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Abstract

Objective

To evaluate the efficacy of inhaled nitric oxide (NO) in anesthetized healthy newborn foals with experimentally induced pulmonary hypertension.

Animals

Five 1- to 3-day-old foals.

Procedure

Anesthesia was induced and maintained with propofol, and foals were intubated and mechanically ventilated. Systemic pressure and pulmonary arterial pressure (PPA) were recorded every 30 seconds. Hypertension was induced via a hypoxic gas mixture or chemical vasoconstriction, using the thromboxane mimetic U46619. Nitric oxide was added at a concentration of 80 parts per million (ppm) for 6 minutes under baseline conditions and during pulmonary hypertension-induced alveolar hypoxia (inspired oxygen concentration = 0.08). Nitric oxide (20, 40, 80, and 160 ppm) was evaluated during U46619-induced hypertension. Samples for determination of arterial blood gas tensions were collected before and after each NO treatment.

Results

Inhaled NO (approx 80 ppm) did not have an effect on baseline variables. Infusion of U46619 (0.35 ± 0.04 μg/kg of body weight/min) or alveolar hypoxia resulted in increased PPA and decreased arterial oxygenation (Pao2) and hemoglobin saturation (HbSat). The increase in PPA was attenuated, in a dose-dependent manner, by NO during U46619 infusion and reversed by NO during induced hypoxemia. The Pao2 and HbSat were significantly improved at all NO doses during U44619 infusion but not during alveolar hypoxia. For all inhaled NO concentrations, nitrogen dioxide and methoglobin values were < 5 ppm and 3%, respectively.

Conclusions and Clinical Relevance

Nitric oxide is a potent, selective vasodilator of the pulmonary circulation in healthy newborn foals. Inhaled NO may have value as a therapeutic agent in foals with pulmonary hypertension. (Am J Vet Res 1999;60:1207–1212)

Free access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

SUMMARY

Extracellular myoelectric activity from the terminal ileum cecum, and colonic pelvic flexure was assessed in 4 adult horses. The collection and analysis of myoelectric data involved the development and use of a computer-based system. After collection, the myoelectric signal was digitally filtered to enhance the activity of interest. The smoothed signal was then processed by use of computer programs designed to identify and count spike-burst activity and estimate burst duration. The intense phases of myoelectric complexes also were identified. The propagation of myoelectric spike-burst activity was assessed over 3 electrode sites to identify the propagative patterns of intestinal motility. There was high correlation between the results of computer-based analysis and those of visual analysis. We concluded that the computer provides a fast, accurate, and reliable means of assessing myoelectric activity.

Free access
in American Journal of Veterinary Research

SUMMARY

Myoelectric activity was monitored from the terminal ileum, cecum, and colonic pelvic flexure by use of Ag-pAgCl bipolar electrodes in 4 adult horses before, during, and after general anesthesia. Horses were anesthetized by way of 3 commonly used regimens, including xylazine (1.1 mg/kg of body weight) and ketamine hydrochloride (2.2 mg/kg); thiopental sodium (7.7 mg/kg), followed by halothane vaporized in oxygen; and thiopental sodium (2.5 g) in guaifenesin (100 mg/ml) solution given to effect, followed by halothane in oxygen. All 3 anesthetic regimens decreased intestinal spike-burst activity in the areas monitored. The slowest return to preanesthetic myoelectric activity was observed after xylazine and ketamine administration. After both of the barbiturate/halothane anesthetic regimens, there was a rebound increase in spike-burst frequency, without alteration in the proportion of propagative myoelectric events. All 3 anesthetic regimens appeared to reset the timing of the small and large intestinal migrating myoelectric complexes. By 9 hours after recovery from anesthesia, the effects of anesthesia, irrespective of regimen, had disappeared. Although anesthesia significantly (P < 0.05) altered intestinal myoelectric activity, no particular anesthetic regimen had a prolonged effect. Results of our study indicate that the particular chosen regimen of general anesthesia is unimportant in development of motility disturbances in horses after anesthesia.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate the prokinetic effect of bethanechol and erythromycin in the upper gastrointestinal tract of healthy horses by measuring the gastric emptying (GE) rate of a radioactive meal.

Animals

4 healthy adult horses.

Procedure

After food was withheld for 12 hours, horses were given 370 MBq of 99mTc-labeled sulfur colloid incorporated into egg albumen and 37 MBq of 111In-labeled diethyltriaminepentaacetic acid in 120 ml of water via nasogastric intubation. Intravenously administered treatments were 0.9% NaCl solution, erythromycin (0.1 or 1.0 mg/kg of body weight), or bethanechol (0.25 mg/kg). All drugs were given in 10 ml of 0.9% NaCl solution. Dualphase scintigraphic images were obtained by use of a gamma camera. The best-fit function was determined for each study, and the resultant curves were then analyzed by use of least squares nonlinear regression. Two variables, time to 50% emptying of the stomach (T-50) and slope of the emptying curve, were derived from the calculated power exponential equation.

Conclusions

Treatment had a significant (P < 0.05) overall effect on T-50 of solid-phase GE. The T-50 of bethanechol (30.09 ± 10.01 minutes), erythromycin at 0.1 mg/kg (59.08 ± 10.01 minutes), and erythromycin at 1 mg/kg (60.50 ± 10.01 minutes) were significantly shorter than T-50 after saline administration (89.97 ± 10.01 minutes). There was a trend (P = 0.09) for the slope of solid-phase GE of bethanechol and erythromycin (0.1 mg/kg; P = 0.37) to be steeper than that of saline solution. For liquid-phase GE, the T-50 and the slope of bethanechol differed significantly (P < 0.05) from those for saline solution.

Clinical Relevance

Bethanechol and erythromycin significantly increased solid-phase GE in healthy horses and may have value for use as prokinetic agents in certain gastrointestinal tract diseases. (Am J Vet Res 1996;57:1771–1775)

Free access
in American Journal of Veterinary Research

Summary

Effects of a change from a diet composed primarily of forage to a diet composed primarily of concentrate on abomasal antral and duodenal motility were assessed in 5 lactating Holstein cows. Antroduodenal motility was measured by use of 8 silver electrodes sutured to the abomasum and duodenum, and abomasal emptying was assessed by continuous measurement of intraduodenal pH. Both diets were fed to achieve a daily dry matter intake of 2.7 kg/100 kg of body weight. The abrupt change in diet did not alter antroduodenal myoelectric activity or abomasal emptying. Initiation of phase III of the migrating myoelectric complex in the proximal portion of the duodenum corresponded with a decrease in abomasal antral spiking activity and an increase in intraduodenal pH. Results suggest that a high concentrate diet alone does not adversely affect antroduodenal motility in adult dairy cattle.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether particular vaccine brands, other injectable medications, customary vaccination practices, or various host factors were associated with the formation of vaccine-associated sarcomas in cats.

Design—Prospective multicenter case-control study.

Animals—Cats in the United States and Canada with soft tissue sarcomas or basal cell tumors.

Procedure—Veterinarians submitting biopsy specimens from cats with a confirmed diagnosis of soft tissue sarcoma or basal cell tumor were contacted for patient medical history. Time window statistical analyses were used in conjunction with various assumptions about case definitions.

Results—No single vaccine brand or manufacturer within antigen class was found to be associated with sarcoma formation. Factors related to vaccine administration were also not associated with sarcoma development, with the possible exception of vaccine temperature prior to injection. Two injectable medications (long-acting penicillin and methyl prednisolone acetate) were administered to case cats more frequently than to control cats.

Conclusions and Clinical Relevance—Findings do not support the hypotheses that specific brands or types of vaccine within antigen class, vaccine practices such as reuse of syringes, concomitant viral infection, history of trauma, or residence either increase or decrease the risk of vaccineassociated sarcoma formation in cats. There was evidence to suggest that certain long-acting injectable medications may also be associated with sarcoma formation. (J Am Vet Med Assoc 2003;223:1283–1292)

Full access
in Journal of the American Veterinary Medical Association