剖胸术与肺通气功能——气道压、阻力和顺应性改变及相互效应

本文探讨麻醉下肺通气功能的不良影响在剖胸术中及术后的演变。30例剖胸手术病人用Engstrǒm Erica全自动微型电脑信息处理人工呼吸机通气和观察。结果表明,开胸后胸壁的限制作用丧失,顺应性改善;但胸腔负压消失致胸内小气道萎陷,吸气阻力增加。二者作用结果,气道峰压显著升高,但气道平均压不变。说明前者与增大的气流阻力有关,而后者反映了克服弹性阻力的压力。提示分别了解气道蜂压和平均压有其独特意义。剖胸本身对解剖死腔和氧及二氧化碳代谢无重要影响。关胸后顺应性逐渐下降并低于开胸前水平,吸气阻力和气道峰压、平均压显著上升。应重视剖胸术后对肺通气功能的进一步影响。     

异丙托溴铵对全麻病人呼吸力学的影响

目的通过麻醉前吸入异丙托溴铵,观察其对气管插管及机械通气时呼吸力学指标的影响。方法49例择期上腹部手术病人随机分为两组,雾化吸入异丙托溴铵0.5 mg的观察组(27例)和雾化吸入生理盐水的对照组(22例),分别于插管后即刻、插管后10、30及60 min监测呼吸力学指标的变化。结果观察组的气道峰压、呼吸功、吸气阻力和呼气阻力与对照组相比明显降低,而观察组肺顺应性明显高于对照组(P<0.05)。随着时间的延长,两组病人的气道峰压、呼吸功、吸气阻力和呼气阻力在不同时间点有不同程度的上升趋势;顺应性在下降到某一数值后则不再随时间而变化(P<0.05)。结论麻醉前雾化吸入异丙托溴铵,可降低机械通气早期气道峰压、呼吸机所做的呼吸功、吸气阻力及呼气阻力,同时改善肺动态顺应性。     

自主呼吸时辅助呼气能补偿气管导管阻力

背景尽管辅助吸气在插管的自主呼吸病人很常见,但辅助呼气却少见报道。在自主呼吸时有效的呼气支持（expiratorysupport,ES）可用于抵消气管导管（endotrachealtube,ETT）的阻力。在这个研究中,我们测试了一个新系统的性能,这个系统用于在自主呼吸中既提供吸气支持（inspiratorysupport,IS）又提供呼气支持以减少气管导管的有效阻力。方法这个ES系统由一个通气阀门和一个电脑控制的气缸活塞组成,用于在呼气相把气体从呼吸回路抽出。这个活塞的运动与自主呼吸同步。我们在9例健康成年男性志愿者身上,比较在自主呼吸时,5mmID和8mmID两种导管的尖端和呼吸回路内的压力。通气模式设定在维持持续气道压在0cmH2O。比较用5mmIDETT通气时3种通气设置（无支持,单纯吸气支持,吸气支持＋呼气支持）。结果我们监测了呼吸回路压力（Paw）,导管尖端压力（Ptip）,呼吸气流。在无呼吸支持的5mmIDETT,Ptip在吸气时呈大幅度的负偏移而呼气时呈大幅度的正偏移。单纯的IS并不改善小气管导管的呼吸模式。但是Is＋ES却能使只。在呼气呈负压吸气呈正压,使5mmIDE]rr的只,。压力特征与8mmIDETT的相似。而且Is＋ES使5mmIDETT的呼吸模式与8mmIDETT的相似。结论通过这项对健康志愿者的研究表明,IS＋ES抵消通过5mmIDETT强加的气道阻力,产生与8mmIDETT相似的Ptip改变。     

高频喷射通气对吸入性损伤犬呼吸气流与气体交换的影响

目的观察犬吸入性损伤时呼吸气流对气体交换的影响。方法用三维粒子动态分析仪测定犬自主呼吸时吸气和呼气流速。将实验动物通入高压蒸气5秒后随机进行五种不同条件高频喷射通气,每种通气方式通气20分钟,并根据公式Re=Vrρ/η计算出雷诺数,同时采取动脉血标本,观察Pa-CO_2、PaO_2PIP的变化。结果①自主呼吸时吸气为层流,呼气可能为层流,也可能为涡流;②高频喷射通气(HFJV)时呼气和吸气均为涡流;③高频双向喷射通气(HFTJV)与HFJV相比,呼气流速显著增加(P<0.05),PaCO_2显著降低(P<0.05),呼气流速与PaCO_2呈负相关(r=-0.9216,P<0.05),同时吸气流速也有增加的趋势。结论 HFJV可维持吸入性损伤犬正常通气,其机制可能与涡流有关。HFTJV是在HFJV基础上增加了反向喷射气流,可以增进呼吸气体速度,促进CO_2排除。     

以气道阻(压)力判断Robertshaw双腔导管插管对位305例临床观察

目的 探讨以气道阻力判断Robertshaw双腔支气管导管插管深度及对位正确与否的可行性.方法 随机选择305例剖胸手术患者,静脉快速诱导后,经口腔插入Robertshaw左双腔支气管导管至遇阻力为止.如左、右单肺通气阻力均高,则在右侧单肺通气状态下,逐渐后退双腔支气管导管至气道阻力开始下降,在此导管深度继续后退1.5cm固定导管.如无病理因素,气道阻力在12～20cm H2O范围.观察左、右单肺通气时气道阻力;双肺通气后20min及单肺通气20min分别行动脉血气分析并比较;随机对其中100例应用纤维支气管镜观察导管对位状况.结果 肺部病变患者,患肺通气气道阻力比健侧肺通气时明显增高(P<0.01);食管纵隔病变患者,左肺通气时气道阻力比右肺通气时气道阻力增高(P<0.05);插管后纤维支气管镜检左、右侧导管开口距左肺上叶支气管开口及隆凸距离分别为(1.18±0.28)cm、(2.16±0.34)cm;305例患者双肺通气20min后健侧单肺通气20min后血气分析结果均在正常范围.结论 以气道阻力判断Robertshaw双腔支气管导管插管对位是否正确,方法简捷、实用可行,可供临床参考.     

不同通气方式对重度蒸汽吸入伤犬呼吸力学及气体交换的影响

目的　研究常规机械通气 (CMV)、高频喷射通气 (HFJV)和高频双向喷射通气 (HFTJV)对重度蒸汽吸入伤犬呼吸力学和气体交换的影响。　方法　 9只犬 ,重度蒸汽吸入性损伤 ,分别在上述三种条件下检测呼吸力学、循环和血气等各种参数。　结果　 ( 1)三种通气方式下呼吸系统总阻力 (Rrs)、肺阻力 (RL)均显著高于对照值 (P <0 .0 1) ,呼吸总顺应性 (Crs)、肺顺应性 (CL)均显著低于对照值 ( P <0 .0 5 ) ,但三者之间比较 ,Rrs、RL、Crs、CL 的变化差异均无显著性意义。 ( 2 )CMV和HFJV均引起CO2 潴留 ,HFTJV比HFJV显著增加CO2 排出 (VCO2 ,P <0 .0 1)。 ( 3)三种通气方式的功能残气量(FRC)和PaO2 均无明显变化。　结论　三种通气方式均能克服气道阻力辅助呼吸 ,但不能使伤后高气道阻力和低肺顺应性恢复正常。CMV的通气效率类似于HFJV ,而HFTJV的通气效率则优于HFJV。     

困难气道时两种经插管型喉罩引导气管插管方法的疗效比较

气管插管型喉罩通气道（ILMA）是一种为引导盲探气管插管而特殊设计的新型喉罩通气道。不仅具有普通型喉罩通气道（LMA）的特性,还可引导气管导管进行盲探插管。本文报道本院使用的两种经ILMA引导气管插管方法在处理困难气道的临床效果。     

吸气式脉冲爆震发动机反压传播规律研究

以汽油为燃料,空气为氧化剂,在内径为60mm的吸气式脉冲爆震发动机上进行了反压传播规律实验研究。测量了10~30Hz频率范围内进气道内的反传压力。实验结果表明,进气道内的反压峰值随着工作频率的增加而增加,两者基本呈线性关系。随着工作频率的增加,压力波动的时间占每个工作循环时间的比例增加。压力脉动比在20Hz时达到最大。建立了数值模型,采用小能量点火及温度梯度自适应方法,计算得到了反压的形成及传播特性。计算结果印证了反压是由于回传爆震引起的。将计算结果与实验结果进行了比较,结果表明两者符合地较好。      

双喷管差动式小推力测量装置的设计与分析

为了研究喷管型面对小推力火箭发动机推力性能的影响,设计并建设了双喷管差动式小推力测量装置及其附属设备。在测量装置中,基准喷管和待测喷管同轴反向设置,通过测量结构应变来直接测量两个喷管的推力差。对测量装置进行了简化模型理论分析,导出其灵敏系数理论公式。依据该公式进行关键参数设计,确定合理的灵敏系数,指导试验系统设计,以保证测量精度。验证性试验表明测量装置可以测量牛级推力差,标定曲线线性较好,以基准喷管推力作为比较对象,推力差的相对扩展不确定度为0.5%。推力差与基准喷管推力的比值越小,以基准喷管推力为比较对象的相对测量不确定度越小。测量装置可以用于小推力火箭发动机喷管性能分析及优化的试验研究。      

高频喷射通气对吸入性损伤犬呼吸气流与气体交换的影响

目的 观察犬吸入性损伤时呼吸气流对气体交换的影响。方法 用三维粒子动态分析仪测定犬自主呼吸时吸气和呼气流速。将实验动物通入高压蒸气５秒后随机进行五种不同条件高频喷射通气，每种通气方式通气２０分钟，并根据公式Ｒｅ＝Ｖｒｐ／η计算出雷诺数，同时采取动脉血标本，观察Ｐ２－ＣＯ２、ＰａＯ２、ＰＩＰ的变化。结果（１）自主呼吸时吸气为层流，呼气可有为层流，也可能为涡流；（２）高频喷射通气（ＨＦＪＶ）时呼气和吸     

Vasopressor hormone response following mesenteric traction during major abdominal surgery

Background : We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI₂) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia. Methods : In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGFlα (stabile metabolite of PGI₂), TXB₂ (stabile metabolite of thromboxane A₂) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection. Results : Following MT, arterial hypotension occurred along with a substantial PGI₂ release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF_1α (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P=0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB² (164 (87) vs. 58 (1) ng/L, P=0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P=0.001), AVP (41 ± (18) vs. 12 (7) ng/L, P=0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients. Conclusion : Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI₂ release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A₂, presumably contributing to hemodynamic stability within 30 min after MT.     

A Teaspoon Pump for Pumping Blood with High Hydraulic Efficiency and Low Hemolysis Potential

Abstract: Virtually all blood pumps contain some kind of rubbing, sliding, closely moving machinery surfaces that are exposed to the blood being pumped. These valves, internal bearings, magnetic bearing position sensors, and shaft seals cause most of the problems with blood pumps. The original teaspoon pump design prevented the rubbing, sliding machinery surfaces from contacting the blood. However, the hydraulic efficiency was low because the blood was able to "slip around" the rotating impeller so that the blood itself never rotated fast enough to develop adequate pressure. An improved teaspoon blood pump has been designed and tested and has shown acceptable hydraulic performance and low hemolysis potential. The new pump uses a nonrotating "swinging" hose as the pump impeller. The fluid enters the pump through the center of the swinging hose; therefore, there can be no fluid slip between the revolving blood and the revolving impeller. The new pump uses an impeller that is comparable to a flexible garden hose. If the free end of the hose were swung around in a circle like half of a jump rope, the fluid inside the hose would rotate and develop pressure even though the hose impeller itself did not "rotate"; therefore, no rotating shaft seal or internal bearings are required.     

Microspheres Based Detoxification System: A New Method in Convective Blood Purification

Abstract: A variety of protein-bound or hydrophobic substances, accumulating as a result of pathologic conditions such as exogenous or endogenous intoxications, are removed poorly by conventional detoxification methods because of low accessibility (hemodialysis), insufficient adsorption capabilities (hemosorption), low efficiency (peritoneal dialysis), or economic limitations (high-volume plasmapheresis). Combining advantages of existing methods with microspheric technology, a module-based system was designed. Major operating parameters of the latter can be modified to allow for adjustment to individual clinical situations. An extracorporeal blood circuit including a plasmafilter is combined with a secondary high-velocity plasma circuit driven by a centrifugal pump. Different microspheric adsorbers can be combined in one circuit or applied in sequence. Thus, a prolonged treatment can be tailored using specially designed selective adsorber materials. Comparing this system with existing methods (high-flux hemodialysis, molecular adsorbent recycling system), results from our in vitro studies and animal experiments demonstrate the superior efficiency of substance removal.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts

Background : Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far.
Methods : Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined.
Results : At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1±1.2% (mean±SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2±1.2%), sevoflurane (to 4.4±0.9%) or halothane (to 3.2±1.5%) (each P <0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics.
Conclusion : Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.     

Bariatric Surgery in Some "Central and East-European (former Eastern bloc)"Countries - Current Status and Prediction for the Next Millennium

Background: Obesity is increasing globallly, including in the formerly "Eastern Bloc" countries. Methods: A survey was made of obesity and bariatric surgery. Results: In the 8 East and Central European countries studied, with total population 300 million, roughly 43% of the population was overweight (BMI 25-30), 23% obese (BMI > 30), with about 15 million people morbidly obese (BMI > 40). From 0-10 morbidly obese individuals/100,000/year undergo bariatric surgery. Conclusion: Most countries were found to provide inadequate treatment for obesity.The majority of the morbidly obese are not treated effectively. However, health-care awareness of obesity and bariatric surgeons are slowly increasing.     

Is the recovery profile of mivacurium independent of the rate of decay of its plasma concentration in patients with normal plasma cholinesterase activity?

Background: The duration of action of muscle relaxants is poorly correlated to the rate of decay of their plasma concentration. The plasma concentration of mivacurium may rapidly decrease below its active concentration because of the extensive hydrolysis of mivacurium. By inflating a tourniquet on one upper limb for 3 min after the administration of atracurium, mivacurium or vecuronium, we studied the influence of the initial decline of their plasma concentration on their effect. Methods: In 50 patients anaesthetised with thiopental, isoflurane and fentanyl, the effect of bolus doses of 0.15 or 0.25 mg . kg^?1 mivacurium (MIV 15, MIV 25), 0.3 or 0.5 mg . kg^?1 atracurium (ATR 30, ATR 50) and 0.06 or 0.1 mg . kg^?1 vecuronium (VEC 06, VEC 10) were measured on both arms (evoked response of the adductor pollicis to train-of-four stimulation every 12 s), a tourniquet being applied on one arm just before and during 3 min after the muscle relaxant bolus. Results: Tourniquet inflation of 3 min almost abolished the neuromuscular effect of mivacurium. In the vecuronium groups and in the ATR 50 group, tourniquet inflation did not modify the maximum degree of depression of the twitch response. Also, the duration of action of vecuronium was unaffected by the tourniquet. In the ATR 30 group, times to return of the twitch response to 25% (duration 25%) and 75% (duration 75%) of control response were significantly shorter in the cuffed arm, 23 min vs 27 min, and 41 min vs 45 min, respectively. In the ATR 50 group, only duration 25% was significantly shorter in the cuffed arm (41 min vs 45 min). Conclusion: The results suggest that the rate of decline of the plasma concentration of mivacurium is so rapid, that a very low and almost clinically ineffective concentration is present as soon as 3 min after its administration. The results also indicate that the recovery from a mivacurium-induced neuromuscular blockade is not influenced by the rate of decay of its plasma concentration in patients with genotypically normal plasma cholinesterase.     

Membranes in Artificial Organs

Abstract: Membrane processes play a pivotal and enabling role in modern replacement therapy for acute and chronic organ failure and in the management of immunologic diseases. In fact, virtually all contemporary extracorporeal blood purification methods employ membrane devices, and the next generation of artificial organs and tissue engineering therapies are almost certain to be similarly grounded in membrane technology. In this short essay, we comment on the similarities and differences among synthetic membranes and their natural counterparts and also provide a critical overview of the demographics and technology of hemodialysis, hemofiltration, apheresis, oxygenation, and emerging membrane technologies and applications.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.     

Synergistic interaction between the effects of propofol and midazolam with fentanyl on phrenic nerve activity in rabbits

Background: It has been shown that the depressive effects of both propofol and midazolam on consciousness are synergistic with opioids, but the nature of their interactions on other physiological systems, e. g. respiration, has not been fully investigated. The present study examined the effect of propofol and midazolam alone and in combination with fentanyl on phrenic nerve activity (PNA) and whether such interactions are additive or synergistic. Methods: PNA was recorded in 27 anaesthetised and artificially ventilated rabbits. In three groups, propofol, fentanyl and midazolam were administered intravenously in incremental doses to construct dose-response curves for the depressant effects of each one on PNA. In another two groups, the effect of pretreatment with either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. on the effects of propofol and fentanyl respectively on PNA were studied. Results: Propofol and fentanyl caused a dose-dependent depression of PNA with complete abolition at the highest total doses of 16 mg · kg^?1 i. v. and 32 μg · kg^?1 i. v., respectively. In contrast, midazolam in incremental doses to a total of 0.8 mg · kg^?1 reduced mean PNA by 63%, but approximately 12% of PNA remained at a total dose as high as 6.4 mg · kg^?1. The mean ED₅₀s, calculated from dose-response curves, were 5.4 mg · kg^?1, 3.9 μg · kg^?1 and 0.4 mg · kg^?1 for propofol, fentanyl and midazolam, respectively. Initial doses of either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. acted synergistically with subsequent doses of either propofol or fentanyl to abolish PNA at total doses of 8 mg · kg^?1 and 8 μg · kg^?1, respectively. Conclusion: Fentanyl has a synergistic interaction with both propofol and midazolam on PNA and hence potentially on respiration.