多孔介质对麻醉蒸发器传热传质效果影响的计算分析

目的:研究某型部分填充多孔介质麻醉蒸发器工作原理,并对其结构进行实际测量。利用Darcy扩展方程和N-S方程及能量和组分传递方程分别对多孔介质区域和纯流体区域建立数学模型,分析不同孔隙率下的平均传热传质速率随渗透率的变化。方法:文中采用运用CFD方法分析了多孔介质材料对麻醉蒸发器蒸发效果的影响,并且论述了在蒸发器多孔介质区域内麻醉药液与载气相遇、混合、蒸发过程的变化状况。假定麻醉药物蒸发雾滴与稀释气体存在热交换和动量的相互作用,忽略重力和剪切力在雾滴运动过程当中对其的影响效果,利用湍流随机跟踪模型追踪了在多孔介质区域中的气液两相流离散项麻醉药物蒸发雾滴的运动状况。结果:通过计算得到了不同状态下蒸发器多孔介质区域内气体速度场、密度、麻醉药物质量分数、药物浓度、比热变化,药物浓度场在与稀释气体混合过程中的变化以及麻醉药物挥发等结果。结论:数值模拟结果表明多孔介质特性、渗透率、孔隙率对麻醉蒸发器腔体内传热传质存在不可忽略的影响。     

麻醉蒸发器内部流动与混合过程的三维数值计算分析

研究了某型麻醉蒸发器工作原理,并对其结构进行实际测量。运用CFD方法对蒸发器内部气体流动与混合过程进行了三维数值模拟分析,并采用湍流随机跟踪方法,对麻醉药物蒸发雾滴的运动进行轨迹追踪,得到了蒸发器内部气体速度场变化,麻醉药物挥发以及与稀释气体混合过程中浓度场变化等结果。根据计算结果发现,稀释气体在蒸发器内部流动过程中速度降幅较大,由于蒸发器几何结构因素,麻醉药物蒸发后与稀释气体的混合过程存在不均匀混合现象,即影响了最终蒸发药物浓度的稳定性与精确性,为此给出了麻醉蒸发器的设计优化方案。     

德尔格Zeus麻醉工作站检修5例

正麻醉工作站现广泛地用于各医院的手术室、诱导室和复醒室。应用范围包括成年人、儿童和新生儿患者[1]。它通过机械回路将麻醉药物注入患者的肺泡,在患者体内产生麻醉气体,经血液吸收后,通过血液循环到达中枢神经系统,进而起到麻醉作用。麻醉机主要由气体供应系统、麻醉药品蒸发器、流量控制系统、麻醉呼吸回路组成[2,3]。现将德尔格Zeus(宙斯)麻醉工作站故障分析及检修方法介绍如下。     

Blease-8500型麻醉机常见故障及维修

正麻醉机是医院进行手术时用于麻醉病人的重要工具。麻醉机通过机械回路将麻醉混合气体送入病人的肺泡,形成麻醉药物气体分压,弥散到血液后,对中枢神经系统直接发生抑制作用,从而产生全身麻醉的效果。麻醉机的性能直接关系到手术能否正常的进行。因此,设备的安全性、可靠性、精确性成为衡量麻醉机质量的重要指标~[1]。下面就麻醉机故障维修体会做一叙述。     

神经外科麻醉药物的进展

目的 探讨神经外科手术麻醉药物的进展及其麻醉的最佳方案.方法 查阅文献,分析对比用于神经外科手术的静脉麻醉药、吸入麻醉药、麻醉性镇痛、局部麻醉药及肌松药对中枢神经的作用和影响.结果 对各类麻醉药物的中枢神经作用有了进一步的认识,各麻醉药物联合使用可互相弥补不足.结论 复合多种药物能更好发挥药理作用,达到理想的神经外科麻醉的效果.     

瑞芬太尼在全麻术中对血气与血氧的影响分析

手术全麻可导致机体发生强烈的应激反应,表现为血压升高、心率增快、血压升高、血氧波动等。而通过选择合适的麻醉方法、麻醉药物可以调整和抑制应激反应。瑞芬太尼是麻醉手术中调控应激反应的最常用药物,多用于手术全麻,起效快、维持时间短[1]。本文通过靶浓度控制输注丙泊酚复合瑞芬太尼,观察其对全麻诱导期血气与血样指标的影响,现报告如下。     

麻醉方案对脑肿瘤对流增强给药的影响

目的对流增强给药技术可直接将抗癌药物输注到脑肿瘤组织局部区域,在治疗脑胶质瘤疾病具有广泛的应用前景。给药之前通常患者处于麻醉状态,当前缺乏评估不同麻醉方案对对流增强抗癌药物传输过程的方法。拟通过数值模拟揭示麻醉方案对药物传递的影响。方法通过CT重构建立脑结构及肿瘤组织的物理模型,进而将复杂的脑部组织看作多孔介质,建立组织间液和药物传输的数学模型。以紫杉醇(对照组)为抗癌药,研究对照组及丙泊酚和右美托咪定两种麻醉方案对紫杉醇传输的影响。分析24 h药物传输过程的给药区流场、脑部压力场及药物传递的浓度场。结果台盼蓝染料的扩散系数设置为1.1×10-10m2/s,模型预测的渗透的深度与实验测量结果吻合得很好;对流速度Q=1μL/min,直径0.41 mm和0.31 mm两种输液管产生不同的染色渗透,较小的导管导致了更大渗透深度,但是要求更高的渗透压力。紫杉醇传递过程中2～24 h给药期间,压力分布较为稳定,几乎没有发生变化,但是增加速率逐渐降低。麻醉剂存在的情况,药物传输的深度和传输体积要高于对照组,24 h后,右美托咪定组传输深度相比对照组增加了4.5%,丙泊酚组增加了9.0%。对照组和两种麻醉组速度和压力分布均呈现从针管中心向外逐渐减小的趋势,在对数坐标下,速度与传输深度呈现线性下降关系。结论麻醉方案通过影响脉压而增加了针管附近组织间液的流动速度,进而促进了药物传递。     

稀释介质与稀释方式对化学发光免疫法测定血清雌二醇浓度的影响

探讨不同的稀释介质与稀释方式对化学发光免疫法测定血清雌二醇(Estradiol,E2)浓度的影响.评价SIEMENS Centaur化学发光分析仪的E2测定精密度与线性范围.然后选择线性范围内的血清样品,等分为4份,1份使用仪器自动稀释的方式和配套稀释液D9完成测定,另外3份分别使用配套稀释液D9、混合低值血清和生理盐...     

局部麻醉药物在肿瘤转移和复发中作用的研究进展

围术期肿瘤治疗常需要使用麻醉药物。不同麻醉药物及麻醉方法的选择会影响肿瘤的增殖、转移复发及预后。围术期应用局部麻醉药物(简称局麻药)不仅能减少阿片类药物的用量,尚能通过阻滞肿瘤细胞钠通道、改变表观遗传学、减轻炎性反应和提高免疫功能等机制发挥抑制肿瘤转移和复发的作用。探讨局麻药在肿瘤转移复发中的作用机制,可为围术期肿瘤患者局麻药的合理使用提供新的策略。     

方形孔结构细胞支架非线性流固耦合数值计算

目的讨论三维方形孔细胞支架不同孔隙率和不同孔半径的对细胞表面固体场和流体场的影响,以及将多孔支架视为刚性体和非线性变形体对计算结果的影响。方法采用一种直接耦合解法和和两种间接耦合解法,两种间接耦合解法分别是有限原法(固体模型)与有限差分法(流体模型)耦合、有限原法(固体模型)与有限体积法(流体模型)耦合。对3种流固耦合计算方法的可靠性进行验证。结果通过对构建的12种模型的计算(50、100和150μm三种边长和61%、65%、77%和84%四种孔隙率),获得了固体模型的应力场、应变场和位移场和流体模型的静压、速度、壁面剪应力和切变率,并对结果进行了比较分析。结论将多孔支架视为刚性体和非线性变形体计算结果有一定差别;孔隙率一定时不同孔半径以及孔半径一定时不同孔隙率条件下对固体场和流体场都有不同程度的影响。     

Automatic control of anesthetic delivery and ventilation during surgery

Use of a closed rebreathing circuit for anesthesia delivery offers several advantages: conservation of anesthetic agent, natural heating and humidification of inspired gases, less pollution, and improved monitoring. However, the technique requires careful control of the fresh gas and anesthetic delivery. An anesthesia delivery system has been developed which automatically controls fresh gas delivery, anesthetic delivery, and ventilation in order to regulate circuit volume, oxygen concentration, end-tidal anesthetic concentration, and end-tidal PCO2. This system makes available the advantages of closed-circuit anesthesia without encumbering the anesthesiologist with its more demanding control tasks. The system has undergone clinical testing in adult surgical patients. Maintenance of circuit volume, oxygen concentration, end-tidal anesthetic concentration, and end-tidal PCO2 was achieved by the system in all patients but the first. The anesthetic delivery controller required tuning on the first patient. No further tuning was required for any of the other patients or controllers. During abdominal surgery, the end-tidal bellows position measurement and end-tidal anesthetic concentration measurement increased in variability. The cause of the variability and its elimination are discussed in the article.     

Merits of sponge-like PLGA microspheres as long-acting injectables of hydrophobic drug

Abstract

Our study was initiated to challenge the preconception that nonporous PLGA microspheres with compact matrices should be used to develop long-acting depot injectables of hydrophobic drugs. A simple, new oil-in-water emulsion technique was utilized to produce porous PLGA microspheres with a sponge-like skeleton. Then, their applicability to developing sustained-release depots of hydrophobic drugs was explored in this study. As control, nonporous microspheres with a compact matrix were produced following a typical solvent evaporation process. Both microsphere manufacturing processes used non-halogenated isopropyl formate and progesterone as a dispersed solvent and a model hydrophobic drug, respectively. Various attempts were made to evaluate critical quality attributes of the porous microspheres and the nonporous ones. Surprisingly, the former displayed interesting features from the viewpoints of manufacturability and microsphere quality. For example, the spongy microspheres improved drug encapsulation efficiency and particle size uniformity, inhibited drug crystallization during microencapsulation, and minimized the residual solvent content in microspheres. Furthermore, the porous microspheres provided continual drug release kinetics without a lag time and much faster drug release than the non-porous microspheres did. In summary, the porous and sponge-like PLGA microspheres might find lucrative applications in developing sustained release dosage forms of hydrophobic drugs.     

Barium sulphate-loaded p(HEMA) microspheres as artificial emboli: preparation and properties

Poly(2-hydroxyethyl methacrylate) p(HEMA) microspheres of good spherical geometry (diameter 90-1500 microns) encapsulated with 40-50% barium sulphate to impart radiopaque properties were prepared by a solvent evaporation process. These microspheres were cross-linked by reacting with hexamethylene diisocyanate (HMDI) or by gamma-irradiation in the presence of ethylene glycol dimethacrylate (EGDM) in n-heptane. Microspheres with a porous structure and a rough surface were also made by the incorporation of NaCl along with BaSO4. The effects of concentration of the polymer solution, concentration of the stabilizing agent, concentration of BaSO4, viscosity of the dispersion medium and ratio of the dispersed phase to the dispersion medium on the formation, stability and particle size distribution of the microspheres were investigated.     

A Cascade Feedback Control Approach for Hypnosis

This article studies the problem of controlling the drug administration during an anesthesia process, where muscle relaxation, analgesia, and hypnosis are regulated by means of monitored administration of specific drugs. On the basis of a seventh-order nonlinear pharmacokinetic-pharmacodynamic representation of the hypnosis process dynamics, a cascade (master/slave) feedback control structure for controlling the bispectral index (BIS) is proposed. The master controller compares the measured BIS with its reference value to provide the expired isoflurane concentration reference to the slave controller. In turn, the slave controller manipulates the anesthetic isoflurane concentration entering the anesthetic system to achieve the reference from the master controller. The advantage of the proposed cascade control structure with respect to its noncascade counterpart is that the former provides operation protection against BIS measurement failures. In fact, under a BIS measurement fault, the master control feedback is broken and the slave controller operates under a safe reference value. Extensive numerical simulations are used to illustrate the functioning of the proposed cascade control structure.     

Gas foamed open porous biodegradable polymeric microspheres

Highly open porous biodegradable polymeric microspheres were fabricated for use as injectable scaffold microcarriers for cell delivery. A modified water-in-oil-in-water (W1/O/W2) double emulsion solvent evaporation method was employed for producing the microspheres. The incorporation of an effervescent salt, ammonium bicarbonate, in the primary W1 droplets spontaneously produced carbon dioxide and ammonia gas bubbles during the solvent evaporation process, which not only stabilized the primary emulsion, but also created well inter-connected pores in the resultant microspheres. The porous microspheres fabricated under various gas foaming conditions were characterized. The surface pores became as large as 20 microm in diameter with increasing the concentration of ammonium bicarbonate, being sufficient enough for cell infiltration and seeding. These porous scaffold microspheres could be potentially utilized for cultivating cells in a suspension manner and for delivering the seeded cells to the tissue defect site in an injectable manner.     

Demonstrating the Influence of Compression on Artery Wall Mass Transport

The development of restenosis within the coronary arteries after a stenting procedure has been addressed with the development of the drug eluting stent device. However, in recent times the superiority of the drug eluting stent over bare metal stents has been brought into question. A lack of knowledge regarding the behavior of drug transport from the drug eluting devices contributes to this uncertainty. Questions arise as to whether drug eluting stents deliver sufficient amounts of therapeutic agents into the artery wall to suppress restenosis. Published investigations in this area have focused primarily on trends associated with how variations in stenting conditions affect mass transport behavior. However, experimentally validated numerical models that simulate mass transport within the artery wall are lacking. A novel experimental model was developed to validate computational predictions of species diffusion into a porous medium and an investigation into how stent strut compression influences mass transport was conducted. The study revealed that increased compressive forces on a porous media reduced the ability of species to diffuse through that media, and in relation to drug eluting stents will contribute to a reduction in therapeutic levels of drugs within the wall.     

Intradermal Tests for Diagnosis of Drug Allergy are not Affected by a Topical Anesthetic Patch

The use of topical anesthesia to perform intradermal tests (IDTs) for drug allergy diagnosis was never investigated. We aimed to determine the effects of a topical anesthetic patch containing prilocaine-lidocaine on wheal size of IDT with drugs. Patients who had positive IDT as part of their investigation process of suspected drug hypersensitivity were selected. IDT were performed according to guidelines. Anesthetic patch (AP) was placed and the same prior positive IDT, as well as positive histamine skin prick test (SPT) and negative (saline IDT) controls, were performed in the anesthetized area. Patients with negative IDT were also included to check for false positives with AP. Increase in wheals after 20 minutes both with and without AP was recorded and compared. 45 IDT were performed (36 patients), of which 37 have been previously positive (14 antibiotics, 10 general anesthetics, 6 non-steroidal anti-inflammatory drugs, 3 iodinated contrasts, 3 anti-Hi-histamines and 1 ranitidine). Mean histamine SPT size without the AP was 4.7 mm [95%CI (4.4-5.1]), and 4.6 mm [95%CI(4.2-5.0)] with anesthesia. Mean wheal increase in IDT for drugs without the anesthesia was 4.5 mm [95%CI(3.3-5.7)] and with anesthesia was 4.3 mm [95%CI(2.8-5.8)]. No statistical significant differences were observed between skin tests with or without AP for histamine SPT (P=0.089), IDT with saline (P=0.750), and IDT with drugs (P=0.995). None of the patients with negative IDT showed positivity with the AP, or vice-versa. The use of an AP containing prilocaine-lidocaine does not interfere with IDT to diagnose drug allergy, and no false positive tests were found.     

Drug release from a porous ion-exchange membrane in vitro.

The effect of environmental ionic strength on the rate of drug release from a cation exchange membrane was evaluated. Cationic propranolol-HCl, timolol, sotalol-HCl, atenolol and dexmedetomidine-HCl and neutral diazepam were adsorbed onto a porous poly(vinylidene fluoride) (PVDF) membrane that was grafted with bioadhesive poly(acrylic acid) chains (PAA-PVDF). Despite its porosity, the PAA-PVDF membrane acted as a cation exchange membrane. The release of adsorbed drug from the PAA-PVDF membrane was investigated by using a USP rotating basket apparatus. Adsorption of cationic drugs onto the PAA-PVDF membrane tended to increase with increasing lipophilicity of the drug. A decrease in the ionic strength of the adsorption medium increased the amount of the cationic drugs adsorbed onto the membrane, but had no effect on diazepam adsorption. The release of cationic drugs from the PAA-PVDF membrane was greatly affected by the ionic strength of both the adsorption medium and the dissolution medium, while ionic strengths did not affect diazepam release. Our results suggest that the ionic strength of both the adsorption and dissolution media substantially affects the release rate of a drug that has been adsorbed onto the ion exchange membrane, primarily via electrostatic interactions, while ionic strength has no effect on the release of a drug which has been adsorbed onto the membrane via non-electrostatic forces.     

麻醉剂浓度对大鼠暴发-抑制脑电特征的影响

暴发-抑制脑电图(EEG)是深度麻醉状态下EEG活动受到严重抑制的表现。为定量研究暴发-抑制波形特征与麻醉剂浓度之间的关系,本文采用暴发-抑制比、暴发频率、暴发幅度和抑制幅度4个时域指标,分析大鼠麻醉模型在不同异氟烷浓度下的EEG特征。结果表明,暴发-抑制脑电的4个指标均随异氟烷浓度的改变而变化:异氟烷浓度越大,暴发-抑制比和暴发幅度越大,暴发频率和抑制幅度越小。暴发-抑制比可快速反映异氟烷浓度的变化,且个体间一致性高,有潜力作为深度麻醉状态下暴发-抑制EEG较理想的特征指标。