Objective—To determine effects of sedation
achieved by xylazine (XYL) or acepromazine (ACE) on
cardiopulmonary function and uterine blood flow in
cows in late gestation.
Animals—8 cows between 219 and 241 days of gestation.
Procedure—Doses of ACE (0.02 mg/kg) or XYL (0.04
mg/kg) were administered IV. Measurements were
obtained to determine cardiopulmonary effects and
oxygen delivery to the uterus.
Results—Heart rate was not significantly affected by
administration of ACE, but it decreased markedly after
administration of XYL. Uterine artery flow was
decreased at all times by XYL and was always less
than for ACE. Xylazine increased uterine vascular
resistance through 30 minutes and caused reduced
PaO2 and increased PaCO2 at all time periods.
Acepromazine caused a 5% decrease in PaO2 only at
5 minutes. Xylazine reduced oxygen delivery by 59%
at 5 minutes and 32% at 45 minutes. In contrast, ACE
caused a nonsignificant reduction of oxygen delivery
by 16% at 15 minutes and a return to baseline values
by 45 minutes
Conclusions and Clinical Relevance—Xylazine
markedly reduces flow and availability of oxygenated
blood to the uterus, which may critically impair delivery
of oxygen to the fetus at a stressful and important time
of development or delivery. Acepromazine was associated
with slight reductions of much shorter duration.
When XYL is used to sedate pregnant cows, it could
impose physiologic distress on the fetus and potentially
increase fetal morbidity and mortality. When sedation
of the dam is desirable, ACE could be an alternative
to XYL. (Am J Vet Res 2002;63:1695–1699)
Objective—To elucidate the species and biovariants of Pasteurellaceae isolated from clinically normal bighorn sheep (Ovis canadensis) or bighorn sheep with evidence of respiratory disease.
Sample—675 Pasteurellaceae isolates from 290 free-ranging bighorn sheep in Idaho, Oregon and Wyoming.
Procedures—Nasal and oropharyngeal swab specimens were inoculated onto selective and nonselective blood agar media. Representatives of each colony type were classified via a biovariant scheme. The association of respective β-hemolytic isolates with respiratory disease was evaluated via χ2 analyses.
Results—Bacterial isolates belonged to 4 species: Histophilus somni, Mannheimia haemolytica, Pasteurella multocida, and Bibersteinia (Pasteurella) trehalosi. Within the latter 3 species, 112 subspecies, biotypes, and biovariants were identified. Bibersteinia trehalosi 2 and B trehalosi 2B constituted 345 of 675 (51%) isolates. Most (597/618 [97%]) isolates from adult sheep were from clinically normal animals, whereas most (47/57 [82%]) isolates from lambs were from animals with evidence of respiratory disease. Twenty-two Pasteurellaceae biovariants were isolated from sheep with respiratory disease; 17 of these biovariants were also isolated from clinically normal sheep. The ability of isolates to cause β-hemolysis on blood agar was associated with respiratory disease in adult bighorn sheep (OR, 2.59; 95% confidence interval, 1.10 to 6.07).
Conclusions and Clinical Relevance—Bighorn lambs appeared more susceptible to respiratory disease caused by Pasteurellaceae than did adult sheep. β-Hemolytic Pasteurellaceae isolates were more likely to be associated with respiratory disease than were non–β-hemolytic isolates in adult sheep. Identification of Pasteurellaceae with the greatest pathogenic potential will require studies to estimate the risk of disease from specific biovariants.
Objective—To examine cross-reactivity of aeroallergens
in Colorado and surrounding states by evaluating
concurrent positive reactions of related and nonrelated
allergens of intradermal tests in dogs.
Sample Population—Intradermal test results of 268
Procedure—A retrospective evaluation of skin test
results for 268 dogs was performed. Pairs of closely
related and nonrelated allergens were evaluated.
Group 1 consisted of closely related allergens with
demonstrated antibody cross-reactivity in humans. In
group 2, allergens of the same plant group (ie, trees,
grasses, or weeds) that were not closely related were
paired. In group 3, allergen pairs were of different
plant groups. Plant allergens were paired with dust
mite allergens, animal dander, or mold spores in
group 4. In the last group, allergens not derived from
plants were paired. Data were evaluated twice by use
of a different definition of a positive reaction.
Significance of the difference between group means
of log odds ratios was estimated by use of a bootstrap
percentile confidence interval.
Results—Significant differences in the number of
concurrent positive reactions were not found
between related versus nonrelated grass, weed, or
tree allergens. Significant differences in the number
of concurrent positive reactions were found between
plant allergens of different groups (ie, grasses,
weeds, and trees) and plant allergens of the same
groups, related or nonrelated , as well as between
plant-derived and nonplant-derived allergens. Many
dogs reacting to a specific allergen did not react to a
closely related allergen at the same time.
Conclusion and Clinical Relevance—These results provide evidence against
clinically relevant cross-reactivity and suggest that
allergen-specific immunotherapy should be formulated
on the basis of single allergen test results.
(Am J Vet Res 2002;63:874–879)
Objective—To assess the pharmacokinetics and pharmacodynamics of morphine in llamas.
Animals—6 healthy adult llamas.
Procedures—Llamas received morphine sulfate in a randomized crossover design. In phase 1, they received IV or IM administration of morphine at 0.05 or 0.5 mg/kg, respectively; in phase 2, they received IV administration of morphine at 0.05, 0.25, or 0.5 mg/kg. Plasma morphine and morphine-6-glucuronide concentrations were determined by validated methods. Body temperature, heart rate, respiratory rate, sedation, and analgesia were assessed and compared with plasma concentrations by regression analysis.
Results—Total body clearance was similar between IV administration of morphine sulfate at 0.25 and 0.5 mg/kg (mean ± SD, 25.3 ± 6.9 mL/min/kg and 27.3 ± 5.9 mL/min/kg, respectively), and linearity was demonstrated between these doses. Bioavailability of morphine following IM administration at 0.5 mg/kg was 120 ± 30%. Body temperature and sedation increased as the dose of morphine administered increased. Heart rate was unaffected by varying doses. Respiratory rate decreased as dose increased. Analgesia was difficult to assess as a result of high individual variability. Intravenous administration of morphine at 0.25 mg/kg provided the most consistent increase in tolerance to electric stimulation. Pharmacodynamic modeling revealed a sigmoidal relationship between plasma concentration and sedation score.
Conclusions and Clinical Relevance—Morphine was characterized by a large apparent volume of distribution and high systemic clearance in llamas. A prolonged half-life was observed with IM injection. Intravenous administration of morphine sulfate at 0.25 mg/kg every 4 hours is suggested for further study.