三种方法建立兔椎间盘退变模型的比较研究

目的选择可靠的椎间盘退变动物模型,能为研究椎间盘退变性疾病的发病机制和治疗提供重要的实验载体。通过3种不同损伤方式诱导建立兔椎间盘退变模型,并采用生物化学和影像学方法比较其退变过程及特点。方法取健康6月龄新西兰大白兔25只,体重2.0～2.5kg,随机分为5组,每组5只,每只均选取L3、4、L4、5、L5、6共3个节段椎间盘进行实验。其中A、B组为纤维环穿刺组,分别采用18G和22G针头穿刺;C组为髓核抽吸组;D组为终板破坏组;E组为假手术对照组。分别于术后2、4、8、16和32周每组各取1只动物行CR和MRI检查,测量椎间盘相对高度,评估并记录各椎间盘退变分级的分值;然后处死实验动物获取椎间盘髓核组织,测定其中的水含量和硫酸化糖胺多糖(sulfated-glycosaminoglycan,s-GAG)含量。结果影像学检查显示除E组外,A～D组手术节段的椎间隙随时间延长逐渐狭窄,上下软骨终板出现不同程度钙化,椎体前缘骨赘形成,椎间盘髓核信号强度呈现逐渐降低趋势。与E组相比,A～D组椎间隙相对高度和椎间盘分级分值分别在4周内不同时间点开始差异有统计学意义(P0.05);C、D组出现明显变化时间早于A、B组。A～D组髓核组织的水含量和s-GAG含量随时间延长也呈逐渐下降的变化趋势;与E组相比,A～D组两者含量分别在8周内不同时间点开始差异有统计学意义(P0.05);C、D组出现明显下降趋势的时间早于A、B组。结论3种手术损伤方式均成功建立了兔椎间盘退变模型。终板破坏法和髓核抽吸法较纤维环穿刺法所诱发的退变过程出现更早,进展较快且退变程度更重。     

实验性椎间盘退变的放射影像学与病理学观察

目的　研究椎间盘退变过程中 ,椎间盘退变的放射影像学与病理学改变。方法　选用 4 0只新西兰大白兔随机分为 2组 ,实验组切除兔腰椎间棘间、棘上韧带及棘突、关节突 ,造成力学失稳状态诱导形成椎间盘退变模型。术后一周、 3个月、 8个月时摄腰椎正、侧位X线片 ,观察腰椎影像学变化。第 3个月、 8个月时取腰椎间盘 ,进行组织检查 ,评定椎间盘退变的病理改变情况。结果　模型建立后 ,3个月、 8个月的X线片显现对照组无明显改变 ,实验组腰椎后突畸形 ,椎间隙狭窄 ,随着时间延长椎体软骨终板钙化更加明显。组织学观察发现 ,实验组随术后时间延长 ,髓核由椎间盘内脱出 ,并伴有椎间盘两侧软骨终板的纤维化即软骨终板发生退变。结论　椎体软骨终板的退变是椎间退变早期的主要表现方式。     

去势小鼠椎体骨质疏松和终板重塑导致椎间盘退变

目的通过去势小鼠模型探讨椎体骨质疏松(osteoporosis,OP)是否影响椎间盘退变(intervertebral disc degeneration,IVDD),并初步阐明OP相关性IVDD的发病机制。方法 30只8周龄健康雌性C57BL/6 J小鼠(16.8±0.6) g,随机分为正常对照组(CT组,n=15)和去势组(OVX组,n=15)。适应性饲养3 d后分别行假手术和双侧卵巢摘除,记录体重等一般资料。术后12周处死小鼠,取下L4/5脊柱节段。Micro-CT检测小鼠L5椎体骨量、微结构、终板孔隙率以及L4/5椎间盘体积变化;番红O-固绿染色观察椎间盘病理改变;免疫组织化学法检测椎间盘Col2的表达,免疫荧光检测椎间盘血管内皮生长因子(vascular endothelial growth factor,VEGF)的表达。结果 OVX组小鼠与CT组相比,腹腔内可见大量脂肪堆积,卵巢明显萎缩,伴随体重明显增加及子宫重量明显减轻(~*P0.05)。Micro-CT结果显示,OVX小鼠可见明显的椎体骨质疏松,与CT组相比骨结构参数骨体积分数、骨小梁数量、骨小梁连接密度明显降低,而骨小梁变异系数及模型指数明显升高(~*P0.05);终板出现明显的骨化重塑和孔隙率增加,同时伴有椎间盘体积的明显降低(~*P0.05)。番红O-固绿染色显示OVX小鼠L4/5椎间盘出现明显退变,可见终板明显骨化和增厚,髓核细胞外基质的降解和结构紊乱。椎间盘免疫组化显示OVX小鼠椎间盘中Col2表达明显降低,在终板骨化区和纤维环中尤其明显,免疫荧光显示在椎间盘终板中VEGF表达明显增加。结论 OVX小鼠椎体OP和终板骨化重塑可促使椎间盘发生退变,终板孔隙的增加及血管新生并不能为椎间盘修复提供更多营养,反而是导致IVDD的重要因素。     

实验性椎间盘退变的放射影像学与病理学观察

目的 研究椎间盘退变过程中，椎间盘退变的放射影像学与病理学改变。方法 选用40只新西兰大白兔随机分为2组，实验组切除兔腰椎间棘间、棘上韧带及棘突、关节突，造成力学失稳状态诱导形成椎间盘退变模型。术后一周、3个月、8个月时摄腰椎正、侧位X线片，观察腰椎影像学变化。第3个月、8个月时取腰椎间盘，进行组织检查，评定椎间盘退变的病理改变情况。结果 模型建立后，3个月、8个月的X线片显现对照组无明显改变，实验组腰椎后突畸形，椎间隙狭窄，随着时间延长椎体软骨终板钙化更加明显。组织学观察发现，实验组随术后时间延长，髓核由椎间盘内脱出，并伴有椎间盘两侧软骨终板的纤维化即软骨终板发生退变。结论 椎体软骨终板的退变是椎间退变早期的主要表现方式。     

高应力与腰椎小关节方向变化关系的实验研究

目的:观察兔腰椎小关节加载应力后小关节方向的变化,并探讨小关节在应力作用下方向变化的机制.方法:将42只6月龄新西兰白兔随机分为正常对照组(A组)、椎间盘退变组(B组)、小关节加载组(C组)及椎间盘退变联合小关节加载组(D组),A组6只,其他3组各12只.对B组和D组动物采用针刺抽吸髓核法建立L3/4、L5/6椎间盘退变模型,对A组和C组仅剥离椎旁肌.建模6周后分别对C组和D组的L3/4、L5/6小关节加载拉簧造成高应力模型,对A组和B组仅行小关节暴露,分别于小关节术后4个月、8个月获取腰椎,进行MicroCT扫描,观察小关节形态,B、C、D组在横断面上测量L3/4、L5/6小关节角度(关节突关节面与椎体正中矢状面的夹角)并将两个节段数据合并分析,A组测量L3/4 、L4/5、L5/6、L6/7小关节角度并将数据合并分析,小关节角度越小,小关节方向越偏向矢状位.结果:组内比较,各组8个月时小关节方向较4个月时更加矢状化(均P＜0.05);同一时间点,D组的小关节方向较B组更加矢状化,C组的小关节方向较A组更加矢状化,差异均有显著性意义(均P＜0.05),A、B组间及C、D组间比较小关节角度无显著性差异(P＞0.05).小关节加载组(C组和D组)的小关节较小关节未加载组(B组)退变严重,时间越长退变越严重;各时间点A组小关节结构清晰.结论:高应力可引起兔腰椎小关节退变,小关节方向的矢状化改变是由小关节退变和重塑所导致.     

腰椎侧凸软骨终板退变的X线表现及临床意义

目的探讨腰椎侧凸软骨终板退变的X线表现及其临床意义。方法收治的退变性腰椎侧凸43例,均行X线平片检查,观察其影像学特点。分别测定凹侧和凸侧每个椎体头、尾侧关节软骨的钙化层厚度,均数行t检验。结果 X线片显示椎间隙楔形样变、椎间隙狭窄、终板钙化和骨赘形成。退变的软骨终板潮标明显前移,钙化和骨化层增厚,形成突向外侧的椎体边缘的骨赘。凹侧和凸侧椎间盘关节软骨钙化层厚度分别为(35±8)μm和(72±12)μm,差异有统计学意义(P0.01)。结论软骨终板退变较其他椎间盘退变的X线征象出现早,详细研究其X线特点,对于诊断退变性腰椎侧凸和设计合理的手术方式具有重要的指导作用。     

颈椎椎间盘退变对终板结构生物力学特性的影响

目的研究颈椎椎间盘对终板结构生物力学特性的影响。方法50节颈椎标本,采用Nachemson椎间盘分级标准将标本分为4组,正常组(n=22)、Ⅰ度退变组(n=10)、Ⅱ度退变组(n=9)、Ⅲ度退变组(n=9),对每一终板平面上20个特定的测试点进行压缩实验,直径2mm的半球形压头以003mm/s的速度垂直于终板平面下压2mm,由所得的力─位移曲线计算出最大压缩力及刚度,采用单因素方差分析、析因分析、SNK检验及相关分析对实验数据进行统计学分析。结果颈椎椎间盘退变可导致颈椎终板最大压缩力及刚度的显著性减小(P<001),且存在负相关关系(分别为rs=-0429,P<0001;rs=-0244,P<0001);上终板随着椎间盘退变的加重终板平面中央承力逐渐变弱,外周承力逐渐增强,下终板的力学分布无明显改变。结论颈椎椎间盘退变是影响终板结构生物力学特性的重要因素,在进行颈椎前路融合术时应警惕由于椎间盘退变引起的“植入物沉陷”。     

Modic改变与椎间盘高度及椎体骨质增生的关系

目的 研究Modic改变与椎间盘高度及椎体边缘骨质增生的关系,探讨Modic改变在腰椎退变中的意义.方法 回顾性研究分析2011年4月至2012年4月150例老年慢性腰腿痛患者的影像学资料,所有患者均进行MRI及腰椎正侧位X线检查,选择患者L1～2至L5～S1椎间盘为研究对象,150例患者共观测750个椎间盘、椎体及椎间盘邻近终板.观察患者腰椎终板Modic改变的发生率、椎间盘高度以及椎体边缘骨质增生程度,定义椎间盘高度/椎间盘平均高度＜50％为椎间盘塌陷.将所有患者腰椎间盘分为4组,A1组:椎间盘塌陷,椎体无或轻度骨质增生;A2组:椎间盘塌陷,椎体重度骨质增生;B1组:无椎间盘塌陷,椎体无或轻度骨质增生;B2组:无椎间盘塌陷,椎体重度骨质增生.采用x2检验方法,对4个组Modic改变发生率进行比较,分析椎间盘高度以及椎体骨质增生与Modic改变的关系.结果 4组共观测了750个椎间盘,A1组208个椎间盘,终板Modic改变发生率为54.3％;A2组135个椎间盘,终板Modic改变发生率为34.8％;B1组225个椎间盘,终板Modic改变发生率为16.9％;B2组182个椎间盘,终板Modic改变发生率为29.7％.4组间Modic改变发生率差异有统计学意义(x2 =69.565,P＜0.05).组间两两比较,A1组与A2、B1和B2组比较,差异均有统计学意义(x2=12.524、66.701和24.102,P ＜0.00714).A2组与B1组比较差异有统计学意义(x2=15.032,P＜0.00714),但与B2组比较差异无统计学意义(x2=0.945,P＞0.00714).B1与B2组比较,差异有统计学意义(x2=9.395,P＜0.00714).结论 老年慢性腰腿痛患者中椎间盘高度的丢失且不伴有重度椎体骨质增生的终板Modic改变发生率较高,椎间盘塌陷合并重度椎体骨质增生患者与单纯重度椎体骨质增生患者的Modic改变发生率无明显差别.     

高应力导致兔腰椎小关节骨性关节炎的实验研究

目的:观察兔腰椎小关节加载应力后小关节在应力作用下的病理变化,并探讨其病理机制。方法:将42只新西兰白兔随机分为正常对照组(A组)、椎间盘退变组(B组)、小关节加力组(C组)及椎间盘退变及小关节加力组(D组)。对B组和D组动物采用针刺抽吸髓核法建立椎间盘退变模型,建模6周后分别对C组和D组的L3/4、L5/6小关节加载拉簧造成高应力模型,对A组和B组仅行小关节暴露,分别于术后4个月、8个月取腰椎小关节,采用番红O-快绿染色,进行Mankin评分判断软骨退变程度并分为轻度、中度及重度;免疫组化染色观察细胞因子IL-1β、IL-6、TNF-α在小关节软骨中的表达。结果:不同组间小关节退变程度有显著性差异(F=92.77,P=0.000),组内比较,各组8个月时小关节退变程度较4个月时严重(P<0.05);同一时间段不同组间比较,小关节加力组(C组和D组)的小关节退变程度较小关节未加力组(A组和B组)严重,差异均有显著性(P<0.05),A、B组间及C、D组间比较,小关节退变程度无显著性差异(P>0.05)。三种细胞因子随着软骨退变程度的增加而表达增强,而严重退变的软骨由于软骨细胞数减少表达反而有所下降。结论:高应力可导致腰椎小关节退变,应力作用时间越长,小关节退变越严重。腰椎小关节软骨细胞的退变伴随着炎性细胞因子合成、分泌的改变。     

椎体成形术对兔手术椎体相邻椎间盘的影响

[目的]探讨椎体成形术(vertebroplasty,VP)是否会引起兔手术椎体相邻椎间盘的退变,以及椎间盘的退变程度与聚甲基丙烯酸甲酯(polymethyl methacrylate,PMMA)用量的相关性.[方法]80只5个月龄雌性新西兰大白兔,随机选16只为正常对照组(A组),剩余的64只采用去势法建立兔骨质疏松模型后随机分为4组,设L5为手术椎体.B组(实验对照组)L5不注入任何药物;C组L5注入PMMA0.1 ml;D组L5注入PMMA0.3 ml;E组L5注入PMMA 0.5ml.每组分别于术前及术后1、3、6个月各处死4只动物,进行X线、MRI检查,通过计算椎间盘高度指数百分数(disc height Index percentage,DHIP)和MRI指数,来定量分析椎间盘退变程度.并取相邻椎间盘送病理,采用Masuda评分评估椎间盘退变程度.[结果]A、B组椎间盘的DHIP、MRI指数和Masuda评分在各个时间点均无明显变化.C、D、E组在术前及术后1个月时的DHIP、MRI指数和Masuda评分较A、B组无明显改变.第3个月时,E组椎间盘的DHIP、MRI指数较其他各组均有降低,且MRI指数和Masuda评分较A、B组有统计学差异(P＜0.05).第6个月时,D、E组椎间盘的DHIP、MRI指数和Masuda评分跟术前及术后1、3个月比较均有显著统计学差异(P＜0.05),E组的DHIP和MRI指数均明显低于A、B、C、D组.组织学退变也较A、B、C、D明显,Ma-suda评分明显高于A、B、C、D组.[结论]VP可以引起手术椎体相邻椎间盘的退变,并且椎间盘退变程度与PM-MA用量相关.     

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 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.     

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.