The free energy of biomembrane and nerve excitation and the role of anesthetics.

In the electromechanical theory of nerve stimulation, the nerve impulse consists of a traveling region of solid membrane in a liquid environment. Therefore, the free energy necessary to stimulate a pulse is directly related to the free energy difference necessary to induce a phase transition in the nerve membrane. It is a function of temperature and pressure, and it is sensitively dependent on the presence of anesthetics which lower melting transitions. We investigate the free energy difference of solid and liquid membrane phases under the influence of anesthetics. We calculate stimulus-response curves of electromechanical pulses and compare them to measured stimulus-response profiles in lobster and earthworm axons. We also compare them to stimulus-response experiments on human median nerve and frog sciatic nerve published in the literature.

Phyto-anesthetics: A mini-review on herb-anesthesia drug interactions.

Over the years studies have shown the high prevalence rate in the use of herbal drugs among patients, doctors and health workers as such there is a need to take care of any health consequences associated with herbal drugs administrations. Herbal drugs are made of pharmacologically effective constituents, that can interact with anesthesia drugs that risk the life of the patients in question. In addition, pharmacokinetics and pharmacodynamics of herbal drugs are yet to be fully understood thus still needs more study. In view of this anesthesiologist should take a thorough history of the patient in question, taking into full consideration earlier use of herbal medicine/drugs by the patient. The aim of this article is to provide a mini-review on herb-anesthesia drug interactions.

A transmembrane amino acid in the GABAA receptor ß2 subunit critical for the actions of alcohols and anesthetics.

Alcohols and inhaled anesthetics enhance the function of GABA(A) receptors containing α, ß, and γ subunits. Molecular analysis has focused on the role of the α subunits; however, there is evidence that the ß subunits may also be important. The goal of our study was to determine whether Asn265, which is homologous to the site implicated in the α subunit (Ser270), contributes to an alcohol and volatile anesthetic binding site in the GABA(A) receptor ß(2) subunit. We substituted cysteine for Asn265 and exposed the mutant to the sulfhydryl-specific reagent octyl methanethiosulfonate (OMTS). We used two-electrode voltage-clamp electrophysiology in Xenopus laevis oocytes and found that, after OMTS application, GABA-induced currents were irreversibly potentiated in mutant α(1)ß(2)(N265C)γ(2S) receptors [but not α(1)ß(2)(I264C)γ(2S)], presumably because of the covalent linking of octanethiol to the thiol group in the substituted cysteine. It is noteworthy that this effect was blocked when OMTS was applied in the presence of octanol. We found that potentiation by butanol, octanol, or isoflurane in the N265C mutant was nearly abolished after the application of OMTS, suggesting that an alcohol and volatile anesthetic binding site at position 265 of the ß(2) subunit was irreversibly occupied by octanethiol and consequently prevented butanol or isoflurane from binding and producing their effects. OMTS did not affect modulation or direct activation by pentobarbital, but there was a partial reduction of allosteric modulation by flunitrazepam and alphaxalone in mutant α(1)ß(2)(N265C)γ(2S) receptors after OMTS was applied. Our findings provide evidence that Asn265 may contribute to an alcohol and anesthetic binding site.

[Surgery patients' intake of herbal preparations and dietary supplements]. / Kirurgiske patienters indtagelse af naturlaegemidler og kosttilskud.

INTRODUCTION: Herbal medicine is being frequently used by patients around the world. Several products may interact with ordinary medicine, so it is important for doctors to know what kind of herbal medicines their patients take. MATERIAL AND METHODS: A questionnaire was given to presurgery patients during a two-month period. RESULTS: A total of 115 consecutive patients responded, 69 women (60%) and 46 men (40%). 50.4% had taken or still took herbal medicine, with the following distribution of gender: women 69.8%, men 30.2%. The age group was 18-82 years. The frequently used herbal medicines were fish oil, ginkgo, Echinacea, Co-Q10, garlic, and hip. Twenty-five patients took nutritional supplements with the following spread of gender: 84% women and 16% men. The frequently used nutritional supplements were Gerimax, LongoVital, and Melbrosia. Not all patients would inform their doctor about their use of herbal medicine. 28.6% retained information because of the doctor and 64.3%, did not perceive herbal medicine as "real medicine". DISCUSSION: It is important for anaesthesiologists to know what specific kind of herbal medicines patients are using before they anaesthetize them as interactions between herbal medicine and anaesthesia are prevalent. Anaesthesiologists have to ask specific questions to receive full information regarding herbal medicines during the preoperative period.

Use of yohimbine to reverse prolonged effects of xylazine hydrochloride in a horse being treated with chloramphenicol.

A 1-year-old Standardbred gelding had received xylazine hydrochloride (0.75 to 1.00 mg/kg [0.34 to 0.45 mg/lb] of body weight, IV) during 2 surgeries for debridement of a wound. The horse was given chloramphenicol (55 mg/kg [25 mg/lb], PO, q 6 h) for 5 days, and was anesthetized a third time with xylazine (0.75 mg/kg, IM). Five hours after administration of xylazine, the horse remained markedly sedated and had clinical signs of gaseous distention of the large bowel (bloat) requiring trocharization. Administration of yohimbine (0.03 mg/kg [0.01 mg/lb], i.v.) eliminated signs of sedation within 5 minutes. Moderate flatulence developed, and gastrointestinal sounds could be heard within all 4 abdominal quadrants within 15 minutes of yohimbine administration. The remainder of recovery was unremarkable. Xylazine induces bradycardia and decreases gastrointestinal motility in addition to causing sedation, muscle relaxation, and analgesia. Chloramphenicol can inhibit oxidase activity of cytochrome P-450 and inhibit metabolism and elimination of drugs such as xylazine.

[Passage of propofol in the colostrum. Preliminary data]. / Passage du propofol dans le colostrum. Données préliminaires.

So as to ascertain whether propofol passed into human milk, a study was carried out in five women who had undergone general anaesthesia with propofol in the puerperium. Concentrations of propofol were measured both in plasma and colostrum. The results showed clearly the excretion of propofol in the colostrum, and the similar time-courses of propofol levels in the blood and colostrum; the ratio of concentrations blood:colostrum was close to 1.