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Biomedical subjects

L W Hall

Publications and source records attributed to L W Hall.

At least 55 records · Page 3Linked to original sources
PubMed1984

Combined use of sedatives and opiates in horses.

The effects of four intravenous combinations, xylazine (0.7 mg/kg)/methadone (0.1 mg/kg), xylazine (0.7 mg/kg)/buprenorphine (0.004 and 0.006 mg/kg) and acepromazine (0.05 mg/kg)/buprenorphine (0.006 mg/kg) on arterial blood pressure, central venous pressure, heart rate, respiratory rate and blood gases were studied in four experimental ponies. With xylazine/buprenorphine and xylazine/methadone onset of sedation was rapid and obvious and although no surgical or diagnostic procedures were carried out, sedation was judged to be satisfactory for the next 30 to 40 minutes. Onset of sedation after intravenous injection of acepromazine/buprenorphine was slower and less obvious, while its duration was difficult to determine for the ponies could be aroused by noise even when apparently fully sedated. The observations indicated that at the stated doses all the drug combinations should be safe for clinical use.

Acepromazine↗
PubMed1984

Behavioral modification of estuarine fish exposed to sulfur dioxide.

This study was designed to determine the avoidance responses of juvenile striped bass (Morone saxatilis) and Atlantic menhaden (Brevoortia tyrannus) exposed to sulfur dioxide (sulfite) at acclimation temperatures of 15, 20, 25, and 30 degrees C. Predictive models were developed and compared for each species at each acclimation temperature. Striped bass avoided 2.2, 2.3, 3.0, and 3.5 mg sulfite/l at 15, 20, 25, and 30 degrees C, respectively. Atlantic menhaden avoided 3.2, 3.6, 2.9, and 3.0 mg sulfite/l at acclimation temperatures of 15, 20, 25, and 30 degrees C, respectively. Acclimation temperature was an important factor influencing the avoidance response of each species exposed to sulfur dioxide. Striped bass avoided lower concentrations of sulfite than Atlantic menhaden at 15 and 20 degrees C. Both species avoided approximately the same concentration of sulfite at 25 degrees C. Atlantic menhaden avoided lower concentrations of sulfur dioxide than striped bass at 30 degrees C.

Acclimatization↗
PubMed1984

Cardiovascular and pulmonary effects of recumbency in two conscious ponies.

Respiratory dead-space, tidal volume, respiratory rate, blood gases, cardiac output, heart rate and arterial and pulmonary arterial blood pressures were measured in two conscious, trained ponies in the standing position and in left lateral recumbency. The ponies were reluctant to remain lying down for more than about 20 mins but the reason for this did not become apparent. Tidal volume was reduced during recumbency but the respiratory rate increased, tending to maintain the minute volume at about that of the standing animal. Arterial carbon dioxide tension did not change significantly from standing values but the mean arterial oxygen tension values tended to decrease in both ponies during recumbency because of a slight increase in pulmonary venous admixture. Venous admixture in these two laterally recumbent conscious animals was considerably less than previously reported for anaesthetised subjects.

Animals↗
PubMed1983

COPD--or is it?

Explore the source record for details and available documents.

Animals↗
PubMed1982

A comparison of the avoidance responses of individual and schooling juvenile Atlantic menhaden, Brevoortia tyrannus subjected to simultaneous chlorine and delta T conditions.

The objectives of this study were to determine and compare the avoidance responses of individual and groups of Atlantic menhaden, Brevoortia tyrannus, exposed to simultaneous elevated temperature (0, 2, 4, and 6 degrees C) and total residual chlorine (TRC) (0.00, 0.05, 0.10, and 0.15 mg/l) conditions. An unbalanced three-factor factorial design was used to develop predictive avoidance models with this species at a test temperature of 25 degrees C. Fish tested in groups elicited the following avoidance responses: (1) a high avoidance response occurred at 0.10 and 0.15 mg/l TRC regardless of delta T; (2) avoidance increased with increasing delta T values at 0.00 mg/l TRC; and (3) TRC was the most important factor influencing avoidance. Atlantic menhaden tested individually demonstrated the following responses: (1) avoidance increased with increasing delta T at 0.15 mg/l TRC; (2) minimal increase in avoidance at 0.00, 0.05, and 0.10 mg/l TRC as delta T increased; (3) greatest avoidance occurred at 0.10 mg/l TRC and 6 degrees C delta T; and (4) TRC was the most important factor influencing avoidance. A significant difference was found between avoidance models of the group and individual tests: greater avoidance generally occurred at most test conditions during the group tests. The data collected in this study showed the importance of testing methods when evaluating the avoidance responses of a strongly schooling species exposed to simultaneous chlorine and delta T conditions simulating a power-plant effluent.

Animals↗
PubMed1981

Clinical trial of xylazine with ketamine in equine anaesthesia.

One hundred anaesthetics were administered in a clinical trial to 95 equine patients, ranging in age from nine months to 19 years and in weight from 140 to 1270 kg, undergoing a variety of surgical procedures. Acepromazine maleate premedication (0.01 to 0.03 mg per kg intramuscularly) was given to seven animals, the remainder were not premedicated. Xylazine (1.1 mg per kg) was injected intravenously over a two minute period and after a pause of two minutes ketamine (2.2 mg per kg) was injected rapidly by the same route. For 30 procedures no other anaesthetic was given but in 59 cases anaesthesia was prolonged with halothane-oxygen while in 11 additional intravenous agents were administered. Recumbency followed one-and-a-half to two minutes after completion of the ketamine injection and limb movements occurring immediately after the animal lay down gradually subsided over the next 30 to 60 seconds. On 26 occasions when no other agent was given satisfactory operating conditions were produced for a mean (+/- sd) of 20 +/- 7 minutes and on four occasions when absence of complete muscle relaxation was observed surgery was still possible. When no other agent was given the onset of recovery was abrupt but recovery was always extremely quiet; the animals stood 33 +/- 10 minutes after induction of anaesthesia and showed a remarkable absence of ataxia. A similar recovery was seen in the 56 animals receiving halothane-oxygen and all stood 28 +/- 14 minutes after disconnection from the anaesthetic system. Heart block was observed during induction of anaesthesia bu otherwise cardiovascular and respiratory parameters were well maintained. It was concluded that the xylazine-ketamine combination had advantages over other current techniques of inducing anaesthesia in horses.

Anesthesia, Intravenous↗
PubMed1981

Seasonal temperature and power plant chlorination effects on estuarine invertebrates.

The influence of seasonal temperatures (15-22 degrees C) on chlorine (0.00, 0.15 and 0.30 mg/L total residual chlorine), delta T (2, 6 and 10 degrees C), and exposure duration (0.08, 2.0 and 4.0 hr) interaction studies simulating power plant entrainment and effluent discharge conditions was evaluated for opossum shrimp. Neomysis americana and amphipods, Gammarus Seasonal Temperature was an important factor effecting the toxicity of the three treatment variables with both of these organisms. Mortality responses were greater at the higher acclimation temperatures.

Animals↗
PubMed1981

Acclimation temperature: an important factor in power plant chlorination studies with larval white perch, Morone americana.

Larval white perch were subjected to interacting power plant conditions of total residual chlorine (0.00-0.30 mg/l), elevated temperature (2, 6, and 10 degrees C), and exposure time (0.08, 2.0, and 4.0 h) at acclimation temperatures of 15 and 23 degrees C. Mortality observations were conducted up to 96 h after exposure. Acclimation temperature was a significant factor contributing to the effects of simulated power plant conditions during the low and high thermal conditions. Larvae tested at 23 degrees C generally showed greater mortality at all treatment levels than those tested at 15 degrees C. Mortality of test organisms during a 4-h exposure at the higher acclimation temperature was greater than 85% at elevated temperatures greater than 6 degrees C regardless of other treatment factors. Mortalities as low as 30% were observed at the lower acclimation temperature.

Acclimatization↗
PubMed1980

Intravenous anaesthesia in horses after xylazine premedication.

The effects of combining large doses of xylazine (1.1 mg per kg intravenously) with ketamine, methohexitone and thiopentone were studied in four experimental ponies. Onset of anaesthesia was more delayed after ketamine than after the barbiturates. Assessment of smoothness of induction and recovery indicated that all three combinations were effective and acceptable. Injection of xylazine was followed by atrioventricular (A-V) block which could be prevented by the prior administration of atropine. Blood pressure was well maintained with all three combinations of drugs. Arterial oxygen tension decreased as soon as the ponies became recumbent but there were no marked changes in arterial blood pH or carbon dioxide tension. Cardiac output was measured in one pony and was found to be least affected by ketamine. There was no great difference between the recumbency times after ketamine and methohexitone but thiopentone produced a significantly longer period of recumbency. In every instance the animals stood at the first attempt without struggling or excitement. The ability of the three drug combinations to produce surgically useful anaesthesia was not tested.

Anesthesia, Intravenous↗