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。     

Reduction of Plasma Fibrinogen, Immunoglobulin G, and Immunoglobulin M Concentrations by Immunoadsorption Therapy with Tryptophan and Phenylalanine Adsorbents

Abstract Immunoadsorption (1A) therapy with tryptophan (TR-350) or phenylalanine (PH-350) adsorbents has been used to reduce the concentration of serum antibodies in human lymphocyte antigen (HLA)-immunized patients. Other forms of plasma purification have been reported to reduce the level of fibrinogen, which affects the blood properties. In this study we investigated the effects of IA therapy using both adsorbents on plasma fibrinogen and immunoglobulins G and M in 13 patients (8 patients were treated with TR-350, and 5 patients were treated with PH-350). During each session 1 plasma volume (2.8 ± 0.4 L of plasma) was processed through the immunocolumn and then returned to the patient together with the blood cells. Compared with the pretreatment values, the plasma fibrinogen, IgG, and IgM concentrations were significantly reduced after IA therapy (p < 0.01 for TR-350; p < 0.04 for PH-350). There was a positive correlation between the degree of reduction of plasma proteins and the number of IA treatments given. A nonpara-metric test (Wilcoxon's signed-rank test or the Mann-Whitney test) was used for statistical analysis. We conclude from our study that IA therapy effectively lowers the plasma levels of fibrinogen, IgG, and IgM and thus can be considered a valuable alternative to other blood purification methods.     

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.     

The multiply injured child

Blunt trauma is the principal cause of childhood death in many developed countries. This review outlines the differences between adults and children with respect to resuscitation and treatment of orthopaedic injuries in a child with polytrauma. Recent advances in techniques of fracture stabilization are reported.     

Dilemma of Membrane Biocompatibility and Reuse

Abstract: Numerous articles have been published on the multiple use of dialyzers and on the effect of different reprocessing chemicals and techniques on the dialyzer biocompatibility and performance. The results often appear contradictory, especially those comparing standard biocompatibility parameters. Despite this confusion, a discerning review of the published works allows certain limited conclusions to be drawn. Reprocessing of used hemodialyzers changes the biocompatibility profile of a dialyzer as defined by the parameters complement activation. leukopenia, and cytokine release. The effect of reprocessing depends on the chemicals and reprocessing technique applied and also on the type of membrane polymer being subjected to the reprocessing procedure. Reports of pyrogenic reactions indicate that the flux of the membrane also influences how suitable it is for safe reuse. An increased risk of allergic and pyrogenic reactions appears to be associated with dialyzer reuse. Furthermore, there has been a lack of investigations into the immunologic effect of the layer of adsorbed and chemically altered proteins that remains on the inner surface of reprocessed dialyzers. We conclude that the clinical benefit of dialyzer reuse cannot be generally accepted from a biocompatibility point of view.     

The analgesic effect of racemic ketamine in patients with chronic ischemic pain due to lower extremity arteriosclerosis obliterans

Background : Ketamine in sub-dissociative doses has been shown to have analgesic and phantom-Limb pain, where conventional treatment has often failed. Chronic ischemic pain due to lower extremity arteriosclerosis obliterans often responds poorly to analgesics, and the pain-generating mechanisms are not well understood.
Methods : Eight patients with rest pain in the lower extremity due to arteriosclerosis obliterans were given sub-dissociative doses of 0.15, 0.30, or 0.45 mg/kg racemic ketamine and morphine 10 mg as a 5-min infusion on four separate days in a cross-over, double-blind, randomised protocol. Plasma levels of (S)- and (R)-ketamine and their nor-metabolites were analysed with an enantioselective high-performance liquid chromatography (HPLC) method. Pain levels were evaluated with a visual analogue scale (VAS).
Results : Individual pain levels were highly variable during and after all the infusions but the pooled pain levels showed a dose-dependent analgesic effect of ketamine with a transient but complete pain relief in all patients at the highest dose (0.45 mg/ kg). Side-effects, mainly disturbed cognition and perception, were pronounced and dose-dependent. Morphine 10 mg had an analgesic peak at 20 min and 5/8 patients had complete pain relief. The remaining 3 patients also had high baseline pain scores, indicating a higher analgesic potency for the 0.30 and 0.45 mg/ kg ketamine doses than for morphine 10 mg.
Conclusion : We have demonstrated a potent dose-dependent analgesic effect of racemic ketamine in clinical ischemic pain. Due to a narrow therapeutic window, this analgesic effect is probably best utilised in combination with other analgesics.     

Intravenous endotoxin does not increase tissue extravasation of albumin in rats

Background : It is unclear whether activation of the inducible nitric oxide synthase (iNOS) increases or decreases the extravasation of plasma.
Methods : Chloralose anaesthetised male Wistar rats received E. coli lipopolysacharide (LPS), 3 mg kg^-1 i.v., or the corresponding volume of saline, 3 or 5 h before the end of the experiment. Mean arterial pressure (MAP) and heart rate (HR) were recorded. Tissue clearance of radio-labelled albumin, during the last 2 h of each experiment, was determined by a double-isotope method. In separate animals, the serum concentration of nitrite and nitrate was determined, 5 h after LPS or the solvent.
Main Results : LPS initially decreased MAP and lastingly increased HR. In the 3-h LPS animals (n=8), tissue plasma clearance was lower in the heart and calf muscle and increased only in diaphragm, compared to corresponding control animals (n=8). In the 5-h LPS rats, clearance was lowered (n=8) in the entire gastrointestinal tract and in testes, compared to controls (n=8). The serum nitrite/nitrate concentration was higher in animals given LPS (n=6) than in controls (n=6).
Conclusion : After LPS, tissue clearance of albumin was not increased in any major tissue, in spite of increased serum levels of NO end products. Apparently, after activation of iNOS, the augmented release of NO is not necessarily associated with increased albumin extravasation.     

Adrenaline markedly improves thoracic epidural analgesia produced by a low-dose infusion of bupivacaine, fentanyl and adrenaline after major surgery: A randomised, double-blind, cross-over study with and without adrenaline

Background: Basic pharmacological research indicates that there are synergistic antinociceptive effects at the spinal cord level between adrenaline, fentanyl and bupivacaine. Our clinical experience with such a mixture in a thoracic epidural infusion after major surgery confirms this. The objectives of the present study were to evaluate the effects on postoperative pain intensity, pain relief and side effects when removing adrenaline from this triple epidural mixture. Methods: A prospective, randomised, double-blind, cross-over study was carried out in 24 patients after major thoracic or abdominal surgery. Patients with only mild pain when coughing during a titrated thoracic epidural infusion of about 10 ml · h^?1 of bupivacaine 1 mg · ml^?1, fentanyl 2 μg · ml^?1, and adrenaline 2 μg · ml^?1 were included. On the 1^st and 2^nd postoperative days each patient was given a double-blind epidural infusion, at the same rate, with or without adrenaline. The effect was observed for 4 h or until pain when coughing became unacceptable in spite of a rescue analgesic procedure. Rescue analgesia consisted of up to two epidural bolus injections per hour and i.v. morphine if necessary. All patients received rectal paracetamol 1 g, every 8 h. Fentanyl serum concentrations were measured with a radioimmunoassay technique at the start and end of each study period. Main outcome measures were extent of sensory blockade and pain intensity at rest and when coughing, evaluated by a visual analogue scale, a verbal categorical rating scale, the Prince Henry Hospital pain score, and an overall quality of pain relief score. Results: The number of hypaesthetic dermatomal segments decreased (P <0.001) and pain intensity at rest and when coughing increased (P <0.001) when adrenaline was omitted from the triple epidural mixture. This change started within the first hour after removing adrenaline. After 3 h pain intensity when coughing had increased to unacceptable levels in spite of rescue analgesia (epidural bolus injections and i.v. morphine). Within 15–20 min after restarting the triple epidural mixture with adrenaline, pain intensity was again reduced to mild pain when coughing. Serum concentration of fentanyl doubled from 0.22 to 0.45 ng · ml^?1 (P <0.01), and there was more sedation during the period without adrenaline. Conclusions: Adrenaline increases sensory block and improves the pain-relieving effect of a mixture of bupivacaine and fentanyl infused epidurally at a thoracic level after major thoracic or abdominal surgery. Serum fentanyl concentrations doubled and sedation increased when adrenaline was removed from the epidural infusion, indicating more rapid vascular absorption and systemic effects of fentanyl.