Sir,

An otherwise ASA I, 5ft.6inches, 34 yr old lady, weighing 64kg, was posted for laparoscopic cholecystectomy. Her airway examination as according to the Benumof’s 11 parameters revealed no airway difficulty. General Anaesthesia with controlled ventilation was planned for surgery. A supraglottic airway device (Proseal LMA #4) was selected for securing the airway. The patient was induced with propofol 130mg. Isoflurane 1.2% + 66% N₂O in O₂ was used to deepen the plane of anaesthesia after confirming loss of eye reflex and hemodynamic stability. 40 mg rocuronium was administered after confirming ability to ventilate with bag and mask. Proseal LMA insertion was attempted 3 minutes later. However considerable difficulty was encountered during insertion of Proseal LMA due to the presence of bilateral, medially protruding, upper canines and premolars into the oral cavity which were reducing the space available for the negotiation of the Proseal LMA. Consequently the #4 Proseal LMA was replaced with one of a smaller size (#3), which was inserted successfully by rail-roading it over a 14G Ryle’s tube inserted orally into the esophagus.

Benumof’s 11 parameters (see below) can prove extremely valuable for identification of difficult airway. However as evidenced by the above scenario it is not completely fool-proof. Hence rather than blindly following the 11 parameters suggested by Benumof, it would be better to look at the contour of the oral cavity and the airway as a whole during airway assessment.

Figure 1

Table 1: Benumof’s 11 parameters for predicting difficult airway

Figure 2

Figure 1: Examination of oral cavity. Note the medially protruding bilateral upper canines and premolars.