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Summary

The effects of short-term phenobarbital administration were evaluated in 6 adult mixed-breed dogs that received phenobarbital (5 mg/kg of body weight, PO, q 12 h) for 8 consecutive weeks. Six additional dogs served as untreated controls. At 2-week intervals, endogenous adrenocorticotropic hormone (ACTH) concentration and cortisol concentration before and 2 hours after administration of porcine aqueous ACTH (2.2 IU/kg, M) were measured. By means of oneway ANOVA, we were not able to detect a significant (P ≥ 0.05) difference in endogenous ACTH concentration and cortisol concentration before and after exogenous ACTH administration within groups over time or between groups at any time.

To evaluate effects of long-term phenobarbital administration, sera and plasma were collected from 5 epileptic dogs that had received phenobarbital for > 2 years and had serum phenobarbital concentrations > 20 μg/dl. Endogenous ACTH concentration and cortisol concentration, before and after administration of ACTH, were within established reference ranges for all 5 dogs.

Together, these results suggest that phenobarbital administration alone does not affect endogenous ACTH concentration or response to exogenous ACTH administration in dogs, and that these may be valid screening tests for hyperadrenocorticism in most dogs receiving phenobarbital.

Free access
in Journal of the American Veterinary Medical Association

Summary

Observations made during endoscopic evaluation of the stomach, duodenum, and colon of 58 dogs and 17 cats with a history of regurgitation, vomiting, and/or diarrhea were compared with results of histologic examination of tissues obtained during the procedures. Endoscopic observations included normal mucosa, alternations in mucosal color and texture, and luminal masses. Although endoscopy alone is a useful technique for detecting alterations of the gastrointestinal mucosa, histologic assessment of tissues obtained is necessary to confirm either an inflammatory or a neoplastic process.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

Modification of gastroduodenal motility has been proposed to aid endoscopic examination of the duodenum in dogs. The objective of this study was to evaluate the use of the following pharmacologic agents for facilitation of endoscopic intubation of the duodenum in 6 clinically normal dogs: metoclopramide HCl (0.2 mg/kg of body weight), atropine sulfate (0.045 mg/kg), glucagon (0.06 mg/kg), and isotonic saline solution.

In a randomized, blinded, crossover design, the ease of endoscopic duodenal intubation was qualitatively scored by 3 endoscopists (in random order), using the following scale: immediate entry; rapid entry—moderate manipulation; difficult entry—multiple attempts; and no entry after 2 minutes. Anesthesia was induced with thiopental and maintained with halothane. The 4 agents were diluted to a fixed volume and randomly administered. Duodenal intubation was attempted 2 minutes after iv injection of 1 of the agents. Four endoscopic procedures (1 for each agent) were performed on each dog with a minimum of 5 days between each procedure.

In this study, no agent facilitated endoscopic duodenal intubation at the dose used. Instead, atropine and metoclopramide made duodenal intubation significantly more difficult, compared with use of saline solution. Difference between intubation after administration of glucagon and saline solution was not seen. On the basis of our findings, the use of these agents for facilitating endoscopic duodenal intubation is not recommended.

In addition, in this study, we found that experience in endoscopic intubation is an important factor in determining the ease of duodenal intubation.

Free access
in American Journal of Veterinary Research

Summary

The purposes of this study were to evaluate the efficacy of metoclopramide to aid passage of a flexible endoscope into the duodenum of dogs, and to determine whether the effect of metoclopramide is dependent on dose. In a randomized, blinded, complete-block design, 6 healthy dogs were anesthetized, then each was given saline solution or 1 of 4 doses of metoclopramide on different days. The - ease of passage of a flexible, fiberoptic gastroscope through the pylorus was assessed independently by 3 endoscopists.

Administration of metoclopramide hydrochloride at a dosage of 0.4 mg/kg of body weight, iv, made passage of a flexible endoscope into the duodenum significantly (P= 0.009) more difficult than when, saline solution was administered; however, dosages of 0.1, 0.2 and 0.8 mg of metoclopramide/kg did not (P = 0.489, 0.842, and 0.092 respectively). It was concluded that metoclopramide did not facilitate, and at one dosage hindered, successful passage of a flexible endoscope into the duodenum of healthy dogs under the conditions of the study. Metoclopramide, therefore, cannot be recommended as an aid for passage of a flexible endoscope into the duodenum of dogs.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of hypothyroidism on insulin sensitivity, glucose tolerance, and concentrations of hormones counter-regulatory to insulin in dogs.

Animals—8 anestrous mixed-breed bitches with experimentally induced hypothyroidism and 8 euthyroid control dogs.

Procedures—The insulin-modified frequently sampled IV glucose tolerance test and minimal model analysis were used to determine basal plasma insulin and glucose concentrations, acute insulin response to glucose, insulin sensitivity, glucose effectiveness, and disposition index. Growth hormone response was assessed by stimulation and suppression tests. Additionally, basal serum growth hormone (GH) and insulin-like growth factor-1 (IGF-1) concentrations and urine cortisol-to-creatinine concentration ratios were measured and dual energy x-ray absorptiometry was performed to evaluate body composition.

Results—Insulin sensitivity was lower in the hypothyroid group than in the euthyroid group, whereas acute insulin response to glucose was higher. Glucose effectiveness and disposition index were not different between groups. Basal serum GH and IGF-1 concentrations as well as abdominal fat content were high in hypothyroid dogs, but urine cortisol-to-creatinine concentration ratios were unchanged.

Conclusions and Clinical Relevance—Hypothyroidism appeared to negatively affect glucose homeostasis by inducing insulin resistance, but overall glucose tolerance was maintained by increased insulin secretion in hypothyroid dogs. Possible factors affecting insulin sensitivity are high serum GH and IGF-1 concentrations and an increase in abdominal fat. In dogs with diseases involving impaired insulin secretion such as diabetes mellitus, concurrent hypothyroidism can have important clinical implications.

Full access
in American Journal of Veterinary Research