球形探针技术在椎弓根螺钉置钉术中的应用

 目的 通过与传统徒手置钉术的比较, 评价一种新的椎弓根螺钉置钉技术, 即应用椎弓根球形探针系统置入椎弓根螺钉的准确率。方法 自 2009年 5月至 2010年 6月, 对脊柱侧凸、腰椎滑 脱、脊柱骨折等疾病需行颈胸腰椎椎弓根钉内固定的患者, 术中应用椎弓根球形探针置入椎弓根螺钉。 该探针为医用不锈钢制成, 包括一个球端、杆和柄, 金属球端的直径分别有 1.5、2.5、3.0、3.5 mm四种, 其 中直径 1.5 mm的探针具有较强的硬度和一定的弹性。球形探针技术要点: 按标准椎弓根螺钉进钉点定 位, 高速磨钻去除皮质骨, 将椎弓根球形探针按直径从小到大±次缓慢敲入椎弓根内直至达到椎体前 方骨皮质。术后采用 CT扫描评价椎弓根螺钉钉道情况。并与采用传统徒手技术的病例资料进行对比。 结果采用球形探针技术共置入 312枚椎弓根螺钉, 传统徒手技术置入 276枚。术后 CT扫描显示球形 探针技术组颈椎、胸椎、腰椎椎弓根螺钉钉道准确率为 100%, 无一例穿出椎弓根骨皮质。传统徒手技术 组准确率为 78%, 共有 61枚螺钉(22%)位置不良, 23枚(8.3%)穿透椎弓根内侧骨皮质, 38枚(13.7%) 穿透外侧骨皮质。两组置钉准确率的差异具有统计学意义。所有患者术中和术后均未出现神经、血管和内脏损伤等并发症。结论 与传统徒手置钉技术相比, 椎弓根球形探针置钉技术, 可准确地置入椎弓根钉, 避免因螺钉误置所导致的术后并发症。     

L4/L5节段椎弓根螺钉进针点选择的新方法

目的 设计一种新的L₄/L₅节段椎弓根螺钉进针点的定位方法,并评估其准确性及安全性。方法 2019年1月-2020年8月,中国人民解放军北部战区总医院采用椎间融合并椎弓根螺钉内固定术治疗L₄/L₅节段椎间盘突出症患者98例,其中53例（观察组）采用新的进针点定位法（选择横突上缘下方4 mm与上关节突外缘交点处作为进针点）,45例（对照组）采用人字嵴法进行进针点定位。记录并比较2组手术时间、术中出血量、首次置钉准确率、置钉前切口显露时间、螺钉与椎弓根皮质关系及并发症发生情况。采用疼痛视觉模拟量表（VAS）评分评估疼痛程度。结果 观察组共置入螺钉212枚,对照组置入180枚。2组手术时间、术中出血量、首次置钉准确率、螺钉与椎弓根皮质关系、术后VAS评分差异均无统计学意义（P>0.05）;观察组置钉前切口显露时间短于对照组,差异有统计学意义（P<0.05）。结论 L₄/L₅节段置入椎弓根螺钉,以椎体横突上缘下方4 mm与上关节突外缘交点处作为进针点,可获得与人字嵴定位法相同的置钉准确率和安全性,并可减少置钉前切口显露时间。     

改良Rao穿破分级评估胸腰椎椎弓根螺钉的准确性及其临床意义

目的 探讨改良Rao穿破分级评估胸腰椎椎弓根螺钉的准确性及其临床意义。方法 采用改良Rao穿破分级标准,对2010年1月至2017年6月我科收治的经胸腰椎开放后路椎弓根置钉术治疗的40例胸腰椎病变病人的术后CT影像资料进行回顾性分析。收集病人的一般资料、并发症情况,并对术后各椎弓根螺钉发生穿透的方向和程度进行统计,分析各椎弓根螺钉的穿透率。结果 共置入254枚螺钉,其中33枚螺钉穿出,置钉总准确率为87.01%（221/254）。L₅的置钉准确性最低,仅为78.26%（36/46）,且其A、D型的穿透率和2级及以上的穿透率明显高于其他椎体。畸形椎弓根的穿透率明显高于退行性变与骨折,差异均具有统计学意义（P均＜0.05）。结论 改良Rao穿破分级更加精准、实用,胸腰椎畸形的椎弓根穿透率明显高于退行性变和骨折,而L₅节段2级及以上穿透率均明显高于其他胸腰椎,临床上应引起足够重视。     

机器人辅助与徒手置钉在腰椎翻修术早期结果比较

[目的]比较Renaissance机器人系统辅助椎弓根螺钉置入与徒手椎弓根螺钉置入在腰椎翻修手术中的安全性及准确性。[方法]回顾性分析2018年1月~2018年12月在本院行腰椎后路翻修手术的病例69例,其中使用Renaissance机器人系统辅助椎弓根螺钉置入共31例,使用传统徒手椎弓根螺钉置入38例。记录临床资料,并根据术后CT对螺钉精度进行Gertzbein Robbins分级,比较螺钉置入准确性。[结果]两组患者手术时间、术后出血量及手术相关并发症等差异无统计学意义(P0.05)。机器人组术中出血量、术中透视次数显著少于徒手组(P0.05)。机器人辅助组共置入螺钉152枚,术后CT评估显示:A级置钉137枚,B级置钉11枚,C级置钉4枚,没有D、E级置钉,置钉准确率97.37%。徒手组共置入螺钉194枚,术后CT评估显示:A级置钉129枚,B级置钉48枚,C级置钉15枚,D级置钉2枚,没有发现E级置钉,置钉准确率91.24%。在螺钉精度分级及螺钉准确性方面,机器人组优于徒手组,差异具有统计学意义(P0.05)。[结论]与徒手置钉技术相比,Renaissance机器人系统辅助椎弓根螺钉置入在腰椎翻修手术中具有置钉精度高、且术中出血及术中透视次数少的优势。     

多层螺旋CT三维重建技术在胸腰椎骨折经椎弓根螺钉内固定术中的应用价值

目的:探讨多层螺旋CT(MSCT)三维重建技术在胸腰椎骨折患者经椎弓根螺钉内固定术中的应用价值。方法:2007年1月~2008年12月,78例胸腰椎骨折患者在我院行椎弓根螺钉内固定术,其中38例使用传统置钉法(Weinstein法或AO法)进行椎弓根螺钉置入(A组),40例采用MSCT三维重建设计钉道的置钉方法进行螺钉置入(B组),术后两组均复查胸腰椎正、侧位X线片和CT了解置入螺钉位置情况,应用Lonstein等的方法评判置钉准确率。结果:78例患者共置入椎弓根螺钉436枚,A组38例共置入212枚,12例32枚螺钉穿破椎弓根皮质,其中穿破椎弓根内外皮质21枚,穿破椎弓根上下皮质11枚,置钉准确率84.91%;B组40例共置入224枚,5例6枚螺钉穿破椎弓根皮质,其中穿破椎弓根内外皮质4枚,穿破椎弓根上下皮质2枚,置钉准确率97.33%。两组置钉准确率有统计学差异(P<0.05)。结论:胸腰椎骨折患者行椎弓根螺钉内固定时应用MSCT三维重建设计钉道的置钉方法较传统置钉方法成功率高。     

改良3D打印导板辅助颈椎椎弓根螺钉置钉的准确性研究

【摘要】 目的：探讨改良3D打印导板辅助颈椎椎弓根螺钉置钉的准确性。方法：回顾性分析2016年1月~2023年1月在我院行颈椎后路椎弓根螺钉内固定手术的60例患者的临床资料,其中男30例,女30例,年龄58.7±13.8岁（17~84岁）;根据颈椎后路手术是否使用导板辅助置钉分为导板组及徒手置钉组。导板组（30例）采用改良3D打印导板辅助颈椎椎弓根置钉,徒手置钉组（30例）采用角度尺辅助颈椎弓根置钉,两组患者年龄、性别、术前诊断无统计学差异（P＞0.05）。所有患者术后1周行颈椎CT扫描,按照Kaneyama标准判断椎弓根置钉准确性：0级,螺钉完全处于椎弓根中,没有穿破骨皮质;1级,螺钉穿破皮质<螺钉直径的50％;2级,螺钉穿破皮质≥螺钉直径的50％但没完全穿出;3级,完全穿出骨皮质。记录椎弓根置钉准确率（0级+1级螺钉占比）及因螺钉误置导致的血管神经损伤、切口感染、脑脊液漏、螺钉松动断裂等并发症。结果：导板组共置入椎弓根螺钉152枚,其中0级74枚,1级68枚,2级10枚,3级0枚,置钉准确率93.4%;徒手置钉组共置入椎弓根螺钉136枚,其中0级53枚,1级61枚,2级18枚,3级4枚,置钉准确率83.8%,导板组置钉准确率高于徒手置钉组（P＜0.05）。所有患者均未出现因椎弓根螺钉误置导致的血管神经损伤、切口感染及脑脊液漏等相关并发症。所有患者随访5～29个月（14.2±7.7个月）,无内固定松动、断裂等并发症。结论：改良3D打印导板辅助颈椎椎弓根置钉可提高置钉精准度。     

CT导航系统在重度僵硬性脊柱畸形矫形术中的置钉准确性及临床疗效评估

目的 评估CT导航系统在重度僵硬性脊柱畸形矫形术中的置钉准确性及临床疗效。方法 回顾性纳入2017年1月至2022年12月我院收治的43例重度僵硬性脊柱畸形病人,其中21例采用术中CT导航系统辅助置钉（421枚螺钉）的病人纳入导航组,22例采用传统徒手置钉（386枚螺钉）的病人纳入徒手组。收集两组病人的一般资料、手术前后主弯Cobb角、矫正率、置钉数量以及顶椎区域置钉数量。采用Gertzbein和Robbins分级分析两组病人术后CT图像,以评估置钉准确性。结果 两组病人手术前后主弯Cobb角及矫正率比较,差异无统计学意义（P＞0.05）。较之徒手组,导航组置入于顶椎区域的螺钉数量更多［（7.37±1.12）个 vs. （6.45±0.96）个］,手术时间更长［（376.19±56.26） min vs. （331.36±50.92） min］,差异均有统计学意义（P＜0.05）;但出血量无明显差异（P＞0.05）。两组病人总体置钉准确率比较,差异无统计学意义（P=0.586）;但在顶椎区域,导航组置钉准确率显著高于徒手组（96.1% vs. 89.4%,χ²=5.051,P=0.025）。此外,术中CT导航系统明显降低了椎弓根内侧穿孔率（χ²=5.122,P=0.024）。结论 CT导航系统可有效提高重度僵硬性脊柱畸形顶椎区域的置钉准确性。     

青少年特发性脊柱侧凸应用Ball tip技术置入椎弓根钉的准确性

目的针对需要手术治疗的青少年特发性脊柱侧凸,通过与传统徒手置钉技术比较来评价一种新的椎弓根置钉技术—Ball tip技术置入椎弓根钉的准确性。方法自2009年5月~2011年5月,对28例青少年特发性脊柱侧凸,术中应用椎弓根球形探针(ball tip probe)置入椎弓根。结果采用Ball tip技术共置入193枚椎弓根钉,传统徒手技术置入161枚螺钉。术后CT扫描显示Ball tip组椎弓根钉钉道准确率为89.1%,共有21枚(10.9%)置钉不良螺钉,其中5枚(2.6%)穿透椎弓根内侧骨皮质,16枚(8.3%)穿透外侧骨皮质。徒手置钉组准确率为75.2%,共有40枚(24.8%)置钉不良螺钉,其中11枚(6.8%)穿透椎弓根内侧骨皮质,29枚(18.0%)穿透外侧骨皮质。两组置钉准确率的差异具有统计学意义(P<0.01),两组螺钉穿透椎弓根内侧、外侧骨皮质的差异具有统计学意义(P<0.05)。结论与传统徒手置钉技术相比,椎弓根Ball tip技术,可准确地置入椎弓根钉,减少因螺钉误置所导致的术后并发症。     

角度控制组合式椎弓根螺钉植入工具的临床应用

目的观察角度控制组合式椎弓根螺钉植入工具在腰椎椎弓根螺钉植入中的应用价值。方法将行后路椎弓根螺钉植入内固定术的61例腰椎疾患患者按随机区组设计分为角度组(使用角度控制组合式椎弓根螺钉植入工具,31例)和目测组(依靠术者目测角度,30例)。比较两组患者在置钉时间、准确率、穿出率等方面是否存在差异。结果角度组共置入椎弓根螺钉182枚,置钉用时(2. 5±1. 2) min/枚,置钉准确率为97. 2%;目测组共置钉178枚,置钉用时(3. 0±1. 5) min/枚,准确率为88. 2%。角度组置钉时间明显短于目测组(P 0. 05),置钉准确率明显高于目测组(P 0. 01),螺钉穿出率明显低于目测组(P 0. 01)。结论在腰椎椎弓根螺钉植入术中,采用角度控制组合式椎弓根螺钉植入工具的置钉准确率有明显优势,具有临床应用价值。     

纯A-P技术经皮椎弓根螺钉内固定术治疗胸腰椎压缩性骨折的临床疗效

目的 探讨纯A-P技术经皮椎弓根螺钉内固定手术治疗胸腰椎压缩性骨折的临床疗效。方法 回顾性分析2013年1月至2016年1月我院采用经皮椎弓根螺钉内固定术治疗胸腰椎压缩性骨折的病人85例,根据手术方式不同分为两组：观察组45例,采用纯A-P技术经皮单平面椎弓根螺钉内固定术;对照组40例,采用传统开放椎弓根螺钉内固定术。收集并比较两组病人的围手术期相关指标、术后功能恢复情况、影像学指标及置钉准确率。结果 病人平均随访时间为14个月。观察组的手术时间、术中出血量、切口长度、术后住院时间均明显低于对照组（P均＜0.05）;两组的置钉准确率、透视次数比较,差异均无统计学意义（P均＞0.05）。两组术后的矢状面后凸Cobb''s角、Oswestry功能障碍指数（Oswestry disability index, ODI）、疼痛视觉模拟量表（visual analogue scale, VAS）评分均较术前明显降低（P均＜0.05）,伤椎椎体前缘高度、伤椎椎体后缘高度均较术前明显升高（P均＜0.05）,但两组间术后指标比较,差异均无统计学意义（P均＞0.05）。结论 纯A-P技术经皮椎弓根螺钉内固定术治疗胸腰椎压缩性骨折具有创伤小、出血少、术后功能恢复快等优点,建议在大多数医院推广。     

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.