Blockade of 'alveolar' and airway reflexes by local anesthetic aerosol in dogs.

To determine whether local anesthetic aerosol could selectively block a reflex thought to originate from the alveoli, two small particle bupivacaine aerosols (mass median diameters 1.0 and 1.7 micron) were administered on separate occasions to spontaneously breathing anesthetized dogs. Both aerosols resulted in a small but statistically significant increase in VT and one produced an increase in f. The pulmonary chemoreflex to right heart injection of capsaicin, the cough reflex and the Hering-Breuer inflation reflex were unaffected. The ability of a large particle aerosol (mass median diameter 4.8 micron) to block these reflexes was also assessed. This aerosol produced a progressive slowing and deepening of breathing which was maximal after 20 min of aerosol inhalation. Ten min of this aerosol attenuated the pulmonary chemoreflex and abolished the cough and inflation reflexes; 20 min abolished all reflexes. These had recovered by about 1 h after aerosol. Intravenous bupivacaine had no effect on breathing or any reflex. We conclude that a local anesthetic aerosol can block reflexes arising from the alveoli, but not selectively.