BackgroundLower 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/ObjectivesTo compare effects of 1 low and 1 high molecular weight and molar substitution HES solution on cardiovascular variables, COP, and hemostasis in normal horses.AnimalsEight healthy adult horses.MethodsRandomized, 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).ResultsCentral 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 ImportanceBoth 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.

Summary Granulosa cell tumour (GCT) is reported to be the most common ovarian neoplasm in the mare. A multicentre retrospective study evaluating the medical records of horses undergoing ovariectomy for treatment of a GCT was undertaken, documenting the presenting clinicopathological features, treatment and outcome. Follow‐up information was obtained by telephone questionnaire. Fifty‐two mares were included. Most presented with behavioural/reproductive abnormalities, including stallion‐like behaviour (50%), aggression (31%), prolonged oestrus or nymphomania (19%), and persistent anoestrus (8%). Most (93%) affected ovaries had a multilocular appearance when examined ultrasonographically. Only 60% of horses with histopathologically confirmed GCTs demonstrated elevations in serum inhibin concentrations. Twenty‐five percent of horses had histopathologically confirmed bilateral GCTs. Ninety‐four percent of horses that underwent ovariectomy were discharged from the hospital. Standing laparoscopic ovariectomies had a lower complication rate (34%) than other surgical methods. Long‐term complications were uncommon (11%). In conclusion, histopathologically confirmed GCTs can occur in the presence of normal serum inhibin concentrations. The high prevalence of bilateral GCTs indicates that thorough evaluation of the contralateral ovary is necessary. Surgical ovariectomy for treatment of GCTs has favourable short‐ and long‐term outcomes. Standing laparoscopic ovariectomy may be associated with a lower complication rate than other surgical methods.

Nuchal bursitis can be successfully managed with either medical or surgical treatment. Prognosis for return to work tends to be worse in horses requiring surgical intervention following failed medical management.

ESIGL was more prevalent in this population of horses evaluated for acute abdominal pain than in previous studies, accounting for 10.7% of all horses with strangulating small intestinal lesions. Geldings and Quarter Horse or Quarter Horse related breeds are predisposed to this condition. The prognosis for survival to hospital discharge was fair to good.

A lower molecular weight and molar substitution formulation (130/0.4) of hydroxyethyl starch solution has been shown to have a more sustained effect on COP and similar hemodynamic effects as a higher molecular weight and molar substitution formulation (600/0.75) in healthy horses. In humans, these pharmacodynamic characteristics are coupled with more rapid clearance and decreased adverse coagulation effects and accumulation. The objective of this study was to determine and compare the pharmacokinetics of these two formulations in horses. Eight healthy horses were given a 10 mL/kg bolus of each formulation (600/0.75 and 130/0.4) of hydroxyethyl starch solution in a randomized crossover design. Blood was collected, and plasma was harvested for plasma levels over 24 h. Pharmacokinetic parameters for each horse were estimated from a noncompartmental analysis. Treatment with 600/0.75 resulted in a higher initial plasma concentration (C ), systemic half-life (t ), and overall drug exposure (AUC ) in addition to decreased elimination rate (β), volume of distribution (Vd), and clearance (CL), compared to treatment with 130/0.4 (P < 0.001). The pharmacokinetic findings combined with previous pharmacodynamics findings suggest that 130/0.4 can provide similar benefits to 600/0.75 with a lower risk of accumulation in the circulation.