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Abstract

Objective—To evaluate differences in response to ID injection of histamine, phytohemagglutinin (PHA), and Aspergillus organisms between clinically normal horses and horses with recurrent airway obstruction (RAO).

Animals—5 healthy adult horses and 5 adult horses with RAO.

Procedure—Intradermal testing (IDT) was performed on the neck with 2 positive control substances (histamine and PHA) and a mixture comprising 5 Aspergillus species. Four concentrations of each test substance plus a negative control substance were used. Equal volumes (0.1 mL) of each test substance were prepared to yield 15 syringes ([4 concentrations of each test substance plus 1 negative control substance] times 3 test substances) for each side of each horse (ie, 30 syringes/horse). Intradermal injections were administered; diameter of wheals was recorded 0.5, 4, and 24 hours after injection.

Results—Hypersensitive responses to ID injection of histamine were detected 0.5 hours after injection, and a delay in wheal formation after ID injection of Aspergillus mixture 24 hours after injection was detected in RAO-affected horses but was not observed in clinically normal horses. No differences were detected between the 2 groups after ID injection of PHA.

Conclusions and Clinical Relevance—RAO-affected horses are hypersensitive to histamine, suggesting that RAO is associated with a heightened vascular response to histamine. Higher concentrations of Aspergillus mixture may be needed to detect horses that are sensitive to this group of antigens. Wheal reactions to Aspergillus may be a delayed response, suggesting that IDT results should be evaluated 0.5, 4, and 24 hours after ID injection. (Am J Vet Res2005;66:1348–1355)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To determine the accuracy of 2 interstitial glucose-monitoring systems (GMSs) for use in horses compared with a point-of-care (POC) glucometer and standard laboratory enzymatic chemistry method (CHEM).

ANIMALS

8 clinically normal adult horses.

PROCEDURES

One of each GMS device (Dexcom G6 and Freestyle Libre 14-day) was placed on each horse, and blood glucose concentration was measured via POC and CHEM at 33 time points and compared with simultaneous GMS readings. An oral glucose absorption test (OGAT) was performed on day 2, and glucose concentrations were measured and compared.

RESULTS

Glucose concentrations were significantly correlated with one another between all devices on days 1 to 5. Acceptable agreement was observed between Dexcom G6 and Freestyle Libre 14-day when compared with CHEM on days 1, 3, 4, and 5 with a combined mean bias of 10.45 mg/dL and 1.53 mg/dL, respectively. During dextrose-induced hyperglycemia on day 2, mean bias values for Dexcom G6 (10.49 mg/dL) and FreeStyle Libre 14-day (0.34 mg/dL) showed good agreement with CHEM.

CLINICAL RELEVANCE

Serial blood glucose measurements are used to diagnose or monitor a variety of conditions in equine medicine; advances in near-continuous interstitial glucose monitoring allow for minimally invasive glucose assessment, thereby reducing stress and discomfort to patients. Data from this study support the use of the Dexcom G6 and Freestyle Libre 14-day interstitial glucose-monitoring systems to estimate blood glucose concentrations in horses.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To assess whether the combination of hyaluronan, sodium chondroitin sul-fate, and N-acetyl-d-glucosamine (HCSG) lubricates articular cartilage in vitro and modulates joint lubrication in vivo.

ANIMALS

16 healthy adult horses.

PROCEDURES

The effects of HCSG injections on SF lubricant properties and joint health, immediately after injury and 2 weeks later, were analyzed by use an equine osteochondral fracture model of post-traumatic osteoarthritis (OA). Middle carpal joints of adult horses were randomly assigned to 1 of 4 surgical treatment groups as follows: normal nonsurgical group (n = 8), normal sham-surgical group (8), OA-induced surgical group with HCSG injection (8), or OA-induced surgical group with saline (0.9% NaCl) solution injection (8). Synovial fluid was aspirated periodically and analyzed for boundary lubrication function and lubricant molecules. At 17 days, joints were screened for gross pathological changes.

RESULTS

Induction of OA led to an impairment of SF lubrication function and diminished hyaluronan concentration in a time-dependent manner following surgery, with HCSG injection lessening these effects. Certain friction coefficients approached those of unaffected normal equine SF. Induction of OA also caused synovial hemorrhage at 17 days, which was lower in joints treated with HCSG.

CONCLUSIONS AND CLINICAL RELEVANCE

After induction of OA, equine SF lubricant function was impaired. Hyaluronan-sodium chondroitin sulfate–N-acetyl-d-glucosamine injection restored lubricant properties at certain time points and reduced pathological joint changes.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the precision of intradermal testing (IDT) in horses.

Animals—12 healthy adult horses.

Procedure—IDT was performed on the neck of each horse by use of 2 positive control substances (histamine and phytohemagglutinin [PHA]) and a negative control substance. An equal volume (0.1 mL) for each injection was prepared to yield a total of 20 syringes ([4 concentrations of each positive control substance plus 1 negative control substance] times 2 positive control substances times 2 duplicative tests) for each side of the neck. Both sides of the neck were used for IDT; therefore, 40 syringes were prepared for each horse. Hair was clipped on both sides of the neck, and ID injections were performed. Diameter of the skin wheals was recorded 0.5, 4, and 24 hours after ID injection.

Results—Intra- and interhorse skin reactions to ID injection of histamine and PHA resulted in wheals of uniform size at 0.5 and 4 hours, respectively. Significant intra- and interhorse variation was detected in wheals caused by PHA at 24 hours.

Conclusions and Clinical Relevance—ID injection of histamine and PHA caused repeatable and precise results at 0.5 and 4 hours, respectively. Concentrations of 0.005 mg of histamine/mL and 0.1 mg of PHA/mL are recommended for use as positive control substances for IDT in horses. This information suggests that consistent wheal size is evident for ID injection of control substances, and variation in wheals in response to ID injection of test antigens results from a horse's immune response to specific antigens. (Am J Vet Res 2005;66:1341–1347)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To assess multiple central venous and arterial blood variables that alone or in conjunction with one another reflect global oxygenation status in healthy neonatal foals.

ANIMALS 11 healthy neonatal foals.

PROCEDURES Central venous and arterial blood samples were collected from healthy neonatal foals at 12, 24, 36, 48, 72, and 96 hours after birth. Variables measured from central venous and arterial blood samples included oxygen saturation of hemoglobin, partial pressure of oxygen, lactate concentration, partial pressure of carbon dioxide, and pH. Calculated variables included venous-to-arterial carbon dioxide gap, estimated oxygen extraction ratio, ratio of partial pressure of oxygen in arterial blood to the fraction of inspired oxygen, bicarbonate concentration, base excess, and blood oxygen content.

RESULTS Significant differences between arterial and central venous blood obtained from neonatal foals were detected for several variables, particularly partial pressure of oxygen, oxygen saturation of hemoglobin, and oxygen content. In addition, the partial pressure of carbon dioxide in central venous blood samples was significantly higher than the value for corresponding arterial blood samples. Several temporal differences were detected for other variables.

CONCLUSIONS AND CLINICAL RELEVANCE Results of this study provided information about several variables that reflect global oxygenation in healthy neonatal foals. Values for these variables in healthy foals can allow for comparison with values for critically ill foals in future studies. Comparison of these variables between healthy and ill foals may aid in treatment decisions and prognosis of clinical outcome for critically ill foals.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To determine the pharmacokinetics and clinical safety of acetaminophen after oral administration of 40 mg/kg q 12 hours or 60 mg/kg q 24 hours for 14 days.

ANIMALS

12 healthy light-breed neonatal foals.

PROCEDURES

6 foals received acetaminophen at 40 mg/kg q 12 hours and 6 foals received 60 mg/kg q 24 hours for 14 days. The study dates were January 31 to April 15, 2023. Physical examinations were performed daily. Plasma disposition of acetaminophen was determined after the first, mid-point drug administration. Hematology and biochemistry analysis was performed before the study, day 7, and the last day of drug administration. Plasma acetaminophen concentrations were determined by high-performance liquid chromatography. Plasma pharmacokinetic parameters were estimated using noncompartmental analysis.

RESULTS

No statistically significant changes occurred on hematology or biochemistry profiles. Elevations in γ-glutamyl transferase (GGT) and sorbitol dehydrogenase (SDH) were noted in 4 foals at various time points. The maximum plasma concentration (Cmax) occurred within 2 hours for both doses. The 60 mg/kg dose resulted in a larger median Cmax (range) at 28 μg/mL (22–32) than the 40 mg/kg dose at 23 μg/mL (19–27). The median area under the concentration-vs-time curve from 0 to 8 hours (AUC0–8 hour [range]) was 100 h•µg/mL (82–100) at 40 mg/kg and 128 h•µg/mL (120–168) for 60 mg/kg. Trough concentrations decreased over time for both regimens.

CLINICAL RELEVANCE

Foals tolerate oral acetaminophen at 40 mg/kg q 12 hours or 60 mg/kg q 24 hours. Further analgesic and antipyretic studies will help to delineate optimal dosage regimens of acetaminophen to treat foals.

Open access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effects of various flow rates of oxygen administered via 1 or 2 nasal cannulae on the fraction of inspired oxygen concentration (Fio2) and other arterial blood gas variables in healthy neonatal foals.

Animals—9 healthy neonatal (3- to 4-day-old) foals.

Procedures—In each foal, a nasal cannula was introduced into each naris and passed into the nasopharynx to the level of the medial canthus of each eye; oxygen was administered at 4 flow rates through either 1 or both cannulae (8 treatments/foal). Intratracheal Fio2, intratracheal end-tidal partial pressure of carbon dioxide, and arterial blood gas variables were measured before (baseline) and during unilateral and bilateral nasopharyngeal delivery of 50, 100, 150, and 200 mL of oxygen/kg/min.

Results—No adverse reactions were associated with administration of supplemental oxygen except at the highest flow rate, at which the foals became agitated. At individual flow rates, significant and dose-dependent increases in Fio2, Pao2, and oxygen saturation of hemoglobin (Sao2) were detected, compared with baseline values. Comparison of unilateral and bilateral delivery of oxygen at similar cumulative flow rates revealed no differences in evaluated variables.

Conclusions and Clinical Relevance—Results indicated that administration of supplemental oxygen via nasal cannulae appeared to be a highly effective means of increasing Fio2, Pao2, and Sao2 in neonatal foals. These findings may provide guidance for implementation of oxygen treatment in hypoxemic neonatal foals. (Am J Vet Med 2010;71:1081–1088)

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.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine clinical characteristics, clinicopathologic data, and bacterial culture and antimicrobial susceptibility results associated with septic arthritis in foals ≤ 180 days old.

Design—Retrospective case series.

Animals—83 foals with septic arthritis.

Procedures—Medical records at 2 teaching hospitals between 1998 and 2013 were searched to identify those for foals ≤ 180 days old with confirmed infection of ≥ 1 synovial structure. Data extracted from the records included signalment, clinicopathologic information, bacteriologic culture and antimicrobial susceptibility results, and outcome. Data were analyzed for all foals as a single population and for foals stratified into 3 age groups (≤ 7 days, 8 to 30 days, and 31 to 180 days).

Results—Mean ± SD age of all foals was 18.2 ± 25 days (range, 0 to 180 days). The median number of joints affected per foal was 2 (range, 1 to 10 joints). Forty-seven of 83 (56.6%) foals survived to discharge from the hospital. Seventy antemortem synovial fluid samples underwent bacteriologic culture, of which 60 (85.7%) yielded growth. Of the 72 bacterial isolates identified, 45 (62.5%) were gram negative and 27 (375%) were gram positive. Survival rate was positively associated with plasma fibrinogen concentration and negatively associated with number of affected joints.

Conclusions and Clinical Relevance—Results indicated the frequency with which certain bacterial agents were isolated from septic joints, which may be beneficial for the empirical treatment of septic arthritis in foals. Also, the positive association between survival rate and plasma fibrinogen concentration may have prognostic value in a clinical setting.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate baseline plasma cortisol and ACTH concentrations and responses to low-dose ACTH stimulation testing in ill foals.

Design—Cross-sectional study.

Animals—58 ill foals.

Procedures—Baseline cortisol and ACTH concentrations and cortisol concentrations after administration of a low dose of cosyntropin were determined within 6 hours after admission. Foals were assigned to 4 groups on the basis of age (≤ 24 hours vs 1 to 56 days) and presence of septicemia (yes vs no). Values were compared among groups and with values previously reported for healthy foals.

Results—Plasma cortisol concentrations 30 and 60 minutes after cosyntropin administration in foals ≤ 24 hours old were significantly higher than corresponding cortisol concentrations in older foals. In all 4 groups, plasma cortisol concentration 30 minutes after cosyntropin administration was significantly higher than baseline cortisol concentration or concentration 60 minutes after cosyntropin administration. No differences in baseline cor-tisol or ACTH concentration or in the ACTH-to-cortisol ratio were detected between groups or when ill foals were compared with healthy foals. A small number of ill foals had low baseline cortisol and ACTH concentrations or low responses to cosyntropin administration, compared with healthy foals.

Conclusions and Clinical Relevance—Results indicated that most ill foals in the present study population had adequate responses to cosyntropin administration. However, a small subset of ill foals appeared to have dysfunction of the hypothalamic-pituitary-adrenal axis.

Full access
in Journal of the American Veterinary Medical Association