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  • Author or Editor: Alejandro Valdés-Martínez x
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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE To determine the pharyngeal and laryngeal distribution of radiopaque contrast medium administered orally or via nasopharyngeal catheter to standing horses.

ANIMALS 5 healthy adult horses.

PROCEDURES A crossover study was conducted. Radiopaque contrast medium (12 mL) was administered orally and via nasopharyngeal catheter to each horse. Pharyngeal and laryngeal distribution of contrast medium was determined by examination of radiographs obtained immediately after administration of contrast medium, compared with those obtained before administration. Regional distribution of contrast medium was graded. Endoscopic examination of the nasopharynx, laryngopharynx, and larynx was performed to confirm radiographic results.

RESULTS Examination of radiographs obtained after nasopharyngeal administration revealed contrast medium in the nasopharynx (n = 5), oropharynx (2), laryngopharynx (3), and larynx (5) of the 5 horses. Examination of radiographs obtained after oral administration revealed contrast medium in the oropharynx (n = 4) and larynx (1) of the 5 horses. Endoscopic examination confirmed radiographic findings and was found to be sensitive for detection of contrast medium in the laryngopharynx, whereby detection rates were higher for both administration methods.

CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that medication administered by use of a nasopharyngeal catheter will result in topical distribution within the nasopharynx, including the dorsal surface of the soft palate, and larynx, although distribution should be evaluated in horses with clinical airway disease to confirm these findings. Oral administration did not result in consistently detectable topical laryngeal distribution but could be used for selected conditions (eg, palatitis).

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate tissue diffusion of anesthetic agent following administration of low palmar nerve blocks (LPBs) in horses.

Design—Randomized clinical trial.

Animals—12 adult horses.

Procedures—In 9 horses, mepivacaine hydrochloride–iohexol (50:50 dilution) injections were administered bilaterally (2 or 4 mL/site) to affect the medial and lateral palmar and palmar metacarpal nerves (4 sites). Lateral radiographic views of both metacarpal regions were obtained before and at 5, 15, 30, 60, 90, and 120 minutes after block administration; proximal and distal extents of contrast medium (and presumably anesthetic agent) diffusion from palmar and palmar metacarpal injection sites were measured and summed to determine total diffusion. Methylene blue solution was injected in forelimbs of 3 other horses that were subsequently euthanized to determine the potential route of anesthetic agent diffusion to the proximal suspensory ligament region.

Results—Mean extents of proximal and total contrast medium diffusion were 4.0 and 6.6 cm, respectively, for the palmar metacarpal nerves and 4.3 and 7.1 cm, respectively, for the palmar nerves. Subtle proximal diffusion secondary to lymphatic drainage was evident in 17 of the 18 limbs. Contrast medium was detected in the metacarpophalangeal joint or within the digital flexor tendon sheath in 8 and 7 limbs, respectively. In the cadaver limbs, methylene blue solution did not extend to the proximal suspensory ligament region.

Conclusions and Clinical Relevance—In horses, LPBs resulted in minimal proximal diffusion of anesthetic agent from the injection sites. Limbs should be aseptically prepared prior to LPB administration because inadvertent intrasynovial injection may occur.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the ideal interval to image acquisition after IV injection of sodium fluoride F 18 (18F-NaF) and evaluate biodistribution of the radiopharmaceutical in clinically normal skeletally immature dogs.

Animals—4 female dogs.

Procedures—Each dog was anesthetized for evaluation with a commercial hybrid positron emission tomography (PET)–CT instrument. A low–radiation dose, whole-body CT scan was acquired first. An IV injection of 18F-NaF (0.14 mCi/kg) was administered, and a dynamic PET scan centered over the heart and liver was acquired during a period of 120 minutes. Uptake of 18F-NaF in the blood pool, soft tissues, and skeletal structures was evaluated via region of interest analysis to derive standardized uptake values and time-activity curves, which were used to determine the optimal postinjection time for skeletal image acquisition. Biodistribution was also assessed from a final whole-body PET-CT scan acquired after the dynamic scan.

Results—Time-activity curves revealed a rapid decrease in the amount of radiopharmaceutical in the blood pool and soft tissues and a rapid increase in the amount of radiopharmaceutical in bones soon after injection. At 50 minutes after injection, the greatest difference in uptake between soft tissues and bones was detected, with continued subtle increase in uptake in the bones. Uptake of 18F-NaF was slightly increased at growth plates and open ossification centers, compared with that at other parts of the bone.

Conclusions and Clinical Relevance—At 50 minutes after IV injection of 18F-NaF at the dose evaluated, PET-CT yielded excellent bone-to-background ratio images for evaluation of the skeletal system in dogs.

Full access
in American Journal of Veterinary Research

Abstract

CASE DESCRIPTION A 12-year-old mixed-breed mare (horse 1) and 6-year-old Friesian gelding (horse 2) were examined for chronic lameness associated with the stifle joint.

CLINICAL FINDINGS Lameness examination revealed effusion of the right (horse 1) or left (horse 2) femoropatellar and medial femorotibial joints and grade 3/5 (horse 1) or 4/5 (horse 2) lameness. A diagnosis of cranial cruciate ligament (CCL) injury with associated mineralization and avulsion (horse 1) or mineralization alone (horse 2) was facilitated in both horses with a caudomedial-craniolateral oblique radiographic view obtained 45° medial to the caudocranial line, which highlighted the origin of the ligament on the caudoaxial aspect of the lateral femoral condyle within the intercondylar fossa. These lesions were subsequently confirmed via CT.

TREATMENT AND OUTCOME Arthroscopy of the medial and lateral femorotibial joints was performed for horse 1 and revealed the osseous fragment associated with the CCL, but the fragment could not be removed. Horse 2 was euthanized while anesthetized following CT owing to the poor prognosis.

CONCLUSIONS AND CLINICAL RELEVANCE Radiography is typically the first imaging modality attempted for horses with CCL injury, particularly outside the hospital setting. A 45° caudomedial-craniolateral oblique radiographic view may aid in diagnosis of CCL injury when avulsion or mineralization is present. Although this view is not commonly included in the typical radiographic series for imaging of the stifle joint in horses, it should be considered when CCL injury is suspected.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To develop a quantitative method of interpreting tibial scintigrams of Thoroughbred racehorses with tibial stress fractures that may facilitate diagnosis of fractures and to provide prognostic information regarding future performance of affected horses.

Animals—35 Thoroughbred racehorses.

Procedures—Static bone-phase scintigrams of tibial stress fractures were quantitatively analyzed by use of ratios of the mean radionuclide counts per pixel in a region of interest (ROI) drawn around the area of increased uptake of radiopharmaceutical to mean counts per pixel in a second ROI drawn around an apparently normal area of the tibial diaphysis. In horses with unilateral fractures, ratios for the contralateral tibia were determined by use of 2 ROIs drawn at the same positions as the ROIs in the fractured tibia. Ratios were compared between fractured versus apparently normal tibias, between horses that returned to racing versus those that did not, and among horses with various grades of lameness. The association between ratios for fractured tibias and intervals between diagnosis and return to racing was also assessed.

Results—Mean ratio of ROIs in apparently normal tibias was 1.35 (95% confidence interval [CI], 1.21 to 1.50); that in tibias with stress fractures was 3.55 (95% CI, 2.50 to 4.60). These ratios were significantly different. None of the associations between ratios for fractured tibias and grades of lameness or performance outcomes were significant.

Conclusions and Clinical Relevance—Tibial stress fracture scintigrams can be quantitatively analyzed. A prospective study with a controlled rehabilitation period is necessary to evaluate the possible applications of this method.

Full access
in American Journal of Veterinary Research