Imagine this clinical scenario: you are seeing an increasing number of pet rabbits in practice, many of which need to undergo procedures requiring general anaesthetic. You have always used endotracheal intubation for such procedures, but given the relatively high anaesthetic death risk for rabbits and various complications that can be experienced with endotracheal intubation, you are interested in finding out more about supraglottic airway devices which are gaining ground as an alternative.
You decide to consult the literature to explore how the use of supraglottic airway devices compares to endotracheal intubation for ease of use in achieving a patent airway and maintaining stable anaesthesia in domestic rabbits.
The evidence
Five papers were reviewed: four randomised controlled trials (Engbers et al., 2017; Comolli et al., 2020; Toman et al., 2015), one of which was a randomised crossover trial (Wenger et al., 2017), and one peer-reviewed conference proceeding (Cruz et al., 2000). Two breeds were studied (Norfolk and New Zealand White), with sample sizes ranging from 8 to 24 rabbits. The main outcomes considered were mucosal damage, loss of airway seal, ability to achieve positive pressure ventilation and ease of application.
Limitations of the evidence included universally small sample sizes, with power calculations only undertaken in Wenger et al. (2017); the inclusion of only two breeds; and the exclusive focus on healthy adult rabbits with low anaesthetic risk based on the American Society of Anesthesiologists’ physical status grading scale (2020). Further, a variety of agents were used to premedicate and induce patients, which could potentially have affected the ease of application of different airway devices, the sedation quality and the stress levels of each subject.
Only one study assessed the difference between endotracheal intubation and supraglottic airway devices while the subjects were undergoing a surgical procedure common in general practice
Only one study assessed the difference between endotracheal intubation and supraglottic airway devices while the subjects were undergoing a surgical procedure common in general practice (GP) (Comolli et al., 2020). The subjects of two studies were euthanised while under anaesthesia (Engbers et al., 2017; Comolli et al., 2020); therefore, the results of these studies may be less applicable to cases of pet rabbits undergoing anaesthesia for surgery.
Additionally, blind endotracheal intubation may have affected the level of tracheal injury; long-term recovery was not assessed; and inexperienced or, conversely, highly experienced anaesthetists performing the intubations and placements may not be comparable to the individual GP experience.
The results
All studies found applying a supraglottic airway device was faster than intubation with an endotracheal tube. Where measured, most physiological parameters relevant to the assessment of the patient during anaesthesia did not differ between these two groups, although Comolli et al. (2020) found higher levels of pCO2 in anaesthetised rabbits with a supraglottic airway device fitted. Further, this study found that supraglottic devices were more easily displaced during patient movement, supporting findings reported elsewhere in the literature (Crotaz, 2010; Bateman et al., 2005).
Where measured, most physiological parameters relevant to the assessment of the patient during anaesthesia did not differ between these two groups
When comparing mucosal damage to the trachea, Engbers et al. (2017) found histological evidence of damage was significantly greater when using an endotracheal tube, whereas Comolli et al. (2020) found no significant difference between either device. This could potentially be due to use of the blind technique by Engbers et al., whereas Comolli et al. visualised the trachea during endotracheal intubation.
Wenger et al. (2017) showed that more attempts were required to place the endotracheal tube than the supraglottic device, which could explain the further damage to the oral cavity and tracheal mucosa.
Conclusion
Based on the current available evidence, endotracheal intubation is a useful option for maintaining a patent airway and anaesthesia in rabbit patients, although it can cause tracheal damage if conducted blindly.
Supraglottic airway devices can be used as an alternative option where the speed of obtaining a patent airway is imperative. This is because these devices may be easier and faster to apply, especially by inexperienced practitioners without the necessary equipment for safe endotracheal intubation. Supraglottic devices can also be used in cases where practitioners have not been successful in obtaining an airway via endotracheal intubation. Supraglottic devices are unsuitable for procedures requiring patient movement and/or access to the oral cavity due to the size and ease of the loss of the seal during movement, potentiating the risk of aspiration.
The final choice of airway maintenance device should be based on the availability of equipment, the training of the practitioner and the procedure undertaken
The current evidence demonstrates that both devices can be used effectively to maintain anaesthesia in rabbit patients. However, the final choice of airway maintenance device should be based on the availability of equipment, the training of the practitioner and the procedure undertaken. More research in clinical settings would be beneficial, especially with recovery rate and long-term effects as outcomes studied.
| The full Knowledge Summary can be read in RCVS Knowledge’s open access journal Veterinary Evidence. |
Disclaimer
The application of evidence into practice should take into account multiple factors, not limited to individual clinical expertise, patient’s circumstances, owner’s values, the individual case in front of you, the availability of therapies and resources and the country, location and/or clinic where you work.
Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.
