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Biomedical subjects

W W Muir

Publications and source records attributed to W W Muir.

At least 181 records · Page 10Linked to original sources
PubMed1984

Pharmacologic and pharmacokinetic properties of methocarbamol in the horse.

The hemodynamic, respiratory, and behavioral effects, as well as the pharmacokinetic properties of methocarbamol, were determined in horses. Heart rate, cardiac output, arterial and venous blood pressures, respiratory rate, and arterial blood gases did not change after IV methocarbamol (4.4, 8.8, 17.6 mg/kg) administration. There were no signs of behavior modification or ataxia observed. Analysis of plasma concentration time data indicated that the disposition of methocarbamol may be dose-dependent. Clearance and steady-state volume of distribution decreased as the dose increased. Plasma concentrations of guaifenesin, a metabolite of methocarbamol, were never greater than 0.5% of the plasma concentration of methocarbamol.

Animals↗
PubMed1984

Furosemide: effects on the hemostatic mechanism of resting and exercised standardbred horses.

Two groups of 6 Standardbred horses each were used to study hemostatic functions at rest and after exercise with furosemide or a placebo. One group which was trained was given maximum exercise on the racetrack, and the other, a less-fit group, was given submaximum exercise on the treadmill. There was no difference in furosemide compared to placebo trial results in either group in coagulation screening tests, platelet concentration, or retention of platelets in a glass bead column. Increased fibrinogen concentration and enhanced platelet retention were associated with maximum exercise. Aggregation of platelets by adenosine diphosphate and bovine collagen was not different in furosemide and the placebo submaximal exercise trials.

Animals↗
PubMed1983

Atrial fibrillation in cows: clinical findings and therapeutic considerations.

In a 3-year period, atrial fibrillation (AF) was diagnosed in 16 dairy cows between the ages of 2 and 11 years. Ten cows had AF when they were referred to the hospital and 6 cows developed AF while hospitalized. The chief reason for hospitalization in 15 of the cows was a gastrointestinal problem. Characteristic auscultatory findings were irregular rhythm (mean rate +/- SD: 94 +/- 25 beats/min), variation in the intensity of heart sounds, and absence of the 4th heart sound. The electrocardiographic features of AF were ventricular and F wave (mean +/- SD) rates of 94.4 +/- 24.8 and 272.7 +/- 53.3 beats/min, respectively. The most common electrolyte disorders were hypocalcemia, hypochloremia, and hypokalemia. Some of the cows had no acid-base imbalance, but metabolic alkalosis, respiratory alkalosis, and metabolic acidosis were found in other cows. Conversion to normal sinus rhythm (NSR) without specific therapy was documented by electrocardiography in 6 cows. In 7 of 9 cows treated with quinidine sulphate or quinidine gluconate, the AF converted to NSR. Quinidine plasma concentration at the time of conversion ranged from 2.2 to 24 micrograms/ml. Four cows died while they were hospitalized. Only 1 cow was in AF at the time of death and in no case was death attributed to AF. A follow-up on each of the survivors indicated that the persistence of AF was associated with poor performance and progressive cardiac disease, whereas conversion to NSR uniformly led to clinical improvement.

Animals↗
PubMed1983

Automatic noninvasive sphygmomanometry in horses.

Systolic, diastolic, and mean arterial blood pressures and heart rate were determined in 73 horses, using an indirect automatic oscillometric technique. Blood pressure and heart rate data obtained by sphygmomanometry were compared with similar data obtained from cannulation of the horses' facial or dorsal metatarsal arteries. Good correlation between direct (actual) and indirect (oscillometric) blood pressures and heart rate measurements were obtained when the heart rate was low, using high sensitivity setting. Cardiac arrhythmias or hypotension prevented oscillometric measurements from being obtained in 9 (12%) horses.

Animals↗
PubMed1983

Complications associated with permanent pacemaker implantation in the dog.

Serious complications developed in 11 dogs treated for bradycardia with surgical implantation of a permanent pacemaker. Complications resulted from underlying heart disease, cardiac dysrhythmias, drugs and anesthetic agents, surgery, pulse generator and pacemaker lead malfunction, and infection. As a result of these complications, 8 dogs died from 1 day to 35 months after surgery. Their mean survival time was 17 months. Three dogs are alive and doing well. Evaluation of clinical and electrocardiographic abnormalities were necessary for the successful management of complications in some of these patients. It was concluded that complications should be expected in dogs that are treated wih cardiac pacemakers and that many of these problems can be anticipated and successfully treated.

Anesthesia↗
PubMed1983

Hemodynamics during experimental gastric dilatation-volvulus in dogs.

Gastric dilatation-volvulus (at 30 mm of Hg of gastric pressure) was experimentally induced in 8 dogs under sodium pentobarbital anesthesia. Hemodynamic indices including cardiac output, mean aortic pressure, left ventricular end diastolic pressure, heart rate, total peripheral resistance, and dp/dtmax were measured during a 180-minute period of gastric dilatation-volvulus and for 120 minutes after gastric decompression. Experimental gastric dilatation-volvulus resulted in significant (P less than 0.05) decreases in cardiac output (64%), mean aortic pressure (48%), left ventricular end diastolic pressure (68%), and ventricular dp/dtmax (32%) compared to 4 control dogs. Hemodynamic indices returned toward control values after gastric decompression. It was concluded that gastric dilatation-volvulus in the present experiment was capable of inducing hemodynamic alterations of a magnitude similar to those reported in gastric dilatation studies, using higher gastric pressures.

Animals↗
PubMed1983

Isovolumetric indices and humoral cardioactive substance bioassay during clinical and experimentally induced gastric dilatation-volvulus in dogs.

Plasma collected from 6 experimentally induced and 29 clinical cases of gastric dilatation-volvulus was assayed for cardioactive substances utilizing isolated canine papillary muscles. The results were correlated with in vivo isovolumetric indices of myocardial contractility observed during experimental gastric dilatation-volvulus in the dog. Cardioactive substances were not detected during experimental gastric dilatation-volvulus. Two experimental dogs showed a cardiostimulatory response and 4 experimental dogs showed a cardiodepressant response following gastric decompression. Cardioactive substance bioassays correlated well with isovolumetric indices in experimental dogs. The variable response in cardioactive substance bioassay observed in experimental dogs was consistent with clinical gastric dilatation-volvulus bioassays which produced a widely variable response ranging from strongly cardiostimulatory to strongly cardiodepressant.

Animals↗
PubMed1983

A new analgesic drug combination in the horse.

A xylazine and butorphanol drug combination produced minimal and transient hemodynamic effects and no significant respiratory depression when administered to 6 healthy horses. Combining xylazine and butorphanol produced a synergistic analgesic effect and provided good chemical restraint for a standing surgical procedure.

Analgesia↗
PubMed1983

Segmental epidural and subarachnoid analgesia in conscious horses: a comparative study.

Six adult horses were used to compare the effects of segmental epidural analgesia (SEA) and segmental subarachnoid analgesia (SSA). A 17-gauge Huber point directional needle was used to place a catheter with stylet into the epidural space or the subarachnoid space at the lumbosacral intervertebral junction and to catheterize the thoracolumbar epidural or subarachnoid space. The position of the catheter was confirmed radiographically. A 2% solution of mepivacaine hydrochloride was used at average doses of 80 mg (4 ml) to produce SEA and 30 mg (1.5 ml) to produce SSA. Onset of analgesia in response to superficial and deep muscular pinprick stimulations was significantly (P less than 0.05) faster in horses with SSA than with SEA (8.0 +/- 1.9 minutes vs 15.8 +/- 3.8 minutes). Maximal thoracolumbar analgesia extended from spinal cord segments T14 to L3 on both sides of the spinal column during SSA and from T12 to L2 on one or both sides during SEA. Duration of analgesia lasted significantly (P less than 0.05) longer in horses with SEA than in those with SSA (80.8 +/- 16.9 minutes vs 44.8 +/- 14.5 minutes). There was a significant (P less than 0.05) increase in subcutaneous temperature at the right and left 18th thoracic (T18) dermatomes and decreases of respiratory rate and rectal temperatures in horses with SEA. Respiratory rate and rectal temperature were not significantly (P greater than 0.05) decreased in horses with SSA.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia↗
PubMed1983

Continuous caudal epidural and subarachnoid anesthesia in mares: a comparative study.

A new technique for producing continuous caudal epidural analgesia (CEA) and caudal subarachnoid analgesia (CSA) in adult horses (mares) without causing loss of pelvic limb function is described. A modified 17-gauge Huber-point directional needle was used to place a catheter with stylet into either the epidural or subarachnoid space at the lumbosacral intervertebral junction. The catheter was positioned at either the midsacral (S2-3) subarachnoid space or caudal portion of the sacral (S-3 to S-5) epidural space in 7 mares. The position of the catheter was confirmed radiographically. A 2% solution of mepivacaine HCl was used at an average dose of 0.061 +/- 0.013 mg/kg (1.3 +/- 0.3 ml) to produce CSA and 0.196 +/- 0.034 mg/kg (4.1 +/- 0.7 ml) to produce CEA. Onset of analgesia to superficial and deep muscular pinprick stimulation was faster with CSA than it was with CEA (8.2 +/- 2.4 minutes vs 21.4 +/- 3.8 minutes). Maximal caudal analgesia extended from spinal cord segments S-1 to coccyx during CSA and CEA. Periods of analgesia were shorter with CSA than with CEA (70.0 +/- 21.8 minutes vs 102.1 +/- 13.2 minutes). Perineal (S-4 to S-5) dermatome subcutaneous temperature was increased after epidural and subarachnoid injections of mepivacaine HCl solution. Heart rate, respiratory rate, systolic, diastolic, and mean arterial blood pressures, pulse pressure, rectal temperature, arterial blood gas tensions (PaCO2, PaO2), pHa, hematocrit, and total solid concentrations did not change significantly (P greater than 0.05) from base-line values after injection. The benefits and potential complications of CSA and CEA in horses are discussed.

Anesthesia, Caudal↗
PubMed1983

Arrhythmogenicity of dopamine, dobutamine, and epinephrine in thiamylal-halothane anesthetized dogs.

The arrhythmogenicity of epinephrine, dopamine, and dobutamine, administered by constant-rate infusion, was determined in vagotomized and nonvagotomized thiamylal-halothane anesthetized dogs. Electrocardiograms and atrioventricular bundle electrograms revealed the development of atrial, junctional, and ventricular arrhythmias. The 3 drugs produced atrial arrhythmias at dosages smaller than those required to produce ventricular arrhythmias. The mean dosages (microgram/kg-1/min-1) required to produce ventricular arrhythmias on duplicate trials in vagotomized dogs were for epinephrine, 0.6 +/- 0.2; dopamine, 22.8 +/- 14.8; and dobutamine, 11.6 +/- 5.2. The corresponding doses for nonvagotomized dogs were for epinephrine, 0.8 +/- 0.3; dopamine, 35.3 +/- 13.5; and dobutamine, 21.9 +/- 13.9. Most ventricular arrhythmias originated from a single focus in the left ventricle. Heart rate and blood pressure were significantly increased immediately before ventricular arrhythmia appeared. We conclude that epinephrine, dopamine, and dobutamine are capable of producing cardiac arrhythmias in vagotomized and nonvagotomized thiamylal-halothane anesthetized dogs and that bilateral vagotomy decreases the dosage of epinephrine, dopamine, and dobutamine required to produce cardiac arrhythmias.

Anesthesia, Inhalation↗
PubMed1982

Acid-base and electrolyte disturbances in dogs with gastric dilatation-volvulus.

Blood samples from 57 dogs with gastric dilatation-volvulus were analyzed for acid-base, blood gas (P02, Pco2), and electrolyte abnormalities. Although a variety of pH, blood gas, and electrolyte disturbances were recorded, metabolic acidosis and hypokalemia were common findings. Three dogs had hypochloremic-hypokalemic metabolic alkalosis. Attempts to correlate the severity of pH, blood gas, and electrolyte derangements with duration of disease, heart rate, respiratory rate, or a mathematical index based on the sum of these variables were unsuccessful. It was concluded that acid-base and fluid therapy for dogs with gastric dilatation-volvulus should be based on accurate determinations of blood pH and serum bicarbonate and electrolyte concentrations.

Acid-Base Imbalance↗
PubMed1982

Gastric dilatation-volvulus in the dog, with emphasis on cardiac arrhythmias.

Gastric dilatation was diagnosed in 156 dogs during a 5-year period. The recurrence rate was 10% and the overall mortality was 43%. Large-breed dogs of either sex and ranging in age from 2 months to 15 years (mean age, 5.2 +/- 2.9 years) were found to be susceptible to the problem. Cardiac arrhythmias were diagnosed in 48 of 115 (42%) affected dogs. Cardiac arrhythmias occurred most frequently between 12 and 36 hours after the onset of gastric dilatation-volvulus and were generally ventricular in origin.

Animals↗
PubMed1982

Hemodynamic and respiratory effects of segmental subarachnoid analgesia in adult Holstein cows.

Hemodynamic measurements, arterial and mixed venous blood gas tensions, and pH were determined in 13 adult, nonpregnant Holstein cows (511.3 +/- 77.3 kg) after subarachnoid injection of a 5% procaine hydrochloride solution (av dosage level of 0.162 +/- 0.026 mg/kg) at the thoracolumbar (T13-L1) intervertebral space. Segmental analgesia occurred within 8 to 12 minutes after completing the procaine HCl injection and extended between spinal cord segments T7 and L3 on both sides of the spinal column. The average duration of analgesia, as determined by the cows' responses to superficial and deep muscular pinpricks, was 35.8 +/- 8.5 minutes (25 to 60 minutes, min-max). Subarachnoid injection of procaine HCl caused a significant (P less than 0.05) increase in heart rate and significant (P less than 0.05) decreases in pulse pressure and rectal temperature. Cardiac output, stroke volume, left ventricular stroke work, left ventricular minute work, total peripheral resistance, arterial blood pressure, arterial and mixed venous blood gas tensions, pH, oxygen transport, oxygen uptake, PCV, and total solids did not change significantly (P greater than 0.05) from base-line values. Similarly, no significant changes (P greater than 0.05) were observed in a group of 5 control cows after subarachnoid injection of sodium chloride solution (1.5 ml, 0.9%) at the T13-L1 intervertebral space. Segmental subarachnoid analgesia caused minimal circulatory disturbance and was well tolerated by adult, conscious, unsedated cows.

Analgesia↗
PubMed1982

Pharmacodynamic and pharmacokinetic properties of diazepam in horses.

The cardiopulmonary, behavioral, and pharmacokinetic properties of diazepam were determined in horses. Heart rate, cardiac output, mean pulmonary artery, aortic and right atrial blood pressures, respiratory rate, and arterial pH and blood gas values did not change after IV diazepam (0.05, 0.1, 0.2, 0.4 mg/kg) administration. Increasing doses of diazepam resulted in signs of muscle weakness including fixed stance, muscle fasciculations of the head, neck, and thorax muscles, ataxia, and then recumbency. Dosages of diazepam exceeding 0.2 mg/kg produced mild sedation. Behavioral changes persisted for up to 2 hours with a dosage of 0.4 mg/kg. Plasma concentration-time data in horses given brief (5 min) infusions of diazepam were described by a triexponential equation. Total body clearances of diazepam were between 6.94 and 9.56 ml/min/kg, and the half-life values between 2.52 and 21.6 hours. The volume of distribution at steady state was 1.56 to 2.94 L/kg. N-Desmethyldiazepam was identified by gas chromatography-mass spectrometry following glucuronide hydrolysis of urine. Oxazepam, N-methyloxazepam, and N-desmethyldiazepam, but not diazepam, were detected after glucuronide hydrolysis of urine collected from 1 horse which was given 140 mg of IV diazepam. Only N-desmethyldiazepam was detected in hydrolyzed urine samples collected from other horses given 80 mg of diazepam.

Animals↗
PubMed1982

Aprindine for treatment of ventricular arrhythmias in the dog.

Aprindine hydrochloride was administered IV and orally to 20 dogs with ventricular tachycardia. Seventeen of the 20 dogs had been unsuccessfully treated with conventional antiarrhythmic drugs. Fifteen of the 20 dogs converted to sinus rhythm after IV aprindine therapy, 4 dogs demonstrated marked slowing of their ventricular tachycardia, and 1 dog showed an increase in the rate of ventricular tachycardia. Emesis, ataxia, salivation, and nystamus were observed in 7 dogs after IV aprindine therapy. One dog developed clinical and laboratory evidence compatible with acute hepatitis.

Animals↗