骨髓间充质干细胞促进骨-肌腱结合部位早期愈合的动物生物力学实验研究

[目的]通过生物力学研究,观察骨髓间充质干细胞对骨-肌腱结合部愈合的影响.[方法]采用骨髓穿刺、全骨髓培养法获取兔骨髓间充质干细胞.24只18周龄新西兰大白兔随机分为2组,实验组将骨髓间充质干细胞与Pluronic F-127载体材料结合后,植入兔髌骨部分切除模型,对照组只进行手术,不植入细胞.在术后6、12、18周处死动物取标本(n=4)进行生物力学检测评估骨-肌腱结合部位的愈合恢复情况.[结果]生物力学结果显示相同时间点实验组拉断负荷及极限拉应力均大于对照组,差异有统计学意义(P<0.05),提示实验组恢复较对照组迅速.[结论]相同时间点实验组拉断负荷、极限拉应力均大于对照组.实验组的力学特性明显高于对照组.骨髓间充质干细胞可以促进骨-肌腱结合部细胞早期愈合,提高其力学特性.     

骨髓间充质干细胞对肌腱移植物在骨隧道内愈合效果及示踪的实验研究

[目的]观察骨髓间充质干细胞对肌腱移植物在骨隧道内愈合的影响,并为干细胞的标记示踪提供实验依据.[方法]采用贴壁分离筛选法获取大鼠的骨髓间充质干细胞(bone mesenchymal stem cells,BMSCs),用超顺磁性氧化铁(superparamagnetic iron oxide,SPIO)和DiI(1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate)对其标记.39只8周龄雄性SD大鼠随机分为两组,实验组21只,对照组18只.实验组在骨隧道内腱-骨结合面注入含双标的BMSCs和Pluronic F-127载体,对照组只注入载体,术后2、4、8周进行生物力学评估愈合效果,实验组2、4、8周组织冰冻切片荧光显微镜和手术后即刻、3、7 d行7.0 T MR示踪移植的BMSCs.[结果]SPIO、DiI能有效标记干细胞.实验组2、4、8周荧光显微镜观察在腱骨界面有DiI标记的阳性细胞存在.7.0 T MR未能在实验组腱骨界面观察到明显信号改变.生物力学最大拔出载荷实验组和对照组在术后2周无统计学差异,在4、8周实验组显著高于对照组(P<0.05).[结论]移植的骨髓间充质干细胞可以促进骨隧道内腱骨结合部的早期愈合,DiI能有效标记示踪干细胞,SHO能有效标记干细胞,但在该实验模型中7.0T MR可能不能活体示踪磁粒子标记的干细胞.     

骨膜促进骨-肌腱结点愈合的研究

[目的]探讨骨膜对骨-肌腱结合部位愈合的影响,通过实验证明骨膜促进骨-肌腱结合部位细胞增生,进而促进该部位愈合.[方法]48只18周龄新西兰大白兔随机分为2组,实验组将骨膜游离并植入兔髌骨部分切除模型中骨-肌腱结点中,对照组只进行手术,不植入骨膜.在术后4、8、12周处死动物取标本进行大体和组织学观察.[结果]大体观察可见实验组骨-肌腱结合部位愈合较早.组织学检查显示实验组术后4、8周骨-肌腱结合部组织愈合明显,以从松质骨再生和骨-肌腱愈合接点纤维软骨带的再生为特征,较对照组迅速,提示早期实验组恢复较对照组迅速.[结论]骨膜可以促进骨-肌腱结合部位细胞增生,增加细胞基质合成,促进新生骨和纤维软骨移行带形成,促进其愈合.     

骨髓间充质干细胞及其复合物对肌腱早期愈合影响的实验研究

[目的]探讨骨髓间充质干细胞(BMSCs)与纤维蛋白胶复合体对兔肌腱早期愈合的影响,为临床应用提供依据.[方法]家兔骨髓间充质干细胞离体培养、纯化、扩增后与纤维蛋白胶混合.36只家兔分为实验组和对照组,兔跟腱横断制作肌腱断裂模型.实验组应用自体BMSCs复合纤维蛋白胶移植于肌腱损伤区,对照组仅以纤维蛋白胶置于肌腱损伤区.分别于术后1周,3周,6周及12周对移植部位进行大体标本观察,细胞示踪、组织学检查、免疫组织化学检查、形态测定分析及生物力学测定.[结果]实验组相比对照组肌腱大体观察粘连差,肌腱活动性好.3周后纤维蛋白载体即降解,细胞示踪结果显示标记的骨髓间充质干细胞至少6周内仍可保持活性并存在于肌腱组织中,但之后逐渐扩散.3周时,实验组与对照组相比胶原纤维排列更为有序,且胞核形态结构更规则,但在6周及12周时,实验组与对照组胞核参数测定无统计学意义.3周时实验组比对照组具有更强的的生物力学特性,但之后则差别不明显.[结论]肌腱损伤后即给以腱内BMSCs复合纤维蛋白胶治疗可促进肌腱愈合早期组织形态学及生物力学修复.     

应用重组合异种骨促进前交叉韧带重建术后腱-骨愈合的研究

[目的]通过影像学、组织学及生物力学手段探讨重组合异种骨(RBX)对前交叉韧带重建术后腱-骨愈合的影响.[方法]25只新西兰白兔,利用双侧趾长伸肌肌腱重建前交叉韧带(ACL),其中一侧移植物两端固定有RBX,另一侧作为对照组,分别于术后2、6、12周取材,进行Micro-CT扫描,组织学染色(包括HE、甲苯胺蓝)以及生物力学检测,观察腱-骨之间愈合状况.[结果]影像学结果显示,术后6、12周RBX治疗组腱-骨之间的骨矿化组织密度(BMD)数值均高于对照组,并具有显著性差异;组织学结果显示,术后2周,RBX组腱-骨之间被大面积不规则分布的软骨样细胞填充;术后6周,治疗组的腱-骨之间已见大量成熟软骨细胞,并开始分泌基质.而对照组术后腱-骨间一直被纤维样结缔组织连接,至术后12周,治疗组部分标本出现类ACL正常肌腱止点.生物力学结果同样证实,RBX组的最大牵拉力均显著高于对照组.[结论]RBX可显著提高ACL重建术后腱-骨之间的愈合,较早恢复膝关节功能.     

放射性核素骨显像动态检测组织工程化骨血管化的价值

[目的] 放射性核素骨显像动态检测评价组织工程化骨血管化与骨代谢的价值.[方法] 取大白兔24只,抽取骨髓,行骨髓间充质干细胞分离、培养与骨向诱导.双侧股骨髁制作0.6 cm×1.2 cm的骨缺损,将诱导后的骨髓间充质干细胞与珊瑚羟基磷灰石复合植入左侧骨缺损处为实验组,右侧单纯植入珊瑚羟基磷灰石为对照组.术后4、8、12周分别行静态放射性核素骨显像检测,用ROI计数计算不同时间点的ROI平均计数.[结果] 结果术后4、8、12周实验组ROI计数(单位像素)均较对照组有显著性增高.实验组ROI计数随时间的延长,呈明显的上升趋势,术后8周开始增长放缓;对照组ROI计数术后8周增长缓慢,8周后开始增长加快,两组均在12周达到峰值.[结论] 骨髓间充质干细胞诱导后与珊瑚羟基磷灰石复合可有效的修复股骨髁松质骨缺损.放射性核素骨显像可动态检测组织工程化骨血管化及骨代谢变化.     

兔自体骨膜包裹同种异体肌腱移植对腱-骨愈合的影响

目的 探讨兔同种异体肌腱表面包裹自体骨膜植入骨隧道对移植肌腱与骨隧道之间界面愈合的影响. 方法 健康4～5月龄新西兰白兔20只,体重2.5～3.0 kg,随机取一侧后肢作为实验组,另一侧后肢作为对照组.以同种异体肌腱在兔胫骨干骺端建立腱-骨固定模型,实验组骨隧道肌腱表面包裹自体骨膜,骨膜生发层朝向骨隧道;对照组骨隧道肌腱表面不包裹自体骨膜.分别于术后4、8周取标本作腱.骨界面的组织学检查(n=2),并进行最大拔出负荷的生物力学测试(n=8). 结果 术后4、8周标本大体观察,实验组骨隧道口周围新生骨较多;对照组新生骨少或不明显.组织学观察:术后4周实验组骨膜生发层内有大量间充质细胞增生,出现明显的膜内成骨,沿新生骨小梁周围可见大量骨母细胞呈栅形排列,新生骨小梁与骨膜延续:对照组腱-骨界面间无明显新生骨形成,有疏松结缔组织填充,腱-骨间连接较疏松.术后8周实验组新生骨和肌腱与骨隧道连接紧密,无间隙,新生骨量多,新生骨排列比较规则、整齐,腱-骨界面可见潮线形成,类似于正常腱-骨附着结构,骨膜内成纤维细胞增殖活跃,骨膜与肌腱间有较多纤维连接;对照组腱-骨界面局部有新生骨形成,排列紊乱,腱-骨间可见较多胶原纤维连接.术后4、8周,实验组最大拉出或拉断强度分别为(35.03±1.21)N/cm和(42.36±1.31)N/cm,对照组分别为(26.14 ±6.13)N/cm和(31.63±6.87)N/cm,两组比较差异均有统计学意义(P<0.05). 结论 兔自体骨膜包裹同种异体肌腱移植可缩短腱-骨间成骨时间,提高愈合强度,加速腱-骨间愈合.     

肌腱-骨块自体复合移植物嵌压固定法重建前交叉韧带的实验研究

[目的]研究肌腱-骨块自体移植物嵌压固定法重建前交叉韧带的组织形态学转归.[方法]以8只山羊膝关节为实验模型,用阶梯状联合钻1次成形建立股骨隧道呈倒置瓶颈状,以髌腱-胫骨结节骨块为移植物,在股骨隧道内行嵌压固定;在胫骨端骨桥打结固定.术后4、8、12和16周取材,分别进行放射学、大体形态和组织切片检查,观察隧道宽度变化及移植物的组织学转归.[结果]术后各时间点放射检查未见隧道扩大;HE染色检查显示12周后有明显的腱-骨连接形成,移植骨块与隧道形成骨性愈合.[结论]嵌压固定法重建前交叉韧带有利于移植物的愈合.     

骨形态发生蛋白2基因修饰自体骨髓间充质干细胞移植促进兔胫骨牵张成骨的实验研究

[目的]观察人骨形态发生蛋白2基因修饰的自体骨髓间充质干细胞移植对兔胫骨牵张成骨新骨形成的促进作用。[方法]48只新西兰白兔随机摸球法分为3组。建立牵张成骨动物模型,在固定期第2 d,实验组于牵张间隙注射人骨形态发生蛋白2基因修饰的自体骨髓间充质干细胞;对照组注射等量自体骨髓间充质干细胞;空白组不注射任何物质。[结果]在固定期2周及6周实验组牵张区在大体观察、HE染色、X线观察方面成骨质量均好于对照组和空白组。12周后取牵张成骨区标本作骨组织骨密度和生物力学测定,结果显示实验组新生骨质量较高,骨愈合情况要优于对照组和空白组。[结论]骨形态发生蛋白2基因修饰的自体骨髓间充质干细胞移植能有效提高兔胫骨牵张成骨新骨形成质量。     

自体肌腱加富血小板血浆重建比格犬前交叉韧带的实验研究

目的研究应用自体肌腱添加富血小板血浆重建比格犬前交叉韧带的早期组织学转归及生物力学变化。方法选用健康成熟的雄性比格犬36只,随机分为两组(模型组和实验组),将每组比格犬36个膝关节分别取同侧趾长屈肌腱进行单束双股重建,实验组添加自体富血小板血浆。术后第4、8、12周每组随机抽取6只比格犬处死,分别取12个膝关节(包括股骨端与前交叉韧带),每组随机取8个膝关节做生物力学拉脱试验,另4个膝关节标本进行组织学检查,并对实验数据进行统计学分析。结果组织学观察模型组术后4周时,腱骨界面有纤维血管形成,实验组腱骨界面纤维血管更加密集,排列较有序并有少量Ⅱ型胶原纤维。术后8周模型组有肌腱周围的新骨形成,骨隧道壁增厚。但在此期间,胶原纤维机化不充分,腱骨的连续性偶尔可见;实验组胶原纤维生长成熟,可见腱骨的连续性,并在腱骨界面中心出现少量垂直排列的Sharpey样纤维。术后12周模型组可见少量垂直排列的Sharpey样纤维;实验组腱骨界面可见大量的垂直排列的Sharpey样纤维,此时腱骨愈合已逐步趋于稳定。生物力学测试显示术后第4、8周,两组肌腱都能从骨隧道里拉脱出来。在第12周时,模型组仍可以从骨髓道里被拉脱;实验组肌腱均不能从隧道中被拉出,而是在肌腱中间断裂。结论应用自体肌腱可以重建比格犬前交叉韧带并达到腱骨愈合,添加富血小板血浆可以加快腱骨愈合的速度。     

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.     

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.     

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.     

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.     

Systemic analgesia adapted to the children's condition

A concept of balanced analgesia using nonsteroidal anti-inflammatory drugs (NSAIDs), paracetamol (acetaminophen), opioids, and corticosteroids can also be used in patients with pre-existing illnesses. NSAIDs are the most effective treatment for acute pain of moderate intensity in children; however, these drugs should be avoided in patients at increased risk for serious side effects, e.g. patients with renal impairment, bleeding tendency, or extreme prematurity. NSAIDs can be given with minimal risks to the younger child with mild to moderate asthma, and, in these patients, the use of steroids can be encouraged; in addition to their antiemetic and analgesic action, a beneficial effect on asthma symptoms can be expected. In the non-intubated child with cerebral trauma, exaggerated sedation caused by opioids and increased bleeding tendency caused by NSAIDs must be avoided. In neonates and small infants, the oral administration of sucrose or glucose is helpful to minimize pain reaction during short uncomfortable interventions.     

Intraoperative autotransfusion is associated with modest reduction of allogeneic transfusion in prosthetic hip surgery

Background: The efficacy of intraoperative salvage and washing of wound blood and the predictors of allogeneic red cell transfusions in prosthetic hip surgery are insufficiently known.
Methods: In 96 patients, undergoing primary or revision surgery, salvaged and washed red cells and, if necessary, allogeneic blood were used to keep haematocrit not lower than 33%. The bleeding of red cells during hospital stay was calculated from the red cell balance. The preoperative red cell reserve (millilitres of red cells in excess of a haematocrit of 33%) was estimated and the difference between this volume and the total bleeding of red cells was retrospectively used to classify patients with regard to the need for red cells. Stepwise regression analysis was used to define patient-related variables associated with allogeneic blood transfusion.
Results: Preoperative knowledge of the type of operation (primary, revision), the preoperative red cell reserve, and the body mass could predict roughly half of the need for banked blood (r²=0.45). Only one-third of the total bleeding of red cells was retransfused. For complete avoidance of allogeneic blood, autotransfusion was most effective in patients with a moderate need (0–4 u). However, 32% of such patients required allogeneic blood.
Conclusions: Autotransfusion has a limited efficacy to decrease the need for allogeneic blood, and other blood-saving methods should be added for this purpose. It is difficult to predict the need for allogeneic blood preoperatively.     

缺氧对肾小管上皮细胞分泌外泌体的影响

目的    观察缺氧对肾小管上皮细胞分泌外泌体的影响,探讨外泌体在缺氧致肾脏损伤中的作用及机制。 方法    （1）常氧（21% O₂）及缺氧（1% O₂）分别处理大鼠肾小管上皮细胞（NRK-52E）48 h,收集细胞上清液并使用高速梯度离心法分离外泌体。采用透射电镜、纳米示踪分析、Western印迹、蛋白浓度定量鉴定并比较两组外泌体的基本特性。（2）在共培养实验中,以不同浓度（1、10、50、100、300 mg/L）的常氧外泌体、缺氧外泌体分别干预脂多糖（LPS）诱导的大鼠原代腹腔巨噬细胞,使用实时荧光定量PCR与酶联免疫吸附试验（ELISA）法分别检测巨噬细胞白细胞介素6（IL-6）、肿瘤坏死因子α（TNF-α）、诱导型氮氧化物合酶（iNOS）水平;使用Western印迹法检测巨噬细胞磷酸化（p）STAT/STAT及细胞因子信号传导抑制蛋白1（SOCS1）的蛋白表达;最后,使用实时荧光定量PCR法检测常氧外泌体与缺氧外泌体中炎性反应相关微RNA（microRNA,miR）的表达差异。 结果    （1）离心得到的囊泡具有外泌体典型的结构,粒径小于150 nm,表达外泌体标志蛋白CD63,说明分离得到外泌体。缺氧对肾小管上皮细胞分泌的外泌体形态、粒径分布比例无明显影响,但提高了外泌体的分泌量。（2）缺氧外泌体相比于常氧外泌体促进了LPS诱导的M1型巨噬细胞IL-6、TNF-α、iNOS 的表达和分泌（均P＜0.01）,同时提高STAT的磷酸化水平并减少SOCS1的蛋白表达（均P＜0.01）;对炎性反应相关microRNA检测发现缺氧外泌体中miR-155、miR-27a表达量较常氧外泌体明显升高（P＜0.05）。 结论    缺氧可改变外泌体的生物学功能,表现为协同促进LPS诱导的M1型巨噬细胞的表型转化,这可能是慢性肾脏病微炎性反应状态持续的原因之一。     

In Vitro Function and Durability Assessment of a Novel Polyurethane Heart Valve Prosthesis

Abstract While flexible-leaflet, central-flow prosthetic heart valves promise relief from anticoagulation therapy, they continue to be restricted by inadequate durability. In consequence, a novel trileaflet valve, made entirely from polyurethane, has been developed. A batch of 6 consecutively manufactured polyurethane valves was subjected to hydrodynamic function and accelerated fatigue testing. Computerized data acquisition and control systems have been introduced to improve valve testing methodologies. In terms of hydrodynamic function, the polyurethane valve demonstrates transvalvular pressure gradients similar to those for a bioprosthetic valve (Carpentier-Edwards) and levels of retrograde flow significantly less than those for either the bioprosthetic valve or a bileaflet mechanical valve (St Jude Medical). The equivalent of 10 years of cycling without failure has been exceeded by all 6 polyurethane valves in accelerated fatigue tests with 2 valves remaining intact after 674 million cycles (equivalent to approximately 17 years) in continuing tests. Highspeed photography revealed considerable differences in leaflet motion between valves cycled at accelerated and physiological rates.     

Negative pressure ventilation vs. spontaneous assisted ventilation during rigid bronchoscopy: A controlled randomised trial

Background: Ventilation during interventional rigid bronchoscopy (IRB) under general anaesthesia (jet ventilation, positive pressure ventilation and spontaneous assisted ventilation) may offer some difficulties. This study compares the effectiveness during IRB of intermittent negative pressure ventilation (INPV) and spontaneous assisted ventilation (SAV). Methods: Thirty-eight patients submitted to IRB were randomised into two groups: SAV or INPV. All patients received a total intravenous anaesthesia; INPV patients were paralysed. Pre-and intra-operative arterial blood gases and O₂ flow through a rigid bronchoscope were assessed. The endoscopist applying a subjective score evaluated the operating conditions. Results: Patients of the INPV group, as compared to the SAV group, required a lower dosage of fentanyl (2.6 ± 1.8 (μg · kg^?1· h^?1 vs. 6.6 ± 4.8 μg · kg^?1· h^?1), a lower O₂ supply (3.3 ± 2.8 1/min vs. 11.6 ± 3.4 1/min), a shorter recovery time (5.4 ± 2.9 min vs. 9.8 ± 7.1 min) and no manually assisted ventilation (0 ± 0 vs. 1 ± 1.1 nd?/procedure). Intraoperative PaCO₂ was higher in the SAV (8.1 ± 1.3 kPa) than in the INPV group (5.0 ± 1.6 kPa) and intraoperative pH differed in the two groups (7.26 ± 0.05, SAV vs. 7.47 ± 0.08, INPV). Operating conditions, as assessed by a subjective score, were considered better with INPV than with SAV (4.9 vs. 4.3). Conclusions: As compared to SAV, INPV in paralysed patients during IRB reduces administration of opioids, shortens recovery time, prevents respiratory acidosis, excludes the need for manually assisted ventilation, reduces 02 need and affords optimal surgical conditions. INPV appears a safe, non-invasive and effective ventilatory management during IRB.