微型钛板改良单开门颈椎管扩大成形术治疗脊髓型颈椎病的临床效果

【摘要】〓目的〓评价微型钛板改良单开门颈椎管扩大椎板成形术治疗脊髓型颈椎病的临床效果。方法〓2008年1月~2012年2月,观察46例多节段脊髓型颈椎病(MCSM)行微型钛板改良单开门颈椎管扩大椎板成形术的脊髓型颈椎病患者,对比术前及术后JOA评分,在CT上测量C5节段椎管术前、术后6个月的矢状径,计算椎管扩大率[(术后椎管矢状径-术前椎管矢状径)/(术前椎管矢状径)×100%],观察单开门门轴侧骨融合情况。结果〓平均随访18个月(6~24个月)。术前平均JOA评分8.2分,术后平均JOA评分14.8分。C5节段椎管矢状径术前为8.6±1.1 mm,术后6个月为16.1±0.9 mm,椎管扩大率为(74.3±14.4)%。术后6个月,可以观察到单开门门轴侧骨融合,无螺钉松动及再“关门”现象。结论〓微型钛板改良单开门椎管成形术治疗脊髓型颈椎病临床效果满意,防止再关门。     

纳米人工椎板在颈椎后路减压椎管重建手术中的临床应用研究

[目的]评估颈椎后路减压手术中应用纳米人工骨重建椎管后临床症状的改善和影像学变化。[方法]观察组30例多节段脊髓型颈椎病行颈椎后路减压人工椎板椎管重建术,对照组38例多节段脊髓型颈椎病行颈椎后路双开门椎管扩大成形术。两组术后平均随访25个月。比较两组的手术时间、术中出血量、术前术后JOA(日本矫形外科学会)评分,轴性症状及C5神经根麻痹的发生情况,颈椎X线片及CT了解椎管矢状径扩大情况及人工椎板融合情况。[结果]观察组手术时间平均92 min,术中出血量平均316 ml,低于对照组,有1例发生C5神经根麻痹。两组在手术时间、出血量及C5神经根麻痹的发生方面比较差异有统计学意义(P<0.05)。观察组术后JOA评分改善率为74.3%,3例出现轴性症状,理疗治疗后好转。术后各节段椎管矢状径皆超过14 mm,术后1年和2年人工骨骨性融合率分别为43.3%和71.1%。两组在JOA评分改善率、轴性症状发生率、椎管矢状径扩大及植骨融合方面比较差异无统计学意义(P>0.05)。[结论]在颈椎后路全椎板切除减压手术中应用纳米人工椎板重建颈椎管效果良好,获得与颈椎后路双开门椎管扩大成形术相同的治疗效果,而且具有手术时间短、术中出血少及并发症较少的优点。     

颈椎“双开门”椎管扩大成形同种异体骨植骨治疗脊髓型颈椎病的疗效分析

目的 总结分析颈椎后路双开门椎管扩大成形同种异体骨植骨治疗脊髓型颈椎病的临床效果.方法 对61例行颈椎后路“双开门”椎管扩大成形同种异体骨植骨治疗的脊髓型颈椎病患者进行回顾性分析,采用JOA评分法、颈椎管平均矢状径评价临床疗效,X线、CT判定植骨融合状况.结果 术后所有患者症状体征得到改善,JOA评分由术前平均10.6...     

多节段脊髓型颈椎病的前后路外科治疗

目的 比较前路减压植骨内固定和后路单开门椎管扩大成形术对多节段脊髓型颈椎病的治疗效果.方法 回顾性分析我院2001年1月～2004年6月手术治疗多节段脊髓型颈椎病患者78例,前路减压植骨内固定43例,后路全椎板切除减压术或单开门椎管扩大成形术治疗35例,术前和术后按照JOA评分系统进行评分并计算恢复率,MRI测量硬脊膜囊矢状径并计算膨胀回复率.结果 术后随访6个月～4年2个月,平均1年11个月,两组手术病例术前JOA评分及硬脊膜矢状径比较无统计学意义(P＞0.05),术后JOA评分和恢复率,硬脊膜囊矢状径和膨胀回复率前路手术组高于后路手术组,差异均有统计学意义(P＜0.05).结论 前、后路减压手术均是治疗多节段脊髓型颈椎病的有效方法,前路减压植骨内固定术优于后路全椎板切除减压或单开门椎管扩大成形术.     

颈椎单开门椎管成形术结合微型钛板内固定治疗多节段脊髓型颈椎病

目的：探讨颈椎后路微型钛板内固定结合单开门椎管成形术治疗多节段脊髓型颈椎病的临床效果。方法2008年3月至2011年10月山东大学齐鲁医院沂南分院采用单开门椎管成形术结合微型钛板内固定治疗34例多节段脊髓型颈椎病患者,对患者术前及术后3周、15个月日本骨科学会（JOA）评分、椎管矢状径、轴性症状严重程度、颈椎活动度（ROM）进行评估。结果所有患者获随访10～18个月,平均随访时间13个月。术后3周、15个月JOA评分及椎管矢状径较术前均明显提高（P＜0.05）;术后3周及15个月的JOA评分、椎管矢状径比较,差异无统计学意义（P＞0.05）。颈部轴性疼痛发生率12%。术后ROM较术前有所降低,但差异无统计学意义（P＞0.05）。结论颈椎后路微型钛板内固定结合单开门椎管成形术是治疗多节段脊髓型颈椎病安全有效的方法。     

改良颈椎后路单开门椎管扩大成形术治疗多节段脊髓型颈椎病的疗效观察

目的比较改良颈椎后路单开门椎管扩大成形术与传统颈椎后路单开门椎管扩大成形术治疗多节段脊髓型颈椎病的临床疗效。方法回顾性分析自2016-05—2019-03诊治的80例多节段脊髓型颈椎病,40例采用改良颈椎后路单开门椎管扩大成形术治疗(改良组),40例采用传统颈椎后路单开门椎管扩大成形术治疗(传统组)。比较2组手术时间、术中出血量、住院时间、术后出现轴性症状数以及末次随访时的疼痛VAS评分、JOA评分、JOA评分改善率、Tsuji轴性症状评分。结果 80例均顺利完成手术,随访时间平均15.0(7～28)个月。改良组术后出现轴性症状数、术中出血量较对照组少,差异有统计学意义(P0.05)。2组手术时间、住院时间比较差异无统计学意义(P0.05)。末次随访时2组疼痛VAS评分、JOA评分、JOA评分改善率、Tsuji轴性症状评分比较差异无统计学意义(P0.05)。结论改良颈椎后路单开门椎管扩大成形术与传统颈椎后路单开门椎管扩大成形术治疗多节段脊髓型颈椎病均能取得满意的临床疗效,但前者能有效降低术中出血量,简化手术步骤,术后可有效减少轴性症状的发生率。     

颈椎后路椎管扩大成形加短节段固定手术疗效及影响因素分析

目的探讨颈椎后路椎管扩大成形加短节段固定手术治疗脊髓型颈椎病的疗效及影响因素。方法 2006-08-2008-06因脊髓型颈椎病行颈椎后路单开门椎管扩大成形加颈椎侧块钉棒系统固定融合术的患者21例,将患者的年龄、病程、术前椎管矢状径值、骨性椎管扩大率、脊髓后移距离、术前JOA评分诸影响因素与JOA改善率进行多元逐步回归分析,分析JOA改善率与上述诸因素的相关性。结果术前JOA评分、病程与JOA改善率明确相关,有显著性统计学意义。病程与JOA改善率呈明显负相关,术前JOA评分与JOA改善率呈明显正相关。结论颈椎后路单开门椎管扩大成形加颈椎侧块钉棒系统固定融合术是治疗脊髓型颈椎病的有效方法;术前JOA评分和病程是决定脊髓型颈椎病预后的重要因素,是判断预后的重要指标,两者相比,术前JOA评分更重要。     

颈椎"双开门"椎管扩大成形人工骨植骨治疗颈椎疾患的疗效分析

目的总结分析颈椎后路双开门椎管扩大成形羟基磷灰石人工骨(hydroxyapatite artificial bone,HAB)植骨治疗颈椎疾患的临床效果.方法对130例行颈椎后路"双开门"椎管扩大成形HAB植骨治疗的患者进行回顾性分析,采用JOA评分法、颈椎管平均矢状径、颈椎屈伸活动度、颈椎弯曲类型中前弯型比率、相邻椎间的稳定性评价临床疗效,X线、CT判定植骨融合状况.结果术后所有患者症状体征得到改善,JOA评分由术前平均10.8分增加至出院时平均14.0分,改善率为51.6%;最狭窄部颈椎管平均矢状径由术前8.8mm增加至15.4mm,扩大率为75.0%;颈椎屈伸活动度由术前41.6°±10.2°下降为25.2°±11.2°;前弯型比率由术前79.2%下降为73.9%.4例出现相邻椎间失稳.平均随访5年7个月,术后5年时人工骨骨性融合率为56%.结论应用HAB的颈椎后路双开门椎管扩大成形术是一种安全、有效、有应用价值的手术方法.     

颈后路两种手术方式治疗脊髓型颈椎病远期疗效比较

目的通过回顾性研究，对比颈椎后路单开门椎管扩大成形术和双开门椎管扩大成形术治疗脊髓型颈椎病的远期疗效。方法我院自1995-1999年采用颈椎后路椎板成形术治疗并成功随访的142例脊髓型颈椎病患者，按手术方式不同分为单开门组（1组）和双开门组（2组）。分析复查颈椎CT测量椎管矢状径，并按照JOA评分系统计算恢复率。结果术后随访8～11年，平均9．5年，患者术后椎管矢状径双开门组大于单开门组，差异有显著的统计学意义（P〈0．01）。术后永久性并发症发病率单开门组显著高于双开门组（P〈0．01），而暂时性并发症发病率和术后神经功能恢复优良率，两组差异无意义（P〉0．05）。结论颈椎后路单开门和双开门椎管扩大成形术均取得令人满意的优良率。双开门手术在扩大椎管方面优于单开门手术，且术后永久性并发症发病率略低于后者。     

前路椎间隙减压融合与后路单开门椎管扩大成形术治疗多节段脊髓型颈椎病的疗效比较

目的比较颈前路椎间隙减压植骨融合内固定与后路单开门椎管扩大成形术治疗多节段脊髓型颈椎病的临床疗效。方法回顾性分析自2013-01—2015-12诊治的112例累及4节段(C3~7)的脊髓型颈椎病,49例采用颈前路椎间隙减压植骨融合内固定术治疗(前路组),63例采用后路单开门椎管扩大成形术治疗(后路组)。比较2组手术时间、术中出血量、术后引流量、住院时间,术后1周、术后3个月、末次随访时椎间高度、颈椎生理曲度C值、JOA评分。结果 112例均获得随访,随访时间平均24.3(18~28)个月。前路组在手术时间、术中出血量、术后引流量、住院时间,以及术后椎间高度、颈椎生理曲度C值、JOA评分方面均优于后路组,差异有统计学意义(P 0.05)。前路组所有患者随访期间均获得骨性融合。结论与颈后路单开门椎管扩大成形术相比,颈前路椎间隙减压植骨融合内固定术治疗多节段脊髓型颈椎病能更有效增加病变节段椎间高度,恢复颈椎生理曲度,改善术后脊髓神经功能,而且手术创伤更小。     

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.