Objective—To evaluate changes in heart rate (HR)
and mean arterial pressure (MAP) as indicators of
changes in pressor response for muscle afferents
after topical application of menthol (MEN)-based analgesic
Animals—11 decerebrate cats.
Procedure—Pressor responses were reflexively
evoked by static contraction of hind limb muscles,
which are caused by group III and IV afferents.
Responses were monitored without interference
from anesthesia or effects of higher brain function by
the use of decerebrate cats. After obtaining baseline
data, MEN analgesic balm (1.9%) was applied to the
skin over contracting muscles of 1 hind limb in 6 cats;
petrolatum was applied to 5 control cats. Muscle contractions
were evoked every 10 minutes, alternating
between hind limbs, for 120 minutes. Peak MAP and
HR were analyzed.
Results—Peak MAP responses evoked by static
muscle contraction for the ipsilateral hind limb were
significantly attenuated 20 minutes after application,
but approached baseline values 40 minutes after
application. The pressor response was significantly
decreased 20 minutes after application during the last
12 seconds of the stimulus, which was attributed to
group IV afferents. There were no significant differences
in HR responses.
Conclusions and Clinical Relevance—Application of
MEN analgesic balm to the skin over contracting muscles
significantly decreased the pressor response to
static muscle contractions. This suggests that topical
application of MEN has effects on responses evoked
from receptors located in muscles. The MEN analgesic
balm appeared to attenuate the pressor
response 20 minutes after application, but it was a
short-term effect. (Am J Vet Res 2004;65:1204–1210)
OBJECTIVE To determine pharmacokinetics and pulmonary disposition of minocycline in horses after IV and intragastric administration.
ANIMALS 7 healthy adult horses.
PROCEDURES For experiment 1 of the study, minocycline was administered IV (2.2 mg/kg) or intragastrically (4 mg/kg) to 6 horses by use of a randomized crossover design. Plasma samples were obtained before and 16 times within 36 hours after minocycline administration. Bronchoalveolar lavage (BAL) was performed 4 times within 24 hours after minocycline administration for collection of pulmonary epithelial lining fluid (PELF) and BAL cells. For experiment 2, minocycline was administered intragastrically (4 mg/kg, q 12 h, for 5 doses) to 6 horses. Plasma samples were obtained before and 20 times within 96 hours after minocycline administration. A BAL was performed 6 times within 72 hours after minocycline administration for collection of PELF samples and BAL cells.
RESULTS Mean bioavailability of minocycline was 48% (range, 35% to 75%). At steady state, mean ± SD maximum concentration (Cmax) of minocycline in plasma was 2.3 ± 1.3 μg/mL, and terminal half-life was 11.8 ± 0.5 hours. Median time to Cmax (Tmax) was 1.3 hours (interquartile range [IQR], 1.0 to 1.5 hours). The Cmax and Tmax of minocycline in the PELF were 10.5 ± 12.8 μg/mL and 9.0 hours (IQR, 5.5 to 12.0 hours), respectively. The Cmax and Tmax for BAL cells were 0.24 ± 0.1 μg/mL and 6.0 hours (IQR, 0 to 6.0 hours), respectively.
CONCLUSIONS AND CLINICAL RELEVANCE Minocycline was distributed into the PELF and BAL cells of adult horses.
Objective—To determine whether cardiovascular
dysfunction is evident in horses with leukoencephalomalacia
experimentally induced by administration of
Animals—11 healthy horses of various breeds (body
weight, 252 to 367 kg).
Procedure—Horses were randomly assigned to 3
groups and administered fumonisin B1 daily. Horses
received IV injections of 0 (control horses; n = 4), 0.01
(3), or 0.20 mg (4) of fumonisin B1/kg for 7 to 28 days.
Horses were examined daily for evidence of neurologic
disease. When neurologic signs consistent with
leukoencephalomalacia were evident, horses were
anesthetized, and catheters were inserted for evaluation
of the cardiovascular system. After recovery from anesthesia,
hemodynamic measurements were obtained.
Results—Fumonisin-treated horses with clinical
signs of neurologic disease had evidence of cardiovascular
dysfunction manifested as decreases in
heart rate, cardiac output, right ventricular contractility
(assessed by measuring the maximal rate of
change of right ventricular pressure), coccygeal artery
pulse pressure, and pH and base excess in venous
blood as well as increases in systemic vascular resistance,
compared with values for control horses.
Fumonisin-treated horses with and without clinical
signs of neurologic disease also had higher serum
and right ventricular sphinganine and sphingosine
concentrations than control horses.
Conclusions and Clinical Relevance—An association
was detected among fumonisin-induced neurologic
disease, increased serum and myocardial sphinganine
and sphingosine concentrations, and decreased cardiovascular
function in horses. Fumonisin-induced
decreases in cardiovascular function may contribute to
the pathophysiologic development of leukoencephalomalacia
in horses. (Am J Vet Res 2002;63:538–545).
OBJECTIVE To compare CT and radiographic images of the lungs in sedated healthy foals positioned in sternal recumbency and to investigate whether a relationship exists between CT-derived measurements of lung attenuation and Paco2 and Pao2.
ANIMALS 6 healthy Standardbred foals < 14 days of age.
PROCEDURES Thoracic CT images were acquired followed by radiographic views with each foal sedated and positioned in sternal recumbency. For each foal, both CT and radiographic images were evaluated for severity and extent of changes by lung regions on the basis of a subjective scoring system by 3 investigators. Quantitative analysis of CT images was also performed. Assessments of Pao2 and Paco2 were performed before sedation, following sedation prior to CT, and after CT prior to radiography.
RESULTS Interobserver agreement for CT and radiographic image scoring was strong (0.73) and fair (0.65), respectively; intraobserver agreement was near perfect for CT (0.97) and radiographic (0.94) image scoring. Increased CT attenuation and radiographic changes were identified for all foals and were preferentially distributed in the caudoventral portion of the lungs. Radiographic scores were significantly lower than CT image scores. A positive correlation (r = 0.872) between lung attenuation and CT image score was identified. A significant increase in Paco2 was not considered clinically relevant. Significant changes in Pao2 were not observed.
CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that interpretation of CT images may be less subjective, compared with interpretation of radiographic images. These findings may aid in the evaluation of CT and radiographic images of neonatal foals with respiratory tract disease.
Objective—To compare signalment of horses with cervical vertebral malformation-malarticulation (CVM) with that of control horses and to describe results of clinical examination, diagnostic imaging and necropsy findings, and reported outcome in horses with CVM.
Design—Retrospective case-control study.
Animals—270 horses with CVM and 608 control horses admitted to 6 veterinary hospitals from 1992 through 2007.
Procedures—Medical records of participating hospitals were reviewed to identify horses with CVM (ie, case horses) and contemporaneous control (non-CVM-affected) horses that were admitted for treatment. Signalment was compared between case horses and control horses. Results of clinical examination, laboratory and diagnostic imaging findings, necropsy results, and outcome were assessed for horses with CVM.
Results—Case horses were younger (median age, 2 years) than were control horses (median age, 7 years). Thoroughbreds, warmbloods, and Tennessee Walking Horses were overrepresented in the CVM group. Gait asymmetry and cervical hyperesthesia were frequently detected in horses with CVM. Vertebral canal stenosis and articular process osteophytosis were commonly observed at necropsy; agreement between the results of radiographic or myelographic analysis and detection of lesions at necropsy was 65% to 71% and 67% to 78%, respectively. Of 263 horses with CVM for which outcome was recorded, 1 died and 172 (65.4%) were euthanatized.
Conclusions and Clinical Relevance—Odds of a diagnosis of CVM were greater in young horses and horses of specific breeds. Detection of gait asymmetry and cervical hyperesthesia were frequently reported in association with CVM. Accurate diagnosis of lesions associated with CVM by use of radiography and myelography can be challenging. (J Am Vet Med Assoc 2010;237:812-822)