不同颈椎内固定融合术式实验兔模型的建立

目的建立兔颈椎不同术式内固定融合模型。方法将60只新西兰白兔随机分3组,每组20只。A组行颈椎前路椎体间融合内固定术,B组行颈椎后路椎板棘突间融合内固定术,C组行颈椎前、后路联合融合内固定术。造模后1个月和3个月,每组10只行安乐死取材,分别摄X线片、作大体及组织形态学观察。结果随着时间的推移,X线片可见A、C组固定节段椎间隙逐渐融合、消失,B、C组固定节段椎板棘突融合。术后1个月标本见骨小梁、胶原纤维排列有序、规则,骨外膜侧尚有部分纤维组织,表明其有骨化及成骨现象;术后3个月标本见类似于正常椎体骨或椎板骨,胶原纤维折光性强,方向有序。结论建立兔颈椎内固定融合模型方法简单、易行、可靠,为脊柱疾病治疗方法研究提供良好的平台。     

组织工程椎间盘体内原位植入的实验研究

目的:观察组织工程椎间盘原位植入Beagle犬腰椎间盘后支架与种子细胞的转归及犬腰椎间盘的形态与功能变化。方法:应用聚乳酸聚酯(polyL-lactic-co-glycolicacid,PLGA)可吸收多孔支架复合犬髓核细胞构建组织工程椎间盘。将18只Beagle随机分为3组,均摘除L4/5椎间盘髓核,A组单纯髓核摘除,B组植入空白PLGA支架,C组植入组织工程椎间盘。术后定期行X线片及MRI检查,分别于术后4、8及12周处死动物行组织病理及免疫组化观察。结果:全部动物术后存活。4周后,X线片示3组椎间盘高度均有下降,C组下降幅度较小,与A、B组比较有显著性差异(P0.05);A组和B组手术节段屈伸活动度(ROM)明显大于C组(P0.05);MRI示A组与B组椎间盘退变明显,呈"黑间盘"改变,而C组椎间盘退变程度较轻,呈灰色,MRIT2加权像上椎间盘信号灰度值测量结果示A、B组明显低于C组(P0.05)。术后4周B、C组组织学观察未见到支架材料结构,A、B组椎间盘内纤维组织增生形成瘢痕样组织,C组于术后8周仍能观察到植入的红色荧光细胞,有大量类软骨细胞增生伴丰富的细胞外基质。术后8周免疫组化显示三组均有Ⅰ、Ⅱ型胶原着色,其中C组Ⅱ型胶原染色强度高于Ⅰ型,A、B组Ⅰ型胶原染色强度高于Ⅱ型。结论:PLGA组织工程椎间盘支架在体内可降解吸收;种子细胞可存活并分泌Ⅰ、Ⅱ型胶原,能阻止纤维组织侵入及瘢痕形成;维持了脊柱节段稳定及生理活动功能。     

可降解聚乳酸腰椎间融合器植骨融合成骨方式的研究

目的:探讨可降解聚乳酸腰椎间融合器实现椎体间植骨融合的成骨方式。方法:健康9月龄内江猪48只,随机分成两组:实验组24只,采用聚-DL-乳酸可降解腰椎融合器置入L4/5椎间隙并植骨;对照组24只,采用与融合器相同大小自体骨行L4/5椎间植骨。分别于1、3、6、9、12、18个月时取标本进行组织学检查。结果:术后1个月,实验组填充骨与融合器之间没有见纤维组织的长入,在融合器与骨之间可见少量软骨细胞存在;对照组植骨部位见软骨组织与纤维组织交错。术后3个月,实验组中融合器边缘与中央与填充骨和椎体骨接触部分可见明显的胶原纤维、纤维组织、软骨组织交互长入,软骨内化骨形成成熟的骨小梁,但排列很紊乱;对照组中软骨组织逐渐进化为骨组织,骨小梁排列较术后紊乱,部分已钙化成骨。术后6个月,实验组中残存融合器边缘及中空部分仍可见大量纤维细胞、软骨细胞,部分软骨组织已经成骨并钙化;对照组已达到良好的骨性融合。术后9个月,实验组已大部分融合,填充骨与椎体间的界限已消失,手术部位仍可见明显胶原、纤维组织,软骨细胞进化为骨细胞;对照组骨性融合,可见大量软骨组织和成熟板层骨形成。术后12个月,实验组基本达到骨性融合,仍可见明显软骨组织和纤维组织,对照组完全融合,且塑形良好。术后第18个月,两组均达到骨性融合,并且塑形良好接近周围正常骨组织。结论:生物降解可降解聚-DL-乳酸腰椎间融合器在猪的椎间成骨方式主要是软骨内成骨和纤维性成骨,膜内成骨不起重要作用。     

椎体终板的解剖与椎间植骨融合的相关性研究

目的：探讨椎体终板的解剖与椎间植骨融合的相关性。方法：5具新鲜成人脊柱标本，取C3－7、L1－5椎体各25个，光镜下观察终板结构。成年犬15只，随机在每只动物的L4－5和L6－7两个椎间隙构建保留终板和不促留终板的脊柱前路融合模型，术后4、8、12周分别切取新鲜融合脊柱节段，标本切片行光镜和电镜检查，观察两组植骨愈合进程。结果：终板中央区为多孔的松质骨样结构，该孔状空腔与终板的通透性有关。动物实验中，4例时保留终板组和对照组植骨区以纤维性骨痂为主，保留终板组稍多；12周时两组均获骨性愈合。结论：终板有特殊的层状孔结构，具有较大的通透性，保留终板对植骨愈合进程和骨愈合质量无影响。     

同种异体骨板覆盖预防硬膜外瘢痕粘连的实验研究

目的 探讨经冻干辐照处理后的同种异体骨板预防椎板切除术后硬膜外瘢痕粘连的作用。方法 12只成年雄性绵羊,随机分成A、B两组,每组6只。两组均作L3,4和L4,5椎板切除,A组的L4,5和B组的L3,4椎板缺损用“H”形同种冻干辐照骨板覆盖,为实验节段;A组的L3,4和B组的L4,5不覆盖骨板作为对照节段。于术后4、8、12、16、20和24周取材,行大体、X线平片和组织切片观察;并对4、24周取材行CT扫描。结果 术后4周,实验节段可见同种骨板形态、位置保持完好,椎管内无狭窄,硬膜囊无压迫,镜下椎板咬除缘有多量新生骨小梁生成,周边有大量软骨细胞及其分泌黏多糖和坏死后所留下的空腔,骨板内侧有增生纤维组织及少量炎性细胞浸润;对照节段可见大范围致密的纤维组织夹杂变性坏死肌肉嵌入椎板缺损处,硬膜广泛粘连,硬膜囊受压。术后24周,实验节段椎管重建基本完成,覆盖骨板吸收完全,并与再生椎板融合,椎管形态完好,硬膜外未见瘢痕组织;对照节段椎板再生未完成,瘢痕组织自椎管外嵌入椎管内,压迫硬膜囊及脊髓,硬膜外间隙几乎消失。统计学分析表明手术后期（16～24周）,实验节段与对照节段相比硬膜粘连程度明显减轻,椎管矢状径均较对照节段大,硬膜囊形状保持良好,无明显压迫。结论 同种异体冻干辐照骨板在实验羊椎板切除后的硬膜外能有效减少瘢痕形成和粘连。     

聚氨基酸/纳米羟基磷灰石/硫酸钙融合器在山羊腰椎椎间融合中的作用研究

目的探讨聚氨基酸/纳米羟基磷灰石/硫酸钙(poly-amino acid/nano-hydroxyapatite/calcium sulfate,PHC)融合器(Cage)在山羊腰椎椎间融合中的作用。方法 18只2岁龄雌性山羊,体重29~33 kg,随机分成PHC Cage组(A组)、钛合金Cage组(B组)及自体髂骨组(C组),每组6只,经腹膜外入路建立L3、4椎间融合模型。术后观察动物一般情况;于术前及术后4、12、24周行X线片检查,测量椎间高度(disc space heights,DSH),并于24周行CT三维重建进行改良Brantigan融合评分,明确椎间融合情况;处死动物获取L3、4标本,进行生物力学测试、组织学及扫描电镜观察。结果所有动物均存活至实验完成。各组术后4周DSH均较术前增高,之后呈下降趋势。其中A、B组手术前后各时间点比较差异均无统计学意义(P0.05),C组12、24周均显著低于术前(P0.05)。术前及术后4周,3组间比较差异均无统计学意义(P0.05);术后12、24周,A、B组DSH均显著高于C组(P0.05),A、B组间比较差异无统计学意义(P0.05)。CT三维重建示,A、C组均达骨性融合,B组仅3例达骨性融合;A、C组评分比较差异无统计学意义(P0.05),但均高于B组(P0.05)。生物力学测试示A、B组各方向活动度差异无统计学意义(P0.05),但均小于C组(P0.05)。组织学及扫描电镜观察示A组椎间融合良好,Cage表面微降解,Cage骨界面可见新生骨形成;B组Cage骨界面连接欠紧密,部分区域由纤维组织填充,Cage内部少量新生骨形成;C组髂骨植入区域与宿主骨连接紧密,椎间融合良好,界面未见明显缝隙。结论采用PHC Cage行山羊腰椎椎间融合效果优于钛合金Cage,与自体髂骨相似;其在体内表面微降解并与宿主骨紧密结合,但长期降解情况仍需进一步观察。     

纳米羟基磷灰石/聚酰胺66复合物椎间融合器在山羊颈椎融合中的应用

目的:观察纳米羟基磷灰石/聚酰胺66复合物(n-HA/PA66)椎间融合器在山羊颈椎前路融合中的效果。方法:15只成年雌性山羊随机分成A、B、C组,每组5只,均行经前路C3/4椎间盘切除术,A组椎间置入n-HA/PA66椎间融合器植骨;B组置入钛网植骨;C组采用自体三面皮质髂骨块植骨。分别于术前、术后、术后4周、8周及12周拍X线片观察测量各组手术节段平均椎间高度(disc space height,DSH)、椎间角(intervertebral angle,IVA)及前凸角(lordosis angle,LA);12周时处死动物取颈椎标本进行生物力学测试及组织学检查。结果:术前三组DSH、IVA和LA无显著性差异。术后即刻及术后4周三组间DSH无显著性差异(P0.05);术后8周及12周,A组DSH与B、C组有显著性差异(P0.05);B组和C组差别无显著性(P0.05)。术后即刻及术后4周、8周三组间IVA无显著性差异(P0.05);术后12周,A、B组IVA与C组有显著性差异(P0.05),A组与B组无显著性差异。术后即刻及术后4周、8周三组间LA差异无显著性(P0.05);术后12周,A、B组LA与C组有显著性差异(P0.05),B组与C组无显著性差异。术后12周时,A、B组颈椎标本各向角位移与C组有显著性差异(P0.05);除后伸外A组各向稳定性优于B、C组;平均刚度均强于B、C组;ROM均小于B、C组(P0.05)。A组在植骨区和椎间融合器边缘可见大量成熟的骨小梁组织,材料交界处可见大量纤维骨痂及新生骨形成,骨组织与材料表面已发生嵌合;B组的植骨块与椎体间的新生骨小梁已改建为成熟的骨小梁,部分区域尚可见未完全矿化的类骨质;C组可见较多的纤维骨痂形成,在骨小梁表面有红色的类骨质,部分区域有成熟的骨小梁。结论:n-HA/PA66椎间融合器能有效维持椎间隙高度,促进山羊颈椎前路植骨融合。     

犬椎间隙感染治疗的实验研究

目的探讨椎间隙感染前路病灶清除一期植骨内固定的可行性、安全性及疗效和病理转归。方法犬腰椎间隙内注射金黄色葡萄球菌建立椎间隙感染模型。监测肛温、ESR、CRP;术后2周摄腰椎正侧位X线片和MRI,证实椎间隙感染模型成功建立。32只建模成功的犬随机均分为4组。A组：抗生素治疗;B组：抗生素治疗＋前路病灶清除;C组：抗生素治疗＋前路病灶清除＋椎间植骨;D组：抗生素治疗＋前路病灶清除＋前路椎间植骨＋钢板内固定。治疗后3d及1、2、3周测肛温、ESR、CRP;12周摄X线片后处死,取椎间隙组织病理学检查和培养。结果A组：治疗3周后肛温、ESR及CRP下降缓慢,12周内死亡3只,存活5只未发现椎体间融合。B、C、D3组与A组比较：3周后肛温、ESR、CRP均下降迅速,差异有显著性（P〈0．05）。观察12周感染无复发,但B、C组出现脊柱后凸畸形各1只。12周后D组椎体间融合6只,与A、B、C组相比融合率升高（P〈0．05）,无脊柱畸形发生和感染复发。结论前路手术可彻底清除犬椎间隙感染病灶,一期植骨内固定无感染复发,融合率高,病理转归佳。     

颈椎自张式记忆合金椎间融合器山羊动物模型实验研究

目的建立颈椎自张式记忆合金椎间融合器山羊动物模型,比较其与三面皮质髂骨、钛网的融合效果及并发症。方法18只成年公山羊随机分为自体三面皮质髂骨（A组）、钛网（B组）、记忆合金椎间融合器（C组）3组,均行C4椎体次全切除植骨术,附加颈前路钢板内固定。术后即刻及12周摄颈椎X线片,术后12周取标本行组织学检查。结果A组出现1例髂骨血肿,B组出现1例不全瘫及1例钛网下沉,B组、C组出现1例切口感染。术后12周各组山羊颈椎获得放射学及组织学融合。C组山羊颈椎获得牢固的椎体间融合。结论颈椎自张式记忆合金椎间融合器可获得满意的融合效果,手术并发症较少。     

高纯度猪软骨Ⅱ型胶原修复兔膝关节软骨缺损的实验研究

目的 研制高纯度猪软骨Ⅱ型胶原海绵,探讨其修复关节软骨缺损的可行性.方法 将40只成年雄性新西兰兔制成膝关节软骨缺损模型,随机分成两组.A组20只兔的缺损区植入Ⅱ型胶原海绵,B组20只兔的缺损区旷置,不植入胶原作为对照.于术后2、4、8、12、24周分别做HE染色、Masson染色、Safranin O染色及Ⅱ犁胶原免疫组化检测.结果 ①HE染色及Masson染色显示A组在术后2周即出现新生软骨细胞,细胞以胶原纤维为支架迁移进入缺损区,并与胶原纤维生长融合;12周后新生骨和软骨组织完全填满缺损区并与周围组织整合,而B组直至术后24周仍由纤维组织所填充;②免疫组化检测结果 显示A组新生软骨细胞具有正常兔软骨细胞的表型;③Safranin O染色结果 显示A组新生软骨细胞具有分泌软骨基质的功能.结论 Ⅱ型胶原具有较强的诱导软骨细胞生长的能力,其诱导生长的新生软骨细胞具有正常透明软骨细胞的表型和功能,是良好的软骨缺损修复的生物填充材料.     

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.