Effects of 0.05% chlorhexidine lavage on the tarsocrural joints of horses.

The research study investigates the effects of chlorhexidine lavage on the joints of horses, concluding that even at the lowest bactericidal concentration, it leads to increased lameness and inflammation, and is therefore not recommended.

Overview of Research Design

• The study involved six horses. For each, one tarsocrural joint (ankle joint) was lavaged with a 0.05% solution of chlorhexidine diacetate, while the contralateral joint, serving as a control, was lavaged with lactated Ringer’s solution which is a common sterile mixture used in medicine.
• Animals were evaluated for lameness each day, and synovial fluid samples (the fluid that lubricate the joints) were collected at three different time points: on days 1, 4, and 8.
• Several parameters in the collected synovial fluid were measured, including protein concentration, total and differential leukocyte counts (white blood cells), and mucin clot formation.
• On day 8, after euthanizing the animals, samples of synovium (the membrane that lines the joints) and osteochondral (referring to both bone and cartilage) samples were collected for morphological assessment and the examination of proteoglycan staining (a method of visualizing cartilage).

Findings of the Study

• Lavage with the chlorhexidine solution led to clear signs of lameness in the horses. Although this lameness reduced over time, some effects were visible even by day 8.
• The use of chlorhexidine significantly increased synovial protein concentration, especially on day 1.The general implication is that it led to an inflammatory response in the joint.
• The number of white blood cells, particularly polymorphonuclear (PMN) cell counts were noted to be increased on day 1 after chlorhexidine lavage. Leukocyte counts returned to normal by day 4, however, PMN cell counts remained high until day 8 and this indicates a persistent inflammatory response.
• The study noted chlorhexidine lavage caused synovial ulceration (sores), inflammation, and a high accumulation of fibrin (a protein that helps in blood clot formation) within the joint.
• No significant differences in proteoglycan staining were found between the joints lavaged with chlorhexidine and those lavaged with the control solution, showing that this treatment did not cause visible changes to the cartilage.

Conclusion

• The researchers concluded that the use of a 0.05% chlorhexidine diacetate solution for joint lavage in horses potentiate an inflammation. Therefore, its use, even at the lowest known bactericidal concentration, is not recommended for equine joints.