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Abstract

Objective

To evaluate the effect on equine duodenal motility of some analgesic agents commonly used to treat colic.

Animals

4 healthy adult healthy horses—2 mares and 2 geldings—which were carrying an indwelling gastric cannula made of silastic rubber. One horse also carried 2 long-term indwelling bipolar electrodes that had been sutured onto the duodenum and jejunum.

Procedure

To ensure an empty stomach, solid food was withheld from horses for around 20 hours prior to an experiment. Using videoendoscopic guidance, an 8-F catheter with 3 small, discrete pressure sensors was passed through the gastric cannula and directed into the proximal portion of the duodenum. Deflection of the recording pen, to which the catheter was attached, indicated a motile event in that section. Drugs (treatment) were given into the jugular vein in a randomized block design, 1 treatment/experiment, after a 1-hour baseline recording. Treatments were: 2 ml of 0.9% NaCl, xylazine (XYL, 0.5 mg/kg of body weight), detomidine (DET, 0.0125 mg/kg), or a xylazine/butorphanol combination (XYB, 0.5/0.05 mg/kg). Each horse received each treatment twice. All positive pressure peaks > 5 mm of Hg recorded from the most proximal sensor on the catheter were counted in 15-minute blocks. Each mean 15-minute posttreatment value was compared with the baseline value for that specific treatment.

Results

There was no significant difference between baseline values. All treatments significantly (P < 0.05) reduced frequency of pressure peaks below their respective pretreatment values, but to variable degrees and durations. Comparatively, XYL had the least effect, with mild, though significant, reduction for only the first 30 posttreatment minutes; DET and XYB caused a significant marked reduction for 1 hour after treatment.

Conclusions

The profound suppressive effect of a routine dose of detomidine or xylazine/butorphanol combination on equine duodenal motility must be considered when using these agents for management of colic, especially when encouragement of intestinal motility is desirable. (Am J Vet Res 1998;59:619–623)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the origin of the nonacid (nonparietal) component of gastric secretions in horses induced by pentagastrin infusion.

Animals—6 horses.

Procedure—A Latin square design was used, involving 6 horses, 3 treatments, and 2 duodenal intubation conditions (catheter with balloon to obstruct pylorus [B] or without balloon allowing movement of contents between stomach and duodenum [NB]). Each horse had an indwelling gastric cannula and a catheter positioned in the duodenum. Gastric and duodenal contents were collected during 15-minute periods. Each experiment consisted of serial collection periods: baseline; infusion of pyrilamine maleate (1 mg/kg of body weight, IV); not treated; and IV infusion of saline (0.9% NaCl) solution alone, saline solution containing pentagastrin (6 µg/kg·h), or saline solution containing histamine (30 µg/kg·h). Volume of samples was recorded, and electrolyte concentrations were measured.

Results—Pentagastrin and histamine stimulated maximal acid output; however, during NB conditions, pentagastrin-induced concentration of hydrogen ions was significantly less than during histamine or pentagastrin infusions during B conditions. The large volume produced in response to pentagastrin during NB conditions was accompanied by increased sodium ion output that was greater than for pentagastrin during B conditions, but both values were significantly greater than values for histamine during B or NB conditions.

Conclusions and Clinical Relevance—Nonparietal secretions collected during IV infusion of pentagastrin are duodenal in origin. Reflux of duodenal contents into the stomach of horses is enhanced by pentagastrin. Flow of duodenal contents into the stomach could have implications in the pathogenesis of ulcers in horses. (Am J Vet Res 2000;61:1133–1139)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine gastric secretory responses in horses treated with histamine and to determine the dose of histamine needed to elicit maximal gastric secretion.

Animals

6 adult horses with an indwelling gastric cannula.

Procedure

Gastric contents were collected in 15-minute periods, and volume, pH, hydrogen ion concentration, hydrogen ion output, sodium concentration, and sodium output were determined. Values were determined without any treatment (baseline), after administration of pyrilamine maleate (1 mg/kg of body weight, IV, given during a 15-minute period), and during 1-hour infusions of histamine at 3 rates (7.5, 15, and 30 μg/kg/h, IV).

Results

Volume and hydrogen ion concentration of gastric contents and hydrogen ion output were significantly increased, compared with baseline values, during histamine infusion. Mean hydrogen ion concentration and hydrogen ion output were significantly greater during infusion of histamine at a rate of 15 or 30 μg/kg/h than at a rate of 7.5 μg/kg/h. Sodium concentration was significantly decreased, compared with baseline value, during histamine infusion, but sodium output was unchanged.

Conclusions

Histamine at doses of 15 and 30 μg/kg/h, IV stimulated maximal gastric secretion in horses. Histamine appeared to induce only parietal secretion.

Clinical Relevance

This study provides additional information related to equine gastric physiology, which may benefit further understanding of the pathogenesis of peptic ulcer disease. (Am J Vet Res 1998;59:1303–1306)

Free access
in American Journal of Veterinary Research

Objective

To assess the effect of aluminum hydroxide/magnesium hydroxide antacid and bismuth subsalicylate on gastric pH in clinically normal horses and to develop guidelines on the use of these agents for treatment of peptic ulcer disease in horses.

Design

Prospective, randomized, controlled trial.

Animals

5 clinically normal adult horses with chronically implanted gastric cannulas.

Procedure

Each horse received all 5 treatments (30 g of aluminum hydroxide/15 g of magnesium hydroxide, 12 g of aluminum hydroxide/6 g of magnesium hydroxide, 10.5 g of bismuth subsalicylate, 26.25 g of bismuth subsalicylate, and 5% methylcellulose control) with only 1 experiment performed each day. Gastric pH was measured via a glass electrode inserted through the gastric cannula for 1 hour before treatment and continued for 2 hours after treatment. Food or water was not given to the horses during the experiment. Measurements of gastric pH obtained during posttreatment hours were compared with pretreatment gastric pH values.

Results

Only a dose of 30 g of aluminum hydroxide/ 15 g of magnesium hydroxide resulted in a significant increase in gastric pH over baseline or control values. Mean pH was 5.2 ± 0.62 and 4.59 ± 0.48 for posttreatment hours 1 and 2, respectively.

Clinical Implications

Oral administration of 30 g of aluminum hydroxide/15 g of magnesium hydroxide to adult horses should result in a mean hourly gastric pH ≥ 4.0 for at least 2 hours. (J Am Vet Med Assoc 1996;208:1687-1691)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To better characterize the source of the large nonparietal secretory response to pentagastrin (PG) expressed in gastric contents of cannulated horses.

Animals

Adult cross-bred horses: 4 geldings and 1 mare.

Procedure

Horses were prepared by surgical insertion of a silastic gastric cannula from which gastric contents after feed was withheld could be continuously collected by gravity drainage. During experiments, the horses were lightly restrained in stocks, the gastric cannula was opened, and a catheter was inserted into a jugular vein. Over the next 5 hours, gastric contents were collected in 15-minute aliquots for which volume, pH, [Na+], and [K+] were measured. During the first hour, treatment was not administered. At the start of the second hour, either 0.5 mg of omeprazole (OME; dissolved in glycerol formal)/kg of body weight, or 0.9% NaCI (PSS) of comparable volume, was given IV at random as a bolus. At the start of the third hour, IV infusion of PG (6 µg/kg/h) was started and continued for the next 2 hours.

Results

The response to PG in the PSS-treated horses was similar to that previously seen-significant decrease in pH and increase in volume of gastric contents, and no change in [K+] and [Na+], but a modest volume-related increase in their respective outputs. After OME treatment, pH of the contents increased sharply and remained between 5 and 6 throughout PG infusion. Sodium concentration significantly increased after OME and virtually paralleled the pH response throughout the rest of the experiment; volume of gastric contents significantly increased in response to PG infusion and resulted in a significant increase in Na output. There was no change in K output in OME-treated animals.

Conclusions

PG induces a marked, nonparietal, secretory response into the gastric contents of cannulated horses. The volume and [Na+] of this response was maintained after pretreatment with OME, although the pH of the contents became basic, indicating that this nonparietal response is not mediated by an OME-sensitive proton pump. (Am J Vet Res 1996;57:1640–1644)

Free access
in American Journal of Veterinary Research