骨组织工程快速成型支架改性的相关研究

目的探讨胶原杂化及磷灰石表面沉积改性后的聚乳酸一羟基乙酸共聚物／β-磷酸三钙（PLGA／β—TCP）作为快速成型支架应用于骨组织工程的可行性。方法使用骨髓基质干细胞对胶原杂化及磷灰石表面沉积改性后的PLGA／β-TCP的生物相容性进行评估，通过扫描电镜观察改性后材料的表面特性及细胞与材料复合的形态学特征；细胞与材料复合后的繁殖与分化能力分别使用细胞计数及碱性磷酸酶定量方法进行评估。结果通过对亲水性、细胞增殖能力及碱性磷酸酶测定证实改性后的PLGA／β-TCP快速成型支架较单纯材料其亲水性及生物相容性有明显提高（P〈0．05）。结论胶原杂化及磷灰石表面沉积改性后的PLGA／β—TCP快速成型支架可作为三维支架应用于骨组织工程。     

新型聚乳酸-羟基乙酸(PLGA)支架的细胞相容性研究

目的研究骨髓基质干细胞(BMSCs)与该聚乳酸-羟基乙酸(PLGA)类支架的细胞相容性及体外粘附情况,为制备负载多种细胞因子的PLGA类支架提供研究基础。方法抽取新西兰兔骨髓,用全骨髓培养法获取单核细胞,经条件培养液体外诱导、扩增。设立空白BMSCs组和具有良好细胞相容性的β-磷酸三钙(β-TCP)为对照组。BMSCs以1×106/mL浓度接种于PLGA和β-TCP上,通过倒置相差显微镜、扫描电镜观察细胞生长及细胞与材料的附着情况。以MTT实验、流式细胞仪等手段检测各组细胞增殖和细胞周期变化情况。结果BMSCs可较好粘附于PLGA支架上,且该PLGA类支架对细胞增殖、生长周期无明显影响。结论该PLGA类支架的细胞相容性较好,并可进一步作为多种细胞因子载体构建缓释型支架,从而用于骨组织工程。     

基于增材制造和凝胶注模成型技术的多孔生物陶瓷支架制备与表征

目的探讨基于增材制造和凝胶注模成型技术的多孔β-磷酸三钙（TCP）生物陶瓷支架的制备方法及其表征。方法利用计算机辅助设计（CAD）软件设计支架内部孔隙结构,通过光固化快速成型技术制造相应的树脂模具,在模具中填充生物材料,待其固化后通过热分解去除树脂模具,然后对所形成的多孔β-TCP支架的微观孔隙结构特征、力学性能以及体外细胞相容性进行检测。结果多孔β-TCP支架孔隙结构与设计结构一致,孔隙率为45.1%±1.2%,孔的尺寸为300～500μm;力学性能测试表明,支架的平均抗压强度为5.3±0.8 MPa;成骨细胞能够在支架上黏附生长,支架具有良好的生物相容性。结论基于增材制造技术和凝胶注模成型工艺的多孔生物陶瓷支架制备方法,可实现支架复杂外形与内部微结构的精确控制和一体化制造。     

唑来膦酸、聚乳酸-羟基乙酸聚合物、β-磷酸三钙复合支架修复去势大鼠股骨干骺端骨缺损的实验研究

目的唑来膦酸、聚乳酸-羟基乙酸聚合物、β-磷酸三钙(ZA、PLGA、β-TCP)复合支架对去势大鼠股骨干骺端骨缺损的修复作用。方法雌性SD大鼠经过双侧去卵巢手术后饲养3个月建立骨质疏松模型,随后在大鼠双侧股骨干骺端建立直径为3 mm圆形骨缺损,上述大鼠随机分为4组;分别置入ZA、PLGA支架,β-TCP支架和ZA、PLGA、β-TCP复合支架,不置入支架材料的为对照组。术后12周取材,通过Micro-CT扫描重建和病理组织学评价三组支架材料的成骨作用。结果术后观察发现空白对照组骨缺损未修复,骨缺损断端硬化,而其他3组骨缺损均有不同程度修复。植入骨质疏松大鼠体内12周后,三组材料随着材料的降解均有新生骨长入,且三组新骨生成率均显著优于对照组(P0.05),缺损区域都有较高BV/TV、Tb.Th、Tb.N、Conn.D、骨矿化沉积率(MAR)和较低的Tb.Sp,其中以ZA、PLGA、β-TCP组最高。Micro-CT和病理组织学结果提示ZA、PLGA、β-TCP组骨修复效果较ZA、PLGA与β-TCP组更好。结论 ZA、PLGA、β-TCP复合支架具有明显促进去势大鼠股骨干骺端骨缺损修复的作用。     

载利福喷丁/聚乳酸-聚乙醇酸共聚物微球制备及体外释放

目的：制备可用于持续抑制脊柱结核术后病灶残留结核分枝杆菌的载利福喷丁／聚乳酸-聚乙醇酸共聚物[ Poly（ lactic-co-glycolic acid）, PLGA]微球,并研究其体外释放性能。方法通过乳化-溶剂挥发法制备载利福喷丁／PLGA微球,光学显微镜和扫描电镜观察微球形貌,激光粒度分布仪测定微球粒径及分布,紫外分光光度计测定微球载药量及包封率。检测利福喷丁抗结核分枝杆菌的最低抑菌浓度,并以pH＝7．4的PBS缓冲溶液为释放介质,紫外分光光度计检测载药微球体外释放特性。结果载利福喷丁／PLGA微球成球形状良好,表面光滑,分散性好,粒径分布均匀,平均粒径为25．49μm。载药量及包封率分别为21．37％±0．16％和74．79％±2．71％。体外释放实验显示在突释期内,利福喷丁释放量占载药微球中药物含量的37．08％±1．68％;在缓释期内载药微球释药速度减慢,第5周释放量仍超过利福喷丁抗结核分枝杆菌的最低抑菌浓度,35 d后体外累积释放量为80．67％±0．97％,仍高于利福喷丁抗结核分枝杆菌的最低抑菌浓度2μg／mL。结论 PLGA是一种理想的控缓释材料,所制备的载利福喷丁／PLGA微球具有良好的控释效果,是一种有效的抗结核缓释剂型。     

高孔隙连通性β-磷酸三钙细胞支架的制备

目的 改进多孔β-TCP支架的制备方法,提高支架的孔隙连通性、孔隙结构的均匀性以及支架的抗压特性.方法 利用两阶段中和反应工艺,制备β-TCP粉末原料;将粘结剂均匀涂布在致孔剂表面后与β-TCP粉末混合,添加高温液相传质介质,再次混合形成致孔剂与β-TCP粉末的均匀混合体,加压成型、煅烧制备三维多孔细胞支架;X-衍射检测原料和支架的成分,扫描电镜观察支架的孔隙结构,力学实验仪测定支架的抗压性能.结果 原料和支架化学成分均为β-TCP;支架的孔隙呈球形、分布均匀、孔隙间几乎完全连通,大孔平均孔径781.38±70.47(n=12)μm,连通孔径297.88±66.86(n=13)μm;孔隙率、吸水率和抗压强度分别为52.27±0.11(n=6)Vol%、31.82±0.13(n=6)Wt%和11.40±0.07(n=6)MPa.结论 两阶段中和反应工艺能够制备出纯的β-TCP粉末,改进的支架制备技术,可以制备出孔隙率高、强度大、孔隙大小可控、孔隙分布均匀、孔隙间几乎完全连通的β-TCP支架,具备了组织工程要求的结构特征.     

多孔钙磷陶瓷表面浸涂制备明胶/HA复合涂层

目的采用有机泡沫浸渍法制备β-磷酸三钙（β-TCP）多孔生物陶瓷，以明胶／羟基磷灰石（Hydroxyapatite，HA）复合浆料对其进行表面浸涂处理。本研究旨在保证高孔隙率的前提下提高多孔支架的综合性能。方法利用X-射线衍射仪对β-TCP多孔生物陶瓷进行相组成分析，并研究多孔支架涂覆前后的孔隙率和孔隙特征的变化以及不同明胶／HA比例对支架性能的影响。结果β-TCP多孔生物陶瓷烧结后的主要成分为（Ca，Mg），（PO4）2和β-CaEP2O7。涂覆前后多孔支架的孔隙率并没有发生明显改变，但涂覆处理后表面粗糙度明显增大，涂层与支架具有良好的结合界面，涂层中有大量的微孔存在。结论涂覆处理在β-TCP多孔生物陶瓷支架孔隙率基本不变的情况下，成功地在其表面制备出明胶／HA复合涂层，随之形成的粗糙表面形貌，将有利于细胞的早期粘附。     

明胶-硫酸软骨素-透明质酸钠作为组织工程软骨支架的实验研究

目的探索明胶-硫酸软骨素-透明质酸钠多孔支架的制备方法和其作为组织工程软骨支架的可行性。方法光镜和扫描电镜观察-20℃、-80℃及液氮条件下冷冻抽真空干燥制备的明胶-硫酸软骨素-透明质酸钠支架的孔径、孔隙率、交通孔和密度;测定不同条件制备的支架材料与正常软骨的压缩载荷-形变曲线;分离、扩增兔骨髓基质干细胞(mesenchymalstemcells,MSCs),接种于不同条件制备的支架材料上培养,MTT检测MSCs在支架上的黏附率及多孔支架对细胞增殖功能的影响。结果在-20℃、-80℃及液氮条件下制备的支架材料具有疏松多孔结构,孔径依次为300±45μm、230±30μm和45±10μm,孔隙率为81%、79%和56%,密度为9.41±0.25μg/mm3、11.50±0.36μg/mm3和29.50±0.61μg/mm3;-80℃和液氮条件下制备的支架材料,力学强度接近于正常软骨;MTT测得细胞在-20℃、-80℃及液氮条件下制备的支架材料,黏附率分别为85.0%、87.5%和56.3%;可轻度促进MSCs增殖。结论-80℃条件下抽真空干燥制备的明胶-硫酸软骨素-透明质酸钠多孔支架,具有良好的孔径、孔隙率和抗压缩载荷能力,与MSCs具有较好的相容性,是软骨组织工程中的一种新型仿生支架材料。     

不同比例三联抗结核药物复合缓释材料的释药性能观察

目的 :观察不同比例三联抗结核药物复合缓释材料在模拟体液中的药物释药性能。方法 :以聚乳酸-羟基乙酸(PLGA)作为载体,采用双乳、喷涂、冷冻干燥溶剂挥发法制备不同比例抗结核药物的复合缓释材料:A组,异烟肼(INH,H)∶利福平(RFP,R)∶吡嗪酰胺(PZA,Z)=15∶15∶30;B组,H∶R∶Z=20∶30∶50;C组,H∶R∶Z=30∶30∶120;D组,H∶R∶Z=80∶120∶250。药物总质量与PLGA之比为1∶5。扫描电子显微镜(SEM)观察HRZ/PLGA复合缓释材料的表面形态,高效液相色谱法(HPLC)检测其在模拟体液中H、R、Z三种药物的释放浓度,计算药物累计释放量及释放率,分析其体外缓释性能。结果:A组和B组缓释材料表面分散均匀,空隙规则、分布均匀,直径分别为23.07±0.38μm和25.67±1.26μm;C组和D组缓释材料分散欠均匀,空隙不规则、分布欠均匀,直径分别为31.25±1.98μm和45.67±3.26μm。A组H、R、Z分别于42d、56d、42d的累计缓释度超过50%,于70d时的阶段释药量分别为157.43±057μg、129.29±0.14μg、196.43±0.28μg,浓度分别为28.486μg/ml、23.525μg/ml、39.265μg/ml。B组H、R、Z分别于35d、42d、35d的累计缓释度超过50%,于70d时阶段释药量分别为9.89±0.96μg、21.71±0.42μg、51.12±0.87μg,浓度分别为1.789μg/ml、1.618μg/ml、10.242μg/ml。C组H、R、Z分别于21d、35d、42d的累计缓释度均超过50%,于70d时阶段释药量分别为1.76±0.49μg、8.43±0.31μg、81.14±0.58μg,浓度分别为0.352μg/ml、1.618μg/ml、10.242μg/ml。D组H、R、Z分别于28d、42d、35d的累计缓释度均超过50%,于70d时阶段释药量分别为1.71±0.21μg、14.01±0.42μg、65.57±0.26μg,浓度分别为0.312μg/ml、2.128μg/ml、13.516μg/ml。70d时A组三种药物浓度均大于各自的10倍最低抑菌浓度(MIC),且A组分散均匀,空隙规则、分布均匀,直径约为23.07±0.38μm,三种药物在不同的时间段释放行为不相同,前14d药物缓释规律按Higuchi方程拟合最好,即前14d三种药物按照扩散的形式进行缓释,14d后三种药物按照零级动力学缓释曲线释放,即等量缓释。其余3组均有药物未达到10倍MIC。结论:复合HRZ/PLGA缓释材料具有优良的载药及药物缓释效果,是一种理想的复合药物缓释系统,其中H∶R∶Z=15∶15∶30的HRZ/PLGA缓释材料为较佳配方。     

羟基磷灰石/β－磷酸三钙/甲壳素复合多孔支架材料的制备及生物相容性研究

目的 探讨羟基磷灰石/β-磷酸三钙/甲壳素(HAP/β-TCP/CS)多孔支架的制备及其与人体骨髓间质干细胞(MSCs)的生物相容性.方法 以羟基磷灰石粉体为基体,采用有机泡沫浸渍-发泡复合成型工艺制备出羟基磷灰石/β-磷酸三钙多孔支架,再将该多孔支架与甲壳素复合得到有机-无机复合支架,然后通过体外培养实验评价该复合支架的干细胞相容性.结果 复合甲壳素可以显著提高HAP/β-TCP支架的抗压强度,并且该支架具有三维连通网状结构,细胞在支架上粘附,生长良好.结论 该复合多孔支架具有良好的干细胞亲和性和生物相容性.     

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.     

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.     

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.     

Dilemma of Membrane Biocompatibility and Reuse

Abstract: Numerous articles have been published on the multiple use of dialyzers and on the effect of different reprocessing chemicals and techniques on the dialyzer biocompatibility and performance. The results often appear contradictory, especially those comparing standard biocompatibility parameters. Despite this confusion, a discerning review of the published works allows certain limited conclusions to be drawn. Reprocessing of used hemodialyzers changes the biocompatibility profile of a dialyzer as defined by the parameters complement activation. leukopenia, and cytokine release. The effect of reprocessing depends on the chemicals and reprocessing technique applied and also on the type of membrane polymer being subjected to the reprocessing procedure. Reports of pyrogenic reactions indicate that the flux of the membrane also influences how suitable it is for safe reuse. An increased risk of allergic and pyrogenic reactions appears to be associated with dialyzer reuse. Furthermore, there has been a lack of investigations into the immunologic effect of the layer of adsorbed and chemically altered proteins that remains on the inner surface of reprocessed dialyzers. We conclude that the clinical benefit of dialyzer reuse cannot be generally accepted from a biocompatibility point of view.     

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.