快速康复外科理论在高龄患者腹腔镜胆囊切除术中的应用——前瞻性随机对照研究

目的探讨快速康复外科(fast track surgery,FTS)理论在高龄患者腹腔镜胆囊切除术(laparoscopiccholecystectomy,LC)中的应用价值。方法 2008年3月～2011年3月30例80岁以上择期3孔法LC,随机分为FTS组及对照组,FTS组接受FTS方案治疗,对照组接受传统方法治疗。比较2组术后肠道排气时间、住院时间、术后并发症和住院总费用等。结果 FTS组术后排气时间(22.9±5.5)h显著短于对照组(36.1±8.1)h(t=-5.280,P=0.000),FTS组术后住院时间(2.8±2.1)d显著短于对照组(5.6±2.0)d(t=-3.725,P=0.000),FTS组术后住院总费用(9.9±1.8)千元显著少于对照组(12.2±2.1)千元(t=-3.231,P=0.000);2组并发症发生率无统计学差异(P=0.586)。结论对80岁以上患者择期LC应用FTS能缩短患者的住院时间,加速康复。     

基于加速康复外科理念的无痛腹腔镜胆囊切除术的临床研究

目的探讨基于加速康复外科(fast track surgery,FTS)理念的围手术期多模式镇痛在腹腔镜胆囊切除术中的临床应用价值。方法回顾性搜集2013年7月至2015年7月期间在白银市第二人民医院普外科接受腹腔镜胆囊切除术的268例患者的临床资料,其中2014年8月31日之前的133例患者采用的传统围手术期镇痛方案(简称传统组),2014年9月1日之后的135例患者采用基于FTS理念的围手术期多模式镇痛(简称FTS组),比较2组患者的术后疼痛、肛门排气时间、排便时间、进食时间、下床活动时间、引流管留置时间、住院时间、72 h时的睡眠时间、并发症等情况。结果 1 FTS组患者术后1、4、8、12、24、48及72 h时的疼痛数字评估量表评分均明显低于传统组(P0.01)。2 FTS组术后肛门排气、排便时间、进饮食时间、下床活动时间、引流管留置时间及住院时间均明显短于传统组(P0.01),72 h时的睡眠时间明显长于传统组(P0.01)。3 FTS组的恶心呕吐发生率明显低于传统组(P0.01),其他不良反应如返酸、尿潴留及呼吸困难发生率在2组间比较差异无统计学意义(P0.05)。4 FTS组术后镇痛效果满意率明显高于传统组(P0.01)。结论在腹腔镜胆囊切除术围手术期采用基于FTS理念的多模式镇痛安全、有效,基本能够达到全程无痛的手术效果。     

早期宫颈癌腹腔镜辅助阴式全子宫切除术围手术期FTS理念护理效果观察

目的探讨早期宫颈癌腹腔镜辅助阴式全子宫切除术围术期快速康复外科(FTS)理念的护理效果。方法选取84例早期宫颈癌患者,随机分为2组,各42例。2组均行腹腔镜辅助阴式全子宫切除术。对照组围手术期施行常规护理,观察组在对照组基础上施行FTS理念护理。比较2组术后并发症、住院时间及费用。结果观察组下床活动时间、术后肛门首次排气时间、住院时间、住院费用及术后并发症总发生率均优于对照组,差异有统计学意义(P0.05)。结论围术期FTS理念护理能促进早期宫颈癌腹腔镜辅助阴式全子宫切除术患者的术后康复,减少住院费用和降低术后并发症发生率。     

胃癌术后罗哌卡因持续切口浸润麻醉对患者镇痛及早期康复的影响

目的评估罗哌卡因持续切口浸润麻醉对开腹胃癌根治术后的镇痛效果及对早期康复的影响。方法回顾性分析2011年6月至2014年10月期间榆林市第二医院普通外科开腹行胃癌根治术的50例患者的临床资料,根据镇痛方法不同分为罗哌卡因持续切口浸润麻醉组(简称"罗哌卡因组")和生理盐水对照组(简称"对照组"),每组均为25例。所有患者均使用静脉自控麻醉泵,比较不同时间点(术后4 h、8 h、16 h、24 h、48 h)视觉模拟评分法(VAS)评分、舒适度(BCS)评分、术后恶心呕吐评分,以及2组间累计静脉自控镇痛药物使用量、首次下床活动时间、肠功能恢复时间、住院时间、切口感染发生情况。结果罗哌卡因组在术后4 h、8 h、16 h、24 h、48 h时的VAS评分均明显低于对照组(P0.05)、BCS评分均明显高于对照组(P0.05)。罗哌卡因组48 h时舒芬太尼用药量明显少于对照组(P0.05)。与对照组相比,罗哌卡因组患者肠功能恢复时间、首次下床活动时间、术后住院时间均明显缩短(P0.05),恶心呕吐评分明显降低(P0.05)。2组切口感染发生率比较,差异无统计学意义(P0.05)。结论罗哌卡因持续切口浸润麻醉用于开腹胃癌根治术后镇痛安全、有效,能够促进患者早期康复。     

150例腹腔镜全子宫联合胆囊切除术的临床效果观察

目的:探讨快速康复外科结合中医治疗在腹腔镜全子宫切除联合胆囊切除术中的临床应用效果。方法:选取天津市南开医院行腹腔镜全子宫切除联合胆囊切除术患者150例,随机分为对照组与观察组。观察组76例,给予快速康复外科技术及中医治疗干预。对照组74例,采用传统围手术期方法。观察两组术后首次肛门排气时间、术后首次进食时间、术后首次下床活动时间、术后不良反应和并发症、住院时间、平均住院费用。同时观察两组白细胞介素6(IL-6)、肿瘤坏死因子α(TNFα)、白细胞总数及C反应蛋白(CRP)的变化。结果:观察组术后首次肛门排气时间(26.83±5.25)h,首次进食时间(6.38±0.91)h、下床活动时间(8.32±1.28)h,住院时间(4.88±1.27)d,与对照组相比均明显缩短,平均住院费用(1.1±0.1)万元,也明显减少,差异有统计学意义(P0.05)。观察组术后不良反应14.47%,与对照组(32.43%)相比明显减少(P0.05),但并发症两组相比较无明显差异(P0.05)。两组术前IL-6、TNFα、白细胞总数及CRP水平差异无统计学意义,观察组与对照组术后24 h及72 h IL-6、TNFα、白细胞总数及CRP水平均高于术前水平,而术后24及72 h同一时间段内,观察组IL-6、TNFα、白细胞总数及CRP水平均低于对照组,差异有统计学意义(P0.05)。结论:快速康复外科结合中医治疗应用于腹腔镜全子宫切除联合胆囊切除术,能有效缩短术后首次肛门排气时间、首次进食时间、下床活动时间、住院时间,且平均住院费用及术后不良反应也明显减少。     

腹腔镜胆囊切除术围术期快速康复外科护理效果分析

目的分析腹腔镜胆囊切除术(LC)围术期快速康复外科(FTS)护理的效果。方法将76例接受择期LC的患者随机分为2组,每组38例。对照组围术期常规护理,研究组围术期实施FTS护理。比较2组的护理效果。结果研究组术后下床活动时间、肛门排气时间,以及住院时间短于对照组;术后并发症发生率低于对照组;患者及家属对临床工作满意度高于对照组。差异均有统计学意义(P0.05)。结论对接受择期LC的患者围术期实施FTS护理,能促进患者术后胃肠功能恢复,减少术后并发症风险,有利于加快患者康复。     

腹腔镜胆囊切除术围术期快速康复外科护理的应用效果

目的分析腹腔镜胆囊切除术(LC)围术期快速康复外科(FTS)护理的应用效果。方法随机将64例接受LC的胆囊良性疾病患者分为2组,每组32例。对照组行围术期常规护理,FTS组围术期实施FTS护理干预。比较2组的护理效果。结果 FTS组患者术后下床活动时间、住院时间、并发症发生率均优于对照组,差异有统计学意义(P0.05)。2组术后24 h、72 h的C反应蛋白(CRP)水平比术前均明显升高,FTS组患者升高幅度低于对照组,差异有统计学意义(P0.05)。结论 LC围术期实施FTS护理干预,能降低术后并发症发生率,减轻手术应激反应,促进患者术后早期康复。     

罗哌卡因局部麻醉减轻腹腔镜胆囊切除术后疼痛的临床观察

目的 观察腹腔镜胆囊切除术后应用罗哌卡因行局部麻醉对术后疼痛的缓解作用.方法 90例实施腹腔镜胆囊切除术患者,随机均分为三组:Ⅰ组用1%罗哌卡因10ml进行胆囊床喷洒;Ⅱ组用1%罗哌卡因5ml进行胆囊床喷洒,同时再用1%罗哌卡因5ml对三个切口进行局部注射,Ⅲ组为对照组.记录术后1、2、4、6、12、24 h的VAS.结果 术后1、2、4 h时,Ⅰ组和Ⅱ组的VAS显著低于Ⅲ组(P＜0.05),且Ⅱ组的VAS显著低于Ⅰ组(P＜0.05).术后6 h时,Ⅰ组和Ⅱ组的VAS显著低于Ⅲ组(P＜0.05),Ⅰ组和Ⅱ组差异无统计学意义.术后Ⅲ组需要哌替啶镇痛的患者数量显著多于Ⅰ组和Ⅱ组(P＜0.05).结论 罗哌卡因局部麻醉能显著减轻腹腔镜胆囊切除术后疼痛.     

快速康复外科理念护理干预应用于腹腔镜子宫肌瘤手术的效果

目的探讨快速康复外科(FTS)理念护理干预应用于腹腔镜子宫肌瘤手术的效果。方法选取2018-09—2019-02间接受腹腔镜子宫肌瘤手术的150例患者,按入院时间分为2组,各75例。对照组采用常规护理干预,观察组采用FTS理念的护理干预。比较2组术后禁食时间、首次排气时间、下床活动时间、住院时间、术后12 h及24 h疼痛评分、患者满意度。结果观察组术后禁食、首次排气、下床活动、住院时间短于对照组,术后12 h、24 h疼痛评分低于对照组,患者满意度高与对照组,差异均有统计学意义(P0.05)。结论 FTS理念的护理干预应用于子宫肌瘤腹腔镜手术患者,可缩短术后禁食及下床活动时间,缓解术后疼痛,促进术后恢复,提高患者满意度。     

加速康复外科策略应用于患儿腹腔镜阑尾切除术的效果

目的观察加速康复外科(enhanced recovery after surgery,ERAS)策略下超声引导下腰方肌神经阻滞应用于患儿腹腔镜阑尾切除术的临床疗效。方法选择拟行腹腔镜阑尾切除术患儿154例,男114例,女40例,年龄3～10岁,ASAⅠ或Ⅱ级,采用随机对照法分为两组:ERAS组(E组)和对照组(C组),每组77例。E组于超声引导下腰方肌深面注射0.2%罗哌卡因0.75 ml/kg,同时参照加速康复指南禁食4 h禁饮2 h、术前30 min给予功能饮料、麻醉诱导期家长陪同,麻醉方式采用喉罩全麻,即丙泊酚2～6 mg·kg~(-1)·h~(-1)持续泵入,吸入2%～6%七氟醚;C组采用传统麻醉方法,严格禁食6 h禁饮4 h,咪达唑仑、丙泊酚、阿曲库铵、舒芬太尼诱导后气管插管全麻。记录术后1、2、3、6、12、24、48 h VAS评分;随访患儿术后苏醒时间、首次肛门排气时间、下床时间、住院时间、家属满意度,术后恶心、呕吐等不良反应发生率。结果术后2、3、6、12 h E组VAS评分明显低于C组(P0.05);E组术后苏醒时间、首次肛门排气时间、下床时间、住院时间明显短于C组(P0.05),家属满意度明显高于C组(P0.05)。E组恶心、呕吐发生率明显低于C组(P0.05)。结论 ERAS策略应用于患儿腹腔镜阑尾切除术,并发症发生减少、术后疼痛明显减轻,患儿康复快、住院时间缩短,患儿家属满意度升高。     

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.