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Biomedical subjects

M A Curran

Publications and source records attributed to M A Curran.

10 recordsLinked to original sources

Progesterone potentiation of bupivacaine arrhythmogenicity in pentobarbital-anesthetized rats and beating rat heart cell cultures.

The effects of progesterone treatment on bupivacaine arrhythmogenicity in beating rat heart myocyte cultures and on anesthetized rats were determined. After determining the bupivacaine AD50 (the concentration of bupivacaine that caused 50% of all beating rat heart myocyte cultures to become arrhythmic), we determined the effect of 1-hour progesterone HCl exposure on myocyte contractile rhythm. Each concentration of progesterone (6.25, 12.5, 25, and 50 micrograms/ml) caused a significant and concentration-dependent reduction in the AD50 for bupivacaine. Estradiol treatment also increased the arrhythmogenicity of bupivacaine in myocyte cultures, but was only one fourth as potent as progesterone. Neither progesterone nor estradiol effects on bupivacaine arrhythmogenicity were potentiated by epinephrine. Chronic progesterone pretreatment (5 mg/kg/day for 21 days) caused a significant increase in bupivacaine arrhythmogenicity in intact pentobarbital-anesthetized rats. There was a significant decrease in the time to onset of arrhythmia as compared with control nonprogesterone-treated rats (6.2 +/- 1.3 vs. 30.8 +/- 2.5 min, mean +/- SE). The results of this study indicate that progesterone can potentiate bupivacaine arrhythmogenicity both in vivo and in vitro. Potentiation of bupivacaine arrhythmia in myocyte cultures suggests that this effect is at least partly mediated at the myocyte level.

Anesthesia

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Albuterol

Barbiturate anesthesia and alcohol tolerance in a rat model.

Anesthetic responses to a variety of barbiturates were examined in adult male rats rendered alcohol-tolerant by administration of an ethanol-containing balanced liquid diet for 3 weeks. Within 9 hours of withdrawing the diets, groups of 10-15 ethanol-fed rats and pair-fed controls were injected intraperitoneally with one of the following drug/dose combinations: thiamylal 20, 40, or 60 mg/kg; methohexital 10, 20, or 40 mg/kg; secobarbital 20, 30, or 40 mg/kg; pentobarbital 10, 20, or 40 mg/kg; or phenobarbital 80, 120, or 160 mg/kg. Each animal was monitored for time to loss of righting reflex (onset of anesthesia), absence of response to a painful stimulus (analgesia), and sleeping time (duration of anesthesia). None of these three anesthetic responses differed significantly in ethanol-fed and control rats with any dose of thiamylal, methohexital, or secobarbital. In contrast, all three responses were significantly less in rats given the middle dose of pentobarbital (20 mg/kg) than they were in control rats. Onset and duration of anesthesia were also shorter with the middle dose of phenobarbital (120 mg/kg), but analgesia was not. The results of this study, in combination with others, suggest that 1) cross-tolerance to anesthetic effects of barbiturates in ethanol-tolerant rats is not uniform with all barbiturates: and 2) because shorter-acting barbiturates show negligible cross-tolerance with alcohol, higher doses of these agents may not be required for satisfactory anesthesia in chronically alcoholic humans.

Animals

Gambling away absenteeism.

Current conditions in health care make the battle against absenteeism critical. Of all the various methods devised, one seems to be consistently effective: positive reinforcement through a simple lottery incentive system. The authors describe this system's impact on reducing absenteeism.

Absenteeism

The management of epilepsy in women of child-bearing age and the Australian experience of valproate in pregnancy.

Published opinion is reviewed and summarized with special reference to the teratogenic potential of the newer anticonvulsant drugs, treatment decisions and patient supervision. An Australian report covering a period of eight years, summarizing congenital malformations in births to patients whose treatment included sodium valproate (EpilimR) is presented against the background of the WHO report on valproate and pregnancy.

Abnormalities, Drug-Induced

Effects of chronic alcohol intake on anesthetic responses to diazepam and thiopental in rats.

The effect of chronic alcohol intake on anesthetic responses to alcohol, thiopental, or diazepam was examined in adult male Sprague-Dawley rats. Alcohol-fed animals were maintained solely on a complete balanced liquid diet containing 6.54% ethanol (w/w) for 21 days; pair-fed control animals received equal amounts of the same diet with alcohol isocalorically replaced by sucrose or dextrin. Nine hours after diets were withdrawn on the twenty-second day, the following drug/dose combinations were administered intraperitoneally to separate groups of alcohol-fed and control rats (10-15 animals in each group): ethanol 2.4, 3.2, and 4.0 g/kg; thiopental 20, 40, and 80 mg/kg; and diazepam 10, 20, and 40 mg/kg. Three different responses were assessed in every animal: 1) loss of righting reflex (induction of anesthesia); 2) response to a painful stimulus (analgesia); and 3) sleeping time (duration of anesthesia). Alcohol-fed rats compared with controls were significantly less tolerant of pain at an acute alcohol dose of 2.4 g/kg, and loss of righting reflex and sleeping time were reduced at 4.0 g/kg. All three anesthetic responses were also attenuated in alcohol-fed rats at a diazepam dose of 20 mg/kg. In contrast, none of the three responses was reduced in alcohol-fed rats at any of the three thiopental doses. Thus, chronic alcohol intake sufficient to produce tolerance to anesthetic doses of alcohol in rats also produced cross-tolerance to diazepam but not to thiopental in equianesthetic doses. These results suggest that blanket recommendations for adjusting intravenous anesthetic dosages in alcoholic humans may be inadequate as guides to anesthetic management.

Alcoholism