Superior gallstone dissolubility and safety of tert-amyl ethyl ether over methyl-tertiary butyl ether

BACKGROUND

The use of methyl-tertiary butyl ether (MTBE) to dissolve gallstones has been limited due to concerns over its toxicity and the widespread recognition of the safety of laparoscopic cholecystectomy. The adverse effects of MTBE are largely attributed to its low boiling point, resulting in a tendency to evaporate. Therefore, if there is a material with a higher boiling point and similar or higher dissolubility than MTBE, it is expected to be an attractive alternative to MTBE.

AIM

To determine whether tert-amyl ethyl ether (TAEE), an MTBE analogue with a relatively higher boiling point (102 °C), could be used as an alternative to MTBE in terms of gallstone dissolubility and toxicity.

METHODS

The in vitro dissolubility of MTBE and TAEE was determined by measuring the dry weights of human gallstones at predetermined time intervals after placing them in glass containers with either of the two solvents. The in vivo dissolubility was determined by comparing the weights of solvent-treated gallstones and control (dimethyl sulfoxide)-treated gallstones, after the direct infusion of each solvent into the gallbladder in both hamster models with cholesterol and pigmented gallstones.

RESULTS

The in vitro results demonstrated a 24 h TAEE-dissolubility of 76.7%, 56.5% and 38.75% for cholesterol, mixed, and pigmented gallstones, respectively, which represented a 1.2-, 1.4-, and 1.3-fold increase in dissolubility compared to that of MTBE. In the in vitro experiment, the 24 h-dissolubility of TAEE was 71.7% and 63.0% for cholesterol and pigmented gallstones, respectively, which represented a 1.4- and 1.9-fold increase in dissolubility compared to that of MTBE. In addition, the results of the cell viability assay and western blot analysis indicated that TAEE had a lower toxicity towards gallbladder epithelial cells than MTBE.

CONCLUSION

We demonstrated that TAEE has higher gallstone dissolubility properties and safety than those of MTBE. As such, TAEE could present an attractive alternative to MTBE if our findings regarding its efficacy and safety can be consistently reproduced in further subclinical and clinical studies.

The Perfect and Famous Anesthetic Known as Methyl in Boston in 1895

Extravagant claims were made for proprietary dental anesthetics in Boston, MA, in the late 1800s. For instance, in 1883, Urial K. Mayo introduced an inhaled Vegetable Anaesthetic comprised of nitrous oxide that had been uselessly pretreated with botanical material. This misguided concept may have been inspired by homeopathy, but it was also in line with the earlier false belief of Elton R. Smilie, Charles T. Jackson, and William T.G. Morton that sulfuric ether could volatilize opium at room temperature. In 1895, the Dental Methyl Company advertised an agent they called Methyl, a supposedly perfect topical anesthetic for painless dental extraction. The active ingredient was probably chloroform. Anesthetic humbug did not cease in Boston on Ether Day of October 16, 1846.

Ether Anesthesia in the Austere Environment: An Exposure and Education

Medical services in the austere and limited environment often require therapeutics and practices uncommon in modern times due to a lack of availability, affordability, or expertise in remote areas. In this setting, diethyl ether, or simply ether anesthesia, still serves a role today as an effective inhalation agent. An understanding of ether as an anesthetic not only illustrates the evolution in surgical anesthesia but also demonstrates ether's surviving function and durable use as a practical agent in developing nations. Although uncommon, it is not unseen, so a working knowledge should be understood if observation and advocacy for patients receiving this method of anesthesia are experienced.

Obstetric and Other Uses of Ether Before Ether Day, According to the Boston Medical and Surgical Journal of 1828-1846

From the inception of the Boston Medical and Surgical Journal in 1828 until the prominent public demonstration of surgical anesthesia on Ether Day of 1846, ether was often mentioned in the journal. Many of the examples were related to obstetrics. Because molecular structures were not available in the early 1800s, diverse volatile liquids were termed ethers. In addition to sulphuric ether, so-called ethers included cyanide-releasing propionitrile and ethanolic solutions of chloroform and of the potent vasodilator ethyl nitrite. Familiarity with anesthetically unsuitable ethers may have long deterred consideration of inhaled sulphuric ether for analgesia and anesthesia.

The outlook of physician histories: J. Marion Sims and 'The Discovery of Anaesthesia'

The fact that doctors have a long tradition of writing medical history to interpret and direct their profession is well established. But readers (particularly modern physician readers) can also understand physician-authored histories as offering commentary and analysis of the world beyond medicine. In this essay, we offer a reading (perhaps a modern one) of J. Marion Sims's 1877 article, 'The Discovery of Anaesthesia' which exemplifies the stance of looking both inward and outward from the medical field. We begin by discussing Sims, including the complicated legacy he left as a physician. Next, we review late 19th-century history with a focus on Reconstruction. Finally, we show how the modern reader can use Sims's article both to trace the first use of ether and nitrous oxide for surgical anaesthesia and to provide a window into the 19th-century medical profession and the post-Civil War period. Through this study, we hope to show how to read both medicine and the world around it in physician histories.

Ether in the developing world: rethinking an abandoned agent

BACKGROUND

The first true demonstration of ether as an inhalation anesthetic was on October 16, 1846 by William T.G. Morton, a Boston dentist. Ether has been replaced completely by newer inhalation agents and open drop delivery systems have been exchanged for complicated vaporizers and monitoring systems. Anesthesia in the developing world, however, where lack of financial stability has halted the development of the field, still closely resembles primitive anesthetics.

DISCUSSION

In areas where resources are scarce, patients are often not given supplemental intraoperative analgesia. While halothane provides little analgesia, ether provides excellent intra-operative pain control that can extend for several hours into the postoperative period. An important barrier to the widespread use of ether is availability. With decreasing demand, production of the inexpensive inhalation agent has fallen. Ether is inexpensive to manufacture, and encouraging increased production at a local level would help developing nations to cut costs and become more self-sufficient.

Uptake and efflux of rhenium in cells exposed to rhenium diseleno-ether and tissue distribution of rhenium and selenium after rhenium diseleno-ether treatment in mice

We proposed a new water-soluble rhenium diseleno-ether compound (with one atom of Re and two atoms of Se) and investigated the uptake of Re into the nucleus of malignant cells in culture exposed to the compound for 48 h and its efflux from the nucleus after a post-exposure period of 48 h, as DNA is the main target of Re. We also studied the distribution of both Re and Se in the main organs after an oral administration of 10 or 40 mg/kg Re diseleno-ether to mice for four weeks, five days-a-week.

MATERIALS AND METHODS

Re and Se concentrations were assayed by inductively coupled plasma mass spectrometry (ICP-MS). Statistical analysis was performed using the Wilcoxon signed-rank test, comparing two related groups.

RESULTS

We observed that Re was well incorporated into the nucleus of malignant cells in the most sensitive cells MCF-7, derived from human breast cancer, and that there was no efflux of Re. In contrast, in MCF-7 resistant cells (MCF-7 Mdr and MCF-7 R), A549 and HeLa cells, there was significant efflux of Re from the nucleus after the wash-out period. In mice, an important and dose-dependent uptake of both Re and Se was observed in the liver, with lower concentrations in kidneys. The lowest concentrations were observed in blood, lung, spleen and bones. There was a significant increase of Re concentrations in the blood, liver and kidney in mice treated with Re diseleno-ether at the dose of 40 mg/kg/24 h versus those treated at the dose of 10 mg/kg/24 h. There was a significant increase of Se concentrations in all tissues with the dose of Re diseleno-ether of 10 mg/kg/24 h versus controls, and a significant increase in the liver in mice treated with dose of Re diseleno-ether of 40 mg/kg/24h versus those treated with 10 mg/kg/24 h.

CONCLUSION

We are the first to demonstrate that a compound combining Re and Se in a single molecule, is able to deliver Re and Se to the organism via an oral route, for cancer treatment.

In vitro and in vivo efficacy of ether lipid edelfosine against Leishmania spp. and SbV-resistant parasites

Background

The leishmaniases are a complex of neglected tropical diseases caused by more than 20 Leishmania parasite species, for which available therapeutic arsenal is scarce and unsatisfactory. Pentavalent antimonials (SbV) are currently the first-line pharmacologic therapy for leishmaniasis worldwide, but resistance to these compounds is increasingly reported. Alkyl-lysophospoholipid analogs (ALPs) constitute a family of compounds with antileishmanial activity, and one of its members, miltefosine, has been approved as the first oral treatment for visceral and cutaneous leishmaniasis. However, its clinical use can be challenged by less impressive efficiency in patients infected with some Leishmania species, including L. braziliensis and L. mexicana, and by proneness to develop drug resistance in vitro.

Methodology/Principal Findings

We found that ALPs ranked edelfosine>perifosine>miltefosine>erucylphosphocholine for their antileishmanial activity and capacity to promote apoptosis-like parasitic cell death in promastigote and amastigote forms of distinct Leishmania spp., as assessed by proliferation and flow cytometry assays. Effective antileishmanial ALP concentrations were dependent on both the parasite species and their development stage. Edelfosine accumulated in and killed intracellular Leishmania parasites within macrophages. In vivo antileishmanial activity was demonstrated following oral treatment with edelfosine of mice and hamsters infected with L. major, L. panamensis or L. braziliensis, without any significant side-effect. Edelfosine also killed SbV-resistant Leishmania parasites in in vitro and in vivo assays, and required longer incubation times than miltefosine to generate drug resistance.

Conclusions/Significance

Our data reveal that edelfosine is the most potent ALP in killing different Leishmania spp., and it is less prone to lead to drug resistance development than miltefosine. Edelfosine is effective in killing Leishmania in culture and within macrophages, as well as in animal models infected with different Leishmania spp. and SbV-resistant parasites. Our results indicate that edelfosine is a promising orally administered antileishmanial drug for clinical evaluation.

Leishmaniasis represents a major international health problem, has a high morbidity and mortality rate, and is classified as an emerging and uncontrolled disease by the World Health Organization. The migration of population from endemic to nonendemic areas, and tourist activities in endemic regions are spreading the disease to new areas. Unfortunately, treatment of leishmaniasis is far from satisfactory, with only a few drugs available that show significant side-effects. Here, we show in vitro and in vivo evidence for the antileishmanial activity of the ether phospholipid edelfosine, being effective against a wide number of Leishmania spp. causing cutaneous, mucocutaneous and visceral leishmaniasis. Our experimental mouse and hamster models demonstrated not only a significant antileishmanial activity of edelfosine oral administration against different wild-type Leishmania spp., but also against parasites resistant to pentavalent antimonials, which constitute the first line of treatment worldwide. In addition, edelfosine exerted a higher antileishmanial activity and a lower proneness to generate drug resistance than miltefosine, the first drug against leishmaniasis that can be administered orally. These data, together with our previous findings, showing an anti-inflammatory action and a very low toxicity profile, suggest that edelfosine is a promising orally administered drug for leishmaniasis, thus warranting clinical evaluation.

Evidence for TREK-like tandem-pore domain channels in intrapulmonary chemoreceptor chemotransduction

Intrapulmonary chemoreceptors (IPC) are carbon dioxide sensing neurons that innervate the lungs of birds, control breathing pattern, and are inhibited by halothane and intracellular acidosis. TASK and TREK are subfamilies of tandem-pore domain potassium leak channels, important in setting resting membrane potential, that are affected by volatile anesthetics and acidosis. We hypothesized that such channels might underlie signal transduction in IPC. We treated mallard ducks with four volatile anesthetics in increasing concentrations to test their effects on IPC discharge through single cell, extracellular recording from vagal fibers. Isoflurane inhalation attenuated IPC discharge only at 8.25% inspired (alpha=0.05). Halothane attenuated IPC discharge significantly (alpha=0.05) at all treatment levels. Chloroform at 3.8%, 5.6%, and 8.25% significantly attenuated IPC discharge (alpha=0.05). Ether at 1.9%, 2.9%, and 3.8% significantly attenuated IPC discharge (alpha=0.05), abolishing IPC discharge at 3.8% inspired. The pharmacological signature of IPC discharge attenuation suggests that IPC express tandem-pore domain leak channels similar to TREK channels, which are inhibited by intracellular acidosis.

Secretory phospholipase A2 as a tumor-specific trigger for targeted delivery of a novel class of liposomal prodrug anticancer etherlipids

The use of many common clinically relevant chemotherapeutics is often limited due to insufficient delivery to the tumor and dose-limiting systemic toxicities. Therefore, therapeutics that specifically target tumor cells and are nontoxic to normal cells are required. Here, we report the development of a novel class of liposomes composed of lipid prodrugs, which use the increased secretory phospholipase A2 type IIA (sPLA2) activity of the tumor microenvironment as a trigger for the release of anticancer etherlipids (AEL). Treatment of sPLA2-secreting tumor cells in vitro with liposomes consisting of proAELs resulted in growth inhibition comparable with addition of the AELs alone. Using a specific sPLA2 inhibitor, we showed the low cytotoxicity of the nonhydrolyzed proAEL liposomes and have proven the sPLA2 dependency of the activation of proAELs to cytotoxic AELs. In addition, we showed that our proAEL liposomes circumvent the inherent hemolytic toxicities associated with the use of etherlipids, thereby allowing i.v. administration of such therapeutics as nontoxic prodrug liposomes. Furthermore, using a sPLA2-secreting human colon cancer xenograft model, we showed that the proAEL liposomes are capable of inducing a tumor growth delay in vivo. Taken together, these data support the validity of this novel tumor-selective liposomal prodrug delivery strategy. This new approach also provides a promising system for tumor-selective delivery and release of conventional chemotherapeutics encapsulated in the sPLA2-degradable prodrug liposomes.

Correlation of bispectral index and Guedel's stages of ether anesthesia

Bispectral index (BIS) analysis is a method of electroencephalograph (EEG) analysis based on the interfrequency phase relationships of the EEG, designed to quantify anesthetic hypnosis. The BIS was created after concurrent collection of EEG and clinical data from a large number of patients anesthetized with various drugs over a prolonged period and then performing a Fourier analysis followed by a bispectral calculation. The clinical stages of anesthetic depth are very well demonstrated in etherized patients. In this study, we studied the BIS changes during various stages of ether anesthesia and quantified the hypnotic depth during the surgical stage of ether anesthesia. The values for BIS under various stages and planes of ether anesthesia were recorded in 21 patients listed for short surgical procedures. During diethyl ether anesthesia, BIS initially increased and subsequently decreased. During surgical anesthesia, a BIS value of 30 was observed.

IMPLICATIONS

For the first time, bispectral index (BIS) has been studied in patients being anesthetized solely with ether. Ether both causes an increase and decrease in BIS during induction and emergence. The index observed during the surgical stage of ether anesthesia is probably the correct value for the depth of hypnosis because no other volatile anesthetic can produce the true anesthetic state when used alone. This value could be taken as the value to be attained when balanced anesthesia is being practiced.

[Immuno-corticotropin interactions in a nociceptive environment in the Wistar rat]

In pregnant rats, oral administration of ammonium nitrate, stress with ether and antigenic stimulation were found to induce immune variations, hormonal changes and evince the organism's capacities of detoxification. An activation of the immune system and immunosuppression have been recorded respectively during xenobiotics administration and antigenic stimulation, and during stress. Corticotrophe response occurred on the 6th day of gestation and was more pronounced from the 12th day onwards in animals receiving ammonium nitrate. At the end of the gestation period, however, the corticotrophe response became stable in treated animals. Ammonium nitrate administration seemed to drive a major toxicity effect, clearly observed through increased levels of methemoglobine and coincided with a significant decrease in the level of glutathione, confirming a mechanism of detoxification.

Startin's pneumatic inhaler

This apparatus was seen by one of us (DAW) in a private collection. Although it was one of the first ether inhalers to be manufactured commercially, and was described in the medical literature of the time, it is not mentioned in any of the histories of anaesthesia. Its genesis was unusual, and it presents a number of interesting features, not least being the purpose for which it was originally designed.

Endocrine stress response in jugular-vein cannulated rats upon multiple exposure to either diethyl-ether, halothane/O2/N2O or sham anaesthesia

The main objective of this study was to assess the endocrine stress response to multiple anaesthesia followed by sham anaesthesia in order to detect any memory effects. For this purpose, jugular-vein cannulated rats were subjected to either sham, diethyl-ether or halothane/O2/N2O anaesthesia, and their plasma ACTH, corticosterone, glucose, adrenaline and noradrenaline levels measured. The study had three separate experiments, each consisting of a control and treatment group. In two experiments, the rats were exposed to high or low concentrations (40-15%) of diethyl ether, using either a jar containing cotton soaked in diethyl ether or a vaporizer. In the third experiment, rats were exposed to halothane/O2/N2O. Control animals underwent sham anaesthesia. Blood samples were taken 6 min before and at 5, 15 and 55 min after starting the exposure (t = 0 min). For each variable, the dt5 (level at t = 5 min minus that at t = -6 min) and the cumulative levels over the one-hour period as determined by the area under the curve (AUC) were calculated. Further, the peak levels (Cmax) were determined. The mean time needed to induce anaesthesia was 68, 121 and 55 s for exposure to high and low concentrations of diethyl ether and to halothane/O2/N2O, respectively. Increased noradrenaline and adrenaline dt5 levels were observed only after the first exposure to the high concentration of diethyl ether. Multiple anaesthesia sessions using either diethyl ether or halothane/O2/N2O did not clearly influence adrenaline and noradrenaline levels. Diethyl ether induced a sharp rise in plasma ACTH and glucose levels, irrespective of the concentration used. The response of the ACTH and glucose was similar for single and multiple exposure. An increased response of ACTH, corticosterone and glucose to sham anaesthesia following multiple induction of anaesthesia was observed for the high concentration of diethyl ether only. Halothane/O2/N2O raised plasma glucose without differences between single and multiple anaesthesia sessions. Upon sham anaesthesia following multiple exposures to halothane/O2/N2O, glucose levels were significantly increased. This study indicates that repeated anaesthesia in rats can elicit an increased stress response during subsequent handling and change of environment.

[When anesthesia came to Norway]

On 16 October 1846, William T.G. Morton performed the first successful demonstration of ether anaesthesia. The news quickly spread to Europe; reports reached the Scandinavian countries in early 1847. The first ether anaesthesia was administered in Norway at Rikshospitalet, the teaching hospital of the only Norwegian university at the time, on 4 March 1847. The number of surgical procedures increased; medical practice was changed.

An ether stressor increases REM sleep in rats: possible role of prolactin

Sleep alterations after a 1-min exposure to ether vapor were studied in rats to determine if this stressor increases rapid eye-movement (REM) sleep as does an immobilization stressor. Ether exposure before light onset or dark onset was followed by significant increases in REM sleep starting approximately 3-4 h later and lasting for several hours. Non-REM (NREM) sleep and electroencephalographic slow-wave activity during NREM sleep were not altered. Exposure to ether vapor elicited prolactin (Prl) secretion. REM sleep was not promoted after ether exposure in hypophysectomized rats. If the hypophysectomy was partial and the rats secreted Prl after ether exposure, then increases in REM sleep were observed. Intracerebroventricular administration of an antiserum to Prl decreased spontaneous REM sleep and inhibited ether exposure-induced REM sleep. The results indicate that a brief exposure to ether vapor is followed by increases in REM sleep if the Prl response associated with stress is unimpaired. This suggests that Prl, which is a previously documented REM sleep-promoting hormone, may contribute to the stimulation of REM sleep after ether exposure.

Inhaled anesthetics have hyperalgesic effects at 0.1 minimum alveolar anesthetic concentration

We investigated the hyperalgesic (antianalgesic) effect of the inhaled anesthetics isoflurane, halothane, nitrous oxide, and diethyl ether, or the nonimmobilizer 1, 2-dichlorohexafluorocyclobutane at subanesthetic partial pressures (or, for the nonimmobilizer, subanesthetic partial pressures predicted from lipid solubility) in rats. Hyperalgesia was assessed as a decrease in the time to withdrawal of a rat hind paw exposed to heat. All four anesthetics, including nitrous oxide and diethyl ether, produced hyperalgesia at low partial pressures, with a maximal effect at 0.1 minimum alveolar anesthetic concentration (MAC) required to prevent response to movement in 50% of animals, and analgesia (an increased time to withdrawal of the hind paw) at 0. 4 to 0.8 MAC. The nonimmobilizer had neither analgesic nor hyperalgesia effects. We propose that inhaled anesthetics with a higher MAC-Awake (the MAC-fraction that suppresses appropriate responsiveness to command), such as nitrous oxide and diethyl ether, can be used as analgesics because patients are conscious at higher anesthetic partial pressures, including those which have analgesic effects, whereas anesthetics with a lower MAC-Awake do not produce analgesic effects at concentrations that permit consciousness.

IMPLICATIONS

The inhaled anesthetics isoflurane, halothane, nitrous oxide, and diethyl ether produce antianalgesia at subanesthetic concentrations, with a maximal effect at approximately one-tenth the concentration required for anesthesia. This effect may enhance perception of pain when such small concentrations are reached during recovery from anesthesia.

Diazepam-like effects of a fish protein hydrolysate (Gabolysat PC60) on stress responsiveness of the rat pituitary-adrenal system and sympathoadrenal activity

RATIONALE

Gabolysat PC60 is a fish protein hydrolysate with anxiolytic properties commonly used as a nutritional supplement.

OBJECTIVE

The diazepam-like effects of PC60 on stress responsiveness of the rat pituitary-adrenal system and on sympathoadrenal activity were studied.

METHODS

The activity of the pituitary-adrenal axis, measured by plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone (B) of the sympathoadrenal complex, measured by circulating levels of noradrenaline (NA) and adrenaline (A), and the gamma aminobutyric acid (GABA) content in the hippocampus and the hypothalamus were investigated in male rats which received daily, by an intragastric feeding tube, for 5 days running either diazepam (1 mg/kg) or PC60 (300 or 1,200 mg/kg). Controls received only solvent (carboxymethylcellulose 1%). Six hours after the last force-feeding, the rats were subjected to 3 min ether inhalation or 30 min restraint and killed by decapitation 30 min after ether stress or at the end of restraint.

RESULTS

Baseline plasma levels of ACTH, B, NA and A were not affected by either diazepam or PC60. Both ether- and restraint-induced release of ACTH, but not B, were similarly and drastically reduced by diazepam and PC60 (1,200 mg/kg). Both diazepam and PC60 (1,200 mg/kg) deleted restraint-induced NA and A increases. Both treatments also reduced the ether-induced rise of A. Basal levels of GABA were significantly increased in both the hippocampus and the hypothalamus in PC60-treated rats and only in the hippocampus in diazepam-treated ones. In controls, ether inhalation as well as restraint increased GABA content of these two brain structures. In contrast, such stress procedures performed in PC60-treated rats reduced GABA content slightly in the hippocampus but significantly in the hypothalamus. In diazepam-treated rats, GABA content of the hypothalamus was unaffected by stresses but that of the hippocampus was slightly decreased.

CONCLUSIONS

Present data suggest diazepam-like effects of PC60 on stress responsiveness of the rat pituitary adrenal axis and the sympathoadrenal activity as well as GABA content of the hippocampus and the hypothalamus under resting and stress conditions. These effects of PC60 agree with anxiolytic properties of this nutritional supplement, previously reported in both rats and humans.

[Phenomenology of ether administration. With a review of the literature]

A 45-year-old man was found dead lying on a sofa in his house. He had pulled a plastic bag over his head, the bag containing a pad of cotton-wool soaked with diethylether. Different aspects are discussed in this paper including a review of the literature: anamnesis, scene of death, utensils used for inhalation and autopsy findings. There are especially pointed out the results of chemical-toxicological analyses in many body compartments. Furthermore are interpreted the manners and the relations of the distribution of ether as well as possible effects on the consciousness. In consideration of other published cases, the analytical results concerning ether are discussed with regard to the presumed cause of death (e.g. asphyxia) and other potential competitive mechanisms.

Near fatal respiratory distress following massive ether intravenous injection

To the best of our knowledge, no case of ether-induced acute respiratory distress syndrome (ARDS) has been published as yet. A 36-year-old female developed pneumonitis which showed all the characteristics of a chemical-associated ARDS due to intravenous self-administration of ether: the hemodynamic investigation demonstrated a normal blood flow pattern with low left-heart filling pressure while the anteroposterior roentgenogram evidenced disseminated bilateral lung edema. Advanced symptomatic respiratory support including inhaled nitric oxide and steroidal anti-inflammatory use was the treatment of choice.

Skin and plasma levels of acetylsalicylic acid: a comparison between topical aspirin/diethyl ether mixture and oral aspirin in acute herpes zoster and postherpetic neuralgia

OBJECTIVE

The aim of this investigation was to elucidate whether the analgesic effect was due to the local aspirin or to the systemic drug. This was done by comparing skin and plasma levels of acetylsalicylic acid (ASA) and salicylic acid (SA) after topically administered ASA/diethyl ether (ADE) mixture in acute herpetic neuralgia (AHN) and postherpetic neuralgia (PHN). The analgesia and the plasma and skin levels of ASA were also determined after oral administration of aspirin.

METHODS

Nineteen patients, 11 (57.9%) with AHN and 8 (42.1 %) with PHN were given, on different days, a single 500-mg oral dose of ASA or a topical dose (750 mg) of (ADE) daubed onto the painful skin. The analgesic effect was assessed by means of a visual analogue scale (VAS). Overall pain relief was graded as: excellent, good, fair, or poor. AHN as well as PHN patients had severe pain at baseline (6.83 and 5.93). Levels of ASA and SA in plasma and in the stratum corneum after adhesive tape stripping of the treated area were determined by HPLC.

RESULTS

After ADE application, the analgesic effect was very rapid and VAS scores were lower than at baseline. Pain significantly decreased by 82.6% after topical and 15.4% after oral ASA. After ADE, 95% of the patients had excellent or good pain relief, but after oral administration 79% of the patients had a poor response. Pain relief was similar in the two subgroups after ADE. Skin concentrations of ASA, but not of SA, after ADE were about 80- to 100-fold those after oral administration. Levels of ASA and SA in plasma after oral administration were similar to those previously found, but after ADE were undetectable or very low. Patients with excellent pain relief showed a trend towards higher ASA skin concentrations.

CONCLUSIONS

The analgesic effect can be obtained only after topical administration, because by this route the skin levels of ASA are much higher than after oral administration. The mechanism is exclusively local; there are no active drugs in plasma after topical administration.

A model to investigate postoperative ileus with strain gauge transducers in awake rats

BACKGROUND

Postoperative ileus influences patients well-being, hospital stay, and health cost, and postoperative inhibition of colonic motility is a major contributor to postoperative ileus. Experimental models for investigating postoperative ileus are needed. In particular, recording of postoperative colonic motility in awake rats has not been described yet.

MATERIAL AND METHODS

Gastric, small intestinal, and colonic motility were recorded with strain gauge transducers in awake rats, and the effects of anesthesia and abdominal surgery on gastrointestinal motility were investigated.

RESULTS

Ether anesthesia increased gastric motility and inhibited small intestinal motility, while enflurane anesthesia had only minor effects on gastrointestinal motility. Abdominal surgery inhibited gastric, small intestinal, and colonic motility, and a detailed analysis of gastrointestinal motility in our postoperative ileus model is given.

CONCLUSIONS

We established a model to record gastric, small intestinal, and colonic motility in awake rats postoperatively. We could demonstrate that enflurane anesthesia had little effect on gastrointestinal motility, while laparotomy and short manipulation of the cecum produced a prolonged inhibition of gastrointestinal motility. Our model could be used to investigate postoperative ileus, particularly of the colon, in awake rats.

Characteristics of the proopiomelanocortin system in the outdoor-bred domestic gander. II. Seasonal and circadian rhythmicity; effect of ether stress and lipopolysaccharide administration

The responsiveness of the POMC system to exogenous stimuli and the diurnal and seasonal rhythmicity of ACTH and beta-endorphin (beta E) in plasma were studied in outdoor-reared domestic ganders. Plasma levels of ACTH- and beta E-like immunoreactivities were determined by direct and specific radioimmunoassays. In the first series of experiments immunoreactive (ir) ACTH and beta E were measured in the plasma of male domestic geese after 5 min of ether stress and after administration of 2 micrograms/kg lipopolysaccharide (LPS). Both ir-ACTH and ir-beta E levels increased 5 and 10 min after ether inhalation, but the increase in the ir-beta E concentration was only half that of the ir-ACTH. The plasma ir-ACTH levels were elevated after 60 and 120 min but not after 90 min of LPS administration: ir-beta E levels were unchanged at all time points. In a second series of experiments blood samples were taken on 30 March. 16 June, 4 August, and 27 October. On these days diurnal samplings were performed at 02:00, 06:00, 10:00, 14:00, 18:00, and 22:00 h. A two-way analysis of variance showed significant diurnal and seasonal changes for both hormones and significant interaction between the diurnal and seasonal levels. The highest daily mean values of the plasma ir-ACTH and ir-beta E concentrations were measured in June. The maximum of the ir-ACTH level was at 10:00 h in March and August, but at 22:00 h in June and October. The changes in ir-beta E concentrations paralleled those of ir-ACTH, but the changes did not reach statistical significance in every case.

Influence of halothane-diethyl-ether azeotrope and isoflurane on ventilation. Re-evaluation of an obsolete drug

The azeotropic mixture of halothane and diethyl-ether has been claimed to be a suitable anaesthetic agent for use during difficult conditions because of its negligible effect on circulation and ventilation. The purpose was to evaluate the effect of halothane-diethyl-ether azeotrope (HE) and isoflurane (ISO) on ventilation. 12 patients scheduled to undergo minor orthopaedic surgery and belonging to ASA 1, were randomly allocated to the HE group or the ISO group. Evaluation of resting ventilation and ventilation stimulated by hypercarbia and hypoxaemia was done on three occasions: (A) before anaesthesia, (B) after inhalational induction of anaesthesia and intubation without muscle relaxants when the level of anaesthesia was 1 MAC and (C) half an hour after operation and during recovery. Resting ventilation and the ventilatory response to hypercarbia during anaesthesia were maintained in the HE group but not in the ISO group, whereas the ventilatory response to hypoxaemia during anaesthesia was absent in both groups. The responses had returned to normal values in both groups during recovery. We conclude that halothane-diethyl-ether azeotrope is comparatively safe during anaesthesia with spontaneous breathing provided arterial oxygenation is adequate. This makes this azeotrope suitable for use by anaesthetists with limited experience and during difficult conditions such as civil disaster or war.

Liver function and halothane-diethyl-ether azeotrope anaesthesia. Re-evaluation of an obsolete drug with special reference to early postoperative effects

A general anaesthetic drug that fulfils requirements for use under difficult circumstances is the inhalation agent halothane-diethyl-ether (HE) azeotrope. Although both halothane and diethyl ether have been described in detail, their effect on the liver when given together as an azeotrope has not been systematically characterised. The effect on liver function was evaluated and compared with the effects of halothane anaesthesia (H) and spinal anaesthesia with tetracaine (S), the last named serving as controls. The series consisted of 33 healthy men (ASA 1-2) receiving no medication and scheduled for inguinal hernia repair. The patients were randomly allocated to receive HE, H or S. The following parameters were estimated the day before surgery and on the first postoperative day: liver cell metabolism (bile acids, unconjugated bilirubin), cell integrity (aminotransferases), synthesizing capacity (Prothrombin complex), cholestasis (conjugated bilirubin, alkaline phosphatase, gamma-glutamyl transpeptidase), and global liver function (chenodeoxycholic load test). No major differences emerged between the groups. Unconjugated bilirubin was increased in all groups. Prothrombin complex activity was reduced in all groups. Conjugated bilirubin was increased in the H group. The oral bile acid load test and the fasting bile acid were unaltered by anaesthesia in all groups. No major impact on liver cell function was seen in the early post-operative period after HE azeotrope anaesthesia. The findings support our view that HE azeotrope could be considered as an alternative anaesthetic agent under field conditions.

Staurosporine, a protein kinase C inhibitor, decreases the general anesthetic requirement in Rana pipiens tadpoles

Protein kinase C, the intracellular effector for the inositol phosphate-mediated signal transduction pathway, plays a key role in neurotransmission in the central nervous system. Although the in vitro activity of protein kinase C is inhibited by therapeutic concentrations of volatile anesthetics, the relation of this effect to in vivo obtundation has not been established. If obtundation by volatile anesthetics involves protein kinase C inhibition, then an inhibitor of this enzyme should decrease the anesthetic requirement. To test this hypothesis, we compared the EC50S of halothane and diethylether for loss of the righting reflex in Rana pipiens tadpoles pretreated with staurosporine and in untreated controls. Anesthetic concentrations were confirmed by gas chromatography and staurosporine concentrations by ultraviolet absorbance spectrophotometry. Results obtained in more than 1000 animals indicated that pretreatment with staurosporine concentrations in the nanomolar range significantly decreased the EC50 for both halothane (68% of control; P < 0.035) and diethylether (41% of control; P < 0.001). This finding implies that protein kinase C inhibition may play a role in general anesthetic-induced obtundation.

Effects of inhalation of ethyl-ether on glycemia and on some variables of intermediate metabolism in rats

The influence of a anesthetic, ethyl-ether, on arterial plasma levels of glucose, insulin and lipids was studied in starved Wistar rats. Ethyl-ether increased significantly (P < 0.05) glucose plasma levels, as a result not only of stress and of the release of catecholamines and glucocorticoids, but also of the decrease in the use of glucose by the tissues. Ethyl-ether did not change significantly the level of triglycerides, cholesterol and phospholipids. Insulin concentration was not increased, even when hyperglycemia was established. Ketonuria, acidosis and hypercapnia were increased. In these rats the administration of insulin produced a diminution in glycemia. The findings suggest that, under anesthesia with ether, the endocrine pancreas is incapable of recognizing glucose as a specific stimulus to promote the release of insulin.

A new topical treatment for acute herpetic neuralgia and post-herpetic neuralgia: the aspirin/diethyl ether mixture. An open-label study plus a double-blind controlled clinical trial

Topical aspirin/diethyl ether (ADE) mixture was used to treat 45 consecutive patients with acute herpetic neuralgia (AHN) (n = 28) and with post-herpetic neuralgia (PHN) (n = 17) in an open-label study. Good-to-excellent results were achieved by 93% of AHN patients and by 65% of PHN patients. Earlier treatment yielded better results for the AHN but not the PHN group. The topical treatment seemed to accelerate the healing of acute herpetic skin lesions and possibly modulate the severity of the herpetic infection. Furthermore, a striking reduction in the percentage of AHN patients developing PHN was observed in the treated group, as compared with the disease natural history reported in the literature (4 vs. 50-70%). Treatment tolerance was excellent with no adverse effect observed. In addition to the open trial, a pilot double-blind crossover placebo-controlled study (n = 11) compared the analgesic efficacy of ADE with two other NSAID (indomethacin and diclofenac) drug/ether mixtures. Aspirin (but not indomethacin and diclofenac) was significantly superior to placebo as regards pain relief (P less than 0.05).

Effect of CGS 19755, a competitive N-methyl-D-aspartate antagonist, on general anesthetic potency

CGS 19755 is a competitive N-methyl-D-aspartate (NMDA) receptor antagonist which penetrates the blood-brain barrier. The effect of pretreatment with subanesthetic doses of CGS 19755 on general anesthetic potency was determined in mice. Mice were pretreated with saline or CGS 19755 by intraperitoneal (IP) administration 30 min before IP administration of an anesthetic dose of ethanol or pentobarbital or measurement of the volatile anesthetic minimum alveolar concentration (MAC). CGS 19755 increased the duration of ethanol- and pentobarbital-induced loss of righting reflex in a dose-dependent manner. The highest dose of CGS 19755 tested, 50 mg/kg, increased duration of loss of righting reflex by about four- and twofold for ethanol and pentobarbital, respectively. CGS 19755 also decreased the MAC for halothane. However, CGS 19755 pretreatment had no effect on the MAC for diethyl ether. These results suggest that the potency of certain general anesthetic agents can be increased by antagonism of brain NMDA receptors.

Central circulation during halothane-diethyl-ether azeotrope and isoflurane anaesthesia in the pig

The fatal anaesthetic ratio (FAR) has been determined for halothane-diethyl-ether (HE) in pigs, and the central circulation during hypovolaemia has been investigated using a well-documented agent such as isoflurane as a standard. The fatal anaesthetic ratio for HE in pigs was (3.21/1.03) = 3.12. This is high compared to the FAR for halothane of 1.7. The central circulation was investigated in 12 pigs which were randomly allocated to either HE or isoflurance anaesthesia, respectively. Baseline values were recorded when they were stable at 1.3 MAC of the volatile anaesthetic used. The pigs were bled 30% of their blood volume, and measurements were made at 5 and 30 min. There was one significant difference between these groups in central circulation: the blood pressure was higher at baseline measurement in the HE group. At 5 min and 30 min, there were no significant differences between these groups. There was a general depression of central circulation without any sign of decreased contractility. HE anaesthesia is well tolerated during hypovolaemia in pigs.

[An approach to removing stains and remineralization of dental fluorosis]

341 mottled teeth were bleached with 4% and 18% hydrochloric acid; the mixture of 36% hydrochloric acid, 30% hydrogen peroxide and anesthetic ether; and 30% hydrogen peroxide warmed by infra-red ray lamp. The effects were evaluated clinically. The extracted mottled and normal teeth were treated with the methods mentioned above. The decolouration effects, the structural changes of tooth surface, and the remineralization were examined by scanning electronmicroscopy and polaroid microscopy. The results showed: all of the four methods had the decolouration effects; the decolouration effect was better in the teeth with higher mineralization and the pigmentation existed more superficially; complete decolouration was 94.8% and lightened cases were 5.2%. The mechanism of decolouration seemed to be the dissolution of tooth superficial layer containing pigment. The decalcified tooth surface might be recalcified by the treatment of recalcification solution, or by saliva itself.

Minimum alveolar concentration of halothane-diethyl-ether azeotrope

The azeotropic mixture of halothane and diethyl ether (HE) may be a valuable alternative to other anaesthetic agents under circumstances such as war, civil disaster, and primitive conditions. In the present study the minimum alveolar concentrations (MACs) for HE in man (n = 25) and in pigs (n = 6) were determined. For comparison with results of other studies, the MAC for halothane in man (n = 14) was also determined. A Normac gas analyser and a Varian 3700 gas chromatograph were calibrated against known standards of HE. The performance of two vaporizers (Fluotec Mark III, Servo vaporizer for halothane) was studied. The Fluotec Mark III vaporizer and the Servo halothane vaporizer filled with HE gave a linear performance with increasing dial settings. The Normac gas analyser set for methoxyflurane was linearly sensitive to the ether component of the azeotrope. The MAC for HE in man was 0.71 vol.% +/- 0.03 (s.e.mean) (ether 0.21 vol.%, halothane 0.50 vol.%) in the age group 19-42 years. MAC for halothane in man was 0.65 +/- 0.03 in the age group 19-32 years. The MAC for HE in pigs between 20-24 kg was 0.99 vol.% +/- 0.07. The ether component seems to act synergistically with halothane in the azeotropic mixture. The present study provides an opportunity to compare HE with other volatile anaesthetic agents.