Biomechanical and Microbiological Analysis of Canine Cadavers Fixed With Ethyl Alcohol Formaldehyde Mixtures for Anatomy and Surgery Education

Abstract

In Brazil, with the creation of the Arouca Law in 2009 and the need for substitutes for live animals in studies, it is essential to apply anatomical techniques to conserve corpses. Fixative substances prevent autolysis, facilitate incisions and make the protein fraction of the tissue insoluble, preserving its morphology due to antiseptic properties. Preservative solutions aim to maintain anatomical specimens intact to allow the long-lasting use of them. Several techniques can promote such fixation and preservation, but formaldehyde is the most used in many countries. This research aims to determine the viability of a new anatomical technique using ethyl alcohol (EA) and formaldehyde, in different proportions, to fix canine cadavers and sodium chloride aqueous solution (SCAS 30%) for preservation biomechanical and microbiological analyses. Fresh samples were collected before fixation to be the control samples in every group. Corpses were divided into four groups: G1 (only formaldehyde), G2 (30% formaldehyde and 70% EA), G3 (70% formaldehyde and 30% EA) and G4 (50% formaldehyde and 50% EA) and were subsequently conserved in 30% SCAS. Analyses were done at D0 (before fixation), D30, D60, D90 and D120 after preservation on 30% SCAS. Biomechanical traction tests were performed on skin and jejunum samples at all times of fixation and preservation. Microbiological analyses of the solution were at the end of fixation and during all preservation moments. The control samples (fresh corpses) were compared to the other four groups with the T-test. There was no statistical difference in the maximum rupture force (MRF) of the skin and jejunum between the control and the fixation and preservation moments. It was observed that G2 and G3 presented minor variations in the MRF with means of skin (−14.2 N) and jejunum (−0.28 N). There were significant differences at all times for rupture elongation (RE) of the skin and jejunum. G3 and G4 showed minor variations in the RE, with a difference between the skin (1.32 mm) and jejunum (0.23 mm). The microbiological analyses of the SCAS 30% did not show any contamination (aerobic and anaerobic microorganisms) for Groups 1, 2 and 3. For D120 of G4, Bacillus spp. was identified in the amount of 1.0 × 10.