七氟醚对罗库溴铵肌松效应的影响

目的 观察七氟醚对罗库溴铵肌松作用的影响.方法 成人全麻手术患者60例随机均分为三组.每组20例.Ⅰ组丙泊酚静脉麻醉,Ⅱ组吸入七氟醚(1 MAC)15 min,Ⅲ组吸入七氟醚(1 MAC)45 min.在麻醉平稳(Ⅱ、Ⅲ组在呼气末七氟醚浓度稳定在1 MAC)后静脉注射罗库溴铵0.6 mg/kg,记录TOFr的变化.结果 Ⅱ、Ⅲ组罗库溴铵的起效时间分别为97.60 s和94.50 s,明显短于Ⅰ组的119.90 s(P<0.05);Ⅱ和Ⅲ组完全肌松时间(T1消失)明显长于Ⅰ组(32.7 min和44,6 min vs.21.3 min)(P<0.05),Ⅲ组明显长于Ⅱ组(P<0.05);TOF的T2～T4出现的时间及TOFr恢复到25%、50%和75%的时间,Ⅱ、Ⅲ组均长于Ⅰ组,且Ⅲ组长于Ⅱ组(P<0.05).结论 持续吸入1 MAC七氟醚能随吸人时间延长而增强罗库溴铵的神经肌肉阻滞效应.     

不同浓度异氟醚对罗库溴铵肌松作用的影响

目的 观察不同浓度异氟醚对罗库溴铵肌松作用的影响。方法 60例ASA Ⅰ-Ⅱ择期手术患者,随机分为3组,每组20例。组Ⅰ静脉注射罗库溴铵0.6 mg·kg-1;组Ⅱ吸入0.6％异氟醚后静脉注入罗库溴铵0.6mg·kg-1;组Ⅲ吸入1.2％异氟醚后从静脉注入罗库溴铵0.6mg·kg-1。分别记录各组注药后肌松作用的起效时间、作用时间及T1恢复时间。结果 与组Ⅰ相比,组Ⅱ、Ⅲ起效时间明显缩短(P<0.05),TOF无反应期明显延长(P<0.01),T1恢复25％、50％、90％时间明显延长(P<0.01),且组Ⅲ较组Ⅱ延长(P<0.05),恢复指数明显延长,且组Ⅲ较组Ⅱ延长(P<0.05)。结论 吸人异氟醚能明显缩短罗库溴铵起效时间,延长罗库溴铵作用时间,临床合并使用时应注意减少用量。     

七氟醚对罗库溴铵肌松效应的影响

目的 研究吸入不同浓度的七氟醚对不同剂量的罗库溴铵肌松效应的影响.方法 90例择期手术患者随机均分为六组.记录各组静注罗库溴铵后其起效时间、四个成串刺激(TOF)无反应时间、T1 25%恢复时间、T1 75%恢复时间及恢复指数(T1 25%恢复到75%的时间).结果 静注等效剂量的罗库溴铵Ⅲ组与Ⅰ组、Ⅳ组与Ⅱ组比较,起效时间差异无统计学意义.而静注等效剂量的Ⅴ组与Ⅰ组、Ⅵ组与Ⅱ组比较,起效时间明显缩短(P＜0.05);在无反应时间、T1 25%恢复时间、T1 75%恢复时间及恢复指数上,复合吸入七氟醚的Ⅲ到Ⅵ组较注入等效剂量的罗库溴铵Ⅰ组与Ⅱ组比较均有明显的延长(P＜0.05或P＜0.01);Ⅱ组与Ⅲ组之间以及Ⅳ组与Ⅴ组之间罗库溴铵的肌松维持时间差异无统计学意义.结论 七氟醚能明显延长罗库溴铵的作用时间,有时间依赖及剂量依赖趋势.     

罗库溴铵对老年病人的药效动力学影响

目的 研究罗库溴铵对老年病人的肌松效应。方法 94例ASA Ⅰ～Ⅱ级的病人按年龄分为4组,Ⅰ组为对照组(28例,32～59岁),Ⅱ组(29例,60～69岁),Ⅲ组(27例,70～89岁)和Ⅳ组(10例,90～97岁)。四组病人均于全麻诱导时静注罗库溴铵0.6mg/kg,并进行四个成串刺激(TOF)肌松监测。术中持续静注罗库溴铵,用注射泵调控给药剂量,T_1维持10％～20％至手术结束。记录罗库溴铵起效时间、T_1为零时间、首次给药后T_110％恢复时间、停药后T_125％恢复时间以及每30min罗库溴铵用量。结果 (1)Ⅰ组病人罗库溴铵起效时间明显比其余三组长(P<0.01),Ⅳ组病人肌松起效时间快于Ⅱ组和Ⅲ组(P<0.01)。(2)Ⅰ组病人T_1为零时间明显比其余3组病人长(P<0.01),Ⅱ、Ⅲ组T_1为零时间相近(P>0.05),Ⅳ组病人则短于Ⅱ组和Ⅲ组(P<0.01)。(3)Ⅰ组和Ⅱ组首次给药后T_110％恢复时间和停药后T_125％恢复时间显著快于Ⅲ组和Ⅳ组(P<0.01)。(4)不同年龄组罗库溴铵用量不同,随年龄增加而减少(P<0.01)。结论 随着年龄的增长,尤其在高龄病人罗库溴铵起效时间,达最大效能时间增快、维持用量减少和肌松持续时间延长。     

肝功能不全门脉高压病人罗库溴铵的肌松效应

目的 观察罗库溴铵在肝功能不全门脉高压病人中的肌松效应。方法 70例ASA I-Ⅱ级择期行上腹部手术的病人分为两组:门脉高压组(M组,n=36),对照组(C组,n=34),其中门脉高压组肝功能均属Child-Turcottee分级法Ⅱ级,对照组肝功能正常。两组病人麻醉诱导均为静脉注射咪唑安定0.02 mg·kg-1、异丙酚1.0 mg·kg-1、芬太尼5μg·kg-1和罗库溴铵0.6 mg·kg-1,同时进行肌松监测。麻醉维持采用吸入异氟烷及间断静脉注射芬太尼,罗库溴铵微量泵持续静注维持肌松,维持T1在10％-20％直至手术结束。记录罗库溴铵起效时间,TOF无反应时间,首次给药后,T110％恢复时间,停药后T125％恢复时间,恢复指数以及每30 min罗库溴铵维持用量。结果 M组病人肌松药起效时间、TOF完全阻断时间、首次给药后,T110％恢复时间、停药后T125％恢复时间及恢复指数比C组病人延长(P<0.01)。M组病人持续输注罗库溴铵用量明显小于C组病人(P<0.01)。结论 肝功能不全的门脉高压病人罗库溴铵起效、维持时间和肌松恢复时间明显延长,维持用量明显减少。     

罗库溴铵预注和麻黄碱预处理对小儿罗库溴铵肌松起效的影响

目的 观察小儿在罗库溴铵预注、麻黄碱预处理和罗库溴铵预注复合麻黄碱预处理对罗库溴铵起效时间、插管条件和肌松时效的影响.方法 选择全麻下行择期手术的患儿80例,ASA Ⅰ或Ⅱ级,随机均分为四组.在麻醉诱导前预先静注:Ⅰ组生理盐水O.5 ml,Ⅱ组罗库溴铵0.06 mg/kg,Ⅲ组麻黄碱70 μg/kg,Ⅳ组罗库溴铵0.06 mg/kg和麻黄碱70 μg/kg.预注和预处理4min后,Ⅰ、Ⅲ组静注罗库溴铵0.6 mg/kg,Ⅱ、Ⅳ组静注罗库溴铵0.54 mg/kg.待四个成串刺激(TOF)第1个颤搐反应高度(Th)达最大阻滞程度后行气管插管.记录肌颤搐抑制75%、90%和达最大阻滞程度的时间,并评估气管插管条件,同时观察HR、BP变化.结果 Ⅰ、Ⅱ、Ⅲ、Ⅳ组的最大阻滞起效时间分别为(196±43)、(140±43)、(144±35)和(100±33)s,Ⅱ、Ⅲ、Ⅳ组的起效时间明显短于Ⅰ组(P＜0.05),Ⅳ组的起效时间较Ⅱ、Ⅲ组短(P＜0.05).各组气管插管条件均达到6～9分,优良率100%.各组麻醉诱导期间均无明显的心血管不良反应.各组的临床肌松作用时间和恢复指数差异均无统计学意义.结论 罗库溴铵预注和麻黄碱预处理分别使用均能缩短小儿罗库溴铵的肌松起效时间,而两种方法复合使用可进一步加快肌松起效,但该方法对罗库溴铵的肌松时效无明显的影响.     

术中磁共振成像对持续泵注罗库溴铵肌松效应的影响

目的 观察神经外科手术术中磁共振成像(iMRI)对罗库溴铵肌松效应的影响.方法 采用前瞻、随机、对照研究.择期行开颅手术的患者30例,ASA Ⅰ或Ⅱ级,随机均分为两组:iMRI组(M组)和非iMRI组(C组).采用加速度仪四个成串刺激(TOF)监测肌松.两组采用相同的保温措施.麻醉诱导后给予罗库溴铵0.6 mg/kg,T1为0时静脉泵注罗库溴铵0.3～0.7Mg·kg-1·h-1,维持T1在0～5%.关闭硬脑膜时停止泵注罗库溴铵.记录T1恢复25%、TOF恢复25%、75%、90%的时间,停止泵注罗库溴铵至手术结束时间,罗库溴铵用量等.结果 术中M组患者腋温逐渐升高,而C组逐渐降低.手术时M组和C组腋温分别为(37.00±0.36)℃和(35.53±0.74)℃.M组TOF 25%、TOF 75%、TOF 90%时间显著短于C组(P<0.05或P<0.01).结论 iMRI可使患者体温升高,加快罗库溴铵TOF 25%的恢复,缩短临床及体内作用时间,但对于恢复指数无显著影响.     

七氟醚对不同性别患者罗库溴铵肌松作用的影响

目的 比较罗库溴铵肌松效应的性别差异和七氟醚对不同性别患者罗库溴铵肌松增效作用.方法 择期手术患者120例(男:女为1:1),年龄20～60岁.ASA Ⅰ或Ⅱ级,按性别随机分为丙泊酚组和七氟醚组:女性丙泊酚组(PF组).男性丙泊酚组(PM组),女性七氟醚组(SF组),男性七氟醚组(SM组),每组30例.所有患者静脉注射咪达唑仑、芬太尼和丙泊酚行麻醉诱导,意识消失后,置入喉罩,接麻醉机辅助通气并启动肌松监测.丙泊酚组静脉输注丙泊酚维持麻醉,设定血浆靶控浓度2～6 μg/ml,输注丙泊酚5 min后静脉注射罗库溴铵0.6 mg/kg,七氟醚组在呼气末七氟醚浓度稳定于1 MAC 5 min后静脉注射罗库溴铵0.6 mg/kg.记录肌松起效时间、完全肌松时间、T1恢复到25%和TOF恢复到25%的时间.结果 PM组较PF组起效时间长,完全肌松时间、T1恢复到25%和TOF恢复到25%的时间缩短(P＜0.05).SF组TOF恢复到25%的时间较PF组延长(P＜0.05),SM组较PM组起效时间缩短,完全肌松时间、T1恢复到25%和TOF恢复到25%的时间均延长(P＜0.05).SM组T1恢复到25%和TOF恢复到z5%的时间较SF组延长(P＜0.05).结论 女性罗库溴铵起效更快,作用时间长;而七氟醚对男性罗库溴铵的增效作用优于女性.     

地氟醚对罗库溴铵肌松效应的影响

目的研究地氟醚对罗库溴铵肌松效应的影响。方法成人全麻手术患者30例,随机分为3组静脉麻醉组(Ⅰ组)、吸入地氟醚(1MAC)15min组(Ⅱ组)和45min组(Ⅲ组)。Ⅰ组在麻醉平稳后,Ⅱ组和Ⅲ组分别在呼气末地氟醚浓度稳定15min和45min时静注罗库溴铵0.6mg·kg-1,用肌松监测仪监测TOF(四个成串刺激)的变化。结果Ⅱ组的T1和TOF比值起效时间(min)分别为1.3和0.8,与Ⅰ组2.2和1.5比较,明显缩短(P<0.05);临床肌松时间(T1值恢复至25％基础值的时间)3组分别为29.6,31.7和37.8min,Ⅲ组与Ⅰ组比较明显延长(P<0.05);T     

罗库溴铵和维库溴铵在终末期肾衰竭病人临床药效的比较

目的　比较罗库溴铵和维库溴铵在终末期肾衰竭病人中的肌松效应。方法　 2 5例ASAⅢ级行肾移植术病人随机分为罗库溴铵组 (R组 ,15例 )和维库溴铵组 (V组 ,10例 )。麻醉诱导后分别给予 2×ED95剂量的罗库溴铵 (0 6mg/kg)或维库溴铵 (0 1mg/kg)。术中当T1恢复至 2 5 %时 ,追加 0 5×ED95剂量的罗库溴铵 (0 15mg/kg)或维库溴铵 (0 0 2 5mg/kg)。末次剂量后 ,使肌张力自然恢复或给予新斯的明拮抗。结果　初量罗库溴铵的起效时间为 (1 98± 0 4 7)min ,明显短于维库溴铵的 (3 2 5±0 82 )min。初量和追加量的罗库溴铵的肌松维持时间分别为 (4 6 87± 14 6 0 )min和 (34 86± 15 5 7)min,与维库溴铵相似。两组应用拮抗药后 ,恢复指数均显著缩短。结论　对于终末期肾衰竭病人 ,罗库溴铵的起效快于维库溴铵 ,肌松作用维持时间和恢复指数与维库溴铵相似。     

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 comparison of the inhibitory effects of four volatile anaesthetics on the metabolism of chlorzoxazone, a substrate for CYP2E1, in rabbits

Background: Halothane inhibits in vitro and in vivo activity of cytochrome P-450 (CYP) 2E1. There are several fluorinated volatile anaesthetics besides halothane, and most of them are defluorinated by CYP2E1. It is unclear whether other fluorinated anaesthetics inhibit the in vivo activity of CYP2E1.
Methods: We compared the inhibitory effects of therapeutic concentrations of four inhalational anaesthetics, halothane, enflurane, isoflurane, and sevoflurane, on chlorzoxazone metabolism in rabbits receiving artificial ventilation.
Results: All four inhalational anaesthetics decreased arterial blood pressure and increased plasma chlorzoxazone concentration. However, no significant differences in the plasma chlorzoxazone concentration were found between the four anaesthetics. The estimated chlorzoxazone clearance increased after beginning inhalation with all four agents, but no significant difference in clearance was noted between agents.
Conclusions: At therapeutic concentrations, the in vivo inhibitory effect on chlorzoxazone metabolism was similar for all four inhalational anaesthetics examined, even though their chemical characteristics and extent of hepatic metabolism differ considerably.     

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.     

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.