Evaluation of the Characteristics of Venous Occlusion After Placement of an Ameroid Constrictor in Dogs

Abstract

A similar pattern of venous occlusion may occur after placement of an AC on a portosystemic shunt, which may lead to both short- and long-term complications associated with portal hypertension.

Changes in chemical and ultrastructural composition of ameroid constrictors following in vitro expansion

“…Previous studies have hypothesised that the presence of formaldehyde may have a role as a trigger for perivascular inflammation and intravascular thrombosis. [ 7 – 9 , 18 ] One previous study has identified a possible formaldehyde signature ion CH 3 O + at m / z 31, using ToF-SIMS analysis, [ 19 ] which was indeed detected in this study. Formaldehyde has a very simple, small and volatile chemistry (CH 2 O) and as such is often very hard to definitively identify, and due to the fragmentation process of ToF-SIMS other organic species may generate this ion.…”

“…[ 23 , 24 ] Possible sequelae of these issues of biocompatibility include protein adsorption, phagocytosis activation, platelet activation and clotting cascade activation, all of which have been noted in histological studies following implantation in vivo . [ 7 – 9 , 18 ] Our study has demonstrated variations that occur in both the surface chemistry and topography over the course of plasma immersion, which will affect the biomaterial-host interface. Although our study has failed to identify a compound responsible for an inflammatory trigger, it is likely that the change in the surface topography and chemistry affects the inherent biocompatibility of the ARC resulting in the changes observed histologically post-implantation.…”

“…However, in vivo studies following ARC placements around peripheral veins have shown that flow through the shunt is usually halted before expected due to external compression alone, and the same studies have shown that perivascular inflammation (characterised by neutrophilic, histiocytic and lymphocytic infiltrates) and fibrosis, as well as intravascular thrombosis provide a significant contribution to attenuation of the vessel lumen. [ 7 – 10 ]…”

“…However, the presence and amount of formaldehyde present in ARCs commercially available for use in portosystemic shunt surgery is not known. [ 7 – 9 ]…”

Evaluation of ameroid ring constrictors for treatment for single extrahepatic portosystemic shunts in dogs: 168 cases (1995–2001)

“…After placement of the ARC around a blood vessel, the expansion of ameroid within the stainless steel cylinder, fibrous tissue reaction to the ARC, and thrombosis result in occlusion of the vessel. 17 The purposes of this study were to report shortand long-term clinical outcomes in a series of dogs treated with an ARC for a single extrahepatic PSS and to identify factors associated with postoperative death and persistent portosystemic shunting. We hypothesized that perioperative factors could be used to predict postoperative death and continued portosystemic shunting in dogs with single extrahepatic PSSs treated by ARC placement.…”