Anaesthesia, 2011, 66, pages 519–531 .....................................................................................................................................................................................................................
Correspondence 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 thoughtprovoking 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 opioidmediated 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. F. S. Xue X. Liao Q. Wang Y. J. Yuan J. Xiong J. H Liu Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China Email:
[email protected].
No external funding and no competing interests declared. Previously posted at the Anaesthesia Correspondence website: http://www.anaesthe siacorrespondence.com.
References 1 Warters RD, Szabo TA, Spinale FG, Desantis SM, Reves JG. The effect of neuromuscular blockade on mask ventilation. Anaesthesia 2011; 66: 163–7. 2 Amathieu R, Combes X, Abdi W, et al. An algorithm for difficult airway management, modified for modern optical devices (AirtraqTM Laryngoscope; LMA CTrachTM): a
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Correspondence Anaesthesia, 2011, 66, pages 519–531 . ....................................................................................................................................................................................................................
2-year prospective validation in patients for elective abdominal, gynecologic, and thyroid surgery. Anesthesiology 2011; 114: 25–33. 3 Kheterpal S, Han R, Tremper KK, et al. Incidence and predictors of difficult and impossible mask ventilation. Anesthesiology 2006; 105: 885–91. 4 McGee JP, Vender JS. Nonintubation management of the airway. In: Benumof JL, ed. Clinical Procedures in Anesthesia and Intensive Care, New York: JB Lippincott, 1992: 110–4. 5 Xue FS, Liao X, Li CW, et al. Clinical experience of airway management and tracheal intubation under general anesthesia in patients with scar contracture of the neck. Chinese Medical Journal 2008; 121: 989–97. A reply
We appreciate the interest Dr Xue et al. have taken in our recent article [1]. Our study was designed to assess the effect of neuromuscular blockade on facemask ventilation and we found that the former facilitates the latter. The cumulative incidence of difficult facemask ventilation on the Han scale was 13.6% in our study, which is indeed higher than the incidence published in previous reports [2–4]. However, the study was not designed to assess the incidence of difficult facemask ventilation, and was not sufficiently powered to do so. Xue et al. are correct in stating that a light plane of anaesthesia may lead to laryngospasm (and subsequent difficult mask ventilation). However, we believe that our doses of induction agents were sufficient to provide an adequate anaesthetic depth. In our study, facemask ventilation was performed by an experienced practitioner (senior resident or nurse anaesthetist), supervised by a board certified anaesthetist. Furthermore, the same practitioner ventilated the lungs before and after the neuromuscular blocker; thereby serving as their own control. 520
We agree with Xue et al. that neuromuscular blockers should not be given to patients with a history of a difficult airway, and also that difficult airway guidelines should be followed. Unfortunately, the American Society of Anesthesiologists does not provide guidance on the management of ‘difficult-to-ventilate’ scenarios before the initial tracheal intubation attempt. We agree that our data do not definitely answer whether mask ventilation should be confirmed before giving neuromuscular blockers. However, it does add considerable weight to the argument that confirmation is not necessary since neuromuscular blockade is known to facilitate tracheal intubation, and we have now shown that it facilitates mask ventilation as well. Clinicians still remain divided on this issue [5], and our hope is that our findings will add value to this important discussion. T. A. Szabo R. D. Warters Medical University of South Carolina, Charleston, South Carolina, USA Email:
[email protected]
No external funding and no competing interests declared. Previously posted at the Anaesthesia Correspondence website: http://www.anaes thesiacorrespondence.com.
References 1 Warters RD, Szabo TA, Spinale FG, DeSantis SM, Reves JG. The effect of neuromuscular blockade on mask ventilation. Anaesthesia 2011; 66: 163–7. 2 Langeron O, Masso E, Huraux C, et al. Prediction of difficult mask ventilation. Anesthesiology 2000; 92: 1229–36. 3 Kheterpal S, Han R, Tremper KK, et al. Incidence and predictors of difficult and impossible mask ventilation. Anesthesiology 2006; 105: 885–91. 4 Amathieu R, Cobes X, Abdi W, et al. An algorithm for difficult airway management, modified for
modern optical devices (Airtraq Laryngoscope; LMA CTrach): a 2-year prospective validation in patients for elective abdominal, gynecologic, and thyroid surgery. Anesthesiology 2011; 114: 25–33. 5 Broomhead RH, Marks RJ, Ayton P. Confirmation of the ability to ventilate by facemask before administration of neuromuscular blocker: a non-instrumental piece of information? British Journal of Anaesthesia 2010; 104: 313. Checking the ability to mask ventilate before administering long-acting neuromuscular blocking drugs
Whereas we previously reported little or no effect of neuromuscular blockade on the ability to mask ventilate the lungs [1], Szabo et al. have now reported that neuromuscular blockade improves mask ventilation [2]. Some readers may erroneously conclude from this result that it is acceptable to administer neuromuscular blocking drugs (NBDs) without first checking the ability to mask ventilate. There are in fact several related, but often confused, questions involved: (i) should we check the ability to mask ventilate before administering NBDs? (ii) should we administer a short- or long-acting NBD? and (iii) can we predict who is difficult to mask ventilate? In relation to the first question, Broomhead et al. divided anaesthetists using a questionnaire into ‘checkers’ (who assess the ability to mask ventilate the lungs before administering NBDs) and ‘non-checkers’ [3]. Checkers claimed they checked ‘so that they could wake the patient up’ but in fact it appeared that when checkers found difficulty with mask ventilation, they nonetheless administered a (usually short-acting) NBD. Broomhead et al. did not understand this logic, citing arguments that even short-acting NBDs do not allow ‘wake-up’ in sufficient time and if neuromuscular blockade improves the airway (as in the
Anaesthesia 2011 The Association of Anaesthetists of Great Britain and Ireland
