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Summary

Opsonized Rhodococcus equi activated the respiratory burst of resident alveolar macrophages (am) from adult horses in a logarithmic-linear, mass-related manner. The effect of R equi was not significantly different from that of equal masses of opsonized zymosan A. Therefore, R equi does not appear to attenuate the respiratory burst of equine am. The stimulatory effect of R equi was not reflected by increased production of superoxide anion (O2 -), but increased activity of the hexose monophosphate shunt was observed. These results suggest a similarity between the respiratory burst of am from horses and that of am from rabbits. We concluded that resident am from adult horses do not produce O2 - concurrently with an increase in activity of the hexose monophosphate shunt when stimulated with either opsonized zymosan A or opsonized R equi. This suggests that O2 - is not an important component of the antibacterial defenses of equine am. Whether equine am are incapable of producing O2 - or require different stimuli to produce it was not determined.

Free access
in American Journal of Veterinary Research

SUMMARY

Sodium salicylate was administered to cattle and goats iv and po according to a crossover design. Total urinary excretion of sa and its metabolites was measured for 3 days after dosing. Salicyluric acid (sua) was the only metabolite detected in urine of either species. Recovery of sodium salicylate and sua in goats amounted to 67.9 and 34.6% of the dose, respectively, after iv administration. After oral dosing, total recoveries were 30.2% (sodium salicylate) and 71.7%(sua) of dose. By comparison, cattle excreted significantly (P < 0.05) less sodium salicylate (54.0%) and more sua (49.9%) after iv dosing. The same pattern was observed after oral administration, wherein cattle excreted < 12% as sodium salicylate and more than 99% as sua. In both species, almost 90% of the drug excreted as sodium salicylate was found in urine within the first 12 hours after an iv dose and within 24 hours after oral dosing. The excretion of sua was somewhat slower in both species, especially after oral administration. The data suggested that there were only quantitative differences in the metabolism and elimination of sodium salicylate between the 2 species, with cattle excreting a higher proportion of the drug as the glycine conjugate sua.

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To determine the most repeatable method for evaluating right ventricular relaxation rate in horses and to determine and compare effects of isoflurane or halothane with and without the added influence of intravenously administered calcium gluconate on right ventricular relaxation rates in horses.

Animals

6 Thoroughbred horses from 2 to 4 years old.

Procedure

6 models (2 for monoexponential decay with zero asymptote, 3 for monoexponential decay with variable asymptote, and 1 for biexponential decay) for determining right ventricular relaxation rate were assessed in conscious and anesthetized horses. The 2 methods yielding the most repeatable results then were used to determine right ventricular relaxation rates in horses anesthetized with isoflurane or halothane before, during, and after IV administration of calcium gluconate. Right ventricular pressure was measured, using a catheter-tip high-fidelity pressure transducer, and results were digitized at 500 Hz from minimum rate of change in ventricular pressure.

Results

2 models that used monoexponential decay with zero asymptote repeatedly produced an estimate for relaxation rate and were used to analyze effects of anesthesia and calcium gluconate administration on relaxation rate. Isoflurane and halothane each prolonged right ventricular relaxation rate, with greater prolongation evident in halothane-anesthetized horses. Calcium gluconate attenuated the anesthesia-induced prolongation in right ventricular relaxation rate, with greater response obtained in isoflurane-anesthetized horses.

Conclusions and Clinical Relevance

Right ventricular relaxation rate in horses is assessed best by use of a monoexponential decay model with zero asymptote and nonlinear regression. Intravenous administration of calcium gluconate to isoflurane-anesthetized horses best preserves myocardial relaxant function. (Am J Vet Res 1999;60:872–879)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To evaluate the effects of halothane and isoflurane on cardiovascular function and serum total and ionized calcium concentrations in horses, and to determine whether administration of calcium gluconate would attenuate these effects.

Animals

6 clinically normal adult Thoroughbreds.

Procedure

Catheters were inserted for measurement of arterial blood pressures, pulmonary arterial blood pressures, right ventricular pressure (for determination of myocardial contractility), right atrial pressure, and cardiac output and for collection of arterial blood samples. Anesthesia was then induced with xylazine hydrochloride and ketamine hydrochloride and maintained with halothane or isoflurane. An IV infusion of calcium gluconate was begun 75 minutes after anesthetic induction; dosage of calcium gluconate was 0.1 mg/kg of body weight/min for the first 15 minutes, 0.2 mg/kg/min for the next 15 minutes, and 0.4 mg/kg/min for an additional 15 minutes. Data were collected before, during, and after administration of calcium gluconate.

Results

Halothane and isoflurane decreased myocardial contractility, cardiac index, and mean arterial pressure, but halothane caused greater depression than isoflurane. Calcium gluconate attenuated the anesthetic-induced depression in cardiac index, stroke index, and maximal rate of increase in right ventricular pressure when horses were anesthetized with isoflurane. When horses were anesthetized with halothane, a higher dosage of calcium gluconate was required to attenuate the depression in stroke index and maximal rate of increase in right ventricular pressure; cardiac index was not changed with calcium administration.

Conclusions and Clinical Relevance

IV administration of calcium gluconate may support myocardial function in horses anesthetized with isoflurane. (Am J Vet Res 1999;60:1430–1435)

Free access
in American Journal of Veterinary Research