Use of the ProSeal Laryngeal Mask to protect the airway from methylene blue dye

Introduction

In the trauma patient tracheal soiling is usually from the upper airway [1]. Although the ProSeal Laryngeal Mask Airway (LMA) gives a better seal pressure than the standard LMA [2] and is designed to prevent inadvertent gastric insufflation, and thus should reduce aspiration of gastric contents, its ability to protect the airway from material already in the mouth has not been formally assessed.

Method

After local ethics committee approval, 13 ASA 1 and 2, starved patients undergoing elective general anaesthesia gave informed consent. Only patients with grade 1 or 2 direct laryngoscopic views were included. At induction of anaesthesia, an appropriately sized ProSeal LMA was placed into the larynx and the cuff inflated. Ten millilitres of 0.1% methylene blue dye was instilled in the mouth. Full monitoring was used and adequate ventilation ensured throughout. At the end of surgery, or after a minimum of 10 min, all dye was suctioned away and the oral cavity dried with swabs. The ProSeal LMA was removed and the airway examined by direct laryngoscopy for dye staining. Other adverse events were also noted.

Results

No dye was detected in the trachea of 10/13 (77%) patients. Two of 13 (15%) of the patients had significant blue staining of the vocal cords. One patient developed stridor following dye removal, prior to the ProSeal LMA removal, and the trachea was intubated for the remainder of the duration of surgery. There were no problems at extubation, and the trachea was free from dye.

Conclusions

The ProSeal LMA failed to protect 2/13 (15%) of patients from aspiration of dye from the oral cavity. In the trauma setting blood and oral debris may therefore not be prevented from entering the airways. One of these failures may have occurred after patient movement; however, patient movement would be expected in the trauma situation.