidelines also recommend a limit on the maximum attempts at intubation: 3 attempts, but a 4th permissible by an experienced colleague. 1,20 Other sources recommend 3 attempts, 21 or 2 attempts but a third permissible by an experienced colleague 22 . In the context of out-of-OR cases, the 'experienced colleague' should be an AC provider.
Of note, none of the non-AC providers used a SAD to rescue failed intubation. The reason may be the lack of knowledge of its use as well as its limited availability in certain areas such as the angiography suite. However, after failed intubation in the OR, a SAD is the recommended plan B, 20 and provides successful rescue ventilation in 63%, 23 and 94% of cases. 24 Rescue techniques when used outside the OR (face-mask ventilation, SAD ventilation and cricothyroidotomy) have relatively high failure rates. 10 The success rate in our study was 97.3%. One study showed a high success rate (91%) on the first tracheal intubation attempt and this was attributable partly to the high level of experience of intubators. 11 This is important as lack of education and training are causal factors of major airway complications outside the OR. 10 The results of our survey highlighted that emergency airway code activations were often due to failure to secure airway by non-anaesthetists. In addition, there was a higher incidence of oropharyngeal trauma and bleeding caused during attempts prior to AC team arrival, which may have worsened the situation. This observation may suggest the need for more airway training courses for non-anaesthetists to better manage emergency scenarios and to recognise a potential difficult airway so as to involve the AC team early during resuscitation and securing of airway.
Airway management complications can lead to serious morbidity and mortality. 2,[8][9][10] More than 60% of ICU airway complications have shown to lead to death or brain damage compared with 14% in the OR. 10 The unique challenges of airway management outside the OR contribute to serious complications and stem from many causes. 1,2 Systemic factors include poor environment and ergonomics, as well as lack of guidelines, resources and training, and specialist staff. Human factors include poor clinical judgment, poor communication and teamwork; poor airway assessment; lack of, and unfamiliarity with, equipment and monitoring; and limited training in airway emergencies. Patient factors include obesity, low physiological functional reserve, difficult airways, suboptimal positioning of patients and aspiration risk.
In the Fourth National Audit Project, complications of airway management led to emergency surgical airway in 33% of cases in ICU and 67% in ED, with 25% and 0% failure rate, respectively. 10 Needle cricothyroidotomy, however, had a high failure rate (63%), but it was performed in patients who were in extremis. Owing to the challenges of airway management outside the OR and its associated morbidities, the concept of priming for 'front-of-neck access' was recently introduced. 1 This is the formalised transition from a 'cannot intubate, cannot oxygenate' scenario to performing front-of-neck access.
Fortunately, we did not encounter any 'cannot intubate, cannot oxygenate' scenarios in our 224 AC activations.
In 1 study, there were 4 independent predictors of the composite airway complication outcome: 3 or more intubation attempts (odds ratio 6.7), grade 3 or 4 direct laryngoscopy view (odds ratio 1.9), and patient location on the general care floor (odds ratio 1.9) or ED (odds ratio 4.7). 4 Not surprisingly, we found that factors associated with increased risk of complications are similar to those predicting a difficult airway, that is, interdental distance <3cm, prominent upper teeth and receding lower jaw, and limited range of motion of neck. We note that the use of bougie was associated with more complications due probably to a difficult airway encountered instead of the bougie causing direct injury.
In the Fourth National Audit Project report, equipment or resource-related causal and contributory factors in major airway complications occurred in 36% of cases and included non-availability, lack of training in their use, and failure to consider using the right equipment. 10 Another study showed that various equipment was not available for out-of-OR intubation: suction (2%), bougie (4%), alternative airways such as a SAD (12%) and capnography (32%). 3 In our study, portable capnography was initially unavailable but was later included as part of the emergency airway response kit. There is also increased training in the use of this equipment in areas outside of operating theatres, especially for paramedical staff, such as ward nurses, in the event of emergency airway events. The lack of, or failure to use, capnography is a major factor in airway mortality and morbidity outside the OR, contributing to 74% of cases of death or persistent neurological injury. 10 Continuous capnography is therefore recommended for use in all locations, in patients who are intubated or ventilated via SADs or similar devices. 2,10,26,27 However, despite the availability of portable capnography devices, capnography is not consistently used in airway management in the ICU (54-72%) 3,11 and the general wards (20%). 3 The ICU should have a difficult airway trolley identical in content and layout as that in the OR, 1,2,10 but only 50% of units have such a trolley. 28 Delays in obtaining equipment were reported in 30 cases (13.4%) in our study. We have now equipped our AC team with a difficult airway box that contains a videolaryngoscope, SAD, and airway adjuncts.
Our study reinforced that increased intubation attempts are associated with an increased incidence of adverse events. Hence, we should consider reducing the number of intubation attempts by novice intubators.
To help coordinate airway management between various personnel, the mnemonic 'PREPARE' may be helpful: P: pre-oxygenate/position; R: reset/resist; E: examine/explicit; P: plan A/B; A: adjust/attention; R: remain/review; E: exit/explore. 18 The details are described in Fig. 2 One institution developed the Difficult Airway Response Team (DART), that consists of a multidisciplinary difficult airway response team operating on a model with 3 core components: operations, safety and education. 5 During the first 5 years of the DART programme, there were no airway management-related deaths, sentinel events or malpractice claims. However, further studies are required to evaluate its effect on patient outcome and the cost effectiveness.

Limitations
There are several limitations to this observational study. First, airway management was not standardised across all AC providers. We were able to record the types of equipment used but not the order in which they were used. There were still missing data despite our best efforts at collection. Airway code categories for AC activation, such as respiratory distress and cardiovascular instability, were also not defined and were left to the individual interpretation by clinicians. Although the primary reason for AC activation in our study was because of failed intubation by a non-AC team, the underlying reason was not recorded. We recognise that this may not truly reflect the medical reason behind the need for intubation. Also, we note that there is potential for overestimating the incidence of difficult airway because adult patients who underwent emergency intubation without AC activation are excluded. As the forms were anonymous, there is a possibility of under-reporting of adverse events. Definition of adverse events was not standardised and was left to the interpretation of clinicians.

Conclusion
This study offers insight into patient, equipment and human factors that impact the outcome of emergency outof-theatre airway management in 2 of our local tertiary institutions. Future multicentre studies will be useful to further validate these findings and extrapolate the results to improve emergency airway outcomes.