Search PubMed⌕ Search

Biomedical subjects

W W Muir

Publications and source records attributed to W W Muir.

At least 199 records · Page 11Linked to original sources
PubMed1982

Segmental thoracolumbar spinal (subarachnoid) analgesia in conscious horses.

A new technique for producing segmental subarachnoid analgesia in adult horses without causing complete loss of locomotor control is described. A 17-gauge Huber point (Tuohy) needle was used to place a catheter with a stylet into the subarachnoid space at the lumbosacral intervertebral space in 13 adult horses (weighing 500 +/- 60 kg, representing both sexes) and to advance the catheter craniad to the thoracolumbar area. The position of the catheter was confirmed radiographically. A 2% mepivacaine hydrochloride solution (1.5 ml, 30 mg) was injected through the catheter at a rate of 0.5 ml/60 s. Segmental analgesia, as determined by the horses' responses to superficial and deep muscular pinpricks, occurred within (onset) 5 to 10 minutes of injection and lasted (duration) 42.4 +/- 15 minutes (min-max, 25 to 68 minutes). Maximal thoracolumbar analgesia extended from spinal cord segments T12 to L3 on both sides of the spinal column. Subarachnoid injection of mepivacaine hydrochloride caused significant (P less than 0.05) increases in heart rate and subcutaneous temperature and decreases in respiratory rate and rectal temperature. Significant changes (P less than 0.05) were not observed in a control group of 7 horses after subarachnoidal injection of sterile water (1.5 ml). The surgical application of segmental subarachnoid analgesia was demonstrated in 1 horse. The benefits and potential complications of segmental subarachnoid analgesia in horses are discussed.

Anesthesia, Spinal↗
PubMed1982

Effect of xylazine hydrochloride on canine splenic weight: an index of vascular capacity.

Splenic weight, an index of changes in vascular capacity, was used to assess the effects of xylazine hydrochloride in anesthetized dogs. Intravenous xylazine (0.01, 0.1, and 1 mg/kg) produced dose-dependent decreases in vascular capacity as assessed by decreases in splenic weight which were significant (P less than 0.05) at the 1 mg/kg dose. Phenoxybenzamine, an alpha-adrenergic receptor blocking drug, prevented the splenic contractile response to xylazine. Propranolol, a beta-adrenergic receptor blocking drug, did not alter the splenic contractile response to xylazine. Intravenous xylazine (0.1 and 1 mg/kg) produced significant (P less than 0.05) decreases in heart rate, splenic arterial flow, and systolic, mean, and diastolic blood pressures. Central venous pressure increased significantly (P less than 0.05) in dogs given the 1 mg/kg dose.

Animals↗
PubMed1982

Cardiopulmonary effects of intramuscular xylazine-ketamine in calves.

The cardiopulmonary effects of an intramuscular xylazine (0.088 mg/kg)-ketamine (4.4 mg/kg) drug combination were evaluated in calves. Heart rate, central venous and mean pulmonary artery blood pressures, and cardiac output did not change after drug administration. Mean arterial blood pressure decreased significantly (P less than 0.05) 15 minutes after drug administration. Respiratory frequency increased significantly (P less than 0.05) whereas arterial partial pressure of oxygen (PaO2) decreased significantly (P less than 0.05) after drug administration. The duration of lateral recumbency was 55.7 +/- 10.4 minutes. Immediate or long-term adverse effects were not observed.

Animals↗
PubMed1981

Effects of segmental subarachnoid analgesia on arterial blood pressure, gas tensions, and pH in adult conscious cows.

Arterial blood pressure, blood gas tensions (PaCO2, PaO2), and pH (pHa) were determined in 16 adult, nonpregnant Holstein cows (620 +/- 54 kg) given subarachnoid injection of a 5% procaine hydrochloride solution at the T13-L1 intervertebral space. Analgesia, as determined by response to superficial and deep muscular pinpricks at the L1 dermatome, was delayed (onset) 7 to 15 minutes, and it lasted (duration) 28 to 83 minutes. Thoracolumbar analgesia extending between spinal cord segments T9 and L4 on 1 or both sides of the spine produced significant (P less than 0.05) increases in heart rate and decreases in respiratory rate, but otherwise had no effect (P less than 0.05) on systolic, diastolic, and mean arterial blood pressures, PaCO2, PaO2, and pHa. Similarly, no significant changes (P less than 0.05) of physiologic variables were observed in a control group of 5 cows given a subarachnoidal injection of 0.9% sodium chloride solution at 1 hour before procaine hydrochloride was injected. It was concluded that the unsedated, healthy cow tolerates segmental subarachnoid analgesia between spinal segments T9 and L4 well and that this analgesia is not adversely affected by hypoxemia, respiratory acidosis, or hypotension.

Anesthesia, Spinal↗
PubMed1981

Cardiopulmonary effects of butorphanol tartrate in horses.

The cardiopulmonary and behavioral effects of butorphanol were evaluated in pain-free adult horses. Butorphanol tartrate was administered IV in doses of 0.1, 0.2, and 0.4 mg/kg to the same horses on 3 separate occasions. There were no significant (P less than 0.05) changes in heart rate, mean and diastolic arterial pressure, mean and diastolic pulmonary arterial blood pressure, or cardiac output recorded in the horses given these doses. Systolic arterial blood pressure was significantly (P less than 0.05) increased in only the horses given the 0.2 mg/kg dose. Significant (P greater than 0.05) changes in electrocardiographic intervals, respiratory rate, arterial blood gas values, or pH were not recorded. Increasing IV doses of butorphanol resulted in varied behavioral changes, but were predominantly excitatory.

Animals↗
PubMed1981

Pharmacokinetic analysis of intravenously and orally administered quinidine in horses.

A pharmacokinetic study was made, using 7 healthy adult horses (weighing between 400 and 560 kg) given quinidine gluconate IV and quinidine sulfate orally. The apparent volume of distribution of quinidine base was 3.10 +/- 0.79 L/kg, total body clearance was 5.49 +/- 2.40 ml/minute/kg, and plasma half-life was 6.65 +/- 3.00 hours. The systemic availability of quinidine sulfate after oral administration of a 10 mg/kg dose was 48.5 +/- 20.4%. Oral administrations of quinidine sulfate in doses of 10 mg/kg and 10 g produced peak plasma concentrations of 0.79 microgram/ml at 146 minutes and 1.47 microgram/ml at 131 minutes, respectively. In 4 horses given 4 oral doses of 10 mg of quinidine sulfate/kg, each dose separated by 2 hours, maximal plasma concentrations of quinidine averaged 13% higher than the preceding minimal plasma concentration. The application of these pharmacokinetic determinations to the clinical use of quinidine in the horse is discussed.

Administration, Oral↗
PubMed1981

Pharmacokinetic analysis of intravenously and orally administered quinidine in cows.

Seven healthy adult cows weighing between 550 and 750 kg were administered quinidine gluconate (5 mg/kg) IV and quinidine sulfate (15,84 mg/kg) orally to determine pharmacokinetic values. The apparent volume of distribution was 3.80 +/- 2.21 L/kg. Total body clearance was 19.0 +/- 7.02 ml/min/kg and plasma half-life was 2.25 +/- 0.68 hours. The systemic availability of quinidine sulfate after oral administration of a 20 mg/kg dose was 23.3 +/- 16.3%. The mean peak plasma concentration reached in 7 cows after oral administration of quinidine sulfate was 0.26 micrograms/ml. The peak plasma quinidine concentration was reached in an average of 41 minutes after oral administration. The average plasma quinidine concentration 5 minutes after IV administration of quinidine gluconate was 27.5 +/- 22.1 micrograms/ml. At this time, some of the cows showed signs of quinidine toxicosis. The application of pharmacokinetic determinations to the clinical use of quinidine in cows is discussed.

Administration, Oral↗
PubMed1981

Segmental thoracolumbar subarachnoid analgesia in cows.

A new technique for producing segmental subarachnoid analgesia in adult cows without causing complete loss of locomotor control is described. Segmental subarachnoid analgesia was produced in 18 adult nonpregnant Holstein-Friesian cows. A 17-gauge Huber point directional needle was used to place a catheter with a stylet into the subarachnoid space at the lumbosacral intervertebral space and advance it craniad to the thoracolumbar intervertebral space. The position of the catheter was confirmed radiographically in 8 cows. A 5% solution of procaine hydrochloride was injected through the catheter. The volume injected varied between 1.5 ml (8 cows) and 2 ml (10 cows). The rate of injection was approximately 0.5 ml/30 s. In 5 cows, 1.5 or 2 ml of normal saline solution was injected intrathecally 1 hour before the injection of procaine hydrochloride. These cows served as the control group. Segmental analgesia was achieved 7 to 10 minutes after completing the procaine hydrochloride injection and extended between spinal cord segments T9 and L4 on one or both sides of the spinal cord. The average duration of analgesia, as determined by response to superficial and deep muscular pinprick stimulation at the I1 dermatome, was 43.7 +/- 17.6 minutes, with a range of 22 to 80 minutes. Significant decreases (P less than 0.05) in respiratory rate and rectal temperature and increases in heart rate and subcutaneous temperature occurred in cows given procaine hydrochloride. The clinical application of the technique was demonstrated in one surgical procedure described. The advantages and disadvantages of segmental subarachnoid analgesia compared with segmental epidural analgesia are discussed.

Analgesia↗
PubMed1981

Appearance of procaine in spinal fluid during segmental epidural analgesia in cows.

The concentration of procaine in the CSF of 10 adult nonpregnant cows was determined after epidural injection of 5% procaine hydrochloride solution. Samples of CSF were removed through a catheter introduced into the subarachnoid space at the lumbosacral intervertebral space and advanced craniad to the same level as the epidural injection site. The position and the location of the catheter and spinal needle were confirmed radiographically. Segmental analgesia was achieved 8 to 20 minutes after completing the procaine hydrochloride injection and extended between spinal cord segments T12 and L3 on one or both sides of the animal. The average duration of analgesia, as determined by response to superficial and deep muscular pinpricks at the L1 dermatome, was 81.3 +/- 22.8 minutes (min-max, 45-127 minutes). The average subarachnoid concentration of procaine 10 minutes after epidural injection was 120.4 +/- 42.9 microgram/ml. The highest average procaine concentration recorded was 160.7 +/- 63.7 microgram/ml at 25.0 +/- 6.7 minutes after injection. Average procaine concentration was 47.8 +/- 13.5 microgram/ml at cessation of analgesia. A similar concentration of procaine was recovered from the subarachnoid space during either unilateral or bilateral analgesia. Procaine was not found in arterial plasma after the epidural administration of procaine hydrochloride. Subarachnoid threshold concentrations of local anesthetic necessary to produce spinal analgesia were reached after repeated epidural injections, but not after a single administration. It is concluded that segmental epidural analgesia is principally due to anesthesia of dura-covered nerve roots within and outside the epidural space and is minimally, if at all, dependent on the production of analgesia of nerves within the subarachnoid space.

Analgesia↗
PubMed1980

Effects of furosemide on cardiovascular function and performance when given prior to simulated races: a double-blind study.

In a double-blind study under simulated racing conditions, six Standardbred horses, which had been trained for 12 weeks, were given 1 mg of furosemide/kg of body weight or saline solution IV 15 minutes before the first of two warm-up workouts (1.6 km at 60-minute intervals). Sixty minutes later, 135 minutes after drug or placebo injection, these horses were driven 1.6 km at maximum speed. Heart rate, respiratory rate, cardiac output, pulmonary trunk pressure, body temperature, PCV, arterial oxygen, and plasma lactic acid were recorded during and after the first warm-up workout and after a simulated race (1.6 km). Values increased compared with values determined at rest whether saline solution or furosemide was given. There were decreases in arterial CO2 and pH. When furosemide was given, the pulmonary trunk pressure was significantly lower (P < 0.05) during the first warm-up workout (1.6 km). There were no significant differences in the other values. The average times of the simulated races were not significantly (P < 0.05) different after the use of furosemide compared with average times after use of saline solution.

Animals↗
PubMed1980

Guaifenesin: cardiopulmonary effects and plasma concentrations in horses.

We determined the cardiopulmonary changes in horses given guaifenesin alone and in the same horses given xylazine (IV) immediately before administration of guaifenesin. In addition, plasma guaifenesin concentrations were determined in horses and 2 pregnant mares and compared with previously published values in ponies. The dose of guaifenesin necessary to produce lateral recumbency in adult horses was 134 +/- 34 mg/kg (mean +/- SD). The administration of guaifenesin caused insignificant (P less than 0.05) changes in heart rate, respiratory rate, right atrial pressure, pulmonary arterial pressure, and cardiac output. Systolic, diastolic, and mean arterial blood pressures were significantly (P less than 0.05) decreased. Arterial partial pressure of oxygen (PaO2) was transiently, but significantly (P less than 0.05), reduced. The administration of xylazine (IV) to the horses before they were given guaifenesin reduced the dose of guaifenesin necessary to produce lateral recumbency to 88 +/- 10 mg/kg. In these horses, there were significant transient decreases in heart rate, respiratory rate, cardiac output, and PaO2. Central venous pressure remained significantly (P less than 0.05) increased, whereas systolic, diastolic, and mean arterial blood pressures were significantly (P less than 0.05) decreased at all times. In horses given guaifenesin alone, plasma concentrations at the time of lateral recumbency were 313 +/- 108 microgram/ml, and in those given xylazine-guaifenesin, the concentrations of the drug were 277 +/- 83 microgram/ml. Neonatal concentrations of guaifenesin were approximately 30% of that of the mare immediately after delivery, indicating that significant amounts of guaifenesin cross the placental barrier in the mare.

Animals↗
PubMed1980

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 followed by a period of increased motor activity lasting for approximately 30 minutes. Horses given 2.2 mg of propoxyphene/kg demonstrated significant (P less than 0.05) increases in heart rate and arterial blood pressure and, after a brief period of ataxia and disorientation, displayed increased motor and locomotor activity lasting several hours. These behavioral effects were less apparent in three of four horses 4 hours after their appearance by the IV administration of naloxone. Propoxyphene exhibited a dose dependent half-life of from 61 to 135 minutes and an apparent volume of distribution of from 2.54 to 4.26 L/kg. Total body clearance was 21.9-28.4 ml/min/kg. In the adult pain-free horse, propoxyphene causes dose dependent excitatory effects similar to the narcotic analgesics.

Animals↗
PubMed1979

Coronary artery pressure development and wave transmission characteristics in the horse.

Measurements of the pressure waveform development and the wave transmission characteristics in the left extramural coronary arteries of the horse have been carried out. Near the ostium the left coronary pressure waveforms are seen to be virtually identical to the corresponding aortic root waveforms; however, the present of low frequency, relatively large amplitude pressure oscillations (on the order of 5 to 10 Hz) gradually become the dominant diastolic feature as one proceeds distally from the left ostium, and these eventually completely mask the incisura. In a limited number of experiments, these oscillations have been simultaneously observed on both centerline velocity and phasic flow signals. These are felt to be primarily due to wave reflection phenomena, but may represent a combined effect of wave reflections and the natural oscillatory motion of the heart mass. Peak systolic pressures were found to remain relatively unchanged as one proceeds distally; however, the end-diastolic pressures were found to decrease steadily, thus giving rise to an increasing pulse pressure and a gradually decreasing mean pressure. Wave speeds in the coronary arteries were found to range between 4 and 11 m.s-1, and the data obtained indicate the wave speed to be highly dependent on both local intralumenal pressure and spatial location.

Animals↗
PubMed1979

Comparison of the cardiopulmonary effects of etomidate and thiamylal in dogs.

The cardiopulmonary effects of etomidate, a nonbarbiturate, short-acting, IV anesthetic, were compared and contrasted with those of thiamylal sodium in chronically instrumented conscious dogs. Etomidate, when administered IV at dosages of 1.5 and 3.0 mg/kg of body weight, produced anesthesia lasting from 8 +/- 5 and 21 +/- 9 minutes, respectively. Heart rate, aortic blood pressure, left ventricular peak pressure, left ventricular end diastolic pressure, left ventricular contractile force, and myocardial oxygen consumption were unchanged after administration of either dose of etomidate; however, the dosage of 1.5 mg/kg produced significant (P less than 0.05) increases in respiratory rate and decreases in tidal volume. The minute volume remained unchanged from base-line values. Significant (P less than 0.05) decreases in tidal volume, arterial pH, and partial pressure of oxygen were produced, and minute volume remained unchanged when 3.0 mg of etomidate/kg of body weight was administered. Thiamylal sodium (8.0 mg/kg of body weight; given IV) produced anesthesia lasting for 14 +/- 5 minutes. Significant increases (P less than 0.05) in heart rate, arterial blood pressure, left ventricular peak pressure, and myocardial oxygen consumption were observed after IV administration. Left ventricular contractility was significantly (P less than 0.05) decreased. Respiratory rate was not significantly (P less than 0.05) affected by thiamylal although tidal volume and minute volume were decreased. These respiratory alterations resulted in significant (P less than 0.05) increases in the arterial partial pressure of carbon dioxide and decreases in pH and the partial pressure of oxygen. On the basis of cardiopulmonary function, etomidate offered rapid, safe, short duration anesthesia superior to that of thiamylal sodium.

Animals↗
PubMed1979

Hemodynamic effects of unilateral segmented lumbar epidural analgesia in cattle.

Hemodynamic measurements, arterial and mixed venous blood gas tensions, and pH were determined in 12 adult cows (mean weight 538 kg) following the injection of 8 ml of 5% procaine between the first and the second lumber vertebra into the epidural space. Comparison of base-line data with obtained during unilateral segmented lumbar analgesia between T(13) and L(3) segments indicated significant decreases (P is less than 0.05) in total peripheral resistance and diastolic and mean arterial blood pressures, and significant increases (P is less than 0.05) in heart rate and cardiac output. Arterial and mixed venous blood gas tensions and pH, O(2)-uptake, stroke volume, left ventricular stroke work, left ventricular minute work and hematocrit did not change significantly (P is less than 0.05). Cardiovascular and respiratory values in two cows (mean weight 700 kg) given xylazine (50 mg, IM), were depressed from base-line data, but did not change significantly (P is less than 0.05) during unilateral segmental epidural analgesia of segments T(13 to L(3). The nonsedated healthy cow tolerates sympathetic vasomotor blockade between T(13) and L(3) segments well and is able to mobilize circulatory mechanisms effectively.

Analgesia↗