Systemic Vascular Resistance (SVR) refers to the resistance offered by the systemic blood vessels to the flow of blood in horses. It is an important physiological parameter that influences blood pressure and cardiac workload. SVR is determined by factors such as vessel diameter, blood viscosity, and overall vascular tone. In equine medicine, understanding SVR is essential for assessing cardiovascular function and diagnosing potential disorders. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, measurement, and implications of systemic vascular resistance in equine health and disease.
Garcia Filho SG, de Andrade FSRM, Dos Santos RST, Gonçalves LA, Pereira MAA, de Souza AF, Ambrósio AM, Fantoni DT.The objective of this study was to compare the hemodynamic effects of dobutamine and ephedrine during the management of anesthesia-related hypotension in healthy horses. Thirteen horses underwent general anesthesia with isoflurane and were randomly divided into two different groups, one of which received a dobutamine constant rate infusion (CRI) (1 µg/kg bwt/min) and the other received an ephedrine CRI (20 µg/kg bwt/min) when hypotension (<60 mmHg) was identified, following up to 15 min after the blood pressure reached 70 mmHg. All horses were equipped with a pulmonary artery catheter and a ...
Schnuelle ML, Hopster K, Toribio RE, Hurcombe SD.To compare the effects of 7.2% hypertonic and 0.9% isotonic saline (sodium chloride) solutions on cardiovascular parameters and plasma arginine vasopressin (AVP) concentrations in healthy, isoflurane-anesthetized horses. Methods: 8 healthy horses. Methods: In a prospective, randomized, crossover study, horses were anesthetized with isoflurane twice with a 14-day washout period between anesthetic episodes. While anesthetized, horses received a bolus (4 mL/kg) of 7.2% hypertonic saline solution (HS) or 0.9% isotonic saline solution (IS). Heart rate; systolic, mean, and diastolic arterial blood p...
Meier M, Bettschart-Wolfensberger R, Schwarzwald CC, Portier K, Gysler A, Ringer SK.Dobutamine is routinely used to improve cardiovascular function in anaesthetized horses. However, dobutamine in conscious horses is insufficiently investigated. Ten research horses that were already instrumented for a preceding trial were included into the study. Cardiovascular variables were recorded and blood samples taken after instrumentation (Baseline), before starting dobutamine and after 10 min of dobutamine infusion (2 µg kg min ). A significant increase in systemic blood pressure, mean pulmonary artery pressure and right atrial pressure, and a decrease in heart rate were observe...
Jones T, Bracamonte JL, Ambros B, Duke-Novakovski T.To evaluate effects of anesthesia induced with alfaxalone and maintained with alfaxalone, dexmedetomidine and remifentanil infusions in foals. Methods: Prospective, experimental study. Methods: A group of six healthy foals [median (range) 11 (8-33) days] undergoing abdominal surgery. Methods: Intravenous (IV) dexmedetomidine (3-7μgkg) provided sedation for insertion of a pulmonary artery catheter. IV anesthesia was induced with alfaxalone (2mgkg) and maintained with alfaxalone (6mgkghour), dexmedetomidine (1μgkghour) and remifentanil (3μgkghour). Foals were endotracheally intubated and lung...
Wittenberg-Voges L, Kästner SB, Raekallio M, Vainio OM, Rohn K, Hopster K.To compare the effects of MK-467 during isoflurane anaesthesia combined with xylazine or dexmedetomidine on global and gastrointestinal perfusion parameters. Methods: Prospective, randomized experimental trial. Methods: A total of 15 warmblood horses. Methods: Horses were divided into two groups for administration of either dexmedetomidine (D) or xylazine (X) for premedication (D: 3.5 μg kg; X: 0.5 mg kg) and as constant rate infusion during isoflurane anaesthesia (D: 7 μg kg hour; X: 1 mg kg hour). During anaesthesia, heart rate, mean arterial blood pressure (MAP), systemic vascular resista...
Ohta M, Kurimoto S, Ishikawa Y, Tokushige H, Mae N, Nagata S, Mamada M.To determine dose-dependent cardiovascular effects of dobutamine and phenylephrine during anesthesia in horses, increasing doses of dobutamine and phenylephrine were infused to 6 healthy Thoroughbred horses. Anesthesia was induced with xylazine, guaifenesin and thiopental and maintained with sevoflurane at 2.8% of end-tidal concentration in all horses. The horses were positioned in right lateral recumbency and infused 3 increasing doses of dobutamine (0.5, 1.0 and 2.0 µg/kg/min) for 15 min each dose. Following to 30 min of reversal period, 3 increasing doses of phenylephrine (0.25, 0.5 and 1....
Fantoni DT, Marchioni GG, Ida KK, Belo JN, Zoppa AL, Silva LC, Ambrósio AM.To assess the cardiopulmonary effects of ephedrine and phenylephrine for management of isoflurane-induced hypotension in horses. Methods: Prospective randomized clinical study. Methods: Fourteen isoflurane-anesthetized horses undergoing digital palmar neurectomy. Methods: Ephedrine (EPH group; 0.02 mg kg(-1) minute(-1); n = 7) or phenylephrine (PHE group; 0.002 mg kg(-1) minute(-1); n = 7) was administered to all horses when mean arterial pressure (MAP) was <60 mmHg. The infusions were ended when the target MAP was achieved, corresponding to a 50% increase over the pre-infusion MAP (baseline)....
Ohta M, Kurimoto S, Tokushige H, Kuroda T, Ishikawa Y.To determine hemodynamic effects of hydroxyethyl starch (HES) infusion during anesthesia in horses, incremental doses of 6% HES were administered to 6 healthy Thoroughbred horses. Anesthesia was induced with xylazine, guaifenesin and thiopental and maintained with sevoflurane at 2.8% of end-tidal concentration in all horses. The horses were positioned in right lateral recumbency and administered 3 intravenous dose of 6% HES (5 ml/kg) over 15 min with 15-min intervals in addition to constant infusion of lactated Ringer's solution at 10 ml/kg/hr. Hemodynamic parameters were measured before and e...
Hollis AR, Ousey JC, Palmer L, Stephen JO, Stoneham SJ, Boston RC, Corley KT.Norepinephrine increases arterial blood pressure but may have adverse effects on renal blood flow. Fenoldopam, a dopamine-1 receptor agonist, increases urine output in normotensive foals. The combination of norepinephrine and fenoldopam may lead to improved renal perfusion compared with an infusion of norepinephrine alone. The combined effects of these drugs have not been reported in the horse. Objective: Norepinephrine will alter the hemodynamic profile of foals without affecting renal function. Addition of fenoldopam will change the renal profile during the infusions without changing the hem...
Hollis AR, Ousey JC, Palmer L, Stoneham SJ, Corley KT.Norepinephrine is a potent vasopressor that increases arterial blood pressure but may have adverse effects on renal blood flow. The combination of norepinephrine and dobutamine may lead to improved renal perfusion compared to an infusion of norepinephrine alone. The effects of these drugs in the normotensive neonatal foal have not been reported. Objective: Norepinephrine increases arterial blood pressure. Adding dobutamine to a norepinephrine infusion will change the renal profile during the infusions without changing the arterial blood pressure. Methods: Eight conscious Thoroughbred foals wer...
Durongphongtorn S, McDonell WN, Kerr CL, Neto FJ, Mirakhur KK.To compare hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of halothane and isoflurane in horses undergoing arthroscopic surgery. Methods: 8 healthy adult horses. Methods: Anesthesia was maintained with isoflurane or halothane (crossover study). At 6 intervals during anesthesia and surgery, cardiopulmonary variables and related derived values were recorded. Recovery from anesthesia was assessed; gastrointestinal tract motility was subjectively monitored for 72 hours after anesthesia. Horses were administered chromium, and fecal chromium concen...
Kushiro T, Yamashita K, Umar MA, Maehara S, Wakaiki S, Abe R, Seno T, Tsuzuki K, Izumisawa Y, Muir WW.The anesthetic sparring and cardiovascular effects produced by midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.05 mg/ml (0.025 ml/kg/hr) drug infusion during sevoflurane in oxygen (MKM-OS) anesthesia was determined in healthy horses. The anesthetic sparring effects of MKM-OS were assessed in 6 healthy thoroughbred horses in which the right carotid artery was surgically relocated to a subcutaneous position. All horses were intubated and ventilated with oxygen using intermittent positive pressure ventilation (IPPV). The end-tidal concentration of sevoflurane (ET(SEV)) required to maintain s...
Latimer FG, Eades SC, Pettifer G, Tetens J, Hosgood G, Moore RM.Abdominal insufflation is performed routinely during laparoscopy in horses to improve visualisation and facilitate instrument and visceral manipulations during surgery. It has been shown that high-pressure pneumoperitoneum with carbon dioxide (CO2) has deleterious cardiopulmonary effects in dorsally recumbent, mechanically ventilated, halothane-anaesthetised horses. There is no information on the effects of CO2 pneumoperitoneum on cardiopulmonary function and haematology, plasma chemistry and peritoneal fluid (PF) variables in standing sedated horses during laparoscopic surgery. Objective: To ...
Bettschart-Wolfensberger R, Bowen MI, Freeman SL, Feller R, Bettschart RW, Nolan A, Clarke KW.To determine cardiopulmonary effects of total IV anesthesia with propofol and medetomidine in ponies and effect of atipamezole on recovery. Methods: 10 ponies. Methods: After sedation was induced by IV administration of medetomidine (7 microg/kg of body weight), anesthesia was induced by IV administration of propofol 12 mg/kg) and maintained for 4 hours with infusions of medetomidine (3.5 microg/kg per hour) and propofol 10.07 to 0.11 mg/kg per minute). Spontaneous respiration was supplemented with oxygen. Cardiopulmonary measurements and blood concentrations of propofol were determined during...
Raisis AL, Young LE, Taylor PM, Walsh KP, Lekeux P.To use Doppler ultrasonography and single-fiber laser Doppler flowmetry (LDF) to evaluate blood flow in the dependent and nondependent hind limbs of anesthetized horses and to evaluate changes in femoral arterial blood flow and microvascular skeletal muscle perfusion in response to administration of phenylephrine hydrochloride or dobutamine hydrochloride. Methods: 6 healthy adult horses. Methods: Horses were anesthetized and positioned in left lateral recumbency. Doppler ultrasonography was used to measure velocity and volumetric flow in the femoral vessels. Single-fiber LDF was used to measur...
Tetens J, Bueno AC, Cornick-Seahorn JL, Hosgood G, Eades SC, Moore RM.To determine hemodynamic and metabolic effects of IV infusion of ATP-MgCl2 combination and maximal safe IV infusion rate in conscious horses. Methods: 6 adult female horses. Methods: All horses received an IV infusion of ATP-MgCl2 combination, beginning at a rate of 0.05 mg of ATP/kg of body weight/min, which was increased by 0.05 mg/kg/min increments at 10-minute intervals until a rate of 1.0 mg/kg/min was achieved. Data were collected prior to the start of the infusion, at the end of each infusion rate, and at 15-minute intervals for the next hour after discontinuation of the infusion. Measu...
Brodbelt DC, Harris J, Taylor PM.This study investigated whether maintenance of normotension using a methoxamine infusion would prevent activation of the stress response during halothane anaesthesia in ponies. After acepromazine premedication, anaesthesia was induced with thiopentone in six ponies, and maintained for 120 minutes with halothane in oxygen and ventilation to normocapnia. Methoxamine (M, 0.013+/-0.005 mg kg(-1) min(-1)) or saline (C) was infused throughout anaesthesia. Sequential blood samples were taken for cortisol and ACTH assay. During anaesthesia normotension (mean arterial blood pressure 101-124 mm Hg) was ...
Geimer TR, Ekström PM, Ludders JW, Erichsen DF, Gleed RD.The haemodynamic effects of hyoscine-N-butylbromide (0.30 mg/kg, intravenously) were studied in eight adult ponies in a blinded two-period crossover experiment with repeated measures. Values for heart rate were 63%, 48% and 13% greater than control values at 1, 16 and 46 min, respectively, after administration of hyoscine-N-butylbromide. Cardiac output increased by 16% at 16 min after drug injection. Mean right atrial pressure was decreased by 79%, 63%, 45% and 52% at 1, 16, 46 and 61 min, respectively, after drug administration. Stroke volume was decreased by 32% at 1 min and pulmonary arteri...
Wagner AE, Dunlop CI, Wertz EM, Chapman PL, Baxter GM, Klopp LS.Seven horses, which were part of an investigation of the effect of endotoxin administration on vascular reactivity, were anesthetized on two separate occasions for surgical excision of 4-cm sections of palmar digital artery and vein. On the first occasion, the horses were given an infusion of 1 L 0.9% NaCl solution intravenously (i.v.) just before induction of anesthesia (control); on the second occasion, the horses received an infusion of 1 L 0.9% NaCl containing Escherichia coli endotoxin, 0.1 microgram/kg (endotoxin). On both occasions, anesthesia was induced with xylazine, guaifenesin, and...
Daunt DA, Dunlop CI, Chapman PL, Shafer SL, Ruskoaho H, Vakkuri O, Hodgson DS, Tyler LM, Maze M.Cardiopulmonary and behavioral responses to detomidine, a potent alpha 2-adrenergic agonist, were determined at 4 plasma concentrations in standing horses. After instrumentation and baseline measurements in 7 horses (mean +/- SD for age and body weight, 6 +/- 2 years, and 531 +/- 48.5 kg, respectively), detomidine was infused to maintain 4 plasma concentrations: 2.1 +/- 0.5 (infusion 1), 7.2 +/- 3.5 (infusion 2), 19.1 +/- 5.1. (infusion 3), and 42.9 +/- 10 (infusion 4) ng/ml, by use of a computer-controlled infusion system. Detomidine caused concentration-dependent sedation and somnolence. The...
Hinchcliff KW, McKeever KH, Muir WW.The authors investigated the cardiovascular effects of low doses of nitroprusside, dobutamine, and phenylephrine and a beta-adrenergic blocking dose of propranolol in conscious, healthy horses with and without prior atropine administration. A parasympathetic blocking dose of atropine produced significant increases in heart rate and arterial pressures, and decreased stroke volume, ejection fraction, pulse pressure, and right-ventricular end-diastolic pressure and volume. Cardiac output was not changed by atropine administration. Nitroprusside reduced arterial pressures to a greater extent in at...
Latimer FG, Eades SC, Pettifer G, Tetens J, Hosgood G, Moore RM.Abdominal insufflation is performed routinely during laparoscopy in horses to improve visualisation and facilitate instrument and visceral manipulations during surgery. It has been shown that high-pressure pneumoperitoneum with carbon dioxide (CO2) has deleterious cardiopulmonary effects in dorsally recumbent, mechanically ventilated, halothane-anaesthetised horses. There is no information on the effects of CO2 pneumoperitoneum on cardiopulmonary function and haematology, plasma chemistry and peritoneal fluid (PF) variables in standing sedated horses during laparoscopic surgery. Objective: To ...
Durongphongtorn S, McDonell WN, Kerr CL, Neto FJ, Mirakhur KK.To compare hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of halothane and isoflurane in horses undergoing arthroscopic surgery. Methods: 8 healthy adult horses. Methods: Anesthesia was maintained with isoflurane or halothane (crossover study). At 6 intervals during anesthesia and surgery, cardiopulmonary variables and related derived values were recorded. Recovery from anesthesia was assessed; gastrointestinal tract motility was subjectively monitored for 72 hours after anesthesia. Horses were administered chromium, and fecal chromium concen...
Bettschart-Wolfensberger R, Bowen MI, Freeman SL, Feller R, Bettschart RW, Nolan A, Clarke KW.To determine cardiopulmonary effects of total IV anesthesia with propofol and medetomidine in ponies and effect of atipamezole on recovery. Methods: 10 ponies. Methods: After sedation was induced by IV administration of medetomidine (7 microg/kg of body weight), anesthesia was induced by IV administration of propofol 12 mg/kg) and maintained for 4 hours with infusions of medetomidine (3.5 microg/kg per hour) and propofol 10.07 to 0.11 mg/kg per minute). Spontaneous respiration was supplemented with oxygen. Cardiopulmonary measurements and blood concentrations of propofol were determined during...
Meier M, Bettschart-Wolfensberger R, Schwarzwald CC, Portier K, Gysler A, Ringer SK.Dobutamine is routinely used to improve cardiovascular function in anaesthetized horses. However, dobutamine in conscious horses is insufficiently investigated. Ten research horses that were already instrumented for a preceding trial were included into the study. Cardiovascular variables were recorded and blood samples taken after instrumentation (Baseline), before starting dobutamine and after 10 min of dobutamine infusion (2 µg kg min ). A significant increase in systemic blood pressure, mean pulmonary artery pressure and right atrial pressure, and a decrease in heart rate were observe...
Hinchcliff KW, McKeever KH, Muir WW.The authors investigated the cardiovascular effects of low doses of nitroprusside, dobutamine, and phenylephrine and a beta-adrenergic blocking dose of propranolol in conscious, healthy horses with and without prior atropine administration. A parasympathetic blocking dose of atropine produced significant increases in heart rate and arterial pressures, and decreased stroke volume, ejection fraction, pulse pressure, and right-ventricular end-diastolic pressure and volume. Cardiac output was not changed by atropine administration. Nitroprusside reduced arterial pressures to a greater extent in at...
Wittenberg-Voges L, Kästner SB, Raekallio M, Vainio OM, Rohn K, Hopster K.To compare the effects of MK-467 during isoflurane anaesthesia combined with xylazine or dexmedetomidine on global and gastrointestinal perfusion parameters. Methods: Prospective, randomized experimental trial. Methods: A total of 15 warmblood horses. Methods: Horses were divided into two groups for administration of either dexmedetomidine (D) or xylazine (X) for premedication (D: 3.5 μg kg; X: 0.5 mg kg) and as constant rate infusion during isoflurane anaesthesia (D: 7 μg kg hour; X: 1 mg kg hour). During anaesthesia, heart rate, mean arterial blood pressure (MAP), systemic vascular resista...
Raisis AL, Young LE, Taylor PM, Walsh KP, Lekeux P.To use Doppler ultrasonography and single-fiber laser Doppler flowmetry (LDF) to evaluate blood flow in the dependent and nondependent hind limbs of anesthetized horses and to evaluate changes in femoral arterial blood flow and microvascular skeletal muscle perfusion in response to administration of phenylephrine hydrochloride or dobutamine hydrochloride. Methods: 6 healthy adult horses. Methods: Horses were anesthetized and positioned in left lateral recumbency. Doppler ultrasonography was used to measure velocity and volumetric flow in the femoral vessels. Single-fiber LDF was used to measur...
Kushiro T, Yamashita K, Umar MA, Maehara S, Wakaiki S, Abe R, Seno T, Tsuzuki K, Izumisawa Y, Muir WW.The anesthetic sparring and cardiovascular effects produced by midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.05 mg/ml (0.025 ml/kg/hr) drug infusion during sevoflurane in oxygen (MKM-OS) anesthesia was determined in healthy horses. The anesthetic sparring effects of MKM-OS were assessed in 6 healthy thoroughbred horses in which the right carotid artery was surgically relocated to a subcutaneous position. All horses were intubated and ventilated with oxygen using intermittent positive pressure ventilation (IPPV). The end-tidal concentration of sevoflurane (ET(SEV)) required to maintain s...
Daunt DA, Dunlop CI, Chapman PL, Shafer SL, Ruskoaho H, Vakkuri O, Hodgson DS, Tyler LM, Maze M.Cardiopulmonary and behavioral responses to detomidine, a potent alpha 2-adrenergic agonist, were determined at 4 plasma concentrations in standing horses. After instrumentation and baseline measurements in 7 horses (mean +/- SD for age and body weight, 6 +/- 2 years, and 531 +/- 48.5 kg, respectively), detomidine was infused to maintain 4 plasma concentrations: 2.1 +/- 0.5 (infusion 1), 7.2 +/- 3.5 (infusion 2), 19.1 +/- 5.1. (infusion 3), and 42.9 +/- 10 (infusion 4) ng/ml, by use of a computer-controlled infusion system. Detomidine caused concentration-dependent sedation and somnolence. The...
Hollis AR, Ousey JC, Palmer L, Stephen JO, Stoneham SJ, Boston RC, Corley KT.Norepinephrine increases arterial blood pressure but may have adverse effects on renal blood flow. Fenoldopam, a dopamine-1 receptor agonist, increases urine output in normotensive foals. The combination of norepinephrine and fenoldopam may lead to improved renal perfusion compared with an infusion of norepinephrine alone. The combined effects of these drugs have not been reported in the horse. Objective: Norepinephrine will alter the hemodynamic profile of foals without affecting renal function. Addition of fenoldopam will change the renal profile during the infusions without changing the hem...
Fantoni DT, Marchioni GG, Ida KK, Belo JN, Zoppa AL, Silva LC, Ambrósio AM.To assess the cardiopulmonary effects of ephedrine and phenylephrine for management of isoflurane-induced hypotension in horses. Methods: Prospective randomized clinical study. Methods: Fourteen isoflurane-anesthetized horses undergoing digital palmar neurectomy. Methods: Ephedrine (EPH group; 0.02 mg kg(-1) minute(-1); n = 7) or phenylephrine (PHE group; 0.002 mg kg(-1) minute(-1); n = 7) was administered to all horses when mean arterial pressure (MAP) was <60 mmHg. The infusions were ended when the target MAP was achieved, corresponding to a 50% increase over the pre-infusion MAP (baseline)....
Wagner AE, Dunlop CI, Wertz EM, Chapman PL, Baxter GM, Klopp LS.Seven horses, which were part of an investigation of the effect of endotoxin administration on vascular reactivity, were anesthetized on two separate occasions for surgical excision of 4-cm sections of palmar digital artery and vein. On the first occasion, the horses were given an infusion of 1 L 0.9% NaCl solution intravenously (i.v.) just before induction of anesthesia (control); on the second occasion, the horses received an infusion of 1 L 0.9% NaCl containing Escherichia coli endotoxin, 0.1 microgram/kg (endotoxin). On both occasions, anesthesia was induced with xylazine, guaifenesin, and...
Ohta M, Kurimoto S, Tokushige H, Kuroda T, Ishikawa Y.To determine hemodynamic effects of hydroxyethyl starch (HES) infusion during anesthesia in horses, incremental doses of 6% HES were administered to 6 healthy Thoroughbred horses. Anesthesia was induced with xylazine, guaifenesin and thiopental and maintained with sevoflurane at 2.8% of end-tidal concentration in all horses. The horses were positioned in right lateral recumbency and administered 3 intravenous dose of 6% HES (5 ml/kg) over 15 min with 15-min intervals in addition to constant infusion of lactated Ringer's solution at 10 ml/kg/hr. Hemodynamic parameters were measured before and e...
Hollis AR, Ousey JC, Palmer L, Stoneham SJ, Corley KT.Norepinephrine is a potent vasopressor that increases arterial blood pressure but may have adverse effects on renal blood flow. The combination of norepinephrine and dobutamine may lead to improved renal perfusion compared to an infusion of norepinephrine alone. The effects of these drugs in the normotensive neonatal foal have not been reported. Objective: Norepinephrine increases arterial blood pressure. Adding dobutamine to a norepinephrine infusion will change the renal profile during the infusions without changing the arterial blood pressure. Methods: Eight conscious Thoroughbred foals wer...
Jones T, Bracamonte JL, Ambros B, Duke-Novakovski T.To evaluate effects of anesthesia induced with alfaxalone and maintained with alfaxalone, dexmedetomidine and remifentanil infusions in foals. Methods: Prospective, experimental study. Methods: A group of six healthy foals [median (range) 11 (8-33) days] undergoing abdominal surgery. Methods: Intravenous (IV) dexmedetomidine (3-7μgkg) provided sedation for insertion of a pulmonary artery catheter. IV anesthesia was induced with alfaxalone (2mgkg) and maintained with alfaxalone (6mgkghour), dexmedetomidine (1μgkghour) and remifentanil (3μgkghour). Foals were endotracheally intubated and lung...
Ohta M, Kurimoto S, Ishikawa Y, Tokushige H, Mae N, Nagata S, Mamada M.To determine dose-dependent cardiovascular effects of dobutamine and phenylephrine during anesthesia in horses, increasing doses of dobutamine and phenylephrine were infused to 6 healthy Thoroughbred horses. Anesthesia was induced with xylazine, guaifenesin and thiopental and maintained with sevoflurane at 2.8% of end-tidal concentration in all horses. The horses were positioned in right lateral recumbency and infused 3 increasing doses of dobutamine (0.5, 1.0 and 2.0 µg/kg/min) for 15 min each dose. Following to 30 min of reversal period, 3 increasing doses of phenylephrine (0.25, 0.5 and 1....
Brodbelt DC, Harris J, Taylor PM.This study investigated whether maintenance of normotension using a methoxamine infusion would prevent activation of the stress response during halothane anaesthesia in ponies. After acepromazine premedication, anaesthesia was induced with thiopentone in six ponies, and maintained for 120 minutes with halothane in oxygen and ventilation to normocapnia. Methoxamine (M, 0.013+/-0.005 mg kg(-1) min(-1)) or saline (C) was infused throughout anaesthesia. Sequential blood samples were taken for cortisol and ACTH assay. During anaesthesia normotension (mean arterial blood pressure 101-124 mm Hg) was ...
Geimer TR, Ekström PM, Ludders JW, Erichsen DF, Gleed RD.The haemodynamic effects of hyoscine-N-butylbromide (0.30 mg/kg, intravenously) were studied in eight adult ponies in a blinded two-period crossover experiment with repeated measures. Values for heart rate were 63%, 48% and 13% greater than control values at 1, 16 and 46 min, respectively, after administration of hyoscine-N-butylbromide. Cardiac output increased by 16% at 16 min after drug injection. Mean right atrial pressure was decreased by 79%, 63%, 45% and 52% at 1, 16, 46 and 61 min, respectively, after drug administration. Stroke volume was decreased by 32% at 1 min and pulmonary arteri...
Schnuelle ML, Hopster K, Toribio RE, Hurcombe SD.To compare the effects of 7.2% hypertonic and 0.9% isotonic saline (sodium chloride) solutions on cardiovascular parameters and plasma arginine vasopressin (AVP) concentrations in healthy, isoflurane-anesthetized horses. Methods: 8 healthy horses. Methods: In a prospective, randomized, crossover study, horses were anesthetized with isoflurane twice with a 14-day washout period between anesthetic episodes. While anesthetized, horses received a bolus (4 mL/kg) of 7.2% hypertonic saline solution (HS) or 0.9% isotonic saline solution (IS). Heart rate; systolic, mean, and diastolic arterial blood p...
Tetens J, Bueno AC, Cornick-Seahorn JL, Hosgood G, Eades SC, Moore RM.To determine hemodynamic and metabolic effects of IV infusion of ATP-MgCl2 combination and maximal safe IV infusion rate in conscious horses. Methods: 6 adult female horses. Methods: All horses received an IV infusion of ATP-MgCl2 combination, beginning at a rate of 0.05 mg of ATP/kg of body weight/min, which was increased by 0.05 mg/kg/min increments at 10-minute intervals until a rate of 1.0 mg/kg/min was achieved. Data were collected prior to the start of the infusion, at the end of each infusion rate, and at 15-minute intervals for the next hour after discontinuation of the infusion. Measu...
Garcia Filho SG, de Andrade FSRM, Dos Santos RST, Gonçalves LA, Pereira MAA, de Souza AF, Ambrósio AM, Fantoni DT.The objective of this study was to compare the hemodynamic effects of dobutamine and ephedrine during the management of anesthesia-related hypotension in healthy horses. Thirteen horses underwent general anesthesia with isoflurane and were randomly divided into two different groups, one of which received a dobutamine constant rate infusion (CRI) (1 µg/kg bwt/min) and the other received an ephedrine CRI (20 µg/kg bwt/min) when hypotension (<60 mmHg) was identified, following up to 15 min after the blood pressure reached 70 mmHg. All horses were equipped with a pulmonary artery catheter and a ...
