Measuring Upper Airway Cross Sectional Areas During Residual Neuromuscular Blockade and After Reserval

Introduction

Postoperative residual neuromuscular can cause severe respiratory complications. One of these is pharyngeal dilator muscle weakness, which can lead to airway obstruction. One way to prevent this is to have objective neuromuscular monitors to track the degree of muscle relaxation and use the measurements to guide the the suspension of neuromuscular block. Monitoring the muscle relaxant effect is not a mandatory component of anaesthesia and is therefore often omitted in anaesthesiologists. In our study, the investigators investigated whether, at the end of surgery, only patients extubated at the end of surgery, based on clinical signs, have an airway diameter reduction and how this relates to the degree of residual muscle relaxation. Our single-centre, prospective study included 20 patients. The patients' narcosis by the anaesthetist, as is often done in routine anaesthesia work, is without monitoring neuromuscular block and on the basis of clinical signs deciding on extubation.

Sample size calculation

In a previous study, Eikermann and associates (Eikermann M, Vogt FM, Herbstreit F, Vahid-Dastgerdi M, Zenge MO, Ochterbeck C, de Greiff A, Peters J. The predisposition to inspiratory upper airway collapse during partial neuromuscular blockade. Am J Respir Crit Care Med. 2007;175(1):9-15.) using MRI technique described a minimal retroglossal diameter after a total neuromuscular recovery of 20.2±5.2 mm and a 20% decrease of this diameter at TOFR=0.8. the investigators hypothesised that in the present study, the decrease of the retroglossal cross-section area during inspiration will decrease by 30% in patients with residual neuromuscular block of any severity. Using and alpha of 0.05 and a power of 90%, 8 patients were calculated to be necessary to prove our hypothesis. In a previous study, it was found that in our working group the amount of residual neuromuscular block (as defined TOFR <90%) during spontaneous recovery at the end of surgery approximates 45% of all cases (Nemes R, Fülesdi B, Pongrácz A, Asztalos L, Szabó- Maák Z, Lengyel S, Tassonyi E. Impact of reversal strategies on the incidence of postoperative residual paralysis after rocuronium relaxation without neuromuscular monitoring: A partially randomised placebo controlled trial. Eur J Anaesthesiol. 2017;34(9):609-616.). With respect to this, the investigators planned to include 18 patients. the investigators also calculated with eventual dropouts and finally included 20 patients.

Procedure of the investigation