Topic:Blood Pressure
Blood pressure in horses refers to the force exerted by circulating blood on the walls of the blood vessels. It is a vital physiological parameter that can provide insights into the cardiovascular health of equines. Blood pressure is influenced by various factors, including heart rate, blood volume, and vascular resistance. In horses, blood pressure measurements can be used to assess cardiac function, detect circulatory abnormalities, and monitor the effects of anesthesia or medications. This page compiles peer-reviewed research studies and scholarly articles that explore the methods of measuring blood pressure in horses, the factors affecting it, and its implications for equine health management.
Evaluation of the demand valve for resuscitation of horses. Arterial blood gas values, rate of pulmonary nitrogen washout, respiratory rate, arterial blood pressure, heart rate, and cardiac output were determined during ventilation of six anesthetized horses, with a demand valve. The horses were allowed to ventilate spontaneously, or intermittent positive pressure ventilation was utilized. When compared with spontaneous ventilation, intermittent positive pressure ventilation caused a significant increase in the rate of pulmonary nitrogen washout and a significant decrease of arterial carbon dioxide. It was concluded that intermittent positive pressure ...
Cardiopulmonary, behavioral, and pharmacokinetic effects of propoxyphene in horses. The acute behavioral cardiopulmonary and pharmacokinetic effects of propoxyphene hydrochloride were studied in seven adult horses. Each horse was given three different dosages of propoxyphene (0.5, 1.0, 2.2 mg/kg) IV. Fourteen days was allotted between each drug administration. The lower IV dosages of propoxyphene (0.5, 1.0 mg/kg) resulted in no changes in indices of cardiopulmonary function. Four horses demonstrated a transient period of muscle fasciculations when given 0.5 mg of propoxyphene/kg. Horses given 1.0 mg/kg demonstrated a brief period of euphoria, ataxia, and muscle fasciculations...
Physiologic effects of succinylcholine chloride in mechanically ventilated horses anesthetized with halothane in oxygen. Succinylcholine chloride, administered to horses anesthetized with halothane in oxygen and mechanically ventilated, caused slight but significant (P less than 0.01) increases in heart rate. Significant alteration in mean arterial blood pressure did not occur, and there were clinically insignificant increases in serum K+ and C1- concentration. Cardiac dysrhythmia and myoglobinuria did not occur. Thus, effects of halothane anesthesia and mechanical ventilation prevented cardiac dysrhythmia and hypertension and greatly reduced the tachycardia generally associated with siccinylcholine administrati...
Hemodynamic and respiratory effects of xylazine-morphine sulfate in horses. The cardiopulmonary effects of two xylazine-morphine sulfate drug combinations (mixtures) given IV were evaluated in horses. In horses given xylazine (0.66 mg/kg of body weight) and morphine sulfate (0.12 mg/kv) IV (experiment 1), there were significant (P less than 0.05) decreases in heart rate, cardiac output, and respiratory rate. Central venous pressure was significantly (P less than 0.05) increased. Arterial and pulmonary arterial blood pressures increased significantly (P less than 0.05) but transiently. Arterial blood gas tensions (PaCO2 and PaO2) and pH remained unchanged. In the horse...
Indirect measurement of mean blood pressure in the normotensive and hypotensive horse. Indirect mean arterial pressure was obtained from the tails of 78 anaesthetised and unanaesthetised normotensive and hypotensive horses. Data were obtained to determine the optimum cuff width in relation to tail circumference. A cuff that is too wide under-estimates and a cuff that is too narrow over-estimates blood pressure. With the optimum cuff width, which is slightly in excess of about one-fifth of the tail circumference, indirect mean blood pressure was obtained consistently in normotensive and hypotensive animals with mean blood pressures of 40 mmHg and frequently in animals with pressu...
Cardiopulmonary effects of narcotic agonists and a partial agonist in horses. The cardiopulmonary effects of the narcotic agonists morphine, meperidine, oxymorphone, and methadone and of the partial agonist pentazocine were examined in the pain-free adult horse. The drugs produced dysphoric followed by euphoric effects. Increases in heart rate, arterial blood pressure, and cardiac output were observed in all horses with all drugs. Arterial blood pressure remained increased even after heart rate and cardiac output had returned to base-line values. Respiratory rate generally remained unchanged or increased shortly after drug administration and then decreased insignificant...
Evaluation of xylazine, guaifenesin, and ketamine hydrochloride for restraint in horses. A combination of intramuscular xylazine plus intravenous guaifenesin and ketamine hydrochloride was evaluated as a method for chemical restraint and casting of the adult horse. This drug combination provided safe and rapid induction of the horse and uneventful recovery from lateral recumbency. Cardiopulmonary function remained within base-line values for the adult horse, although cardiac output, arterial blood pressure, and arterial partial pressure of oxygen were decreased from base-line values. Xylazine, guaifenesin, and ketamine hydrochloride provided safe induction to general anesthesia wi...
Cardiovascular, acid-base, electrolyte, and plasma volume changes in ponies developing alimentary laminitis. Twelve Shetland ponies were fed a high-starch ration. Seven ponies which had a transitory metabolic acidosis developed laminitis 56 hours (+/- 3.5, SEM) after overfeeding. These ponies also developed persistent hypokalemia, hyperthermia, and increased heart rate 24 hours before the onset of lameness. Serum sodium, serum chloride, hematocrit, plasma volume, and blood volume were unchanged. At the onset of clinical signs of laminitis, cardiac output and blood pressure increased, but total peripheral resistance was unchanged. None of the measured or calculated values predicted the onset of lamini...
Evaluation of xylazine and ketamine hydrochloride for anesthesia in horses. The cardiopulmonary effects resulting from the combination of xylazine and ketamine hydrochloride were evaluated in the adult horse. Xylazine (1.1 mg mg/kg) administered intravenously prior to or simultaneously with ketamine hydrochloride (2.2 mg/kg; intravenous) provided excellent analgesia and light anesthesia in all horses. Cardiac output, arterial blood pressure, pulmonary arterial pressure, central venous pressure, and pulmonary arterial wedge pressure remained within normal limits for the adult horse. Evidence of respiratory acidosis developed with time during the anesthetic period. Indu...
Effects of preanesthetic medication, anesthesia, and position of recumbency on central venous pressure in horses. Central venous pressure (cvp) was recorded in horses before and after tranquilization and during halothane-maintained anesthesia in lateral or dorsal recumbency. The cvp was significantly decreased after administration of acetylpromazine, when compared with base line measurements and measurements taken after xylazine administration. After induction of anesthesia, cvp increased with time for 75 minutes, and values in lateral recumbency were significantly higher than those in dorsal recumbency.
The rate of rise of intraventricular pressure as an index of myocardial contractility in conscious and anaesthetised ponies. Measurements of the rate of rise of left ventricular blood pressure (dP/dt) have been made in conscious and anaesthetised ponies. Concurrent measurements of heart rate, mean arterial pressure and left ventricular pressure were also made in order to assess their relationship to values of dP/dt. Thiopentone-halothane and thiopentone-ether anaesthesia reduced the maximal rate of rise of intraventricular pressure (dP/dt max) from conscious control levels. After correcting for variations in the loading conditions of the ventricle, the depressant effect of halothane was still apparent, but the actio...
The applied pharmacology of azaperone in ponies. The butyrophenone tranquilliser, azaperone, was administered intramuscularly to ponies in five series of experiments, using a dose level of 0-4 mg/kg once and 0-8 mg/kg four times. An excellent or good sedative effect was usually obtained with both dose levels, but the response was more consistent with the higher dose. The onset of sedation was apparent within 10 min of administration, the maximal effect usually occurring between 20 and 60 min while sedation was no longer apparent after 2 to 6 h. Body temperature was reduced in all animals for at least 2 h and respiratory rate was increased in...
Ultrasonic measurement of arterial blood pressure in conditioned thoroughbreds. Indirect systolic and diastolic arterial pressure measurements of 456 Thoroughbred horses of various ages and sex stabled at 9 different race tracks were measured with an ultrasonic-Doppler device interfaced with a sphygmomanometer cuff. The mean systolic pressure was 111.8 +/- 13.3 mmHg and the mean diastolic pressure was 69.6 +/- 13.8 mmHg in this population.
Effects of azaperone on cardiovascular and respiratory functions in the horse. 1 The butyrophenone tranquilizer, azaperone, was administered intramuscularly, at dose levels of 0.4 and 0.8 mg/kg, to ponies and its effects on cardiovascular and respiratory functions assessed. 2 Arterial blood pH, CO2 tension (PaCO2) and O2 tension (PaO2) remained relatively constant throughout the course of action of azaperone. 3 Azaperone did not modify plasma protein concentration but venous blood packed cell volume and haemoglobin concentration were reduced by 5 to 10% for at least 4 hours. These changes were probably caused by uptake of erythrocytes into the splenic reservoir. 4 Small ...
Pulmonary arterial wedge pressures: blood gas tensions and pH in the resting horse. Blood pressure recordings were made from right atrium, right ventricle, pulmonary trunk, and pulmonary arterial "wedge" positions in the standing, resting, adult horse. Similarly, comparisons were made of blood samples collected from these vascular positions, as well as from jugular vein and carotid artery. A consistently lower partial pressure of carbon dioxide and a greater partial pressure of oxygen and pH were found in blood samples from pulmonary arterial wedge than from carotid artery. A technique for safe and rapid collection of pulmonary trunk and pulmonary arterial wedge blood gases, ...
Influence of induced hypermagnesemia and hypocalcemia on neuromuscular blocking property of oxytetracycline in the horse. The neurally evoked contractile response of the upper lip muscles of horses anesthetized with halothane was used to evaluate the neuromuscular blocking property of oxytetracycline which was administered intravenously at total dose rate of 21 to 28 mg/kg. This dose rate did not alter the contractile response which had a mean control value (and standard error; SE) of 1.76 plus or minus 0.22 kg. Arterial blood pressure was not affected by these dose rates. Neuromuscular blocking effect of the antibiotic occurred when it was administered during partial neuromuscular blockade which had been induced...
Hypoxic pulmonary hypertension in the pony. Hemodynamic measurements were made in 6 ponies at low altitude (Madison, WI, altitude, 250 m) and after 1, 2, 4, and 6 weeks at high altitude (Climax, CO, altitude, 3,400 m). The salient findings were that ponies maintain an increased heart rate and cardiac output and develop significant pulmonary hypertension at high altitude. The average control resting mean pulmonary artery pressure (BPpul) was 25.1 mm of Hg at 250 m; this value increased to 56.3 mm of Hg after 6 weeks at 3,400 m. An additional finding was that the pulmonary vascular response to acute hypoxia seemed to increase with time at...
Systolic time intervals in domestic ponies: alterations in a case of coarctation of the aorta. This report describes the measurement of systolic time intervals in a nine year old female domestic pony which was found at necropsy to show coarctation of the aorta and bilateral ventricular hypertrophy. Electrocardiogram, phonocardiogram and direct arterial blood pressure were recorded from the pony in a standing unmedicated state and systolic time intervals were measured from the resulting tracings. A prolongation of left ventricular ejection time and shortening of the pre-ejection period were observed in comparison to a group of normal ponies similarly examined. Such changes are consistent...
The influence of suxamethonium on cardiovascular and respiratory function in the anaesthetized horse. 1. In horses anaesthetized with halothane the intravenous administration of suxamethonium chloride, at a dose level of 0.2 mg/kg, produced a short-lived period of hypoventilation, which was associated with increases in arterial blood PCO(2) levels and in plasma concentrations of bicarbonate, sodium and potassium ions, and reductions in arterial blood pH and PO(2) values.2. The respiratory depressant action of suxamethonium chloride 0.2 mg/kg was accompanied by increases in blood pressure and heart rate. Doses of suxamethonium chloride 0.4 mg/kg produced similar but quantitatively greater chang...