红细胞停搏液的心肌保护作用及对细胞间粘附分子-1表达的影响

目的：研究红细胞停搏液的心肌保护作用及其对细胞间粘附分子－1表达的影响。方法：应用滤器去除血液中的白细胞和血小板，配制红细胞停搏液，并应用Langendorff离体心模型，测定心率（HR）、左室收缩压峰值（LVSP）、左室舒张末压（LVEDP）、左室内压最大小升速率（dp/dtmax）、冠脉流量（CF）、肌酸激酶（CK）、电镜下观察组织结构的变化，用免疫组化方法观察粘附分子（ICAM－1）的表达情况。结果：在HR、LVSP、dp/dtmax、CF的恢复率、组织显微结构和ICAM－1表达方法，红细胞停搏液组优于全血及去白细胞停搏液组（P＜0．05）。结论：红细胞停搏液较全血停搏液和去白细胞停搏液具有更好的心肌保护作用。     

温血诱停及再灌注对缺氧未成熟心肌保护的实验研究

目的　探讨温血诱导心脏停跳及复跳前再灌注对缺氧未成熟心肌的保护作用。方法　构建缺氧幼兔模型 ,观察比较温血诱导心脏停跳及复跳前再灌注 (实验组 )与冷晶体停跳液灌注 (对照组 ) ,心肌丙二醛 (MDA)、超氧化物歧化酶 (SOD)及三磷酸腺苷 (ATP)含量 ,心肌含水量和心肌细胞超微结构的变化。结果　缺氧幼兔出现发绀 ,低氧血症和右室 / (左室 +室间隔 )比值 [RV/ (LV +S) ]增高等改变 ,与紫绀型先天性心脏病的病理生理改变相近。再灌注末心肌MDA、SOD、ATP含量分别为 :实验组( 32 6 39± 82 88)nmol/g、( 45 44± 4 76 )U/ 10 0mg、( 13 0 9± 1 5 0 ) μmol/g ;对照组 ( 5 37 88± 10 0 5 1)nmol/g、( 2 9 2 5± 5 40 )U/ 10 0mg、( 11 5 3± 2 17) μmol/g(P <0 0 1)。心肌含水量实验组 ( 5 9 95± 2 0 9) %、对照组 ( 79 77± 1 17) % (P <0 0 1)。实验组心肌细胞线粒体、细胞核等超微结构得到较好保护。结论　缺氧幼兔模型制作方法简单 ,可操作性和可重复性较强。温血诱导停跳及复跳前再灌注能减少缺血后未成熟心肌的氧自由基产生和再灌注损伤 ,对心肌能量代谢、超微结构等方面的保护效果较好。     

顺行灌注心脏不停跳法的心肌保护作用

目的　探讨顺行灌注心脏不停跳法心肌保护作用的效果。方法　选用 12～ 16周龄健康长耳白兔 3 0只 ,随机分为 3组 ,每组 10只。A组 (心脏不停跳组 ) :经主动脉持续灌流 3 2℃稀释血液 15 0min。B组 (冷血钾心脏停跳组 ) :在主动脉间断灌注 15℃血钾心停搏液 5 0ml ,将心脏置入 15℃生理盐水中 15 0min。C组 (微温血连续灌注心脏停跳组 ) :从主动脉持续灌注 3 2℃血钾心停搏液 15 0min。观察心功能、心肌酶、左心室心肌生化、氧自由基。结果　A组主动脉流量 (AF)、冠脉流量 (CF)、左室收缩压 (LVSP)和舒张末压 (LVEDP)的恢复率较B组和C组好 ,心肌组织三磷酸腺苷 (ATP)含量为 [(12 .17± 0 .69) μmol/g干重 ]、超氧化物歧化酶 (SOD)活性均高于B组 [ATP(8.5 2± 1.0 4) μmol/ g干重 ]和C组 [ATP (9.0 5± 1.0 4) μmol/ g干重 ] ,丙二醛 (MDA)、Na+ 、Ca2 +含量、冠脉流出液的乳酸盐 (LA)、心肌肌酸磷酸激酶 (CPK )和乳酸脱氢酶 (LDH)漏出率比B组和C组低 (P <0 .0 1) ;B组与C组比较 ,差异无显著性 (P >0 .0 5 )。结论　顺行灌注心脏不停跳法有良好的心肌保护作用 ,是一种安全、更接近生理状态的心肌保护方式     

逆行灌注心脏不停跳法对心肌的保护作用

目的　探讨逆行灌注心脏不停跳法心肌保护作用的效果。方法　用离体兔心工作模型 ,经冠状静脉窦逆行灌注 3 2℃稀释血液或血钾停搏液 12 0min。将 2 0只长耳大白兔随机分成 2组 ,每组 10只。A组 (心脏不停跳组 ) ,B组 (温血心停跳连续灌注液组 )。观察左室收缩压 (LVSP)和左室舒张末压 (LVEDP)、磷酸肌酸激酶 (CK )、左右心室三磷酸腺苷 (ATP)、丙二醛 (MDA)等。结果　A组的LVSP、LVEDP恢复率分别为 91.69%、111.3 1% ;ATP[(11.45± 0 .91)nmol/g干重 ]高于B组 (P <0 .0 5 ) ;MDA(2 .3 4± 0 .5 7) μmol/g和CK漏出率 (3 3 .69± 3 .0 9)IU /5mim .g干重低于B组 (P <0 .0 5 ) ;左右室心肌各项指标差异无显著性 (P >0 .0 5 )。结论　逆行灌注心脏不停跳法对左右心室均有良好保护作用 ,是一种安全有效的心肌保护方法。     

骨髓基质干细胞治疗兔缺血心肌的初步实验研究

目的通过建立兔自体骨髓移植模型,验证骨髓基质干细胞(MSCs)移植到缺血心肌后是否在心肌的微环境中可以向心肌细胞分化,探讨其对缺血心肌心功能的影响。方法将13只新西兰大白兔分为实验组(7只)和对照组(6只),实验组于心肌梗死前后缘上、中、下各3点分别注射被5溴-2脱氧尿苷(BrdU)标记的自体MSCs(3×106cells/30μl);对照组注射同等量的磷酸盐缓冲液(PBS)。移植4周后通过激光共聚焦显微镜验证移植后的MSCs是否向心肌细胞分化,并用心脏彩色超声心动图和多导生理记录仪测定缺血心肌的心功能。结果移植4周后,MSCs向心肌细胞分化,表达出α-肌小节肌动蛋白(-αsarcomeric actin)和存在于闰盘中的连接蛋白43(connexin 43),自体MSCs能够增加局部心肌组织中血管数量。实验组心肌左心室收缩功能明显比对照组增强[左心室射血分数(LVEF):0.51±0.07 vs.0.43±0.06,左心室侧壁运动幅度(LVLWMD):1.75±0.42mm vs.1.09±0.28mm,左心室收缩期室壁增厚率(LVΔT):0.19%±0.05%vs.0.11%±0.04%,左心室收缩压(LVSP):113.1±6.3 mmHg vs.99.5±5.1 mmHg,左心室舒张期末压(LVEDP):11.5±2.1 mmHg vs.14.3±3.1mmHg,左心室压力增高最大速率(+dp/dtmax):4 618.3±365.2mmHg/s vs.3 268.1±436.9 mmHg/s,左心室压力下降最大速率(-dp/dtmax):3 008.8±346.7mmHg/s vs.2 536.9±380.4 mmHg/s,P<0.05]。结论自体MSCs移植到兔缺血心肌后可以向心肌细胞分化,提高缺血心肌的心功能,对治疗心肌缺血具有较好的前景。     

冷血浆停搏液对幼兔未成熟心肌功能及结构的影响

目的 评价冷血浆停搏液对未成熟心肌结构及功能的影响。方法 选择生后17～26 d的新西兰白兔32只,分别灌注冷血浆停搏液(P组,n=16)或冷晶体停搏液(C组,n=16)。离体心脏连接Langendorff装置,灌注时在Krebs-Henseleit(K-H)液中持续通入95％O2+5％CO2,心脏复跳稳定10 min后灌注不同的停搏液。C组灌注冷st.Thomas停搏液,P组灌注冷血浆停搏液(血浆与St.Thomas停搏液按4:1比例配制,其中钾浓度与C组相同)。停跳30 min后重新灌注K-H液,观察心脏复跳时间,稳定10 min后测定复跳后心率、冠脉流量及心肌含水量,在光、电镜下观察心肌的形态结构。结果 P组再灌注心脏复跳后心率(129±5)次/min、冠脉流量(5.10±0.20)ml/L分别均高于C组(120±4)次/min、(3.50±0.50)ml/L;心肌含水量72.0％±2.0％低于C组77.0％±4.0％(P<0.05);光镜下P组心肌问质血管轻度扩张,血管周围轻度水肿;C组心肌细胞血管明显扩张,血管周围水肿明显,细胞间质可见水肿液。电镜下P组心肌细胞线粒体轻度肿胀,细胞核、细胞器基本正常;C组心肌细胞线粒体多高度肿胀,有空泡变性,嵴部分分散、断裂。结论冷血浆停搏液比冷晶体停搏液对未成熟心肌结构和功能的影响较小。     

腺苷停搏液对未成熟心肌的保护作用

目的　探讨腺苷加入停搏液对未成熟心肌的保护作用。方法　 0～ 2d的豚鼠 3 0只 ,随机分为 3组 ,每组 10只。低温组 :局部单纯低温 (15～ 17℃ ) ;Thomas组 :ThomasⅡ号停搏液灌注加低温 ;腺苷组 :腺苷高钾停搏液灌注加低温。平均全心停循环 90min ,再灌注 3 0min。观察诱导心脏停搏时间、冠脉流量恢复率 (CFR)、心肌含水量、超微结构、丙二醛 (MDA )和黄嘌呤氧化酶(XO)的变化。结果　腺苷组诱导心脏停搏时间 (4 .0± 1.1)s较Thomas组 (15 .6± 3 .7)s明显缩短 ;心肌MDA含量 (5 5 .2 6± 3 .3 4)低于Thomas组 (61.49± 3 .70 )和低温组 (64 .92± 3 .2 0 ) ;再灌注末心肌含水量 (77.17± 1.44 ) %少于Thomas组 (79.5 4± 2 .49) %和低温组 (79.48± 1.78) % ;CFR(73 .72± 6.74)高于Thomas组 (67.85± 4.83 )和低温组 (63 .5 5± 4.70 ) ;心肌超微结构改变较轻。 3组间心肌XO差异无显著性 (P >0 .0 5 )。结论　腺苷加入停搏液中对未成熟心肌有保护作用。     

钙依赖性酪氨酸激酶在风湿性心脏病心肌纤维化中的作用

目的观察钙依赖性酪氨酸激酶2(Pyk2)在风湿性心脏病患者中的表达,与心肌纤维化指标的关系及临床意义。方法30例风湿性心脏病患者心肌组织(实验组)和6例正常心肌标本(对照组)行M asson染色测定心肌蓝色胶原灰度值,采用放射免疫法检测血清透明质酸(HA)、层粘连蛋白(LN)和Ⅳ型胶原(IV-C)含量,并通过免疫组织化学法和逆转录-聚合酶链反应(RT-PCR)法观察Pyk2蛋白和信使核糖核酸(mRNA)的表达,以及Pyk2表达与心肌纤维化指标的相关性。结果实验组血清HA,LN和IV-C均较对照组高(174.95±76.14μg/L vs.70.06±15.63μg/L,153.86±20.72μg/L vs.90.01±14.11μg/L,95.26±7.66μg/L vs.63.21±10.62μg/L;P=0.003,0.013,0.035)。实验组Pyk2蛋白吸光度和Pyk2 mRNA/磷酸甘油醛脱氢酶(GAPDH)明显高于对照组(0.325±0.032vs.0.106±0.013,0.870±0.085 vs.0.573±0.042;P=0.048,0.006)。心肌Pyk2蛋白表达与心肌纤维化指标HA、LN和IV-C含量呈明显正相关(r=0.611,0.743,0.829,P<0.01),心肌Pyk2 mRNA表达与LN,IV-C含量呈正相关(r=0.794,0.766,P<0.05)。结论Pyk2可能通过增加风湿性心脏病心肌胶原合成在风湿性心脏病心肌间质纤维化的发生、发展进程中发挥重要作用。     

含不同浓度乳化异氟醚的停跳液对大鼠离体心脏缺血再灌注损伤的影响

目的 探讨含不同浓度乳化异氟醚的停跳液对大鼠离体心脏缺血再灌注损伤的影响.方法 清洁级雄性成年SD大鼠,体重180～250 g,建立Langendorff离体心脏灌注模型,取模型制备成功的56个心脏随机分为7组(n=8):St.Thomas停跳液组(C组)和含不同浓度乳化异氟醚的停跳液组(E1组～E6组).K-H液平衡灌注20 min后,C组用4℃ St.Thomas停跳液20 ml使心脏停搏45 min,K-H 液再灌注60 min,E1组～E6组分别用含乳化异氟醚0.28、0.56、1.12、1.68、2.24和2.80 mmol/L的4℃St.Thomas停跳液20 ml使心脏停搏45 min,K-H液再灌注60 min.于平衡灌注末、再灌注20、40、60 min 时记录HR、左心室发展压(LVDP)、左心室舒张末压(LVEDP)和左心室压力最大上升速率(+dp/dtmax),并收集冠脉流出液1.5 ml,测定乳酸脱氢酶(LDH)、超氧化物歧化酶(SOD)的活性和肌钙蛋白I(cTnI)浓度.于再灌注60 min时取心肌组织,计算心肌梗死面积.结果 与C组比较,E4组HR、LVDP、+dp/dtmax和SOD活性升高,LVEDP、LDH的活性和cTnI浓度降低,心肌梗死面积减小,E5组和E6组HR、LVDP、+dp/dtmax和SOD活性降低,LVEDP、LDH活性和cTnI浓度升高,心肌梗死面积增加(P<0.05),E1组～E3组上述指标差异无统计学意义(P>0.05).与E4组比较,其余含不同浓度乳化异氟醚的停跳液组HR、LVDP、+dpldt～和SOD活性降低,LVEDP、LDH活性和cTnI浓度升高,心肌梗死面积增加(P<0.05).结论 含1.68 mmol/L乳化异氟醚的停跳液可减轻大鼠离体心脏缺血再灌注损伤.     

腺苷预处理对心脏直视手术心肌保护作用的临床研究

目的　探讨腺苷预处理对心脏直视手术的心肌保护效果。方法　将 30例择期心脏瓣膜置换术患者随机分成治疗组和对照组 ,治疗组在开心术前实施腺苷预处理。观察血清心肌肌钙蛋白T(cTnT)、磷酸肌酸激酶同工酶 (CK MB)、血浆丙二醛 (MDA)、心肌三磷酸腺苷 (ATP)、能量储备(EC)及心肌超微结构 (线粒体计分 )的变化。结果　主动脉开放后 30min ,治疗组cTnT为 ( 0 .42±0 .1 8) μg/L、CK MB为 ( 35.42± 1 5.87)U/L、MDA为 ( 4 .2 8± 0 .35)mmol/L升高值均明显低于对照组 [( 1 .1 6± 0 .32 ) μg/L、( 56.2 6± 1 6.36)U//L、( 6.37± 2 .46)nmol/L(P <0 .0 5) ];治疗组ATP含量( 1 5.86± 3.51 ) μmol/g干重和EC值 0 .4857± 0 .0 578均明显高于对照组 [( 6.2 5± 2 .79) μmol/g干重、0 .2 992± 0 .0 4 1 9(P <0 .0 1 ) ];治疗组线粒体计分 0 .860 2± 0 .2 381明显低于对照组 2 .740 6±0 .9792 ,(P <0 .0 1 )。结论　腺苷预处理对心脏具有明显的保护作用     

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.