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  • Author or Editor: D. V. Wilson x
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The role of platelet-activating factor in mediating the cardiovascular and peripheral cellular responses to large-colon ischemia and reperfusion, was explored in anesthetized ponies. A specific platelet-activating factor (PAF) antagonist (WEB 2086) was administered to a group of 6 ponies, and another 6 ponies (controls) were given an equivalent volume of saline solution, prior to 1 hour of large-colon torsion. After correction of the torsion, ponies were monitored during the reperfusion period. Significant (P < 0.05) hypotension and metabolic acidosis developed in all ponies after correction of colonic torsion, cardiac index increased initially, but then decreased significantly (P < 0.05) over the study period. Mean times between correction of torsion and onset of cardiac failure and death were not different between groups. Significant (P < 0.05) thrombocytopenia developed during the reperfusion period in control ponies, but not in WEB-treated ponies. Blood leukocyte concentration in control ponies was more variable and significantly (P < 0.05) decreased immediately upon reperfusion, compared with that in WEB-treated ponies. We conclude that although the cardiovascular responses to colonic ischemia and reperfusion are not prevented by use of a specific paf-antagonist, specific peripheral cellular responses are mediated by paf.

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in American Journal of Veterinary Research
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To investigate the cardiopulmonary effects of positive end-expiratory pressure (peep), values of 10, 20, and 30 cm of H2O, were applied to anesthetized, dorsally recumbent, ventilated ponies. After iv induction of general anesthesia, peep was superimposed on controlled ventilation with 100% oxygen, and changes in gas exchange and cardiac function were measured. Increasing values of peep in these ponies caused a linear increase in the mean (± SEM) functional residual capacity, from a control value (zero end-expiratory pressure) of 1.7 ± 0.24 L to 2.2 ± 0.31, 2.9 ± 0.32 and 3.4 ± 0.3 L at peep of 10, 20, and 30 cm of H2O, respectively (P < 0.05). Paralleling these changes, intrapulmonary shunt fraction decreased significantly (P < 0.05) from a control value of 12.9 ± 0.5%, to 7.5 ± 1.1 and 2.1 ± 0.6%, at peep of 20 and 30 cm of H2O, respectively. Cardiac output was decreased by increasing values of peep, from control value of 11.7 ± 1.56 L/min to 9.9 ± 1.51, 8.8 ± 1.33 and 5.62 ± 0.56 L/min at peep of 10, 20, and 30 cm of H20, respectively. Related to decreasing cardiac output, tissue oxygen delivery also decreased as peep was increased, from control value of 2.0 ± 0.09 L/min to 1.8 ± 0.07, 1.6 ± 0.06, and 1.03 ± 0.04 L/min at peep of 10, 20, and 30 cm of H2O, respectively.

Thus, the effects of increasing values of peep in these ponies included increased functional residual capacity and arterial oxygenation, but marked reduction in cardiac output, resulting in no improvement or decrease in total oxygen delivery. Although peep is useful for improving arterial oxygenation, the deleterious cardiovascular effects should be anticipated or ameliorated by use of volume loading and/or inotrope administration.

Free access
in American Journal of Veterinary Research