[Health hazards resulting from occupational exposure to enfluran - overview of tests and analysis of admissible concentration values]. / Zagrozenia zdrowotne wynikajace z narazenia zawodowego na enfluran ­ przeglad badan i próba analizy wartosci dopuszczalnych stezen.

The aim of this work is to analyze the health hazards of enflurane exposure and to analyze the occupational exposure limits (OEL). The method of obtaining evidence based on a review of online databases of scientific journals was used. Enflurane is an inhalation anesthetic. Malignant hyperthermia, seizures, arrhythmias, respiratory depression and hypotension have been observed in patients. Occupational exposure to enflurane may occur in healthcare professionals. The target organ for enflurane is the central nervous system with a critical consequence of deterioration in psychomotor performance. In studies on volunteers recruited from the medical staff of operating rooms exposed to enflurane, a significant deterioration in the results of the Simple Reaction Time Test was shown. World experts' groups assume that the LOAEC (lowest observed adverse effect concentration) value for the deterioration of psychomotor test results is 5-10% of the MAC value (minimal anesthetic concentration), i.e., 6342-12 684 mg/m3. Assessment of the nephrotoxic potential of enflurane has shown that it is unlikely to occur because biotransformation of enflurane in humans results in a low peak serum fluoride concentration of 15 µmol/l. Early reports about liver damage in patients were not be supported. Occupational exposure epidemiological studies have raised concerns about the effects of anesthetic gas mixtures on the abortion rate or on fetal development and birth defects in children, but none of these studies specifically determined the type and concentration of anesthetic gases used. The carcinogenicity and mutagenicity studies were negative. Occupational exposure to enflurane is not monitored in Poland, as no standard value has been established for it in the air of the working environment. It is necessary to quickly introduce this anesthetic along with the applicable limit value to the OEL list. Med Pr. 2022;73(1):51-69.

[Determination of Sevoflurane, Isoflurane and Enflurane in the air of workplace by gas chromatography].

Objective: To establish a solvent desorption gas chromatographic method for determination of Sevoflurane, Isoflurane and Enflurane in the air of the Workplace. Methods: Sevoflurane, Isoflurane and Enflurane were collected with activated carbon tube and desorbed with dichloromethane, separated with DB-1 capillary columns, and then detected with flame ionization detector. Results: The linearity ranges were 1.9-304.8 µg/ml for Sevoflurane, 2.1-300.4 µg/ml for Isoflurane and 1.7-305.2 µg/ml for Enflurane, The correlation coefficient was both >0.999. Their limits of detection were 0.6 µg/ml, 0.6 µg/ml and 0.5 µg/ml, and Their limits of quatification were 1.9 µg/ml, 2.1 µg/ml and 1.7 µg/ml, and their minimum detectable concentrations were 0.1、0.2 and 0.1 mg/m(3) per 4.5 L of air. Their relative standard deviations (RSD) were 2.5%-3.0%, 2.3%-3.1% and 2.2%-3.0%. The average desorption efficiencies were 101.1%-103.3%, 100.7%-102.7% and 101.0%-102.9%. The sampling efficiency was both 100%. The breakthrough volume of 100 mg actived carbon was 3.7 mg, 3.4 mg and 3.4 mg. Sevoflurane, Isoflurane and Enflurane in activated carbon tube could be kept at least 10 days at room temperature without significant losses. Conclusion: The method shows lower detection limit, high accuracy and precision. It is feasible for determination of Sevoflurane, Isoflurane and Enflurane in the air of workplace.

Programmable Peptide-Cross-Linked Nucleic Acid Nanocapsules as a Modular Platform for Enzyme Specific Cargo Release.

Herein we describe a modular assembly strategy for photo-cross-linking peptides into nucleic acid functionalized nanocapsules. The peptides embedded within the nanocapsules form discrete nanoscale populations capable of gating the release of molecular and nanoscale cargo using enzyme-substrate recognition as a triggered release mechanism. Using photocatalyzed thiol-yne chemistry, different peptide cross-linkers were effectively incorporated into the nanocapsules and screened against different proteases to test for degradation specificity both in vitro and in cell culture. By using a combination of fluorescence assays, confocal and TEM microscopy, the particles were shown to be highly specific for their enzyme targets, even between enzymes of similar protease classes. The rapid and modular nature of the assembly strategy has the potential to be applied to both intracellular and extracellular biosensing and drug delivery applications.

Cardiac Calcium Release Channel (Ryanodine Receptor 2) Regulation by Halogenated Anesthetics.

BACKGROUND: Halogenated anesthetics activate cardiac ryanodine receptor 2-mediated sarcoplasmic reticulum Ca release, leading to sarcoplasmic reticulum Ca depletion, reduced cardiac function, and providing cell protection against ischemia-reperfusion injury. Anesthetic activation of ryanodine receptor 2 is poorly defined, leaving aspects of the protective mechanism uncertain. METHODS: Ryanodine receptor 2 from the sheep heart was incorporated into artificial lipid bilayers, and their gating properties were measured in response to five halogenated anesthetics. RESULTS: Each anesthetic rapidly and reversibly activated ryanodine receptor 2, but only from the cytoplasmic side. Relative activation levels were as follows: halothane (approximately 4-fold; n = 8), desflurane and enflurane (approximately 3-fold,n = 9), and isoflurane and sevoflurane (approximately 1.5-fold, n = 7, 10). Half-activating concentrations (Ka) were in the range 1.3 to 2.1 mM (1.4 to 2.6 minimum alveolar concentration [MAC]) with the exception of isoflurane (5.3 mM, 6.6 minimum alveolar concentration). Dantrolene (10 µM with 100 nM calmodulin) inhibited ryanodine receptor 2 by 40% but did not alter the Ka for halothane activation. Halothane potentiated luminal and cytoplasmic Ca activation of ryanodine receptor 2 but had no effect on Mg inhibition. Halothane activated ryanodine receptor 2 in the absence and presence (2 mM) of adenosine triphosphate (ATP). Adenosine, a competitive antagonist to ATP activation of ryanodine receptor 2, did not antagonize halothane activation in the absence of ATP. CONCLUSIONS: At clinical concentrations (1 MAC), halothane desflurane and enflurane activated ryanodine receptor 2, whereas isoflurane and sevoflurane were ineffective. Dantrolene inhibition of ryanodine receptor 2 substantially negated the activating effects of anesthetics. Halothane acted independently of the adenine nucleotide-binding site on ryanodine receptor 2. The previously observed adenosine antagonism of halothane activation of sarcoplasmic reticulum Ca release was due to competition between adenosine and ATP, rather than between halothane and ATP.

Serotonin, estrus, and social context influence c-Fos immunoreactivity in the inferior colliculus.

A fundamental task of sensory systems is to extract relevant social information from a range of environmental stimuli in the face of changing behavioral contexts and reproductive states. Neuromodulatory pathways that interact with such contextual variables are 1 mechanism for achieving this. In the mouse inferior colliculus (IC), a midbrain auditory region, the neuromodulator serotonin increases in females interacting with courting males, but events downstream of serotonin release have not been investigated. Here, we manipulated serotonin levels in female mice with the serotonin releaser fenfluramine or the serotonin depleter para-chlorophenylalaninemethyl ester (pCPA). Females were then exposed to an empty cage, a male partner, or a playback of courtship vocalizations, and the numbers of neurons in the IC with positive immunoreactivity for the immediate early gene product c-Fos were measured. The effects of drug treatments depended on social context and estrous state. Fenfluramine had greater effects in the nonsocial than in the partner social treatments. Females in proestrus or estrus and given fenfluramine had higher densities of c-Fos immunoreactive neurons, while females in diestrus had fewer immunoreactive neurons. The drug pCPA had the expected opposite effect of fenfluramine, causing a decreased response in pro/estrus females and an increased response in diestrus females. These findings show that the effects of serotonin on c-Fos activity in the IC of females is dependent on both external context and reproductive state, and suggest that these effects occur downstream of serotonin release. (PsycINFO Database Record

Effects of maternal enflurane exposure on NR2B expression in the hippocampus of their offspring

This work aims to study the pathogenesis of learning and memory impairment in offspring rats resulting from maternal enflurane anesthesia by focusing on the expression of the N-methyl-d-aspartic acid receptor subunit 2B (NR2B) in the hippocampus of the offspring. Thirty female Sprague-Dawley rats were randomly divided into three groups: control (C group), 4 h enflurane exposure (E1 group), and 8 h enflurane exposure (E2 group) groups. Eight to ten days after the initiation of pregnancy, rats from the E1 and E2 groups were allowed to inhale 1.7% enflurane in 2 L/min oxygen for 4 h and 8 h, respectively. Rats from the C group were allowed to inhale 2 L/min of oxygen only. The Morris water maze was used to assay the learning and memory function of the offspring on postnatal days 20 and 30. RT-PCR and immunohistochemistry assays were then used to measure the mRNA levels and protein expression of NR2B, respectively. Relative to offspring rats from the C group, those from the E1 and E2 groups exhibited longer escape latencies, lesser number of crossings over the platform, and less time spent in the target quadrant in the spatial exploration test (P < 0.05). In addition, the mRNA and protein expression levels of NR2B in the hippocampus of offspring rats in the E1 and E2 groups were down-regulated (P < 0.05). No significant differences between the E1 and E2 groups were observed (P > 0.05) in terms of mRNA levels and protein expression of NR2B. The cognitive function of the offspring is impaired when maternal rats are exposed to enflurane during early pregnancy. A possible mechanism of this effect is related to the down-regulation of NR2B expression.

Este trabalho objetiva o estudo da patogênese de deficiência no aprendizado e memória de prole de ratos resultante da anestesia maternal por enflurano, por meio da expressão da subunidade 2B do receptor do ácidoN-metil-D-aspártico (NR2B) no hipocampo dos filhotes. Dividiram-se, aleatoriamente, 30 fêmeas de ratos Sprague-Dawley em três grupos: controle (grupo C), exposição ao enflurano por 4 h (grupo E1) e por 8 h (grupo E2). De oito a 10 dias após o início da gravidez, os ratos dos grupos E1 e E2 inalaram enflurano 1,7% em 2 L/min de oxigênio, por 4 h e 8 h, respectivamente. Ratos do grupo C inalaram apenas 2 L/min de oxigênio. O labirinto de água de Morris foi empregado para analisar as funções de aprendizado e memória da cria em 20 e 30 dias após o nascimento. Utilizaram-se ensaios de RT-PCR e de imuno-histoquímica para medir os níveis de mRNA e expressão da proteína do NR2B, respectivamente. Em comparação com os ratos controle do grupo C, aqueles dos grupos E1 e E2 exibiram latências de escape mais longas, menor número de travessias na plataforma e menos tempo gasto no quadrante alvo no teste de exploração espacial (P < 0,05). Adicionalmente, os níveis de expressão de mRNA e de proteína do NR2B no hipocampo dos filhotes nos grupos E1 e E2 estavam reduzidos (P < 0,05). Não se observaram diferenças significativas entre os grupos E1 e E2 (P < 0,05) quanto aos níveis de mRNA e à expressão de proteína de NR2B. A função cognitiva dos filhotes é prejudicada quando as mães são expostas ao enflurano durante o início da gravidez. O mecanismo possível para esse efeito está relacionado à diminuição na expressão de NR2B.

Influence of propofol, isoflurane and enflurance on levels of serum interleukin-8 and interleukin-10 in cancer patients.

OBJECTIVE: To observe the influence of propofol, isoflurane and enflurance on interleukin-8 (IL-8) and IL-10 levels in cancer patients. METHODS: Ninety cancer patients with selective operation from March 2011 to May 2014 were randomly divided into group A (34 cases), group B (28 cases) and group C (28 cases). Intramuscular injections of scopine hydrochloride and phenobarbital sodium were routinely conducted to 3 groups. After general anesthesia was induced, tracheal intubations were given. During the maintenance of anesthesia, 0.5~1.0 mg/ kg propofol was intravenously injected to group A discontinuously, while continuous suctions of isoflurane and enflurance were subsequently performed to group B and C correspondingly. Clinical outcomes, postoperative complications as well as serum IL-8 and IL-10 levels before operation (T0), at the time of skin incision (T1), 3 h after the beginning of the operation (T2) and 24 h (T3) and 72 h (T4) after the operation were observed among 3 groups. RESULTS: Operations in all groups were successfully completed. The rates of surgery associated complications were 8.82% (3/34), 7.14% (2/28) and 7.14% (2/28) in group A, B and C, respectively, and there were no significant differences (P>0.05). Serum IL-8 and IL-10 levels increased gradually from the beginning of the operation and reached the peak at T3, and were evidently higher at each time point than at T0 (P<0.01). At T1, serum IL-8 and IL-10 levels had no significant differences among 3 groups (P<0.05), but the differences were significant at T2, T3 and T4 (P<0.05). Moreover, correlation analysis suggested that serum IL-8 level was in positive relation with IL-10 level (r=0.952, P<0.01). CONCLUSIONS: Propofol, which is better in inhibiting serum IL-8 secretion and improving IL-10 secretion than isoflurane and enflurance, can be regarded as a preferable anesthetic agent in inhibiting traumatic inflammatory responses.

Ventilation/perfusion ratios measured by multiple inert gas elimination during experimental cardiopulmonary resuscitation.

BACKGROUND: During cardiopulmonary resuscitation (CPR) the ventilation/perfusion distribution (VA /Q) within the lung is difficult to assess. This experimental study examines the capability of multiple inert gas elimination (MIGET) to determine VA /Q under CPR conditions in a pig model. METHODS: Twenty-one anaesthetised pigs were randomised to three fractions of inspired oxygen (1.0, 0.7 or 0.21). VA/ Q by micropore membrane inlet mass spectrometry-derived MIGET was determined at baseline and during CPR following induction of ventricular fibrillation. Haemodynamics, blood gases, ventilation distribution by electrical impedance tomography and return of spontaneous circulation were assessed. Intergroup differences were analysed by non-parametric testing. RESULTS: MIGET measurements were feasible in all animals with an excellent correlation of measured and predicted arterial oxygen partial pressure (R(2) = 0.96, n = 21 for baseline; R(2) = 0.82, n = 21 for CPR). CPR induces a significant shift from normal VA /Q ratios to the high VA /Q range. Electrical impedance tomography indicates a dorsal to ventral shift of the ventilation distribution. Diverging pulmonary shunt fractions induced by the three inspired oxygen levels considerably increased during CPR and were traceable by MIGET, while 100% oxygen most negatively influenced the VA /Q. Return of spontaneous circulation were achieved in 52% of the animals. CONCLUSIONS: VA /Q assessment by MIGET is feasible during CPR and provides a novel tool for experimental purposes. Changes in VA /Q caused by different oxygen fractions are traceable during CPR. Beyond pulmonary perfusion deficits, these data imply an influence of the inspired oxygen level on VA /Q. Higher oxygen levels significantly increase shunt fractions and impair the normal VA /Q ratio.

Salient features of enantioselective gas chromatography: the enantiomeric differentiation of chiral inhalation anesthetics as a representative methodological case in point.

The enantiomeric differentiation of the volatile chiral inhalation anesthetics enflurane, isoflurane, and desflurane by analytical and preparative gas chromatography on various modified cyclodextrins is described. Very large enantioseparation factors α are obtained on the chiral selector octakis(3-O-butanoyl-2,6-di-O-pentyl)-γ-cyclodextrin (Lipodex E). The gas-chromatographically observed enantioselectivities are corroborated by NMR-spectroscopy using Lipodex E as chiral solvating agent and by various sensor devices using Lipodex E as sensitive chiral coating layer. The assignment of the absolute configuration of desflurane is clarified. Methods are described for the determination of the enantiomeric distribution of chiral inhalation anesthetics during narcosis in clinical trials. The quantitation of enantiomers in a sample by the method of enantiomeric labeling is outlined. Reliable thermodynamic parameters of enantioselectivity are determined by using the retention-increment R' approach for the enantiomeric differentiation of various chiral halocarbon selectands on diluted cyclodextrin selectors.

Airway management using a supraglottic airway device without endotracheal intubation for positive ventilation of anaesthetized rats.

Endotracheal intubation is often necessary for positive pressure ventilation of rats during open thoracic surgery. Since endotracheal intubation in rats is technically difficult and is associated with numerous complications, many techniques using various devices have been described in the scientific literature. In this study, we compared the effectiveness of airway management of a home-made supraglottic airway device (SAD), which is cheap to fabricate and easy to place with that of an endotracheal intubation tube in enflurane-anaesthetized rats. Twenty male Sprague-Dawley rats (200-300 g) were randomly assigned to two equal groups for positive pressure mechanical ventilation using either the SAD or an endotracheal intubation tube. The carotid artery of each rat was cannulated for continuous blood pressure measurements and obtaining blood samples for determination of oxygen tension, carbon dioxide tension, and blood acidity before, during and after SAD placement or endotracheal intubation. Proper placement of the SAD was confirmed by observing chest wall movements that coincided with the operation of the mechanical ventilator. No complications and adverse events were encountered in the rats in which the SAD was placed, during SAD placement and immediate removal, during their mechanical ventilation through the SAD, and one week after SAD removal. From the results of blood gas analyses, we conclude that anaesthetized rats can be successfully ventilated using an SAD for open thoracic surgery.

Comparação entre o enflurano e o propofol na eletroconvulsoterapia: um estudo preliminar, aleatório, aberto e cruzado sobre a duração de convulsões e a recuperação anestésica / Comparison of enflurane and propofol in electroconvulsive therapy, a randomized crossover open preliminary study on seizure duration and anaesthetic recovery

JUSTIFICATIVA E OBJETIVOS: A eletroconvulsoterapia (ECT) é comumente utilizada para o tratamento de depressão, mania e transtornos do humor. Anestésicos para anestesia geral durante a ECT devem ter início e despertar rápidos, não interferir com a atividade da convulsão e não encurtar a duração das crises. O objetivo deste estudo é comparar os efeitos do enflurano, um agente anestésico pró-convulsivo, e o propofol na duração das ocnvulsões, no índice de supressão pós-ictal e nos tempos de recuperação durante a eletroconvulsoterapia. MÉTODO: Pacientes sem uso de medicação pré-anestésica foram alocados em dois grupos de acordo com a indução da anestesia. Os pacientes foram induzidos para a ECT com 5 por cento de enflurano no grupo E e 1,2 mg.kg-1 de propofol no grupo P, até perda de consciência. A duração das crises motora e no eletroencefalograma (EEG), o índice de supressão pós-ictal, o tempo para respiração espontânea, para duração da abertura dos olhos e obedecer aos comandos foram registrados. RESULTADOS: Não houve diferença estatisticamente significativa entre os grupos quanto aos tempos das crises motora e no EEG e índice de supressão pós-ictal nos registros de EEG. Tempos de recuperação (tempo de início de respiração espontânea, de abertura dos olhos e para obedecer aos comandos) foram significativamente menores no grupo E em relação ao grupo P. Não foram observados náuseas ou vômitos e nenhuma anormalidade no ECG, exceto bradicardia sinusal transitória e taquicardia sinusal. CONCLUSÕES: Embora convulsões suficientes para o tratamento tenham ocorrido durante a anestesia com enflurano, nenhum benefício adicional foi observado sobre os tempos de convulsão ou índice de supressão pós-ictal quando comparado à anestesia com propofol. Por outro lado, o tempo de recuperação após anestesia com enflurano foi mais curto que com propofol. No entanto, ainda há necessidade de mais estudos em diferentes níveis de ETCO2.

BACKGROUND AND OBJECTIVES: Electroconvulsive therapy (ECT) is commonly used for treatment of depression, mania and affective disorders. Anaesthetics for general anaesthesia during ECT should have rapid onset, rapid emerge, not interfere with seizure activity and not shorten seizure duration. The aim of this study is to compare effects of enflurane, a pro-convulsive anaesthetic agent, and propofol on seizure durations, postictal suppression index and recovery times during electroconvulsive therapy. METHODS: Unpremedicated subjects were divided into two groups according to induction of anaesthesia. Patients were induced for ECT with 5 percent enflurane in group E and 1.2 mg.kg-1 propofol in group P until loss of consciousness. The durations of electroencephalogram (EEG) and motor seizures, postictal suppression index, time to spontaneous breathing, duration of eye opening, and obeying commands were recorded. RESULTS: There was no statistically significant difference between the groups regarding motor and EEG seizure times and postictal suppression index on the EEG records. Recovery times (times of starting spontaneous breathing, eye opening, and obeying command) were significantly shorter in group E compared to group P. No nausea or vomiting were observed and no ECG abnormality was noted except transient sinus bradycardia and sinus tachycardia. CONCLUSIONS: Although sufficient seizure for the treatment was provided during enflurane anaesthesia, any additional benefit was not revealed regarding seizure times or postictal suppression index when compared to propofol anaesthesia. On the other hand, recovery times after enflurane anaesthesia were shorter than propofol anaesthesia. However, there is still a need for further study in different ETCO2 levels.

JUSTIFICATIVA Y OBJETIVOS: La electroconvulsoterapia (ECT), se usa a menudo para el tratamiento de la depresión, manía y transtornos del humor. Los anestésicos para la anestesia general durante la ECT deben tener un inicio y un despertar rápidos, no interferir en la actividad de la convulsión y no acortar la duración de las crises. El objetivo de este estudio, es comparar los efectos del enflurano, un agente anestésico pro convulsivo, y el propofol, en la duración de las convulsiones, en el índice de supresión postictal y en los tiempos de recuperación durante la electroconvulsoterapia. MÉTODO: Pacientes sin uso de medicación preanestésica que fueron colocados en dos grupos de acuerdo con la inducción de la anestesia. Los pacientes fueron inducidos para la ECT con 5 por ciento de enflurano en el grupo E y 1,2 mg.kg-1 de propofol en el grupo P, hasta la pérdida de la conciencia. También fueron registrados la duración de las crises motora y en el electroencefalograma (EEG), el índice de supresión postictal, el tiempo para la respiración espontánea, para la duración de la abertura de los ojos y obedecer a los comandos. RESULTADOS: No hubo diferencia estadísticamente significativa entre los grupos en cuanto a los tiempos de las crises motora y en el EEG e índice de supresión postictal en los registros de EEG. Los tiempos de recuperación (tiempo de inicio de la respiración espontánea, de abertura de los ojos, y para obedecer a los comandos), fueron significativamente menores en el grupo E con relación al grupo P. No se observaron náuseas o vómitos, ni ninguna anormalidad en el ECG tampoco fue notada, excepto bradicardia sinusal transitoria y taquicardia sinusal. CONCLUSIONES: Aunque las convulsiones suficientes para el tratamiento hayan sucedido durante la anestesia con enflurano, ningún beneficio adicional fue observado sobre los tiempos de convulsión o sobre el índice de supresión postictal cuando se le comparó con la anestesia con propofol. Por otro lado, el ti...

Halogen bonded complexes between volatile anaesthetics (chloroform, halothane, enflurane, isoflurane) and formaldehyde: a theoretical study.

The structures and intermolecular interactions in the halogen bonded complexes of anaesthetics (chloroform, halothane, enflurane and isoflurane) with formaldehyde were studied by ab initio MP2 and CCSD(T) methods. The CCSD(T)/CBS calculated binding energies of these complexes are between -2.83 and -4.21 kcal mol(-1). The largest stabilization energy has been found for the C-Br···O bonded halothane···OCH(2) complex. In all complexes the C-X bond length (where X = Cl, Br) is slightly shortened, in comparison to a free compound, and an increase of the C-X stretching frequency is observed. The electrostatic interaction was excluded as being responsible for the C-X bond contraction. It is suggested that contraction of the C-X bond length can be explained in terms of the Pauli repulsion (the exchange overlap) between the electron pairs of oxygen and halogen atoms in the investigated complexes. This is supported by the DFT-SAPT results, which indicate that the repulsive exchange energy overcompensates the electrostatic one. Moreover, the dispersion and electrostatic contributions cover about 95% of the total attraction forces, in these complexes.

In-vitro contracture testing for susceptibility to malignant hyperthermia: can halothane be replaced?

BACKGROUND: Malignant hyperthermia is a potentially lethal inherited hypermetabolic syndrome that develops in susceptible individuals following administration of depolarising neuromuscular relaxants or volatile anaesthetics. Genetic analysis can only confirm a diagnosis of malignant hyperthermia in about 70%, and in the remainder an in-vitro contracture test, with halothane and caffeine, on muscle obtained from open muscle biopsy is required to establish the diagnosis. As the licence for clinical use of halothane expired in 2005, its continuing availability is in doubt. More modern volatile anaesthetics such as enflurane, isoflurane, desflurane and sevoflurane are less potent triggers of malignant hyperthermia in humans and pigs. The aim of this study was to investigate whether these agents can be considered possible substitutes for halothane in a modified in-vitro contracture test. METHOD: With institutional review board approval and prior written consent, muscle bundles of 30 patients with a personal or family history of malignant hyperthermia were investigated. Of these, 13 were diagnosed malignant hyperthermia susceptible and 17 nonsusceptible. Surplus muscle was tested with increasing concentrations of enflurane, isoflurane, desflurane and sevoflurane. RESULTS: There were no differences in weight, length or predrug tension of the muscle bundles. At increasing concentration, all volatile anaesthetics except sevoflurane induced significantly greater contractures in malignant hyperthermia susceptible compared to malignant hyperthermia nonsusceptible muscle. In malignant hyperthermia susceptible muscle bundles, halothane led to significantly higher contractures compared to the other investigated substances. CONCLUSION: Halothane was the strongest discriminator for malignant hyperthermia in the in-vitro contracture tests. It remains the ideal substance for diagnostic testing and cannot simply be replaced by other agents in this test.

Nicotinic acetylcholine receptors mediate the hypnotic and analgesic effects of emulsified inhalation anesthetics.

This study was designed to investigate the role of nicotinic acetylcholine receptors (nAChRs) in hypnosis and analgesia induced by emulsified inhalation anesthetics. After having established the mice model of hypnosis and analgesia by intraperitoneal injections of appropriate doses of enflurane, isoflurane or sevoflurane, we intracerebroventricularly or intrathecally injected different doses of nicotine and then observed the effects on the sleeping time using awaken test and the pain threshold in hot-plate test (HPPT) using hot-plate test. In the awaken test, 10, 20 and 40 microg of nicotine (intracerebroventricularly) significantly decreased the sleeping time of the mice treated with the three emulsified inhalation anesthetics mentioned above (P < 0.05 or 0.01). In the HPPT, 5, 10 and 15 microg of nicotine (intrathecally) did not affect the HPPT in conscious mice (P > 0.05); in contrast, 5, 10 and 15 microg of nicotine (intrathecally) significantly decreased the HPPT of the mice treated with emulsified inhalation anesthetics (P < 0.05 or 0.01). The data presented in this study suggest that nAChRs may be important targets for the hypnotic and analgesic effects induced by emulsified enflurane, isoflurane and sevoflurane.

Comparison of effects of anaesthesia with desflurane and enflurane on liver function.

INTRODUCTION: Although most general anaesthesia procedures are performed without any complications, volatile agents may have adverse effects on various living systems. This study aimed to compare the effects of desflurane and enflurane on liver function. METHODS: 40 patients, who were in the ASA I-III risk groups and were planned to undergo head and neck surgery of at least three hours' duration, were randomly divided into two groups: the desflurane (Group D) and enflurane groups (Group E). Venous blood samples (5 ml) of the patients were obtained before anaesthesia induction, in the postoperative first hour and on the first and seventh days. The samples were centrifuged and then stored at -80 degrees Celsius until the determination of glutathione S-transferase (GST) levels. For maintenance of anaesthesia in Group D, desflurane (6 percent) was used, while in Group E, enflurane (1.2 percent) was used. RESULTS: GST levels were significantly higher in Group E in the postoperative first hour (p-value is 0.002), and on the first day (p-value is 0.025) and seventh day (p-value is 0.035), although there were no differences preoperatively (p-value is more than 0.05). When postoperative levels were compared with preoperative levels, the postoperative GST levels of Group E were significantly higher (first hour [p-value is 0.008], first day [p-value is 0.010], seventh day [p-value is 0.038]). CONCLUSION: Subclinical hepatic injury after anaesthesia continues to be an issue of interest, particularly with the development of new, more sensitive methods of measuring GST levels. The increase in GST concentration after anaesthesia is thought to be a result of reduced hepatic blood flow. This study has shown that desflurane has fewer effects than enflurane on liver function tests in lengthy operations of up to 330 minutes.

Pre-operative prediction of 'dry taps'.

OBJECTIVES: The treatment of children with 'glue ear' often presents surgeons with the question of whether or not to insert a grommet when myringotomy reveals no fluid in the middle ear. We present a study designed to assess which factors contribute to the presence of a 'dry tap'. DESIGN: We prospectively gathered data from a cohort of 280 children (504 myringotomies). The cohort included two subgroups, one received halothane and nitrous oxide anaesthesia, and the other received enflurane anaesthesia. SETTING: The ENT department of a district general hospital. PARTICIPANTS: Children (aged less than 17 years) requiring myringotomy. MAIN OUTCOME MEASURES: The presence of a 'glue' or dry tap at myringotomy was documented. We also recorded data on the following: pre- and post-induction tympanometry; age; season; anaesthetic type; and the delay from listing to actual operation. RESULTS: A non type B pre-induction tympanogram and delay to operation were strong indications of finding a dry tap at surgery. CONCLUSIONS: In our study population, the proportion of dry taps at myringotomy was 18 per cent. The presence of a dry tap was rarely due to the induction of anaesthesia. Multivariate analysis revealed that the combination of factors most likely to predict a dry tap were non type B tympanogram and delay to operation.

The effect on the recovery profile of a change from enflurane to desflurane during the latter part of anaesthesia.

This study compared emergence and recovery characteristics after either enflurane anaesthesia or crossover from enflurane to desflurane anaesthesia. At an estimated 1 h prior to the end of operation, enflurane was either reduced (group E, n = 23) or replaced with desflurane (group X, n = 23). At the end of the operation, emergence and recovery characteristics of the two groups were compared. The crossover technique accelerated recovery compared with enflurane anaesthesia. The time taken for the eyes to open in response to painful pinching or a verbal command, and to regain awareness of age and name, were significantly shorter after crossover anaesthesia than after enflurane anaesthesia. The digit symbol substitution test and serial seven test scores were significantly better in patients subjected to crossover anaesthesia than in those subjected to enflurane anaesthesia. We conclude that, during surgery, the substitution of enflurane with desflurane in the latter part of anaesthesia can improve recovery.

Myocardial metabolism altered by ischemic preconditioning and enflurane in off-pump coronary artery surgery.

OBJECTIVE: During off-pump coronary artery bypass (OPCAB) surgery, the heart is subjected to ischemia and reperfusion. The authors hypothesized that the volatile anesthetics are as effective as ischemic preconditioning (IPC) in preserving myocardial function during off-pump cardiac surgery, and this effect is because of multiple mechanisms of action. Therefore, the effects of enflurane with its calcium inhibition and antioxidative properties were compared with mechanical IPC in preserving myocardial cellular markers. DESIGN: A prospective, randomized, controlled, and partly blinded study. SETTING: A tertiary care university hospital. PARTICIPANTS: Twenty-five patients undergoing elective single-graft OPCAB surgery. INTERVENTIONS: Patients were randomized into 3 groups: (1) control (n = 8), (2) a single 5-minute ischemia/reperfusion interval of IPC before coronary occlusion (n = 9), and (3) 1.6% enflurane anesthesia 15 minutes before and during graft attachment (n = 8). Arterial and coronary sinus venous blood were analyzed for biochemical indices of ischemia and hydroxyl radical generation. MEASUREMENTS AND MAIN RESULTS: Although the hemodynamic changes were small, myocardial lactate production in the control group increased by 120%, whereas in the enflurane group it decreased significantly (p < 0.01) compared with the control and IPC groups. Oxygen utilization in the control group was 44% higher (p < 0.03), and there was also a larger release of the hydroxyl radical-dependent adduct 2,3-dihydroxybenzoic acid (225% increase, p < 0.05) compared with both study groups. During reperfusion, initial anterior wall hypokinesis by TEE was observed, with slow recovery during reperfusion compared with early recovery in both study groups. CONCLUSIONS: Coronary occlusion during OPCAB surgery results in increased production of ischemia-related metabolic products. The application of methods such as IPC or volatile anesthesia appears to reduce the metabolic deficit, free-radical production, and physiologic changes.

Enflurane requirement for blocking adrenergic responses to incision in infants and children.

BACKGROUND: Enflurane is one of the most commonly used inhaled anesthetics in China, but its requirement to block adrenergic responses after skin incision in pediatric patients is still unknown. This study was to determine the minimum alveolar anesthetic concentration (MAC) of potent inhaled anesthetics required to blunt the adrenergic response to skin incision of enflurane (MACBAR) in infants and children. METHODS: Twenty-eight patients, 10 infants (6-12 months) and 18 young children (1-6 years), were studied. The 18 children were randomly assigned into two groups, with or without fentanyl. Anesthesia was induced with 3 mg/kg propofol and 0.15 mg/kg vecuronium, and maintained with enflurane in 100% oxygen. Fentanyl (3 microg/kg) was given intravenously 5 minutes before incision for the patients of fentanyl group. The "up and down" method (with 0.3 MAC as a step size and 1 MAC as the start dose) was applied to determine MACBAR. The response was considered positive if the mean arterial pressure (MAP) or heart rate (HR) increased > or =15% after incision. The MACBAR was calculated as the mean of four independent cross-over responses in each group. RESULTS: MACBAR of enflurane in children of 1-6 years old was 3.2% (95% CI, 2.8%-3.6%) and was reduced to 2.2% (95% CI, 1.8%-2.5%) by 3 microg/kg fentanyl. In infants of 6-12 months old, the MACBAR of enflurane was 3.4% (95% CI, 3.0%-3.8%). CONCLUSIONS: MACBAR of enflurane in infants older than 6 months is similar to that in young children. The MACBAR of enflurane decreases with co-administration of fentanyl in the pediatric population.