Objective—To measure changes in laminar microvascular
blood flow (LMBF) over time in healthy horses
and horses in the prodromal stage of black walnutinduced
laminitis and to determine the effects of glyceryl
trinitrate application on LMBF in horses with
Animals—10 healthy adult horses.
Procedure—Laser Doppler flowmetry was used to
measure LMBF. Baseline measurements were
obtained, horses were given deionized water via a
nasogastric tube, and measurements were obtained
hourly for 12 hours. Twenty-four hours later, baseline
measurements were again obtained, and horses
were given black walnut extract. Measurements were
obtained hourly for 12 hours or until development of
Obel grade-3 laminitis. At this time, 5 horses were
treated with phenylbutazone, and the other 5 were
treated with phenylbutazone and glyceryl trinitrate,
and measurements were obtained hourly for an additional
Results—LMBF was significantly decreased 1 and 2
hours after administration of the black walnut extract
but then returned to near-baseline values for the next
6 hours. Eight hours after extract administration,
there was a second significant decrease in LMBF that
persisted until the end of the study. Glyceryl trinitrate
had no effect on LMBF. Clinical signs of laminitis
developed 8 to 12 hours after extract administration.
Conclusions and Clinical Relevance—Results suggest
that in horses with black walnut-induced laminitis,
there is an early decrease in LMBF followed by
reperfusion prior to onset of clinical signs. Treatment
with glyceryl trinitrate after development of clinical
signs of laminitis did not have a significant effect on
LMBF. (Am J Vet Res 2000;61:862–868)
Objective—To determine the effectiveness of preinduction hyperbaric oxygen treatment (HBOT) in ameliorating signs of experimentally induced endotoxemia in horses.
Animals—18 healthy adult horses.
Procedures—Horses were randomly assigned to 1 of 3 equal-sized treatment groups to receive normobaric ambient air and lipopolysaccharide (LPS), HBOT and LPS, or HBOT and physiologic saline (0.9% NaCl) solution. Horses were physically examined, and blood was obtained for a CBC and to determine concentration or activity of plasma tissue necrosis factor-α, blood lactate, and blood glucose before the horses were treated with HBOT and then intermittently for 6 hours after administration of LPS or physiologic saline solution.
Results—All LPS-treated horses developed signs and biochemical and hematologic changes consistent with endotoxemia. Treatment with HBOT significantly ameliorated the effect of LPS on clinical endotoxemia score but did not significantly improve other abnormalities associated with endotoxemia.
Conclusions and Clinical Relevance—The protective effect of HBOT was minimal, and results did not support its use as a treatment for horses prior to development of endotoxemia.
Objective—To determine effects of domperidone and acepromazine maleate on microvascular blood flow in digital laminae of clinically normal adult horses.
Animals—8 clinically normal adult horses (4 mares and 4 geldings).
Procedures—In a 4-period crossover study, domperidone was administered PO at 1.1 mg/ kg and 5.5 mg/kg and IV at 0.2 mg/kg; acepromazine was administered IV at 0.04 mg/kg. The washout period between treatments was 1 week. A 3-minute measurement of laminar microvascular blood flow (LMBF) was obtained with laser Doppler flowmetry. Baseline measurements were obtained at −2, −1, and 0 hours prior to administration of drugs. Post-treatment measurements were obtained at 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 10, and 12 hours. Percentage change from baseline values in LMBF for each treatment was subsequently calculated.
Results—Oral administration of domperidone at 1.1 mg/kg and 5.5 mg/kg significantly increased LMBF, compared with baseline values, beginning 4 hours after administration, and this effect persisted for at least 8 hours. Intravenous administration of domperidone at 0.2 mg/kg significantly increased LMBF, compared with baseline values, at 10 and 12 hours after administration. Administration of acepromazine (0.04 mg/kg, IV) significantly increased LMBF, compared with baseline values, at 3, 5, 8, and 10 hours after administration. No adverse effects of drugs were detected in any horse.
Conclusions and Clinical Relevance—Domperidone may be useful for preventing vasoconstriction and reduction in LMBF believed to occur in horses with laminitis, but additional research of the drug's effects in horses with laminitis is required.