Abstract title
Equine sinus lavage: current clinical practices and translational insights from human medicine

Take-home messages
• Equine sinus lavage practices are highly variable, with no clear standardisation in fluid choice, sequence, or use of additives across clinicians.
• The primary therapeutic effect of lavage is mechanical, with volume and frequency likely more influential than the specific solution used.
• Use of antiseptics is inconsistent and often not standardised, raising concerns about cytotoxicity, impaired mucociliary function, and unintended microbial selection.
• Human sinonasal research highlights the importance of solution composition (tonicity, pH, ionic balance), suggesting a clear opportunity to improve and standardise equine lavage protocols.

Background
Sinus lavage (sinus flushing) has long been a cornerstone in the management of equine sinus disease, particularly in cases of dental sinusitis, primary sinusitis, and post-surgical care. Despite its widespread use, there is currently no consensus on optimal lavage protocols in equine practice and the performed practices do not seem to have substantial medical evidence
Clinical approaches vary substantially in terms of:
• irrigation solutions used
• sequence of flushing (initial vs terminal lavage)
• use and concentration of additives (e.g. antiseptics)
• volume, frequency, and delivery methods
In contrast, human medicine-particularly in chronic rhinosinusitis (CRS)-has progressively refined sinonasal irrigation strategies based on mucosal physiology, antimicrobial balance, and patient outcomes.

This study aimed to:
1. Characterise current sinus lavage practices among equine clinicians
2. Identify areas of variability and inconsistency
3. Compare these findings with established principles from human sinonasal irrigation

Materials and Methods
An anonymous, cross-sectional survey was distributed to equine clinicians and specialists. The questionnaire explored:
• irrigation solutions and sequences
• use and rationale of additives
• lavage volume, frequency, and duration
• catheter use and management
• variation between primary and secondary sinusitis
Descriptive statistics were used to summarise practice patterns.

Results
A total of 92 complete responses were analysed.

Marked variability in irrigation solutions
A wide range of primary irrigation solutions was reported, including:
• isotonic saline
• balanced electrolyte solutions (e.g. Hartmann’s)
• tap water (with or without pre-boiling)
• sequential combinations of these
A significant proportion of respondents reported multi-stage lavage protocols, typically involving an initial mechanical flush followed by a secondary solution.

Extensive variation in additive use
The use of additives (e.g. povidone-iodine, antibiotics, other agents) showed considerable heterogeneity:
• Additives were frequently used only in terminal lavage phases, rather than throughout the procedure
• Concentration was often not standardised, with many respondents relying on subjective estimates (e.g. “a splash” or visual dilution)
• Clear protocols or defined concentrations were uncommon

Volume and frequency: predominantly empirical
Lavage strategies were largely guided by clinical judgement rather than defined protocols:
• Large variability in volume and frequency
• Decision-making was primarily influenced by case severity, response to treatment, and practical constraints

Catheter use and management
A broad range of catheter types and management strategies were reported, reflecting practical adaptation rather than standardisation.

Discussion
This study highlights substantial heterogeneity in equine sinus lavage practices, particularly regarding irrigation composition and additive use.

Mechanical vs chemical effects
Findings suggest that lavage in equine practice is primarily considered a mechanical intervention, relying on volume and repetition to remove debris and infectious material.
This aligns with human data, where:
• large-volume, low-pressure irrigation is preferred
• mechanical clearance is a key therapeutic mechanism

Additives: potential benefits and risks
The widespread but inconsistent use of antiseptics such as povidone-iodine raises important considerations:
• Antiseptic efficacy depends on concentration and contact time, both of which are difficult to control in lavage settings
• High concentrations may be cytotoxic, impairing epithelial integrity and mucociliary clearance
• Subtherapeutic concentrations may contribute to selective pressure on microbial populations
Human studies demonstrate that low-concentration PVP-I (≈0.08%) can improve outcomes in refractory CRS without impairing mucosal function. However, the non-standardised concentrations reported in this study suggest that equine protocols may frequently fall outside this therapeutic window.

Importance of solution composition
Human sinonasal irrigation research emphasises that lavage solutions should consider:
• Tonicity
• pH buffering
• ionic composition
Balanced solutions (e.g. Ringer’s) have been associated with improved outcomes compared to normal saline, likely due to better preservation of epithelial function. Hypertonic solutions may improve mucociliary clearance but are associated with increased irritation at higher concentrations (>3%). These principles are largely absent from current equine practice, where solution selection is often pragmatic rather than physiologically driven.

Emerging adjuncts
Novel additives such as xylitol and manuka honey have demonstrated antimicrobial and anti-biofilm properties in human medicine, with improved culture negativity in some settings. Their role in equine sinus disease remains unexplored but represents a potential area for future investigation.

Safety considerations
The use of non-sterile water remains a concern. In human medicine, unsterile irrigation has been associated with severe complications including amoebic meningoencephalitis. Comparable risks, including bacterial complications, have been reported in equine sinus surgery.

Conclusion
Equine sinus lavage practices are characterised by significant variability and limited standardisation, particularly in relation to irrigation solutions and additive use. Comparison with human sinonasal irrigation highlights several key areas for improvement:
• consideration of solution composition (tonicity, pH, ions)
• cautious and standardised use of antiseptics
• recognition of lavage as primarily a mechanical intervention
• need for evidence-based protocols

This study provides a foundation for future work aimed at developing guidelines and consensus-driven approaches to equine sinus lavage. At GVEH, the aim is to prepare a lavage solution that supports mucosal function while maintaining mechanical cleaning efficiency. Based on human literature composition data the solution is designed to be:
• Slightly hypertonic (approximately 1.5–3%) to support mucociliary clearance
• Buffered to a neutral to slightly alkaline pH (around pH 7–7.5) using sodium bicarbonate
• Balanced in composition to minimise irritation of the sinus epithelium

In practical terms, this is achieved by:
• Mixing salt and sodium bicarbonate (baking soda) in a 2:1 ratio
• Adding approximately 5.5 g of this mixture per 500 mL of water (scaled accordingly for larger volumes)
• Adjusting bicarbonate content as needed to achieve a near-neutral pH

In addition, xylitol (5% w/v) is included as a potential adjunct due to its antibacterial and anti-biofilm properties. Tap water is used as the base fluid, with attention to cleanliness and preparation standards and is pre-boiled before mixing.