3D打印个体化人工椎体在多节段脊柱肿瘤切除后脊柱稳定性重建中的应用

目的:探讨3D打印个体化人工椎体在多节段脊柱肿瘤切除后脊柱稳定性重建中应用的安全性和有效性。方法:回顾性分析2017年5月～2019年12月在我院行多节段脊柱肿瘤全切并行3D打印人工椎体脊柱稳定性重建的患者9例,其中男性3例,女性6例;年龄25～64岁,平均41.7±10.5岁,随访18.3±11.4个月(6～36个月)。9例均为原发肿瘤:T5～T7骨母细胞瘤术后复发1例,T7～T8上皮样血管肉瘤1例,T10～T11未分化小圆细胞肉瘤1例,T11～L1软骨肉瘤1例,骨巨细胞瘤5例(T6～T8共2例,T2～T3、T4～T5、T11～L1各1例)。依据肿瘤位置及周围软组织侵袭程度,采取单纯后路手术方式8例,前后路联合手术方式1例行多节段全椎体切除,并通过激光选区融化技术构建个体化3D打印人工椎体进行脊柱稳定性重建。记录手术时间、出血量,通过术后X线片(1个月、3个月、6个月、12个月)及CT(6个月、12个月、24个月)定期复查,之后每6个月复查1次。应用BrantiganSteffee脊柱融合分级评估人工椎体稳定性、界面骨融合情况,手术前及术后1周进行Frankel神经功能评分及疼痛视觉模拟(visual analogue scale,VAS)评分。术后定期观察肿瘤是否复发生原位复发、远处转移以及患者生存情况。结果:所有患者均成功接受多节段脊柱肿瘤切除3D打印人工椎体脊柱稳定性重建术,其中2个节段椎体切除4例,3个节段椎体切除5例。患者手术时间433.3±174.6min(235～740min),术中出血量4816.7±3221.2ml(1000～14000ml)。术前的VAS评分4.1±1.1分,术后7d患者的VAS评分1.2±0.4分,差异具有统计学意义(P0.001)。术前Frankel分级为D级的3例患者术后7d时有2例恢复到E级,1例无明显变化,6例E级患者无明显变化。随访期内3D打印人工椎体与邻近椎体匹配情况良好,无松动、下沉及移位,同时未出现断钉、断棒等内固定失败情况。术后6个月,人工椎体与邻近椎体接触紧密,开始出现界面骨长入,术后12个月,人工椎体与邻近椎体出现骨性连接,发生骨性融合。随访期内7例患者无肿瘤复发转移,1例软骨肉瘤患者术后16个月局部复发,安罗替尼治疗后肿瘤无恶化,1例上皮样血管肉瘤患者全身多发转移于术后18个月死亡,患者中位生存期18个月。结论:3D打印个体化人工椎体可以满足多节段脊柱肿瘤切除后脊柱稳定性重建的要求,精确恢复椎体连续性,精准匹配相邻椎体,自身孔隙结构利于骨的长入,是一种多节段脊柱肿瘤切除后理想的脊柱稳定性重建方法。     

选择性腰动脉栓塞全脊椎切除重建术治疗腰椎骨巨细胞瘤

目的 探讨选择性腰动脉栓塞全脊柱切除及稳定性重建治疗腰椎骨巨细胞瘤的疗效。方法2例腰椎骨巨细胞瘤患者采用术前选择性腰动脉介入栓塞,全期手术行全脊椎切除、前后路联合重建脊柱稳定性的治疗方案。结果 2例术后均获得15个月随访,神经功能恢复满意,植入椎体获得骨性融合,脊柱稳定性良好。结论 选择性腰动脉栓塞下全脊椎切除,前后路联合重建脊柱稳定性治疗腰椎骨巨细胞瘤出血少,疗效满意。     

全脊椎切除及脊柱稳定性重建治疗颈胸段脊柱肿瘤的疗效分析

目的 :探讨颈胸段脊柱肿瘤全脊椎切除的手术方式、脊柱重建策略及治疗效果。方法 :回顾性分析我院自2008年1月~2013年12月行全脊椎切除术治疗的颈胸段脊柱肿瘤病例11例,病理诊断包括骨巨细胞瘤5例,骨母细胞瘤1例,Ewing肉瘤1例,浆细胞性骨髓瘤1例,甲状腺滤泡型转移癌2例,前列腺转移癌1例。患者均有不同程度的胸背部疼痛,术前VAS评分为7.45±0.82分;脊髓损伤神经功能Frankel分级B级1例,C级3例,D级6例,E级1例。所有病例术前根据Tomita脊柱肿瘤外科分期评估均为间室外病变。4例C7~T1段肿瘤行一期前后联合入路全脊椎切除,前方钛网、钛板重建;7例T2~T4段肿瘤行单一后路整块全脊椎切除(TES),前方单纯钛网重建。两种术式后方均为钉棒系统重建。观察患者术中术后并发症以及脊柱重建稳定性情况。结果:手术时间298~573min,平均423.9min;术中失血量800~3800ml,平均2077ml。4例术中胸膜破裂,2例术后神经功能一过性下降,7例术中结扎病椎神经根,残留轻度胸前区不适。所有患者均获随访,平均随访34.7个月,1例前列腺转移癌患者死亡,其余均无局部复发。术后患者疼痛明显改善,VAS评分由术前7.45±0.82分下降至术后2.55±0.69分(P<0.05)。术后神经功能2例(术前D级1例,E级1例)保持原有水平,余均获得改善,均未出现内固定失败。结论:全脊椎切除治疗颈胸段脊柱肿瘤可以获得满意的局部控制,缓解疼痛,改善神经功能,应根据肿瘤位于颈胸段脊柱近端(C7~T1)或远端(T2~T4)而制定个体化手术方式及脊柱重建策略。     

新型3D打印个体化人工椎体在脊柱重建中的初步研究

目的探讨新型3D打印个体化人工椎体在脊柱重建中的优势,并对其重建效果进行临床评估。方法收集2017年1月至2018年12月行全椎体切除术后采用3D打印个体化人工椎体行脊柱重建的15例肿瘤患者的临床资料,其中男8例,女7例;年龄(39.5±13.4)岁(范围:20~57岁)。原发肿瘤12例,转移肿瘤3例。依据肿瘤位置及周围软组织侵及范围,采取单纯后路或前后路联合手术方式行全椎体切除,并进行3D打印人工椎体重建。分析手术时间、术中出血量、术后人工椎体稳定情况、与相邻椎体骨长入情况,手术前后神经功能改变情况、疼痛视觉模拟评分(visual analogue scale,VAS),局部控制情况及患者生存情况。结果本组15例的手术时间(412.0±166.1)min(范围:135~740 min);术中出血量(4140.0±3809.3)ml(范围:100~14000 ml);术后随访(23.2±7.0)个月(范围:12~35个月)。术前VAS评分(4.7±1.1)分,术后7 d(1.6±0.6)分,末次随访时(1.0±0.5)分,术后7 d及末次随访较术前的差异均有统计学意义(P<0.001)。术后7 d术前Frankel分级C级的3例逐渐恢复到D级,余12例D级和E级无变化,差异无统计学意义(Z=-1.732,P=0.083);术后末次随访时Frankel分级较术后7 d无明显变化。影像学表现:术后3个月时人工椎体与临近椎体已有初步的骨愈合;术后12个月时人工椎体和邻近椎体有大量骨连接形成,形成骨整合;术后24个月时可见人工椎体与邻近椎体骨整合更加确实。在随访期内人工椎体无松动移位,内固定无断裂失效。术中1例出现胸膜破裂,术后1例发生脑脊液漏,1例出现L5神经根麻痹,积极对症处理后均痊愈。1例血管内皮细胞瘤和1例上皮样血管肉瘤,分别于术后33个月和35个月死亡,1例软骨肉瘤术后16个月局部复发,服用安罗替尼治疗,肿瘤无进展,余12例无肿瘤复发及远处转移。结论利用3D打印个体化人工椎体对脊柱肿瘤切除后重建,有利于精确恢复脊柱连续性,提供更好的界面匹配,利于骨的长入,同时人工椎体植入后即刻及远期稳定性良好,可满足脊柱重建的需要。     

胸腰椎肿瘤整块切除后应用3D打印人工椎体重建的安全性和有效性研究

目的:评估胸腰椎肿瘤整块切除后应用3D打印人工椎体重建脊柱稳定性的安全性和有效性。方法:回顾性分析我院2016年5月～2020年1月胸腰椎肿瘤整块切除术后应用3D打印人工椎体重建脊柱稳定性的42例患者。原发性骨肿瘤37例;转移性肿瘤5例。肿瘤均累及胸腰椎。手术实施整块切除,均使用3D打印人工椎体作为前方支撑结构。根据随访超过6个月患者的X线片、CT片评估3D打印假体与相邻椎体融合情况、有无内固定失败。结果:全脊椎切除者39例,矢状切除者3例。使用标准化3D打印人工椎体19例,其中1节段者15例,2节段者3例,3节段者1例;从后路放置15例,从前方放置4例。使用定制化假体23例,其中单节段者7例,2节段者3例,3节段者10例,4节段者2例,5节段者1例;通过椎弓根螺钉拧入假体内置钉孔与后方钉棒系统连接达到自稳19例,从前路放置并通过内置钉孔用螺钉固定于相邻椎体者4例。40例患者获得随访,随访时间3～47个月,中位随访时间22个月。影像学随访超过6个月的患者36例,包含确定融合者9例,可能融合者19例,可能不融合者8例;均无螺钉断裂或拔出、连接棒断裂和假体断裂移位情况;总体融合率为77.8%(28/36)。2例假体下陷超过2mm,但症状轻微未行内固定翻修手术。结论:3D打印人工椎体较大的终板面积有利于防止假体塌陷;微孔结构能促进骨长入增加骨融合;定制化设计能使其与内固定系统连接或直接固定于相邻椎体从而获得更好的即刻稳定性。     

脊柱肿瘤的手术治疗

目的 :探讨对于脊柱肿瘤一期全脊椎切除及脊柱稳定性重建的手术方法和临床效果。方法 :对 12例脊柱肿瘤行前、后路或前、后联合入路Ⅰ期全脊椎切除、脊髓减压 ,椎间植骨融合、内固定术。结果 :术后 11例获得随访 ,按照Frankel分级较术前均有 1级以上提高 ,所有患者局部疼痛症状消失。术后复查平均植骨融合时间 3个月。1例脊索瘤术后 1年复发 ,1例巨细胞瘤术后 9个月复发。结论 :针对脊柱肿瘤的性质、部位 ,通过不同的手术入路行一期全脊椎切除、植骨融合内固定 ,彻底切除肿瘤 ,重建脊柱稳定性并体现了个体化的治疗方向     

脊柱肿瘤的全脊椎切除术及脊柱稳定性重建

目的探讨对脊柱肿瘤行全脊椎切除术的可行性与临床价值,以及重建脊柱稳定性的可靠方法。方法对27例椎体和附件结构均遭破坏的脊柱肿瘤采用全脊椎切除及内固定重建技术进行治疗,其中包括上颈椎至下腰椎的良、恶性及转移性肿瘤,手术切除1～3节脊椎。结果23例获完整随访,随访时间7～96个月(平均25个月)。1例L5恶性神经纤维瘤及1例C6,7巨细胞瘤于术后10个月及12个月复发,患者放弃治疗;1例C2～4脊索瘤术后1年复发,再次手术效果良好;其余20例未见复发。25例术前伴神经功能损害者,术后有23例获显著改善。结论全脊椎切除术为治疗全脊椎受累脊柱肿瘤的有效方法;切除1～3节脊椎的脊柱可由相应内固定系统进行可靠的稳定性重建。     

个体化定制3D打印假体枢椎前柱重建治疗枢椎肿瘤的疗效观察

目的 :观察应用个体化定制3D打印假体重建枢椎前柱治疗枢椎肿瘤的临床疗效。方法 :回顾性分析2018年12月～2019年10月我科应用个体化定制3D打印假体重建枢椎前柱治疗的6例枢椎椎体肿瘤患者的临床资料。其中男5例,女1例,年龄11～63岁,平均42.7±19.2岁。初次手术4例,其中脊索瘤2例,动脉瘤样骨囊肿1例,血管外皮细胞瘤1例;术后复发2例,均为脊索瘤。肿瘤累及椎体节段:C2节段5例,C2～C4节段1例。所有患者均行后前联合入路方式切除病变椎体。前路经口咽后壁入路5例,经下颌下咽后入路1例。所有患者均应用个体化定制3D打印颈椎假体行枢椎前柱重建。脊索瘤患者术后补充术区放疗。所有患者术后定期随访,观察肿瘤复发及内固定稳定性情况。结果:所有患者术中无神经、血管和硬脊膜损伤发生,术后患者伤口均一期愈合,无感染发生。术后平均随访11.8±3.7个月,未见肿瘤残留或复发,所有患者内固定稳定,未见螺钉松动及假体移位。结论:应用个体化定制3D打印假体能够有效重建枢椎前柱结构,获得满意的短期临床疗效。     

多节段胸椎软骨母细胞瘤整块切除后定制化3D打印人工椎体重建1例报道

正整块全椎切除是治疗脊柱良性侵袭性和恶性肿瘤的最佳方法~([1、2])。整块切除,特别是多节段整块全椎切除对脊柱的稳定性重建提出了严峻的考验。文献报道整块切除术后内固定的失败率可高达40%~([2～6])。3D打印人工椎体因其增大的接触面积和独特的人工骨小梁结构,明显降低了人工假体的塌陷率,提高了骨融合率~([7～9])。     

脊椎肿瘤的外科治疗

目的：探讨采用不同经路切除脊椎肿瘤与改进的人工椎体和自体植骨术治疗脊椎不同节段肿瘤的疗效。方法：对13例脊椎肿瘤采取切除瘤椎、人工椎体置换和自体植骨术;肿瘤包括颈椎4例,胸椎3例,腰椎6例。术前颈脊髓瘫痪1例,不完全瘫痪4例,肿瘤的术后病理学诊断有骨巨细胞瘤3例,骨囊肿、Ewing瘤、骨神经鞘瘤、软骨瘤、骨成纤维细胞瘤、骨纤维细胞瘤、骨嗜酸性肉芽肿、骨转移瘤、骨肉瘤和骨血管瘤各1例。结果：13例安全度过围手术期,无脊髓神经症状加重。除1例3个月恢复良好后失访外,余12例获平均4．3年随访,瘫痪5例完全恢复,12例均恢复家务和工作,X线片显示假体无松动、移位,植骨融合。结论：应根据肿瘤的脊柱节段和类型,选择手术治疗方式,采用人工椎体置换和自体植骨术,对完全切除脊椎肿瘤和重建脊椎稳定性是十分有益的。     

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.     

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.     

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.