The effect of intravenous lidocaine infusion on bronchoalveolar lavage cytology in equine recurrent airway obstruction.

This research investigates whether intravenous infusions of lidocaine can reduce neutrophilic inflammation in horses with recurrent airway obstruction (RAO). Unfortunately, it does not seem to provide the expected results.

Study Objective and Methods

• The main purpose of this study was to determine if lidocaine, widely used for its anti-inflammatory properties, could alleviate neutrophil (a type of white blood cell) induced inflammation within the airways of horses suffering from Recurrent Airway Obstruction (RAO), a common condition in equine species similar to asthma in humans.
• The researchers used six RAO-affected horses currently in a remission period and engaged them in a randomized cross-over design experiment. The horses were either given a lactated Ringer’s solution (LRS) or lidocaine hydrochloride intravenously.
• The intervals between treatments was a minimum of four weeks, during which time the horses were allowed to graze. The treatment was given as a continuous infusion which started 4 hours before exposure to a hay and straw challenge and continued for the next 68 hours.
• Clinical scores (severity of sickness), maximal change in pleural pressure (∆Ppl(max), a measure of lung function), bronchoalveolar lavage fluid (BALF) cytology (cell exam from fluid in the lungs) and plasma lidocaine concentrations were monitored and measured at the beginning and at the end of the challenge on day four.

Results of the Study

• At the beginning of the study, the horses showed no significant differences between the two treatments.
• The plasma lidocaine concentration remained above 1100 ng/mL. However, post-challenge results indicated an increase in Clinical Score from 2/8 (median) to 4/8 and ∆Ppl(max) from 3.6 cmH2O to 9.62 cmH2O, but there were no significant differences between the two treatments.
• The proportion of neutrophils was similar for both treatments, however, the total number of cells found in the BALF significantly increased in the group receiving lidocaine, suggesting a possible increase in inflammation.

Conclusions

• Contrary to the initial hypothesis, intravenous lidocaine did not reduce the neutrophil-induced inflammation in horses with RAO. The researchers conclude there may be more complexity to the role of neutrophils in RAO and lidocaine’s effect on them than currently understood.
• Though the study provides valuable insight into the roles of neutrophils and lidocaine in lung inflammation, more research is needed to understand the exact mechanisms involved and to explore potential therapeutic agents to mitigate inflammation in RAO.