Abstract

Following induction of anaesthesia, the practice of checking the ability to mask ventilate before administering neuromuscular blocking drugs remains controversial. In this context, we wished to study effect of neuromuscular blockade on the ease of facemask ventilation by measuring changes in tidal volume. Objectives: Objectives of the study was to evaluate any change in expired tidal volume after administering neuromuscular blocking drugs during pressure-controlled ventilation in anesthetized patients and to assess the effect of body mass index & neck circumference on tidal volume and ease of mask ventilation. Methods: After approval from the ethical committee and obtaining informed written consent from each patient, 87 adult patients aged > 18 years, of ASA physical status 1–2, scheduled to undergo elective surgery under GA were included in this observational study. Preoperative assessment of participants was done on the previous day and the participants were premedicated. Following preoxygenation, general anaesthesia was induced using fentanyl and propofol. The patients’ lungs were ventilated using PCV at 15 cmH2O pressure, 12 breaths/min. Initial grade of mask ventilation was assessed as described by Hans et al. Anaesthesia was maintained with sevoflurane with a FGF of O2 6l/min. Once stabilized, the expired tidal volumes with each breath were recorded for 2 min. After administration of Vecuronium, following the absence of twitches on train of four, individual patient values for expired tidal volume at 1 min, 2 min and 3 min after the onset of block were measured and each averaged to get a mean tidal volume. The mean expired tidal volumes were compared using paired t tests. Results:There was a significant increase in the mean tidal volume (SD) following administration of neuromuscular blocking drugs from 451 (61.5) ml to 557(72.5) ml (p< 0.001) & no deterioration in tidal volume in any of the patients in whom neuromuscular blocking drugs were administered. The increase in mean expired TV was significantly higher in the low-BMI group compared with the high-BMI group. 71% of patients with neck circumference >40 was classified as grade 3 mask ventilation. When comparing the low-neck circumference group (neck circumference < 40) to the high neck circumference group, the increase in mean expired tidal volume was significantly higher in the low-neck circumference group (p<0.001) Conclusion: Facemask ventilation became easier after administering neuromuscular blocking drugs, as evidenced by improvement of expired tidal volume. Hence, neuromuscular blocking drugs can be considered to facilitate Facemask ventilation in patients with normal airway.

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