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Biomedical subjects

J E Heavner

Publications and source records attributed to J E Heavner.

At least 73 records · Page 4Linked to original sources
PubMed1983

Indwelling jugular venous catheterization of semirestrained cattle.

An inexpensive method for chronic cannulation of one or both jugular veins in cattle was devised. A commercial catheter set containing a 14-gauge 5-cm needle, a 16-gauge 60-cm catheter with stylet, and a plastic retainer facilitated intravenous dosing and blood withdrawal at timed intervals. The method did not require special restraining equipment for large animals and was completed within 10 to 15 minutes per animal. The catheter apparatus did not interfere with ad libitum feeding and watering of trained cattle.

Animals↗
PubMed1981

Local anesthetics.

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Action Potentials↗
PubMed1981

Lidocaine and pentylenetetrazol seizure thresholds in cats are not reduced after enflurane anesthesia.

Some previous reports indicate that the excitability of the brain may be increased for days following enflurane anesthesia. The authors investigated this possibility in cats by determining whether or not pentylenetetrazol- (Metrazol) or lidocaine-seizure thresholds decreased after repeated enflurane exposure. The lidocaine-seizure threshold was bracketed in 4 cats, and the pentylenetetrazol-seizure threshold was bracketed in another 4 cats. Each cat was then exposed to 4 per cent enflurane for 2 hours on 4 successive days. Twenty-four hours after the last enflurane exposure, the cats were injected with the previously determined subthreshold dose of pentylenetetrazol (6.4 mg/kg, on the average) or lidocaine (7.8 mg/kg, on the average). No cat convulsed. It was therefore concluded that under our experimental conditions, repeated enflurane exposure does not increase the sensitivity to drugs which nonselectively excite the central nervous system (e.g., pentylenetetrazol) or to drugs which mimic temporal lobe epilepsy (e.g., lidocaine). This finding cast doubt that brain excitability is increased in the post-enflurane anesthetic period.

Anesthesia↗
PubMed1981

Anesthetic potencies and the unitary theory of narcosis.

Anesthetic potencies of nitrous oxide, isoflurane, enflurane, halothane, cyclopropane, or chloroform were measured in male (CD-1) mice using three end points: (a) the ability to maintain an upright position (the righting-response ED50, RR ED50); (b) the response to a tail-clamp stimulus (MAC); and (c) the response to heat applied to the tail (tail-flick ED50, TF ED50). The ratio of RR ED50 to MAC ranged from mean values of 0.475 for isoflurane, 0.507 for cyclopropane, 0.524 for enflurane, and less than 0.55 for N2O, to 0.600 for halothane and 0.621 for chloroform. The ratios of RR EDS50 to MAC for halothane differed significantly from the ratios for isoflurane and enflurane. The mean values for TF ED50/MAC and RR ED50/TG ED50 ranged from 0.688 to 1.01 and 0.664 to 0.682, respectively, for isoflurane, enflurane, and halothane. The nitrous oxide RR ED50/TF ED50, however, was 1.34. The ratios of TF ED50 to MAC were significantly different for halothane and isoflurane. The different end points were measured in an attempt to determine whether the response in mice anesthetized with a particular agent was the same with varying stimuli. The differences found suggest that a unitary mechanism of anesthetic action cannot completely explain the depression defined by these three end points.

Anesthesia, Inhalation↗
PubMed1980

Temperature-dependent nerve-blocking action of lidocaine and halothane.

The effect of lidocaine and halothane on the compound action potential of rat sciatic nerves was studied under hypo-hyperthermic conditions. In drug-free desheathed nerves, a total but reversible cold block occurred at 10-11 degrees C, and an irreversible heat block at 46 degrees C. Cooling potentiated the dose-dependent blocking action of lidocaine (decreased amplitude, and increased duration and latency of the compound action potential). Total block of conduction occurred at 17 degrees C with 100 microM lidocaine, at 20 degrees C with 200 microM lidocaine and at 24 degrees microM with 400 microM lidocaine. In nerves equilibrated in 200 microM lidocaine solution, the lidocaine concentrations in the nerves decreased as the temperature decreased; at 20 degrees C, the lidocaine concentration was about half of that at 37 degrees C. The nerve-blocking effect of lidocaine was also potentiated by increasing the temperature above 37 degrees C. At 30 degrees C and 20 degrees C, 1 vol. % halothane caused a slight time-dependent inhibition of the compound action potential. When the nerves were exposed to 2.5 vol. % halothane, the decrease in amplitude and increase in duration and latency were potentiated by hypothermia and were also time dependent. Interaction of halothane and temperature of 40 degrees C was not significant. Although thermodynamic principles suggest similarities between high pressure and cooling in reversing anaesthesia, cooling was found to potentiate the anaesthetic effect of lidocaine and halothane in this study. Temperature may thus be an interesting physical variable in studying nerve-blocking mechanisms.

Action Potentials↗
PubMed1979

Effect of atropine on tear formation in anesthetized dogs.

Tear production (as determined by the Schirmer I tear test) in five dogs given atropine (0.02 mg/kg) subcutaneously and in five dogs given 0.9% saline solution subcutaneously was compared before and during halothane anesthesia. Fifteen minutes after the atropine injections, mean tear production was 15.0 +/- 2.9 mm/minute, as compared with 23.8 +/- 2.9 mm/minute before treatment rate. There was no change in tearing 15 minutes after injection of the saline solution. Tear production declined in both groups during anesthesia. Ten minutes after anesthetic induction, mean tear formation was 20% of pretreatment value in the atropinized dogs and 54% of the pretreatment value in the dogs given saline solution. At the end of 1 hour of anesthesia, tearing was essentially zero in both groups.

Anesthesia, Inhalation↗
PubMed1979

Kindling phenomenon: impairment by auditory stimuli.

By coupling kindling stimuli with tones, it is shown that kindled epileptiform activity is not easily classically conditioned such that it can be evoked by an auditory stimulus. On the contrary, a tone presented 400 msec before and during the kindling stimulus impedes the rate of kindling.

Acoustic Stimulation↗
PubMed1979

Ketamine kinetics: decerebrate vs. intact cats.

Pharmacokinetic parameters of a ketamine (10 mg/kg, iv) bolus in decerebrate and intact cats were compared. A two-compartment open model best described the data in both groups. The apparent volume of distribution of the peripheral compartment, the apparent volume of distribution of the drug in the body, and the half-life of the postdistributive phase were significantly less (p less than 0.05) in the decerebrate animals. These results emphasize the importance of correlating behavior and neuronal activity with plasma or blood concentrations of drug in animals rather than assuming that, for a given drug dose, blood (and thus tissue) levels of the agent will be similar regardless of how the animal is prepared for study.

Animals↗