胫骨高位截骨术治疗膝骨关节炎并膝内翻体会

目的探讨胫骨高位截骨术治疗膝关节骨关节炎并内翻畸形的疗效。方法 2007年8月至2010年8月采用胫骨高位截骨术对35例50膝的膝关节骨关节炎并膝内翻患者进行治疗。手术前后拍摄患侧下肢负重位全长X线片,测量内翻角、FTA角、内外侧关节间隙距离及关节活动度,同时对患者进行HSS评分对比。结果对34例患者平均随访23.7个月。术后X线片示膝关节内侧间隙明显增宽,膝关节内翻畸形基本纠正,膝关节疼痛症状明显缓解,优良率为91.2%。结论胫骨高位截骨术对膝关节骨关节炎并膝内翻畸形患者有明显的疗效,早、中期效果较好。 更多还原     

开放胫骨高位楔形截骨术治疗膝关节内翻畸形

目的 评价双平面开放胫骨高位楔形截骨治疗成人膝关节内翻畸形的手术效果.方法 回顾性分析2001年6月至2008年7月存在膝关节内侧单间室退行性改变伴内翻畸形且进行双平面开放胫骨高位楔形截骨术治疗的12例患者的一般资料.术前膝内翻畸形5.0°～19.0°,平均11.5°;膝关节屈伸活动度大于90°;不伴有其他关节间室病变;1例伴有外侧副韧带及前交叉韧带断裂,行韧带重建手术后二期进行开放截骨矫形术.术前膝关节症状以内侧间室疼痛为主.手术前后测量患者关节活动度的大小,并对患者进行Lysholm评分.术后对患者进行主观满意度调查.结果 12例患者术后平均随访时间32.5个月.截骨处至术后12～16周均获得骨性愈合.矫正角度5.5°～18.0°,平均9.5°.在随访期间内X线检查下肢力线维持在术后水平,内外侧间室及髌股间室均未发现明显退变进展.手术总体效果优良率为83.3%,Lysholm评分、内翻角度变化在手术前后均有统计学显著性差异.结论 双平面开放胫骨高位楔形截骨术对中青年膝关节内翻畸形伴单间室退行性改变有良好的早、中期效果.     

胫骨高位截骨改良Giebel刃形钢板内固定治疗伴膝内翻的膝骨性关节炎

目的：观察胫骨高位截骨改良Giebel刃形钢板内固定治疗伴膝内翻畸形的膝骨性关节炎的临床疗效。方法：7例10个伴膝内翻畸形的膝骨性关节炎患者行胫骨高位截骨改良Giebel刃形钢板内固定术，术后观察x线及临床症状的变化。结果：所有病例均获得随访，随访时间8～24个月，平均16个月，截骨部位临床愈合时间为8～12周，平均10周，无1例不愈合，术后X线片示膝关节内侧间隙明显增宽，膝关节内翻畸形基本纠正，优良率为90％。结论：胫骨高位截骨改良Giebel刃形钢板内固定具有手术创伤小，固定牢固，早期功能锻炼，术后恢复快等优点。是治疗伴膝内翻畸形的膝骨性关节炎较年轻患者的一种首选方法。     

胫骨高位截骨改良Giebel刃形钢板内固定治疗伴膝内翻的膝骨性关节炎

目的:观察胫骨高位截骨改良Giebel刃形钢板内固定治疗伴膝内翻畸形的膝骨性关节炎的临床疗效.方法:7例10个伴膝内翻畸形的膝骨性关节炎患者行胫骨高位截骨改良Giebel刃形钢板内固定术,术后观察X线及临床症状的变化.结果:所有病例均获得随访,随访时间8～24个月,平均16个月,截骨部位临床愈合时间为8～12周,平均10周,无1例不愈合,术后X线片示膝关节内侧间隙明显增宽,膝关节内翻畸形基本纠正,优良率为90%.结论:胫骨高位截骨改良Giebel刃形钢板内固定具有手术创伤小,固定牢固,早期功能锻炼,术后恢复快等优点.是治疗伴膝内翻畸形的膝骨性关节炎较年轻患者的一种首选方法.     

胫骨高位截骨Giebel内固定治疗膝内翻的疗效观察

目的探讨胫骨高位截骨Giebel内固定术治疗膝内翻畸形的效果。方法对18膝内翻畸形患者采用胫骨高位截骨Giebel内固定。手术前后摄双下肢负重位全长X线片，测量内翻角、机械轴线和斛剖轴线并记录。结果18例均获得随访，时间8～29个月。术后1例出现腓总神经麻痹，经治疗3个月后肌力感觉完全恢复。截骨处在术后12～14周均达到骨性愈合，疼痛症状均明显缓解或消失，摄片检查下肢力线维持在术后水平。结论胫骨高位截骨Giebel内固定术治疗膝内翻畸形效果确实可靠，骨愈合率高，推迟了膝关节置换的年龄。     

综合手术治疗膝关节骨性关节炎合并膝内翻

目的 为使膝关节骨性关节炎合并膝内翻的年轻患者延缓行全膝关节置换,探讨股骨内髁马赛克植骨、髌骨成形并胫骨高位截骨综合手术治疗膝关节骨性关节炎合并膝内翻的临床疗效.方法 2004年6月-2006 年2月,对8例10膝骨性关节炎合并膝内翻患者行综合手术治疗.其中男2例3膝,女6例7膝;年龄42～56岁.左膝3例,右膝3例,双膝2例.患者均表现为行走或站久后疼痛.X 线片示股胫关节及髌骨边缘骨质增生,以内侧为重,髌股关节间隙变窄或消失,膝关节内侧间隙明显变窄.股胫角185～200°,平均 190°;HSS 膝关节评分为55～75分,平均60分.膝痛1～12年,平均5年. 结果 术后切口均Ⅰ期愈合,无早期并发症发生.患者均获随访7～24个月,平均15个月.患者截骨部位均于8～11 周达临床愈合,平均9周.股胫角矫正15～30°,平均 20°,基本恢复正常负重力线,膝关节外翻角 10°.术后关节活动度为 100～120°,较术前增加 5～20°,平均增加 10°.X 线片示膝关节内翻畸形基本纠正,截骨处无移位,内固定无松动、断裂.术后6个月HSS膝关节评分75～88分,平均80分. 结论 股骨内髁马赛克植骨使关节软骨得到一定程度的修复重建,髌骨成形有效解决膝前区疼痛,胫骨高位截骨矫正异常负重力线,三者结合,疗效肯定.     

胫骨高位楔形截骨治疗创伤性膝关节内翻畸形的临床研究

目的探讨胫骨高位楔形截骨治疗成人膝关节内翻畸形并发单间室退变的应用价值。方法在2000年6月至2008年6月间,对11例（男7例,女4例,平均39岁）存在膝关节内侧单间室退行性改变伴内翻畸形患者进行胫骨高位楔形截骨术治疗。术前膝内翻畸形4°。-18°,平均10．5°;不伴有其他关节间室病变;6例伴有内、外侧副韧带或交叉韧带断裂,行韧带重建手术后二期进行截骨矫形术。术前膝关节症状以内侧间室疼痛为主。8例行闭合型楔形截骨术,3例行开放型楔形截骨术,手术前后测量患者关节活动度的大小,并对患者进行Lysholm评分,术前平均41．5分。术后对患者进行主观满意度调查。结果术后随访平均22．5个月。无神经血管损伤,内固定失败等并发症出现,截骨处均获得骨性愈合,矫正角度5°-17．5°。X线检查下肢力线维持在术后水平,关节间室均未发现明显退变进展。手术总体效果优良率为90．9％,术后Lysholm评分平均72．5分（t=-26．65,P〈0．01）,内翻角度术后为1．05°（t=4．49,P〈0．01）。结论胫骨高位楔形截骨术可有效用于中青年膝关节内翻畸形伴单间室退行性改变患者。     

胫骨高位截骨手术并发症23例次分析

[目的] 探讨胫骨高位截骨手术并发症的发生情况，并提出预防和治疗措施。[方法]2000年1月～2004年10月采用胫骨高位截骨术治疗膝骨关节炎合并内翻畸形患者126人，21人发生手术并发症，男4例，女17例；年龄48～64岁，平均61岁。术前拍摄站立膝关节正位X线片，测量股骨一胫骨角，计算截骨角度，采用外侧闭合胫骨高位截骨术矫正膝内翻畸形。[结果] 术后随访6～12个月，平均7．5个月。共21名患者发生各类并发症23例次．发生率为16．7％。其中发生胫骨骨折4例，腓总神经麻痹3例，出现深静脉血栓形成5例，膝内翻复发病例6例，内固定失败4例（其中2例合并膝内翻复发），感染1例。[结论] 降低胫骨高位截骨手术并发症需要术者熟悉局部解剖和精确的术前设计，提高手术技巧及完善的围手术期护理。     

胫骨高位嵌插截骨与传统高位截骨治疗高龄屈曲型膝内侧间隙骨关节炎的对比研究

目的:报告胫骨高位嵌插截骨治疗高龄屈曲型膝内侧间隙骨关节炎的方法疗效,并与传统高位胫骨截骨的疗效进行比较。方法:2003年7月至2007年7月对年龄60～82岁,病史3～20年,屈曲度7°～19°的膝内侧间隙骨关节炎的30例患者随机分成2组,分别进行胫骨高位嵌插截骨和传统高位截骨手术治疗。术后观察骨折愈合时间、膝关节内翻畸形和屈曲畸形恢复、膝关节功能恢复等情况。要求患者术后第4、6、8、9、10、12、14、16周及5、7、9、12个月复查,记录骨折愈合时间及内翻、屈曲角度纠正情况。术后12个月时根据Lysholm膝关节评分标准进行评分,并对2组的疗效进行比较。结果:胫骨高位嵌插截骨组平均骨折愈合时间(9.26±2.23)周,传统高位截骨组平均(11.53±3.15)周,2组相比差异有统计学意义(P0.05)。膝关节功能恢复方面,术后1年,根据Lysholm评分标准进行评分,胫骨高位嵌插截骨平均(88.5±4.4)分,优14例,良1例;传统高位截骨组平均(78.1±5.7)分,优8例,良5例,可2例。胫骨高位嵌插截骨组术后膝关节伸直位角度0°～-1.1°,术后平均矫正(13±3.3)°;传统高位截骨组术后膝关节伸直位角度与术前相同,为(14°±3.3)°。两组术后站立位X线测量,FTA平均170.2°(l69.1°～172.3°),平均矫正12.3°～12.5°。结论:胫骨高位嵌插截骨手术治疗膝关节内侧间隙骨关节炎缩短了骨折愈合时间,同时矫正了膝关节内翻畸形和屈曲畸形,更好地恢复了膝关节的功能,此手术方式明显优于传统的高位截骨术。     

胫骨近端截骨联合膝关节后外侧重建治疗儿麻后遗症严重膝内翻

[目的]胫骨近端截骨术联合采用股二头肌长头腱重建膝关节后外侧结构并探讨其在儿麻后遗症严重膝内翻畸形矫正中的临床效果。[方法]2011年8月~2015年8月对7例儿麻后遗症严重膝内翻畸形患者,一期均行胫骨近端截骨术,二期取内固定时,同时采用股二头肌长头腱重建膝关节后外侧结构。[结果]一期胫骨近端截骨术后均随访20~48个月,平均25.40个月。在非负重状态下,所有胫骨内翻畸形均矫正;在负重状态下,术前膝内翻角度30°~45°,平均37.10°,术后膝内翻角度8°~14°,平均11.70°,矫正角度20°~31°,平均25.4°,所有膝内翻畸形较术前有改善。截骨端愈合时间3~5个月,平均3.50个月。二期膝关节后外侧重建术后随访12~24个月,术后12个月,完全伸膝位无内翻不稳;屈膝30°,Ⅰ度内翻不稳1例;屈膝30°,患侧小腿外旋较健侧增加1例。术后24个月,患膝后外侧结构的稳定性无明显改变,下肢力线恢复满意。[结论]胫骨近端截骨术可以纠正胫骨内翻畸形,改善膝内翻畸形;采用股二头肌长头腱重建膝外侧副韧带和腘肌腱,能够有效恢复膝关节后外侧结构的稳定性;两者联合应用在儿麻后遗症严重膝内翻畸形矫正中可以取得较好疗效。     

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.