Spectroscopic and mechanical evaluation of thin film commonly used for banding congenital portosystemic shunts in dogs.

Objectives: To (1) determine whether different types of thin film used to occlude congenital portosystemic shunts are cellophane, and (2) evaluate the influence of saline immersion and sterilization on the tensile properties of cellophane.

Study Design: Ex vivo spectroscopic evaluation and mechanical testing.

Sample Population: Rectangular strips of thin film from 4 sources.

Methods: Samples were evaluated with Fourier Transform Infrared Spectroscopy and microscopy with a polarizing lens. Samples consistent with cellophane were divided into 5 sterilization groups: non-sterile, autoclave, gamma irradiation, hydrogen peroxide and ethylene oxide. Samples were tested while dry or after saline solution immersion. Tensile properties were compared using ANOVA, unpaired t-tests, Mann-Whitney U-tests and Fisher's exact tests. P < 0.05 was considered significant.

Results: One thin film was consistent with cellophane and it could be differentiated from the other thin films by visible striations. Cellophane was strongest when strips were oriented parallel with its fiber direction and saline immersion reduced its strength by 48% (P < .001). All sterilization methods except autoclave significantly weakened wet cellophane (ethylene oxide [P < .001], gamma irradiation [P < .001], and hydrogen peroxide [P < .001]).

Conclusions: Thin film from most sources was not consistent with cellophane. Autoclave sterilization is the best way to preserve the strength of wet cellophane.