Effects of heparin treatment on colonic torsion-associated hemodynamic and plasma eicosanoid changes in anesthetized ponies

P. J. Provost From the Departments of Large Animal Clinical Sciences (Provost, Stick, Robinson), Small Animal Clinical Science (Hauptman), Pathology (Patterson), Pharmacology (Roth), and Physiology (Robinson), Michigan State University, East Lansing, MI 48824-1314.

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J. A. Stick From the Departments of Large Animal Clinical Sciences (Provost, Stick, Robinson), Small Animal Clinical Science (Hauptman), Pathology (Patterson), Pharmacology (Roth), and Physiology (Robinson), Michigan State University, East Lansing, MI 48824-1314.

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J. S. Patterson From the Departments of Large Animal Clinical Sciences (Provost, Stick, Robinson), Small Animal Clinical Science (Hauptman), Pathology (Patterson), Pharmacology (Roth), and Physiology (Robinson), Michigan State University, East Lansing, MI 48824-1314.

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J. G. Hauptman From the Departments of Large Animal Clinical Sciences (Provost, Stick, Robinson), Small Animal Clinical Science (Hauptman), Pathology (Patterson), Pharmacology (Roth), and Physiology (Robinson), Michigan State University, East Lansing, MI 48824-1314.

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N. E. Robinson From the Departments of Large Animal Clinical Sciences (Provost, Stick, Robinson), Small Animal Clinical Science (Hauptman), Pathology (Patterson), Pharmacology (Roth), and Physiology (Robinson), Michigan State University, East Lansing, MI 48824-1314.

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R. Roth From the Departments of Large Animal Clinical Sciences (Provost, Stick, Robinson), Small Animal Clinical Science (Hauptman), Pathology (Patterson), Pharmacology (Roth), and Physiology (Robinson), Michigan State University, East Lansing, MI 48824-1314.

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SUMMARY

Large colon torsion frequently is a fatal condition in horses. The purpose of the study reported here was to determine systemic arterial pressure, plasma eicosanoid concentrations, colonic blood flow, vascular resistance, tissue pH, and morphologic features associated with large colon torsion and detorsion, and to evaluate the effects of sodium heparin (80 IU/kg of body weight, iv) treatment on these values. Values were determined in 20 anesthetized ponies that were randomly assigned into 4 equal groups: control; control/heparin; torsion; torsion/heparin. Torsions were created by a 720° rotation of the cecum and colon around their long axes at the sternal and diaphragmatic flexures. After 1 hour of torsion, the torsion was corrected and the colon was allowed to reperfuse for 1 hour. Heparin was administered 30 minutes into the experiment. Parametric data were analyzed (P ≤ 0.05), using split-plot analysis of variance, with differences between means evaluated with a modified Bonferroni t test; histopathologic data were analyzed (P ≤ 0.05) with a Kruskal-Wallis one-way analysis of variance by ranks. Heparin prevented colonic detorsion-induced hypotension and increases in vascular resistance and thromboxane concentration, and it significantly increased colonic blood flow for 40 minutes during reperfusion. Heparin did not alter prostacyclin concentration or the histologic appearance of the large colon.

SUMMARY

Large colon torsion frequently is a fatal condition in horses. The purpose of the study reported here was to determine systemic arterial pressure, plasma eicosanoid concentrations, colonic blood flow, vascular resistance, tissue pH, and morphologic features associated with large colon torsion and detorsion, and to evaluate the effects of sodium heparin (80 IU/kg of body weight, iv) treatment on these values. Values were determined in 20 anesthetized ponies that were randomly assigned into 4 equal groups: control; control/heparin; torsion; torsion/heparin. Torsions were created by a 720° rotation of the cecum and colon around their long axes at the sternal and diaphragmatic flexures. After 1 hour of torsion, the torsion was corrected and the colon was allowed to reperfuse for 1 hour. Heparin was administered 30 minutes into the experiment. Parametric data were analyzed (P ≤ 0.05), using split-plot analysis of variance, with differences between means evaluated with a modified Bonferroni t test; histopathologic data were analyzed (P ≤ 0.05) with a Kruskal-Wallis one-way analysis of variance by ranks. Heparin prevented colonic detorsion-induced hypotension and increases in vascular resistance and thromboxane concentration, and it significantly increased colonic blood flow for 40 minutes during reperfusion. Heparin did not alter prostacyclin concentration or the histologic appearance of the large colon.

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