SYSTEMIC AND COLONIC VENOUS PLASMA BIOCHEMICAL-ALTERATIONS IN HORSES DURING LOW-FLOW ISCHEMIA AND REPERFUSION OF THE LARGE COLON

The purpose of this study was to determine the effects of low-flow isc hemia and reperfusion (I-R) of the large colon on 16 systemic venous ( SV) and colonic venous (CV) plasma biochemical variables in horses. Ho rses (rt = 24) were randomly allocated to 3 groups: sham-operated (n = 6), 6 h ischemia (It = 9), and 3 h ischemia followed by 3 h reperfusi on (n = 9). SV and CV heparinized blood was collected at 0, 1, 3, 3.25 , 4, and 6 h. The SV-CV difference was calculated for each variable. T he SV, CV, and SV-CV difference for albumin, total protein, and calciu m decreased significantly (P < 0.05) across time in horses of all grou ps, but there were no differences among groups. SV phosphorous was sig nificantly increased from baseline (BL) at 1 to 6 h in horses of all g roups, but there were no differences among groups. CV phosphorous was significantly greater than BL from 1 to 6 h in group-2 horses and from 1 to 3 h in group-3 horses. SV potassium was not different among grou ps, but was significantly higher at 6 h, compared with BL in horses of all groups. CV potassium was significantly greater than BL from 1 to 6 h in horses of groups 2 and 3. SV glucose was greater at 6 h compare d with all previous times in horses of all groups, but there were no d ifference among groups. CV glucose was significantly lower than BL and group-1 values in horses of groups 2 and 3 during ischemia, but retur ned to BL during reperfusion in group-3 horses. CV anion gap was signi ficantly greater and SV-CV anion gap was significantly more negative i n horses of groups 2 and 3, compared with group-1 horses during ischem ia. The biologic relevance of these alterations is unknown, but they m ay contribute to histopathologic, hemodynamic, and metabolic alteratio ns characteristic of low-flow I-R. Alternatively, these alterations ma y simply reflect colonic injury sustained during I-R. Results suggest that the colon utilizes glucose as a fuel and generates acid anions du ring low-flow ischemia. Increased CV phosphorous and potassium during I-R likely occurs as a result of leakage of intracellular stores subse quent to cellular damage.