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.
PROCEDURES A catheter was aseptically placed into a jugular vein. Each animal was anesthetized and properly positioned, and 0.25% ICG was administered. Images were obtained by use of an adaptor system consisting of a modified digital single-lens reflex camera, camera adaptor, and camera lens. Images were obtained at a rate of 3 images/s for the 60 seconds immediately after ICG administration and then at 2, 3, 4, and 5 minutes after administration. Ten minutes later, 10% SF was administered IV and images were obtained in a similar manner.
RESULTS Angiography with ICG provided visual examination of the arterial, capillary, and venous phases in all species. Visual examination of the iris vasculature by use of SF was performed in goats and sheep but was not possible in the alpacas because of iridal pigmentation. Extravasation of SF was a common finding in sheep and alpacas but not in goats. No adverse events were detected.
CONCLUSIONS AND CLINICAL RELEVANCE Quality angiographic images of the anterior segment were obtainable after IV administration of ICG to goats, sheep, and alpacas. This may provide a useful imaging modality for ocular research in these animal species.
To determine corneal thickness of eyes of healthy goats, sheep, and alpacas by use of a portable spectral-domain optical coherence tomography (SD-OCT) device and evaluate intraoperator reliability for measurements.
11 female goats, 10 female sheep, and 11 (4 males and 7 females) alpacas.
Each animal was sedated, and gentle manual restraint was used to ensure proper positioning of the head and globe. Corneal pachymetry was performed (in triplicate) with a portable SD-OCT device on both eyes of each animal. All corneal measurements were obtained manually by use of the integrated caliper function. Corneal epithelial thickness (CET), corneal stromal thickness (CST), Descemet membrane thickness (DMT), and total corneal thickness (TCT) were measured twice on each image, and a mean value was calculated.
Mean ± SD values for CET, CST, DMT, and TCT were 96.1 ± 5.0 μm, 486.0 ± 10.3 μm, 36.8 ± 4.8 μm, and 616.9 ± 7.1 μm, respectively, for the goats; 111.6 ± 5.7 μm, 599.8 ± 10.0 μm, 31.0 ± 4.5 μm, and 741.1 ± 9.9 μm, respectively, for the sheep; and 147.4 ± 5.7 μm, 446.1 ± 7.4 μm, 44.5 ± 5.0 μm, and 634.8 ± 6.2 μm, respectively, for the alpacas. Intraclass correlations ranged from 0.49 to 0.83 for CET, CST, and TCT and from 0.13 to 0.36 for DMT.
CONCLUSIONS AND CLINICAL RELEVANCE
SD-OCT provided manual measurement of corneal thickness (CET, CST, and TCT) with clinically acceptable intraoperator reliability for eyes of healthy goats, sheep, and alpacas.
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.
Objective—To determine humoral responses to an equine encephalitis vaccine in healthy alpacas.
Animals—39 healthy alpacas on 1 farm and 86 healthy alpacas on a second farm.
Procedures—All alpacas were given 3 doses IM of a bivalent, killed-virus equine encephalitis vaccine, with 4 weeks between doses. Eastern equine encephalitis (EEE) virus neutralizing antibody responses were determined with a plaque reduction neutralization assay every 14 days in alpacas on the first farm and 70 days after the first dose of vaccine on the second farm.
Results—For alpacas on the first farm, geometric mean virus neutralizing antibody titer peaked 2 weeks after the third vaccine dose was given (ie, day 70). At this time, 29 of 38 (76%) animals were seropositive for antibodies against EEE virus, and percentage of animals ≤ 2 years old that were seropositive (16/17) was significantly higher than percentage of animals > 6 years old that were seropositive (1/5). For alpacas on the second farm, 76 (88%) were seropositive on day 70, and percentage of animals ≤ 2 years old that were seropositive (24/24) was significantly higher than percentage of animals > 6 years old that were seropositive (27/33). For both farms, geometric mean titer on day 70 was significantly higher in animals < 2 years old than in animals > 6 years old.
Conclusions and Clinical Relevance—Results suggested that inoculation of alpacas with 3 doses of a bivalent, killed-virus equine encephalitis vaccine induced a humoral antibody response against EEE virus.
Case Description—6 female alpacas, ranging in age from < 1 day to > 2 years, were examined because of primary owner complaints related to urogenital malformation.
Clinical Findings—In all instances, the vulva was totally to subtotally imperforate. One neonate had failure of passive transfer of immunity and mild azotemia at the time of initial examination. No additional urogenital malformations were detected in any of the alpacas.
Treatment and Outcome—Vulvoplasty performed via local anesthesia was successful in all alpacas. The neonate with failure of passive transfer received a plasma transfusion. Postsurgical wound management was limited to topically applied medications.
Clinical Relevance—Congenital vulvar deformity in alpacas may result in interference with urine outflow. Neonates with a completely imperforate vulva may be brought to veterinarians for examination on an emergency basis. Less severely affected alpacas may be examined later in life with owner complaints ranging from stranguria or dysuria to urogenital malformation. No other primary abnormalities of the urogenital tract in alpacas have been reported, to the authors' knowledge. Vulvoplasty, performed with local anesthesia, resolves obstructed urine flow. Because it is possible that this condition is heritable, affected alpacas, and possibly their sires and dams, should not be used for breeding.
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
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)
Objective—To characterize the cardiopulmonary effects of dobutamine and norepinephrine infusion in isoflurane-anesthetized healthy alpacas.
Animals—8 adult alpacas.
Procedures—Initial baseline cardiovascular, respiratory, and metabolic variables were obtained 30 minutes after induction of isoflurane anesthesia in 8 alpacas (3 females and 5 sexually intact males). Four treatments (dobutamine at 4 and 8 μg/kg/min and norepinephrine at 0.3 and 1 μg/kg/min) were administered in random order via constant rate infusion over 15 minutes, followed by repeat measurements of cardiopulmonary values and a 20-minute washout period. Subsequent baseline and posttreatment measurements were similarly repeated until both drugs and dosages were administered to each animal. Baseline data in awake alpacas were obtained 18 to 24 hours following recovery from anesthesia.
Results—Both dobutamine and norepinephrine significantly increased cardiac index and arterial blood pressure from baseline values. Similar increases in hemoglobin concentration, oxygen content, and oxygen delivery were observed following administration of each drug at either dosage. Only dobutamine, however, reduced relative oxygen consumption while improving overall tissue oxygenation. Furthermore, heart rate was selectively enhanced by dobutamine and systemic vascular resistance by norepinephrine. Norepinephrine infusion resulted in dose-dependent changes in cardiopulmonary variables.
Conclusions and Clinical Relevance—Results indicated that both dobutamine and norepinephrine were appropriate choices to improve cardiac index, mean arterial pressure, and overall oxygen delivery in alpacas with isoflurane-induced hypotension. Careful titration by use of low infusion rates of dobutamine and norepinephrine is recommended to avoid potential arrhythmogenic effects and excessive vasoconstriction, respectively.