膝骨关节炎临床症状与X线表现相关性研究

目的:探讨膝骨关节炎临床症状与X线片表现的相关性,为临床诊疗提供依据.方法:收集门诊78例(108膝)膝骨关节炎患者,年龄41～77岁;女65例(89膝),男13例(19膝).对所有病例进行严重性指数(Lequesne膝关节指数)问卷调查,计算严重性指数,并将病例分成轻度组(Lequesne指数≤8)和重度组(Lequesne指数>8).摄负重站立位膝关节正侧位、髌股关节Skyline位X线片,分部位观察评价关节间隙狭窄、骨赘生成、软骨下骨硬化、软骨下囊变,测量下肢力线角及外侧髌股角.对膝骨关节炎严重性与各X线表现进行相关性及回归分析.结果:膝骨关节炎轻度组和重度组在外侧胫股关节间隙、内侧髌股关节间隙狭窄程度、内侧胫骨骨赘、内侧股骨骨赘、外侧胫骨骨赘、外侧股骨骨赘、内侧滑车骨赘、外侧髌骨骨赘、外侧滑车骨赘、胫骨髁问骨赘程度等方面的差异有统计学意义(P<0.05).Logistic回归分析结果显示外侧股骨骨赘的相伴概率(0.009)最小,Wald值最大(6.779),提示外侧股骨骨赞为判断膝骨关节炎严重性最重要的放射学表现.结论:评价膝骨关节炎严重性时,关节间隙狭窄与骨赘生成是最有意义的X线表现,其中外侧胫股关节间隙狭窄、内侧髌股关节间隙狭窄、内侧胫骨骨赘、内侧股骨骨赘、外侧胫骨骨赘、外侧股骨骨赘、内侧滑车骨赘、外侧髌骨骨赘、外侧滑车骨赘、胫骨髁问骨赘更加应该予以重视.     

膝骨关节炎从痹论治的病因与证候探讨

针对膝骨关节炎从痹论治的观点,通过分析膝骨关节炎的常见临床表现,应用中医辨证规律,对其病因病机和临床证候提出不同的看法。认为膝骨关节炎的中医病因病机是先天禀赋不足,或劳作虚损,或脏腑、气血功能失调及外邪侵入、外伤久积所致。将膝骨关节炎分为肝肾亏虚、筋脉痹阻证,肝肾两虚、湿注骨节证,肝肾亏虚、痰瘀互阻证,肝肾亏损、气血两虚证4个中医证型。提出以滋补肝肾为主,配合祛风、散寒、除湿、清热、化痰、活血等治法。     

膝骨性关节炎的中医辨证分型与膝关节镜下病理改变对比性研究

目的对比性地研究膝骨性关节炎中西医诊断相关性.方法对60例膝骨性关节炎患者进行中医辨证,分三型:Ⅰ型,肝肾不足,筋脉瘀滞型(21例);Ⅱ型,脾肾两虚,湿注骨节型(18例);Ⅲ型,肝肾亏虚,痰瘀交阻型(21例).然后进行关节镜下病理改变观察,同时进行组织学病理改变观察.结果 60例病人均有不同程度的关节软骨面退行磨损或剥脱.18例Ⅱ型的滑膜增生或炎性变与Ⅰ、Ⅲ型比较差异有显著性意义,P＜0.01.21例Ⅲ型的骨赘增生与Ⅰ、Ⅱ型比较差异有显著性意义,P＜0.01.结论脾肾两虚、湿注骨节型与镜下滑膜增生及炎性变有较密切临床诊断意义;肝肾亏虚、痰瘀交阻型与镜下骨赘增生有较密切临床诊断价值.     

膝骨关节炎影像学分级同胫股及髌股关节轴线角相关性分析

目的:探讨膝骨关节炎影像学分级与胫股及髌股关节轴线角的相关性。方法:回顾性分析2018年9月至2020年12月行立位双下肢X线及膝关节侧位片检查的中老年KOA患者739例(1 026膝)。其中K-L0级患者63例(95膝);K-L 1级100例患者(130膝);K-L 2级161例患者(226膝);K-L 3级187例患者(256膝);K-L 4级228例患者(319膝)。依据膝关节中心和髋关节中心与踝关节中心连线的相对位置将患膝分为内翻组844膝及外翻组182膝。根据Install-Salvati法将患膝重新分为高位髌骨(髌骨高度>1.2 mm)347膝、中位髌骨(髌骨高度0.8～1.2 mm)561例、低位髌骨(髌骨高度<0.8 mm)118膝3组。测量并比较各组股骨下角,胫骨上角,股骨颈干角,股骨胫骨角,关节间隙角,髋-膝-踝角,髌骨股骨角及髌骨高度。结果:(1)在内翻型KOA组中,不同K-L分级患者的髋-膝-踝角、胫股角、股骨下角、胫骨上角、关节间隙角、股骨颈干角比较,差异有统计学意义(P<0.05)。髋-膝-踝角、胫股角、股骨下角、胫骨上角、关节间隙角与K-...     

膝骨关节炎骨赘放射学大小与负重位下肢力线相关性分析

[目的]探讨膝OA患者膝关节放射学骨赘大小与负重位下肢力线的关系。[方法]对40例接受人工全膝关节置换术的原发性骨关节炎患者(共40膝),利用躯体X线测量系统进行负重位下肢力线的测量。将膝关节正位X线片导入计算机,应用Photoshop软件长度测量工具分别测量股骨远端、胫骨平台宽度和骨赘长度。骨赘长度与骨端宽度的比值,称为骨赘突起指数。应用SPSS软件通过Pearson相关检验,评价测量者内及测量者间骨赘突起指数重复性,探索膝OA患者膝关节放射学骨赘大小和负重位下肢力线之间的关系。[结果]40例膝OA患者负重位下肢力线平均为:12.53°±5.62°。测量者内及测量者间骨赘突起指数有较好相关性,r接近1(P<0.001)。负重位下肢力线与股骨内侧髁骨赘突起指数呈正相关(r=0.530,P<0.001),与胫骨平台内侧骨赘突起指数呈正相关(r=0.618,P<0.001)。负重位下肢力线与股骨外侧髁(r=-0.008,P=0.961)、胫骨平台外侧(r=0.244,P=0.129)骨赘突起指数间无相关性存在。[结论]膝OA患者股骨内侧髁骨赘突起指数、胫骨平台内侧骨赘突起指数与负重位下肢力线呈正相关,机械应力通过...     

贵阳市症状性膝骨关节炎疼痛与关节间隙狭窄影像学表现的相关性研究

目的探讨贵阳市症状性膝骨关节炎患者疼痛与关节间隙狭窄影像学表现的相关性。方法收集贵阳市七家大型医院自2014年1月至2015年12月就诊的症状性膝骨关节炎(knee osteoarthritis,KOA)患者。纳入标准为符合美国风湿病学会修订的KOA诊断标准,且X线片示KellgrenLawrence分级Ⅱ级及以上者。共993例患者纳入研究,其中男304例,女689例,采用流行病学问卷调查,并行X线片膝关节正侧位投照,记录患者疼痛部位、疼痛程度,分析骨赘生成部位、骨关节间隙变窄情况。数据采用SPSS 19.0软件进行统计学分析。结果 993例KOA患者,膝关节压痛出现在髌骨周围631例、内侧关节间隙469例、外侧关节间隙132例,109例患者无明显压痛部位,286例患者存在多部位压痛。轻度疼痛290例,中度疼痛427例,重度疼痛276例。KellgrenLawrence分级发现Ⅱ级334例,Ⅲ级407例,Ⅳ级252例。骨赘生长部位于髁间嵴531例,胫骨关节面边缘463例,髌骨周围412例,股骨关节面56例,多部位骨赘生长672例。疼痛程度与关节间隙狭窄关系经统计学分析发现(χ~2=7.381,P0.05)差异无统计学意义。结论症状性膝骨关节炎疼痛与关节间隙狭窄无明显相关性。     

糖尿病足中终末糖基化产物表达与中医辨证分型及部位的相关性

目的:研究糖尿病足截肢标本上动脉内终末糖基化产物(AGEs)的表达与糖尿病足中医辨证分型的相关性.方法:100例患者分为气血两虚瘀阻证、气阴两虚瘀阻证、脉络热毒证,对三型进行动脉AGEs的免疫组化研究.结果:在动脉中脉络热毒证表达最弱,气血两虚瘀阻证表达最强.各证型之间AGEs表达具有显著性差异(P<0.01).结论:糖尿病足中医辨证分型与AGEs的表达具有较高的相关性.     

腰椎间盘性腰痛患者MRI影像与中医证型的相关性分析

目的：探讨腰椎间盘性腰痛中医证型与MRI表现的相关性。方法：根据中医辨证对70例腰椎间盘性腰痛患者进行分型并进行MRI扫描,回顾性分析各证型的MRI表现特点。结果：腰椎间盘性腰痛气滞血瘀型常表现为旁中央型突出,风寒湿滞型为中央型突出,湿热痰滞型常为外侧型突出,肝肾亏虚型常为椎间盘膨出。结论：腰椎间盘性腰痛的中医证型和MRI表现具有相关性。     

前交叉韧带退变与髁间窝撞击及内侧半月板撕裂的相关性研究

目的探讨膝骨关节炎(knee osteoarthritis,KOA)患者前交叉韧带(anterior cruciate ligament,ACL)退变与髁间窝撞击、内侧半月板撕裂间的相关性。方法回顾分析2014年7月-2016年2月收治伴ACL退变的KOA患者55例(55膝,退变组)临床资料,另随机选择55例(55膝)ACL正常的KOA患者作为对照(55膝,正常组)。两组患者性别、年龄、体质量指数、侧别比较,差异均无统计学意义(P0.05)。于术前MRI测量髁间窝指数,评价是否存在髁间窝狭窄;关节镜下观察内、外侧半月板撕裂发生情况以及发生部位,有无ACL胫骨止点骨赘形成;计算各部位半月板撕裂及骨赘形成发生率。结果两组内侧半月板前角、体部撕裂发生率,外侧半月板前角、体部、后角及后根部撕裂发生率比较,差异均无统计学意义(P0.05);内侧半月板后角及后根部撕裂发生率、ACL胫骨止点骨赘形成发生率、髁间窝狭窄发生率以及髁间窝指数比较,差异均有统计学意义(P0.05)。两组13例存在ACL胫骨止点骨赘患者中,内侧半月板后根部撕裂发生率为53.8%(7/13);97例无ACL胫骨止点骨赘患者中,其发生率为16.5%(16/97);比较差异有统计学意义(χ~2=9.671,P=0.002)。结论 KOA患者ACL退变与髁间窝撞击以及内侧半月板后角、后根部撕裂密切相关,ACL胫骨止点骨赘形成与内侧半月板后根部撕裂发生率相关。     

退行性膝关节髁间撞击征的分型与治疗

目的:探讨退行性膝关节髁间撞击征的概念及分型和各型的关节镜治疗原则和方法。方法:对30例退行性膝关节髁间撞击征病人症状、体征、放射检查及关节镜下表现及治疗方法进行总结分析。结果30例全部随访,时间平均1年,伸膝受限改善率平均80％。撞击感消失,疼痛明显减轻,优:10例,良:14例,可:4例,差:2例。结论:退行性膝关节髁间撞击征是由于股骨髁间窝继发性狭窄和(或)胫骨髁间嵴增生增高和(或)前交叉韧带胫骨起点前缘骨赘增生,造成膝关节伸直位时撞击而出现的相应临床表现。分为3型:A型:股骨髁间窝型,即股骨髁间窝骨赘增生。B型:胫骨髁间嵴型;B1型:胫骨髁间嵴增生增高型;B2:前交叉韧带胫骨起点前缘骨赘增生型;C型:混合型。关节镜下股骨髁间窝扩大成形术和(或)胫骨髁间嵴部分切除术,和(或)前交叉韧带胫骨起点前缘骨赘切除术,是治疗退行性膝关节髁间撞击征的有效微创方法。     

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.