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Biomedical subjects

B M Weaver

Publications and source records attributed to B M Weaver.

At least 19 recordsLinked to original sources
PubMed2001

Tissue/blood and tissue/water partition coefficients for propofol in sheep.

The primary objective of this study was to determine in vivo tissue/blood partition coefficients of propofol for use in physiological modelling of its pharmacokinetics. The sheep was used as an animal model. In the main series of experiments, crossbred ewes received a bolus of propofol 1% (Diprivan) followed by an infusion during which blood concentrations were measured at intervals. After 2 h, the sheep were killed with an injection of potassium chloride, and tissue samples were taken for storage at -20 degrees C and subsequent analysis. Tissue/blood partition coefficients depend on the amount of triglyceride which accumulates in blood from the propofol vehicle; for blood, free of added triglyceride, the following coefficients were calculated: brain, 3.23; heart, 5.94; kidney, 2.46; spleen, 1.86; semimembranosus muscle, > or = 1.61; triceps muscle, > or = 1.47. Calculated tissue/water coefficients were 35 times greater. There was indirect evidence of extraction of propofol by the lungs.

Anesthetics, Intravenous↗
PubMed1995

Measurement of propofol concentration in sheep blood and plasma: effect of storage at different temperatures.

In planning a study of the pharmacokinetics of propofol in sheep, contradictions were noted in the literature with regard to loss of propofol during storage of blood samples. This prompted a study of such loss from samples of sheep blood and plasma during storage at room temperature, +4 degrees C and -20 degrees C, for up to 17 days, over a range of concentrations from 1 to 20 micrograms/mL. Samples were drawn from 22 different sheep. Analysis was by the method of Adam et al. (1981). The best estimate of the overall mean loss rate was 0.7% per day with 95% confidence limits of 0.3% to 1.2% per day. The loss rate increased nonsignificantly with storage temperature. There were very small nonsignificant differences of loss rate between plasma and blood, between different concentrations, and between genders. There were significant differences of loss rate between sheep--up to about 2% per day in blood or plasma from any one sheep.

Animals↗
PubMed1995

The effect of xylazine on plasma thromboxane B2 concentration in sheep.

alpha 2-adrenoceptor agonist drugs can cause respiratory changes leading to a short period of hypoxaemia in sheep. It has been suggested that this is due to transient platelet aggregation and pulmonary microembolism. If platelet aggregation were to follow platelet activation in response to the administration of alpha 2 agonists, plasma thromboxane levels would be expected to rise. This study was carried out to measure plasma thromboxane B2 concentrations before and after the intravenous administration of the alpha 2-agonist drug xylazine at a dose of 0.1 mg/kg. It was found that the plasma thromboxane concentration rose by 320% and, furthermore, the rise was prevented by the prior administration of atipamezole hydrochloride (0.125 mg/kg), an alpha 2-adrenoceptor antagonist.

Adrenergic alpha-Agonists↗
PubMed1994

Pharmacokinetics of thiopentone in the horse.

The pharmacokinetics of thiopentone sodium administered intravenously as a single dose (11 mg/kg) were studied in acepromazine pre-medicated horses and ponies in which anaesthesia was maintained with either halothane (Group 1) or isoflurane (Group 2). The results showed that the disposition kinetics of thiopentone in horses and ponies were best described by a three-compartment open model. In plasma, a very short initial distribution phase in both horses and ponies, half-life 1.4 +/- 1.2 min (mean +/- SD) and 1.3 +/- 0.7 min, respectively, was obtained, which was followed by a second comparatively slower redistribution phase, half-life 16 +/- 12 min and 11 +/- 5 min, respectively. The volume of distribution for the drug was large, especially in the ponies which received isoflurane (1127 +/- 86 ml/kg), compared to the horses which received halothane (742 +/- 89 ml/kg). The drug had a somewhat shorter elimination half-life in the horses (147 +/- 21 min) than in than ponies (222 +/- 44 min), but no obvious difference in clearance of the drug was observed between the horses (3.5 +/- 0.5 ml/min/kg) and ponies (3.6 +/- 0.8 ml/min/kg).

Acepromazine↗
PubMed1993

Clinical signs and radiographic diagnosis of a portosystemic shunt in a foal.

A three-month-old native pony foal had a history of recurrent episodes of bizarre neurological behaviour. The results of clinical examinations were non-specific but clinicopathological investigations indicated hepatic encephalopathy. A percutaneous, needle liver biopsy revealed histopathological changes consistent with a portosystemic shunt, which was later identified by operative mesenteric portovenography, and confirmed at post mortem.

Age Factors↗
PubMed1990

Induction of anaesthesia in dogs and cats with propofol.

Propofol was used to induce anaesthesia in 89 dogs and 13 cats of either sex, various breeds and of widely different ages and weights; they varied considerably in physical condition and were anaesthetised for a variety of investigations and surgical procedures. They were premedicated with acepromazine, papaveretum, diazepam, pethidine, atropine and scopolamine in different combinations. After induction with propofol, anaesthesia was maintained with halothane, isoflurane, methoxyflurane and enflurane and, or, nitrous oxide. The mean (+/- sd) induction doses of propofol in unpremedicated and premedicated animals were 5.2 +/- 2.3 mg/kg and 3.6 +/- 1.4 mg/kg respectively for dogs, and 5.0 +/- 2.8 mg/kg and 5.3 +/- 4.3 mg/kg for cats. There were no differences between the sexes. Premedication did not affect recovery times. The incidence of side effects was very low. One dog showed evidence of pain when propofol was injected. No incompatibility was observed between propofol and the premedicants and other anaesthetic agents used.

Anesthesia↗
PubMed1990

Tissue perfusion in anaesthetised sheep.

1. Tissue perfusion was measured in seven sheep by the radioactive microsphere method. 2. The sheep were anaesthetised and ventilated to a near normal arterial carbon dioxide tension. 3. Cardiac output was measured utilizing the Fick principle as applied to thermodilution and at the end of the investigation the sheep were killed by an overdose of anaesthetic. 4. The results were compared with previously published values for conscious sheep and anaesthetised horses and found to be similar when known variations in body composition and physiology were considered.

Anesthesia, General↗
PubMed1989

Tissue blood content in anaesthetised sheep and horses.

The blood content of tissue in eight anaesthetized sheep and three anaesthetized horses was measured using chromium labelled autologous red blood cells. 2. Approximately half the total blood volume was found to be distributed within the body tissues and, with the exception of the spleen and fat, the distribution was similar in these two species.

Anesthesia, General↗
PubMed1988

The management of bovine fractures: a review of 59 cases.

Current trends in bovine fracture repair are reviewed with reference to 59 cases. Thirty-one cases were managed surgically, 14 by external fixation, and six by stall confinement. Eight animals were slaughtered without treatment being attempted. A successful outcome was achieved in 90 per cent of the surgically treated cases, compared with 57 per cent for those treated by external fixation methods.

Animals↗
PubMed1986

A simple device for respiratory resuscitation of newborn calves and lambs.

The neonatal death of calves and lambs is responsible for a heavy financial loss to the farming industry; respiratory failure accounts for 6 per cent of the post parturient deaths in lambs. A simple method of pulmonary resuscitation with expired air is described employing a device portable and simple enough for emergency use by herdsmen and shepherds. The rationale of the use of the equipment is explained.

Animals↗
PubMed1984

Observations following intravenous xylazine administration in steers.

Xylazine was used on 84 occasions to anaesthetise 34 steers, (17 Herefords and 17 Friesians) between 10 and 24 months of age with bodyweights ranging from 209 to 563 kg. Xylazine as a 2 per cent solution was injected intravenously; the mean dose for the Hereford steers was 0.228 mg/kg and for the Friesian steers 0.274 mg/kg. On 21 occasions xylazine only was used. On the other occasions the xylazine was supplemented with local or regional analgesia. The Hereford steers became recumbent after injection of xylazine more readily than the Friesian steers and took longer to recover. In addition the Hereford steers showed fewer reactions to surgical stimulation than the Friesians. It is concluded that xylazine should be supplemented with some form of effective analgesia whenever a surgical operation is performed.

Anesthesia, Conduction↗
PubMed1984

Muscle perfusion in the horse.

Muscle perfusion was studied in conscious and anaesthetised horses by monitoring the clearance of a locally injected bolus of saline containing radioactive xenon (133Xe). The mean of all the measurements made from the brachiocephalicus and semimembranosus muscles in conscious subjects was 1.29 ml/min/100 g while in anaesthetised subjects it was 0.40 ml/min/100 g. The significance of these results is discussed in relation to the clinical occurrence of post anaesthetic myositis.

Anesthesia, General↗
PubMed1984

A "standard horse" for use in physiologically based mathematical modelling.

Standard data for the horse which can be used in physiologically based mathematical computer modelling are presented. The data includes figures for tissue mass, density and perfusion, obtained by measurement mainly from horses weighing 200 to 300 kg. Other related parameters such as mean transit times and tissue blood volume have been calculated and included in the actual values listed for a 250 kg horse.

Animals↗
PubMed1983

Histological changes following Nd YAG laser photocoagulation of canine gastric mucosa.

Tissue changes produced in the dog stomach by exposure to a Nd YAG laser varied from mild mucosal oedema to cell vaporisation. Intermediate degrees of damage caused a marked inflammatory response leading to extensive fibrosis in the submucosa and muscularis propria. The true extent of tissue damage was not apparent immediately, and treated mucosa that initially appeared intact sometimes sloughed several days later to leave an ulcer. The extent of damage and the rate of healing depended on the amount of laser energy used. With pulses at optimum laser power (75 w) and exposure time (0.4 sec), however, haemostasis was achieved in induced ulcers with total energy concentrations that did not produce full thickness tissue damage nor alter the healing rate from that observed in untreated ulcers. Thermal contraction was the primary haemostatic mechanism, thrombosis only occurring as a secondary effect.

Animals↗