Laminar microvascular flow, measured by means of laser Doppler flowmetry, during the prodromal stages of black walnut-induced laminitis in horses.
OBJECTIVE
To measure changes in laminar microvascular blood flow (LMBF) over time in healthy horses and horses in the prodromal stage of black walnut-induced laminitis and to determine the effects of glyceryl trinitrate application on LMBF in horses with acute laminitis.


METHODS
10 healthy adult horses.


METHODS
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 12 hours.


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
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.
Adair
H S
HS
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville 37901-1071, USA.
Goble
D O
DO
Schmidhammer
J L
JL
Shires
G M
GM
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D001794:Blood Pressure; D001831:Body Temperature; D005534:Foot Diseases / Q000209:etiology / Q000503:physiopathology / Q000662:veterinary*; D005552:Forelimb / Q000098:blood supply*; D006339:Heart Rate; D006724:Hoof and Claw / Q000098:blood supply*; D006734:Horse Diseases / Q000209:etiology / Q000503:physiopathology*; D006736:Horses; D017078:Laser-Doppler Flowmetry / Q000662:veterinary; D005996:Nitroglycerin / Q000627:therapeutic use; D009754:Nuts / Q000009:adverse effects / Q000378:metabolism; D010653:Phenylbutazone / Q000627:therapeutic use; D011897:Random Allocation; D012716:Sesamoid Bones / Q000098:blood supply*; D014665:Vasodilator Agents / Q000627:therapeutic use
D000894:Anti-Inflammatory Agents, Non-Steroidal; D014665:Vasodilator Agents; D005996:Nitroglycerin; D010653:Phenylbutazone