Our observations confirm that the LMA® Gastro™ Airway can be successfully employed as a primary airway technique for ERCP procedures in some patients. The case that required conversion from LMA® Gastro™ Airway to an endotracheal tube was due to the gastroenterologist being unable to get the gastroscope pass through the endoscope channel of LMA® Gastro™ Airway. This happened to be the third case since this technique was adapted by us, possibly noting a difficulty during the early learning phase.
Gastroenterologists are unlikely to adopt the LMA® Gastro™ Airway for complex endoscopic intervention, unless success is demonstrated in both emergency and elective cases across a diverse group of patients. Our study group had a mixture of low and high risk cases giving rise to anaesthetic as well as procedural challenges. Although formal interviews were not conducted, it was evident that the gastroenterologists were satisfied with the device.
A medicolegal analysis of malpractice claims involving anesthesiologists, has shown that gastrointestinal endoscopy procedures comprised the largest portion of “outside operating suite” malpractice claims in the US [19]. Of these, ERCPs represented the maximum likelihood of payout (91% compared with 37.5% of colonoscopies, and 25% of combined endoscopy/colonoscopy procedures). In view of the morbidity associated with endoscopy interventions, there has been an increased interest recently looking for devices that can facilitate better oxygenation and airway control. General anaesthesia with an endotracheal tube may be considered in some ways a “safe option” in the prone position in terms of having a secured airway and a lower ERCP failure rate [20], and there may be a reduction in some complication rates. However, intubation has drawbacks. In addition to the well-known problems associated with insertion of the tube, managing a paralysed intubated patient in a semi-prone position creates additional challenges. Furthermore, there may be a prolongation of anaesthetic time due to the use of muscle relaxants.
Although the first generation laryngeal mask airways have been used successfully for ERCPs, the absence of a dedicated endoscopic channel and a gastric aspiration port are obvious limitations [8,9,10]. The GLT is perhaps the most widely evaluated supraglottic airway device for endoscopies [4, 11, 12]. Some of the drawbacks of this device include: loss of position of the device after insertion when turning the patient prone, only one size, and it can be used only in patients over 155 cm tall. The design is unfamiliar to many anaesthetists, and its method of use is slightly different compared to other commonly used supraglottic airways.
Difficulty introducing duodenoscope into the oesophagus may be encountered due to a tight/thick crico-pharyngeus muscle and/or significant anterior cervical osteophytes. This can occur especially in the elderly population, either during sedation without airway adjuncts or even under general anaesthesia with endotracheal intubation. Our gastroenterologists believe that this problem was not encountered during their intubation with the duodenoscope in our patient population. It may be attributed to the alignment of the endoscope channel running parallel to the airway lumen communicating distally with the upper oesophageal sphincter where the endoscope exits. This may indicate another potential benefit using LMA® Gastro™ Airway.
The LMA® Gastro™ Airway has dedicated independent channels for both endoscope insertion (16 mm internal diameter) and oxygenation. It also has an integrated bite block, and an adjustable holder to secure the device (Fig. 1). Some of the advantages that are claimed are: improved airway patency, it is available in three sizes: 3, 4 and 5; familiarity and ease of insertion - it is designed similar to other LMAs; insertion possible in lateral or prone position; dynamic flexibility allowing the device to remain in place with head movement; inbuilt cuff pressure monitoring pilot balloon; and allows endoscopes up to 14 mm in size as compared to 13.8 mm with GLT [11].
The 2 cases associated with intraoperative airway events were semi-urgent presentations. Self-resolving mild oropharyngeal bleeding was noted in one. The other emergency case involved an anticipated difficult airway in the context of Down’s syndrome and central obesity (BMI 31). Mild laryngospasm was noted both intraoperatively and in PACU. This was attributed to induction using a volatile anaesthetic in view of needle phobia and the patient’s airway characteristics. Although the procedure was completed with LMA® Gastro™ Airway, the anaesthetic team recommended the use of an endotracheal tube for similar procedures in the future.
Interestingly, LMA® Gastro™ Airway was employed as a rescue technique in one instance where there the SpO2 dropped to 86% despite the application of dual nasopharyngeal airways and high flow nasal oxygen therapy. The ease of insertion in a non-supine position and enabling successful ventilation is one of the notable features of this device. Although not formally evaluated, our patients positioned themselves in either lateral or prone position prior to preoxygenation. Unlike other endoscopy airway adjuvants, the LMA® Gastro™ Airway offers reliable CO2 monitoring. Oxygenation and ventilation were well maintained in all our cases.
ERCP outcome failure was reported in 5 occasions. While failed cannulation of the bile duct was attributed in three, inability to cannulate ampulla and failed stone extraction were identified in one each. It was evident that the failures were not due to the choice of LMA® Gastro™ Airway as an airway intervention. There is an argument that the endoscope manipulation may be difficult from the extra-oral end of a supraglottic device, rather than a more proximal oropharyngeal entry offered by other airway adjuvants [21]. Nonetheless, the success rate shown in our study diminishes this concern.
It is a contentious issue as to whether non-anaesthesia providers could deliver deep sedation with propofol for a complex intervention such as ERCP [22]. The practice varies globally. Monitoring brain function, some sources have shown that 96% of patients consenting for moderate to deep sedation for endoscopy (including ERCP) were indeed under deep general anaesthesia [23]. The sedation practice (deep propofol based) for endoscopy in Australia is predominantly driven by anaesthetists [24]. A survey on ERCP practice across gastroenterology practitioners in Australia performing the intervention revealed that 97.5% of their cases were assisted by anaesthetists [25]. It has been shown that higher ASA category (> 3) patients would require frequent airway manoeuvres during sedation for ERCPs (1). Hence, LMA Gastro may have a greater role in complex interventions attempted on sicker patients.
Limitations and strengths
This observational study did not allow for formal matched comparison of efficacy and safety with other conventional airway options such as moderate to deep sedation or other airway adjuvants including GA with ETT and sedation with low flow nasal cannula. Choice of the airway technique was at the discretion of the anaesthetist. Hence, confounding factors in patient selection for the LMA® Gastro™ Airway technique could be a further limitation. Nonetheless, this is the largest series analysing LMA® Gastro™ Airway for ERCPs. Over half of the LMA® Gastro™ cases (37 out of 64) were of the ASA III and IV category and difficult airway was anticipated in 10, implying that the technique was employed on a complex case mix. Future large trials are warranted to analyse the safety and cost implications of this technique in specific population groups such as those with known or suspected sleep apnoea, high BMI and diverse co-morbidities.
