椎弓根螺钉把持椎弓根皮质骨对其固定强度的影响

目的：了解椎弓根螺钉把持椎弓根皮质骨对椎弓根螺钉固定强度的影响。方法：将成年羊腰椎椎弓根48个依据椎弓根皮质骨内径和椎弓根螺钉直径（6．25mm）的相对关系分为三组：A组，螺钉直径小于椎弓根皮质骨内径：B组．螺钉直径超出椎弓根皮质骨内径0.01～0．50mm；C组，螺钉直径超出椎弓根皮质骨内径0.51～1．00mm。每组再根据进钉深度与椎弓根长度（平均约8mm）的相对关系分为Ⅰ（进钉深度为16mm）、Ⅱ（进钉深度为8mm）两组。将椎弓根螺钉置入椎弓根中，观察钉道结构、膨胀情况，测量椎弓根螺钉最大轴向拔出力。结果：椎弓根螺钉置入后，椎弓根发生不同程度膨胀；椎弓根螺纹能够切入皮质骨中；C Ⅰ组最大轴向拔出力比A Ⅰ组和B Ⅰ组大（P〈0．05），C Ⅱ组最大轴向拔出力比A Ⅱ组和B Ⅱ组大（P〈0．05），B Ⅱ组比A Ⅱ组大（P〈0.05）。结论：椎弓根螺钉把持椎弓根皮质骨能够增加椎弓根螺钉的固定强度；且椎弓根螺钉把持椎弓根皮质骨量越大，固定强度越大。     

膨胀式脊柱内固定系统椎弓根螺钉翻修作用的生物力学研究

目的：评价自行设计的膨胀式脊柱同定系统（expansive spinal fixation system，ESFS）的椎弓根螺钉对椎弓根螺钉固定失败后的翻修作用。方法：将30个深低温冰冻的正常成人腰椎体标本随机分为A、B、C三组．每组10个椎体（20侧椎弓根）。各组标本每个椎体的两侧椎弓根均先拧入直径6．0mm、长45mm的CD-Ⅱ螺钉．行螺钉拔出试验，记录螺钉的最大旋入力矩和最大轴向拔出力。然后将CD-Ⅱ螺钉拔出，各组标本每一椎体随机经一侧椎弓根原钉道拧入直径7．0mm、长45mm的ESFS螺钉；A组另一侧椎弓根拧入直径7．0mm、长45mm的CD-Ⅱ螺钉，B组另一侧拧入直径7．0mm、长45mm的TSRH螺钉．C组另一侧拧入直径7．0mm、长45mm的GSS螺钉。分别测试螺钉最大旋入力矩和最大轴向拔出力。结果：A、B、C三组的ESFS螺钉最大轴向拔出力分别为6mm CD-Ⅱ螺钉的113％、110％和112％，而直径7．0mm、长45mm的CD-Ⅱ螺钉、TSRH螺钉和GSS螺钉的最大轴向拔出力分别只有6mm CD-Ⅱ螺钉的80％、82％和88％，各组ESFS螺钉最大轴向拔出力明显高于其它三种螺钉。差异有显著性（P〈0．01）。各组各螺钉最大旋入力矩之间差异无显著性（P〉0．05）。结论：ESFS螺钉具有很好的椎弓根锚固作用及翻修作用。     

可吸收骨水泥对椎弓根螺钉稳定性的生物力学影响

目的：验证椎弓根螺钉植入时添加可吸收骨水泥α-BSM^TM对螺钉初始稳定性的影响。方法：采用6具人体新鲜腰椎标本,共16个椎体（L3－L5）,将椎弓根螺钉分别置入两侧椎弓根,随机在一侧加α-BSM^TM,测试螺钉最大轴向拔出力（F－max）和螺钉拔出过程中达到最大轴向拔出力时的能量吸收（E－F－max）及螺钉拔出一个螺距（2．0mm)旦的能量吸收（E－2mm)。结果：同未加α－BSM^TM组相比较,椎弓根螺钉最大轴向拔出力F－max在加入α-BSM^TM后,由370N提高到665N,增加了80％。E－F－max和E－2mm也分别增加了83％和68％,差别有统计学显著意义（Wilcoxon's检验,P＜0．01）。最大轴向拔出力F－max（加和不加α-BSM^TM)与椎体松质骨的骨密度（BMD）紧密相关（r=0.9585,0.9056,P＜0．05）。结论：在椎弓根螺钉植入时添加α-BSM^TM能显著提高其初始稳定性。     

经椎弓根螺钉内固定翻修术的生物力学研究

目的探讨不同直径与长度螺钉翻修及骨水泥强化后椎弓根固定的强度,评价其生物力学效果.方法采用10具新鲜成人尸体T10～L5节段共80个椎体标本.首先置入5.5mm/45mm椎弓根螺钉作为对照组.再将脊椎标本随机平分为Ⅰ、Ⅱ两大组.Ⅰ组中40个椎体各随机选择一侧椎弓根应用6.25mm/45mm螺钉翻修(Ⅰ a组),另一侧椎弓根应用7.0mm/45mm螺钉翻修(Ⅰ b组);Ⅱ组中40个椎体各随机选择一侧椎弓根应用6.25mm/55mm螺钉翻修(Ⅱa组),另一侧椎弓根应用7.0mm/55mm螺钉翻修(Ⅱb组).再随机选择56个椎弓根分别行细小螺钉及粗大螺钉骨水泥强化固定翻修(Ⅲa组、Ⅲb组).在858Mini-MTS生物力学实验机上测试最大拔出力及最大扭力矩,并进行统计分析.结果①6.25mm/45mm螺钉翻修5.5mm/45mm螺钉置入后的椎弓根,其拔出力及扭力矩无明显增加(P＞0.05);应用7.0mm/45mm、6.25mm/55mm及7.0mm/55mm螺钉翻修,把持力及扭力矩均明显增加(P＜0.05).②骨水泥强化固定后,螺钉把持力远大于单纯螺钉翻修组,且与螺钉粗细无关.③在对照组及螺钉翻修组,螺钉把持力与扭力矩间有明显相关性,相关系数r=.86.结论①椎弓根螺钉翻修时,单纯螺钉直径增加1.5mm或直径增加0.75mm、长度增加l0mm以及骨水泥强化均可达到翻修固定的生物力学要求,以骨水泥强化固定更为明显.②增加螺钉直径与长度的翻修中,把持力与扭力矩是一致的;而应用骨水泥强化固定时,螺钉把持力主要取决于骨水泥本身及添加物-骨界面结合强度.     

强化膨胀式椎弓根螺钉翻修作用的生物力学评价

目的测试骨水泥强化膨胀式椎弓根螺钉(augmentation expansive pedicle screwfixa-tion with polymethyl methacrylate,AEPS),未强化的膨胀式椎弓根螺钉(expansive pedicle screw,EPS),CDH椎弓根螺钉翻修后的最大轴向拔出力,评价AEPS螺钉的翻修效应。方法24个新鲜小牛腰椎随机分成三组,AEPS组、EPS组、CDH组,每组8个椎体,三组椎体的椎弓根处均预先植入直径6.5mm CDH螺钉,拔出螺钉造成螺钉松动脱出的脊柱模型,然后分别植入AEPS、EPS、CDH螺钉,再次拔出螺钉,记录翻修后最大轴向拔出力。结果AEPS、EPS、CDH螺钉翻修后的最大拔出力分别为(2723.3±565.4)、(2216.3±475.6)和(1321.4±346.7)N,AEPS和EPS螺钉最大拔出力均显著高于CDH螺钉(P<0.05),AEPS轴向拔出力高于EPS螺钉,但差异无统计学意义(P>0.05)。结论AEPS与EPS螺钉具有相当的翻修作用。     

通用型脊柱内固定系统椎弓根螺钉翻修作用的生物力学研究

目的测试自行设计的通用型脊柱内固定系统(generalspinesystem,GSS)椎弓根螺钉以及SOCON、TSRH和Diapason螺钉置入椎体的拔出力及旋入力矩,评价GSS螺钉的翻修作用。方法将36个正常成人腰椎椎体标本随机分为三组,每组12个椎体(24侧椎弓根)。各组标本每个椎体的每侧椎弓根均先拧入CCD螺钉(直径6.0mm,长45mm),行螺钉拔出试验,测试并记录螺钉的最大旋入力矩和最大轴向拔出力。然后各组标本每个椎体均随机选择一侧椎弓根经原钉道拧入GSS螺钉(直径6.5mm,长45mm);第一组另一侧拧入SOCON螺钉(直径7.0mm,长45mm),第二组另一侧拧入TSRH螺钉(直径7.0mm,长45mm),第三组另一侧拧入Diapason螺钉(直径6.7mm,长45mm)。分别测试螺钉最大旋入力矩及最大轴向拔出力。结果第一组GSS螺钉最大轴向拔出力为CCD螺钉的114%,SOCON螺钉为CCD螺钉的108%;GSS螺钉最大轴向拔出力大于SOCON螺钉,差异无显著性(P>0.05);GSS螺钉最大旋入力矩小于SOCON螺钉,差异无显著性(P>0.05)。第二组GSS螺钉最大轴向拔出力为CCD螺钉的127%,TSRH螺钉为CCD螺钉的64%;GSS螺钉最大轴向拔出力大于TSRH螺钉,差异有显著性(P<0.01);GSS螺钉最大旋入力矩大于TSRH螺钉,差异有显著性(P<0.01)。第三组GSS螺钉最大轴向拔出力为CCD螺钉的122%,Diapason螺钉为CCD螺钉的8     

腰椎不同深度置入椎弓根螺钉对把持力的影响

目的：观察椎弓根螺钉在相同水平角度（TSA 角为0°）、相同矢状角度（SSA 角为0°）不同深度时置入单个椎体对把持力的影响,为临床置钉提供理论依据。方法采用6个月龄猪 L2新鲜标本共16个椎体,将32侧椎弓根分4组,按不同深度分70％组、75％组、80％组、85％组分别置入椎弓根螺钉,自动记录仪记录下螺钉载荷-位移的变化曲线,测出最大轴向拔出力及最大拔出能量。结果80％组椎弓根螺钉最大拔出力及最大拔出能量明显大于70％组（P ＜0．05）,75％组与85％组椎弓根螺钉的最大拔出力及最大拔出能量与70％组比较差异无统计学意义（P ＞0．05）。结论不同深度置钉对椎弓根螺钉的把持力随置钉深度的增加而逐渐增大。     

腰骶椎弓根螺钉翻修及强化固定后稳定性比较

[目的]从生物力学角度评价腰骶椎弓根螺钉翻修及强化固定的稳定性。[方法]采用7具新鲜成人尸体L5S1椎体标本,于L5椎体首先置入5.5mm/45mm椎弓根螺钉,然后再置入7.0mm/55mm螺钉翻修,最后应用骨水泥强化固定;S1椎弓根置入初始螺钉为6.25mm/35mm、翻修螺钉为8.0mm/45mm、最后同样行骨水泥强化固定。在858MiniMTS生物力学实验机上分别测试各状态轴向最大拔出力及最大扭力矩。[结果](1)在L5,初始、翻修及骨水泥强化固定状态的最大把持力分别为(1680.7±242.8)N、(2410.3±366.1)N、(3273.0±688.5)N(P<0.05),最大扭力矩分别为(1006.1±205.3)N·mm、(1432.6±213.7)N·mm、(590.7±83.5)N·m(P<0.05);(2)在S1,初始、翻修及骨水泥强化的把持力分别为(926.3±274.2)N、(957.5±336.3)N、(1825.3±199.9)N,最大扭力矩分别为(667.6±88.3)N·mm、(681.4±79.4)N·mm、(558.8±97.2)N·mm;其中初始及翻修状态把持力及扭力矩均无明显差别(P>0.05),骨水泥强化固定后把持力明显增加、扭力矩明显减小(P<0.05)。[结论](1)L5椎弓根螺钉翻修时,螺钉直径增加1.5mm、长度增加10mm或骨水泥强化均可达到翻修固定的生物力学要求,增加脊椎稳定性,以骨水泥强化固定更为明显;(2)S1椎弓根螺钉翻修时,单纯增加螺钉直径和长度不能获得理想的稳定性,而骨水泥强化螺钉固定效果明显。     

不同矢状角度置入椎弓根螺钉的拔钉生物力学研究

目的 观察椎弓根螺钉不同矢状成角置入后单个椎体的拔钉生物力学特点,为临床置钉提供理论依据.方法 采用猪新鲜L1共12个椎体标本,将24侧椎弓根分三组,按不同矢状成角0°组、10°组、-20°组置人椎弓根螺钉,测出最大轴向拔出力.结果 -20°组椎弓根螺钉拔出力及拔出能量最大,0°组最小,10°组界于二者之间;三组之间最大拔出力及拔出能量两两比较P＜0.05.提示各组之间差异均有统计学意义.结论 矢状面成角置钉对螺钉的把持力大于0°角置钉,随置钉角度的增加,螺钉把持力也增大.     

可吸收陶瓷改善椎弓根螺钉稳定性的体外生物力学试验

目的探讨在椎弓根螺钉置入时添加可吸收陶瓷Biobon对椎弓根螺钉稳定性的影响。方法采用28个L3～L5椎体标本,将椎弓根螺钉按标准操作分别置入两侧椎弓根,随机在其中一侧加Biobon。对其中16个椎体测试螺钉最大轴向拔出力F-max和螺钉拔出过程中达到最大轴向拔出力时的能量吸收值E-F-max及螺钉拔出一个螺距2.0mm时的能量吸收值E-2mm。另外12个椎体作梯增负荷的周期抗屈试验。结果同未加Biobon组比较,加入Biobon组的F-max增加了79.7%。E-F-max和E-2mm也分别增加了83.1%和68.2%,两组差异有非常显著性意义Wilcoxon检验,P<0.01。周期抗屈试验中,添加Biobon可使螺钉耐受更强的负荷或在同等负荷下仅产生较小的位移。结论在椎弓根螺钉置入时添加Biobon能显著提高其初始稳定性。     

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.