人工腰椎间盘置换术的临床应用初步报告

目的 探讨人工腰椎间盘置换术治疗腰椎间盘退行性病变的临床效果。方法 应用改良型SB ChariteⅢ型人工腰椎间盘行椎间盘置换术共6例。结果 随访率100％，随访时间18～30个月(平均24．5个月)。术前JOA下腰痛评分，平均分4．83；术后JOA评分，平均分11．83。疗效满意。结论 人工腰椎间盘置换术是治疗腰椎间盘退行性病变的一种新方法，其近期疗效满意，但应严格掌握手术适应证及进一步随访观察远期疗效。     

Mobi-C人工椎间盘置换治疗颈椎间盘突出症短期疗效观察

目的探讨应用颈椎人工椎间盘置换治疗颈椎间盘突出症的临床疗效。方法 2009-03-2012-03应用Mobi-C人工颈椎间盘置换术治疗25例颈椎间盘突出症患者,记录并统计分析患者在术前、术后的疼痛视觉模拟评分(VAS)、神经功能改善情况JOA评分及植入节段的运动范围影像学评估。结果 25例患者获得12～36个月随访,平均22个月。术前与术后(VAS)、JOA评分差异有统计学意义(P<0.05);而术前与术后植入节段的运动范围差异无统计学意义(P>0.05)。结论应用Mobi-C人工颈椎间盘置换术治疗颈椎间盘突出症,可以保留手术节段的活动功能,短期临床效果满意,是一种合理选择。     

腰椎间盘造影对人工椎间盘置换术的意义

目的：探讨椎间盘造影在人工腰椎间盘置换节段选择中的作用及意义。方法：对17例多节段或一般影像检查不能明确的腰椎退行性变患者的34个椎间隙行椎间盘造影检查，根据注入造影剂的量、注入时阻力、是否诱发出患者原有症状等确定责任椎间盘，并对相应节段行人工腰椎间盘置换术。结果：34个椎间隙造影中注入量大于2ml 17个间隙，推注时阻力减低者17个间隙，诱发出患者原有症状19个间隙，无与造影相关的并发症。对19个诱发出患者原有症状的椎间盘进行了置换术。随访16～42个月，平均30.4个月，术前患者JOA评分7～17分，平均9．9分，术后JOA评分20～29分，平均26．6分，差异有显著性（P〈0．01）。结论：椎间盘造影对准确选择人工腰椎间盘置换节段能够提供重要的指导作用。     

人工腰椎间盘置换术中期疗效分析

目的 对人工腰椎间盘置换术的中期疗效进行评价分析.方法 1999年12月至2006年12月应用Charité SBⅢ假体对65例患者施行人工椎间盘置换术,对其中获得平均5.8年(2～7.5年)随访的48例52个假体进行疗效评价分析.48例患者中,男性22例,女性26例,平均年龄43岁(36～58岁);椎间盘退变9例,椎间盘退变合并椎间盘突出34例,椎间盘突出术后复发5例.VAS疼痛评分术前平均9.3分,Oswestry功能评分术前平均45.8分.所有患者均在全身麻醉下经前路行人工椎间盘置换术.44例患者行单间隙椎间盘置换,其中L3,43例,L4,523例,L5～S118例;双节段4例,其中L3,4和L4,51例,L4,5和L5～S13例.分别在术前和术后1、3、6、12、24个月和末次随访时进行疗效评定.结果 疼痛视觉模拟评分:术后1、3、6、12、24个月分别为4.3、4.3、3.8、3.1、2.6分,末次随访时1.8分;Oswestry功能评分:术后1个月28.6分,术后24个月12.5分,末次随访时8.2分;活动度:末次随访时仅1例患者丧失活动度,其余患者保留活动度,平均5.5°.所有患者术后无假体移位、松动及下沉;1例患者对手术不满意.总满意率为98%.结论 人工椎间盘置换术是治疗腰椎间盘退变的有效方法之一,其远期疗效有待进一步观察.     

人工颈椎间盘置换术在后纵韧带骨化症中的应用

[目的]观察应用Bryan颈椎间盘假体置换术治疗后纵韧带骨化症的近期效果。[方法]2005年10月～2007年6月应用Bryan人工颈椎间盘假体置换术治疗局限型后纵韧带骨化症患者15例,术前和术后6个月时进行JOA评分,并摄颈椎前屈后伸位X线片,观察假体稳定性及颈椎置换节段的活动度。[结果]患者术后症状均明显缓解,随访6～24个月,JOA评分由术前平均8.5分上升至术后平均15.8分。置换节段保留了运动功能,假体稳定无移位。[结论]人工颈椎间盘置换术近期可保持前路减压的良好效果,同时可获得术后即刻稳定性。维持颈椎近正常的活动度。人工颈椎间盘置换术是治疗局限型后纵韧带骨化症的一种有效方法。     

Bryan人工颈椎间盘置换治疗颈椎间盘突出症

目的 探讨Bryan人工颈椎间盘假体置换治疗颈椎间盘突出症的临床疗效,总结其手术操作要点并分析有关并发症.方法 21例颈椎间盘突出症患者应用Bryan人工颈椎间盘进行颈椎间盘置换,术后常规予以非甾体类药物预防异位骨化.结果 所有患者术后症状明显缓解.术前和术后第1、12个月行JOA评分;摄术前和术后正侧、屈伸、左右侧屈位X线片,观察假体稳定性及置换颈椎节段的活动度.随访12～28个月,术后治疗效果Odom评级:优16例,良4例,可1例,优良率95.2%;JOA评分:术前平均7.9分(6～12分),术后第1个月平均14.1分(9～16分),第12个月平均15.7分(10～17分).置换节段术前和术后第1、12个月活动范围分别平均是:术前7.7°(5.8°～9.1°),术后1个月5.5°(3.9°～7.8°),术后12个月5.5°(4.0°～7.8°).末次随访未发现异位骨化、假体松动、脱落、下沉和颈椎生理曲度的改变.结论 Bryan人工颈椎间盘假体置换术治疗颈椎间盘突出症能明显缓解患者症状,维持颈椎近期正常活动范围和生理曲度,但远期疗效还需长期观察.     

人工腰椎间盘置换26例6年疗效分析

[目的]对人工腰椎间盘置换术的疗效进行临床和影像学评价。[方法]自1998年9月～2007年12月,应用SBCharit啨Ⅲ型假体对29例患者施行人工腰椎间盘置换术,对其中获得平均6.9年(3～9年)随访的26例30个节段假体进行疗效评价分析。26例患者中,男25例,女1例;平均年龄44.2岁(38～59岁);腰椎间盘退变性病变3例,腰椎间盘退变合并腰椎间盘突出症21例,腰椎间盘突出术后复发2例。VAS疼痛评分术前平均9.1分,Oswes-ty功能评分术前平均46.4分。所有患者均在全身麻醉下经腹壁前路行人工腰椎间盘置换术。22例行单节段置换,其中L4、58例、L4、5,L5S116例;二节段4例,均为L4、5和L5S1。本组分别在术前和术后1、3、6、12个月及末次随访时进行疗效分析。[结果]疼痛VAS评分:术后1、3、6和12个月分别为3.7、3.2、3.0和2.5分,2年时2.3分,末次随访时2.0分;Oswesty功能评分:术后1个月27.7分,术后3年9.7分,末次随访时7.4分,活动度:末次随访时1例活动度减小(4°),其余患者均有活动度,平均5.6°。所有患者术后无假体移位、松动和下沉;1例患者术后尚满意,总满意率96%。[结论]人工腰椎间盘置换术是治疗腰椎间盘退变的有效方法。     

人工椎间盘置换术治疗腰椎间盘突出症

目的 探讨人工腰椎间盘置换术治疗腰椎间盘突出症的临床效果。方法 自1999年12月～2001年12月对22例腰椎间盘突出症患者采用Link SB ChariteⅢ型人工椎间盘行椎间盘置换术,共置换假体30个,随访4～28个月（平均16个月）,分别于手术前后对患者的情况进行JOA评分。结果所有病例无术中并发症发生,术中出血100～800ml（平均320 ml）。术后第2d（早期病例为术后第7d）,患者可佩戴腰围下地,术后6周除去腰围恢复正常活动。术后X线片显示人工椎间盘位置正确,椎间隙高度恢复正常。患者腰腿痛症状消失,直腿抬高试验阴性。3例患者术后出现健侧肢体麻木。JOA评分较术前提高,差异有非常显著性意义（P<0.001）。无椎间盘假体脱落、失效,远期感染等术后并发症发生。结论 人工椎间盘置换术是治疗腰椎间盘突出症的有效方法,但应严格掌握手术适应证。     

相邻双节段颈椎人工椎间盘置换术疗效的初步观察

目的:探讨相邻双节段颈椎人工椎间盘置换术后颈椎曲度及临床功能的变化.方法:2004年4月-2007年1月收治因颈椎病行相邻双节段颈椎人工椎间盘置换术患者23例,其中使用Bryan人工椎间盘17例,术前颈椎曲度不良12例:使用Prodisc-C人工椎间盘6例,术前颈椎曲I度不良4例.统计并分析患者术前和术后3、12及24个月时颈椎运动范围、颈椎中立位曲度、手术节段Cobb角、手术节段是否发生异位骨化、手术邻近节段是否发生退变、术后Odom评分、JOA脊髓功能评分及颈肩痛VAS评分.结果:术后3、12及24个月时患者的颈椎活动范围、颈椎中立位曲度、手术节段Cobb角与术前比较无显著性差异(P＞0.05).术前颈椎曲度不良的患者使用Bryan人工椎间盘置换后局部后凸加重(P＜0.05);而使用Prodisc-C者得到改善(P＜0.05).所有患者的Odom、JOA和VAS评分较术前改善明显(P＜0.05).2例患者术后出现手术节段的异位骨化,1例出现邻近节段椎间盘退变.结论:相邻双节段颈椎人工间盘置换术基本保留了颈椎的曲度和运动功能,Prodisc-C颈椎人工椎间盘对曲度不良患者有一定的矫正作用.     

椎间盘置换术治疗腰椎间盘突出症

目的：探讨人工椎间盘置换术治疗腰椎间盘突出症的临床效果。方法：对6例腰椎间盘突出症息者用Link SB ChariteⅢ型人工腰椎间盘行椎间盘置换术，共置换假体6例。手术节段为L4、5 4例，L5S1 2例。结果：随访3～9个月，平均6个月，术中和术后未出现并发症，术后X线片显示人工椎间盘位置正确，椎间隙高度恢复正常，5例患者腰腿痛症状完全消失，直腿抬高试验阴性，1例劳累后仍感腰痛，6例均恢复工作和日常生活能力。临床评价：优5例，良1例。结论：人工椎间盘置换术是治疗椎间盘突出症的有效方法，近期效果满意，但应严格掌握手术适应证。     

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.