Effect of Lavage Solution Type on Bronchoalveolar Lavage Fluid Cytology in Clinically Healthy Horses.
Authors: Westermann Cornélie M, de Bie Annelieke G, Olave Carla, de Grauw Janny C, Teske Erik, Couetil Laurent L
Journal: Animals : an open access journal from MDPI
Summary
Bronchoalveolar lavage (BAL) is a standard diagnostic procedure for evaluating equine airways, but the choice of lavage solution has remained largely arbitrary despite longstanding concern that acidic saline might trigger inflammatory responses. Westermann and colleagues investigated whether neutral-pH solutions (Ringer's, phosphate-buffered saline, and Plasma-Lyte 148®) would reduce the post-BAL neutrophil influx compared to conventional acidic saline by performing sequential lavages on four different lung lobes in four healthy horses at 48-hour intervals using a randomised crossover design. Irrespective of solution type, neutrophil percentage increased significantly from 1.5% to 14.7% between the two sampling timepoints (p < 0.001), with no statistically significant difference attributable to pH or lobe location. This finding suggests that the iatrogenic neutrophil elevation observed after BAL is a mechanical consequence of the procedure itself rather than a chemical irritant effect, meaning practitioners can continue using standard isotonic saline without concern that pH is exacerbating airway inflammation—a practically valuable conclusion given saline's accessibility and cost-effectiveness in equine clinical settings.
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Practical Takeaways
- •The type of lavage solution (acidic vs. neutral pH) does not affect the post-BAL neutrophil response in healthy horses, so continue using standard saline for cost and practicality
- •Expect neutrophil counts to increase substantially 48 hours after BAL regardless of solution used; interpret cytology results with awareness of this expected inflammatory response timing
- •This finding supports current BAL protocols and eliminates the need to switch to more expensive neutral pH solutions in hopes of reducing post-procedure airway inflammation
Key Findings
- •Mean neutrophil percentage increased significantly from 1.5% to 14.7% at 48 hours post-BAL (p < 0.001), indicating an inflammatory response to the procedure
- •Neutrophil influx was independent of solution type used (saline, Ringer's solution, PBS, or Plasma-Lyte 148®), despite theoretical expectations that neutral pH solutions would reduce inflammation
- •Mean BAL fluid recovery rate was 51% across all treatments with no significant variation by lung lobe sampled
- •Isotonic saline at pH 5.5 remains an appropriate and cost-effective choice for equine BAL procedures