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  • Author or Editor: Harold C. McKenzie x
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Abstract

Objective—To assess gentamicin concentrations in serum and bronchial lavage fluid (BLF) of horses during a 24-hour period after once-daily aerosol administration of gentamicin (GAER) for 7 days and the pattern and degree of bronchial tree inflammation associated with repeated GAER.

Animals—13 healthy adult horses (9 geldings and 4 mares).

Procedure—The treatment group comprised 8 horses, and 5 horses were untreated control animals. Gentamicin (20 mL of gentamicin [50 mg/mL]) was administered via aerosol once daily for 7 days. Samples of serum and BLF were obtained from all horses before GAER and 0.5, 4, 8, and 24 hours after the final day of GAER. Gentamicin concentrations were determined for all samples from treated horses, and cytologic examinations were performed on all BLF samples.

Results—Peak median BLF gentamicin concentration detected at 0.5 hours was 2.50 µg/mL. Median serum gentamicin concentration was < 0.50 µg/mL at all time points. Significant differences were not observed in total nucleated cell counts or differential cell counts in BLF between groups at any time point. Neutrophil count in BLF for all horses was increased over baseline at 4 and 24 hours.

Conclusions and Clinical Relevance—We did not detect evidence of gentamicin accumulation or respiratory inflammation after once-daily GAER for 7 days. This protocol appears unlikely to result in local or systemic toxicosis. Repeated daily GAER to horses appears to be a safe procedure and may have clinical use in the treatment of horses with bacterial infections of the airways. (Am J Vet Res 2004;65:173–178)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare concentrations of gentamicin in serum and bronchial lavage fluid after IV and aerosol administration of gentamicin to horses.

Animals—9 healthy adult horses.

Procedure—Gentamicin was administered by aerosolization (20 ml of gentamicin solution [50 mg/ml]) and IV injection (6.6 mg of gentamicin/kg of body weight) to each horse, with a minimum of 2 weeks between treatments. Samples of pulmonary epithelial lining fluid were collected by small volume (30 ml) bronchial lavage 0.5, 4, 8, and 24 hours after gentamicin administration. Serum samples were obtained at the same times. All samples were analyzed for gentamicin concentration, and cytologic examinations were performed on aliquots of bronchial lavage fluid collected at 0.5, 8, and 24 hours.

Results—Gentamicin concentrations in bronchial lavage fluid were significantly greater 0.5, 4, and 8 hours after aerosol administration, whereas serum concentrations were significantly less at all times after aerosol administration, compared with IV administration. Neutrophil counts in bronchial lavage fluid increased from 0.5 to 24 hours, regardless of route of gentamicin administration.

Conclusions and Clinical Relevance—Aerosol administration of gentamicin to healthy horses resulted in gentamicin concentrations in bronchial fluid that were significantly greater than those obtained after IV administration. A mild inflammatory cell response was associated with aerosol delivery of gentamicin and repeated bronchial lavage. Aerosol administration of gentamicin may have clinical use in the treatment of bacterial bronchopneumonia in horses. (Am J Vet Res 2000;61:1185–1190)

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in American Journal of Veterinary Research

Abstract

Objective—To investigate the effects of a continuous rate infusion (CRI) of dextrose solution or dextrose solution and insulin on glucose and insulin concentrations in healthy and endotoxin-exposed horses.

Animals—9 adult mares.

Procedures—During phase 1, treatments consisted of saline (0.9% NaCl) solution (control group; n = 4) or 20% dextrose solution (group 1; 4) administered IV as a 360-minute CRI. During phase 2, treatments consisted of 360-minute CRIs of 20% dextrose solution and insulin administered simultaneously at 367.6 mg/kg/h (30 kcal/kg/d) and 0.07 U/kg/h, respectively, in healthy horses (group 2; n = 4) or horses administered 35 ng of lipopolysaccharide/kg, IV, 24 hours before starting the dextrose solution and insulin CRIs (group 3; 4). A balanced crossover study design was used in both phases. Blood samples were collected for measurement of plasma glucose and insulin concentrations.

Results—Infusion of dextrose solution alone resulted in hyperglycemia for most of the 360-minute CRI. Insulin concentration increased significantly in group 1, compared with that in the control group. Mean insulin concentration of group 2 was significantly higher throughout most of the infusion period, compared with concentrations of the control group and group 1. Mean glucose concentration did not differ significantly between groups 2 and 3.

Conclusions and Clinical Relevance—Insulin infusion at a rate of 0.07 U/kg/h was found to be effective for the prevention of hyperglycemia when administered concurrently with dextrose solution. This rate was considered to be safe because horses did not become hypoglycemic during infusions of dextrose solution.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether a limited sampling time method based on serum iohexol clearance (Cliohexol) would yield estimates of glomerular filtration rate (GFR) in clinically normal horses similar to those for plasma creatinine clearance (Clcreatinine).

Animals—10 clinically normal adult horses.

Procedures—A bolus of iohexol (150 mg/kg) was administered IV, and serum samples were obtained 5, 20, 40, 60, 120, 240, and 360 minutes after injection. Urinary clearance of exogenous creatinine was measured during three 20-minute periods. The GFR determined by use of serum Cliohexol and plasma Clcreatinine was compared with limits of agreement plots.

Results—Values obtained for plasma Clcreatinine ranged from 1.68 to 2.69 mL/min/kg (mean, 2.11 mL/min/kg). Mean serum Cliohexol was 2.38 mL/min/kg (range, 1.95 to 3.33 mL/min/kg). Limits of agreement plots indicated good agreement between the methods.

Conclusions and Clinical Relevance—Use of serum Cliohexol yielded estimates of GFR in clinically normal adult horses similar to those for plasma Clcreatinine. This study was the first step in the evaluation of the use of serum Cliohexol for estimating GFR in adult horses.

Full access
in American Journal of Veterinary Research

Abstract

Case Description—13 equids (10 horses, 2 donkeys, and 1 pony) were examined for signs of colic (n = 7), weight loss (6), anorexia (3), and diarrhea (2). Ten equids were evaluated in the fall (September to November). Seven equids had a history of persimmon ingestion.

Clinical Findings—A diagnosis of phytobezoar caused by persimmon ingestion was made for all equids. Eight equids had gastric persimmon phytobezoars; 5 had enteric persimmon phytobezoars. Gastroscopy or gastroduodenoscopy revealed evidence of persimmon ingestion in 8 of 10 equids in which these procedures were performed.

Treatment and Outcome—2 of 13 equids were euthanatized prior to treatment. Supportive care was instituted in 11 of 13 equids, including IV administration of fluids (n = 8) and treatment with antimicrobials (5), NSAIDs (5), and gastric acid suppressants (4). Persimmon phytobezoar–specific treatments included dietary modification to a pelleted feed (n = 8); oral or nasogastric administration of cola or diet cola (4), cellulase (2), or mineral oil (2); surgery (4); and intrapersimmon phytobezoar injections with acetylcysteine (1). Medical treatment in 5 of 7 equids resulted in resolution of gastric persimmon phytobezoars. Seven of 8 equids with gastric persimmon phytobezoars and 1 of 5 equids with enteric persimmon phytobezoars survived > 1 year after hospital discharge.

Clinical Relevance—Historical knowledge of persimmon ingestion in equids with gastrointestinal disease warrants gastroduodenoscopy for evaluation of the presence of persimmon phytobezoars. In equids with gastric persimmon phytobezoars, medical management (including administration of cola or diet cola and dietary modification to a pelleted feed) may allow for persimmon phytobezoar dissolution.

Full access
in Journal of the American Veterinary Medical Association