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Carroll, G. L., Matthews, N. S., Hartsfield, S. M., Slater, M. R., Champney, T. H., & Erickson, S. W. (1997). The effect of detomidine and its antagonism with tolazoline on stress-related hormones, metabolites, physiologic responses, and behavior in awake ponies. Vet Surg, 26(1), 69–77.
Abstract: Six ponies were used to investigate the effect of tolazoline antagonism of detomidine on physiological responses, behavior, epinephrine, norepinephrine, cortisol, glucose, and free fatty acids in awake ponies. Each pony had a catheter inserted into a jugular vein 1 hour before beginning the study. Awake ponies were administered detomidine (0.04 mg/kg intravenously [i.v.]) followed 20 minutes later by either tolazoline (4.0 mg/kg i.v.) or saline. Blood samples were drawn from the catheter 5 minutes before detomidine administration (baseline), 5 minutes after detomidine administration, 20 minutes before detomidine administration which was immediately before the administration of tolazoline or saline (time [T] = 0), and at 5, 30, and 60 minutes after injections of tolazoline or saline (T = 5, 30, and 60 minutes, respectively). Compared with heart rate at T = 0, tolazoline antagonism increased heart rate 45% at 5 minutes. There was no difference in heart rate between treatments at 30 minutes. Blood pressure remained stable after tolazoline, while it decreased over time after saline. Compared with concentrations at T = 0, tolazoline antagonism of detomidine in awake ponies resulted in a 55% increase in cortisol at 30 minutes and a 52% increase in glucose at 5 minutes. The change in free fatty acids was different for tolazoline and saline over time. Free fatty acids decreased after detomidine administration. Free fatty acids did not change after saline administration. After tolazoline administration, free fatty acids increased transiently. Tolazoline tended to decrease sedation and analgesia at 15 and 60 minutes postantagonism. Antagonism of detomidine-induced physiological and behavioral effects with tolazoline in awake ponies that were not experiencing pain appears to precipitate a stress response as measured by cortisol, glucose, and free fatty acids. If antagonism of an alpha-agonist is contemplated, the potential effect on hormones and metabolites should be considered.
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Grubb, T. L., Foreman, J. H., Benson, G. J., Thurmon, J. C., Tranquilli, W. J., Constable, P. D., et al. (1996). Hemodynamic effects of calcium gluconate administered to conscious horses. J Vet Intern Med, 10(6), 401–404.
Abstract: Calcium gluconate was administered to conscious horses at 3 different rates (0.1, 0.2, and 0.4 mg/kg/min for 15 minutes each). Serum calcium concentrations and parameters of cardiovascular function were evaluated. All 3 calcium administration rates caused marked increases in both ionized and total calcium concentrations, cardiac index, stroke index, and cardiac contractility (dP/dtmax). Mean arterial pressure and right atrial pressure were unchanged; heart rate decreased markedly during calcium administration. Ionized calcium concentration remained between 54% and 57% of total calcium concentration throughout the study. We conclude that calcium gluconate can safely be administered to conscious horses at 0.1 to 0.4 mg/kg/min and that administration will result in improved cardiac function.
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Williams, D. O., Boatwright, R. B., Rugh, K. S., Garner, H. E., & Griggs, D. M. J. (1991). Myocardial blood flow, metabolism, and function with repeated brief coronary occlusions in conscious ponies. Am J Physiol, 260(1 Pt 2), H100–9.
Abstract: Studies were performed in the conscious pony instrumented with a Doppler flow probe and hydraulic occluder on the left anterior descending coronary artery (LAD), sonomicrometry crystals and intraventricular micromanometer in the left ventricle, and catheters in the left atrium and anterior interventricular vein. Two-minute LAD occlusions were performed every 30 min continuously or during working hours. Data on release of catabolites (potassium, hydrogen ions, and lactate) and norepinephrine from the initially dysfunctional region were obtained periodically during a regimen of 445 +/- 56 occlusions in six animals. Regional myocardial blood flow was measured (microsphere method) before and after an occlusion regimen in four animals. Marked release of catabolites and norepinephrine from the initially dysfunctional region was noted in association with early occlusions when myocardial segment function was severely reduced. With further occlusions, release of these substances decreased while segment function improved. Blood flow was markedly decreased in the initially dysfunctional region during an early occlusion but was at the control level during a later occlusion. Although the metabolic findings are consistent with protection due to “ischemic preconditioning” and no increase in collateral perfusion, the inverse relationship noted between catabolite release and segment function is best explained by flow-dependent mechanisms. These results, together with the myocardial blood flow data, serve to validate a previous assumption that protection against regional myocardial dysfunction under these conditions is due to increased collateral perfusion.
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Forster, H. V., Pan, L. G., Bisgard, G. E., Flynn, C., & Hoffer, R. E. (1985). Changes in breathing when switching from nares to tracheostomy breathing in awake ponies. J Appl Physiol, 59(4), 1214–1221.
Abstract: We assessed the consequences of respiratory unloading associated with tracheostomy breathing (TBr). Three normal and three carotid body-denervated (CBD) ponies were prepared with chronic tracheostomies that at rest reduced physiological dead space (VD) from 483 +/- 60 to 255 +/- 30 ml and lung resistance from 1.5 +/- 0.14 to 0.5 +/- 0.07 cmH2O . l-1 . s. At rest and during steady-state mild-to-heavy exercise arterial PCO2 (PaCO2) was approximately 1 Torr higher during nares breathing (NBr) than during TBr. Pulmonary ventilation and tidal volume (VT) were greater and alveolar ventilation was less during NBr than TBr. Breathing frequency (f) did not differ between NBr and TBr at rest, but f during exercise was greater during TBr than during NBr. These responses did not differ between normal and CBD ponies. We also assessed the consequences of increasing external VD (300 ml) and resistance (R, 0.3 cmH2O . l-1 . s) by breathing through a tube. At rest and during mild exercise tube breathing caused PaCO2 to transiently increase 2-3 Torr, but 3-5 min later PaCO2 usually was within 1 Torr of control. Tube breathing did not cause f to change. When external R was increased 1 cmH2O . l-1 . s by breathing through a conventional air collection system, f did not change at rest, but during exercise f was lower than during unencumbered breathing. These responses did not differ between normal, CBD, and hilar nerve-denervated ponies, and they did not differ when external VD or R were added at either the nares or tracheostomy.(ABSTRACT TRUNCATED AT 250 WORDS)
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Weik, H., Lingk, W., & Altmann, H. J. (1972). [Behavior of individual fatty acids during in-vitro lipolysis and resynthesis in equine depot fat]. Zentralbl Veterinarmed A, 19(8), 677–685.
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Weik, H., & Altmann, J. (1972). The effect of L(+)-lactate on rat and horse adipose tissue in vitro. Zentralbl Veterinarmed A, 19(6), 514–518.
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Altmann, H. J., & Weik, H. (1971). [Serum fatty acid patterns of phospholipid fractions in horses]. Z Tierphysiol Tierernahr Futtermittelkd, 28(5), 285–288.
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Weik, H., & Altmann, H. J. (1971). [Behavior of blood lipids during fasting in the horse]. Zentralbl Veterinarmed A, 18(2), 131–138.
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Altmann, H. J., Hertel, J., & Drepper, K. (1970). [Nutritional physiology of the horse. 3. Protein values in the gastrointestinal tract of slaughtered horses]. Z Tierphysiol Tierernahr Futtermittelkd, 26(5), 245–252.
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Hertel, J., Altmann, H. J., & Drepper, K. (1970). [Nutritional physiology studies of the horse. II. Raw nutrient studies of the gastrointestinal tract of slaughtered horses]. Z Tierphysiol Tierernahr Futtermittelkd, 26(3), 169–174.
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