Portosystemic shunts are common hepatic vascular anomalies in small animal patients.1–3 Medical management of PSSs has been associated with chronic hepatic fibrosis and portal hypertension, which can result in progressive hepatic failure, as well as clinical signs of persistent or progressive neurologic and urinary tract abnormalities.4–7 The long-term prognosis is generally more favorable following treatment with gradual surgical attenuation of a PSS, compared with that following medical management, provided the patient survives the immediate postoperative period.6–10
Various methods have been used for PSS attenuation including silk ligatures,11 intravascular thrombogenic coils,11,12 hydraulic occluders,4,13 cellophane banding,8,11,14 and ameroid constrictors.2,15,16 Among those devices, ameroid constrictors have gained popularity because they gradually occlude the PSS, provide predictable closure, and are associated with low surgical and postoperative complications.1,15,16 Ameroid is a hygroscopic, compressed casein that undergoes expansion when immersed in fluid, which is characterized by rapid expansion initially followed by a period of slower expansion.1,15,17
Investigators of a retrospective study14 that involved 106 dogs and 5 cats with congenital PSSs in which the shunt was surgically attenuated by use of a cellophane band suggest that the initial constriction of the PSS should not be < 2.0 to 3.0 mm. Because scientifically sound recommendations regarding the appropriate size of ameroid constrictor for use in attenuation of PSSs with particular diameters are lacking, the decision of which size of constrictor to use for attenuation of each PSS is subjective. Surgeons may handle ameroid constrictors of multiple sizes before choosing which size of constrictor to use during a PSS attenuation procedure. Consequently, for the purpose of frugality and because the manufacturer does not advise against multiple sterilizations, unused ameroid constrictors are frequently resterilized after surgical procedures. The casein material in ameroid constrictors is a type of protein. In 1 study,18 the use of heat to sterilize micellar casein concentrates caused proteolysis and protein dissociation. Thus, resterilization of ameroid constrictors could cause denaturation of the casein material and increase its permeability, which could affect the rate of closure of the constrictors when used for PSS attenuation.
The objective of the study reported here was to evaluate the lumen area of ameroid constrictors after ≥ 1 HPGP sterilization procedure. Our hypothesis was that the number of times that an ameroid constrictor undergoes HPGP sterilization would have no effect on its final lumen area.
Hydrogen peroxide gas plasma
Ameroid constrictor, Research Instruments NW, Lebanon, Ore.
VHP MD140X biodecontamination unit, STERIS Corp, Mentor, Ohio.
VITROS 5,1 FS, Ortho Clinical Diagnostics Inc, Rochester, NY.
Chocolate agar plate, Remel Inc, Lenexa, Kan.
Class II Type A/B3 biological safety cabinet, NuAire, Plymouth, Minn.
IR Autoflow CO2 water jacketed incubator, NuAire, Plymouth, Minn.
Microsoft Excel, version 14.06129.5000, Microsoft Corp, Redmond, Wash.
Olympus Tough TG-820 12-megapixel digital camera, Olympus Corporation of the Americas, Tokyo, Japan.
NIH Image J, National Institutes of Health, Bethesda, Md. Available at: rsb.info.nih.gov/nih-image. Accessed Nov 1, 2013.
STATA SE, version 12.1, StataCorp, College Station, Tex.
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