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Abstract

Objective—To examine the effects of an aerosolized β2-adrenoreceptor agonist, albuterol, on performance during a standardized incremental exercise test in clinically normal horses.

Animals—8 Standardbred pacing mares.

Procedure—Clinically normal horses, as judged by use of physical examination, hematologic findings, serum biochemical analysis, and airway endoscopy, were randomly assigned to 2 groups and were given 900 µg of albuterol via a metered-dose inhaler 30 minutes before beginning a standardized incremental exercise test in a crossover design with a 7-day minimum washout. Further examination included measurement of baseline lung mechanics, response to histamine bronchoprovocation, and bronchoalveolar lavage.

Results—No significant differences (albuterol vs placebo) were seen for any incremental exercise test variables (ie, maximum oxygen consumption, maximum carbon dioxide consumption, respiratory quotient, treadmill speed at heart rate of 200 beats/min, or number of steps completed during an incremental exercise protocol). Mast cell percentage was significantly (r = –0.84) associated with the concentration of aerosolized histamine that evoked a 100% increase in total respiratory system resistance. No other direct correlations between bronchoalveolar lavage fluid cell types and any indices of exercise capacity or airway reactivity were found.

Conclusions and Clinical Relevance—Although no horse had exercise intolerance, 4 horses had airway hyperreactivity with bronchoalveolar lavage fluid mastocytosis; these horses may have been subclinically affected with inflammatory airway disease. In our study, albuterol did not enhance performance in 8 clinically normal racing-fit Standardbreds. (Am J Vet Res 2001;62:1812–1817)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate effects of sedation on stability of resistance of the respiratory system (RRS) and measures of resting energy expenditure (REE) by use of open-flow indirect calorimetry (IC) and treatment with aerosolized albuterol on REE in horses with recurrent airway obstruction (RAO).

Animals—9 clinically normal horses and 8 horses with RAO.

Procedure—In phase 1, RRS was measured by using forced oscillometry (FOT) in 5 clinically normal horses before and after sedation with xylazine. In phase 2, REE was measured in 4 clinically normal horses between 20 and 25 minutes and again 35 to 40 minutes after sedation with xylazine. In phase 3, IC was performed between 20 and 25 minutes and FOT was performed between 30 and 35 minutes after xylazine administration in 8 horses with RAO; after administration of 450 µg of albuterol, IC and FOT were repeated.

Results—In phase 1, RRS values were significantly lower 5 and 10 minutes after sedation. In phase 2, diminishing sedation did not significantly affect REE. In phase 3, there was a significant decrease in mean RRS (1.15 ± 0.25 vs 0.84 ± 0.14 cm H20/L/s) and REE (30.68 ± 17.89 vs 27.46 ± 16.54 kcal/kg/d) after albuterol administration.

Conclusions and Clinical Relevance—FOT and IC are useful in obtaining repeatable measurements of RRS and REE, respectively, in sedated horses. Concurrent bronchodilation and decreased REE after albuterol administration suggest that increased work of breathing as a result of airway obstruction may contribute to increased energy demands in horses with RAO. (Am J Vet Res2003;64:235–242)

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in American Journal of Veterinary Research

Abstract

OBJECTIVE To compare effectiveness of glycerol, dimethyl sulfoxide (DMSO), and hydroxyethyl starch (HES) solutions for cryopreservation of avian RBCs.

SAMPLE RBCs from 12 healthy Ameraucana hens (Gallus gallus domesticus).

PROCEDURES RBCs were stored in 20% (wt/vol) glycerol, 10% (wt/vol) DMSO freezing medium, or various concentrations of HES solution (7.5%, 11.5%, and 20% [wt/vol]) and frozen for 2 months in liquid nitrogen. Cells were then thawed and evaluated by use of cell recovery and saline stability tests, cell staining (7-aminoactinomycin D and annexin V) and flow cytometry, and scanning electron microscopy.

RESULTS Percentage of RBCs recovered was highest for 20% glycerol solution (mean ± SE, 99.71 ± 0.04%) and did not differ significantly from the value for 7.5% HES solution (99.57 ± 0.04%). Mean saline stability of RBCs was highest for 10% DMSO (96.11 ± 0.25%) and did not differ significantly from the value for 20% HES solution (95.74 ± 0.25%). Percentages of cells with 7-aminoactinomycin D staining but without annexin V staining (indicating necrosis or late apoptosis) were lowest for 10% DMSO freezing medium (3%) and 20% glycerol solution (1%) and highest for all HES concentrations (60% to 80%). Scanning electron microscopy revealed severe membrane changes in RBCs cryopreserved in 20% HES solution, compared with membrane appearance in freshly harvested RBCs and RBCs cryopreserved in 10% DMSO freezing medium.

CONCLUSIONS AND CLINICAL RELEVANCE Cryopreservation of avian RBCs with HES solution, regardless of HES concentration, resulted in greater degrees of apoptosis and cell death than did cryopreservation with other media. Transfusion with RBCs cryopreserved in HES solution may result in posttransfusion hemolysis in birds.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To validate the use of noninvasive pulmonary function testing in sedated and nonsedated llamas and establish reference range parameters of respiratory mechanical function.

Animals—10 healthy adult llamas.

Procedures—Pulmonary function testing in llamas included the following: measurement of functional residual capacity (FRC) via helium dilution, respiratory inductance plethysmography (RIP) to assess breathing pattern and flow limitations, esophageal-balloon pneumotachography, and a monofrequency forced oscillatory technique (FOT; 1 to 7 Hz) before and after IM administration of xylazine (0.2 mg/kg).

Results—The following mean ± SD measurements of respiratory function were obtained in nonsedated llamas: FRC (5.60 ± 1.24 L), tidal volume (1.03 ± 0.3 L), dynamic compliance (0.83 ± 0.4 L/cm H2O), pulmonary resistance (RL; 1.42 ± 0.54 cm H2O/L/s), and respiratory system resistance (2.4 ± 0.9, 2.3 ± 0.7, 2.2 ± 0.6, 2.7 ± 0.7, and 2.5 ± 0.5 cm H2O/L/s at 1, 2, 3, 5, and 7 Hz, respectively) by use of FOT. Measurements of flow limitations via RIP were comparable to other species. Sedation with xylazine induced significant increases in RL and maximum change in transpulmonary pressure. Following sedation, a mean 127% increase in RL and mean 116% increase in respiratory system resistance were observed across 1 to 7 Hz. The magnitude of change in respiratory system resistance increased with decreasing impulse frequency, suggesting bronchoconstriction.

Conclusions and Clinical Relevance—Noninvasive pulmonary function testing is well tolerated in untrained unsedated llamas. These techniques have clinical applications in the diagnosis and treatment of respiratory tract disease, although testing should not be performed after sedation with xylazine.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To evaluate whether mesenchymal stem cells (MSCs) can be safely administered IV to dogs with congestive heart failure (CHF) secondary to myxomatous mitral valve disease (MMVD) to improve cardiac function and prolong survival time.

ANIMALS

10 client-owned dogs with CHF secondary to MMVD.

PROCEDURES

Dogs with an initial episode of CHF secondary to MMVD were enrolled in a double-blind, placebo-controlled clinical trial. Five dogs in the MSC group received allogeneic Wharton jelly–derived MSCs (2 X 106 cells/kg, IV), and 5 dogs in the placebo group received a 1% solution of autologous serum (IV) for 3 injections 3 weeks apart. Cell-release criteria included trilineage differentiation, expression of CD44 and CD90 and not CD34 and major histocompatability complex class II, normal karyotype, and absence of contamination by pathogenic microorganisms. Patients were followed for 6 months or until death or euthanasia. Echocardiographic data, ECG findings, serum cardiac biomarker concentrations, CBC, and serum biochemical analysis results were obtained prior to and 4 hours after the first injection and every 3 months after the final injection.

RESULTS

Lymphocyte and eosinophil counts decreased significantly 4 hours after injection, and monocytes decreased significantly only in dogs that received an MSC injection. No significant differences were seen in the echocardiographic variables, ECG results, serum cardiac biomarker concentrations, survival time, and time to first diuretic drug dosage escalation between the 2 groups.

CONCLUSIONS AND CLINICAL RELEVANCE

This study showed that MSCs can be easily collected from canine Wharton jelly as an allogeneic source of MSCs and can be safely delivered IV to dogs with CHF secondary to MMVD.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate respiratory mechanical function and bronchoalveolar lavage (BAL) cytologic results in healthy alpacas.

Animals—16 client-owned adult alpacas.

Procedures—Measurements of pulmonary function were performed, including functional residual capacity (FRC) via helium dilution, respiratory system resistance via forced oscillatory technique (FOT), and assessment of breathing pattern by use of respiratory inductive plethysmography (RIP) in standing and sternally recumbent alpacas. Bronchoalveolar lavage was performed orotracheally during short-term anesthesia.

Results—Mean ± SD measurements of respiratory function were obtained in standing alpacas for FRC (3.19 ± 0.53 L), tidal volume (0.8 ± 0.13 L), and respiratory system resistance at 1 Hz (2.70 ± 0.88 cm H2O/L/s), 2 Hz (2.98 ± 0.70 cm H2O/L/s), 3 Hz (3.14 ± 0.77 cm H2O/L/s), 5 Hz (3.45 ± 0.91 cm H2O/L/s), and 7 Hz (3.84 ± 0.93 cm H2O/L/s). Mean phase angle, as a measurement of thoracoabdominal asynchrony, was 19.59 ± 10.06°, and mean difference between nasal and plethysmographic flow measurements was 0.18 ± 0.07 L/s. Tidal volume, peak inspiratory flow, and peak expiratory flow were significantly higher in sternally recumbent alpacas than in standing alpacas. Cytologic examination of BAL fluid revealed 58.52 ± 12.36% alveolar macrophages, 30.53 ± 13.78% lymphocytes, 10.95 ± 9.29% neutrophils, 0% mast cells, and several ciliated epithelial cells.

Conclusions and Clinical Relevance—Pulmonary function testing was tolerated well in nonsedated untrained alpacas. Bronchoalveolar lavage in alpacas yielded samples with adequate cellularity that had a greater abundance of neutrophils than has been reported in horses.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of the topically applied calcium-channel blocker flunarizine on intraocular pressure (IOP) in clinically normal dogs.

Animals—20 dogs.

Procedures—Baseline diurnal IOPs were determined by use of a rebound tonometer on 2 consecutive days. Subsequently, 1 randomly chosen eye of each dog was treated topically twice daily for 5 days with 0.5% flunarizine. During this treatment period, diurnal IOPs were measured. In addition, pupillary diameter and mean arterial blood pressure (MAP) were evaluated. Serum flunarizine concentrations were measured on treatment day 5. Intraday fluctuation of IOP was analyzed by use of an ANOVA for repeated measures and a trend test. Changes in IOP from baseline values were assessed and compared with IOPs for the days of treatment. Values were also compared between treated and untreated eyes.

Results—A significant intraday fluctuation in baseline IOP was detected, which was highest in the morning (mean ± SE, 15.8 ± 0.63 mm Hg) and lowest at night (12.9 ± 0.61 mm Hg). After 2 days of treatment, there was a significant decrease in IOP from baseline values in treated (0.93 ± 0.35 mm Hg) and untreated (0.95 ± 0.34 mm Hg) eyes. There was no significant treatment effect on pupillary diameter or MAP. Flunarizine was detected in serum samples of all dogs (mean ± SD, 3.89 ± 6.36 μg/L).

Conclusions and Clinical Relevance—Topically applied flunarizine decreased IOP in dogs after 2 days of twice-daily application. This calcium-channel blocker could be effective in the treatment of dogs with glaucoma.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether tension of the girth strap of a saddle would sufficiently affect rib motion and reduce lung volume to alter pulmonary resistance in horses.

Animals—10 healthy adult horses.

Procedure—We used classical techniques to measure the effects of tightening a girth strap (15 kg of tension) on pulmonary dynamics during eupnea and hyperpnea in horses. Respiratory impedance was evaluated by use of oscillometry, and resistance and reactance data were partitioned into lung and chest wall components. Rib cage and abdominal contributions to tidal volume and minute ventilation were measured by use of respiratory inductance plethysmography. Effects of strap tension on functional residual capacity (FRC) were measured during eupnea by use of a helium-dilution technique. In a subgroup of 6 horses, we also measured transdiaphragmatic pressures during eupnea and hyperpnea induced by administration of lobeline hydrochloride (0.2 mg/kg, IV).

Results—Pulmonary resistance measured by use of oscillometry but not by use of classical methods was significantly increased by the tension of the girth strap. However, the increase in pulmonary resistance could not be explained by a decrease in FRC. Motion of the rib cage was significantly reduced during eupnea and hyperpnea. However, ventilatory variables (tidal volume, minute ventilation, and peak flows), FRC, and transdiaphragmatic pressures were unaltered by strap tension.

Conclusions and Clinical Relevance—Although tension of the girth strap caused measurable changes in respiratory mechanics (loss of rib motion and increased pulmonary resistance), there was no evidence that ventilation was limited. (Am J Vet Res 2005;66:1167–1174)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the use of a modified whole body plethysmograph in awake sheep.

Animals—10 healthy adult sheep.

Procedure—Concurrent measurements of specific airway resistance (sRaw) and pulmonary resistance (RL) were obtained using a novel noninvasive headout constant-volume plethysmograph and esophageal balloon-pneumotachography, respectively. All data were collected before and after external resistive loading with 1 and 5.6 cm H20/L/s. Functional residual capacity (FRC) was measured by helium dilution for computation of airway resistance (Raw) preloading (Raw = sRaw/FRC).

Results—The sRaw and RL were closely correlated in 10 adult sheep. Additionally, sRaw and RL accurately reflected the magnitude of added resistance. The mean FRC was 52 mL/kg and used to calculate Raw. At baseline, the values for Raw were significantly correlated with sRaw and RL.

Conclusions and Clinical Relevance—Precise measurements of sRaw and Raw at baseline and sRaw after external resistive loading were obtained by use of this novel noninvasive plethysmographic technology. This method should have application to veterinary patients or animals used in research in which noninvasive rapid or serial measurements of sRaw in the conscious state are required. (Am J Vet Res 2004;65:1259–1264)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate the association between airway reactivity and age, sex, body weight, and radiographic findings in cats.

Animals—32 mature cats that constituted 2 age groups (17 young cats that were 1 to 2 years old and 15 old cats that were 12 to 13 years old).

Procedure—Cats were placed in the chamber of a barometric whole-body plethysmograph (volume, 38 L), and box pressure was measured at baseline and after aerosol administration of increasing concentrations of carbachol. Airway reactivity was assessed by monitoring increases in enhanced pause (PENH), a unitless variable that measures bronchoconstriction as derived from dose-response curves. The endpoint chosen was the provocative concentration of carbachol that increased PENH to 300% of the baseline value (PCPENH300).

Results—We did not find a correlation between PCPENH300 and sex, body weight, number of eosinophils, PENH before bronchoconstriction, respiratory frequency, tidal volume, or minute ventilation. Airway reactivity was significantly less in the old cats (mean ± SD PCPENH300, 0.578 ± 0.051%), compared with the value for the young cats (0.053 ± 0.006%). Radiographic patterns differed significantly between groups of cats; a greater proportion of old cats (12/15) had bronchointerstitial patterns, compared with the proportion of young cats (4/17).

Conclusion and Clinical Relevance—These data support the notion that age exerts a strong influence on airway reactivity in adult cats, and radiographic differences suggest that structural changes in older cats may contribute to this effect. These findings have important implications for interpretation of results of airway reactivity tests in cats. (Am J Vet Res 2003;64:26–31)

Full access
in American Journal of Veterinary Research