变频振动在模拟微重力环境下对成骨细胞增殖和分化 的影响

目的观察变频振动在模拟微重力环境下对体外培养成骨细胞增殖和分化的影响。方法利用沿水平轴连续回转(30 r/min)细胞培养系统模拟微重力环境,应用电磁振动台将振动强度为0.5 g(g为加速度)在不同频率45 Hz、90 Hz、变频(5~90 Hz)振动应力作用于新生24 h大鼠颅盖骨成骨细胞,分别使用MTT比色法和碱性磷酸酶(ALP)活性测定了解成骨细胞的增殖和分化情况。结果模拟微重力环境可以抑制新生24 h大鼠颅盖骨成骨细胞的增殖和分化功能;90 Hz和5~90Hz变频振动促进模拟微重力环境成骨细胞的增殖功能(p0.01);45 Hz(p0.05)和5~90 Hz(p0.01)变频振动刺激对模拟微重力环境成骨细胞的分化功能具有一定的保护作用。结论在模拟微重力环境下机械振动对成骨细胞的增殖和分化功能具有保护作用,这为机械振动刺激防治微重力环境下骨丢失提供了理论和实验依据。     

雷尼酸锶对尾吊大鼠失重性骨质疏松的防治作用

目的观察雷尼酸锶(SR)对尾吊大鼠血清骨代谢指标、骨密度、骨生物力学的影响。方法选用3月龄雄性健康SD大鼠30只,随机分为5组:全程对照组(A组)、尾吊时服用SR组(B组)、尾吊后服用SR组(C组)、全程服用SR组(D组)、尾吊后对照组(E组),共8周(其中尾吊4周)。分别检测血清骨代谢指标,行骨密度检查及骨生物力学实验。结果尾吊后对照组碱性磷酸酶和骨钙素活性明显高于其余各组(P0.05)。骨密度、最大压缩载荷、最大三点弯曲载荷均比A组低,经过SR治疗后各组指标均有不同程度提高(P0.05),但尾吊后服用SR组和全程服用SR组效果相当且优于尾吊时服用SR组。结论雷尼酸锶对尾吊大鼠骨质疏松有防治作用。     

50 Hz 1.8 mT正弦交变电磁场通过促进骨形成抑制尾吊大鼠的骨量丢失

目的探究50 Hz 1.8 m T正弦交变电磁(sinusoidal electromagnetic fields,SEMFs)是否能抑制尾吊(hind-limb suspension,HLS)所致大鼠的骨量丢失。方法 30只雌性SD大鼠(180±10)g,分为3组,每组10只,分别为对照组、HLS组和HLS+SEMFs组。除对照组外,HLS组和HLS+SEMFs组大鼠进行尾吊,之后,HLS+SEMFs组大鼠每天进行1.5 h 50 Hz1.8 m T正弦交变电磁场干涉。4 w后处死全部大鼠,对各组大鼠进行重要脏器的器官指数计算和病理学观察、离体骨密度检测、骨生物力学分析和骨形态计量学分析以及Micro-CT扫描。结果实验期间各组大鼠的体重及重要脏器的器官指数差异无统计学意义(P0.05),脏器病理学观察未见异常变化;骨密度结果显示,SEMFs有效提高股骨和椎骨的离体骨密度;生物力学实验表明,SEMFs减轻了HLS引起的股骨和椎骨力学性能的降低。此外,SEMFs能增加骨钙素(osteocalcin,OC)含量,并且对抗酒石酸酸性磷酸酶5b(tartrate-resistant acid phosphatase 5b,TRACP-5b)具有一定的抑制作用;Micro-CT结果显示,SEMFs部分抑制HLS造成的松质骨骨微结构的减少,相比HLS组,骨小梁数、骨小梁厚度、骨小梁面积显著升高,且分离度下降;骨组织形态学分析同样表明SEMFs改善了松质骨骨微结构的恶化。结论 50 Hz 1.8 m T SEMFs能抑制HLS所致大鼠的骨量丢失,其可能机制是具有抑制骨吸收和提高骨形成的双重活性,这将为电磁场治疗骨质疏松症的临床应用提供依据。     

辛伐他汀部分阻止尾悬吊大鼠股骨近端骨量的丢失

目的：观察辛伐他汀体内给药对尾悬吊大鼠骨量和骨髓基质干细胞增殖﹑分化的影响。方法18只9周龄雄性SD大鼠被随机分成3组,每组6只：第一组（G1）,正常对照组,每天蒸馏水灌胃;第二组（G2）,尾悬吊组,每天蒸馏水灌胃;第三组（G3）,尾悬吊大鼠每天20 mg/kg辛伐他汀灌胃。实验持续3周,所有大鼠在最后一次灌胃的第二天被处死,取大鼠右侧股骨用双能X线骨密度仪测量骨密度。取大鼠左侧股骨和胫骨骨髓细胞向成骨细胞定向培养,并作如下检测：碱性磷酸酶活性和von Kossa染色分别在细胞培养第16天和25天检测。在细胞培养第21天,采用Real-time RT-PCR检测BMP-2、RANKL mRNA的表达。结果尾悬吊组大鼠骨量低于对照组。全长骨密度（ tBMD）及远端骨密度（ dBMD） G1组显著高于G2、G3组,近端骨密度（ pBMD） G1组显著高于G2组,但与G3组没有区别, G3组高于G2组但没有显著差别。细胞外基质矿化能力（ von Kossa染色）、ALP比活性以及RANKL、BMP-2 mRNA水平各组间均没有显著差别。结论尾悬吊3周可致大鼠骨骨质疏松,辛伐他汀体内给药可部分阻止股骨近端骨量丢失,但不能显著促进骨髓基质干细胞向成骨细胞分化。     

蛇床子素对模拟微重力引起的骨质流失的防治作用

目的研究蛇床子素对模拟微重力导致大鼠骨质流失的防治作用。方法将Wistar大鼠随机分为3组:对照组(Ctrl)、尾吊组(HLS)、尾吊给药组(OST)。4周后取后肢骨用双能骨密度仪及万能试验机分别测量各组股骨骨密度及生物力学,并通过micro CT分析骨小梁参数;用Van Gieson(VG)染色观察胫骨形态变化。通过qRT-PCR检测胫骨骨保护素(OPG)和核因子-κB受体激活剂配体(RANKL)mRNA表达水平。用ELISA试剂盒检测血清中骨特异性碱性磷酸酶(BALP)、骨钙素(OCN)和抗酒石酸酸性磷酸酶-5b(TRACP-5b)的含量变化。结果与对照组相比,尾吊组大鼠股骨骨密度及生物力学参数显著降低(P0.05),与尾吊组相比,尾吊给药组骨密度及生物力学显著上升(P0.05);尾吊组骨小梁体积分数(BV/TV)、厚度(Tb.Th)显著降低(P0.01),间距(Tb.Sp)显著升高(P0.01),尾吊给药后BV/TV、Tb.Th及Tb.Sp显著降低(P0.01);VG染色观察尾吊组胫骨骨小梁间隙变大,数量减少,而尾吊给药组骨小梁骨髓腔减少,数量增多;尾吊组血清BALP和OCN浓度显著降低(P0.05),TRACP-5b浓度显著升高(P0.05),当给予蛇床子素后,BALP浓度显著升高(P0.05),而TRACP-5b浓度显著降低(P0.05);尾吊组胫骨OPG/RANKL比值显著降低(P0.05),尾吊给药后,OPG/RANKL比值显著升高(P0.05)。结论蛇床子素可通过促进骨形成和抑制骨吸收两方面有效防治模拟微重力导致的骨质流失。     

间断性水平位站立对尾吊大鼠胫骨骨小梁结构影响的micro-CT评价

目的 应用micro-CT研究尾吊大鼠胫骨骨小梁微结构的变化,以此评价间断性水平位站立对抗模拟失重导致的骨微结构退化的效果.方法 24只SD雄性大鼠随机等分为3组:对照组(CON组)、尾吊组(SUS组)、水平位站立对抗组(ST组).尾吊组大鼠始终保持约30°头低位及后肢自由悬垂不负重状态,水平位站立对抗组在尾吊处理的基础上,大鼠每天固定时间水平站立1 h.实验3周后处死各组大鼠,取其右侧胫骨行micro CT扫描及三维重建,对其骨微结构进行定量分析.结果 选定感兴趣区(ROI)行定量分析及三维可视化后,与CON组相比,SUS组胫骨骨体积分数(BVF)、骨小梁数量(Tb.N)、骨小梁厚度(Tb.Th)均显著降低,而骨表面积/体积(BS/BV)、骨小梁间隙(Tb.Sp)及骨小梁模式因子(Trabecular Pattern Factor,TPF)均显著升高;ST组的变化介于SUS组和CON组之间;三维可视化图像结果与物理参数结果趋势一致.应用One-Way ANOVA分析及多重比较LSD-t检验,三组各参数之间统计学差异显著(P＜0.05).结论 间断性水平位站立可明显减弱尾吊大鼠胫骨的微结构退化和骨质丢失,而micro CT可以有效地辨别胫骨松质骨微结构的精细变化.     

中药复方干预3周模拟失重大鼠骨丢失的初步研究

目的：研究中药复方对3周模拟失重大鼠骨骼改变的干预作用,初步观察模拟失重情况下,复方对钙剂（牡蛎醋酸水解物）的协同作用。方法：Wistar大鼠,雄性,30只,随机分为3组,空白组、模型组、中药组,每组10只。尾吊模拟失重3周,中药复方（含熟地黄、怀牛膝、黄芪、当归、牡蛎醋酸水解物等）水煎剂灌胃。观察中药对模拟失重大鼠血清钙与磷水平、后身骨密度、骨矿盐含量、力学强度的影响。结果：模拟失重3周后,与空白组比较,模型组血清钙磷均显著升高（P〈0.01）,后身骨密度、骨力学强度均显著降低（P〈0.01）;中药组血钙磷升高程度有减小趋势,骨密度显著提高（P〈0.01或0.05）,骨力学强度有较大改善趋势。结论：3周尾吊模拟失重可造成大鼠后身骨量显著丢失和强度下降,中药可较好地改善上述情况。单纯补充钙剂不足以对抗模拟失重所致骨丢失,复方中熟地黄、怀牛膝、黄芪、当归等可能对钙剂牡蛎起到了协同作用。     

骨质疏松大鼠股骨内单次注射辛伐他汀强化骨骼的实验研究

 目的 研究骨质疏松骨骼局部注射辛伐他汀刺激成骨的效果, 探索疏松骨骼局部给药预 防脆性骨折的治疗方法。 方法36 只3 月龄雌性SD 大鼠双侧卵巢切除后加低钙饮食3个月, 制备大鼠 骨质疏松模型。实验大鼠随机分为3 组, 每组12 只, 分别在实验大鼠的左侧股骨髓腔内单次注射辛伐 他汀溶液5 mg、10 mg, 对照组单纯注射空白载体。分别在术后1 个月及术后5 个月每组随机处死半数 大鼠(n=6)并取材。双能X 线骨密度仪测定骨密度、Micro-CT扫描并定量分析骨组织形态改变、骨生物 力学测试研究骨骼力学性能的变化。 结果 辛伐他汀局部注射后1 个月和5 个月, 辛伐他汀注射组的 骨密度、骨微结构参数如骨皮质厚度、骨小梁密度及连接率明显优于对照组, 股骨髁及股骨颈的力学性 能明显高于对照组。单次注射辛伐他汀的局部骨强化效果至少持续5 个月, 对照组骨量则持续丢失, 力 学性能持续降低。 结论 疏松骨骼单次注射小剂量辛伐他汀可强效而持久地促进皮质骨形成及骨小梁 改建, 改善骨骼微结构, 增加骨密度及骨强度, 可作为强化局部、防治骨质疏松骨折的新选择。     

基于“脾肾相关”理论防治模拟失重大鼠Wnt信号通路介导的骨形成机制研究

目的基于"脾肾相关"理论考察健脾方药、补肾方药和补肾健脾方药对尾吊模拟失重大鼠骨丢失的防治作用,并揭示其分子机制。方法 50只大鼠随机分成空白对照组、尾吊组、健脾组、补肾组、补肾健脾组,每组10只。除空白对照组外,其余各组大鼠均以尾部悬吊法造模,同时对中药干预的各组大鼠予以相应方药灌胃。实验第28天称体重并取材,取大鼠双侧股骨和胫骨并称重,检测大鼠股骨和胫骨骨密度和生物力学性能,Western Blot方法检测大鼠胫骨内碱性磷酸酶(ALP)、骨连接蛋白(SPARC)、转录激活子4(ATF4)、β-连环蛋白(β-catenin)、分泌型糖蛋白(DKK1)、含环蛋白的跨膜蛋白2(Kremen2)、分泌型卷曲相关蛋白2(SFRP2)蛋白表达量。结果与空白对照组比,尾吊组大鼠股骨和胫骨生物力学性能降低(P0.05),胫骨和股骨与体重比值、骨密度、胫骨ALP、SPARC、ATF4、β-catenin、SFRP2蛋白表达量显著降低(P0.01),DKK1、Kremen2蛋白表达量显著升高(P0.01);与尾吊组比,健脾组、补肾组、补肾健脾组大鼠的胫骨和股骨与体重的比值、骨密度、生物力学性能、胫骨中ALP、SPARC、ATF4蛋白表达量升高,Kremen2蛋白表达量降低(P0.05),健脾组和补肾健脾组大鼠胫骨β-catenin蛋白表达量显著升高(P0.01),补肾组和补肾健脾组大鼠胫骨SFRP2蛋白表达量显著升高(P0.01),DKK1蛋白表达量显著降低(P0.01);与补肾健脾组比,补肾组和健脾组大鼠的胫骨和股骨与体重比值、骨密度、股骨生物力学性能、胫骨ALP、SPARC、ATF4蛋白表达量降低(P0.05),补肾组大鼠胫骨生物力学性能、β-catenin蛋白表达量降低、Kremen2蛋白表达量升高(P0.05),健脾组大鼠胫骨SFRP2蛋白表达量降低、DKK1蛋白表达量升高(P0.05)。结论基于"脾肾相关"理论采用的补肾健脾方、补肾方和健脾方均能对抗尾吊模拟失重导致的骨丢失,以补肾健脾方作用为优,作用机制可能与激活经典Wnt信号通路有关。三首方剂作用于经典Wnt信号通路上的靶点略有差异。     

金匮肾气丸对去势大鼠骨微结构及ALP、OPG、IL-6的影响

目的研究金匮肾气丸防治骨质疏松的机制,探讨"温补肾阳,以生髓壮骨"中医理论在绝经后骨质疏松中的应用。方法采用卵巢切除法复制绝经后骨质疏松大鼠模型,随机分为模型组、金匮肾气丸高、低剂量组、雌二醇组,同时设置假手术组作为对照组,各组分别给予相应的药物灌胃。给药3月后处死取材,计算子宫系数; HE染色观察子宫的病理变化; Micro-CT检测大鼠骨密度及骨微结构的变化;全自动生化分析仪检测各组大鼠血清中血糖、血脂及钙磷的变化; ELISA检测各组大鼠血清中ALP、IL-6及OPG表达的变化。结果与假手术组相比,模型组大鼠骨密度显著下降(P0.05),骨微结构破坏明显;与模型组相比,金匮肾气丸低剂量组大鼠骨密度得到了有效提高、骨微结构获得改善,血糖、血脂水平降低,血清中钙磷的含量明显提高,血清中ALP、IL-6含量降低,OPG含量升高。结论金匮肾气丸能够提高去卵巢大鼠的骨量,防治绝经后骨质疏松症,其作用机理可能与降低ALP、IL-6,提高OPG含量有关。     

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.     

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.