Defining the role of a tailored luminal solution for small bowel preservation.

The mucosal layer is the initial site of small bowel (SB) graft injury sustained during cold storage. Vascular administration of preservation solutions alone is unable to prevent ischemic injury of this layer during clinically relevant storage periods. The SB is unique in that it possesses both a vascular and a luminal route by which preservation solutions can be administered. We hypothesized that addition of a luminal-delivered solution, formulated on amino acid requirements for energy- and non-energy-related reactions, would provide site-specific preservation of mucosal energetics, barrier function and morphology throughout an extended period of cold storage. Of the three luminal solutions containing amino acids which were tested (UWG, AA1, AA2), only the two groups (AA1, AA2), containing glutamine plus 18 other amino acids, +/- osmotic agent (lactobionate) and buffer (BES), exhibited significant improvements in energetics, barrier function, and histology compared to the clinical standard of isolated vascular University of Wisconsin (UW) solution. Although the AA1 and AA2 groups preserved barrier function and morphology up to 24h better than all other solutions tested, AA2 proved to be the only luminal solution with values of permeability, conductance, and short-circuit current not significantly different from freshly isolated tissues. Furthermore, the greatest reduction in histologic injury was effected by AA2 treatment (median grade 2 compared to control, UW(v), grade 8). This study documents that a luminal-delivered solution, formulated on physiologic SB requirements, provides targeted preservation of the SB mucosa.