A novel and simple method for endotracheal intubation of mice

Endotracheal intubation in mice is necessary for experiments involving intratracheal instillation of various substances, repeated pulmonary function assessments and mechanical ventilation. Previously described methods for endotracheal intubation in mice require the use of injection anaesthesia to immobilize the animal during the intubation procedure or the use of a volatile anaesthetic prior to intubation for immobilization. With these methods, the control of anaesthetic depth during the intubation procedure is absent. We describe a method for simple and rapid intratracheal intubation in mice for mechanical ventilation, using a self-built plastic support to facilitate the intubation procedure. General anaesthesia is maintained by means of inhalation through a non-rebreathing circuit connected to the plastic support. This set-up gives the operator control of anaesthetic depth and sufficient time to perform the intubation procedure. A purpose-made laryngoscopic blade is used to facilitate the intubation tube entering the trachea. The blade of the purpose-made laryngoscope is constructed as a retraction guide and is curved for easy handling. Under direct vision, the epiglottis is gently lifted by the laryngoscopic blade while the intubation tube is pushed into the trachea. Following this novel intubation technique, we were able to mechanically ventilate mice for at least 2 h without severely disturbing blood gases. Histological evaluation of the lungs and microscopic evaluation of the trachea and larynx showed no signs of trauma related to the intubation technique or mechanical ventilation.     

Modulation of the Benzodiazepine/γ-Aminobutyric Acid Receptor Chloride Channel Complex by Inhalation Anesthetics

Inhalation anesthetics, such as diethyl ether, halothane, and enflurane, increase 36Cl- uptake into rat cerebral cortical synaptoneurosomes in a concentration-dependent, picrotoxin-sensitive fashion. At concentrations consistent with those that stimulate 36Cl- uptake, inhalation anesthetics also inhibit the binding of t-[35S]butylbicyclophosphorothionate ([35S]TBPS) to well-washed cortical membranes. Scatchard analysis of [35S]TBPS binding indicates that these agents reduce the apparent affinity of this radioligand and have little effect on the Bmax. The ability of inhalation anesthetics to directly stimulate 36Cl- uptake and inhibit [35S]TBPS binding is a property shared by nonvolatile anesthetics. Nonetheless, there are differences between nonvolatile agents (such as barbiturates and alcohols) and inhalation anesthetics, because the former compounds augment muscimol (a GABAmimetic) stimulated 36Cl- uptake, whereas the latter group (such as ether and enflurane) inhibit this effect. These findings demonstrate that therapeutically relevant concentrations of inhalation anesthetics perturb the benzodiazepine/gamma-aminobutyric acid receptor chloride channel complex, and suggest this oligomeric protein may be a common mediator of some aspects of anesthetic action.     

可视喉镜气管插管对心跳骤停抢救患者血流动力学及心肺复苏质量的影响

摘要 目的：探讨可视喉镜气管插管对心跳骤停抢救患者血流动力学及心肺复苏质量的影响。方法：选取联勤保障部队第九四〇医院于2020年4月~2022年5月期间收治的98例心跳骤停抢救患者为研究对象,根据插管方式将患者分为B组（可视喉镜气管插管,n=50）、A组（传统直接喉镜气管插管,n=48）。对比两组插管次数、声门暴露时间、插管时间、气道与牙齿损伤、心肺复苏质量及血流动力学指标变化情况,观察两组不良反应发生情况。结果：B组的插管次数少于A组,声门暴露时间、插管时间短于A组,气道与牙齿损伤比例少于A组（P<0.05）。B组的插管成功率、心肺复苏（CPR）成功率、存活率均高于A组（P<0.05）。B组插管后15 min的收缩压（SBP）、舒张压（DBP）、平均动脉压（MAP）及心率（HR）均低于A组同期（P<0.05）。B组的不良反应发生率低于A组（P<0.05）。结论：相比于传统直接喉镜气管插管用于心跳骤停抢救患者,可视喉镜气管插管可维持血流动力学稳定,提高插管成功率和心肺复苏质量,安全性较好。     

Simultaneous determination of fluorinated inhalation anesthetics in blood by gas chromatography–mass spectrometry combined with a headspace autosampler

Although the fluorinated inhalation anesthetics, including desflurane, sevoflurane, isoflurane, enflurane, and halothane are commonly used, fatal cases resulting from their abuse or misuse have been reported. To date, gas chromatography (GC) equipped with different kinds of detectors has been utilized to analyze inhalation anesthetics. However, none of them can detect desflurane reliably or analyze all five common anesthetics simultaneously. The purpose of the present work is to further modify the previously developed headspace (HS) GC–MS method for blood isoflurane determination to analyze and distinguish five common clinical inhalation anesthetics, simultaneously. The modified HS-GC–MS method adopts a 60 m×0.25 mm I.D., 0.25 μm film thickness DB-5 capillary column along with an adequate GC temperature program, which gives the five inhalation anesthetics, including isoflurane and its isomer, enflurane, a high resolution. The method also takes both the volatility and the influence of the top space on the obtained concentration into consideration and therefore keeps the sample loss acceptable even for analyzing the highly volatile desflurane. Within a certain concentration range of the calibration standard (about 20–300 μg/ml), this method shows a good linearity with correlation coefficients greater than 0.999. In addition, both within- and between-run precision and accuracy results meet the validation requirements as well as the tested results of practical blood samples of desflurane. In summary, this is a reliable analytical method to simultaneously determine the concentration of five common inhalation anesthetics in blood. Such a method is very practical for both clinical and occupational monitoring, as well as for analytical toxicology.     

模式生物秀丽线虫与吸入麻醉药敏感性相关的基因

吸入麻醉药虽已在临床上广泛应用,然其分子作用机制和作用位点仍然不清楚。以秀丽线虫为模式生物在研究麻醉药的分子机制上有着众多优点,近年亦取得了一定的进展。以秀丽线虫作为模式生物时麻醉终点的选择主要有两种：使用大于临床浓度的吸入麻醉药,使秀丽线虫停止运动作为麻醉终点和使用接近临床浓度的吸入麻醉药,使秀丽线虫行动变得不协调和迟缓作为麻醉终点。这两种研究方法已经发现一些与吸入麻醉药敏感性相关的基因,如unc-79,unc-80,unc-9,unc-1,gas-1和unc-64等基因。这些基因主要表达于神经元,与神经突触、线粒体的功能有关。     

Isoflurane induces second window of preconditioning through upregulation of inducible nitric oxide synthase in rat heart

The second window of preconditioning (SWOP) induced by inhalation of volatile anesthetics has been documented in the rat heart and is triggered by nitric oxide synthase (NOS), but involvement of NOS in the mediator phase of isoflurane-induced SWOP has not been demonstrated. We tested the hypothesis that isoflurane-induced SWOP is mediated through upregulation of inducible NOS (iNOS). Rats inhaled 0.75 minimum alveolar concentration (MAC) isoflurane, 1.5 MAC isoflurane, or O2 for 2 h. After 24, 48, 72, and 96 h, the isolated heart was perfused with buffer and subjected to 30 min of ischemia followed by 2 h of reperfusion. Inhalation of 0.75 and 1.5 MAC isoflurane significantly limited infarct size after ischemia-reperfusion 24-72 h after isoflurane inhalation. The maximum effect was obtained 48 h after inhalation of 1.5 MAC isoflurane. Postischemic left ventricular function was improved only 48 h after inhalation of 1.5 MAC isoflurane. iNOS expression and activity in the heart were increased 24-72 h after inhalation of 1.5 MAC isoflurane; this increase was less pronounced after inhalation of 0.75 MAC isoflurane. A selective iNOS inhibitor, 1400W (10 microM), abolished iNOS activation and cardioprotection induced 48 h after inhalation of 1.5 MAC isoflurane. These results suggest that isoflurane inhalation induces SWOP after 24-72 h through overexpression and activation of iNOS in the rat heart.     

Simplification of rat intubation on inclined metal plate

Small-animal intubation is often necessary during inhalation anesthesia to allow steady-state conditions for large operations and in vivo experiments in all fields of experimental surgery. In rats, placing an orotracheal tube is technically difficult primarily because of the small size of the subject and the lack of equipment specifically designed for this task. We describe a simple rat intubation technique in which the animal is suspended in dorsal recumbency on an inclined metal plate. The animal, anesthetized with ether, is fixed to a 70 degrees-inclined metal plate in a dorsal position by means of a Mersilene ribbon hooked around the upper incisors. This method of positioning the animal is the most important step in the intubation process and further facilitates the technique already described by other authors. A human otoscope was used as a laryngoscope, intubation was performed using the Seldinger technique, and a 14-gauge intravenous catheter served as an endotracheal tube. This inexpensive technique is quickly learned and can be used in any laboratory. Safe and reliable airway management can thus be achieved, permitting in vivo examinations and operations.     

吸入性麻醉药动力学模型定量分析

从机理分析的角度研究了吸入性麻醉药使用过程中在诱导期的数学模型,采用室分析方法,建立了人体血药浓度的药代动力学模型和吸入药量模型,并求出其精确解．然后以七氟谜用药累积记录为研究对象,进行了数值计算,算得药代动力学模型和吸入药量模型与实际测量数据的相关系数分别为0．9865和0．8874．最后给出模型拟合曲线．     

Do inhalation general anesthetic drugs induce the neuronal release of endogenous opioid peptides?

The antagonism of some effects of inhalation general anesthetic agents by naloxone suggests that there may be an opioid component to anesthetic action. There is evidence that this opioid action component is due to neuronal release of endogenous opioid peptides. The strongest evidence is provided by studies that monitor changes in the concentration of opioid peptides in the perfused brain following inhalation of the anesthetic. Indirect or circumstantial evidence also comes from studies of anesthetic effects on regional brain levels of opioid peptides, antagonism of selected anesthetic effects by antisera to opioid peptides and anesthetic-induced changes radioligand binding to opioid receptors. It is likely that some inhalation general anesthetics (e.g., nitrous oxide) can induce neuronal release of opioid peptides and that this may contribute to certain components of general anesthesia (e.g., analgesia). More definitive studies utilizing in vivo microdialysis or autoradiography in selected areas of the brain during induction and successive states of general anesthesia have yet to be conducted.     

Induction and persistence of micronuclei, sister-chromatid exchanges and chromosomal aberrations in splenocytes and bone-marrow cells of rats exposed to ethylene oxide

Studies on the induction and persistence of ethylene oxide (EO) induced chromosomal alterations in rat bone-marrow cells and splenocytes following in vivo exposure were carried out. Rats were exposed to ethylene oxide either chronically by inhalation (50-200ppm, 4 weeks, 5 days/week, 6h/day) or acutely by intraperitoneal injection (i.p.) at dose levels of 50-100ppm.Spontaneous- and induced-frequencies of micronuclei (MN), sister-chromatid exchanges (SCEs) and chromosomal aberrations were determined in rat bone-marrow cells, and in splenocytes following in vitro mitogen stimulation. Unstable chromosomal aberrations were studied in whole genome using standard Giemsa staining technique and fluorescence in situ hybridisation using probe for chromosome #2 was employed to detect chromosome translocations.Following chronic exposure, the cytogenetic analyses were carried out at days 5 and 21 in rat splenocytes, to study the induction and persistence of sister-chromatid exchanges. Following chronic exposure, ethylene oxide was effective in inducing SCEs, and markedly cells with high frequency SCEs were observed and they in-part persisted until day 21 post-exposure. However, no significant effect was observed in rat splenocytes for induction of MN and chromosomal aberrations. Following acute exposure, both SCEs and MN were increased significantly in rat bone-marrow cells as well as splenocytes.In conclusion, this study indicates that ethylene oxide at the concentrations employed by intraperitoneal injection or inhalation in adult rats is mutagenic and can induce both SCEs and MN.     

Interfacial preference of anesthetic action upon the phase transition of phospholipid bilayers and partition equilibrium of inhalation anesthetics between membrane and deuterium oxide

The half-height linewidth (v 1/2) of the 1H-NMR spectra of dipalmitoylphosphatidylcholine vesicles changes abruptly at the phase transition temperature. In the absence of inhalation anesthetics, proton signals from the choline head group (hydrophilic interface) and acyl-chain tails (lipid core) change at the same temperature of 39.6 degrees C. The present study compared the effect of four inhalation anesthetics, i.e., methoxyflurane, chloroform, halothane and enflurane, upon the ligand-induced phase transition of phosphatidylcholine vesicle membranes at 37 degrees C. The anesthetics showed differential action upon the phase transition of the phospholipid vesicle membranes between the lipid core and the hydrophilic interface. The concentrations of anesthetics which induced the phase transition of the lipid core were about 2-fold greater than those required for the phase transition of the interfacial choline head groups. From the area under the proton signals of inhalation anesthetics in the NMR spectra, the maximum solubilities of methoxyflurane, chloroform and halothane in 2H2O at 37 degrees C were determined to be 0.671 . 10(-4), 2.637 . 10(-4) and 1.398 . 10(-4) (expressed as mole fractions), or 3.35, 13.17 and 6.98 mmol/1000 g 2H2O, respectively. The solubilities of the anesthetic vapor in 2H2O expressed as mole fractions according to Henry's law ere 9.586 . 10(-4), 6.432 . 10(-4) and 2.311 10(-4)/atm (1.013 . 10(5) Pa) partial pressure, respectively. The presence of phospholipid vesicles in 2H2O increased the solubility of the inhalation anesthetics. From difference between solubility in 2H2O and a dipalmitoylphosphatidylcholine vesicle suspension, the partition coefficients of methoxyflurane, chloroform and halothane between the phospholipid vesicle membranes and 2H2O were estimated. These values, calculated from the mole fractions, were 3364, 1660 and 3850, respectively at 37 degrees C.     

The imidazobenzodiazepine Ro 15-4513 antagonizes methoxyflurane anesthesia

Parenteral administration of the imidazobenzodiazepine Ro 15-4513 (a high affinity ligand of the benzodiazepine receptor with partial inverse agonist qualities) produced a dose dependent reduction in sleep time of mice exposed to the inhalation anesthetic, methoxyflurane. The reductions in methoxyflurane sleep time ranged from approximately 20% at 4 mg/kg to approximately 38% at 32 mg/kg of Ro 15-4513. Co-administration of the benzodiazepine receptor antagonist Ro 15-1788 (16 mg/kg) or the inverse agonists DMCM (5-20 mg/kg) and FG 7142 (22.5 mg/kg) blocks this effect which suggests that the reductions in methoxyflurane sleep time produced by Ro 15-4513 are mediated via occupation of benzodiazepine receptors. Moreover, neither DMCM (5-20 mg/kg) nor FG 7142 (22.5 mg/kg) reduced methoxyflurane sleep time which suggests this effect of Ro 15-4513 cannot be attributed solely to its partial inverse agonist properties. These observations support recent findings that inhalation anesthetics may produce their depressant effects via perturbation of the benzodiazepine/GABA receptor chloride channel complex, and suggest that Ro 15-4513 may serve as a prototype of agents capable of antagonizing the depressant effects of inhalation anesthetics such as methoxyflurane.     

两种用于小型猪胰肾联合移植实验麻醉方法的比较

目的比较静脉复合吸入全麻和静脉全麻两种方法用于小型猪胰肾联合移植实验中的麻醉效果,探讨简单、安全、易行的麻醉方法。方法A、B两组健康贵州小香猪,每组6只,基础麻醉后气管插管,A组：持续吸入异氟醚维持麻醉,根据手术要求间断注入万可松和芬太尼;B组：持续注入氯胺酮,间断静脉注射万可松和芬太尼维持麻醉。观察麻醉持续时间,镇痛和肌松药量,术后拔管和完全清醒时间,监测麻醉过程中血压、心率、脉搏氧的变化。结果A组术中麻醉效果好,血压、心率和脉搏氧稳定,与B组有显著差异（P〈0.05）;B组麻醉效果较差,肌松用药量明显增多,术后完全清醒时间长于A组（P〈0.05）。结论气管插管后静吸复合的麻醉方法是用于贵州小型猪实验安全、合适的麻醉方法。     

The fluorinated anesthetic halothane as a potential NMR biologic probe

Fluorinated anesthetics such as halothane preferentially partition into hydrophobic environments such as cell membranes. The 19F-NMR spectrum of halothane in a rat adenocarcinoma (with known altered lipid metabolism and membrane composition) shows an altered chemical shift pattern compared to the anesthetic in normal tissue. In eight tumor samples examined, the 19F-NMR spectra exhibit two distinct resonances, compared to a single resonance observed in normal tissues. This is explained by an enhanced or altered hydrophobic component in the tumor tissue giving rise to two discrete halothane environments. Another fluorinated anesthetic, isoflurane, shows similar behavior in distinguishing normal from diseased tissue. Given the large chemical shift range of fluorine and the inherent sensitivity of this nucleus, 19F-NMR spectra of fluorinated anesthetics can also be used to follow anesthetic degradation by the liver. The ability of fluorinated anesthetics to discriminate tissues and to monitor metabolic processes is potentially useful for in vivo 19F-NMR surface coil and imaging studies.     

Effects of general anesthetics on search in memory in man.

Recovery of search functions in long-term memory following several hours of anesthesia was studied on human volunteers. Verbal as well as visual search was assessed. The anesthetics used, fluroxene and halothane, slowed down considerably the verbal search for the first few hours following anesthesia, but had very little effect on the following day. No effect was observed a week later. Visual search was not affected at all, in accordance with previous findings indicating a selective effect of low concentrations of inhalation anesthetics on verbal memory.     

The effect of two inhalation anesthetics of the order of spin-labeled phospholipid vesicles

The order parameter (S′_n) of spin-labeled phosphatidylcholine vesicles has been shown to decrease in a concentration-dependent manner with two inhalation anesthetics, halothane and methoxyfluorane. Similar decreases ofS′_n are observed in vesicles labeled adjacent to the polar head group and those labeled near the bilayer center. This suggests that inhalation anesthetics cause a generalized fluidization of the membrane rather than a disorder localized in a particular region of the bilayer. Measurements of the isotropic nitrogen hyperfine coupling constant (a′_N) show a decrease in polarity of the environment with increasing anesthetic concentrations. The experimental approach of plottingS′_n versus anesthetic concentration provides a test of whether anesthetics produce their effects on a per molecule or per volume basis.     

The fluorinated anesthetic halothane as a potential NMR biologic probe

Fluorinated anesthetics such as halothane preferentially partition into hydrophobic environments such as cell membranes. The ¹⁹F-NMR spectrum of halothane in a rat adenocarcinoma (with known altered lipid metabolism and membrane composition) shows an altered chemical shift pattern compared to the anesthetic in normal tissue. In eight tumor samples examined, the ¹⁹F-NMR spectra exhibit two distinct resonances, compared to a single resonance observed in normal tissues. This is explained by an enhanced or altered hydrophobic component in the tumor tissue giving rise to two discrete halothane environments. Another fluorinated anesthetic, isoflurane, shows similar behavior in distinguishing normal from diseased tissue. Given the large chemical shift range of fluorine and the inherent sensitivity of this nucleus, ¹⁹F-NMR spectra of fluorinated anesthetics can also be used to follow anesthetic degradation by the liver. The ability of fluorinated anesthetics to discriminate tissues and to monitor metabolic processes is potentially useful for in vivo ¹⁹F-NMR surface coil and imaging studies.     

DNA damage in patients who underwent minimally invasive surgery under inhalation or intravenous anesthesia

Recent studies have demonstrated the genotoxicity of anesthetics in patients who have undergone surgery and in personnel who are occupationally exposed to anesthetics. However, these findings are controversial. Herein, we used the comet assay (single-cell gel electrophoresis) to investigate the genotoxic effects of two volatile compounds [isoflurane (ISF) and sevoflurane (SVF)] that are used in inhalation anesthesia, and of one intravenous (iv) anesthetic compound [propofol (PF)]. The groups consisted of 45 patients who underwent minimally invasive surgery that lasted at least 2h. Patients were classified as physical status I using the criteria of the American Society of Anesthesiologists (ASA) and were randomly allocated to receive ISF, SVF or PF anesthesia. Venous blood samples were collected at three time points as follows: before the premedication and the induction of anesthesia (T(0)); 2h after the beginning of anesthesia (T(1)); and on the day following surgery (T(2)). DNA damage (strand breaks and alkali-labile sites) was evaluated in peripheral blood lymphocytes. For each patient, one hundred nucleoids were analyzed per time point using a semi-automated image system. Patients did not differ with respect to their demographic characteristics, the duration of surgery, or the total doses of intraoperative drugs. The amount of DNA damage was not different among the three groups before anesthesia (T(0)). No statistically significant (p>0.05) increase in DNA damage was detected during (T(1)) or after anesthesia (T(2)) using three different protocols (ISF, SVF or PF). In conclusion, general anesthesia with inhaled ISF and SVF or iv PF did not induce DNA strand breaks or alkali-labile sites in peripheral lymphocytes. Therefore, our results show that the genotoxic risk of these anesthetics, for healthy patients undergoing minimally invasive otorhinological surgery, is low or even absent.     

Effect of caffeine-coconut products interactions on induction of microsomal drug-metabolizing enzymes in Wistar Albino rats.

Effect of caffeine-coconut products interactions on induction of drug-metabolizing enzyme in wistar albino rats was studied. Twenty rats were randomly divided into four groups: The control group (1) received via oral route a placebo (4.0ml of distilled water). Groups 2 to 4 were treated for a 14-day period with 50 mg/kg body weight of caffeine, 50 mg/kg body weight of caffeine and 50 mg/kg body weight of coconut water, and 50 mg/kg body weight of caffeine and 50 mg/kg body weight of coconut milk in 4.0ml of the vehicle via gastric intubation respectively. One day after the final exposure, the animals were anaestheticized by inhalation of an overdose of chloroform. The blood of each rat was collected by cardiac puncture while the liver of each rat was harvested and processed to examine several biochemical parameters, i.e., total protein and RNA levels, protein/RNA ratios, and activities of alanine and aspartate amino transferase (ALT and AST, respectively). The results showed that while ingestion of coconut milk and coconut water increased the values of protein and protein/RNA ratios, it decreased alanine and aspartate amino transferase (ALT and AST) activities. These effects, in turn, enhanced the induction of the metabolizing enzymes and a resultant faster clearance and elimination of the caffeine from the body, there by reducing the toxic effect on the liver.     

低体质量小儿心脏手术中应用七氟醚全身麻醉诱导的效果及其对血流动力学的影响

目的:探讨低体质量小儿心脏手术中应用七氟醚全身麻醉诱导的效果及其对血流动力学的影响。方法:选择本院2016年7月-2018年2月期间收治的28例低体质量小儿心脏手术患儿纳入本研究,按照随机数字表法将患儿分为对照组和观察组各14例。对照组采用氯胺酮进行全身麻醉诱导,观察组采用七氟醚吸入麻醉进行全身麻醉诱导。观察两组患儿麻醉诱导敏感性及不良反应等情况,比较两组患儿诱导前、诱导过程中、插管即刻的收缩压(SBP)、舒张压(DBP)、心率(HR)及血氧饱和度(SaO2)水平。结果:观察组患儿哭闹时间、睫毛反射消失时间及疼痛反射消失时间显著低于对照组(P0.05)。观察组患儿不良反应发生率为7.14%(1/14),与对照组的28.57%(4/14)比较差异无统计学意义(P0.05)。诱导过程中及插管即刻,对照组患儿SBP、DBP均低于诱导前和观察组,HR高于诱导前和观察组,SaO_2先降低后升高,且低于观察组(P0.05),观察组患儿SBP低于诱导前,SaO2高于诱导前(P0.05),而DBP、HR与诱导前比较无统计学差异(P0.05)。结论:与氯胺酮相比,采用七氟醚吸入全身诱导麻醉,其对低体质量小儿心脏手术患儿的循环干扰较小,同时在诱导过程中安全稳定,对血流动力学影响较小,容易被患儿所接受。