地氟醚、异氟醚对罗库溴铵强化作用的时间依赖性研究

目的：观察IMAC地氟醚或异氟醚对罗库溴铵强化作用的时间依赖性。方法：24例择期腹部手术病人在咪唑安定－芬太尼－异丙酚麻醉期间持续输注罗库溴铵，维持95％的肌松，达到稳态后，病人随机吸入呼气末浓度为1MAC的地氟醚或异氟醚，调整罗库溴铵的注入速率，维持95％的肌松，观察吸入地氟醚或异氟醚后罗库溴铵的注入速率随时间变化的趋势。结果：地氟醚，异氟醚都显著降低了罗库溴铵的注入速率，此效应随吸入地氟醚或异氟醚时间的延长逐渐加，吸入地氟醚或异氟醚90min后达最大效应即罗库溴铵的注入速率下降到最大值。最大下降率：地氟醚组为42．7％，异氟醚组为37．6％，结论：地氟醚，异氟醚明显增强罗库溴铵的肌松作用，其程度相近，且这种强化作用有显著的时间依赖性。     

七氟醚对不同性别患者罗库溴铵肌松作用的影响

目的 比较罗库溴铵肌松效应的性别差异和七氟醚对不同性别患者罗库溴铵肌松增效作用.方法 择期手术患者120例(男:女为1:1),年龄20～60岁.ASA Ⅰ或Ⅱ级,按性别随机分为丙泊酚组和七氟醚组:女性丙泊酚组(PF组).男性丙泊酚组(PM组),女性七氟醚组(SF组),男性七氟醚组(SM组),每组30例.所有患者静脉注射咪达唑仑、芬太尼和丙泊酚行麻醉诱导,意识消失后,置入喉罩,接麻醉机辅助通气并启动肌松监测.丙泊酚组静脉输注丙泊酚维持麻醉,设定血浆靶控浓度2～6 μg/ml,输注丙泊酚5 min后静脉注射罗库溴铵0.6 mg/kg,七氟醚组在呼气末七氟醚浓度稳定于1 MAC 5 min后静脉注射罗库溴铵0.6 mg/kg.记录肌松起效时间、完全肌松时间、T1恢复到25%和TOF恢复到25%的时间.结果 PM组较PF组起效时间长,完全肌松时间、T1恢复到25%和TOF恢复到25%的时间缩短(P＜0.05).SF组TOF恢复到25%的时间较PF组延长(P＜0.05),SM组较PM组起效时间缩短,完全肌松时间、T1恢复到25%和TOF恢复到25%的时间均延长(P＜0.05).SM组T1恢复到25%和TOF恢复到z5%的时间较SF组延长(P＜0.05).结论 女性罗库溴铵起效更快,作用时间长;而七氟醚对男性罗库溴铵的增效作用优于女性.     

全凭静脉麻醉中雷米芬太尼减少肌松药用量的机制探讨

目的：雷米芬太尼作为一种新型的麻醉性镇痛药在临床已经广泛应用于静脉全麻．目前发现在静脉全麻中雷米芬太尼可以明显减少肌肉松弛药的用量．这是否是雷米芬太尼与肌松药的协同作用还不清楚．本研究应用Organon-TOF—WATCH SX肌松监测仪观察垒凭静脉麻醉下腹腔镜手术中靶控输注不同剂量的雷米芬太尼对肌松药罗库溴铵的起效．作用和恢复时间的影响,以此来判断雷米芬太尼与肌松药之间是否有协同作用。方法：选择ASAI—II级．年龄25-55岁,妇科及普外科腹腔镜择期手术病人75例随机分为兰组,全麻诱导：咪唑安定0．04mg·kg^-1,丙泊酚TCI血药浓度3ug·ml^-1．罗库溴铵0．6mg·kg^-1．麻醉维持：A组单纯用TCl丙泊酚．B组用TCl丙泊酚加上TCI雷米芬太尼效应室浓度2ng．mr．．C组用TCI丙泊酚加上雷米芬太尼效应室浓度5ng．mI～,三组异丙酚TCI效应室浓度维持在3ug·ml^-1。左右,根据病人的反应调整．将麻醉深度控制在满足手术需要和术中BIS在40-60之间．用Organon—TOF—WATCH SX肌松监测仪记录罗库溴铵（0．6mg·kg^-1）的起效时间（从给药至TOF比值下降到25％的时间）、维持时间（从TOF值低于25％至恢复到25％）、恢复时间（从TOF比值恢复到25％至TOF比值恢复到75％）用美国Aspect公司的BIS-XP监测仪控制麻醉深度。结果：罗库溴铵的起效时间三组分别为0．96±0．35min．1．12±0．51min。1．11±0．34min,三组之间无统计学差异（P〉0．05）;罗库溴铵的作用时间三组分别为39．94±10．17min．42．45±11．07min。42．46±11．25min,备组间没有统计学差异（P〉0．05）．罗库溴铵的·I灰复时间三组分别为11．68±4．99min．13．44±5．93min．12．20±2．61min．各组间没有统计学差异（P〉0．05）。结论：不同TCI效应室浓度的雷米芬太尼没有明显延长单次注射罗库溴铵（0．6mg·kg^-1）的起效．作用和恢复时间．提示雷米芬太尼减少静脉全麻中肌松药用量的作用机制是中枢性的。     

异氟醚对罗库溴铵肌松效应影响的实验研究

目的　通过在体兔坐骨神经一胫前肌标本的制备,研究异氟醚对单次静注和连续输注罗库溴铵肌松效应的影响。方法　实验家兔均采用异氟醚全麻。10只家兔分为两组观测,观察组间单次静注罗库溴铵的肌松时效的变化;另取10只家兔分为两组,观察组间罗库溴铵连续输注后的肌松时效和输注量的变化。结果　单次静注罗库溴铵(2 倍 ED95 )时,异氟醚使其作用时间延长约 7min(P<0 .05),同时罗库溴铵对血液动力学影响轻微;连续静注罗库溴铵时,异氟醚使罗库溴铵的静脉输注需要量减少40%(P<0 .05),而对起效和恢复指数无明显影响。结论　异氟醚能增强罗库溴铵的肌松时效。     

儿童七氟醚、异氟醚及全静脉麻醉中罗库溴铵的恢复时程

目的 比较罗库溴铵气管插管剂量在儿童七氟醚、异氟醚和全静脉麻醉中恢复时程的差异.方法 51例2～14岁儿童随机均分为七氟醚组(S组)、异氟醚组(I组)和全静脉麻醉组(P组).静脉给予罗库溴铵O.6 mg/kg,比较T1恢复至基础值10%、25%、75%的时间(T10、T25、T75)和恢复指数(RI=T75-T25)在不同麻醉方式下的差异.结果 三组儿童T10、T25差异无统计学意义.I组T75和RI长于P组(P＜0.05),S组与P组比较有延长趋势,但差异无统计学意义.S组与I组所有时点差异均无统计学意义.结论 儿童罗库溴铵气管插管剂量,在七氟醚、异氟醚和全静脉麻醉下的临床作用时间差异无统计学意义,异氟醚麻醉下肌松作用完全恢复时间较在全静脉麻醉下显著延长.     

异氟醚吸入麻醉与异丙酚静脉麻醉下长时间持续输注罗库溴铵的肌松作用

目的比较异氟醚吸入麻醉与异丙酚静脉麻醉下长时间持续输注罗库溴铵的肌松作用。方法拟在全麻下行口腔-颌面肿瘤择期手术(手术时间达5 h左右)病人30例,ASAⅠ或Ⅱ级,年龄18～65岁,随机分为2组(n=15):异丙酚组(Ⅰ组)异氟醚组(Ⅱ组)。用TOF-Watch SX肌松监测仪进行拇内收肌肌松监测。静脉注射罗库溴铵初始剂量0．6 mg·kg-1后气管插管,持续输注罗库溴铵。调整罗库溴铵的输注速率,T1稳定在基础值的10％时(初始状态),Ⅰ组靶控输注异丙酚维持麻醉,Ⅱ组吸入1 MAC异氟醚维持麻醉,持续5 h,术中维持T1在基础值的10％。记录罗库溴铵输注速率、恢复指数(T1恢复25％至75％的时间,T25-75)以及罗库溴铵停止输注到TOFR为0．9的时间。结果与初始状态比较,Ⅰ、Ⅱ组持续给药30 min-5 h时罗库溴铵输注速率下降(P<0．05);Ⅱ组持续给药1～5 h时罗库溴铵输注速率低于Ⅰ组(P<0．05)。两组间恢复指数和罗库溴铵停止输注到TOFR为0．9的时间差异无统计学意义(P>0．05)。结论罗库溴铵可用于长时间持续输注以维持稳定的肌松。维持T1在基础值的10％的情况下,持续输注罗库溴铵5 h时异氟醚麻醉比异丙酚为主的全凭静脉麻醉罗库溴铵输注速率减少30％,但其恢复指数无差异。     

七氟烷对顺式阿曲库铵和罗库溴铵肌松作用的影响

目的：比较七氟烷对顺式阿曲库铵和罗库溴铵肌松效应的影响。方法：择期手术患者240例,随机分为顺式阿曲库铵组（CIS120例）和罗库溴铵组（ROC120例）。两组患者再随机分为丙泊酚组（60例）和七氟烷组（60例）,均静脉注射咪达唑仑、芬太尼和丙泊酚行麻醉诱导,丙泊酚组靶控输注丙泊酚维持麻醉,设定血浆靶控浓度2～6μg/mL,输注丙泊酚5min后静脉注射顺式阿曲库铵0.15mg/kg或罗库溴铵0.6mg/kg;七氟烷组在呼气末七氟烷浓度稳定于1MAC5min后静脉注射顺式阿曲库铵0.15mg/kg或罗库溴铵0.6mg/kg。结果：CIS两组,起效时间差异无统计学意义（P〉0.05）;七氟烷组完全肌松时间、维持时间与丙泊酚组比较均显著延长（P〈0.01）。ROC两组,起效时间差异无统计学意义（P〉0.05）;七氟烷组完全肌松时间、维持时间与丙泊酚组比较均显著延长（P〈0.01）。结论：七氟烷对顺式阿曲库铵及罗库溴铵的肌松均有增效作用。     

性别因素对七氟醚增强顺阿曲库铵或罗库溴铵肌松效应的影响

目的 探讨性别因素对七氟醚增强顺阿曲库铵或罗库溴铵肌松效应的影响.方法 择期全麻手术患者240例,年龄20～60岁,ASA分级Ⅰ或Ⅱ级,BMI 20～30 kg/m2,随机分为2组(n=120):顺阿曲库铵组和罗库溴铵组,各组按性别和麻醉药再分4个亚组(n=30):女性异丙酚组、男性异丙酚组、女性七氟醚组和男性七氟醚组.各异丙酚组靶控输注异丙酚,血浆靶浓度2～6 μg/ml,各七氟醚组吸入七氟醚,于靶控输注或待呼气末七氟醚浓度稳定于1.71%5 min后,静脉注射顺阿曲库铵0.15 mg/kg或罗库溴铵0.6 mg/kg.记录肌松起效时间、肌松作用峰值时间、T1 25%恢复时间和TOFR25%恢复时间.结果 与异丙酚麻醉比较,女性患者七氟醚麻醉时,罗库溴铵TOFR 25%恢复时间延长,顺阿曲库铵肌松作用峰值时间、T1 25%恢复时间和TOFR 25%恢复时间延长,男性患者七氟醚麻醉时,罗库溴铵起效时间缩短,肌松作用峰值时间、T1 25%恢复时间和TOFR 25%恢复时间延长,顺阿曲库铵肌松作用峰值时间、T1 25%恢复时间和TOFR 25%恢复时间延长(P＜0.05或0.01);七氟醚麻醉时与男性患者比较,女性患者罗库溴铵T1 25%恢复时间和TOFR 25%恢复时间缩短,顺阿曲库铵起效时间缩短(P＜0.05或0.01).结论 七氟醚对罗库溴铵肌松的增强作用存在性别差异,男性强于女性;对顺阿曲库铵肌松的增强作用无明显性别差异.     

罗库溴铵的自动化反馈控制给药

目的：本实验设计了一种比例－积分（ＰＩ）控制器，自动化反馈控制罗库溴铵的持续静脉输注，并研究了吸入麻醉药七氟醚对罗库溴铵的肌松作用的影响。方法：选择１４例ＡＳＡ分级Ⅰ～Ⅱ级的手术病人，随机分成七氟醚麻醉组（７例）和芬太尼复合麻醉组（７例）两组。０．６ｍｇ／ｋｇ（２×ＥＤ９５）罗库溴铵静注气管插管后，ＰＩ控制器开始控制罗库溴铵的持续静脉输注，将肌松维持在设定点ＴＨ＝５％的水平。结果：维持９５％的神经肌肉阻滞，芬太尼复合麻醉组罗库溴铵的持续输注速率为８．６±１．１μｇ·ｋｇ－１·ｍｉｎ－１；七氟醚组为４．７±１．２μｇ·ｋｇ－１·ｍｉｎ－１。七氟醚显著地降低了罗库溴铵的输注需要量（Ｐ＜０．０１）。控制器性能指标平均超调七氟醚组为０．６０％±０．４６％，复合麻醉组为０．４２％±０．６７％；平均标准差分别为１．８０％±０．６８％和２．１６％±０．７５％。结论：控制器能够将肌松控制在稳态水平，且能满足手术所要求的较高肌松水平。七氟醚显著地强化了罗库溴铵的肌松作用。     

地氟醚和异氟醚对罗库溴铵肌松效应的影响

罗库溴铵是一种起效时间短的新型甾类非去极化肌松药。本研究以异丙酚为对照观测地氟醚、异氟醚对罗库溴铵肌松效应的影响。资料与方法5 4例ＡＳＡⅠ～Ⅱ级 ,年龄 2 0～ 6 5岁拟行全麻的病人 ,随机分为两组 :甲组 2 4例用于观测地氟醚和异氟醚对罗库溴铵量 效关系的影响 ,再随机分为三个亚组 :异丙酚组、异氟醚组和地氟醚组 ,每个亚组 8例 ,分别用异丙酚、异氟醚和地氟醚维持麻醉 ;乙组 30例用于观测地氟醚和异氟醚对罗库溴铵时 效关系的影响 ,也随机分为上述三个亚组 ,每个亚组 10例。所有病人均不用术前用药。以芬太尼 2 μｇ·ｋｇ-1、…     

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.