Effects of partial paralysis on the swallowing reflex in conscious humans.

The ability to swallow may be affected by administration of a small dose of muscle relaxant. To test the hypothesis that a subparalyzing dose of a muscle relaxant can impair swallowing, effects of partial paralysis produced by pancuronium on the swallowing reflex were investigated in eight conscious subjects. The swallowing reflex was induced by a bolus injection or a continuous infusion of distilled water into the mesopharynx. The swallowing function was assessed by electromyogram of suprahyoid muscles (EMGSH), mesopharyngeal pressure (Pmeso), and hypopharyngeal pressure (Phypo). Peripheral muscle activity was simultaneously determined by train of four ratio (TOFR) of hypothenar muscles to electrical stimulation of ulnar nerve and by hand grip strength (HGS). Following control measurements, measurements during partial paralysis and after recovery from partial paralysis were performed after intravenous administration of pancuronium 0.02 mg/kg. Partial paralysis significantly depressed EMGSH (bolus injection 44.1 +/- 10.0%, continuous infusion 55.9 +/- 10.2% of control value, P less than 0.01). Pmeso also significantly decreased (bolus injection 64.9 +/- 6.7 to 47.8 +/- 5.8 mmHg, P less than 0.01; continuous infusion 63.4 +/- 7.7 to 52.5 +/- 5.8 mmHg, P less than 0.05). The TOFR of peripheral muscles decreased to 81.4 +/- 6.7% of control value (P less than 0.01), and HGS was reduced from 44.6 +/- 1.9 to 39.4 +/- 2.0 kg (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)