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 H₂O; 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.