单中心51例单孔腹腔镜肝切除经验总结

目的:探讨单孔腹腔镜肝切除术的疗效及安全性,总结其手术经验。方法:回顾分析2009年12月至2015年8月完成的51例单孔腹腔镜肝切除术的临床资料,并对比良恶性疾病接受单孔腹腔镜肝切除术的疗效。全组共51例患者(男18例,女33例),良性疾病38例,恶性疾病13例,平均(43.51±11.83)岁。结果:51例单孔腹腔镜肝切除术均成功完成,无加孔或中转开腹。手术时间平均(112.65±53.23)min,其中良性疾病平均(97.11±25.33)min,恶性肿瘤平均(158.08±82.63)min;术中失血量平均(165.88±135.29)ml,其中良性疾病平均(141.05±96.92)ml,恶性肿瘤平均(238.46±199.12)ml;术后排气时间平均(1.76±0.62)d,其中良性疾病平均(1.66±0.58)d,恶性肿瘤平均(2.69±0.86)d;术后平均住院(5.18±2.21)d,其中良性疾病平均(4.42±1.48)d,恶性肿瘤平均(7.38±2.53)d。除2例患者术后发生出血外,无胆漏、胸腔积液等并发症发生。结论:传统腹腔镜器械完成单孔腹腔镜肝左叶病变切除具有良好的疗效及美容效果。病灶局限肝左外叶的良性病例是单孔腹腔镜肝切除术的良好适应证。     

后腹腔镜治疗肾上腺肿瘤的优势和手术技巧

目的探讨后腹腔镜肾上腺肿瘤切除术的优势和手术技巧。方法分别行后腹腔镜（33例）和传统开放手术（10例）治疗肾上腺肿瘤,患者平均年龄37．6岁,平均瘤体大小1．2～6．4cm。结果33例后腹腔镜手术均获成功,手术时间50～130min,平均（80．5±21．3）min;术中失血50～150ml,平均（65．2±11．6）ml;术后引流管留置1～2d,平均住院5d。随访6个月～3年无并发症发生。与开放手术相比有明显的优势。结论后腹腔镜肾上腺肿瘤切除术安全,疗效好,疼痛轻,患者术后恢复快。     

经肾上腺腹侧间隙行后腹腔镜肾上腺肿瘤切除术的临床体会(附30例报告)

目的:探讨经肾上腺腹侧间隙行后腹腔镜肾上腺肿瘤切除术的临床优势。方法:30例患者经肾上腺腹侧间隙行后腹腔镜肾上腺肿瘤切除术(改良组),20例患者行传统解剖性后腹腔镜肾上腺肿瘤切除术(传统组),术前均诊断明确,患者平均(46.5±3.8)岁,瘤体直径平均(3.2±0.6)cm。比较两组患者手术时间、术中失血量、术后引流管放置时间、住院时间等指标。结果:30例后腹腔镜改良术式均获成功,手术时间30~70 min,平均(40.5±18.25)min;术中失血10~30 ml,平均(15.6±6.6)ml;术后引流管留置1~2 d,平均(1.9±0.2)d,平均住院(4.7±0.6)d;均优于传统组,差异有统计学意义(P0.05)。结论:经肾上腺腹侧间隙行后腹腔镜肾上腺肿瘤切除术创伤更小,出血更少,手术时间、住院时间缩短,术后患者康复快,值得推广。     

手助腹腔镜脾切除与开腹脾切除治疗巨脾效果比较

比较手助腹腔镜脾切除与开腹脾切除治疗巨脾的效果。回顾性分析41例因巨脾行脾脏切除术的临床资料。手助腹腔镜脾切除术患者23例,开腹脾切除术患者18例。比较两组患者手术时间、术中出血量、术后平均住院时间、术后并发症发生率。结果显示,与开腹脾切除术相比,手助腹腔镜脾切除的手术时间长[(313+41.8)min vs(209+19.9)min,P=0.01]、术中出血量少[(324±54.8)ml vs(539±154.8)mL,P=0.01]、术后并发症少(P=0.004)、术后平均住院时间短[(6±1.2)d vs(9±1.4)d,P=0.01]。结果表明,与开腹脾切除术相比,手助腹腔镜脾切除的手术出血量少,术后并发症发生率低,术后住院时间更短,但手术时间长。     

后腹腔镜结核性无功能肾切除术23例报告

目的:探讨后腹腔镜结核性无功能肾切除术的临床应用价值。方法:回顾分析2012年7月至2016年3月为23例结核性无功能肾患者行后腹腔镜肾切除术的临床资料,其中男9例,女14例,平均(39±3)岁;患者均为无功能肾,右侧11例,左侧12例。经过2周抗结核治疗后患者均行后腹腔镜肾切除术。结果:23例患者均成功完成肾切除术,无一例中转开放手术。手术时间73～196 min,平均(125±12)min;术中失血量79～420 ml,平均(198±17)ml;术后住院5～10 d,平均(7.5±0.7)d。术中均未发生脓肾破裂、腹膜损伤,其中1例术后发生输尿管残端积脓感染,二期行输尿管切除术。随访1～36个月,平均(17.0±1.3)个月,肾功能正常。结论:后腹腔镜结核性无功能肾切除术具有良好的安全性、可行性,值得在具备条件的医院推广应用。但因腹膜外空间较小,且结核肾周围粘连较重,对术者技术水平要求较高,需熟练掌握解剖,严格把握手术适应证,术中仔细辨认组织层次。     

单孔和传统腹腔镜肾切除术的比较

目的对比分析单孔腹腔镜和传统三孔腹腔镜肾切除术的临床资料,以探讨单孔腹腔镜在泌尿外科运用的安全性和有效性。方法通过回顾性分析15例单孔腹腔镜肾切除术和20例传统腹腔镜肾切除术患者的手术时间、术中失血量、术后肠通气恢复时间、术后留置引流管时间、术后住院天数等临床数据。结果两组患者在年龄[(53±13)岁vs(51±11)岁,P=0.773],体质量指数[(22.1±2.6)kg/m~2 vs(22.7±3.3)kg/m~2,P=0.535],性别、病理类型、手术路径、术中失血量[(142±74)ml vs(138±60)ml,P=0.861)],术后肠通气恢复天数[(2.0±0.7)d vs(2.0±0.6)d,P=1.000],术后留置引流管天数[(3.5±0.9)d vs(3.2±1.1)d,P=0.453],术后住院天数[(7.1±2.2)d vs(6.8±1.6)d,P=0.729]等方面无明显区别。单孔组14例患者成功的完成了单孔腹腔镜手术,没有增加额外的Trocar,1例中转为三孔腹腔镜后,完成了手术。但单孔腹腔镜手术时间比传统腹腔镜更长[(231±52)min vs(157±30)min,P0.01],无切口感染病例,短期随访没有切口疝,疤痕也较小。结论单孔腹腔镜肾切术,无论经腰和经腹途径都是安全和有效的。能满足患者对切口美观的要求。但学习曲线及手术时间较长,随着手术技巧的提高和手术器械的改进,或许能有效的解决这个问题。     

腹腔镜下横结肠癌全结肠系膜切除术的临床应用

目的:探讨腹腔镜下横结肠癌全结肠系膜切除术的临床处理技巧,以提高手术安全性及短期疗效。方法:回顾分析2009年6月至2013年12月行腹腔镜横结肠癌全结肠系膜切除术的31例患者的临床资料。结果:2例患者中转开腹,29例在腹腔镜下完成手术。手术时间85~290 min,平均(140.0±28.6)min;术中出血量25~550 ml,平均(80.0±33.0)ml;术后排气时间2~7 d,平均(2.5±1.3)d;引流量55~450 ml,平均(83.0±24.6)ml;术后开始进食时间2~6 d,平均(2.5±1.2)d;淋巴结清扫数量9~33枚,平均(14.6±3.5)枚;术后住院7~21 d,平均(9.0±3.6)d。术后并发肠梗阻、肺部感染、切口感染各1例,均经保守治疗后治愈,无吻合口漏发生。结论:腹腔镜下横结肠癌全结肠系膜切除术中精细操作注意层面,熟悉常见解剖及变异,具有一定的腹腔镜操作技巧,是安全、有效的,在发挥微创手术优势的同时不增加手术相关风险。     

腹膜后腹腔镜肾上腺部分切除术与全切除术治疗醛固酮瘤的对比研究

目的 比较腹膜后腹腔镜肾上腺部分切除术与全切除术治疗肾上腺醛固酮瘤的治疗效果.方法 回顾性分析我院94 例醛固酮瘤临床资料.34 例行后腹腔镜下肾上腺全切除术,60 例行后腹腔镜下肾上腺部分切除术.术后随访6~60 个月,平均24.5 个月.结果 行肾上腺全切组手术时间(40.0±12.0)min,术中失血量(23.5±9.5)ml,拔引流管时间(2.5±1.2)d,肿瘤大小(20.0±5.0)mm,术后住院天数(6.5±2.0)d.行肾上腺部分切除组手术时间(48.0±13.0)min,术中失血量(25.5±10.0)ml,拔引流管时间(2.8±1.4)d;肿瘤大小(18.5±4.5)mm;术后住院天数(7.0±2.5)d.肾上腺全切除组和部分切除组的肿瘤大小、术中失血量、住院时间和拔引流管时间差异无统计学意义(P>0.05).全切除组手术时间短于部分切除组(P<0.05).全切组术和部分切除组术后有效率分别为100%(34/34)和96.7%(58/60),两组间差异无统计学意义(P>0.05).结论 单发肾上腺醛固酮瘤适合于肾上腺部分切除术,肿瘤多灶性是保留肾上腺组织手术治疗无效的主要原因.对于部分切除术治疗无效患者,再次行患侧肾上腺全切除或肿瘤切除均可获得良好疗效.     

保留脾血管的腹腔镜胰体尾切除术

目的:探讨保留脾脏血管腹腔镜胰体尾切除术的可行性与安全性。方法:回顾分析2011年3月至2014年7月为38例患者行保留脾血管腹腔镜胰体尾部肿瘤手术的临床资料。结果:手术时间116~295 min,平均(170.5±50.2)min;术中失血量15~565 ml,平均(112.3±33.6)ml;均未输血。病理检查结果示胰腺导管腺癌11例,浆液性囊腺瘤6例,黏液性囊腺瘤9例,黏液性囊腺瘤局部癌变2例,胰岛素瘤4例,实性假乳头状肿瘤6例。术后3例发生胰漏,经保守治疗好转。余者术后均恢复顺利,无并发症发生,术后平均住院(7.36±2.13)d。结论:腹腔镜保留脾脏血管胰体尾切除术是有效治疗远端胰腺肿瘤的新术式,具有微创优势,安全、可行。     

完全腹腔镜脾切除42例临床经验总结

目的 探讨完全腹腔镜脾切除(laparoscopic splencetomy,LS)的手术技巧和临床经验.方法 回顾性分析杨州大学临床医学院2006年10月至2008年5月对42例施行完全腹腔镜脾切除术病人手术时间、术中失血量、术后并发症等.其中,血液病脾12例,脾结核1例,脾囊肿1例,外伤性脾破裂4例,恶性淋巴瘤1例,门脉高压性脾功能亢进症23例.脾脏装入塑料袋剪碎取出.结果 42例手术均获成功,平均出血量(300±110.60)ml,手术时间60～260 min(170±45.65)min,术后住院时间平均(8.10±3.52)d,无严重术后并发症.结论 对于大多数脾脏疾病,腹腔镜脾切除术安全可行,关键在于脾蒂的正确处理.根据脾脏的病种、大小形态、脾门等情况,选用比较适宜的脾蒂处理方案.     

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.