Cardiovascular, Colloid Osmotic Pressure, and Hemostatic Effects of 2 Formulations of Hydroxyethyl Starch in Healthy Horses

Background Lower molecular weight and molar substitution formulations of hydroxyethyl starch ( HES ) solutions might maximize cardiovascular function and colloid osmotic pressure ( COP ) and minimize adverse effects on coagulation. Hypothesis/Objectives To compare effects of 1 low and 1 high molecular weight and molar substitution HES solution on cardiovascular variables, COP , and hemostasis in normal horses. Animals Eight healthy adult horses. Methods Randomized, crossover designed study: 10 mL/kg bolus of 6% HES (600/0.75) (hetastarch) ( HS ), 6% HES (130/0.4) tetrastarch ( TS ), and 0.9% NaCl ( NS ). Variables recorded included central venous pressure ( CVP ), noninvasive arterial blood pressure, packed cell volume ( PCV ), COP , and automated platelet analysis ( CT ). Results Central venous pressure was increased for 8 hours after all treatment (baseline = 8.4 ± 3.8; 8 hours = 10.3 ± 3.5 cm H 2 O; P  < .001). HS and TS produced an increase in systolic arterial pressure ( HS = 109.1 ± 11.9; TS = 109.5 ± 10.9 mmHg) and mean arterial pressure ( HS = 80.4 ± 13.0; TS = 82.3 ± 10.1 mmHg) compared to NS ( SAP = 103.2 ± 13.2 [ P  = .023]; MAP = 74.2 ± 11.4 mmHg [ P  = .048]). PCV decreased transiently with HS (baseline = 37.1 ± 4.4%; 1.5 hours = 31.6 ± 3.9%) and TS (baseline = 38.4 ± 3.9%; 1.5 hours = 32.2 ± 3.3%), but not NS ( P  = .007). COP was greater with HS (1 hour; 24.0 ± 2.1 mmHg) and TS (8 hours; 25.9 ± 2.1 mmHg) than NS (1 hour = 20.8 ± 2.6; 8 hours = 22.9 ± 3.1 mmHg; P  < .001). CT was greater at 8 ( HS = 178.6 ± 36.9; TS = 121.9 ± 33.3; NS = 108.3 ± 23.6 seconds) and 24 hours ( HS = 174.2 ± 41.7; TS = 100.8 ± 26.0; NS = 118.7 ± 38.7 seconds; P  < .001) in horses receiving HS than TS or NS . Conclusion and Clinical Importance Both TS and HS resulted in more effective volume expansion and arterial pressure support than NS . TS produced a more sustained effect on COP with shorter duration of adverse effects on platelet function than HS .