Partial neuromuscular block impairs arytenoid abduction during hypercarbic challenge in anesthetized dogs.

OBJECTIVE

To evaluate the effect of two levels of partial neuromuscular block (NMB) on arytenoid abduction, tidal volume (V) and peak inspiratory flow (PIF) in response to a hypercarbic challenge in anesthetized dogs.

STUDY DESIGN

Prospective laboratory study.

ANIMALS

Eleven healthy male Beagle dogs aged 3-5 years.

METHODS

Dogs were anesthetized with propofol and dexmedetomidine infusions. The rima glottidis was observed via an endoscope placed through a laryngeal mask airway. Atracurium infusion was titrated to obtain two levels of partial NMB. The normalized glottal gap area (NGGA; glottal gap area normalized to height squared of rima glottidis) at peak inspiration during a hypercarbic challenge (10% CO inspired for 1 minute) was measured at baseline, during mild [train-of-four (TOF) ratio 0.4-0.6] and shallow (TOF ratio 0.7-0.9) NMB, and 30 minutes after spontaneous recovery from NMB. The V and PIF were measured at the same time points and compared using anova for repeated measures and Tukey's post hoc tests.

RESULTS

The NGGA and V were significantly lower than baseline during both levels of partial NMB with no difference between mild and shallow NMB (p < 0.05). They returned to baseline values after spontaneous recovery from NMB. PIF was not altered significantly during partial NMB.

CONCLUSIONS AND CLINICAL RELEVANCE

The NGGA and V at peak inspiration in response to a hypercarbic challenge were reduced during partial NMB block, with decreased abduction of the arytenoid cartilages. This dysfunction was present even at shallow levels of NMB.