风湿性心脏病瓣膜置换术中单极射频消融术治疗永久性心房纤颤的远期疗效及影响因素分析

目的分析风湿性心脏病瓣膜置换术中行单极射频消融改良迷宫术治疗永久性心房纤颤(房颤)术后远期疗效及其影响因素。方法回顾性分析2004年10月至2010年12月青岛大学附属医院116例同期行瓣膜置换及单极射频消融术的风湿性心瓣膜病合并永久性房颤患者的临床资料,其中男43例、女73例,年龄(50.5±7.5)岁;收集患者术后即刻、出院时、术后3个月、6个月、1年及随后每年的12导联心电图及超声心动图结果,并且记录术后并发症、心功能及生活质量改善情况等。根据末次随访时心电图结果,将患者分为房颤消除组(窦性心律+结性心律)与房颤组,其中房颤消除组52例(男16例、女36例),年龄(48.4±7.3)岁;房颤组50例(男22例、女28例),年龄(51.9±7.1)岁。分析影响术后远期效果的因素。结果住院期间死亡3例(1例因溶血、急性肾功能不全、高钾血症死亡,1例因急性肾功能不全引发多脏器功能不全死亡,1例因反复室性心动过速、心室颤动致多脏器功能不全死亡)。全组随访3~9年,随访期间死亡3例(1例因瓣周漏于外院行二次手术后死亡,余2例原因不详),失访8例,共有效随访102例(90.3%)。随访中,房颤组有1例患者出现脑栓塞,1例出现脑出血。单因素分析显示房颤消除组与房颤组在患者年龄、术前房颤病程、左心房内径、体外循环时间及升主动脉阻断时间方面差异均有统计学意义,是影响手术效果的因素;多因素分析显示年龄及术前左心房内径是影响手术效果的危险因素。结论瓣膜置换术中单极射频消融改良迷宫术治疗风湿性心瓣膜病合并永久性房颤远期疗效好,年龄及术前左心房内径是影响手术远期疗效的因素。     

心脏瓣膜置换术同期冲洗式射频消融术效果观察

目的观察瓣膜置换手术同期冲洗式射频消融术对慢性房颤的临床治疗效果。方法对31例心脏瓣膜病患者行瓣膜置换手术同期冲洗式射频消融术，观察手术前后左房变化、术后心电图变化、术后引流量、术后血制品用量等。结果本组患者平均转机时间（105．86±20．88）min，平均阻断时间（60．71±16．57）min，与我院同期心脏瓣膜置换手术比较差异无统计学意义（P〉0．05）；术后13例（41．9％）需临时起搏器维持心率，均于术后12h～12d恢复自主心律（房颤或窦性心律）；术后随访6～21个月，平均（15．6±3．7）个月，术后1个月，14例（14／31）恢复窦性心律，术后1年，20例（20／27）恢复窦性心律。术后1个月随访恢复窦性心律的14例（转复组）与未复律的17例（房颤组）比较，两组术前左房内径、术后左房内径／术前左房内径差异有统计学意义（P〈0．05）。结论心脏瓣膜置换术同期冲洗式射频消融术是治疗心脏瓣膜病患者慢性房颤的有效、安全手段。     

心房颤动患者左心房纤维化对射频消融术后心律的影响

目的 探讨心房颤动患者左心房纤维化特点及其对外科射频消融术后窦性心律恢复的影响.方法 选取2011年7月至9月北京安贞医院心外科九病房心脏直视手术同期行双极射频消融术患者60例,均为风湿性心脏瓣膜病持续性及永久性房颤,术中射频消融前取左心耳病理标本.根据术前左心房内径(LAD)不同,分为a组(LAD≤50 mm)、b组(50 mm＜ LAD≤60 mm)、c组(60 mm＜LAD≤70 mm)、d组(LAD ＞70 mm),每组各15例.标本切片染色后,比较4组心房肌纤维化程度及细胞径差异.收集患者术后即刻、出院时心电图,随访术后第3、6、12个月心电图,研究4组患者术后窦性心律恢复情况.结果 4组显微镜下测得胶原容积分数值和心肌细胞径差异均有统计学意义(P＜0.001);术后6、12个月窦性心律恢复率差异有统计学意义(P＜0.05).患者术后即刻、出院时、3、6、12个月窦性心律恢复率分别为,a组93.3％、93.3％、93.3％、100％、100％;b组80.0％、73.3％、80.0％、80.0％、80.0％;c组66.7％、66.7％、66.7％、73.3％、66.7％;d组53.3％、53.3％、53.3％、60.0％、60.0％.结论 风湿性心脏病房颤患者术前左心房内径越大、心房纤维化程度越高,心肌细胞径越大外科射频消融术后6及12个月窦性心律维持率越低.     

转化生长因子β1的表达与风湿性心脏病慢性心房颤动射频消融疗效的关系

目的 探讨转化生长因子β1(TGF-β1)的mRNA表达与风湿性心脏病慢性心房颤动(简称房颤)患者射频消融疗效的关系.方法 2008年1月至9月,40例瓣膜手术同期行射频消融术的风湿性心脏病慢性房颤患者,术中获取左心耳,根据术后6个月的随访结果分为房颤消除组及房颤未消除组;以同期行瓣膜手术的风湿性心脏病窦性心律患者10例为对照.通过苦味酸大狼猩红染色法分析心房组织中Ⅰ型及Ⅲ型胶原容量分数(CVF-Ⅰ和CVF-Ⅲ),RT-PCR法检测TGF-β1的mRNA表达.结果 至随访结束,40例房颤患者有28例房颤消除,12例未消除.与窦性心律组相比,房颤消除组和房颤末消除组患者心房组织TGF-β1的mRNA表达、CVF-Ⅰ及CVF-Ⅰ/CVF-Ⅲ比值依次增加(P＜0.05).房颤消除组中左心房功能未恢复的患者心房组织TGF-β1 mRNA表达高于左心房功能恢复患者(P＜0.05).心房组织TGF-β1 mRNA表达与CVF-Ⅰ及左心房直径均呈正相关(r=0.786和0.858,P＜0.05).Logistic回归分析发现,影响同期射频消融术疗效的危险因素有TGF-β1 mRNA表达水平(OR=1.13,95%CI 1.05～1.18,P=0.031)、CVF-Ⅰ(OR=1.07,95%CI 1.00～1.13,P=0.037)及左心房直径(OR=2.23,95%CI 1.08～4.59,P=0.042).结论心房组织TGF-β1的mRNA表达程度在房颤患者心房结构重构中起重要作用,并影响外科射频消融治疗后窦性心律的维持及心房的功能恢复.     

二尖瓣置换同期行射频消融术治疗房颤术后复发的危险因素分析

目的探讨二尖瓣置换同期行射频消融术治疗房颤术后复发的危险因素。方法回顾性分析本院及邵逸夫医院收治的瓣膜病合并房颤患者136例,均采用二尖瓣置换与同期射频消融术进行治疗,其中52例发生术后复发,采用单因素分析和多元回归分析筛选影响房颤复发的影响因素及危险因素。结果单因素分析结果显示房颤病程、高血压、P波离散度、术前及术后的LAD、LVEF及术后血清hs-CRP水平均可能影响患者的复发率(P<0.05);将单因素分析所得结果纳入非条件Logistic回归分析,结果显示房颤病程、高血压、P波离散度、手术前后LAD及术后血清hs-CRP水平为二尖瓣置换同期行射频消融术治疗房颤术后复发的影响因素(P<0.05),其中房颤病程>5年、合并有高血压、P波离散度>40ms、术后LAD>45mm、术后hs-CRP>0.6 mg/dl又为其危险因素(OR>1)。结论二尖瓣置换同期行射频消融术治疗房颤术后复发率高,病程、高血压、P波离散度、术后LAD及hs-CRP水平均为其危险因素,具有较高的监测价值。     

二尖瓣置换术后新发房颤的围手术期危险因素

目的 探讨窦性心律患者行二尖瓣置换术后新发房颤的发生率和围手术期危险因素.方法 回顾性分析1998年至2008年行二尖瓣置换术的术前窦性心律患者586例,根据术后是否发生房颤,分为术后房颤组(AF组)和术后窦性心律组(SR组).纳入评估的危险因素共29个,根据数据类型的不同选用t检验或x2检验进行单因素分析.单因素分析中P＜0.1的指标进入多因素logistic回归分析.多因素分析中P＜0.05为差异有统计学意义.结果 全组中118例发生术后房颤,发生率为20.1％.单因素分析中年龄、慢性肺部疾病、左室质量分数、左心房容积、右心房容积、三尖瓣反流、心功能衰竭、瓣膜病理类型、术后人工二尖瓣有效开口面积指数、术后机械通气时间、术后血清镁浓度及血清钾浓度等12个危险因素对术后房颤的影响较为显著;多因素分析中年龄、左心房容积、术后人工二尖瓣有效开口面积指数和术后血清钾离子浓度在两组间具有统计学差异.结论 年龄、左心房容积、术后人工二尖瓣有效开口面积指数和术后血清钾离子浓度是窦性心律患者二尖瓣置换术后发生房颤的独立危险因素.     

左心房后壁盒式消融的改良心脏迷宫手术疗效

目的 探讨盒式消融术式能否提高心房颤动(房颤)治疗的成功率.方法 2009年1至12月,心脏直视手术同期行改良迷宫手术患者中,行左心房后壁盒式消融术者60例,同期配对选择60例非盒式消融术者作为对照组.两组均经过相对一致的术前检查和围手术期处理.结果 除盒式消融组体外循环时间较长外,两组在年龄、房颤时间、左心房直径、左心室射血分数、同期手术等差异无统计学意义,两组围手术期均无死亡病例.所有病例均顺利随访,平均(9.0±8.4)个月.盒式消融组1例在术后2个月死于脑出血,非盒式消融组1例在术后12个月出现脑梗塞.术后1与3个月,两组免于房颤率分别为70.0％对51.2％(P=0.039)与78.3％对60.0％ (P =0.030);术后6个月分别为80.0％对71.7％ (P =0.286).8例因房颤心律复发再次入院,两组分别有4例和2例行导管消融,两组各有1例行电复律,均恢复窦性心律,并继续口服胺碘酮治疗3个月.结论 盒式消融组通过增加左、右肺静脉之间连线,比非盒式消融组左、右肺静脉之间单一连线,明显提高射频消融迷宫手术后早期(1～3个月)窦性心律的维持率;但在术后半年,两组窦性心律的维持率差异无统计学意义.     

直视下射频消融肺静脉口治疗风湿性心脏病心房颤动的临床观察

目的探讨心脏直视下射频消融肺静脉口治疗风湿性心脏病心房颤动(房颤)的临床疗效。方法对20例风湿性心瓣膜病伴房颤患者(治疗组),在瓣膜置换术中应用射频探针在左心房内行直视下围绕4个肺静脉口的环形线性消融及消融环最低点与二尖瓣环连线的直线消融,输出功率30～40 W,每次放电时间45～60 s。以20例单纯行瓣膜置换术的风湿性心瓣膜病伴房颤患者为对照组,两组均同时应用胺碘酮辅助治疗,比较两组治疗房颤的疗效。患者治疗后均获得随访,平均随访(24±3)个月。结果治疗组心脏复跳后19例转为窦性心律,住院期间房颤复发2例,随访中房颤复发1例,总有效率80%(16／20);对照组心脏复跳后16例为窦性心律,住院期间房颤复发7例,随访中房颤复发2例,总有效率35%(7/20)无心房穿孔、出血及房室传导阻滞等并发症。结论直视下射频消融肺静脉口治疗风湿性心脏病房颤有效率较高,方法简单,并发症少。     

双心房或单纯右心房射频消融术治疗成人先天性心脏病房间隔缺损合并心房颤动的对比研究

目的分析双心房射频消融术与单纯右心房射频消融术治疗成人先天性心脏病房间隔缺损合并心房颤动（房颤）的效果。方法回顾性分析2007年1月至2012年12月47例房间隔缺损合并心房颤动接受房间隔缺损修补联合射频消融术治疗患者的临床资料,其中男20例,女27例;年龄35～76岁;房颤病程3个月至15年;持续性房颤18例,长程持续性房颤29例。合并二尖瓣轻度至中度以上关闭不全10例,三尖瓣轻度至中度以上关闭不全28例。根据手术方式不同将47例患者分为两组,单纯右心房消融组（n=19）：行房间隔缺损修补术＋单纯右心房射频消融术;双心房消融组（n=28）：行房间隔缺损修补术＋双心房射频消融术。对于二尖瓣、三尖瓣存在轻一中度以上反流者,术中同期行二尖瓣、三尖瓣成形术。所有患者术后3个月、6个月、12个月均接受24h动态心电图检查,1年后间断门诊随访。结果双心房消融组的体外循环时间、主动脉阻断时间及术后住院时间较单纯右心房消融组略长,但两组术后早期并发症及恢复情况无明显差异。心脏复跳时,双心房消融组25例（89．3％）直接恢复窦性心律,3例为交界心律,无房颤心律。单纯右心房消融组14例（73．7％）直接恢复窦性心律,2例为交界心律,3例为房颤心律。出院时,双心房消融组28例（100％）均维持窦性心律;单纯右心房消融组15例（78．9％）维持窦性心律,4例房颤复发（P=0．045）。所有患者均得到随访,随访时间3～75个月,全组无死亡病例;房间隔无残余分流;2例出现二尖瓣轻一中度以上关闭不全,4例出现三尖瓣轻．中度以上关闭不全;双心房消融组术后2年累积窦性心律维持率为87．7％±6．7％,明显高于单纯右心房消融组的47．4％±11．5％（P=0．003）。结论对于成人房间隔缺损合并房颤,双心房射频消融术较单纯右心房射频消融术有更好的治疗效果,而且不会增加手术的风险。     

心内直视手术同期双极射频消融治疗心房颤动137例的临床效果

目的评估双极射频消融术在心内直视手术中治疗心房颤动(房颤)的临床效果。方法回顾性分析2009年5月至2014年6月137例合并房颤(21例合并左心房血栓)的心脏病患者行心脏直视手术同期进行双极射频消融术的临床资料,男61例、女76例,年龄35~73(48.3±11.6)岁。患者术后口服胺碘酮6个月,并定期随访,记录窦性心律转复率、术中术后并发症发生率,心功能改善情况、术后生存率、血栓栓塞发生率以及其他手术并发症等。结果 137例患者术中体外循环时间为(122±38)min,主动脉阻断时间为(78±22)min,射频时间为(20±4)min。手术当日130例房颤消除,其中转为窦性心律114例,交界性心律16例,房颤消除率为94.9%。围手术期死亡2例,住院死亡率为1.5%。术后1个月、6个月、1年、2年的窦性心律转复率分别为81.5%(110/135)、88.1%(111/126)、83.1%(74/89)、83.0%(39/47)。术后1年和2年生存率分别为96.6%(86/89)和93.6%(44/47)。随访期间无远期血栓栓塞发生。结论心内直视手术同期双极射频消融手术有选择地治疗合并有房颤的心脏疾病患者,仅轻微增加了转流及主动脉阻断时间。双极射频消融手术窦性心律转复率高,短中期效果好,远期效果仍需进一步观察。     

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 comparison of the inhibitory effects of four volatile anaesthetics on the metabolism of chlorzoxazone, a substrate for CYP2E1, in rabbits

Background: Halothane inhibits in vitro and in vivo activity of cytochrome P-450 (CYP) 2E1. There are several fluorinated volatile anaesthetics besides halothane, and most of them are defluorinated by CYP2E1. It is unclear whether other fluorinated anaesthetics inhibit the in vivo activity of CYP2E1.
Methods: We compared the inhibitory effects of therapeutic concentrations of four inhalational anaesthetics, halothane, enflurane, isoflurane, and sevoflurane, on chlorzoxazone metabolism in rabbits receiving artificial ventilation.
Results: All four inhalational anaesthetics decreased arterial blood pressure and increased plasma chlorzoxazone concentration. However, no significant differences in the plasma chlorzoxazone concentration were found between the four anaesthetics. The estimated chlorzoxazone clearance increased after beginning inhalation with all four agents, but no significant difference in clearance was noted between agents.
Conclusions: At therapeutic concentrations, the in vivo inhibitory effect on chlorzoxazone metabolism was similar for all four inhalational anaesthetics examined, even though their chemical characteristics and extent of hepatic metabolism differ considerably.     

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.