Hydraulic occluders consist of an inflatable silicone membrane inside a polyester-reinforced stretch-resistant cuff. Inflation of the HO can be controlled percutaneously via injection of fluid into an SC injection port attached to the occluder by a length of actuating tubing (Figure 1). Chronic implantation of silicone HOs was first described in experimental models in 1969.1 More recently, clinical applications for HOs in dogs, including use as an artificial urethral sphincter2 and as a means of gradual venous occlusion for surgical treatment of adrenal gland neoplasia3 and congenital portosystemic shunts,4,5 have been reported.
Despite extensive experimental use, little information has been published regarding the precision and reliability of silicone HOs in situations requiring chronic implantation. Hydraulic occluders are individually hand assembled at present by gluing silicone sheets and tubing together in the desired size and configuration with liquid silicone. Early experiences with HOs raised concerns that manufacturing variability could lead to differences in initial lumen size and filling volumes, negatively affecting precision when planning partial occlusion or making adjustments in chronic applications. In addition, silicone acts as a semipermeable membrane, and the diffusion properties of various filling solutions may affect longterm maintenance of occlusion.6–11 To date, no standard filling solution has been evaluated for long-term maintenance of occlusion. The purposes of the present study were to evaluate different sizes of the same HO models, diffusion of various filling solutions (eg, saline [0.9% NaCl] solution, SH, and air), and maintenance of occlusion in 3 sizes of HO. Our hypotheses were that there would be considerable variation in occluder size as a result of the hand-manufacturing process, that high–molecular-weight filling solutions would undergo the least diffusion and yield the most reliable maintenance of long-term occlusion, and that air would diffuse rapidly through the HO membrane.
Simulated body fluid
DOCXS Biomedical Products and Accessories, Ukiah, Calif.
Surgilene, Davis and Geck, Wayne, NJ.
ROPAC-3.5, Access Technologies, Skokie, Ill.
Posi-Grip huber point needle, Access Technologies, Skokie, Ill.
HP Scanjet 4470 C, Hewlett-Packard Co, Palo Alto, Calif.
ImageJ 1.27Z, National Institutes of Health, Bethesda, Md.
Hylartin V, Pharmacia & Upjohn Co, Kalamazoo, Mich.
APX-203, Denver Instrument, Arvada, Colo.
T-5S-CS-UF, Access Technologies, Skokie, Ill.
Silastic, Dow Corning Corp, Midland, Mich.
PX 603-030G5V, Omega Engineering Inc, Stamford, Conn.
DP25 B-E-A, Omega Engineering Inc, Stamford, Conn.
IOX 22.214.171.124, EMKA Technologies, Falls Church, Va.
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Peacock JT, Fossum TW & Bahr AM, et al. Evaluation of gradual occlusion of the caudal vena cava in clinically normal dogs. Am J Vet Res 2003;64:1347–1353.