血栓弹力图预测髋膝关节置换术后血液高凝状态的价值分析

目的分析血栓弹力图(thromboelastography,TEG)预测髋膝关节置换术后病人血液高凝状态的价值。方法前瞻性纳入2019年3月至2019年12月于重庆医科大学附属第一医院拟行髋膝关节置换的204例病人,分析病人围术期的反应时间(R值)、血块形成时间(K值)、血块形成速率(α角)、最大振幅(MA值)、凝血指数(CI)的变化,评估TEG在诊断高凝状态方面与常规凝血试验的差异性和一致性,分析术后血液高凝的危险因素。结果相对于常规凝血试验,TEG诊断高凝状态的阳性率更高(P<0.001),两者具有一定的相关性和一致性。R值与国际标准化比值(international normalized radio,INR)、血小板计数(platelet counts,PLT)呈负相关,与活化部分凝血酶原时间(activated partial thromboplastin time,APTT)呈正相关;K值与PLT呈负性相关;α角与纤维蛋白原(fibrinogen,FIB)、PLT呈正相关;MA值与FIB、PLT呈正相关;CI值与FIB、PLT呈正相关,与D-二聚体(D-Dimer,D-D)呈负相关。术前高凝病人术后第1、3、5天的血液高凝发生率明显高于术前凝血功能正常者,差异均有统计学意义(P均<0.05)。根据术后第5天TEG诊断的凝血状态,年龄≥65岁[OR=8.938,95%CI(3.917,20.397),P<0.001]、围术期输血[OR=12.379,95%CI(5.304,28.893),P<0.001]是髋膝关节置换术后血液高凝的独立危险因素。结论TEG是预测术后高凝的有效指标,对于指导髋膝关节置换围术期个体化抗凝具有重要意义。     

肝硬化门静脉高压症脾切除术后发生门静脉血栓的风险因素及其预测模型的建立

目的:分析肝硬化门静脉高压症脾切除术后门静脉血栓(PVT)形成的危险因素并建立PVT发生的Logistic回归预测模型。方法:对符合入选标准的236例脾切除术患者围术期相关临床因素进行单因素及多因素Logistic回归分析,根据多因素分析结果建立Logistic回归预测模型,计算Logit P并绘制各独立因素预测术后PVT的ROC曲线。结果:多因素结果分析显示术前门静脉血流速度(VPBF)、术后平均血小板体积(MPV)、术后D-二聚体(D-D)、术中门静脉自由压力差(FPPD)为术后发生PVT的独立危险因素,术后使用抗凝药物(UAT)为术后发生PVT的独立保护因素(均P0.05)。根据上述指标建立Logistic回归预测模型为Logit P=5.715-0.558×VPBF(cm/s)+0.592×MPV(f L)+0.707×D-D(mg/L)+0.573×FPPD(cm H_2O)-0.872×UAT(是=1,否=0),Logit P的临界值为-0.96,ROC曲线下的面积为0.898,准确度为86.9%,VPBF、MPV、D-D、FPPD所对应的界值点分别为13.85 cm/s、10.92 f L、3.54 mg/L、6.99 cm H_2O。结论:VPBF≤13.85 cm/s、MPV≥10.92 f L、D-D≥3.54 mg/L、FPPD≥6.99 cm H_2O可增加脾切除术后PVT的发生风险,术后UAT可有效减少PVT的发生;所构建的预测模型对判断此类患者术后PVT形成有较高的准确度,有一定的临床参考价值。     

腹腔镜胆囊切除术对老年原发性高血压患者血凝状态的影响

目的:比较老年原发性高血压患者开腹胆囊切除术和腹腔镜胆囊切除术对血凝状态和血栓形成危险的影响。方法:LC32例,OC23例。均于术前、术后24h留取静脉血标本,检测部分凝血活酶时间(APTT)、D-二聚体(D-D)、血管性血友病因子(VWF)及其抗原(VWFag)和纤维蛋白原(FG),对上述凝血指标用SPSS10软件包行独立样本的t检验。结果:术前两组结果均接近正常范围,组间比较差异无统计学意义(P>0.05)。术后两组病人的所选血凝指标均大于正常值,其中APTT和VWF组间比较差异无统计学意义(P>0.05),而VWFag、D-D和FG的指标LC组较OC高,组间比较差异有统计学意义(P<0.05和P<0.01)。结论:老年原发性高血压病人行LC后,其较OC后存在着更明显的血液高凝状态和潜在血栓形成危险,这种状态和危险随着LC手术时间的延长而可能有所增高。     

羟考酮抑制老年患者腹腔镜下胆囊切除术瑞芬太尼静脉复合麻醉苏醒期疼痛的半数有效量

目的 探讨羟考酮抑制老年患者腹腔镜下胆囊切除术瑞芬太尼静脉复合麻醉苏醒期疼痛的药效学. 方法 选择拟在全身麻醉下行腹腔镜胆囊切除术患者32例,年龄65～74岁,ASA分级Ⅰ、Ⅱ级.麻醉诱导:依托咪酯0.3 mg/kg,瑞芬太尼采用Minto模型靶控输注(target controlled infusion,TCI),效应室浓度为3.0μg/L.待BIS值在40～45后,静脉注射顺式阿曲库铵0.2 mg/kg,5 min内完成气管插管行机械通气.术中除瑞芬太尼外,不再追加任何镇痛药物,麻醉维持分别TCI丙泊酚(3.0 μg/L)、瑞芬太尼(2.5～3.0 μg/L).手术结束时停用丙泊酚、瑞芬太尼.手术结束前5 min采用改良序贯法静脉注射羟考酮.拔管后30 min测定患者术后VAS评分,VAS评分≥4分为术后急性疼痛.计算羟考酮ED50及其95％可信区间(confidence interval,CI),并记录手术时间、术后拔管时间及恶心、呕吐等副作用. 结果 羟考酮抑制老年患者腹腔镜下胆囊切除术瑞芬太尼静脉复合麻醉苏醒期疼痛的EDs及其95％CI分别为0.126 mg/kg和0.093～0.181 mg/kg.32例患者术后有1例发生恶心、呕吐,无其他副作用发生. 结论 羟考酮(0.126 mg/kg)可以抑制半数老年患者腹腔镜下胆囊切除术瑞芬太尼静脉复合麻醉苏醒期的疼痛.     

腹腔镜胆囊切除术并发症相关因素分析

目的 探讨导致腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC)并发症发生的危险因素。方法 回顾分析我院自1991年3月-2003年6月间11974例腹腔镜胆囊切除术患者中发生并发症的临床资料,采用X~2检验和Logistic回归方法对可能导致腹腔镜胆囊切除术并发症发生的15个临床病理相关因素,进行多因素回归分析。结果 本组资料LC术后并发症的发生率为1.896％(227/11 974),中转手术率为2.386％(286/11 974),其中因发生并发症而中转开腹65例,占22.727％(65/286)。Logistic回归分析显示,按作用强度,Calot三角粘连、病期、手术经验、胆囊壁厚度(B超)、胆囊与周围粘连依次为导致腹腔镜胆囊切除术并发症发生的主要危险因素。结论 加强医师的腹腔镜技术培训,正确掌握LC相关危险因素是提高LC手术成功率的关键,正确掌握中转开腹的时机及开腹后处理方法,是降低LC手术严重并发症发生和死亡的有效措施。     

腹腔镜胆囊切除术后血液凝固性改变

目的 近年腹腔镜胆囊切除术(LC)后静脉栓塞性并发症报告日见增多，本文从血液凝固性角度探讨其发生机制。方法 观察施行LC患者术后血液凝固性改变，并以开腹胆囊切除组资料作为对照。结果 LC术后平均血小板体积．纤维蛋白原水平及P-选择素．凝血酶敏感蛋白表达阳性血小板比率明显增高。对照组术后凝血酶原时间，激活的部分凝血活酶时间均显著延长．LC组无明显改变，结论 LC术后患者血液处于明显高凝状态。提示对有血栓形成倾向的患者应采取抗凝措施．以预肪血栓栓塞性并发症发生。     

格拉斯哥预后评分对腹腔镜胃结直肠癌根治术近期临床结局的预测意义

目的:研究格拉斯哥预后评分(Glasgow prognostic score,GPS)对腹腔镜胃结直肠癌根治术后近期临床结局的预测意义。方法:回顾分析2014年6月至2016年3月接受腹腔镜胃结直肠癌根治术的226例患者的临床资料,根据术前外周血C反应蛋白(C reactive protein,CRP)、血清白蛋白(albumin,ALB)水平将患者分为3组,GPS 0组(CRP≤10 mg/L且ALB≥35 g/L)、GPS 1组(CRP10 mg/L或白蛋白35 g/L)与GPS 2组(CRP10 mg/L且白蛋白35 g/L),对比分析3组患者的临床资料、术后并发症及近期生存情况。结果:3组患者年龄、术前合并慢性病、肿瘤标志物、肿瘤TNM分期差异有统计学意义(P0.05),性别、肿瘤部位、体质指数差异无统计学意义(P0.05)。3组患者术后并发症发生率、术后近期生存曲线差异有统计学意义(P0.05)。结论:GPS可作为预测腹腔镜胃结直肠癌根治性手术的预后参考指标,GPS评分高的患者预后可能较差。     

腹腔镜胰十二指肠切除术后胰漏的相关因素分析

目的探讨腹腔镜胰十二指肠切除术后B、C级胰漏发生的预后因素。方法回顾性分析2016年12月～2018年6月83例腹腔镜胰十二指肠切除术的临床资料,对可能与B、C级胰漏有关的围手术期因素进行分析。单因素分析采用χ~2检验,有统计学意义的因素采用非条件logistic回归分析进行多因素分析。结果 83例中11例(13.3%)发生术后B、C级胰漏,其中B级9例(10.8%),C级2例(2.4%)。logistic回归多因素分析显示,术前总胆红素≥171μmol/L (OR=4.636,95%CI:1.080～19.894,P=0.039)、胰腺质地柔软(OR=0.202,95%CI:0.047～0.866,P=0.031)与B、C级胰漏的发生密切相关。BMI≥25(OR=22.347,95%CI:1.462～341.501,P=0.026)、术后未应用生长抑素(OR=0.071,95%CI:0.006～0.799,P=0.032)是胰腺质地柔软患者术后B、C级胰漏发生的相关因素。BMI≥25 (OR=13.474,95%CI:1.258～144.322,P=0.032)、术前采取减黄措施(OR=0.057,95%CI:0.005～0.638,P=0.020)是术前总胆红素≥171μmol/L患者术后B、C级胰漏发生的影响因素。结论胰腺质地柔软及术前总胆红素≥171μmol/L与腹腔镜胰十二指肠切除术后B、C级胰漏发生密切相关。BMI≥25时,此类患者B、C级胰漏发生风险明显增加。当术前总胆红素≥171μmol/L时,宜术前采取减黄措施。对于胰腺质软者,预防性应用生长抑素可在一定程度上降低腹腔镜胰十二指肠切除术后B、C级胰漏发生风险。     

腹腔镜胆囊切除术血液高凝状态的研究

我们于 2 0 0 1年检查了 4 1例腹腔镜胆囊切除术 (LC)和19例开腹胆囊切除术 (opencholecystectomy ,OC)患者术后2 4h的血栓前高凝状态指标 ,报告如下。材料与方法1.一般资料 :LC组 4 1例 ,男 16例 ,女 2 5例 ,年龄 2 7～72岁 ,平均 (4 8± 12 )岁 ;OC组 19例 ,男 5例 ,女 14例 ,年龄2 9～ 71岁 ,平均 (4 9± 13)岁。两组的入选标准均为缓解期的胆囊结石和胆囊息肉 ,既往无血管栓塞、动脉硬化、高血脂、冠心病等导致血栓形成的高危因素 ,选择OC者为经济条件不佳或对腹腔镜技术有顾虑者 ;LC组手术时间为 30～ 16 5min ,平均 (6 4± 36 )m…     

LC术中胆道损伤的危险因素及预防分析

目的:探讨腹腔镜胆囊切除术(LC)胆管损伤的危险因素及患者的预后。方法:回顾分析4 532例腹腔镜胆囊切除术患者的临床资料,对出现胆管损伤患者相关影响因素进行单因素分析,并分析胆管损伤的独立危险因素。结果:4 532例腹腔镜胆囊切除术患者中发生术后并发胆管损伤者19例,发生率为0.42%,单因素分析结果显示观察组患者处于急性期、胆囊壁增厚、解剖变异和术者经验少的比例均明显高于对照组(P<0.05)。经回归分析,解剖变异和术者经验是发生胆管损伤的独立危险因素(P<0.05)。结论:胆管损伤是严重的LC后并发症,解剖变异和术者经验少是影响其发生的独立危险因素。     

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.