Is it unnecessary to confirm successful facemask ventilation before administration of a neuromuscular blocking agent?

We would like to raise some points relating to Warters et al.’s thought-provoking article [1]. Their incidence of difficult facemask ventilation is significantly higher than reported previously in large cohorts of patients undergoing anaesthesia [2, 3]. We are concerned that the drug doses used for induction may have resulted in an inadequate depth of anaesthesia, leading to more frequent airway obstruction and laryngospasm, both common causes of difficult facemask ventilation [4]. Moreover, we do not feel that the authors clearly described if they had used an optimal technique when assessing facemask ventilation. This study showed that after induction of anaesthesia, administration of rocuronium did not worsen facemask ventilation in any patient, but improved it in 67% of cases. These results are supported by a recent study [2]. However, we still believe that the available evidence is not strong enough to answer the question of whether or not one should routinely ensure successful facemask ventilation before administering a neuromuscular blocking drug (NBD), as these studies have excluded patients with known or predicted difficult airways. In patients with normal airways, the usual causes of difficult facemask ventilation are airway or glottic closure due to irritation and opioid-mediated muscle rigidity [4]; these improve with neuromuscular blockade. In contrast, in patients with difficult airways, common causes of difficult facemask ventilation are overcrowding and dysfunction of upper airway structures due to limited mandibular space and reduced displaceability of the soft tissues. In this case, loss of muscle tone by neuromuscular blockade may cause further upper airway soft tissue collapse, resulting in complete upper airway obstruction that cannot be relieved by routine airway manoeuvres [5]. We believe that successful facemask ventilation should be confirmed before administering a NBD, especially in patients with a known or predicted difficult airway. If a patient’s lungs are difficult to ventilate by facemask following induction of anaesthesia, our routine practice is an immediate attempt at direct laryngoscopy. If the view is good, and the chances of achieving successful tracheal intubation are high, we give a NBD. However, if the view at laryngoscopy is poor and tracheal intubation fails, we immediately follow the rescue airway algorithm for a ‘cannot intubate – cannot ventilate’ scenario, including laryngeal mask airway insertion. No external funding and no competing interests declared. Previously posted at the Anaesthesia Correspondence website: http://www.anaesthesiacorrespondence.com.