EFFECT OF HIGH-MOLECULAR-WEIGHT DEXTRAN MACROMOLECULES ON LOW-FLOW ISCHEMIA AND REPERFUSION OF THE LARGE COLON IN HORSES

Objective - To evaluate the effect of high-molecular weight (MW) dextr an macromolecules on low-flow ischemia and reperfusion of the large co lon in horses. Design - Horses subjected to low-flow ischemia and repe rfusion of the large colon were treated with either 0.9 NaCl (group 1, n = 6) or high-MW dextran (group 2, n = 6) solutions. Animals - 12 ad ult horses. Procedure - Horses were subjected to 3 hours' low-flow isc hemia followed by 3 hours' reperfusion. A dose of either 0.9% NaCl or a 6% solution of high-MW (250,000) dextran (10 ml/kg of body weight) w as administered IV, 30 minutes prior to reperfusion. Hemodynamic varia bles were recorded at 30-minute intervals. Systemic arterial and colon ic 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 speci mens was performed. Results - Mean arterial pressure was greater in gr oup-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 ot her hemodynamic variables. Compared with baseline values, colonic bloo d flow was significantly lower from 0.5 to 3 hours and was significant ly 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 significan tly lower in group-2 horses, from 3 to 6 and 3 to 5 hours, respectivel y. There was significant mucosal necrosis, hemorrhage, edema, and neut rophil infiltration in horses of both groups; however, there were no s ignificant differences between the 2 groups. Conclusions - High-MW dex tran did not protect the colonic mucosa from low-flow ischemia and rep erfusion; there were no deleterious effects on colonic mucosa or on sy stemic hemodynamic or metabolic variables. Clinical Relevance-Reperfus ion with high-MW dextran solution probably would not protect the large colon from ischemia-reperfusion injury associated with large-colon vo lvulus.