Effect of magnesium sulfate on anesthesia depth, awareness incidence, and postoperative pain scores in obstetric patients. A double-blind randomized controlled trial.

OBJECTIVES: To assess the effects of magnesium on the depth of anesthesia and to determine the effects of magnesium on incidence of awareness and postoperative pain after caesarean section.  Methods: The study was designed as a double-blind, controlled, randomized study and conducted in Hacettepe University Hospital, Ankara, Turkey  between January 2015 and March 2016. A total of 100 pregnant healthy women who were between 17 and 41 years old, ASA II, and scheduled for an elective cesarean section with general anesthesia were included in the study. After induction, sevoflurane was used for maintenance in Group S and desflurane in Group D (control groups). At Group S-M and Group D-M (study groups), magnesium infusion was started with sevoflurane and desflurane anesthesia respectively. Minimum alveolar concentration of sevoflurane and desflurane were kept constant. Bispectral index scores (BIS), fentanyl consumption and postoperative visual analogue scale (VAS) values were recorded. All of the patients had been followed-up for awareness until the postoperative first year. Results: Demographic variables of the patients were similar. BIS values were significantly higher in control groups throughout the operation (p less than 0.001). No significant difference was detected for intraoperative fentanyl consumption and awareness incidence. VAS values were significantly lower in study groups (p less than 0.05). Conclusion: Magnesium infusion provided significantly lower intraoperative BIS values and lower postoperative VAS scores. We believe that magnesium can be useful as an adjuvant to general anesthesia.

Important role of calcium chloride in preventing carbon monoxide generation during desflurane degradation with alkali hydroxide-free carbon dioxide absorbents.

We investigated whether calcium chloride (CaCl2), a supplementary additive in carbon dioxide (CO2) absorbents, could affect carbon monoxide (CO) production caused by desflurane degradation, using a Japanese alkali-free CO2 absorbent Yabashi Lime®-f (YL-f), its CaCl2-free and 1% CaCl2-added derivatives, and other commercially available alkali-free absorbents with or without CaCl2. The reaction between 1 L of desflurane gas (3-10%) and 20 g of desiccated specimen was performed in an artificial closed-circuit anesthesia system for 3 min at 20 or 40 °C. The CO concentration was measured using a gas chromatograph equipped with a semiconductor sensor detector. The systems were validated by detecting dose-dependent CO production with an alkali hydroxide-containing CO2 absorbent, Sodasorb®. Compared with YL-f, the CaCl2-free derivative caused the production of significantly more CO, while the 1% CaCl2-added derivative caused the production of a comparable amount of CO. These phenomena were confirmed using commercially available absorbents AMSORB® PLUS, an alkali-free absorbent with CaCl2, and LoFloSorb™, an alkali-free absorbent without CaCl2. These results suggest that CaCl2 plays an important role in preventing CO generation caused by desflurane degradation with alkali hydroxide-free CO2 absorbents like YL-f.

Awakening properties of isoflurane, sevoflurane, and desflurane in pediatric patients after craniotomy for supratentorial tumours.

BACKGROUND: The aim of this prospective, comparative, randomized study was to compare the inhalational anesthetics isoflurane, sevoflurane, and desflurane in pediatric patients undergoing craniotomy for excision of supratentorial tumors. We assessed early postoperative recovery outcome, intraoperative hemodynamics, and degree of brain swelling, as well as postoperative vomiting and shivering. METHODS: Sixty patients scheduled for supratentorial brain tumor excision, were randomly allocated into 1 of 3 groups (20 patients each); isoflurane, sevoflurane, and desflurane group. After IV induction of anesthesia, maintenance was achieved using the inhalational anesthetic according to the allocated group. Tracheal extubation time was the primary endpoint. The secondary endpoints included: emergence time and the interval time needed to reach Aldrete score ≥9, intraoperative degree of brain swelling, intraoperative heart rate and mean arterial blood pressure, as well as postoperative vomiting and shivering. RESULTS: The mean emergence time, extubation time, and the interval required to reach Aldrete score 9 were significantly shorter in the desflurane and sevoflurane groups than the isoflurane group. No statistically significant changes in the 3 groups regarding intraoperative brain swelling, hemodynamics, and postoperative shivering or vomiting were noted. CONCLUSIONS: Desflurane and sevoflurane can be used to facilitate early emergence from anesthesia in neurosurgical pediatric patients. Emergence times are shorter with desflurane or sevoflurane than with isoflurane. The patients who received desflurane or sevoflurane have similar intraoperative and postoperative incidence of adverse effects compared with those who received isoflurane. Thus, desflurane and sevoflurane can be considered as suitable for emergence in pediatric neurosurgical anesthesia.

In vivo desflurane preconditioning evokes dynamic alterations of metabolic proteins in the heart--proteomic insights strengthen the link between bioenergetics and cardioprotection.

BACKGROUND: The cardioprotective effect of anaesthetic preconditioning as measured by reduction of ischaemia-reperfusion (I/R) injury is a well described phenomenon. However little is known about the impact on the myocardial proteome. We therefore investigated proteome dynamics at different experimental time points of a preconditioning protocol. METHODS: Using an in vivo rat model of desflurane-induced preconditioning (DES-PC) cardiac tissue proteomes were analysed by a gel-based comparative approach. Treatment-dependent protein alterations were assessed by intra-group comparisons. Proteins were identified by mass-spectrometry. RESULTS: A total of 40 protein spots were altered during the 30-minutes lasting preconditioning protocol. None of the proteins was differentially regulated consistently at all experimental time points. Interestingly, 1) the repeated administration of desflurane mostly accounted for proteome alterations during DES-PC, 2) the majority of altered protein species showed a decrease in abundance, 3) these changes primarily affected metabolic proteins involved in NADH/NAD(+) redox balance, calcium homeostasis and acidosis and 4) protein alterations were not exclusively due to expression changes but also represented modifications of specific protein isoforms. CONCLUSION: DES-PC evokes dynamic alterations in the cardiac proteome which substantiate a tight regulation of bioenergetic proteins. Unique protein modifications may play a more important role in the preconditioning response.

Analysis of the effect of perioperative magnesium sulphate on minimal alveolar concentration of desflurane using bispectral index monitoring.

BACKGROUND: In this study we aimed to analyze the effect of perioperative magnesium sulphate (MgSO(4)) on minimal alveolar concentration (MAC) of desflurane using bispectral index (BIS) monitoring. PATIENTS AND METHODS: Sixty patients undergoing abdominal surgery under general anesthesia were randomized into two groups: Mg - receiving perioperative MgSO(4) supplementation and C - control. Anesthesia was titrated to maintain the BIS value between 45-55. RESULTS: MAC values, tachycardia and hypertension during intubation was found to be lower in group Mg compared to group C (p<0.001). Time to extubation, verbal cooperation and eye opening was longer in patients receiving infusion of MgSO(4) (p<0.001). CONCLUSION: We concluded that perioperative MgSO(4) infusion may be used as an adjunct as it decreases MAC of desflurane and suppresses the hemodynamic response to intubation.

Global warming potential of inhaled anesthetics: application to clinical use.

BACKGROUND: Inhaled anesthetics are recognized greenhouse gases. Calculating their relative impact during common clinical usage will allow comparison to each other and to carbon dioxide emissions in general. METHODS: We determined infrared absorption cross-sections for sevoflurane and isoflurane. Twenty-year global warming potential (GWP(20)) values for desflurane, sevoflurane, and isoflurane were then calculated using the present and previously published infrared results, and best estimate atmospheric lifetimes were determined. The total quantity of each anesthetic used in 1 minimal alveolar concentration (MAC)-hour was then multiplied by the calculated GWP(20) for that anesthetic, and expressed as "carbon dioxide equivalent" (CDE(20)) in grams. Common fresh gas flows and carrier gases, both air/oxygen and nitrous oxide (N2O)/oxygen, were considered in the calculations to allow these examples to represent common clinical use of inhaled anesthetics. RESULTS: GWP(20) values for the inhaled anesthetics were: sevoflurane 349, isoflurane 1401, and desflurane 3714. CDE(20) values for 1 MAC-hour at 2 L fresh gas flow were: sevoflurane 6980 g, isoflurane 15,551 g, and desflurane 187,186 g. Comparison among these anesthetics produced a ratio of sevoflurane 1, isoflurane 2.2, and desflurane 26.8. When 60% N2O/40% oxygen replaced air/oxygen as a carrier gas combination, and inhaled anesthetic delivery was adjusted to deliver 1 MAC-hour of anesthetic, sevoflurane CDE(20) values were 5.9 times higher with N2O than when carried with air/O2, isoflurane values were 2.9 times higher, and desflurane values were 0.4 times lower. On a 100-year time horizon with 60% N2O, the sevoflurane CDE(100) values were 19 times higher than when carried in air/O2, isoflurane values were 9 times higher, and desflurane values were equal with and without N2O. CONCLUSIONS: Under comparable and common clinical conditions, desflurane has a greater potential impact on global warming than either isoflurane or sevoflurane. N2O alone produces a sizable greenhouse gas contribution relative to sevoflurane or isoflurane. Additionally, 60% N2O combined with potent inhaled anesthetics to deliver 1 MAC of anesthetic substantially increases the environmental impact of sevoflurane and isoflurane, and decreases that of desflurane. N2O is destructive to the ozone layer as well as possessing GWP; it continues to have impact over a longer timeframe, and may not be an environmentally sound tradeoff for desflurane. From our calculations, avoiding N2O and unnecessarily high fresh gas flow rates can reduce the environmental impact of inhaled anesthetics.

Functional comparison of anaesthetic agents during myocardial ischaemia-reperfusion using pressure-volume loops.

BACKGROUND: Left ventricular (LV) pressure-volume (PV) loops were used to compare the functional effects that accompany the cardioprotection seen with desflurane, sevoflurane, and propofol in a rabbit preparation of coronary ischaemia-reperfusion (IR). METHODS: Male New Zealand White rabbits (n=48) were anaesthetized with propofol (70 mg kg(-1) h(-1)), desflurane (8.9%), or sevoflurane (3.8%) and randomized to receive IR or non-ischaemic time-matched (TC) perfusion protocol. IR groups (desIR, propIR, and sevIR) underwent 30 min of left anterior descending coronary artery occlusion and then 120 min of reperfusion. TC groups (desTC, propTC, and sevTC) were anaesthetized for 150 min without ischaemia. Haemodynamic endpoints included mean arterial pressure, heart rate, cardiac index, systemic vascular resistance index, preload-recruitable stroke-work, time constant of relaxation (tau), and end-diastolic PV relationship (EDPVR). Ventricles in the IR groups were excised and stained with 2,3,5-triphenyl-tetrazolium chloride in order to measure infarct size. RESULTS: Myocardial infarction size was greater in the propIR group [35.74 (sd 11.32)%] compared with the desIR [13.44 (3.09)%] and sevIR [17.96 (6.63)%] groups (P<0.001). EDPVR deteriorated in the sevIR and propIR groups compared with their TC groups, sevTC (P=0.03) and propTC (P=0.044), respectively. There was no difference in any haemodynamic endpoints for the desIR group compared with its TC control (desTC). CONCLUSIONS: During ischaemia, all anaesthetics provide haemodynamic stability and preservation of LV contractility, whereas propofol and sevoflurane, but not desflurane, caused increased LV diastolic stiffness. Desflurane and sevoflurane provide superior cardioprotection compared with propofol.

Memory priming during light anaesthesia with desflurane and remifentanil anaesthesia.

BACKGROUND: Previous studies of memory priming during anaesthesia with EEG monitoring have observed implicit memory effects for words presented during light and deep anaesthesia with and without surgical stimulation. We hypothesized that memory priming occurs under each of five different combinations of anaesthesia and surgery, and no significant differences occur in memory priming among the five conditions or between the two test points such as, 12 vs 24 h after surgery. METHODS: Forty gynaecological patients (aged between 28 and 66 yr, median 44.5 yr) were included in the study. They received propofol and remifentanil induction followed by desflurane and remifentanil anaesthesia in conjunction with neuromuscular blocking agents. Each patient was exposed to 60 of 120 nouns in a double-blind randomized design. These 60 nouns were divided into 5 groups of 12 words, presented under one of the five different conditions, namely, intubation, skin incision, deep anaesthesia and moderate anaesthesia (both during surgery), and light anaesthesia during the emergence phase. The depth of anaesthesia was measured using the EEG monitor, Narcotrend. RESULTS: No explicit memories were observed in a free recall or in a yes-no recognition test. A word-stem completion test revealed a significant implicit priming only for light anaesthesia (P < 0.01). No significant differences were detected among the five conditions. An overall implicit memory effect occurred for the second test point (P < 0.05). CONCLUSIONS: Our hypotheses could not be verified. Implicit memory priming occurred only under light anaesthesia, when the patients were most probably conscious. Priming effects may be enhanced after night's sleep.

The role of antioxidant supplementation in occupational exposure to waste anaesthetic gases.

OBJECTIVES: Although the genotoxicity related to waste anaesthetic gases is controversial, a consistent number of observations have provided evidence for an increased level of DNA strand breaks. The goal of the research was to investigate this hypothesis and estimate the genoprotective role of antioxidant supplementation in technical anaesthesiology staff working in operating theatres. METHODS: Heparinized venous blood samples were collected from 17 exposed technical anaesthesiology staff (mean age 34.3 +/- 3.5 years) and non-exposed control group (mean age 32.2 +/- 3.4 years) and examined in the alkaline comet assay for DNA strand breakage. Vitamin E (300 mg/day) plus vitamin C (500 mg/day) were supplemented to the technical anaesthesiology staff for 12 weeks and blood samples were retaken and evaluated by comet assay. RESULTS: The DNA breakage observed in the lymphocytes of the technical anaesthesiology staff was 21.5 +/- 5.0, as calculated by total comet score (TCS). This score was significantly higher (P<0.001) than in the controls (8.6 +/- 4.7) before antioxidant treatment. Supplementation of vitamins E plus C significantly (P<0.01) reduced the mean TCS as 14.2 +/- 6.1. CONCLUSION: The results of our study indicate that occupational exposure to anaesthetic gases induces oxidative DNA damage. Supplementation of the diet for 12 weeks with vitamin C and vitamin E resulted in a significant decrease in the DNA damage.

The timing of acupuncture stimulation does not influence anesthetic requirement.

Studies suggest that acupuncture is more effective when induced before the induction of general anesthesia than afterwards. We tested the hypothesis that electro-acupuncture initiated 30 min before the induction reduces anesthetic requirement more than acupuncture initiated after the induction. Seven volunteers were each anesthetized with desflurane on 3 study days. Needles were inserted percutaneously at four acupuncture points thought to produce analgesia in the upper abdominal area and provide generalized sedative and analgesic effects: Zusanli (St36), Sanyinjiao (Sp6), Liangqiu (Sp34), and Hegu (LI4). Needles were stimulated at 2 Hz and 10 Hz, with frequencies alternating at 2-s intervals. On Preinduction day, electro-acupuncture was started 30 min before the induction of anesthesia and maintained throughout the study. On At-induction day, needles were positioned before the induction of anesthesia, but electro-acupuncture stimulation was not initiated until after the induction. On Control day, electrodes were positioned near the acupoints, but needles were not inserted. Noxious electrical stimulation was administered via 25-gauge needles on the upper abdomen (70 mA; 100 Hz; 10 s). The desflurane concentration was increased 0.5% when movement occurred and decreased 0.5% when it did not. These up-and-down sequences continued until volunteers crossed from movement to no movement four times. The P(50) of logistic regression identified desflurane requirement. Desflurane requirement was similar on the Control (mean +/- sd; 5.2% +/- 0.6%), Preinduction (5.0% +/- 0.8%), and At-induction (4.7% +/- 0.3%; P = 0.125) days. This type of acupuncture is thus unlikely to facilitate general anesthesia or decrease the requirement for anesthetic drugs.

The effect of auricular acupuncture on anaesthesia with desflurane.

In most acupuncture studies it is difficult or even impossible to conduct a truly double-blind trial. However, this is possible when treatments are carried out on anaesthetised patients. Because acupuncture provides analgesia, we tested the hypothesis that needle stimulation of a combination of four ear acupoints would significantly reduce anaesthetic requirement. Ten healthy volunteers were anaesthetised with desflurane and randomly assigned to no treatment or acupuncture; the alternative treatment was given on a subsequent study day. Auricular acupuncture was performed with needles placed at the Shen Men, Thalamus, Tranquiliser and Master Cerebral Points on the right ear. Anaesthetic requirement, determined by the Dixon up-and-down method, was defined by the average desflurane concentration that prevented purposeful movement of the extremities in response to noxious electrical stimulation. Volunteers required a greater desflurane concentration to prevent movement on the control than on the acupuncture day: 4.9 (0.7; SD) vs. 4.4 (0.8) vol. %, p = 0.003. Acupuncture thus reduced anaesthetic requirement by 8.5 (7)%.

Electro-acupuncture at the Zusanli, Yanglingquan, and Kunlun points does not reduce anesthetic requirement.

UNLABELLED: We tested the hypothesis that electro-acupuncture at the Zusanli, Yanglingquan, and Kunlun acupuncture points on the legs decreases anesthetic requirement. Fourteen young, healthy volunteers were anesthetized with desflurane on two separate days. Needle electrodes were positioned at the three acupuncture points thought to produce a generalized sedative and analgesic effect. Needles were percutaneously placed on treatment days; on control days, they were insulated and taped near the insertion points. The electrodes were stimulated on the treatment day. Stimulation consisted of 2-Hz and 100-Hz currents alternated at 2-s intervals. When the end-tidal desflurane concentration of 5.5% was stable for 15 min, noxious electrical stimuli were administered via 25-gauge needles on both thighs (70 mA at 100 Hz for 10 s). Desflurane concentration was increased 0.5% when movement occurred and decreased 0.5% when it did not. An investigator, blinded to treatment, determined movement. These up-and-down sequences were continued until volunteers crossed from movement to no movement four times. A logistic regression determined the partial pressure of desflurane that produced a 50% likelihood of movement in response to noxious stimulation and consequently identified the minimum alveolar anesthetic concentration equivalent for desflurane. There was no significant difference in minimum alveolar anesthetic concentration equivalents between the electro-acupuncture (4.6% +/- 0.6%, mean +/- SD) and control (4.6% +/- 0.8%) days (P = 0.8). These data provided an 80% power for detecting a difference of 0.35 volume-percent between the groups. IMPLICATIONS: Electro-stimulation of three general acupuncture points on the leg did not reduce desflurane requirements. This type of acupuncture is thus unlikely to facilitate general anesthesia or decrease the need for anesthetic drugs.

Transcutaneous electrical stimulation of an auricular acupuncture point decreases anesthetic requirement.

BACKGROUND: German anesthesiologists have long used transcutaneous electrical stimulation of an acupuncture point near the tragus to reduce anesthetic requirement in unblinded and uncontrolled trials. This is known as auricular electrically stimulated analgesia. The authors therefore tested the hypothesis that auricular electrically stimulated analgesia reduces anesthetic requirement. METHODS: In a randomized, double-blind, crossover trial, volunteers were anesthetized twice with desflurane. Electrical stimulation of an auricular acupuncture point in the vicinity of the tragus was used on 1 randomly assigned day, and no electrical stimulation of the same point was used on the other study day. Treatment consisted of bilateral electrical stimulation of the lateralization control point, 3 cm anterior to the tragus. The 10-mA current was set to 299 Hz on the dominant side of the face and to 149 Hz on the contralateral side. Anesthetic requirement was determined by the Dixon up-and-down method and was defined by the average desflurane concentration required to prevent purposeful movement of the extremities in response to noxious electrical stimulation. RESULTS: Ten men and 10 women completed the protocol. Electrical stimulation of the lateralization control point reduced anesthetic requirement by 11 +/- 7% (P < 0.001), with the reduction being similar in women and men. Women required more desflurane to prevent movement on the control day than the men (5.5 +/- 1.0 vs. 4.6 +/- 0.6 vol%; P = 0.028). CONCLUSION: This double-blinded trial with an objective outcome demonstrates that electrical stimulation of the lateralization control point significantly reduces anesthetic requirement.

Análise bispectral do tempo de despertar e avaliaçäo da recuperaçäo da psicomotricidade e da consciência em anestesias com desflurano ou sevoflurano / Bispectral analysis of time to emergence and evaluation of psychomotricity and consciousness recovery in anesthesia with desflurance or sevoflurane

Justificariva e objetivos: desflurano e sevoflurano säo utilizados para cirurgias ambulatoriais. O objetivo deste estudo é avaliar a recuperaçäo da cogniçäo, da psicomotricidade e o tempo de alta hospitalar em pacientes anestesiados com desflurano ou sevoflurano. Método: participaram do estudo 30 pacientes do sexo feminino, estado físico ASA I, idades entre 21 e 41 anos, submetidas a mamoplastia estética, alocadas aleatoriamente em dois grupos: no grupo I(n=15), a induçäo foi realizada por via venosa com alfentanil (30µg.kg(elevado a menos 1) e propofol titulado conforme BIS e a anestesia mantida com desflurano associado ao óxido nitroso a 60 por cento em oxigênio; No grupo II(n=15), foi empregada a mesma técnica com sevoflurano. Todas as pacientes foram monitoradas através do teste de Trieger; funçäo cognitiva através do teste de substituiçäo de dígitos; tempo de despertar e teste de da tripla orientaçäo, assim como o tempo para alta hospitalar. Resultados: no tempo de despertar houve diferença significativa (G1=8,13ñ0,37 minutos e GII=11.21ñ0,97 minutos) (p<0,05). No teste da tripla orientaçäo o G I=10,26ñ0,79 minutos e G II=13,4ñ0,82 minutos (p<0,05). Em relaçäo ao teste de Triger, o número de erro no G I foi menor que no G II até 30 minutos pós-extubaçäo (p<0,05). Em relaçäo a alta hospitalar näo houve diferença significativa na comparaçäo dos tempos (G I e G II) (p>0,05). Conclusöes: apesar de apresentar despertar da anestesia e recuperaçäo das funçöes cognitivas e psicomotricidade em tempo mais prolongado, o sevoflurano pode ser empregado, já que as diferenças näo têm importância clínica. Além disso, näo houve diferença significativa nos tempos de alta hospitalar, mostrando que o sevoflurano é uma excelente alternativa ao desflurano em pacientes ambulatoriais, mesmo em operaçöes prolongadas

The effect of midazolam premedication on mental and psychomotor recovery in geriatric patients undergoing brief surgical procedures.

UNLABELLED: To assess the effect of IV midazolam premedication on recovery of cognitive function, 90 geriatric patients (aged 65-81 yr) undergoing brief transurethral procedures were enrolled into this prospective, placebo-controlled, double-blinded study. In all cases, a standard general anesthetic was administered. Thirty minutes before operating room transfer, patients in Group 0.5 mg, Group 2 mg, and Group S received 0.5 mg of midazolam, 2 mg of midazolam, or an equal volume of saline, respectively. Before study-drug administration (baseline), at 15 min thereafter, as well as on arrival in the postanesthesia care unit (PACU), and at 60 min and 120 min, postoperatively, we administered a digit-symbol substitution test, a mini-mental test, a shape-sorter test, and a patient-generated 100-mm visual analog score (0 = minimal and 100 = maximal) for anxiety, sleepiness, and coordination. A 4-point scale was used to assess the degree of patient sedation at 7, 15, and 30 min after study-drug administration. Using a modified Aldrete scoring system, PACU discharge was determined by the PACU staff. Patient anxiety, sleepiness, and coordination scores at baseline and at 15 min after study-drug administration were similar. When compared with saline, midazolam was associated with a significantly (P < 0.05) higher incidence of "deep" sedation. In Group 2 mg, the incidence of a low preoperative Spo2 (<94%) was significantly (P < 0.05) higher when compared with Group S. Emergence, extubation, and orientation times, as well as time to follow commands were unaffected by midazolam premedication. Postoperatively, the digit-symbol substitution test, mini-mental test, and shape-sorter test were similar among the groups. However, time to PACU discharge was significantly (P = 0.03) longer in the two midazolam treatment groups (41 +/-25 min, 60 +/- 32 min, 53 +/- 39 min for Groups S, 0.5 mg, and 2 mg, respectively). Finally, patient satisfaction was unaffected by the randomization schedule. IMPLICATIONS: IV premedicant midazolam 0.5 mg or 2 mg does not adversely affect mental and psychomotor recovery in geriatric patients undergoing brief surgical procedures. However, midazolam administration significantly prolonged postanesthesia care unit discharge time. Finally, during the preoperative period, midazolam increases the incidence of a Spo2 <94% in a dose-dependent manner.

[Occupational exposure in the hospital to laughing gas and the new inhalation anesthetics desflurane and sevoflurane]. / Arbeitsplatzbelastung im Krankenhaus mit Lachgas und den neuen Inhalationsanästhetika Desfluran und Sevofluran.

BACKGROUND AND OBJECTIVE: There have been few studies of the occupational exposure of the new volatile anaesthetic agents desflurane and sevoflurane. Because a health risk through long-term exposure to these inhalants cannot as yet be definitely excluded, we undertook to measure the concentrations of these three anaesthetics in different parts of the Frankfurt University Medical Centre. Considering the results the relevance of exposure for surgical and anaesthesia personnel, possible consequences due to laws and possibilities of improvement were shown. METHODS: The concentration of the three anaesthetics was measured during and after 345 procedures under general anaesthesia, using photoacoustic infra-red-spectrometry every 90 sec in the breathing zone of the same operating room personnel or in the recovery room and the intensive care unit. RESULTS: Exposure of personnel in the air-conditioned operating rooms was very low, but in those rooms that were not or inadequately air conditioned was a times very high. The level of the concentrations was also significantly related to the anaesthesia system and the distance of the exposed person to the patient. The concentration of nitrous oxide was below the maximal working-place concentration (MWC) of 100 ppm, but it exceeded the threshold concentration of 0.1 MAC, as laid down in the "Maternal Protection Law" in the surgical intensive care unit and the recovery room. There are no limiting concentrations for desflurane and sevoflurane yet but their concentrations were clearly below the MWC laid down for isoflurane and enflurane. CONCLUSION: In principle the use of inhalation anaesthetics can be considered to be without occupational health risk under the present legally defined standards of air-conditioning and the requirements of a modern occupational protection law. Because of the increased concentrations in the recovery room and intensive care unit pregnant and breast-feeding women should not work in these areas.

Desflurane, enflurane, isoflurane and ether produce ethanol-like discriminative stimulus effects in mice.

In the present studies, drug discrimination procedures were used to compare the discriminative stimulus effects of ethanol (ETOH) and several volatile anesthetics. Male albino mice were trained to discriminate between IP injections of ETOH (1.25 g/kg) and saline in a two-lever operant task in which responding was under the control of a fixed-ratio 20 (FR20) schedule of food presentation. Stimulus generalization was examined after 20-min inhalation exposures to desflurane (4,000-32,000 ppm), enflurane (3,000-12,000 ppm), isoflurane (1,000-8,000 ppm) and ether (4,000-32,000 ppm). Concentration-related increases in ETOH-lever responding were observed for all four volatile anesthetics. For enflurane and ether, maximal levels of > 85% ETOH-lever responding were obtained at one or more concentrations. For desflurane and isoflurane, the maximal mean percentages of ETOH-lever responding were somewhat lower, but 6 out of 7 mice showed full substitution with desflurane and 5 out of 7 for isoflurane. The shared discriminative properties of these compounds with ETOH suggest that these anesthetics may share some of ETOH's pharmacological properties. These results are similar to previous research results showing ETOH-like discriminative stimulus effects in mice with other anesthetics and abused volatile inhalants (i.e. halothane, toluene and 1.1,1-trichloroethane) and may reflect the CNS-depressant drug-like effects of inhaled anesthetics and abused solvents.

Effect of nebulized lignocaine on airway irritation and haemodynamic changes during induction of anaesthesia with desflurane.

This study was designed to assess the effect of nebulized lignocaine or saline given before induction on the quality of induction of anaesthesia with desflurane in unpremedicated, young, adult males. Of the first six patients, five developed laryngospasm, breath-holding, coughing and increased secretions. In four patients oxygen saturation decreased to 92% or less. Significant tachycardia and hypertension occurred in four patients, and bradyarrhythmia after induction occurred in three patients. Hiccups and bronchospasm occurred in one patient. Because of the unacceptably high incidence of complications, the study was discontinued. The incidence and severity of complications were not decreased by administration of nebulized lignocaine and were higher than those reported by other workers. We conclude that in unpremedicated, young, adult males, induction of anaesthesia with desflurane and nitrous oxide in oxygen was associated with a high incidence of respiratory irritant effects, tachycardia, hypertension and post-induction bradyarrhythmia. We also found that lignocaine, as used in this study, did not appear to obtund the cardiovascular and respiratory complications during inhalation induction using desflurane.

Polyhalogenated and perfluorinated compounds that disobey the Meyer-Overton hypothesis.

Fourteen polyhalogenated, completely halogenated (perhalogenated), or perfluorinated compounds were examined for their anesthetic effects in rats. Anesthetic potency or minimum alveolar anesthetic concentration (MAC) was quantified using response/nonresponse to electrical stimulation of the tail as the end-point. For compounds that produced excitable behavior, and/or did not produce anesthesia when given alone, we determined MAC by additivity studies with desflurane. Nine of 14 compounds had measurable MAC values with products of MAC x oil/gas partition coefficient ranging from 3.7 to 24.8 atm. Because these products exceed that for conventional inhaled anesthetics (1.8 atm), they demonstrate a deviation from the Meyer-Overton hypothesis. Five compounds (CF3CCIFCF3, CF3CCIFCCIFCF3, perfluorocyclobutane, 1,2-dichloroperfluorocyclobutane, and 1,2-dimethylperfluorocyclobutane) had no anesthetic effect when given alone, had excitatory effects when given alone, and tended to increase the MAC for desflurane. These five compounds had no anesthetic properties in spite of their abilities to dissolve in lipids and tissues, to penetrate into the central nervous system, and to be administered at high enough partial pressures so that they should have an anesthetic effect as predicted by the Meyer-Overton hypothesis. Such compounds will be useful in identifying and differentiating anesthetic sites and mechanisms of action. Any physiologic or biophysical/biochemical change produced by conventional anesthetics and deemed important for the anesthetic state should not be produced by nonanesthetics.