不同年龄国人的吸入麻醉药血/气分配系数及决定因素

目的 测定吸入麻醉药在不同年龄国人中的血／气分配系数，判断年龄是否影响Ｂ／Ｇ及确定影响Ｂ／Ｇ的血液成份。方法：１００例从出生至８４岁的国人按年龄分为１０组，每组１０例，男女各半。应用两次平稳法同时测定地氟醚、七氟醚、异氟醚、安氟醚和氟烷的Ｂ／Ｇ，并测定血浆白蛋白，球蛋白，甘油三酯和胆固醇浓度及血红细胞压积。     

紫绀型与非紫绀型先天性心脏病患儿吸入麻醉药血／气分配系数

目的：测定并比较紫绀型与非紫绀型先天性心脏病患儿吸入麻醉药／气分配系数（Ｂ／Ｇ）,判断红细胞压积对Ｂ／Ｇ影响。方法：紫绀型与非紫绀型先天性心脏病患儿各１０例,平均年龄５岁,采桡动脉血１０ｍｌ,用两次平衡法测定地氟醚,异氟醺客氟烷的Ｂ／Ｇ,并测定血浆总胆固醇、甘油三脂,白蛋白、球蛋白浓度和Ｈｃｔ,ｔ检验比较两组间血液成分和吸入麻醉药Ｂ／Ｇ有无差别。结果：紫绀型与非紫绀型先天性心脏病患儿Ｈｃｔ有显著差     

体外循环中吸入地氟醚、异氟醚和氟烷血/气分配系数的计算

体外循环（ＣＰＢ）期间,低温和血液稀释均影响吸入麻醉药的血／气分配系数（Ｂ／Ｇ）。本研究实际测定了常用吸入麻醉药在ＣＰＢ期间的Ｂ／Ｇ,并与根据经验公式得出的推测值进行了相关性分析,为正确了解ＣＰＢ中吸入麻醉药的药代动力学特点提供帮助。资料和方法选择２０例风湿性心脏病,拟行心脏瓣膜置换术的患者,于ＣＰＢ转机后１５分钟取血标本,每例５０ｍｌ。应用注射器两次平衡法同时测定地氟醚、异氟醚和氟烷在３７℃、３３℃、２９℃、２５℃、２１℃、和１７℃条件下的Ｂ／Ｇ。记录病人入手术室后至取血标本时的静脉输液和ＣＰ…     

紫绀型与非紫绀型先天性心脏病患儿吸人麻醉药血／气分配系数

目的测定并比较紫绀型与非紫绀型先天性心脏病患儿吸入麻醉药血／气分配系数(B／G),判断红细胞压积(Hct)对B／G的影响。方法紫绀型与非紫绀型先天性心脏病患儿各10例,平均年龄5岁,采桡动脉血10ml,用两次平衡法测定地氟醚、异氟醚和氟烷的B／G,并测定血浆总胆固醇、甘油三脂、白蛋白、球蛋白浓度和Hct,t检验比较两组间血液成分和吸入麻醉药B／G有无差别。结果紫绀型与非紫绀型先天性心脏病患儿Hct有显著差异(紫绀型为68．7％±11．1％,非紫绀型37．7％±2．9％,P<0．05);但两组间其他血浆成分和三种吸入麻醉药的B／G无差异(P>0．05)。结论Hct对B／G无影响,紫绀型与非紫绀型先天性心脏病患儿的B／G无显著性差异。     

改变氧流量对半紧闭吸入麻醉药浓度的影响

采用自身对照法，通过连续监测异氟醚、安氟醚在１．５Ｌ／ｍｉｎ、２Ｌ／ｍｉｎ、３Ｌ／ｍｉｎ、４Ｌ／ｍｉｎ氧流量下的浓度变化，探讨氧流量改变对吸入麻醉药浓度及摄取的影响。结果表明：各组吸入浓度出现时间无显著差异；异氟醚、安氟醚的吸入浓度，均随氧流量的增加而增高；全麻药的摄取量随氧流量的高低而不等。结论：在同一标刻浓度下，氧流量与全麻药的吸入浓度呈正相关，标刻浓度越高，吸入浓度受氧流量变化的影响越大。摄取量也随之受到影响。提示在临床麻醉中，改变新鲜气体流量时，要考虑到对全麻药吸入浓度及摄取的影响     

挥发性吸入麻醉药对短潜伏期体感诱发电位的影响

目的 选择合适的吸入麻醉药及其浓度，为术中体感诱发电位（SSEP）监测提供参考。方法 60例择期行神经外科手术的患者随机分为三组：安氟醚组、怫氟醚组和地氟醚组。每个患者在清醒和挥发性麻醉药呼气末浓度分别为0．3、0．5、0．75、1．0和1．5MAC时记录正中神经体感诱发电位N13（颈髓）及N20（大脑皮层）。观察皮层电位N20、颈髓电位N13的潜伏期、波幅和中枢传导时间（CCT）的变化。结果 三种吸入麻醉药不改变皮层下电位N13的潜伏期和波幅（P＞0．05）。而皮层电位N20的潜伏期和中枢传导时间（CCT）随安氟醚、异氟醚和地氟醚呼气末浓度的增加，逐渐延长，波幅则下降（P＜0．05）。其中吸入安氟醚在呼出末浓度1．0MAC时有3例患者波形消失，在1．5MAC时共有6例患者波形消失，而异醚和地氟醚呼吸末浓度只在1．5MAC时有3个患者波形消失。结论（1）挥发性吸入麻醉药对SSEP的皮层成分N20波潜伏期和波幅的影响呈浓度依赖性，对皮层下成分N13波影响轻微；（2）在三种吸入麻醉药中，安氟醚对皮层SSEP影响比异氟醚及地氟醚更大，而后者作用相似。术中SSEP监测时，安氟醚在呼气末浓度不大于0．75MAC时是合适的；异氟醚、地氟醚在呼气末浓度不大于1．0MAC时是合适的。     

地氟醚、七氟醚和异氟醚对内源性一氧化氮的影响

目的：观察犬吸入地氟醚、七氟醚和异氟醚后血浆ＮＯ含量的变化，以进一步探讨ＮＯ在囱族吸入麻醉药扩血管作用中的地位。方法：犬麻醉后３０分钟，随机吸入地氟醚、一氟醚或异氟醚（ＭＡＣ ７．２％￣２．３％和１．２８％）使呼气末浓度达１ＭＡＣ，持续３０分钟。分别于呼气末浓度达１ＭＡＣ后５分钟、１５分钟和３０分钟和停吸后３０分钟分钟和１２０分钟抽取静脉血，用硝酸盐还原酶法测定ＮＯ。结果：ＮＯ水平在三组药物吸入过     

吸入麻醉药对人血浆和血小板血栓素B2生成与血小板聚集的影响

目的：探讨吸入麻醉剂氟烷、安氟醚和异氟醚对人血浆血栓素Ｂ２（ＴＸＢ２），血小板ＴＸＢ２生成与血小板聚集的影响。方法：血浆ＴＸＢ２和血小板ＴＸＢ２的生成量用放免分析法测量，血小板聚集率用比浊法测量。结果：吸入１ＭＡＣ氟烷３０分钟后，血浆ＴＸＢ２浓度、二磷酸腺苷（ＡＤＰ）和肾上腺素（Ｅ）诱导的血小板ＴＸＢ２生成量与血小板聚集率显著下降，吸入１ＭＡＣ安氟醚３０分钟后，血浆ＴＸＢ２浓度和血小板ＴＸＢ２生成量与血小板聚集率亦显著下降，其降低的程度比氟烷轻。吸入１ＭＡＣ异氟醚对上述指标无明显影响。血小板ＴＸＢ２生成的减少与血小板聚集率的下降呈显著正相关。结论：氟烷显著抑制血小板聚集，安氟醚次之，异氟醚对血小板聚集无明显影响。其机制可能与氟烷和安氟醚通过抑制血小板上血栓素Ａ２受体的亲和力，降低ＡＤＰ和Ｅ诱导的血小板ＴＸＢ２的生成有关。     

吸入麻醉药对兔肾交感神经活动的影响

目的比较吸入麻醉药对交感神经活动和血液动力学的影响。方法18只兔被随机分为三组:安氟醚组、异氟醚组和地氟醚组。兔麻醉、肌松和人工通气后,暴露肾交感神经并记录其电生理活动。分别吸入呼气末浓度为0.8%、1.6%、2.4%、3.2%安氟醚,0.6%、1.2%、1.8%、2.4%异氟醚,或3.0%、6.0%、9.0%、12.0%地氟醚。结果交感神经活动在兔吸入2.4%安氟醚、0.6%异氟醚和6.0%地氟醚时分别增加到44%、36%和32%,当进一步增加吸入麻醉药的浓度则抑制肾交感神经活动。血压随着吸入麻醉药浓度的增加不断下降而心率除了2.4%异氟醚诱发心率减慢外无明显变化。结论安氟醚、异氟醚和地氟醚具有双向作用,低浓度兴奋交感神经,高浓度抑制交感神经活动和降低血压。     

七氟醚 异氟醚和安氟醚对离体兔胸主动脉环收缩功能的影响

目的：比较吸入麻醉药七氟醚、异氟醚和安氟醚对离体兔胸主动清脉环收缩功能的影响。方法：将取自２４只新西兰白兔的离体胸主动脉环随机分为七氟醚、异氟醚、安氟醚三组。衔用ＰＥ产生主动张力,稳定后分别吹入上述三种吸入麻醉药七氟醚记录不同浓度时的血管张力。结果：与基础值（麻醉药浓度为零时）相比,血管张力在三种吸入麻醉药２为１．０、１．５、２．０ＭＡＣ时均降低（Ｐ值分别小于０．０５、０．０５、０．０１）。安氟醚     

The blood/gas solubilities of sevoflurane, isoflurane, halothane, and serum constituent concentrations in neonates and adults

To determine the effect of prematurity on the solubility of volatile anesthetics in blood, the authors measured the blood/gas partition coefficients of sevoflurane, isoflurane, and halothane and the serum concentrations of albumin, globulin, cholesterol, and triglycerides in umbilical venous blood from ten preterm and eight full-term neonates and in venous blood from eight fasting adult volunteers. The authors found that the blood/gas partition coefficient of sevoflurane did not differ significantly among the three age groups. The partition coefficients of isoflurane and halothane in preterm neonates did not differ significantly from those in full-term neonates. However, the partition coefficients of both anesthetics in neonates were significantly less than those in adults. The blood/gas partition coefficients of the three volatile anesthetics in preterm neonates did not change significantly with gestational age. The blood/gas partition coefficients of sevoflurane, isoflurane and halothane for all three age groups combined correlated only with the serum concentration of cholesterol. The authors conclude that the blood/gas partition coefficients of isoflurane, halothane, and sevoflurane in preterm neonates are similar to those in full term neonates and that gestational age does not significantly affect the blood/gas solubility.     

Age and solubility of volatile anesthetics in blood

The more rapid rate of rise of alveolar anesthetic partial pressure in children compared with adults may be explained in part by an increasing solubility of volatile anesthetics in blood with age. To investigate this possibility, the authors measured the blood-gas partition coefficients of isoflurane, enflurane, halothane, and methoxyflurane in four groups of fasting subjects: 10 full-term newborns (at delivery), 11 children (3-7 years old), 11 adults (20-40 years old), and 10 elderly adults (75-85 years old). The blood-gas partition coefficients were greatest in adults: isoflurane 1.46, enflurane 2.07, halothane 2.65, and methoxyflurane 16.0; and least in newborns: 1.19, 1.78, 2.14, 13.3, respectively. The blood-gas partition coefficients in children (1.28, 1.78, 2.39, 15.0, respectively), which were intermediate between those in newborns (P less than 0.005) and those in adults (P less than 0.005), were not significantly different from those in elderly adults (1.29, 1.79, 2.41, 15.0, respectively). The blood-gas partition coefficients of both isoflurane and enflurane correlated directly with the serum albumin and triglyceride concentrations; that of halothane correlated directly with the serum cholesterol, albumin, triglyceride, and globulin concentrations; and that of methoxyflurane correlated directly with the serum cholesterol, albumin, and globulin concentrations. The authors conclude that age significantly affects blood-gas partition coefficients, and the lower blood-gas partition coefficients in children explain in part the more rapid rise of alveolar anesthetic partial pressure in this age group.     

Age and the solubility of volatile anesthetics in ovine tissues

To determine the effect of age on the solubility of volatile anesthetics in tissues, we measured the blood/gas and tissue/gas partition coefficients of isoflurane, enflurane, halothane, and methoxyflurane in vitro at 37 degrees C in newborn lambs and postpartum adult sheep. The tissue specimens examined were brain, heart, liver, kidney, muscle, and fat. Hematocrit and serum concentrations of albumin, globulin, cholesterol, and triglycerides were measured. The blood/gas partition coefficients, hematocrit, and the serum concentrations of albumin, globulin, cholesterol, and triglycerides in the newborn lambs did not differ from those in the adult sheep. The tissue/blood partition coefficients [the ratio of (tissue/gas)/(blood/gas)] in newborn lambs were 28% [mean value for the four anesthetics] less than those in the adults. The tissue/blood partition coefficients for enflurane and methoxyflurane in newborn tissues were significantly less (P less than 0.05) than those for halothane and isoflurane. We conclude that the blood/gas partition coefficients in sheep do not change significantly with age, and that the time required for equilibration of volatile anesthetics (particularly enflurane and methoxyflurane) in newborn tissues is probably less than in adult sheep.     

Minimum alveolar anesthetic concentration of volatile anesthetics in normal and cardiomyopathic hamsters

Minimum alveolar anesthetic concentrations (MAC) values of volatile anesthetics in cardiovascular diseases remain unknown. We determined MAC values of volatile anesthetics in spontaneously breathing normal and cardiomyopathic hamsters exposed to increasing (0.1%-0.3% steps) concentrations of halothane, isoflurane, sevoflurane, or desflurane (n = 30 in each group) using the tail-clamp technique. MAC values and their 95% confidence interval were calculated using logistic regression. In normal hamsters, inspired MAC values were: halothane 1.15% (1.10%-1.20%), isoflurane 1.62% (1.54%-1.69%), sevoflurane 2.31% (2.22%-2.40%), and desflurane 7.48% (7.30%-7.67%). In cardiomyopathic hamsters, they were: halothane 0.89% (0.83%-0.95%), isoflurane 1.39% (1.30%-1.47%), sevoflurane 2.00% (1.85%-2.15%), and desflurane 6.97% (6.77%-7.17%). Thus, MAC values of halothane, isoflurane, sevoflurane, and desflurane were reduced by 23% (P < 0.05), 14% (P < 0.05), 13% (P < 0.05), and 7% (P < 0.05), respectively in cardiomyopathic hamsters. IMPLICATIONS: Minimum alveolar anesthetic concentrations of volatile anesthetics were significantly lower in cardiomyopathic hamsters than in normal hamsters.     

Effects of Volatile Anesthetics on Atrial and AV Nodal Electrophysiological Properties in Guinea Pig Isolated Perfused Heart

Background: Knowledge of the anesthetic effects on atrial and atrioventricular (AV) nodal electrophysiologic properties is fundamental to understand the modulatory role of anesthetics on the pathogenesis of supraventricular tachycardias, and to individualize the perioperative management of patients with supraventricular tachycardias or AV nodal conduction disturbances. Therefore the authors studied the effects of three commonly used volatile anesthetics on the electrophysiologic properties of the atrium and AV node.

Methods: The concentration-dependent electrophysiologic effects of halothane, isoflurane, and desflurane (0 - 2 minimum alveolar concentration [MAC]) were studied in guinea pig Langendorff-perfused hearts fit with instruments to simultaneously measure atrial and AV nodal conduction times and atrial monophasic action potential duration. Atrial and AV nodal effective refractory periods were measured simultaneously using a computer-assisted premature stimulation protocol. The concentrations of anesthetics in the gas phase were monitor by an infrared gas analyzer.

Results: Volatile anesthetics caused markedly different concentration-dependent effects on atrial conduction, repolarization, and refractoriness, and on AV nodal function. At equianesthetic concentrations, halothane depressed atrial conduction the most, whereas desflurane caused the greatest shortening of atrial monophasic action potential duration. Halothane had no significant effect on atrial refractoriness, whereas at 2 MAC desflurane significantly shortened and isoflurane significantly prolonged atrial effective refractory periods by 18.1 +/- 13.5% and 13.2 +/- 14.7%, respectively. On an equi-MAC basis, the rank order of potency for the anesthetics to prolong AV nodal conduction time and AV nodal ERP was halothane > desflurane > isoflurane.     

A second-generation blood substitute (perflubron emulsion) increases the blood solubility of modern volatile anesthetics in vitro

Perfluorocarbon-based emulsions increase the blood solubility of isoflurane, enflurane, and halothane, with a maximal effect reported for the less soluble isoflurane. Current volatile anesthetics are less soluble and may be more affected by this phenomenon. Perflubron (Oxygent(TM)) is a perfluorocarbon-based emulsion in late-stage clinical testing in surgical patients for use as a temporary oxygen carrier. We tested the hypothesis that perflubron increases the solubility of isoflurane, sevoflurane, and desflurane, as reflected by their blood/gas partition coefficient (lambda(Bl:g)). Fresh whole-blood samples were drawn from eight volunteers and mixed with perflubron to obtain concentrations of 1.2%, 1.8%, and 3.6% by volume (equivalent to in vivo doses of 1.8 to 5.4 g/kg, which represent up to twice the intended clinical dose range). By using the double-extraction method, we demonstrated increased lambda(Bl:g) for isoflurane, sevoflurane, and desflurane. However, the solubility in blood does not really change, because volatile anesthetics are actually partitioning into perflubron. Increasing the amount of emulsion in the blood consequently increases the amount of gas carried, as reflected by the measured linear correlation between the lambda(Bl:g) values of all three volatile anesthetics and perflubron doses. Even though the increase ranges from 0.9 (desflurane) to 2.6 (sevoflurane) times the normal value, the apparent lack of clinical implications in current trials with perflubron may trigger further in vivo experiments. IMPLICATIONS:Perflubron increases the in vitro solubility of volatile anesthetics when present in the blood at clinically relevant concentrations. Volatile anesthetics actually partition into the emulsion, but the solubility in the blood does not change. Further studies are needed to assess whether perflubron will affect the pharmacokinetics of volatile anesthetics in vivo.     

Effects of anaesthesia and surgery on the solubility of volatile anaesthetics in blood

To determine the effects of anaesthesia and surgery on the solubility of volatile anaesthetics in blood, we measured the blood/gas partition coefficients of enflurane, halothane, isoflurane, and methoxyflurane in vitro in blood obtained from six healthy unpremedicated adults at three different times during isoflurane anaesthesia: awake; 20 minutes after induction of anaesthesia, but before surgical incision; and, 90 minutes after surgical incision. The blood/gas partition coefficients of the four volatile anaesthetics decreased significantly after induction of anaesthesia and after surgical incision (p less than 0.05). Values for haematocrit and the serum concentrations of albumin, globulin, and cholesterol decreased parallel to the decrease in blood/gas partition coefficients.     

Influence of desflurane,isoflurane and halothane on regional tissue perfusion in dogs

The actions of desflurane, isoflurane and halothane on regional tissue perfusion were studied using radioactive microspheres in dogs chronically instrumented for measurement of arterial and left ventricular pressure, global (left ventricular dP/dtmax) and regional (percent segment shortening) contractile function, and diastolic coronary blood flow velocity. Systemic and coronary haemodynamics and regional tissue perfusion were measured in the conscious state and during anaesthesia with equihypotensive concentrations of desflurane, isoflurane, and halothane. All three volatile anaesthetics (P < 0.05) increased heart rate and decreased mean arterial pressure, left ventricular systolic pressure, and left ventricular dP/dtmax Myocardial perfusion was unchanged in subendocardial midmyocardial, and subepicardial regions by the administration of either dose of desflurane. No redistribution of intramyocardial blood flow (endo/epi ratio) was observed during desflurane anaesthesia. Although regional myocardial perfusion was reduced (P < 0.05) in a dose-related fashion by halothane and by isoflurane at high concentrations, redistribution of intramyocardial blood flow was not observed during halothane or isoflurane anaesthesia. All three volatile anaesthetics reduced blood flow to the renal cortex, but only desflurane produced a decrease in renal cortical vascular resistance. Hepatic blood flow decreased in response to halothane but not desflurane or isoflurane. Concomitant decreases in hepatic resistance were observed during administration of desflurane and isoflurane. Dose-related decreases in intestinal and skeletal muscle blood flow were observed during halothane and isoflurane but not desflurane anaesthesia. The results suggest that desflurane maintains myocardial, hepatic, intestinal, and skeletal muscle blood flow while halothane and isoflurane decrease regional tissue perfusion in these vascular beds to varying degrees during systemic hypotension in the chronically instrumented dog.