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[Venous catheters in horses - early ultrasonographic venous abnormalities and evidence of biofilms].

OBJECTIVE
Complications associated with indwelling intravenous catheters vary from minor to severe. Changes in tissue architecture and vein structure may be detectable prior to clinical alterations. The aim of the study was to characterize and compare changes in a catheterized vein and surrounding tissue by clinical and ultrasonographic examination. Microbiological infestation of catheter specimens was assessed.


MATERIAL AND METHODS
In this prospective, observational, clinical study 55 horses with an indwelling intravenous catheter have been included. Subsequent to catheter placement, vein and surrounding tissue were daily examined clinically and by ultrasonographic examination at predetermined localizations. After sterile removal of the catheters, specimens underwent microbiological testing and scanning electron microscopy. Obtained data were analyzed via descriptive statistics. Thickness of the venous wall was compared at predetermined localizations and time points for several parameters with the help of non-parametric tests (level of significance at p < 0.05, post-hoc Bonferroni correction).


RESULTS
Overall, in 41.8 % of the horses transient alterations (swelling) of the surrounding tissue occurred during catheterization. Median catheterization was 69.5 hours (19 hour-10 days). With ultrasonography, venous valves and collateral vessels could be detected reliably. Significant alterations in wall thickness during catheterization were associated with various factors (location site [p ≤ 0.001], season [p = 0.006], anesthesia [p ≤ 0.001]).Microbiological analysis revealed a positive result in 23.5 %, 12 of the 51 samples; raster electron microscopy showed presence of bacteria in 25.0 %, 4 of the 16 investigated catheter samples.


CONCLUSION AND CLINICAL RELEVANCE
Local tissue changes at the insertion site of the catheter are commonly associated with catheterization, and are easily detectable with ultrasonography. Despite the easy performance in a clinical setting, the benefit of routine ultrasonographic monitoring of catheterized veins might be questionable with regard to early identification and prediction of catheter-associated venous disease. Bacteria might be detectable morphologically on the catheter but frequently lack a positive result from standard bacterial cultivation.