基层医院输尿管镜钬激光碎石术治疗输尿管结石的综合疗效分析

目的探讨基层医院输尿管镜钬激光碎石术治疗输尿管结石的综合疗效、影响因素及安全性。方法回顾性分析2010年6月至2013年12月间采用输尿管镜钬激光碎石术治疗输尿管结石104例的临床资料,其中输尿管上段结石22例,中、下段结石82例。结果97例一期碎石成功,总体碎石清石成功率为93．2％（97／104）,其中上段结石的一期清石率为86．3％（19／22）,中、下段结石为97．6％（80／82）。手术时间为12～105min,平均（44．5±21,7）min,术后平均3～7d,平均（4．5±1。5）d。3例结石术中返回肾盂,术后改体外冲击波碎石治疗;4例因输尿管严重扭曲置镜失败,改开放手术;4例输尿管穿孔,置双J管1个月后痊愈,无输尿管撕脱、断裂等严重并发症,12例术后出现泌尿系感染。术后随访1～12个月,平均4个月,1个月内结石排净率为100％。结论在基层医院开展输尿管镜钬激光碎石术治疗输尿管结石安全、疗效可靠。     

经输尿管镜钬激光碎石治疗输尿管结石

目的探讨输尿管镜钬激光碎石术治疗输尿管结石的有效性和安全性。方法回顾性分析59例采用输尿管镜钬激光碎石治疗输尿管结石的患者资料。男37例，女22例，平均54．3岁。结石位于输尿管上段16例，中段13例，下段30例。结石直径0．7—1．8cm，平均1．05cm。结果单次碎石成功率为90％（53／59），其中上段结石单次碎石成功率为69％（11／16），中、下段为98％（42／43）。平均手术时间32．2min，术中无输尿管穿孔等并发症发生，平均住院2．9天。57例随访1-3个月，结石排净率98％（56／57），无输尿管狭窄发生。结论输尿管镜钬激光碎石治疗输尿管结石创伤少，成功率高，可作为输尿管结石特别是中、下段结石首选的治疗方法。     

输尿管镜下双频双脉冲激光粉碎上段输尿管结石

目的评价U-100双频双脉冲激光经输尿管镜粉碎七段输尿管结石的疗效。方法回顺性分析85例采用U－100双频双脉冲激光碎石器经输球管镜治疗的上段输尿管结石患者的临床资料。结果一次碎石成功率为88．2％（75／85）。平均手术时间35（15～60）min，平均激光工作时间2．8（1～5）min。碎石后平均15（7～28）d结石排净。其中，5例因结6被息肉包裹或其远端输尿管紧闭而直接伸进光纤行盲目碎石，有4例获得成功。10例一次碎石失败的原因为：结石冲入肾盂6例，插镜失败2例，碎石不完全2例。无一例发生输尿管穿孔、感染等行发症。结论U－100双频双脉冲激光能迅速高效地粉碎上段输尿管结石，对正常输尿管壁无损伤。     

输尿管软镜钬激光碎石术治疗婴幼儿上尿路结石

目的探讨输尿管软镜联合钬激光治疗婴幼儿（<2岁）上尿路结石的可行性与有效性。 方法回顾性分析我科自2016年1月至2018年2月应用输尿管软镜治疗婴幼儿上尿路结石62例（77侧）。其中男37例,女25例,均为维吾尔族,年龄8～24个月,单侧上尿路结石47例,双侧上尿路结石15例。输尿管上段结石19侧,肾盂结石31侧,肾上盏结石18侧,下盏结石9侧,结石最大径8～25 mm。所有患儿均Ⅰ期置入双J管被动扩张输尿管2周,Ⅱ期采用导丝引导下直接置入输尿管软镜,配合200 μm钬激光光纤碎石,激光功率为20～30 W,术后留置双J管2～3周。 结果62例均入镜成功,51例行一次碎石手术（双侧上尿路结石6例）,9例双侧上尿路结石行两次碎石手术,2例下盏结石未能寻及继续观察。术后住院3～5 d,术后8周复查67侧结石排尽,结石清除率87.0%（67/77）,平均手术时间为35 min（20～55 min）。 结论输尿管软镜联合钬激光碎石治疗婴幼儿上尿路结石,有较高的清石率和临床安全性。     

双频双脉冲激光碎石联合坦索罗辛治疗输尿管结石221例分析

目的：探讨双频双脉冲U-100掺钕钇铝石榴石（Nd：YAG）激光输尿管硬镜技术联合药物排石治疗输尿管结石的临床效果。方法：采用双频双脉冲U100Nd：YAG激光碎石器及输尿管硬镜对221例输尿管结石（直径10～25mm）患者进行碎石治疗，配合术后口服坦索罗辛0．4mg／d，共28天。结果：结石碎石率分别为：上段结石76．2％，中段90．2％，下段97．9％；19例未成功，其中11例上段结石上移至肾脏，2例上段输尿管扭曲，6例输尿管狭窄置镜失畋。术后1个月结石排尽率为91．4％（同期单纯ESWL为75．6％，单纯输尿管镜碎石为82．3％，P〈O．05）。结论：U100激光结合口服坦索罗辛治疗输尿管结石（直径10～25mm）安全、有效，可明显提高结石清除率。     

输尿管镜钬激光碎石术治疗输尿管结石

目的：探讨输尿管镜钬激光碎石术治疗输尿管结石的有效性和安全性。方法：回顾性分析216例应用经输尿管镜钬激光碎石术治疗的输尿管结石患者资料。男133例,女83例;年龄20～68岁,平均49岁。上段结石48例,中段58例,下段110例。结石直径0．7～2．6cm,平均1．4cm。结果：单次碎石成功率为98．1％（212／216）,其中上段结石单次碎石成功率为91．6％（44／48）,中、下段为100％（168／168）。平均手术时间29min,212例术后平均住院3．5天。术后随访2周～3个月,结石排净率99％（210／212）。结论：输尿管镜钬激光碎石术治疗输尿管结石高效、安全,可作为输尿管结石特别是中下段结石首选的治疗方法。     

输尿管镜钬激光碎石术治疗输尿管结石（附677例报告）

目的探讨输尿管镜钬激光碎石术治疗输尿管结石的疗效。方法回顾性分析2003年6月～2012年6月应用输尿管镜钬激光碎石术治疗输尿管结石677例的临床资料。B超测量结石长径7—53mm,平均13．2mm。并发尿路感染39例,行积极抗感染后再手术,急性肾功能衰竭38例行急诊手术,其余患者常规术前准备后手术。结果一次碎石成功率92．9％（629／677）,其中上、中、下段结石一次碎石成功率分别为79．2％（80／101）、89．3％（183／205）、98．7％（366／371）,上段〈中段〈下段（X2=5．670,P=0．017,X2=26．025,P=0．000）。手术时间10～90min,（33．4±14．6）min。术后住院时间1～21d,中位数5d。27例中转开放手术。19例一次碎石失败留置双J管加行ESWL治愈。术中并发症包括输尿管穿孔36例,输尿管撕脱伤1例。569例获随访3～6个月,平均4．8月,无输尿管狭窄等并发症。结论输尿管镜钬激光碎石术治疗输尿管结石安全、高效,尤其适用于ESWL失败或结石被包裹和中下段输尿管结石的患者。熟练掌握输尿管镜钬激光操作技巧可以减少并发症。     

输尿管镜钬激光碎石术治疗输尿管结石的技巧探讨（附82例报告）

目的：探讨输尿管镜钬激光碎石术治疗输尿管结石的手术技巧。方法：回顾性分析2009年应用输尿管镜钬激光碎石术治疗输尿管结石82例患者的临床资料,并结合文献复习。结果：一次碎石成功率89．2％（83／93）,其中上段、中下段结石一次碎石成功率分别为86．5％（45／52）和92．7％（38／41）,差异无统计学意义（P〉O．05）。结石被包裹57侧,一次碎石成功率为91．2％（52／57）,未被包裹33侧（3例进镜失败除外）,一次碎石成功率为93．9％（31／33）,差异无统计学意义（P〉O．05）。有ESWL史者43例47侧,一次碎石成功率为87．2％（41／47）,无ESWL史者$9例46侧,一次碎石成功率为91．3％（42／46）,差异无统计学意义（P〉O．05）。手术失败共10例lO侧,包括结石上移入肾盏7例,进镜失败3例。手术时间104100rain,平均（38．4±20．9）min;术后住院时间1～20天,平均（4．9±3．O）天。术后泌尿系感染、发热13例,一侧输尿管穿孔1例,无输尿管撕裂、远期输尿管狭窄等并发症。结论：输尿管镜钬激光碎石术是一种治疗输尿管结石安全、高效的方法,尤其适用于ES-WL失败或结石被包裹的患者。持续硬膜外麻醉联合蛛网膜下腔麻醉或全身麻醉有利于输尿管镜成功进镜。采用头高脚低位、缓慢注水、小功率碎石、“蚕食”等方法可以有效防止结石移位。处理合并息肉或被包裹的结石应先处理息肉或包裹组织,暴露结石后再处理结石;对于息肉或包裹组织不必一味追求剔除干净,而残余结石则需仔细清除。正确、熟练掌握输尿管镜钬激光操作技巧可以减少并发症。     

输尿管镜钬激光碎石术治疗输尿管结石(附104例报告)

目的探讨输尿管镜钬激光碎石术治疗输尿管结石的疗效。方法 2010年6月~2013年12月对104例输尿管结石(输尿管上段结石22例,中、下段结石82例)行输尿管镜下钬激光碎石,钬激光能量1.0~1.5 J,脉冲频率10~15Hz,采用蚕食法,从结石周边向中央行碎石治疗,将结石粉碎成直径3 mm颗粒。结果 97例一次碎石成功,成功率93.3%(97/104),其中上段结石碎石成功率77.3%(17/22),中、下段结石为97.6%(80/82)。3例结石冲回肾盂,改体外冲击波碎石治疗;4例因输尿管严重扭曲置镜失败,改开放手术。手术时间12~105 min,(44.5±21.7)min。术后住院时间3~7 d,(4.5±1.5)d。4例输尿管小穿孔,置双J管1个月后痊愈,无一例出现输尿管撕裂等较为严重的并发症;12例发生泌尿系感染与发热。97例随访1~12个月,平均4个月,术后1个月内结石全部排净。结论输尿管镜钬激光碎石术治疗输尿管结石安全,疗效可靠。     

输尿管镜钬激光碎石治疗嵌顿输尿管结石临床分析

目的：探讨输尿管镜钬激光碎石治疗嵌顿输尿管结石的有效性和安全性。方法：分析2005年10月～2008年5月输尿管镜下钬激光碎石治疗嵌顿输尿管结石268例患者临床资料，对碎石率、排石率和并发症等进行统计分析。结果：共行272例次输尿管镜钬激光碎石，一次碎石成功率为92．6％（252／272），输尿管上段与中、下段结石一次碎石成功率分别为84．6％（66／78）、95．9％（186／194）；平均手术时间35min。平均碎石时间16min；结石移位改行ESWL8例，结石位置较高改行微创经皮肾镜取石9例，改开放手术取石3例；碎石过程中黏膜撕裂4例、黏膜下假道形成6例，输尿管穿孔4例；18例术后发热（体温〉38．5℃，持续2天以上），5例出现体温〉39℃，其中1例发生感染性休克前兆；术后住院2～6天；2周～1个月拔除双J管，复查B超、KUB、IVP，结石排净率97．1％（264／272），肾盂积水由（2．6&#177;0．6）cm降至（1．4&#177;0．4）cm（P〈0．01）；随访3～24个月，3例发现输尿管狭窄。结论：输尿管镜钬激光碎石治疗嵌顿输尿管结石安全、有效，尤其适用于中、下段嵌顿输尿管结石。     

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.     

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.     

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.