新型翻修延长棒的设计及其在翻修模型中的生物力学研究

目的 :采用对端结合的方式,设计适用于脊柱翻修手术的延长棒,研究其生物力学特性。方法 :依据美国材料与试验协会(American Society for Testing and Materials,ASTM)的标准测试方法,制备椎体切除术后腰椎模型。采用静态压缩弯曲试验、静态拉伸弯曲试验和疲劳试验,分别测量"传统连接棒"(A组,n=6)和"翻修延长棒"(B组,n=6)的屈服载荷、弯曲刚度和疲劳参考值,初步评价"翻修延长棒"的生物力学稳定型。结果:在静态压缩弯曲试验中,A组试验模型屈服载荷为865.60±25.71N,弯曲刚度为52.35±0.38N/mm。B组试验模型屈服载荷为863.20±11.01N,弯曲刚度为52.92±2.43N/mm,两组之间无统计学差异(P0.05)。在静态拉伸弯曲试验中,A组试验模型屈服载荷为1184.20±30.14N,拉伸弯曲刚度为58.89±3.01N/mm;B组试验模型屈服载荷为1169.20±14.89N,拉伸弯曲刚度为57.48±1.47N/mm,与A组比较均无统计学差异(P0.05)。在疲劳试验中,A组的疲劳载荷参考值为303N,B组的疲劳载荷参考值为302N,与A组比较无统计学差异(P0.05)。结论:新型翻修延长棒具有与传统连接棒相似的屈服载荷、弯曲刚度及耐疲劳性。     

人体胸腰椎体冲击损伤的生物力学研究

目的:探讨人体脊柱胸腰椎在冲击载荷作用下引起的爆裂骨折的生物力学机制及损伤特点。方法:自2008年9月至2009年10月,采集10具新鲜人体脊柱胸腰椎标本,平均分为两组,建立实验模型,分别进行静力学强度试验和动态冲击生物力学实验,观察在不同载荷作用下,胸腰椎体发生静态和动态冲击响应的相关数据。结果:胸腰椎屈服载荷为(5280.00±354.20)N,屈服位移为(13.32±2.07)mm,极限载荷为(6590.00±249.20)N,极限位移为(20.60±2.57)mm,加载速度为0.02g,胸腰椎的动态力学性质其平均极限载荷为(14425.60±1101.52)N,载荷平均作用时间为(17.29±2.04)ms,平均加速度为(36.80±2.81)g,动态位移为(45.11±1.13)mm。结论:胸腰椎爆裂性骨折是由高能量瞬间释放所导致的严重损伤,生物力学受力作用呈脉冲式变化,胸腰椎体具有生物材料的粘弹性性质。     

股骨远端LISS倒置固定股骨转子下骨折的生物力学研究

[目的]检测股骨远端LISS倒置固定股骨转子下骨折的生物力学性能。[方法]选取成年股骨16根,在小转子下方1 cm处截骨成2 cm间隙,模拟粉碎性高位股骨转子下骨折。标本随机分成2组,第1组用倒置LISS固定,第2组用PFNA固定。先将标本置于液压伺服力学测试机,行非破坏性应力加载试验,观察载荷-应变关系、股骨头的载荷-位移关系、骨折固定后的强度和轴向刚度。再行非破坏性循环加载试验,循环周期2 000次。最后进行极限力学性能试验。对试验数据用Chauvent准则行精度分析,用t检验。[结果]轴向压缩试验中,LISS组在应变片1和应变片2处的应变均于PFNA组相应的应变值近似;载荷600 N时,LISS组与PFNA组股骨头纵向位移分别为(2.87±0.84)mm、(2.89±0.74)mm;载荷600 N时,两组的骨折固定后强度值近似;载荷600 N时,LISS组与PFNA组的轴向刚度分别为(209.06±18.63)N/mm、(207.61±18.73)N/mm。动态疲劳实验中,相同循环加载周期下,LISS组股骨头的最大下沉位移近似于PFNA组;LISS组与PFNA组在股骨头下沉位移0.5 mm时承受的力分别为(130.83±11.67)N、(128.76±8.35)N;股骨头下沉位移0.5 mm时,LISS组与PFNA组分别是循环加载周期的(1 231±30)次、(1 221±27)次。LISS组、PFNA组极限载荷分别为(3 728±128)N、(3 786±115)N。经统计学分析,以上差异均无统计学意义(P>0.05)。[结论]本试验结果证实了股骨远端LISS倒置固定股骨转子下骨折具有良好的力学稳定性,是一种固定股骨转子下骨折的有效方法。     

两种前交叉韧带胫骨止点撕脱骨折固定的生物力学比较

[目的]探讨前交叉韧带(ACL)胫骨止点撕脱骨折两种内固定的生物力学特性,为临床提供良好的理论依据。[方法] 12具猪膝关节新鲜标本,制备ACL胫骨撕脱骨折模型,按照随机数字表法分2组,每组各6具膝关节。缝线组采用缝线结合外排锚钉固定,双排组采用锚钉双排桥式固定。生物力学测试机上进行测试,记录最终失效荷载、屈服载荷、位移、刚度。[结果]除缝线组1例失效,其余对象都通过了50～250 N载荷,1 000周期循环测试,位移缝线组为(4.19±1.31) mm,双排组为(1.94±0.31) mm,差异有统计学意义(P<0.05)。之后,轴向加载损毁试验,最终失效荷载缝线组为(612.60±121.59) N,双排组为(580.19±119.79) N,差异无统计学意义(P>0.05)。屈服载荷缝线组为(343.09±208.07) N,双排组为(278.01±196.39) N,差异无统计学意义(P>0.05)。刚度:缝线组(17.93±7.72) N/mm,双排组(48.34±9.57) N/mm,差异有统计学意义(P<0.05)。[结论]两种内固定方式都具有良好生物力学特性,均提供可靠内固定,在生物力学上无明显差异。在循环加载环境下,双排固定提供了更少的位移。相比抗拔能力,双排固定更强。     

NICE结固定锁骨中段骨折的生物力学研究

[目的]探讨NICE结固定锁骨中段骨折的生物力学特性。[方法]将60例人体锁骨标本随机分为4组，使用骨科摆锯制作锁骨中段骨折（OTA/AO分型15-A2）模型，分别行拉力螺钉固定，以及2-0线NICE结固定、1-0线NICE结固定和1#线NICE结固定。采用Instron生物力学测试机进行三点弯曲实验，测量各组不同固定方式骨折模型的失效载荷、最大位移及屈服刚度。[结果] 1#线NICE组与拉力螺钉组在失效载荷[(98.4±0.7)N vs (99.0±1.7)N, P>0.05]、最大位移[(10.1±0.4)mm vs (10.0±0.4)mm, P>0.05],以及屈服刚度[(24.4±0.4)N/mm vs (24.5±0.5)N/mm, P>0.05]差异无统计学意义。拉力螺钉组在失效载荷[(99.0±1.7)N,(45.2±0.5)N,(64.8±0.7)N, P<0.05]、最大位移[(10.0±0.4)mm,(9.4±0.6)mm,(5.6±0.5)mm, P<0.05]及屈服刚度[(24.5±0.5)N/mm,(5.0±0.3)N/mm,(...     

新型钳夹式外固定器的力学性能研究

目的钳夹式外固定器是通过夹持皮质骨但不穿透骨髓腔的一种外固定器械,探讨其能否在临床应用中保持足够的固定强度和稳定性。方法对钳夹罗盘锁紧后的抗拉伸能力进行试验,观察静力松弛、动态疲劳和抗拉伸刚度。钳夹固定于健康人胫骨标本的两端及骨干部位,进行拔出实验,计算最大拔出力。结果①200N拉伸力下,在实验的6h内基本保持稳定。②动态实验中到36000次循环时,钳夹臂位移平均增加0.32%,之后的循环加载中钳夹臂位移基本保持不变。③钳夹臂抗拉伸初始刚度平均为(1.36±0.14)N/m,到460N左右时平均刚度减低为(0.23±0.049)N/m。④拔出实验中,固定胫骨两端大号钳夹的平均拔出力为(670±50)N;固定胫骨骨干部位的小号钳夹的拔出力为(460±32)N。结论钳夹式外固定器在生理载荷下的强度可以达到使用要求。     

"轴心加压+侧方支撑"空心螺钉固定Pauwels Ⅱ型股骨颈骨折的力学分析

目的探讨"轴心加压+侧方支撑"理念下新型空心螺钉固定Pauwels Ⅱ型股骨颈骨折的生物力学性能。方法将10根Sawbones仿真股骨标本首先制作成Pauwels角为50°的Ⅱ型股骨颈骨折模型, 编号后随机分为两组(n=5):实验组与对照组。实验组标本采用"轴心加压+侧方支撑"理念下新型空心螺钉组合固定:轴心螺钉直径为8.5 mm, 侧方螺钉直径为6.5 mm;对照组标本采用传统倒三角形空心螺钉平行加压固定:3枚螺钉直径均为7.3 mm。将标本置于生物力学试验机上, 依次测试静态轴向刚度、5 000个循环60～600 N载荷下位移、极限载荷和极限刚度参数, 比较两组的差异。结果实验组标本的静态轴向刚度[(1 492.00 ± 87.86)N/mm]显著高于对照组标本[(1 200.22 ± 228.06)N/mm], 差异有统计学意义(P<0.05)。实验组和对照组标本循环载荷下的位移分别为(0.44 ± 0.01)、(0.57 ± 0.17)mm, 差异无统计学意义(P>0.05), 但实验组呈现出较低趋势。实验组标本的极限载荷和极限刚度分别为(4 292.61 ± 80...     

交锁钉与加压钢板固定尺骨骨折的生物力学比较

[目的] 对交锁髓内钉与动力加压钢板固定尺骨骨折的生物力学性能进行测试,为临床应用提供理论依据.[方法] 采用12根新鲜尺骨标本,制作成中段横形骨折模型,分别用交锁髓内钉和6孔3.5 mm动力加压钢板固定,髓内钉规格为φ4mm,长200～230 mm.将标本固定于MTS试验机,对其进行抗轴向压缩、抗弯曲、抗扭转的生物力学测试,比较分析抗压刚度、抗弯刚度、抗扭刚度和抗压强度、抗弯强度、抗扭强度.[结果]交锁髓内钉固定的抗轴向压缩刚度、抗弯曲刚度和抗扭转刚度依次为(450.00±38.42)N/mm、(45.64±5.24)N·cm/Deg、(11.42±1.21)N·cm/Deg;6孔3.5mm动力加压钢板固定的抗轴向压缩刚度、抗弯曲刚度和抗扭转刚度分别为(405.40 4-29.26)N/mm、(41.00±4.78)N·cm/Deg、(10.05±1.32)N·cm/Deg.在1000 N轴向压缩载荷作用下,交锁髓内钉和加压钢板固定时尺骨的位移分别为(2.20±0.11)mm和(2.48±0.15)mm;在5 N·m弯曲载荷下,采用交锁髓内钉固定的尺骨的最大桡度为(3.25±0.15)mm,加压钢板固定的最大桡度为(3.60±0.21)mm;在扭转试验中,交锁髓内钉固定能承受扭矩最大达(2.40±0.13)N·m,而加压钢板固定能承受的扭矩为(1.90±0.10)N·m;实验所得的数据采用SPSS.10软件处理,再进行t检验显示具有显著性差异(P<0.05).可见交锁髓内钉在力学刚度和强度上均优于6孔3.5mm动力加压钢板固定.[结论] 交锁髓内钉具有良好的生物力学性能,固定可靠,符合生物学固定的原则.     

新型微创椎弓根钉-板固定系统的生物力学测试

目的 :评估新型微创椎弓根钉-板内固定系统的生物力学强度。方法:根据美国材料测试协会(ASTM)标准构建单钉-棒测试组件,在万能材料试验机上分别对微创椎弓根钉-板、单向椎弓根钉-棒和万向椎弓根钉-棒组件进行生物力学强度测试。测试内容包括静态侧压测试和疲劳测试。在静态侧压测试中使用6套组件,记录组件屈服载荷、屈曲刚度以及失效模式。在疲劳测试中记录完成250万次循环负荷的最大应力数值。结果:微创椎弓根钉-板组件的屈服载荷和屈曲刚度显著低于单向椎弓根钉-棒组件(834.6±74.5N vs 1087.7±59.0N,218.1±22.4N vs 300.0±14.9N,P0.001)。微创椎弓根钉板组件的屈服载荷与万向椎弓根钉-棒组件比较无显著性差异(834.6±74.5N vs 762.8±88.6N,P=0.118);而钉-板组件的刚度显著低于万向钉-棒组件(218.1±22.4N/mm vs 389.5±37.2N/mm,P0.001)。单向椎弓根钉-棒组件的失败模式为连接棒发生塑性形变,万向椎弓根钉-棒组件为"球窝偶联"结构失效,微创椎弓根钉-板组件为钛板的塑性形变和钉-板连接部位失效。在250万次动态侧压疲劳测试中,单向椎弓根钉-棒组件、微创椎弓根钉-板组件和万向椎弓根钉-棒组件分别在450N、450N和350N循环载荷下完成测试。结论:新型微创椎弓根钉-板内固定系统可耐受250万次450N循环载荷作用,同时具有高屈服载荷和低屈曲刚度的特点。     

"轴心加压+侧方支撑"空心螺钉固定Pauwels Ⅱ型股骨颈骨折的力学分析北大核心CSCD

目的探讨"轴心加压+侧方支撑"理念下新型空心螺钉固定PauwelsⅡ型股骨颈骨折的生物力学性能。方法将10根Sawbones仿真股骨标本首先制作成Pauwels角为50°的Ⅱ型股骨颈骨折模型,编号后随机分为两组(n=5):实验组与对照组。实验组标本采用"轴心加压+侧方支撑"理念下新型空心螺钉组合固定:轴心螺钉直径为8.5 mm,侧方螺钉直径为6.5 mm;对照组标本采用传统倒三角形空心螺钉平行加压固定:3枚螺钉直径均为7.3 mm。将标本置于生物力学试验机上,依次测试静态轴向刚度、5000个循环60~600 N载荷下位移、极限载荷和极限刚度参数,比较两组的差异。结果实验组标本的静态轴向刚度[(1492.00±87.86)N/mm]显著高于对照组标本[(1200.22±228.06)N/mm],差异有统计学意义(P<0.05)。实验组和对照组标本循环载荷下的位移分别为(0.44±0.01)、(0.57±0.17)mm,差异无统计学意义(P>0.05),但实验组呈现出较低趋势。实验组标本的极限载荷和极限刚度分别为(4292.61±804.29)N、(1623.55±180.94)N/mm,对照组分别为(4383.64±1423.24)N、(1433.77±289.93)N/mm,两组比较差异均无统计学意义(P>0.05)。结论"轴心加压+侧方支撑"理念下新型空心螺钉固定PauwelsⅡ型股骨颈骨折较传统倒三角形空心螺钉平行加压固定的生物力学性能更优。     

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.     

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.     

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.     

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.     

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.     

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.