The Effect of Intravenous Lidocaine Infusion on Bronchoalveolar Lavage Cytology in Equine Recurrent Airway Obstruction

Abstract

Background: Lidocaine decreases neutrophilic inflammation in models of acute lung injury and decreases inflammation in asthmatic patients. Neutrophilic bronchiolitis develops in recurrent airway obstruction (RAO), but it remains unknown if lidocaine infusion decreases neutrophil migration into the airways. Hypothesis: Lidocaine decreases neutrophilic inflammation as measured in BALF in RAO-affected horses. Animals: Six RAO-susceptible horses in remission. Methods: In a randomized cross-over design, horses received lactated Ringer's solution (LRS) IV or lidocaine hydrochloride IV with a minimum of 4 weeks at pasture between treatments. Treatments were delivered as continuous infusions beginning 4 hours before and for 68 hours during exposure to hay and straw challenge. Clinical score (CS, grade 0-8), maximal change in pleural pressure ({increment}Pplmax), and bronchoalveolar lavage fluid (BALF) cytology were measured at baseline and the end of challenge (day 4). Plasma lidocaine concentrations were monitored daily. Results: At baseline, there were no significant differences in variables between treatments. Plasma lidocaine concentration was consistently > 1100 ng/mL. After challenge, CS increased significantly [baseline: 2/8 (2-3), [median (interquartile range)]; day 4: 4/8 (4-5) P = .0006] as did {increment}Pplmax [baseline: 3.6 (2.63-4.95) cmH20; day 4: 9.62 (6.5-16) P = .0036], but there was no difference between treatments. Percentage of neutrophils was not different between treatments, but lidocaine infusion significantly increased BALF total cells [baseline: LRS 2.18 ± 0.82 × 105 cells/mL (mean ± SD), lidocaine 1.6 ± 0.3 × 105, day 4: LRS 2.0 ± 0.88 × 105, lidocaine 4.4 ± 2 × 105 (P = .0045)]. Conclusions and Clinical Importance: Lidocaine does not decrease neutrophilic inflammation in RAO. © 2012 by the American College of Veterinary Internal Medicine.