肾脏远隔缺血后适应在兔急性肠系膜缺血再灌注损伤中的作用

目的 观察以肾脏作为远隔器官的远隔缺血后适应能否减轻兔急性肠系膜缺血再灌注损伤.方法 将雄性新西兰兔90只随机分为对照组、缺血再灌注(I/R)组、远隔缺血后适应(IRpostC)组,每组30只.分别干预后采集各组兔部分肠道组织作为标本,试剂盒检测肠道组织内丙二醛(MDA)、髓过氧化物酶(MPO)水平,苏木素-伊红(HE)染色,chiu6级评分法观察肠黏膜损伤,电镜下观察肠上皮细胞变化.结果 I/R组肠道组织中MDA、MPO测定值及肠黏膜损伤评分分别为( 14.72±0.21) nmol/mg、( 1.65±0.35) U/g、(3.30±0.69),IRpostC组分别为(7.13 ±0.40) nmol/mg、(0.91±0.33) U/g、2.10 ±0.92,与对照组[(3.28±0.26) nmol/mg、(0.52 ±0.23) U/g、0.69±0.52]比较差异均有统计学意义(P＜0.01).与I/R组比较,IRpostC组肠道组织中MDA、MPO水平及肠黏膜损伤评分明显降低(P＜0.01),电镜下发现细胞损伤减轻.结论 以肾脏作为远隔器官的远隔缺血后适应可明显降低兔急性肠系膜缺血再灌注损伤后肠道组织中MDA、MPO水平及肠黏膜损伤.     

缺血预处理-后处理对大鼠肠缺血再灌注损伤的影响

目的 评价缺血预处理.后处理对大鼠肠缺血再灌注损伤的影响.方法 清洁级成年雄性SD大鼠40只.体重225～275 g,随机分为5组(n=8):假手术组(S组)仅分离肠系膜上动脉(SMA),不夹闭;肠缺血再灌注组(IIR组)采用夹闭SMA 60 min,再灌注60 min的方法制备肠缺血再灌注损伤模型;缺血预处理组(IPr组)夹闭SMA 10 min,再灌注10 min,余同IIR组;缺血后处理组(IPo 组)夹闭SMA 60 min后,再灌注30 s,缺血30 s,反复3次,再灌注60 min;缺血预处理.后处理组(IPr-IPo组)先行缺血预处理,再行缺血后处理,操作过程同IPr组和IPo组.于再灌注60 min时各组取肠粘膜组织,观察肠粘膜形态并行Chiu评分,检测丙二醛(MDA)含量,超氧化物歧化酶(SOD)及髓过氧化物酶(MPO)活性,同时采集动脉血样检测血浆肿瘤坏死因子α(TNF-α)及白细胞介素6(IL-6)浓度.结果 与S组比较,其余各组Chiu评分、MDA含量、MPO活性、血浆TNF-α与IL-6浓度升高,SOD活性降低(P<0.05).与IIR组比较,IPr组、IPo组及IPr-IPo组Chiu评分、MDA含量、MPO活性、血浆TNF-α和IL-6浓度降低.SOD活性升高(P<0.01).与IPr组和IPo组比较,IPr-IPo组Chiu评分和MDA含量降低,SOD活性升高(P<0.05).IPr组与IPo组各指标比较差异无统计学意义(P>0.05).结论 缺血预处理-后处理可减轻大鼠肠缺血再灌注损伤,较单独应用时效果好.     

缺血后处理对小肠缺血再灌注损伤的保护作用

目的：观察缺血后处理减轻肠缺血再灌注引起的小肠及远隔脏器损伤的效果,并探讨其机制。方法将家兔48只随机分为假手术组、缺血再灌注组、缺血后处理组,每组16只。再灌注2 h 后采集各组动脉血、静脉血及部分肠道组织、肝、肺组织,测动脉血中 TNF-α、IL-1β、IL-6、IL-10水平,测静脉血中 ALT、AST、BUN,Cr、LDH、CK-MB 活性,测内毒素水平,测定血清及小肠、肝、肺组织 MDA、MPO、CAT、SOD 水平,HE 染色,观察肠黏膜损伤情况,细菌培养观察细菌易位率。结果与缺血再灌注组比较,缺血后处理组血清及小肠、肝、肺组织中 MDA、MPO 水平明显降低, SOD、CAT 水平明显升高,静脉血 ALT、AST、LDH、CK-MB、BUN 下降;动脉血中 TNF-α、IL-1β、IL-6、内毒素降低,IL-10水平升高,肠黏膜损伤评分明显降低。结论缺血后处理可以减轻肠黏膜损伤,减少内毒素易位,促进抗炎因子的激活,抑制炎性介质的过度释放,提升小肠组织及远隔脏器的氧自由基的抗氧化能力,减轻小肠及远隔脏器组织损伤。     

肠系膜上动脉灌注高氧液对家兔肠缺血-再灌注损伤的保护作用

目的探讨术中肠系膜上动脉(SMA)灌注高氧液对家兔肠缺血再灌注损伤的保护作用及机制。方法健康家兔32只,随机均分为假手术组(S组)、缺血再灌注组(I组)、高氧液灌注组(H组)和灌注对照组(C组)。开腹夹闭SMA1h造成缺血,松夹再灌注2h制作肠缺血再灌注模型。H组在缺血期经SMA以20ml·kg-1·h-1恒速灌注高氧液1h,C组则采用同样方法输入等容量的5%葡萄糖液。再灌注2h后分别测定各组肠组织丙二醛(MDA)含量及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GPX)活性;观察光镜下各组肠粘膜组织形态学改变;测定肠粘膜组织ATP含量,并测定肠道的氧摄取率。结果小肠缺血再灌注后,肠组织MDA含量明显升高,SOD、CAT和GPX活性明显下降,光镜下肠粘膜损伤严重,肠粘膜组织ATP含量及肠道的氧摄取率均明显下降。I组与C组各参数差异无显著意义。与I组和C组相比,H组肠组织MDA含量明显降低(P<0.01),SOD、CAT和GPX活性明显升高(P<0.05),光镜下肠粘膜损伤明显减轻,肠粘膜组织ATP含量及肠道的氧摄取率均明显增加(P<0.05,P<0.01)。结论术中经SMA灌注高氧液是一种安全有效的小肠保护方法,这与高氧液中的高氧分压有关,并通过增强抗氧化酶的活性减轻肠缺血再灌注损伤。     

肢体缺血预处理对兔肺缺血再灌注损伤的影响

目的 探讨肢体缺血预处理对兔肺缺血再灌注损伤的影响.方法 健康日本大耳白兔18只,体重2.0～2.5 kg,雌雄不拘,随机分为3组(n=6):假手术组(S组)开胸后左侧肺门穿线但不结扎,旷置观察340 min;缺血再灌注组(IR组)开胸旷置100 min,阻断左侧肺门,左肺不张后60 min再灌注180 min;肢体缺血预处理组(L组)捆绑双后肢10 min,松开10 min,反复3次后恢复灌注,60 min后阻断左侧肺门60 min,再灌注180 min.于缺血前、再灌注15、30、60、120、180 min时采集左颈内动脉血样行血气分析,计算呼吸指数(R1);于再灌注180 min时处死动物,取左肺上叶组织,测定超氧化物歧化酶(SOD)、髓过氧化物酶(MPO)活性及丙二醛(MDA)含量,计算肺湿干重比(W/D);取左肺下叶行支气管肺泡灌洗,计算肺通透性指数;取左肺中叶组织,观察肺组织病理学,进行弥漫性肺泡损伤(DAD)评分.结果 与s组比较,IR组RI、MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分升高,SOD活性降低(P<0.05或0.01);与IR组比较,L组RI,MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分降低,SOD活性升高(P<0.05或0.01);L组和S组间上述指标比较差异无统计学意义(P>0.05).L组和S组肺组织病理损伤程度较IR组减轻.结论 肢体缺血预处理可减轻兔肺缺血再灌注损伤.     

肢体缺血预处理对兔肺缺血再灌注损伤的影响

目的 探讨肢体缺血预处理对兔肺缺血再灌注损伤的影响.方法 健康日本大耳白兔18只,体重2.0～2.5 kg,雌雄不拘,随机分为3组(n=6):假手术组(S组)开胸后左侧肺门穿线但不结扎,旷置观察340 min;缺血再灌注组(IR组)开胸旷置100 min,阻断左侧肺门,左肺不张后60 min再灌注180 min;肢体缺血预处理组(L组)捆绑双后肢10 min,松开10 min,反复3次后恢复灌注,60 min后阻断左侧肺门60 min,再灌注180 min.于缺血前、再灌注15、30、60、120、180 min时采集左颈内动脉血样行血气分析,计算呼吸指数(R1);于再灌注180 min时处死动物,取左肺上叶组织,测定超氧化物歧化酶(SOD)、髓过氧化物酶(MPO)活性及丙二醛(MDA)含量,计算肺湿干重比(W/D);取左肺下叶行支气管肺泡灌洗,计算肺通透性指数;取左肺中叶组织,观察肺组织病理学,进行弥漫性肺泡损伤(DAD)评分.结果 与s组比较,IR组RI、MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分升高,SOD活性降低(P<0.05或0.01);与IR组比较,L组RI,MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分降低,SOD活性升高(P<0.05或0.01);L组和S组间上述指标比较差异无统计学意义(P>0.05).L组和S组肺组织病理损伤程度较IR组减轻.结论 肢体缺血预处理可减轻兔肺缺血再灌注损伤.     

肢体缺血预处理对兔肺缺血再灌注损伤的影响

目的 探讨肢体缺血预处理对兔肺缺血再灌注损伤的影响.方法 健康日本大耳白兔18只,体重2.0～2.5 kg,雌雄不拘,随机分为3组(n=6):假手术组(S组)开胸后左侧肺门穿线但不结扎,旷置观察340 min;缺血再灌注组(IR组)开胸旷置100 min,阻断左侧肺门,左肺不张后60 min再灌注180 min;肢体缺血预处理组(L组)捆绑双后肢10 min,松开10 min,反复3次后恢复灌注,60 min后阻断左侧肺门60 min,再灌注180 min.于缺血前、再灌注15、30、60、120、180 min时采集左颈内动脉血样行血气分析,计算呼吸指数(R1);于再灌注180 min时处死动物,取左肺上叶组织,测定超氧化物歧化酶(SOD)、髓过氧化物酶(MPO)活性及丙二醛(MDA)含量,计算肺湿干重比(W/D);取左肺下叶行支气管肺泡灌洗,计算肺通透性指数;取左肺中叶组织,观察肺组织病理学,进行弥漫性肺泡损伤(DAD)评分.结果 与s组比较,IR组RI、MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分升高,SOD活性降低(P<0.05或0.01);与IR组比较,L组RI,MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分降低,SOD活性升高(P<0.05或0.01);L组和S组间上述指标比较差异无统计学意义(P>0.05).L组和S组肺组织病理损伤程度较IR组减轻.结论 肢体缺血预处理可减轻兔肺缺血再灌注损伤.     

肢体缺血预处理对兔肺缺血再灌注损伤的影响

目的 探讨肢体缺血预处理对兔肺缺血再灌注损伤的影响.方法 健康日本大耳白兔18只,体重2.0～2.5 kg,雌雄不拘,随机分为3组(n=6):假手术组(S组)开胸后左侧肺门穿线但不结扎,旷置观察340 min;缺血再灌注组(IR组)开胸旷置100 min,阻断左侧肺门,左肺不张后60 min再灌注180 min;肢体缺血预处理组(L组)捆绑双后肢10 min,松开10 min,反复3次后恢复灌注,60 min后阻断左侧肺门60 min,再灌注180 min.于缺血前、再灌注15、30、60、120、180 min时采集左颈内动脉血样行血气分析,计算呼吸指数(R1);于再灌注180 min时处死动物,取左肺上叶组织,测定超氧化物歧化酶(SOD)、髓过氧化物酶(MPO)活性及丙二醛(MDA)含量,计算肺湿干重比(W/D);取左肺下叶行支气管肺泡灌洗,计算肺通透性指数;取左肺中叶组织,观察肺组织病理学,进行弥漫性肺泡损伤(DAD)评分.结果 与s组比较,IR组RI、MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分升高,SOD活性降低(P<0.05或0.01);与IR组比较,L组RI,MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分降低,SOD活性升高(P<0.05或0.01);L组和S组间上述指标比较差异无统计学意义(P>0.05).L组和S组肺组织病理损伤程度较IR组减轻.结论 肢体缺血预处理可减轻兔肺缺血再灌注损伤.     

缺血后处理对大鼠骨骼肌缺血再灌注损伤的影响

目的 探讨缺血后处理对大鼠骨骼肌缺血再灌注损伤的影响以及应用缺血后处理的时机.方法 将32只大鼠随机分成四组,采用切断患肢全部皮肤、肌肉和神经,保留患肢股动静脉的动物模型,通过夹闭和开放股动静脉造成骨骼肌缺血和再灌注损伤.采用测定骨骼肌缺血4 h.再灌注1 h后血清丙二醛(MDA)、骨骼肌髓过氧化物酶(MPO),再灌注6 h后骨骼肌的死亡程度来观察缺血后处理对大鼠骨骼肌缺血再灌注损伤的影响,以及再灌注5 min后应用缺血后处理是否对骨骼肌缺血再灌注损伤有保护作用.结果 对骨骼肌缺血4 h再灌注6 h的损伤,再灌注开始后即刻应用30 s缺血、30 s再通,三次循环的缺血后处理对骨骼肌的缺血再灌注损伤即有保护作用,不仅减少了骨骼肌再灌注区域中性粒细胞浸润(MPO)和血清氧自由基水平(MDA)水平,而且减少了骨骼肌的死亡程度;再灌注5 min后应用缺血后处理并没有降低骨骼肌缺血再灌注区域的MPO和血清MDA水平,也没有降低骨骼肌缺血再灌注后的死亡程度,与直接缺血再灌注组相同,对骨骼肌缺血再灌注损伤并没有保护作用.结论 骨骼肌缺血后再灌注开始前立刻应用缺血后处理对大鼠骨骼肌缺血再灌注损伤有一定的保护效果,可以减少骨骼肌缺血再灌注损伤后的死亡程度;缺血后处理应用时机非常重要,再灌注5 min后应用缺血后处理则失去对骨骼肌缺血再灌注损伤的保护作用.     

肢体缺血预处理对兔肺缺血再灌注损伤的影响

目的 探讨肢体缺血预处理对兔肺缺血再灌注损伤的影响.方法 健康日本大耳白兔18只,体重2.0～2.5 kg,雌雄不拘,随机分为3组(n=6):假手术组(S组)开胸后左侧肺门穿线但不结扎,旷置观察340 min;缺血再灌注组(IR组)开胸旷置100 min,阻断左侧肺门,左肺不张后60 min再灌注180 min;肢体缺血预处理组(L组)捆绑双后肢10 min,松开10 min,反复3次后恢复灌注,60 min后阻断左侧肺门60 min,再灌注180 min.于缺血前、再灌注15、30、60、120、180 min时采集左颈内动脉血样行血气分析,计算呼吸指数(R1);于再灌注180 min时处死动物,取左肺上叶组织,测定超氧化物歧化酶(SOD)、髓过氧化物酶(MPO)活性及丙二醛(MDA)含量,计算肺湿干重比(W/D);取左肺下叶行支气管肺泡灌洗,计算肺通透性指数;取左肺中叶组织,观察肺组织病理学,进行弥漫性肺泡损伤(DAD)评分.结果 与s组比较,IR组RI、MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分升高,SOD活性降低(P<0.05或0.01);与IR组比较,L组RI,MDA含量、MPO活性、肺W/D、肺通透性指数和DAD评分降低,SOD活性升高(P<0.05或0.01);L组和S组间上述指标比较差异无统计学意义(P>0.05).L组和S组肺组织病理损伤程度较IR组减轻.结论 肢体缺血预处理可减轻兔肺缺血再灌注损伤.     

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.