不同静脉麻醉药对听觉诱发电位指数的影响

目的　研究丙泊酚、咪唑安定、硫喷妥钠、氯胺酮麻醉时听觉诱发电位指数 (AEPI)的变化规律。方法　 4 8例择期手术拟行全身麻醉、无听力障碍和严重神经疾患、非颅脑手术病人 ,随机分为四组。Ⅰ组 (14例 )静注丙泊酚 2mg/kg ;Ⅱ组 (13例 )静注咪唑安定 0 2mg/kg ;Ⅲ组 (11例 )静注硫喷妥钠 5mg/kg ;Ⅳ组 (10例 )静注氯胺酮 2mg/kg。随后芬太尼 5 μg/kg、维库溴铵 0 15mg/kg静注 ,肌松满意后气管插管。记录麻醉诱导前、诱导中、诱导后插管前、插管后的HR、BP、SpO2 ,观察整个诱导期AEPI的变化规律。结果　Ⅰ、Ⅱ、Ⅲ组病人用药后AEPI进行性降低至 30以下。降到 30以下的平均时间分别为Ⅰ组 (6 2± 2 5 )分钟、Ⅱ组 (3 2± 1 9)分钟、Ⅲ组 (5 1± 2 6 )分钟 ;Ⅳ组病人AEPI无明显下降。插管后AEPI有上升趋势 ,吸入异氟醚后 (呼出气浓度 >0 8Vol% )能维持AEPI30以下 ;Ⅳ组病人插管后AEPI不稳定。结论　丙泊酚、咪唑安定、硫喷妥钠降低AEPI,而氯胺酮对AEPI无明显影响。AEPI在丙泊酚、咪唑安定、硫喷妥钠麻醉中可作为麻醉深度监测的指标之一。     

咪唑安定对患者麻醉手术前身心应激的调控

目的 本文目的在于探讨麻醉手术前使用咪唑安定对患者麻醉手术前身心应激的抑制程度。方法 选择40例20～60岁、ASAⅠ～Ⅱ级的择期手术患者,随机分为两组。Ⅰ组于麻醉前30min肌肉注射苯巴比妥钠0.1g;Ⅱ组于麻醉前30min肌肉注射咪唑安定0.06～0.08mg/kg。分别于用药前后测定患者SBP、DBP、HR、SpO_2、RR、焦虑视觉模拟评分(AVAT)、血浆内皮素(ET-1)、血清皮质醇(Cor)和白细胞介素-6(IL-6)水平。结果 两组患者在用药前后SBP、DBP、HR、SpO_2、RR无显著性变化(P>0.05)。Ⅰ组在用药前后AVAT、ET-1、Cor、IL-6水平无显著性变化(P>0.05);Ⅱ组用药后30min AVAT、ET-1、Cor、IL-6水平显著低于用药前(P<0.05)。结论 咪唑安定可以减轻麻醉手术前患者的生理和心理应激,且无严重不良反应。     

咪唑安定与硫喷妥钠复合应用的遗忘效果

咪唑安定可产生顺行性遗忘,硫喷妥钠则产生逆行性遗忘。作者观察了少量咪唑安定与诱导量硫喷妥钠复合应用后的遗忘效果及相互作用。对象及方法择期下肢手术ASAⅠ～Ⅱ级病人30例。分为咪唑安定+硫喷妥钠(M)组15例;未应用咪唑安定(T)组15例。麻醉前30min肌注羟嗪、雷尼替丁各50mg、阿托品0.5mg。入室监测心电、血压、脉搏血氧饱和度     

咪唑安定作为硬膜外阻滞前用药时间的探讨

目的　探讨咪唑安定肌注作为硬膜外阻滞麻醉前用药的最佳时间。方法　选择ASAⅠ～Ⅱ级择期手术行硬膜外麻醉患者 382例 ,入室后肌肉注射咪唑安定 0 1mg/kg ,按用药后 5、10、2 0、30及 4 0min随机分成五组。采用Ramsay镇静评分 ,记录SBP、DBP、HR及SpO2 等的变化。术后 2 4h随访麻醉操作及手术操作过程中遗忘情况。结果　以镇静评分 2～ 3分为最佳时间。 5、10min组得 2～ 3分者分别达 10 0 %与 96 15 % ,与 2 0、30、4 0min组比较有显著性差异 (P <0 0 5 )。 5、10min组在硬膜外阻滞操作过程中患者既有适当镇静作用 ,又能主动合作。 2 0min后各组镇静评分大于 3分 ,患者难以和麻醉者很好合作。肌注咪唑安定 0 1mg/kg后 5～ 10minSpO2 有明显下降 (P<0 0 5 )。术后 2 4h随访 ,患者对麻醉操作完全遗忘达 98 85 %～ 10 0 % ,手术操作完全遗忘达89 4 1%～ 10 0 %。结论　肌注咪唑安定 0 1mg/kg作为硬膜外阻滞麻醉前用药 ,以用药后 5～ 10min进行硬膜外穿刺操作为合适时间。     

术前应用咪唑安定和苯巴比妥钠效果比较

手术前多数患者处于不同程度的焦虑状态,使术前应激反应增强,不仅影响麻醉手术的进行,还影响到手术后的恢复。本文观测和比较患者手术前应用咪唑安定或苯巴比妥钠的镇静抗焦虑作用、顺行性遗忘效果及对血压脉率的影响。方　　法选择硬膜外麻醉下行择期手术的成年患者120例,均无明显呼吸、循环和内分泌系统疾患,肝肾功能和神经精神系统正常,无色盲;既往无长期应用镇静药物史;体重40～50kg。随机分成四组,每组30例。组咪唑安定0.1mg·kg-1,组咪唑安定0.07mg·kg-1,组苯巴比妥钠3mg·kg-1;～组药液均配制成1ml。组生理盐水1ml。药物由专人于麻…     

咪唑安定麻醉前用药与遗忘作用

咪唑安定具有良好的镇静、催眠、抗焦虑和明显的顺行性遗忘作用。本文复习咪唑安定的麻醉前用药与遗忘作用。咪唑安定用于麻醉前用药咪唑安定 (MID)的一种主要药理是通过与γ 氨基丁酸(GABAA)受体上的苯二氮类调控位点结合 ,增强GABA介导的氯离子内流 ,使膜电位向超级化偏移 ,对电兴奋性起抑制作用。此外 ,临床浓度的MID还具有可逆的K+ 离子通道的抑制作用 ,并呈浓度依赖性 ,其半数抑制浓度 (ES50 ) :(8.31± 2 .78)× 1 0 8mol/L ,Hill系数 :0 .90± 0 .1 6 [1 ] 。咪唑安定肌注麻醉前用药　麻醉前用药最适剂量应该既产生良好镇…     

咪唑安定口服作为术前用药的临床效果观察

咪唑安定 6 0 μｇ/ｋｇ肌注作为成人麻醉前用药 ,认为能产生满意的镇静、抗焦虑和顺行性遗忘作用 ,已较广泛应用于临床[1,2 ] 。咪唑安定片剂口服虽方便又无痛苦 ,而成年人口服多大剂量能作为麻醉前用药极少报告。为此 ,本文将探讨口服咪唑安定作为成人麻醉前用药的最佳剂量 ,并与肌注咪唑安定作对比观察 ,供临床参考。资料与方法一般资料　选择ＡＳＡⅠ～Ⅱ级择期行妇科手术患者 84例 ,年龄 30～ 5 5岁 ,既往均无长期应用镇痛、镇静、抗焦虑药的病史。手术麻醉均选用腰麻 硬膜外联合麻醉 (ＣＳＥＡ) ,腰麻应用重比重的 0 75 %布比卡因 1…     

非全麻病人应用咪唑安定的顺行性遗忘作用

目的观察咪唑安定用于非全麻病人的顺行性遗忘作用。方法选择ASAⅠ～Ⅱ级,在腰-硬联合麻醉下行下腹部或下肢手术的病人120例,随机均分为咪唑安定组(A组)和氟哌利多组(B组),分别静注咪唑安定和氟哌利多后再行麻醉操作,观察两组病人对麻醉手术记忆的遗忘效果。结果A组完全遗忘40例(66.7%);不全遗忘20例(33.3%);B组不全遗忘10例(16.7%);无遗忘50例(83.3%)。两组遗忘程度比较差异有极显著意义(P<0.01)。结论非全麻病人应用咪唑安定有良好的顺行性遗忘效果。     

咪唑安定作为小儿术前用药的临床观察

我院传统的小儿术前用药是苯巴比妥钠 ,效果较差。为此我们把咪唑安定作为小儿术前用药与苯巴比妥钠进行比较 ,现报告如下。资料与方法ＡＳＡⅠ～Ⅱ级患儿随机分成两组 ,苯巴比妥钠 5ｍｇ/ｋｇ(Ａ组 ,ｎ =16)和咪唑安定 0 2 0ｍｇ/ｋｇ(Ｂ组 ,ｎ =2 0 ) ,两组均肌肉注射 ,同时注射阿托品 ,术前 3 0分钟接入手术室内同一辅助房间进行注射、镇静评分和监测。镇静评分由同一医师进行 ,评分采用自拟的 5～ 1分评分法表示 :哭吵躁动 ( 5分 ) ,紧张不安 ( 4分 ) ,安静但无睡意 ( 3分 ) ,淡漠有睡意 ( 2分 ) ,入睡 ( 1分 )。监测并记录用药前 ,用…     

比较右美托咪定和咪唑安定对焦虑患者记忆功能的影响

【摘要】〓目的〓比较右美托咪定和咪唑安定对焦虑患者记忆功能的影响。 方法〓60例择期在腰硬联合麻醉下行下腹部或下肢手术且焦虑评分>30 mm的患者,随机等分为4组(n=15):右美托咪定(dexmedetomidine, DXM)0.5 µg·Kg^-1组(D0.5组)、右美托咪定1 µg·Kg-1组(D1组)、咪唑安定组(M组)和对照组(C组)。各组分别在L2/3间隙穿刺麻醉,麻醉平面固定后,分别于10 min内泵注DXM 0.5 µg·Kg^-1、DXM 1 µg·Kg^-1、咪唑安定0.07 mg·Kg^-1和生理盐水10 mL。评估各组患者术前及用药前、用药后30 min的焦虑、镇静程度及记忆情况以及手术结束后4小时的记忆情况。记录并比较4组患者术中的平均压(MBP)、心率(HR)、血氧饱和度(SpO₂)、呼吸次数(RR)等。 结果〓D_0.5、D₁及M组用药后均有一定程度的镇静作用,焦虑程度均较术前明显减轻(P<0.05)。与对照组相比,D_0.5、D₁、M组均有顺行性遗忘作用(P<0.05),D1组顺行性遗忘程度明显高于D_0.5组(P<0.05),与M组相当(P>0.05)。用药后D_0.5、D₁组MBP和HR低于M、C组(P<0.05)。各组RR无明显差异(P>0.05),而M组有2人SpO2下降至94%以下。 结论〓右美托咪定对焦虑患者有明显的镇静、抗焦虑作用,对记忆的影响与剂量有关。1 µg·Kg^-1右美托咪定的顺行性遗忘作用与咪唑安定0.07 mg·Kg-1相当。     

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.