Effect of high-molecular weight dextran macromolecules on low-flow ischemia and reperfusion of the large colon in horses

Abstract

Abstract Objective To evaluate the effect of high-molecular weight (MW) dextran macromolecules on low-flow ischemia and reperfusion of the large colon in horses. Design Horses subjected to low-flow ischemia and reperfusion of the large colon were treated with either 0.9 NaCI (group 1, n = 6) or high-MW dextran (group 2, n = 6) solutions. Animals 12 adult horses. Procedure Horses were subjected to 3 hours' low-flow ischemia followed by 3 hours' reperfusion. A dose of either 0.9% NaCI or a 6% solution of high-MW (250,000) dextran (10 ml/kg of body weight) was administered IV, 30 minutes prior to reperfusion. Hemodynamic variables were recorded at 30-minute intervals. Systemic arterial and colonic venous blood were collected for determination of PCV, plasma total protein, and whole blood lactate concentrations, and for blood gas and oximetry analyses. Histologic examination of large-colon biopsy specimens was performed. Results Mean arterial pressure was greater in group-2 horses, compared with group-1 horses, from 3 to 3.25 hours, but there were no significant differences between groups for any of the other hemodynamic variables. Compared with baseline values, colonic blood flow was significantly lower from 0.5 to 3 hours and was significantly greater from 3.25 to 6 hours. Arterial and colonic venous PCV were significantly lower than baseline values from 3 to 3.25 hours, and at 3 hours, respectively, in group-2 horses. These values were significantly lower in group-2 horses, from 3 to 6 and 3 to 5 hours, respectively. There was significant mucosal necrosis, hemorrhage, edema, and neutrophil infiltration in horses of both groups; however, there were no significant differences between the 2 groups. Conclusions High-MW dextran did not protect the colonic mucosa from low-flow ischemia and reperfusion; there were no deleterious effects on colonic mucosa or on systemic hemodynamic or metabolic variables. Clinical Relevance Reperfusion with high-MW dextran solution probably would not protect the large colon from ischemia-reperfusion injury associated with large-colon volvulus. (Am J Vet Res 1996;57:1067–1073)