腹腔镜肝切除治疗肝内胆管结石的临床研究

目的探讨腹腔镜肝切除治疗肝内胆管结石的可行性。方法8例肝内胆管结石患者均在腹腔镜下行胆囊切除胆总管切开胆道镜取石、T管引流,其中7例同时行腹腔镜左肝外叶切除,1例行左半肝切除。结果8例手术均获成功,手术时间(285.00±37.42)min;术中出血(306.25±29.73)mL,手术后无并发症,住院时间(7.88±1.36)d;残石率0。结论腹腔镜肝叶切除治疗肝胆管结石疗效好、安全,联合胆道镜取石疗效更佳。     

腹腔镜左半肝切除术治疗肝胆管结石的应用研究

目的:探讨完全腹腔镜左半肝切除术治疗左肝胆管结石病的临床应用价值。方法:回顾分析2013年6月至2015年9月为33例左肝胆管结石患者行腹腔镜左半肝切除术的临床资料。在腹腔镜下行左半肝切除、胆道检查并放置T管。术后6周行超声、CT、胆道镜检查或T管造影了解有无结石残留等并发症。患者均得到随访。结果:31例患者顺利完成腹腔镜手术,2例中转开腹,术中生命体征平稳,手术时间平均(177±56)min,术中出血量平均(317±57)ml,术后胃肠功能恢复时间24~48 h,平均(29.0±15.3)h,术后48~72 h拔除腹腔引流管。术后1例发生胆漏,经引流后痊愈;1例出现切口感染,经加强换药、调整血糖后痊愈,1例患者出现膈下积液,行穿刺引流治愈。平均住院(8.7±1.7)d。术后随访1~24个月,均恢复良好,无胆道狭窄、结石复发等并发症发生。结论:由经验丰富的腹腔镜医师开展腹腔镜左半肝切除术治疗左肝胆管结石是安全、可行的,值得临床推广应用。     

腹腔镜解剖性肝切除术的临床体会

目的:探讨完全腹腔镜解剖性肝切除术的应用价值。方法:回顾分析为38例肝疾病患者施行腹腔镜下解剖性肝切除术的临床资料。结果:38例手术均获成功,其中左肝内胆管结石21例,肝癌15例,肝血管瘤1例,肝局灶性结节性增生1例。20例单纯行腹腔镜肝切除术(laparoscopic hepatectomy,LH),6例联合行腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC),9例联合行胆总管切开探查术(laparoscopic common bile duct exploration,LCBDE),3例联合行LC+LCBDE。解剖性肝切除术包括左外叶切除(Ⅱ+Ⅲ段)23例,左内叶切除(Ⅳ段)2例(左外叶已切除),左半肝切除(Ⅱ+Ⅲ+Ⅳ段)9例,Ⅴ段切除3例,Ⅵ段切除1例。单纯解剖性肝切除术手术时间平均(170±20)min,联合LC时平均(190±27)min,联合LCBDE平均(220±45)min,联合LC+LCBDE平均(240±23)min。术中出血量平均(350±86)ml。术后无胆漏、出血等并发症发生。术后1～3 d肛门排气,5～11 d痊愈出院。随访36例6～24个月,除1例于术后1年因肿瘤复发转移死亡外,余者健在,无复发、转移,结石患者无再发。结论:腹腔镜解剖性肝切除术较好地解决了腹腔镜下肝段以上肝切除术的出血、气栓等问题,可安全用于肝段及半肝切除术,可在很大程度上取代开腹手术。     

腹腔镜左肝叶切除治疗肝胆管结石

目的: 总结腹腔镜左肝叶切除治疗肝胆管结石的经验.方法: 2004年10月至2005年1月施行腹腔镜左肝叶切除治疗肝胆管结石7例.肝切除过程包括离断肝周韧带和粘连,解剖阻断左肝蒂,缝扎肝左静脉,离断肝实质.结果: 左半肝切除2例,左肝外叶切除5例,手术时间平均238 min,平均出血量150 ml.术后轻微胆漏3例.手术6~14 d后出院.结论: 腹腔镜左肝叶切除治疗肝胆管结石是可行的.     

腹腔镜左半肝切除术治疗肝胆管结石病的临床疗效

目的 探讨腹腔镜左半肝切除术治疗肝胆管结石的临床疗效.方法 回顾性分析2013年6月至2014年6月南昌大学第二附属医院收治的30例行腹腔镜左半肝切除术治疗左肝胆管结石患者的临床资料.在腹腔镜下先行鞘内或鞘外半肝血流阻断后再切除左半肝,合并胆总管结石或右肝管结石一同处理,根据胆管情况选择放置T管或腹腔镜下行一期胆总管缝合.术后1个月均返院复查彩色多普勒超声、CT或者T管造影检查,此后每3个月复查彩色多普勒超声,必要时增加CT或MRI检查,了解有无结石残留等并发症.随访时间截至2014年7月.结果 5例患者中转开腹,25例患者顺利完成腹腔镜手术,全部采用阻断左半肝入肝血流后行肝切除术,其中鞘外阻断11例,鞘内阻断14例.手术时间为(158±85) min,术中出血量为(405±215) mL,术中输血2例.8例胆总管结石患者术中胆道镜探查未发现结石残留,其中5例行胆道一期缝合,3例放置T管.全组患者无手术死亡,术后2例发生胆汁漏,1例出现胸腔积液,经引流后痊愈;术后1例患者出现膈下积液,B超定位下行穿刺引流;术后1例患者出血,出血量约500 mL,经保守治疗痊愈.全组患者住院时间为(8.5 ±2.3)d.患者术后随访时间为1 ～12个月,无胆汁漏及腹腔感染等并发症,均无结石复发.结论 腹腔镜左半肝切除术治疗肝胆管结石安全、可行,疗效良好.     

腹腔镜左肝叶切除治疗肝胆管结石

目的 探讨胆道镜联合腹腔镜左肝叶切除治疗肝胆管结石的可行性及临床疗效.方法 选择肝胆管结石患者49例,全麻下行腹腔镜左肝外叶切除、左肝内叶切除、左半肝切除,联合胆道镜胆管探查取石.结果 29例患者在完全腹腔镜下行解剖性左肝外叶切除(ⅡⅢ段),2例行左肝内叶切除(Ⅳ段),18例行左半肝切除(ⅡⅢⅣ段).所有患者均联合胆道镜胆管探查和取石,11例联合腹腔镜胆囊切除(LC).平均手术时间为226 min,联合LC者平均手术时间为243 min.术中平均出血378 ml.术后未发生胆漏和出血等并发症.术后1～3 d肛门排气,胃肠功能恢复、进食,7～12d 痊愈出院.患者术后复查MRI、MRCP未发现结石残留.随访47例,平均16个月,患者恢复良好,未发现结石再发.结论 胆道镜联合腹腔镜左肝切除治疗肝胆管结石具有创伤小、恢复快、治疗彻底、临床疗效好等优点,是一种安全、有效、微创、可行的新手术方式.     

腹腔镜肝切除术治疗左肝内胆管结石的临床应用

目的 探讨腹腔镜肝切除术治疗左肝内胆管结石的技术与疗效。 方法 回顾性分析2011年1月至2016年12月完成67例腹腔镜肝切除术治疗左肝内胆管结石临床及随访资料。 结果 全部67例患者合并左半肝或左外叶肝萎缩,腔镜手术方式包括左外叶肝切除48例、左半肝切除19例。其他腹腔镜下联合术式包括：胆囊切除术52例、胆总管探查术43例、T管引流术39例,胆总管一期修补术4例。手术切口长度（4.67±1.26）cm。术后发生胆漏3例,均经引流观察后自愈;1例因术后腹腔大出血合并胆瘘再手术治愈;肝脓肿1例,膈下脓肿1例,均经穿刺引流治愈。 结论 腹腔镜肝切除术治疗左肝内胆管结石安全可靠,术中应尽量取净其他胆道残余结石并连续紧密缝合左肝管残端。如结石已被取净胆总管的探查和T管引流并非必需。     

腹腔镜下鞘外解剖性肝切除结合ICG荧光反染在肝胆管结石治疗中的应用（附视频）

背景与目的 肝胆管结石是常见的消化系统疾病之一,容易导致肝硬化、胆道感染、积脓,甚至引起胆管癌。肝切除是彻底治疗肝胆管结石的主要手段,近年来随着技术的进步,腹腔镜手术因在近期手术效果方面的优越性,逐步取代了开腹手术。但是,相比于肝胆管肿瘤而言,肝胆管结石造成的炎症水肿和粘连使手术更加困难,因此寻找简便可靠的手术方法是有必要的。近来随着对肝脏解剖的再认识,腹腔镜下鞘外解剖性肝切除在肝脏肿瘤中得到广泛应用,且有报道证实结合吲哚菁绿（ICG）荧光反染技术可使手术更加高效和精准,但是在肝胆管结石中的应用鲜有报道。在本文中,笔者总结和归纳近期实施腹腔镜下鞘外解剖性肝切除结合ICG荧光反染在肝胆管结石治疗中的应用体会。方法 回顾性分析中南大学湘雅医院胆道外科2022年2月—2023年4月收治的7例肝胆管结石患者的临床资料,根据患者病史、临床体征和术前影像学资料,患者均有肝切除的指征,其中6例行左半肝切除,1例行右肝后叶切除术。术中应用荧光腹腔镜,在低中心静脉压和全肝入肝血流阻断下,充分利用肝脏表面的解剖标志（Arantius板、脐板、胆囊板、尾状突的Glisson蒂）和Laennec膜解剖出目的肝蒂,将其阻断后再向外周静脉注射ICG,使肝脏表面显示出缺血/切除标记线,术中再结合肝静脉的显露,使解剖性肝切除的实施得以完成。部分患者需要行胆道切开及术中胆道镜取石,提高结石清除率。结果 7例患者均顺利完成肝切除手术,术后解剖标本,检查确认切除肝脏的肝胆管结石情况。5例患者切除肝脏后行胆总管切开取石及术中胆道镜探查。术中出血量100~600 mL,平均（314.3±211.6）mL,无严重并发症（Clavien-Dindo分级Ⅲ~Ⅳ级）发生,除1例患者因术后胆汁漏、伤口感染住院24 d外,其余患者术后住院时间7~9 d,平均（8.5±0.8）d。术后通过腹部B超和T管造影或者MRCP检查,6例患者的结石清除干净,1例患者行1次术后胆道镜后将结石清除干净。病检回报均示肝胆管结石及胆管炎,未见癌变。结论 腹腔镜下鞘外解剖性肝切除结合ICG荧光反染技术在肝胆管结石患者中的应用是安全和可行的。其有效性和优越性还有待扩大样本量、丰富临床数据的对照研究来进一步验证。     

完全腹腔镜规则性肝切除的解剖基础与技术问题

目的探讨腹腔镜规则性肝切除的解剖基础与技术问题。方法 2 0 0 2年 7月至2 0 0 2年 11月 ,治疗原发病灶位于左半肝但未侵及左肝门的原发性肝癌 4例、肝血管瘤 2例、肝囊肿伴感染 1例。肝切除步骤包括显露第 1肝门 ,游离肝周韧带 ,解剖并离断 2、3级肝门 3管 ,解剖第 2肝门并夹闭肝左静脉 ,离断肝实质和切断肝左静脉。结果 7例完全在腹腔镜下完成手术 ,左半肝切除 2例、左外叶切除 4例、肝方叶切除 1例。均成功地在矢状部对 2至 3级肝门的 3管进行解剖和离断。手术时间为 15 0～ 32 0min ,平均 (2 5 3± 5 9)min。出血量 2 0 0～ 10 0 0ml,平均 (4 5 0± 2 6 1)ml。结论腹腔镜规则性左肝切除术是安全可行的 ,对 2级肝门 3管的解剖和离断是行肝段或左半肝切除时控制出血的关键。     

腹腔镜肝切除治疗肝血管瘤18例

目的探讨腹腔镜肝切除治疗肝血管瘤的可行性。方法2002年1月至2006年10月共治疗18例肝血管瘤患者,应用腹腔镜下肝门阻断器阻断第一肝门的血流后,使用电刀、超声刀等方法断肝,肝断面采用腹腔镜下肝针缝合并喷洒生物蛋白胶等方法处理,行腹腔镜肝段或局部切除10例、行左肝外叶切除术5例、行规则性左半肝切除术2例、行不规则性左半肝切除术1例;其中合并胆囊切除2例、合并阑尾切除1例。结果18例患者手术均获得成功,手术时间（185．4±55．7）min;术中出血（416．2±128．8）ml;术后恢复顺利,无严重并发症,患者住院时间（6．2±1．0）d。结论腹腔镜肝切除治疗肝血管瘤安全、可行。     

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.