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  • Author or Editor: Lydia L. Donaldson x
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Abstract

Objective—To determine whether intraluminal distention and subsequent decompression of the equine jejunum affects intestinal blood flow, hemodynamics, and microvascular permeability.

Animals—5 healthy adult horses.

Procedure—Horses were anesthestized and underwent exploratory laparotomy. Two jejunal segments were identified as sham-operated or instrumented segments. After baseline values were obtained, intraluminal distention was created in the experimental segment to induce an intraluminal pressure of 18 cm H2O. After 120 minutes of distention, the intestine was decompressed for 120 minutes. Mesenteric blood flow, oxygen delivery, oxygen consumption, microvascular permeability, wet weight-to-dry weight ratio, neutrophil infiltration, and vascular resistance were determined and comparisons made among control, sham-operated, and experimental segments.

Results—Mean jejunal blood flow was 21.4 ml/min per kg. There was a significant decrease in mesenteric blood flow to the distended intestine (13.4 ml/min per kg). Blood flow increased significantly during the decompression period (340% of baseline blood flow). Intraluminal distention and subsequent decompression resulted in a significant increase in microvascular permeability, as determined by the osmotic reflection coefficient. Oxygen delivery and oxygen content decreased significantly during the distention period and increased during decompression. Morphologic evaluation revealed a significant increase in edema and neutrophil infiltration after distention and decompression, compared with results for the sham-operated or control segments.

Conclusions and Clinical Relevance—Intraluminal distention and decompression of the equine jejunum results in low-flow ischemia and edema, which may contribute to adhesions and ileus in the postoperative period after surgery for obstructions of the small intestines. (Am J Vet Res 2001;62:225–236)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate effects of Carolina rinse solution, dimethyl sulfoxide (DMSO), and 21-aminosteroid, U-74389G, on microvascular permeability and morphology of the equine jejunum after low-flow ischemia and reperfusion.

Animals—20 healthy adult horses.

Procedure—Under anesthesia, full-thickness biopsy specimens of a distal portion of the jejunum were obtained for baseline measurements. In addition to a control segment, 2 jejunal segments were identified as sham-operated or experimental segments. Experimental segments underwent 60 minutes of low-flow ischemia and 3.5 hours of reperfusion. Treatments were as follows: U-74389G (3 mg/kg, IV; 6 horses), DMSO (20 mg/kg, IV; 6) diluted in 1 L of saline (0.9% NaCl) solution, local perfusion (via jejunal artery) of Carolina rinse solution (0.5 mL/kg; 4), and local perfusion of lactated Ringer's solution (0.5 mL/kg; 4).

Results—Jejunal microvascular permeability was significantly lower after treatment with Carolina rinse solution or DMSO, compared with U-74389G or lactated Ringer's solution treatments. After DMSO treatment, serosal- and submucosal-layer edema was significantly increased in experimental segments, compared with control or sham-operated segments; however, edema increases were significantly less than for lactated Ringer's solution or U-74389G treatments. Significant decreases in intestinal wet weight-to-dry weight ratio were found following Carolina rinse solution or DMSO treatments, compared with lactated Ringer's solution or U-74389G treatments. Edema formation and leukocyte infiltration in jejunal segments of horses treated with lactated Ringer's solution or U-74389G were increased, compared with Carolina rinse solution or DMSO treatments.

Conclusions and Clinical Relevance—Carolina rinse solution and DMSO may be protective against ischemia-reperfusion injury in the equine jejunum. (Am J Vet Res 2005;66:525–536)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To assess changes in systemic hydration, concentrations of electrolytes in plasma, hydration of colonic contents and feces, and gastrointestinal transit in horses treated with IV fluid therapy or enteral administration of magnesium sulfate (MgSO4), sodium sulfate (NaSO4), water, or a balanced electrolyte solution.

Animals—7 horses with fistulas in the right dorsal colon (RDC).

Procedure—In a crossover design, horses alternately received 1 of 6 treatments: no treatment (control); IV fluid therapy with lactated Ringer's solution; or enteral administration of MgSO4, Na2SO4, water, or a balanced electrolyte solution via nasogastric intubation. Physical examinations were performed and samples of blood, RDC contents, and feces were collected every 6 hours during the 48 hour-observation period. Horses were muzzled for the initial 24 hours but had access to water ad libitum. Horses had access to hay, salt, and water ad libitum for the last 24 hours.

Results—Enteral administration of a balanced electrolyte solution and Na2SO4 were the best treatments for promoting hydration of RDC contents, followed by water. Sodium sulfate was the best treatment for promoting fecal hydration, followed by MgSO4 and the balanced electrolyte solution. Sodium sulfate caused hypocalcemia and hypernatremia, and water caused hyponatremia.

Conclusions and Clinical Relevance—Enteral administration of a balanced electrolyte solution promoted hydration of RDC contents and may be useful in horses with large colon impactions. Enteral administration of either Na2SO4 or water may promote hydration of RDC contents but can cause severe electrolyte imbalances. (Am J Vet Res 2004;65:695–704)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects on anal pressure of horses after local injection of the external anal sphincter with Clostridium botulinum toxin type B.

Animals—11 healthy adult horses.

Procedure—Peak and resting anal sphincter pressures were measured with a custom-made rectal probe that was connected to a pressure transducer. Pressures were measured before treatment and after injection with botulinum toxin type B (BTB) or saline (0.9% NaCl) solution. Dose titration with 500, 1,000, 1,500, and 2,500 U of BTB was completed. Physical changes, behavior, and anal pressure were recorded for each horse.

Results—Injection of 1,000 U of BTB caused a significant reduction in peak anal pressure from days 2 to 84, compared with pressure in control horses. Maximal effect of the toxin was observed within the first 15 days after injection, followed by a slow return to baseline during the 168-day period. Injection of 2,500 U of BTB in the anal sphincter in 1 horse resulted in lethargy, generalized weakness, and dysphagia for 14 days. Adverse clinical effects were not observed in horses after injections with 500, 1,000, or 1,500 U of BTB.

Conclusions and Clinical Relevance—The effect of focal intramuscular injection of BTB in horses is similar to that reported for other species. However, horses appear to be more sensitive to BTB, compared with other species, and clinical signs of botulism may develop at doses exceeding 1,500 U. Injections of BTB in the external anal sphincter of mares may be useful to reduce incisional dehiscence after repair of perineal lacerations. ( Am J Vet Res 2004;65:26–30)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether antibodies against Sarcocystis neurona could be detected in CSF from clinically normal neonatal (2 to 7 days old) and young (2 to 3 months old) foals.

Design—Prospective study.

Animals—15 clinically normal neonatal Thoroughbred foals.

Procedure—Serum and CSF samples were obtained from foals at 2 to 7 days of age and tested for antibodies against S neurona by means of western blotting. Serum samples from the mares were also tested for antibodies against S neurona. Additional CSF and blood samples were obtained from 5 foals between 13 and 41 days after birth and between 62 and 90 days after birth.

Results—Antibodies against S neurona were detected in serum from 13 mares and their foals; antibodies against S neurona were detected in CSF from 12 of these 13 foals. Degree of immunoreactivity in serum and CSF decreased over time, and antibodies against S neurona were no longer detected in CSF from 2 foals 83 and 84 days after birth. However, antibodies could still be detected in CSF from the other 3 foals between 62 and 90 days after birth.

Conclusions and Clinical Relevance—Results indicate that antibodies against S neurona can be detected in CSF from clinically normal neonatal (2 to 7 days old) foals born to seropositive mares. This suggests that western blotting of CSF cannot be reliably used to diagnose equine protozoal myeloencephalitis in foals < 3 months of age born to seropositive mares. (J Am Vet Med Assoc 2002;220:208–211)

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE To evaluate agreement among diplomates of the American College of Veterinary Anesthesia and Analgesia for scores determined by use of a simple descriptive scale (SDS) or a composite grading scale (CGS) for quality of recovery of horses from anesthesia and to investigate use of 3-axis accelerometry (3AA) for objective evaluation of recovery.

ANIMALS 12 healthy adult horses.

PROCEDURES Horses were fitted with a 3AA device and then were anesthetized. Eight diplomates evaluated recovery by use of an SDS, and 7 other diplomates evaluated recovery by use of a CGS. Agreement was tested with κ and AC1 statistics for the SDS and an ANOVA for the CGS. A library of mathematical models was used to map 3AA data against CGS scores.

RESULTS Agreement among diplomates using the SDS was slight (κ = 0.19; AC1 = 0.22). The CGS scores differed significantly among diplomates. Best fit of 3AA data against CGS scores yielded the following equation: RS = 9.998 × SG0.633 × ∑UG0.174, where RS is a horse's recovery score determined with 3AA, SG is acceleration of the successful attempt to stand, and ∑UG is the sum of accelerations of unsuccessful attempts to stand.

CONCLUSIONS AND CLINICAL RELEVANCE Subjective scoring of recovery of horses from anesthesia resulted in poor agreement among diplomates. Subjective scoring may lead to differences in conclusions about recovery quality; thus, there is a need for an objective scoring method. The 3AA system removed subjective bias in evaluations of recovery of horses and warrants further study.

Full access
in American Journal of Veterinary Research