EFFECTS OF 0.05-PERCENT CHLORHEXIDINE LAVAGE ON THE TARSOCRURAL JOINTS OF HORSES

In six horses, a 0.05% solution of chlorhexidine diacetate was used to lavage one tarsocrural joint; the contralateral control joint was lav aged with lactated Ringer's solution. Horses were evaluated daily for lameness. Synovial fluid samples were collected on days 1, 4, and 8 fo r determination of protein concentration, total and differential leuko cyte counts, and mucin clot formation. After death on day 8, synovium and osteochondral samples were collected from the tarsocrural joints f or examination of morphology and proteoglycan staining. Lavage with ch lorhexidine solution caused lameness that was reduced but still eviden t at day 8. Synovial protein concentration was significantly increased by chlorhexidine lavage; the greatest increase occurred on day 1. Joi nt lavage increased synovial leukocyte counts on day 1, primary by inc reasing polymorphonuclear (PMN) cell counts. Although total synovial l eukocyte counts returned to normal by day 4, PMN cell counts remained elevated through day 8; PMN cell counts for chlorhexidine-lavaged join ts were typically twice that of control joints. Chlorhexidine lavage c aused synovial ulceration, inflammation, and abundant fibrin accumulat ion. Consistent differences in proteoglycan staining were not detected between control and chlorhexidine-lavaged joints. Joint lavage with 0 .05% chlorhexidine diacetate, the lowest known bactericidal concentrat ion, is not recommended for equine joints. (C) Copyright 1994 by The A merican College of Veterinary Surgeons