Introduction

Over the past 12 years, numerous articles addressing the management of the difficult pediatric airway have been published, marking a substantial increase compared to previous years. This surge can be attributed to several factors:

  1. (1)

    International, multicenter data collections and subsequent analysis.

  2. (2)

    Conducting prospective studies.

  3. (3)

    Advancements in pediatric medical devices for airway management.

  4. (4)

    Publication of new and updated guidelines specifically focusing on the pediatric airway.

These developments have significantly influenced the approach to managing both difficult and normal pediatric airways. [1].

It is crucial to recognize that the pediatric airway presents unique challenges. Even seemingly normal pediatric airways can pose difficulties, especially in newborns and infants, a vulnerable group at increased risk for complications.

Anatomical features such as a large occiput, a higher larynx position, and a relatively larger tongue not only make proper alignment during direct laryngoscopy (DL) challenging but also increase the risk of airway obstruction. Additionally, characteristics like an elongated epiglottis and a narrow trachea further compound the challenge. Physiological differences in the pediatric cardiovascular and respiratory systems can lead to rapid oxygen desaturation and bradycardia, potentially leading to cardiac arrest.

Acknowledging the lack of substantial data on the management of the pediatric difficult airways, a group of dedicated pediatric anesthesiologists established a task force within the Society of Pediatric Anesthesia in 2011 to address this knowledge gap. This task force, aiming to collect data on how pediatric difficult airways are managed by different anesthesiologists, defined specific criteria for case inclusion in the Pediatric Difficult Intubation Registry (PeDI-R). The ultimate goal of PeDIR is to enhance the management of pediatric difficult airways [2]. Numerous publications and recommendations have emerged from the analysis of its prospective data collections [1,2,3,4,5,6,7,8,9,10].

While the PeDIR provides valuable insights into the management of pediatric difficult airways, whether expected or unexpected in children under the age of 18, it does not report the incidence of such cases.

However, large-scale prospective observational studies in Europe have shed light on this aspect.

The APRICOT (Anesthesia Practice In Children Observational Trial) study,[11] conducted across 261 pediatric hospitals in 33 European countries, reported a critical respiratory event incidence of 3.1% in children aged 0–15 years, with 0.88% requiring more than three intubation attempts. Similarly, the NECTARINE (NEonate and Children audiT of Anesthesia pRactice IN Europe) study [12], spanning 165 pediatric centers in 31 European countries, identified a 5.8% incidence of difficult intubations defined as more than two attempts in infants (birth to 60 weeks post conception) with two-thirds being unexpected [13].

In 2022, the revised ASA guidelines for the management of the difficult airway included for the first time a dedicated section addressing the pediatric airway [14].

The Society of Anesthesiology and Intensive care and the British Journal of Anaesthesia recently published guidelines for the airway management in neonates and infants [15].

Key insights from these studies underscore the following principles:

  1. 1.

    Higher risk associated with younger children.

  2. 2.

    Increased complication rates with multiple intubation attempts.

  3. 3.

    Repeating the same technique increases multiple attempts, hence increased complications.

  4. 4.

    Importance of creating optimal conditions through sedation, anesthesia, and muscle relaxation.

  5. 5.

    Value of passive oxygenation.

Airway Examination

Airway examination and risk assessment are integral components and the first step to prevent difficulties with the pediatric airway [14, 16]. Pediatric patients, compared to adults, are often not compliant with an airway exam.

The presence of congenital malformations such as Pierre Robin, Apert, Crouzon, Goldenhar, dysmorphic facial features, respiratory conditions, tumors or trauma of neck and head, achondroplasia, mucopolysaccharidoses and other factors contribute to the predictability of the difficult pediatric airway. Lesser dysmorphic characteristics, such as minor retrognathia, can be identified by examining the child’s face from a lateral view.

A history of bronchopulmonary dysplasia in former premature infants, a recent upper airway infection, obstructive sleep apnea, a full stomach, and respiratory distress in the form of stridor or dyspnea can also make pediatric airway management challenging. Symptoms of upper respiratory infections within two weeks prior to airway management significantly increase the risk of serious respiratory events like laryngospasm and bronchospasm [17].

There are expected difficult airway scenarios that one can prepare for and then there are unexpected difficult airway situations [18]. Airway obstruction can rapidly lead to a critical situation necessitating a well-trained structured approach to avoid airway-related morbidity and mortality [14, 16]. The PeDI-R documents a higher complication rate with unexpected difficult airway as compared to expected difficult airway [2].

Preparation

Choosing the most appropriate location, such as a well-equipped pediatric operating room rather than an outside location can be essential. The next step is to discuss the airway management and its backup plan with all involved members to minimize human factor barriers [19]. All available airway equipment needs to be checked and in working conditions, with appropriate size and fitting tested. Appropriate medications should be prepared and ready for use. If available an experienced colleague’s help should be solicitated [20]. Schnittker identified three enablers and five barriers in an interview study indicating that location, storage and preparation of equipment, planning, teamwork and communication influence the success of airway management [19]. (Table 1).

Table 1 Stepwise Approach in Preparation of an Anticipated Pediatric Difficult Airway
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Mask Ventilation

Mask ventilation is considered the most fundamental skill in airway management [21]. It starts with choosing the right sized mask and relies on the training and expertise of the provider [22]. The skills of mask ventilation are as important as intubation, if not more so. Inadequate mask ventilation can easily lead to hypoxemia. Upper airway obstruction is more frequent in children. Only a few studies have addressed difficult mask ventilation in children [22].

Valois-Gomez, in a prospective, observational study of 484 children (0-8 years) presenting for elective surgery, reports the incidence of unexpected difficult mask ventilation as 6.6%. Predictably difficult airways were excluded. Age was the only factor independently associated with difficult mask ventilation. Less significant factors in this study included obstructive sleep apnea, obesity, and ENT surgery [22]. Nevertheless, timely intervention to recognize a difficult mask ventilation depends on the level of expertise [23]. Morbidity and mortality in pediatric airway management are associated with the failure to recognize functional airway problems related to insufficient depth of anesthesia [18, 24]. Concerning children with a difficult intubation from the PeDI registry, the incidence of difficult mask ventilation was 9% and these children had close to a three-fold increase in complications as compared to children with easy mask ventilation. The use of muscle relaxants often improved mask ventilation. Factors associated with difficult mask ventilation included infancy, underweight or overweight, glossoptosis, and limited mouth opening [3, 25]. Similar results were reported from the National Emergency Registry for Children [26].

Intubation

The incidence of difficult intubation in children is reported from 0.88% to 5.8% depending on the pediatric population included and the definition used [11, 12, 27,28,29]. In many studies infants and neonates have the highest incidence of difficult intubation. So far, the pediatric difficult intubation registry (PeDI-R) has collected over 8000 difficult intubations in children under 18 years. The first analysis of 1018 difficult intubations from the PeDI-R, published in 2016, reported the rates of intubation attempts, the incidence of complications depending on the number of attempts, and the most successful devices [2]. Direct laryngoscopy (DL) was used in 46% for the first attempt and was successful in only 3%. The first attempt success rate using flexible bronchoscopy or video laryngoscopy (VL) was 54% and 55%, respectively.

The study confirmed the higher risk of airway management in small children less than 10 kg. Complications increased with multiple intubation attempts. In this cohort, 20% of patients had at least one complication, including laryngospasm, hypoxemia, and airway trauma. Out of these 20%, 3% had severe complication, such as aspiration, emergent surgical airway, and unrecognized esophageal intubation with 2% (15 children) experiencing arrest. In this cohort the incidence of cardiac arrest was 1/68. In 11/15 cardiac arrests the intubation was in the operating room and was non-emergent. Hypoxemia was the most common non-severe complication with an incidence of 9%.

The number of attempts increased when persisting with the same device, while early transition to a video laryngoscopy (VL) was associated with fewer complications. 21% of first attempts were performed by an attending physician such as an intensivist, while at the end over 44% of successful intubations were performed by an attending anesthesiologist. The study suggests limiting airway manipulations by trainees to avoid unnecessary multiple attempts and complications.

The conclusions from this first analysis were:

  1. 1.

    The smaller the child, the riskier the airway management.

  2. 2.

    Avoid multiple attempts by having the airway expert step in.

  3. 3.

    Do not attempt multiple times with the same device.

  4. 4.

    Use passive oxygenation during intubation attempts.

The European studies APRICOT and NECTARINE came to similar conclusions [11, 13].

The poor performance of direct laryngoscopy in the PeDI cohort triggered a more detailed analysis. In 2017, Park compared the initial success rate of DL and GlideScope VL in 1295 encounters, showing an initial success rate of 51% with the GlideScope, compared to only 4% with DL [5]. Small children weighing less than 10 kg had a lower success rate with the GlideScope compared to older children. Due to a greater number of attempts with DL the number of complications increased.

A 2017 Cochrane review of VL in children, excluding neonates, showed a prolonged intubation time and a higher failure rate when compared to DL [29]. This review compared any type of indirect laryngoscopy with direct laryngoscopy and did not distinguish between different VL blades. Multiple studies have compared different video laryngoscopes in hopes of finding the best device [30, 31]. To further clarify if the design of the video laryngoscope affect success rates, Peyton reported 1313 encounters of VL from the PeDI registry during the period of March 2017 to January 2020. Video laryngoscopes were divided into VL with standard blades (Miller and Macintosh) and non-standard blades, curved or angulated [7]. There was no significant difference in the success rate for the first attempt for patients weighing over 5 kg, but VL with standard blades had a significantly higher success rate in children weighing less than 5 kg (51% versus 26%). There were more difficulties inserting the endotracheal tube despite having an adequate view of the vocal cords with non-standard blades compared to standard blades. The data and clinical experience confirm that the use of non-standard blades has a greater learning curve and requires more expertise to overcome the technical difficulty of advancing the ETT into the trachea. According to this study, the use of a video laryngoscope with a standard blade is recommended as a good first choice for intubating the difficult airway, especially in children weighing less than 5 kg [32].

Rescue Devices

VL is not the sole solution for difficult airway problems. In the adult realm, the flexible bronchoscope is considered the gold standard for difficult intubation. The use of a flexible bronchoscope in combination with a video laryngoscope is termed a hybrid technique, and this technique has beenshown to increase the success rate of intubating the difficult airway in children. This technique necessitates two skilled physicians.

The fiberoptic bronchoscope with a loaded ETT serves as a stylet that can be controlled and observed via the videoscopic view. Both providers can visualize the view through the fiberoptic bronchoscope and the videoscope on a split screen, improving the position of each device as needed. This technique overcomes the limitation of each device. It is helpful when secretions or blood soil the tip of the fiberscope, as it can still be guided with the help of the videoscopic view. Stein reported the efficacy of the hybrid technique in children with a difficult airway from the PeDI registry [9]. The success rate of the first attempt with the hybrid technique was 70% compared to 63% with the flexible bronchoscope alone. The complications rates were similar as was the ultimate success of intubation. The hybrid technique was more often used in smaller children and as a rescue technique, it is a good option when either the videoscopy alone or the flexible bronchoscopy alone fails [33]. In case of a failed hybrid technique intubation via a supraglottic airway device or with a rigid bronchoscope has been shown to be successful.

Another successful technique is intubation through a supraglottic airway device using a flexible bronchoscope. The technique involves several steps that need to be prepared before the intubation is initiated. One needs to ensure the ETT will easily slide through the SGA, remove the connecter of the SGA, push the ETT inside the SGA and inflate the cuff so that the combination becomes stable and sealed. A swivel adapter connected to the ETT allows continuous oxygenation and administration of anesthesia gas while the flexible bronchoscope is advanced into the trachea after the SGA/ETT is placed in the child’s oropharynx. Once the ETT is in the trachea, the SGA can carefully be removed by using a second ETT or a laryngeal forceps to hold the ETT in place [33].

Oxygenation

The goal of continuous supplemental oxygen administration during intubation is to prolong apnea time and delay oxygen desaturation [34,35,36]. Hypoxemia is a frequent complication during pediatric airway management, and in 1.6% of children, in the first 1018 cases of the PeDI registry, cardiac arrest occurred and was preceded by hypoxemia in all cases [2]. Apneic oxygenation was first shown to decrease hypoxemia in adults before being studied in children. An observational study looked at the intervention of apneic oxygenation in a pediatric emergency department. Children in the pre-intervention group had a higher incidence of hypoxemia [37]. Although other studies have demonstrated conflicting results apneic oxygenation has been increasingly adopted during pediatric intubation [38]. Continuous apneic oxygenation allows more time for the first attempt at intubation and may decrease the number of repeated intubations and consequent complications. A recently published meta-analysis of 15 studies including 9802 children found that apneic oxygenation increased the success rate of the first attempt at intubation, showed higher oxygen saturation during intubation, decreased the incidence of hypoxemia, and reduced the overall number of attempts [34].

Several continuous oxygenation techniques have been described: nasal cannula, modified nasal trumpet, modified oral RAE tube, nasal CPAP, and heated humidified high flow nasal cannula. There is no need to disconnect any oxygenation device if already in use [34, 38]. (Fig. 1) The recent ASA guidelines for the management of the difficult airway [14], and the guidelines for airway management in neonates and infants [15] emphasize the use of continuous apneic oxygenation for all patients with difficult airways. A difficult airway bundle including oxygenation techniques was distributed by the PeDI collaborators. The positive impact of the bundle has been described in a recent study about the change in outcomes over time within the PeDI registry [1].

Fig. 1
figure 1

An illustration showing several options of continuous apneic oxygenation tools routinely used by the authors. (1) Nasal cannula (2) Appropriately sized nasal airway with ETT connector (3) Supraglottic Airway Device (SGA) with connector removed (4) SGA Connector (5) ETT with cuff inflated to provide stabilization within the SGA (6) Swivel to allow continuous oxygenation via circuit (7) Fiberoptic bronchoscope (8) Circuit

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Sedation and Relaxation

Until recently, teaching about difficult airway management strongly recommended on keeping the patient breathing spontaneously if possible. Awake intubation with minimal sedation is the standard of care in the adult population. For pediatric patients, this dictum has lately been called into question. A retrospective analysis of muscle relaxant drug use and ventilation technique on complications during difficult airway management in children compared spontaneous ventilation with controlled ventilation with and without muscle relaxants. The conclusion was that spontaneous ventilation is associated with more complications, like hypoxemia and laryngospasm, than either controlled ventilation technique [6].

Complications may increase with insufficient depth of anesthesia. A follow-up cohort study using the PeDI registry compared sedation versus general anesthesia for tracheal intubation [8]. Between 2017 and 2020, there were 1839 encounters included in the study. Only 75 children received sedation. After propensity score matching, the rate of first attempt at intubation was similar, but in 27.6% of cases sedation needed to be converted to general anesthesia for successful intubation. Airway reactivity, inability to follow commands, insufficient topicalization, and other factors may be the reasons for conversion to general anesthesia in sedated children. Close to 50% of patients in the general anesthesia group received muscle relaxants. Complications were low and similar in both groups. There were 6 intubation failures in the general anesthesia group, rescued with either a supraglottic airway or emergence from anesthesia and cancellation. There was no front-of-neck access (FONA) needed. Several pathologies need to be mentioned where maintaining spontaneous ventilation is advised, these include but are not limited to head and neck pathologies, certain forms of mucopolysaccharidosis, papillomatosis, and epiglottitis.

Optimizing intubation conditions by choosing adequate sedation, general anesthesia and muscle relaxation will decrease multiple attempts. The choice of sedation or general anesthesia, with or without the use of muscle relaxation, should be selected by the physician depending on provider skills and patient evaluation.

Cannot Ventilate—Intubate / Cannot Oxygenate (cv-i/co)

The incidence of can’t ventilate/intubate and can’t oxygenate CV-I/CO commonly called CICO is a life-threatening emergency and very rare in children [25]. The NAP4 report, including pediatric patients, showed that the decision of FONA was often delayed due to fixation errors and reported a high failure rate of 63% [39]. In small children, the thyroid cartilage is difficult to palpate, and even though the use of ultrasound can help to identify the cricothyroid membrane, the acute angle of the short distance from mandible to cricothyroid membrane will make it difficult to avoid injuring the posterior wall of the trachea. There is no data to determine the best technique for FONA in children. The Melker kit was successfully used in a rabbit model, and could be successful in small children. Independent of the technique used, cannula cricothyrotomy, Seldinger technique, or scalpel cricothyrotomy are all lifesaving but difficult to perform with a high complication rate. The challenge of a cannula access is safe jet oxygenation, and even with the ENK oxygen flow modulator (no longer available via Cook Medical, Bloomington, Indiana), ventilating through a small-bore cannula can easily cause barotrauma when the glottis is closed, as it is in most CICO situations [40].

The only device allowing for expiration through a small-bore cannula is the ventrain device (Ventinova Medical, Eindhoven, the Netherlands, no longer available in the USA) which generates positive pressure during inspiration and active suction during expiration [41,42,43]. It is important that each institution has a difficult airway escalation plan, including how to contact the most qualified physician for the FONA. Depending on the institution, the last resort may be access to ECMO.

Ultrasound

Ultrasound has found its place in pediatric airway management and is helpful in various ways.

The trachea can be easily recognized, and its diameter measured [44]. The deviation of the trachea in case of an abscess or a tumor can be appreciated. The cricoidthyroid membrane can be identified and marked for a possible FONA [45]. An esophageal intubation can be seen on the transverse view of the neck and is a helpful image if the end tidal CO2 is unreliable. The esophagus, normally a collapsed structure, will be stented by an ETT and will look similar to the trachea. The one-sided missing lung-sliding sign may indicate a main stem intubation and should trigger a repositioning of the ETT. These represent a few, easy-to-learn applications of ultrasound use in airway management [46].

Extubation

Traditional airway teaching has focused on intubation, but the APRICOT study showed that extubation is associated with significant risk of respiratory complications [11].The same physiological and anatomical characteristics of the small child that make mask ventilation and intubation challenging, like increased oxygen consumption, decreased functional residual capacity, upper airway obstruction, large occiput and more, are responsible for increased serious adverse events during or after extubation. Laryngospasm and bronchospasm are not rare events in children and are more frequent in the hands of an inexperienced physician [23]. The revised ASA guidelines [14], and the guidelines for neonates and infants [15], recommend careful planning of the extubation, a logical extension of the intubation strategy. Extubation is poorly studied in pediatric patients, and the incidence of the need for reintubation is unknown; there is also no clear definition of failed extubation. Ing reports a low incidence of reintubation (0.096%) in children in a cohort of 28,208 anesthetics, 30% of reintubations were due to accidental extubation and 7% needed chest compression [47]. A higher incidence of reintubation (0.25%) was found by Murat [48]. One needs to keep in mind that extubation is an elective procedure, and patient readiness, reversal of muscle relaxants, sufficient respiratory drive, timing, location, and available help for reintubation should all be considered when planning for extubation [49]. Jagannathan reported 5% failed extubation in a cohort of 137 difficult-to-intubate pediatric patients. Of these failed extubation, 85% had severe upper airway obstruction and weighted less than 10 kg, one child needed a tracheostomy, two experienced a hypoxemic cardiac arrest and both later died [50]. In his review, Weatherall uses the following definition: “A difficult extubation should be anticipated when the airway clinician assesses that it is likely that additional techniques, oxygenation methods, or ventilatory support will be required to support the patient after extubation, or when reintubation is likely to be difficult” [51]. The systematic approach described includes risk assessment, readiness for extubation and potential reintubation, execution of the comprehensive plan, and safe transfer of care including continuous oxygenation, support system, and hand-off [52]. Airway exchange catheters have been used in pediatric patients to allow for easier reintubation, as well as extubation over a SGA as described in literature. Not a lot of data is currently available, however, the use of SGA or airway exchange catheter to facilitate extubation lies in the clinician’s hand [53].

Airway Cart

The importance of readily available airway equipment cannot be overstated [19]. A difficult airway cart should be available in every location caring for pediatric patients. Its location should be well indicated and known to everyone, and should be standardized throughout all pediatric floors. Staff need to be educated about the content. The cart should be regularly updated with drawers labeled and organized so that rescue devices are easily found. Only necessary devices should be stocked. Overfilling the airway cart will limit accessibility to the most urgent equipment, and should be avoided. Depending on the institution, one drawer may be used for equipment for the experienced physician, and contain a surgical set for a tracheostomy or a set for a cannula cricothyroidotomy. An institutional airway escalation plan including relevant contact information should be visible on the cart [18].

Human Factors

The updated ASA guidelines underline the value of situational awareness and being mindful of the time lapsed [14]. Human factors play a crucial role in the successful airway management highlighting the importance of training and simulation [19]. The culture of the clinical environment, the interaction between the members, time constraints, and staffing are found to be equally important.

Education and Training

It has been estimated that it takes 1 to 2 decades for original research to be incorporated into routine practice [54]. Stein et al. looked at outcome over time within the PeDI registry, comparing an early cohort (August 2012- January 2015, 785 patients, 13 centers) to a current cohort (March 2017-March 2023, 3935 patients, 43 centers) using a propensity score of 5:1. (1).

The study showed a decrease in the number of intubation attempts, a decrease in the number of attempts with direct laryngoscopy, close to a 50% decrease in severe complications, an increase in first attempt success rate and an increase in apneic oxygenation compared to the early cohort. Direct laryngoscopy is still used frequently, but the persistence of its use has decreased by close to 50%, while the successful use of videolaryngoscopes with standard blades increased from 5% to 31.2% of cases. The study reconfirmed that severe complications increase with more than 3 attempts at intubation. It showed a shorter time of translation from the published analysis into clinical practice by the PeDI collaborators. Further studies will need to show if this change can be confirmed in a wider pediatric community.

Conclusion

In summary, pediatric airway management has unique challenges and risks. The increase in published research and the establishment of data registries have led to significant advancements in our understanding and approach to managing both expected and unexpected difficulties. Through ongoing research, collaboration, and the development of guidelines, clinicians continue to refine skills and strategies to optimize outcomes for the difficult pediatric airway. (Table 2).

Table 2 Critical Pearls Gained from This Review Article
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It is the authors’ opinion that increased knowledge gained from the above-mentioned publications has undoubtedly enhanced the safety of pediatric airway management. Disseminating this knowledge to all health care providers including anesthesiologists, intensivists, and emergency physicians involved in pediatric care is imperative for further improving patient outcomes.