成人和小儿异氟醚低流量麻醉时体重与挥发罐开启刻度的关系

低流量麻醉时由于新鲜气体流量低,从挥发罐带走的麻醉蒸气较少及呼出气稀释环路气体,吸入麻醉药的挥发罐开启浓度与环路中的浓度存在明显差异。从习惯的半紧闭系统采用的流量平衡麻醉方法到紧闭系统的定量平衡麻醉方法,对于吸入麻醉药的气体浓度而言,始终没有一个实用的个体化吸入浓度参考标准。吸入麻醉药的吸收与肺泡通气量、心输出量有关,而肺泡通气量、心输出量都与体重3/4因子有关,因此从药代动力学的观点看,体重可能可以作为建     

安氟醚最低流量麻醉

目前临床使用的麻醉机吸入全麻药均经呼吸回路外的挥发罐挥发,由于功能残气量和呼吸回路具有很大的容积,因此常需较大的新鲜气流量进行调控吸入麻醉药浓度,其结果必然造成药物的浪费和环境污染。为此我们选择安氟醚采用最低流量麻醉法进行临床研究。资料与方法一般资料　22例ＡＳＡⅠ～Ⅱ级脊柱和脑外科择期手术病人,男14例,女8例,年龄22～64岁(492±63岁),体重621±57ｋｇ,术前心、肺、肝、肾功能均正常。麻醉方法　术前1小时肌注苯巴比妥钠01ｇ、阿托品03～04ｍｇ。硫喷妥钠6ｍｇ/ｋｇ、芬太尼4～5μｇ/ｋｇ及琥珀胆碱100ｍｇ静注后气管内…     

低流量循环下麻醉药吸入浓度的动物实验研究

为考证低流量循环吸入麻醉过程中麻醉药吸入浓度的变化规律，俭测了６只杂种犬在长时间吸人麻醉过程中吸气末、呼气末及挥发器输出端气体中麻醉药（异氟醚）的浓度。实验中氧流量固定在０．３Ｌ／ｍｉｎ，挥发器开启２％档持续６小时以上。结果显示挥发器输出浓度稳定，麻醉初期吸入气麻醉药浓度远低于挥发器输出浓度，但逐渐升高，至麻醉１５０分钟后吸入浓度趋于平稳，在此后 ２００分钟内吸入气麻醉药浓度与挥发器输出浓度可保持基本稳定的比例关系。     

听觉诱发电位指数监测患者吸入异氟醚麻醉深度的准确性

目的 评价听觉诱发电位指数(AAI)监测患者异氟醚吸入麻醉深度的准确性.方法 30例择期全麻手术患者,ASA Ⅰ或Ⅱ级.麻醉诱导气管插管后15 min开始以3 L/min氧流量(高流量)洗人,12 min后调整为0.5 L/min氧流量(低流量)维持,调节异氟醚挥发罐刻度,使异氟醚呼气末浓度依次为0.8 MAC、1.0 MAC和1.3 MAC,每个浓度维持20 min,分别于诱导前(基础状态)、诱导后即刻、吸人异氟醚前即刻、高流量洗入3 min、6 min、9 min、12 min及低流量维持期异氟醚呼气末浓度分别为0.8 MAC、1.0 MAC、1.3 MAC时监测平均动脉压、心率和AAI.结果 与吸入异氟醚前即刻比较,高流量洗人期AAI降低,且高流量洗人期AAI逐渐降低(P＜0.05).低流量维持期异氟醚呼气末浓度为0.8 MAC、1.0 MAC和1.3 MAC时,随浓度的增加AAI逐渐降低(P＜0.05),在此范围内AAI与异氟醚呼气末浓度的相关系数为-0.896(P＜0.01).结论 AAI可用于监测患者异氟醚吸入麻醉的深度.     

闭合环路定量输入七氟醚法及耗药量的探讨

目的 :采用Lowe方式施行密闭循环回路内定量麻醉 (CCA) ,并与常规挥发罐密闭循环麻醉方式比较 ,探讨七氟醚药量的消耗。方法 :42例ASAⅠ～Ⅱ级病人 ,随机分为两组 :Lowe方式组及常规挥发罐组。术中记录呼气末七氟醚浓度 ,并计算 12 1分钟时间内耗药量。结果 :Lowe方式在 9分钟达到预定值 ,挥发罐组在 36分钟达到预定值。12 1分钟时间内七氟醚耗药量在Lowe方式组为 8± 1ml,挥发罐组为 16± 2ml。结论 :Lowe方式较挥发罐法吸入速度快 ,更能节省用药量。     

患者低流量吸入地氟醚或异氟醚的药代动力学

目的比较腹部手术患者低流量吸入地氟醚或异氟醚的药代动力学。方法腹部手术患者40例,ASAⅠ级或Ⅱ级,年龄18～64岁,BMI＜35kg/m^2。随机分为2组（n=20）：地氟醚组（D组）和异氟醚组（Ⅰ组）。麻醉诱导后调节纯氧流量3L/min,术中调整挥发罐刻度,维持肺泡浓度（FA）0．8 MAC,稳定5min后纯氧流量改为1L/min。调节瑞芬太尼静脉输注速率,维持HR和BP波动幅度不超过基础值20%。手术结束时,停止吸入地氟醚或异氟醚,同时吸入纯氧3L/min。记录设定的吸入麻醉药浓度（FD）、吸入麻醉药浓度（FI）、FA/FI=1/2时间、FA/FAO=1/2时间（FAO为关闭挥发罐即时的肺泡浓度）,并计算各时点FA/FI、FA/FD。结果D组FA/FI=1/2时间及FA/FAO=1/2时间均较Ⅰ组缩短（P＜0．05）。低流量麻醉下,D组FD稳定,Ⅰ组FD波动较大。D组FA/FI、FA/FD上升速率较Ⅰ组快,且同一时点各比值D组均高于Ⅰ组。结论与异氟醚比较,腹部手术患者低流量吸入地氟醚时达到预定的肺泡浓度更迅速,可控性好,停止吸入时排泄较快。     

基于Fick定律导出公式的异氟醚静脉血药浓度控制系统的建立及其评价

调控吸入麻醉药最常用的方法是根据患者生命体征旋转挥发罐的刻度而达到所需的麻醉深度.与麻醉药效应相关程度较高的为吸入麻醉药的有效血药浓度~[1],由于挥发罐流出的药物首先要在麻醉环路形成一定的浓度,再在肺泡内形成一定的浓度,麻醉药经过两次缓冲才能进入血液,旋转挥发罐刻度并不能准确地调控血药浓度.     

回路内麻醉气体吸附器的临床应用

目的在吸入麻醉术后恢复阶段,观察回路内麻醉气体吸附器是否可缩短吸入麻醉的苏醒时间。方法在固定潮气量、每分通气量和新鲜气体流量的条件下,术毕关闭挥发罐后,比较使用回路内麻醉气体吸附装置对回路内麻醉气体浓度变化的影响。结果使用吸附器后,回路内麻醉气体浓度降至MAC0．3所需时间,异氟醚由20．0±0．3分钟降至3．3±0．5分钟(P＜0．01)。安氟醚由25．0±0．1分钟降至3．5±0．5分钟(P＜0．01)。结论应用回路内麻醉气体吸附器可显著缩短病人苏醒时间,并减少气源浪费和环境污染。     

低流量紧闭麻醉的回路内七氟醚注药法

目的：采用回路内直接注入七氟醚为２５例病人行低流量紧闭麻醉。方法：将七氟醚液体分次注入钠石灰罐，首次量２ｍｌ，追加量每次１ｍｌ。七氟醚呼气末浓度维持在１％以上。结果：第１ｈ的七氟醚用量为６．９２±２．１６ｍｌ，第２ｈ为４．５７±０．６６ｍｌ（１４例）。首次注药２ｍｌ产生的最大吸入和呼出浓度分别为０．６％～１．７％和０．４％～１．３％。随着麻醉时间的延长，七氟醚的摄取速率减慢，追加给药产生的吸入浓度上升幅度逐渐增大。而七氟醚的用量与体重的相关性较差。结论：钠石灰罐分次注入七氟醚行低流量紧闭麻醉简便可行。     

计算机模拟中国人吸入麻醉药的肺泡浓度升高速度

目的：模拟中国人氟化吸入麻醉药诱导过程。方法：应用Gas Man(R) Version 2.1 for Windows(TM)软件完成模拟。模拟参数设为：体重60kg；人体分为肺泡、血液、血流丰富组织（VRG）、肌肉和脂肪组织；每分肺泡通气量为4L，心输出量为5L，肺泡功能残气量为2.5L；吸入麻醉以半紧闭回路（回路容积为8L）；模拟地氟烷、七氟烷、异氟烷和安氟烷在新鲜气体流量为3L/min，挥发罐输出浓度（FD）以6%地氟烷、2%七氟烷、1.15%异氟烷、1.68%安氟烷条件下麻醉药吸入浓度（F1）和肺泡麻醉药浓度（FA），计算FA/F1比值。模拟采用的血/气及组织/气分配系数分别取自文献报道的中国人和西方白种人的结果。数据采集时间为开启挥发罐后的1min、2min、3min、5min 、10min、15min、25min、45min和75min 。比较吸入麻醉药的FA/F1升高速度在中国人和白种人之间的差异。结果：地氟烷FA/F1在45min之前为中国人低于白种人。对于七氟烷、异氟烷和安指烷，中国人的FA/F1在15min之后高于白种人。结论：吸入麻醉药的分配系数是导致FA/F1在15min之前明显低于白种人，15min后逐渐趋于相同。而对于七氟烷、异氟烷和安氟烷来说，两个人种的差别主要表现在中国人的肌肉/气分配系数较低。模拟结果提示在诱导开始15min之后，这三种麻醉药在中国人的FA/F1明显高于白种人。     

Comparison of costs of different anaesthetic techniques

The costs of anaesthetic drugs, intravenous agents as well as gases, were studied for different anaesthetic techniques in a medium-sized operative procedure, cholecystectomy. Three anaesthetic breathing systems were used: a non-rebreathing system, a circle absorber system with medium fresh gas flows of 3-6 l/min, and a low-flow circle system. Anaesthesia without volatile inhalation agents used with a low-flow technique was the least expensive, and anaesthesia with isoflurane in a non-rebreathing system was the most expensive. The costs of anaesthesia without volatile inhalation agents in a non-rebreathing system, enflurane anaesthesia in a circle system with medium fresh gas flows, and isoflurane anaesthesia with low-flow technique were similar.     

Effects of Low-flow Sevoflurane Anesthesia on Renal Function: Comparison with High-flow Sevoflurane Anesthesia and Low-flow Isoflurane Anesthesia

Background: The safety of low-flow sevoflurane anesthesia, during which CF2 = C(CF3)-O-CH2 F (compound A) is formed by sevoflurane degradation, in humans has been questioned because compound A is nephrotoxic in rats. Several reports have evaluated renal function after closed-circuit or low-flow sevoflurane anesthesia, using blood urea nitrogen (BUN) and serum creatinine as markers. However, these are not the more sensitive tests for detecting renal damage. This study assessed the effects of low-flow sevoflurane anesthesia on renal function using not only BUN and serum creatinine but also creatinine clearance and urinary excretion of kidney-specific enzymes, and it compared these values with those obtained in high-flow sevoflurane anesthesia and low-flow isoflurane anesthesia.

Methods: Forty-eight patients with gastric cancer undergoing gastrectomy were studied. Patients were randomized to receive sevoflurane anesthesia with fresh gas flow of 1 l/min (low-flow sevoflurane group; n = 16) or 6-10 l/min (high-flow sevoflurane group; n = 16) or isoflurane anesthesia with a fresh gas flow of 1 l/min (low-flow isoflurane group; n = 16). In all groups, the carrier gas was oxygen/nitrous oxide in the ratio adjusted to ensure a fractional concentration of oxygen in inspired gas (FiO2) of more than 0.3. Fresh Baralyme was used in the low-flow sevoflurane and low-flow isoflurane groups. Glass balls were used instead in the high-flow sevoflurane group, with the fresh gas flow rate adjusted to eliminate rebreathing. The compound A concentration was measured by gas chromatography. Gas samples taken from the inspiratory limb of the circle system at 1-h intervals were analyzed. Blood samples were obtained before and on days 1, 2, and 3 after anesthesia to measure BUN and serum creatinine. Twenty-four-hour urine samples were collected before anesthesia and for each 24-h period from 0 to 72 h after anesthesia to measure creatinine, N-acetyl-beta-D-glucosaminidase, and alanine aminopeptidase.

Results: The average inspired concentration of compound A was 20 +/- 7.8 ppm (mean +/- SD), and the average duration of exposure to this concentration was 6.11 +/- 1.77 h in the low-flow sevoflurane group. Postanesthesia BUN and serum creatinine concentrations decreased, creatinine clearance increased, and urinary N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase excretion increased in all groups compared with preanesthesia values, but there were no significant differences between the low-flow sevoflurane, high-flow sevoflurane, and low-flow isoflurane groups for any renal function parameter at any time after anesthesia.     

Evaluation of an Oxford Miniature Vaporizer placed in-circuit during the maintenance phase of low-flow anaesthesia

The aim of the study was to assess Oxford Miniature Vaporizer output when mounted in-circuit during the maintenance phase of anaesthesia, using isoflurane, controlled ventilation and a fresh gas flow rate less than 1 l/min. Twenty patients of ASA Physical Status I and II were recruited from routine general surgical lists. All patients were paralysed and ventilated. An out-of-circuit isoflurane vaporiser was used during the induction period (first 20 to 30 minutes). Anaesthesia was maintained using an Oxford Miniature Vaporizer placed in-circuit, using a fresh gas flow of 500 ml/min. The end-tidal isoflurane concentration was recorded for 90 minutes at five-minute intervals using a sidestream agent analyser. Two groups were compared, with the Oxford Miniature Vaporizer dial setting at either the 0.5 mark (low output setting) or at the 1.0 mark (higher output setting). At a dial setting of 0.5, the Oxford Miniature Vaporizer produced a steady end-tidal isoflurane of 0.63% (95% confidence interval 0.60 to 0.66). However, when the dial was turned to 1.0 the output was almost always excessive and had to be reduced. These findings indicate that a stable, predictable and clinically useful output can be achieved when the Oxford Miniature Vaporizer is positioned in-circuit using low-flow and controlled ventilation.     

听觉诱发电位指数监测患者吸入异氟醚麻醉深度的准确性

Objective To evaluate the accuracy of auditory evoked potential index (AAI) in monitoring the anesthetic depth during isoflurane anesthesia.Methods Thirty ASA Ⅰ or Ⅱ patients aged 18-55 years and undergoing elective surgery under general anesthesia were enrolled in this study. The patients were unpremedicated. Anesthesia was induced with midazolam 0.05 mg/kg, fentanyl 3 μg/kg and propofol 1 mg/kg. Tracheal intubation was facilitated with recuronium 0.1 mg/kg. The patients were mechanically ventilated (VT:40 mm Hg. Anesthesia was maintained with isoflurane inhalation and intermittent intravenous boluses of vecuronium. Isoflurane was started with high-flow (FGF, 3 L/min) for 12 min followed by low-flow (LGF, 0.5 L/min). The inspired isoflurane concentration was set at 3%. The electrocardiogram (ECG), mean arterial pressure (MAP), heart rate (HR), pulse oxygen saturation (SpO2), end-tidal isoflurane concentration and AAI were continuously monitored during anesthesia and recorded before induction of anesthesia (baseline, To ), immediately after induction (T1), immediately before isoflurane inhalation (T2), at 3 min(T3), 6 min (T4), 9 min (T5) and 12 min (T6) during high-flow wash-in and at the end-tidal isoflurane concentrations of 0.8 MAC (T7), 1.0 MAC (T8) and 1.3 MAC (T9) during low-flow inhalation of isoflurane, respectively.Results AAI decreased gradually while the end-tidal isoflurane concentration increased during high-flow wash-in. And AAI was negatively correlated with the end-tidal isoflurane concentrations ( r = -0.896, P ＜ 0.01 ) during low-flow inhalation of isoflurane anesthesia.     

The ADU vaporizing unit: a new vaporizer

We determined the performance of the vaporizer of the ADU machine (Anesthesia Delivery Unit; Datex-Ohmeda, Helsinki, Finland). The effects of carrier gas composition (oxygen, oxygen/N(2)O mixture, and air) and fresh gas flow (0.2 to 10 L/min) on vaporizer performance were examined with variable concentrations of isoflurane, sevoflurane, and desflurane across the whole range of each vaporizer's output. In addition, the effects of sudden changes in fresh gas flow and carrier gas composition, back pressure, flushing, and tipping were assessed. Vaporizer output depended on fresh gas flow, carrier gas composition, dial settings, and the drug used. Vaporizer output remained within 10% of dial setting with fresh gas flows of 0.3-10 L/min for isoflurane, within 10% of dial setting with fresh gas flows of 0.5-5 L/min for sevoflurane, and within 13% of dial setting with fresh gas flows of 0.5 to 1 L/min for desflurane. Outside these fresh gas flow ranges, output deviated more. The effect of sudden changes in fresh gas flow or carrier gas composition, back pressure, flushing, and tipping was minimal. We conclude that the ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer. IMPLICATIONS: The ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer.     

Effect of N2O on Sevoflurane Vaporizer Settings during Minimal- and Low-flow Anesthesia

Background: Uptake of a second gas of a delivered gas mixture decreases the amount of carrier gas and potent inhaled anesthetic leaving the circle system through the pop-off valve. The authors hypothesized that the vaporizer settings required to maintain constant end-expired sevoflurane concentration (Etsevo) during minimal-flow anesthesia (MFA, fresh gas flow of 0.5 l/min) or low-flow anesthesia (LFA, fresh gas flow of 1 l/min) would be lower when sevoflurane is used in oxygen-nitrous oxide than in oxygen.

Methods: Fifty-six patients receiving general anesthesia were randomly assigned to one of four groups (n = 14 each), depending on the carrier gas and fresh gas flow used: group Ox.5 l (oxygen, MFA), group NOx.5 l (oxygen-nitrous oxide, MFA after 10 min high fresh gas flow), group Ox1 l (oxygen, LFA), and group NOx1 l (oxygen-nitrous oxide, LFA after 10 min high fresh gas flow). The vaporizer dial settings required to maintain Etsevo at 1.3% were compared between groups.

Results: Vaporizer settings were higher in group Ox.5 l than in groups NOx.5 l, Ox1 l, and NOx1 l; vaporizer settings were higher in group NOx.5 l than in group NOx1 l between 23 and 47 min, and vaporizer settings did not differ between groups Ox1 l and NOx1 l.     

A comparison of the effects of prolonged (>10 hour) low-flow sevoflurane, high-flow sevoflurane, and low-flow isoflurane anaesthesia on hepatorenal function in orthopaedic patients

This study compared the effects of low-flow sevoflurane, high-flow sevoflurane and low-flow isoflurane on hepatorenal function during and after more than 10 hours of anaesthesia. Twenty-five patients scheduled for elective orthopaedic surgery were categorized into three groups; low-flow sevoflurane (fresh gas flow at 1 litre/min, n = 9), high-flow sevoflurane (5 l/rmin, n = 7), or low-flow isoflurane (1 l/min, n=9). Inspiratory compoundA concentrations were measured. The groups had similar duration of anaesthesia and exposure to anaesthetic agents. The area under the curve of concentration (mean, SD) of compound A in the low-flow sevoflurane group (359.8, 106.1 ppm.h) was greater than that in the high-flow sevoflurane group (61.1, 29.3 ppm.h; P<0.01). All groups showed normal plasma creatinine and creatinine clearance, and transient postoperative increases in plasma alanine aminotransferase and alpha glutathione-S-transferase, as well as urinary glucose and alpha glutathione-S-transferase, with no significant differences between groups. There were no significant relationships between the area under the curve of concentration of compound A and the biomarkers. These findings suggest that prolonged anaesthesia with low-flow sevoflurane has similar effects on hepatorenal function to prolonged anaesthesia with high-flow sevoflurane and low-flow isoflurane.     

Minimum alveolar anesthetic concentration of isoflurane with different xenon concentrations in Swine

For patients requiring a fraction of inspired oxygen more than 0.3, the use of xenon (Xe) as the sole anesthetic is limited because of its large minimum alveolar anesthetic concentration (MAC) of 71%. This warrants investigating the combination of Xe with other inhaled anesthetics. We therefore investigated the influence of Xe on the MAC of isoflurane. The study was performed in 10 swine (weight, 28-35 kg) ventilated with Xe 0%, 15%, 30%, 40%, 50%, and 65% in oxygen. For each Xe concentration, various concentrations of isoflurane were administered in a step-wise design. For each combination, a supramaximal pain stimulus (claw-clamp) was applied, and the appearance of a withdrawal reaction was recorded. The isoflurane MAC was defined as the end-tidal concentration required to produce a 50% response rate. At each Xe concentration, the responses to the pain stimulus were categorized, and a logistic regression model was fitted to the results to determine isoflurane MAC. Isoflurane MAC was decreased by inhalation of Xe in a nonlinear manner from 1.92% (95% confidence interval, 1.70%-2.15%) with 0% Xe to 1.17% (95% confidence interval, 0.75%-1.59%) with 65% Xe. Although this indicates partial antagonism of the two anesthetics, a combination of Xe with isoflurane may prove valuable for patients requiring a fraction of inspired oxygen more than 0.3. IMPLICATIONS: We investigated the influence of the anesthetic gas xenon on the minimum alveolar anesthetic concentration (MAC) for isoflurane (another anesthetic gas). The study was performed in 10 swine ventilated with fixed xenon and various concentrations of isoflurane. The isoflurane MAC is decreased by inhalation of xenon in a nonlinear relationship.     

Comparison of plasma α glutathione S-transferase concentrations during and after low-flow sevoflurane or isoflurane anaesthesia

BACKGROUND: We evaluated the effect of low-flow sevoflurane anaesthesia, in which compound A is generated, and isoflurane anaesthesia, in which compound A is not generated (n=13 in each group), on hepatocellular integrity using alpha glutathione S-transferase (GST). Alpha GST is a more sensitive and specific marker of hepatocellular damage than is aminotransferase activity and correlates better with hepatic histology. METHODS: Sevoflurane or isoflurane were delivered without nitrous oxide with a fresh gas flow of 1 l/min. Concentrations of compound A in the circuit were measured hourly, and plasma alpha GST concentrations were measured perioperatively. RESULTS: Mean duration of anaesthesia was 338+/-92 min in the sevoflurane group and 320+/-63 min in the isoflurane group. Mean compound A concentration in the sevoflurane group was 28.6+/-9.0 ppm. There was no significant difference in alpha GST concentrations between the sevoflurane and isoflurane groups during or after anaesthesia. CONCLUSION: These results indicate that low-flow sevoflurane and isoflurane anaesthesia have the same effect on hepatic function, as assessed by plasma alpha GST concentrations.