经皮微波和射频消融治疗肝细胞性肝癌的临床比较研究

目的探讨经皮微波和射频消融治疗肝癌临床效果的差异。方法以相同的纳入标准,回顾性比较了肝细胞性肝癌经超声引导经皮微波消融49例98个结节和射频消融53例72结节的局部疗效、并发症和远期生存率。结果微波组与射频组比较,肿瘤完全消融率分别为94.9%(93/98)和93.1%(67/72)(P=0.75),局部复发率为11.8%(11/93)和20.9%(14/67)(P=0.12)。主要并发症发生率分别为8.2%(4/49)和5.7%(3/53)(P=0.71)。1、2、3年无瘤生存率微波组分别为45.9%、26.9%和26.9%,射频组为37.2%、20.7%和15.5%(P=0.53)。1、2、3、4年累积生存率微波组分别为81.6%、61.2%、50.5%和36.8%,射频组为71.7%、47.2%、37.6%和24.2%(P= 0.12)。结论经皮微波和射频消融治疗肝癌的局部疗效、并发症和远期生存率无显著差别,均为安全有效的肝癌治疗手段。     

肝切除和微波消融治疗结直肠癌肝转移的效果比较

目的 比较肝切除和微波消融（microwave ablation,MWA）治疗结直肠癌肝转移（CRLM）的疗效。方法 回顾性分析2013年1月至2020年7月98例CRLM患者的临床资料,根据治疗方法不同分为2组,肝切除组31例,MWA组67例。MWA组共治疗105个病灶,其中特殊部位病灶36个,非特殊部位病灶69个。Kaplan-Meier法绘制生存曲线,Log-rank（Mantel-Cox）检验比较两组肿瘤复发率和生存差异。χ²检验比较两组消融不完全率,单因素和多因素Logistic回归分析消融不完全的危险因素。结果 随访截止2020年10月30日,中位随访时间38（4～94）个月。肝切除组中位肝内复发时间22（95%CI 13～49）个月,明显长于MWA组9（95%CI 6～12）个月（P＜0.001）。肝切除组中位生存时间为60（95%CI 33～86）个月,也明显长于MWA组36（95%CI 30～41）个月（P=0.040）。肝切除组和MWA组1、5年累积生存率无统计学差异（100% vs97%,χ² =0.945,P=1.000;36% vs 27%,χ²=0.437,P=0.508）。肝切除组3年累积生存率高于MWA组（74% vs 48%,χ² =6.013,P=0.014）。特殊部位组消融不完全率明显高于非特殊部位[33.3%（12/36）vs 15.9%（11/69）,χ² =4.183,P=0.041]。肿瘤直径≥3 cm、特殊部位、CEA≥200 ng/mL是消融不完全的危险因素,其中肿瘤直径≥3 cm是消融不完全的独立危险因素。结论 可切除性CRLM手术切除的疗效优于微波消融,直径大于3 cm的肿瘤不宜微波消融治疗。     

病灶面积最大投影法用于CT引导下经皮肝肿瘤微波消融术

目的探讨病灶面积最大投影法在CT引导下经皮肝肿瘤微波消融术中的应用价值。方法对23例肝肿瘤患者行CT引导下经皮肝肿瘤微波消融治疗,其中15例(研究组)在术中采用病灶面积最大投影法指导消融针穿刺并预测消融范围,8例(对照组)行常规CT引导下经皮微波消融。比较2组术中穿刺次数、术后并发症情况及近期疗效。结果研究组术中穿刺次数少于对照组[(1.27±0.46)次vs (3.62±0.74)次;t=-9.461,P0.001]。2组患者术后并发症仅为肝包膜下出血,且研究组发生率低于对照组[6.67%(1/15) vs 37.50%(3/8);χ~2=3.976,P=0.041]。研究组术后6个月内肝肿瘤完全消融率明显高于对照组[93.33%(14/15) vs 50.00%(4/8);χ~2=5.647,P=0.017]。结论 CT引导下经皮肝肿瘤微波消融术中采用病灶面积最大投影法指导消融针穿刺并预测消融范围,有利于提高肿瘤完全消融率,同时减少并发症。     

CT引导下穿刺活检联合相同针道微波消融治疗肺癌术后同侧单发恶性倾向肺结节

目的观察CT引导下穿刺活检联合相同针道微波消融治疗肺癌术后同侧单发恶性倾向肺结节的有效性及安全性。方法将56例(56枚结节)肺癌术后同侧单发恶性倾向肺结节患者随机分为观察组和对照组,每组28例。对观察组于CT引导下穿刺活检后经同轴套管同针道行微波消融,对照组于CT引导下穿刺活检后经异穿刺点交叉针道行微波消融,对比2组疗效及并发症。结果 2组穿刺活检和微波消融操作成功率、总有效率及局部控制率均为100%。术后24 h内,观察组气胸、咯血及胸腔积液发生率分别为17.86%(5/28)、7.14%(2/28)和7.14%(2/28),对照组分别为21.43%(6/28)、7.14%(2/28)和10.71%(3/28),组间差异均无统计学意义(P均0.05)。随访6个月,2组均未见针道种植转移、肺栓塞及支气管胸膜瘘等并发症。结论 CT引导下穿刺活检联合相同针道微波消融治疗肺癌术后同侧单发恶性倾向肺结节效果确切,安全性较好。     

肝动脉栓塞化疗联合微波消融与单纯手术切除对小肝癌疗效比较

目的对比肝动脉栓塞化疗(TACE)联合微波消融(MWA)与单纯手术切除对小肝癌的治疗效果。方法回顾性分析2008年1月至2013年1月共65例小肝癌病人临床资料。65例中30例行肝动脉栓塞化疗联合微波消融,35例单纯手术切除治疗。比较两组肿瘤治疗后的总并发症发生率,术后1、2、3年生存率和复发率等情况。结果肝动脉栓塞化疗联合微波消融组总并发症发生率为10.0%,低于手术组并发症发生率(31.4%),差异有统计学意义(x~2=4.389,P=0.036)。肝动脉栓塞化疗联合微波消融组术后1、2、3年复发率为6.7%、13.3%、23.3%,手术组术后1、2、3年复发率为11.4%、17.1%、31.4%,两组复发率比较差异无统计学意义(x~2=0.465,P=0.495)。肝动脉栓塞化疗联合微波消融组术后1、2、3年总生存率为93.3%、80.0%、60.0%,手术组术后1、2、3年总生存率为91.4%、77.1%、57.1%,两组的生存率比较差异无统计学意义(x~2=0.078,P=0.78)。结论肝动脉栓塞化疗联合微波消融的治疗效果确切,其术后并发症发生率较低,远期疗效与手术切除相近,可考虑作为小肝癌的首选治疗。     

冷冻消融软组织肉瘤消融率的影响因素

目的探讨冷冻消融治疗软组织肉瘤消融率的影响因素。方法收集接受氩氦刀冷冻消融治疗的60例软组织肉瘤的资料,于冷冻消融治疗1个月后,根据患者情况选择CT或MRI检查判断消融率,对冷冻消融软组织肉瘤消融率的影响因素进行统计学分析。结果单因素分析显示,肿瘤最长径和肿瘤生长部位与软组织肉瘤冷冻消融术后消融率有关(χ~2=10.408,P=0.015;χ~2=36.778,P=0.006)。多因素分析显示,肿瘤生长部位是冷冻消融术后消融率的独立影响因素(P0.05)。结论冷冻消融治疗软组织肉瘤安全有效。软组织肉瘤生长部位是冷冻消融后消融率的独立影响因素。     

CT引导经同轴套管微波消融同步穿刺活检肺高度可疑恶性磨玻璃结节

目的探讨CT引导经同轴套管对肺高度可疑恶性磨玻璃结节(GGN)行微波消融同步活检的可行性。方法回顾性分析54例肺单发高度可疑恶性GGN(直径10～25 mm)患者,其中26例接受CT引导同轴微波消融同步活检(消融同步活检组),28例接受单纯CT引导穿刺活检(单纯活检组);对比2组病理诊断率及出血、气胸发生率。结果 2组均顺利完成操作,技术成功率均为100%。消融同步活检组病理诊断率88.46%(23/26),气胸率26.92%(7/26);单纯活检组病理诊断率92.86%(26/28),气胸率32.14%(9/28),差异均无统计学意义(P均0.05);但消融同步活检组出血率30.77%(8/26),低于单纯活检组[42.86%(12/28),χ~2=5.962,P=0.028]。结论 CT引导经同轴套管对肺高度可疑恶性磨玻璃结节行微波消融同步活检安全、有效,出血风险低于单纯CT引导穿刺活检。     

CT引导下射频消融治疗肺部恶性肿瘤的疗效评价

目的探讨CT引导下肺恶性肿瘤射频消融后的影像学表现、临床疗效及安全性。方法对32例患者共39个肺部肿瘤病灶行CT引导下射频消融,直至即时CT影像上出现磨玻璃影覆盖病灶周围;术后1个月进行复查,其后每3个月随访,并评估影像学上消融灶变化。结果射频消融过程均顺利,无严重的治疗相关性并发症;病灶完全消融率89.19%(33/37),不完全消融率10.81%(4/37);术后1个月消融灶多表现为空洞样或结节样,长期随访中,完全消融的病灶多呈缩小趋势,而不完全消融的4个病灶均出现复发。中位总生存期为21.0月,中位无进展生存时间为17.3个月,中位疾病进展时间为18.0个月。结论 CT引导下射频消融治疗肺部恶性肿瘤安全性好,且病灶控制率高。     

CT引导下射频消融治疗骨肿瘤的疗效及护理

【摘要】〓目的〓观察CT引导下射频消融治疗骨肿瘤的临床疗效并总结护理体会。方法〓收集骨肿瘤患者共78例,均予射频消融治疗,其中对照组(n=36)遵医嘱给予基础护理,观察组(n=42)采用临床护理路径进行全程护理。结果〓78例患者均在CT引导下成功实施射频消融术,手术成功率、术后随访6个月生存率100%。观察组患者健康知识掌握情况显著优于对照组,SAS评分明显低于对照组(P均<0.01);观察组术后并发症发生率明显低于对照组(2.4% vs.16.7%,P<0.05)。结论〓CT引导下射频消融术治疗骨肿瘤有理想疗效,近期生存率高,配合临床护理路径干预措施,可进一步降低术后并发症发生风险,提高患者疾病认知率和护理满意度。     

腹腔镜超声与开腹超声引导肝癌微波消融的对比分析

目的比较腹腔镜超声与开腹超声引导原发性肝癌(简称肝癌)微波消融的疗效与安全性。方法回顾性分析我院2015年1月至2019年7月行超声引导肝癌微波消融治疗的46例肝癌患者临床资料,其中腹腔镜超声引导肝癌微波消融治疗(腹腔镜组)21例,开腹超声引导肝癌微波消融治疗(开腹组)25例。比较两组的手术时间、消融时间、术中出血量、术后肝功能、术后并发症发生率、胃肠功能恢复时间、住院时间、术后住院时间、住院费用、及肿瘤完全消融率差异。结果与开腹组相比,腹腔镜组术中出血量少(P=0.015)、胃肠功能恢复时间短(P0.001)、术后丙氨酸氨基转移酶低(P=0.014)、天门冬氨酸氨基转移酶低(P=0.009)、术后住院时间短(P=0.005);而手术时间、消融时间、住院时间、术后并发症发生率、住院费用及肿瘤完全消融率均无明显差别。结论腹腔镜超声与开腹超声引导肝癌微波消融均安全、有效,腹腔镜超声引导手术创伤更小、术后恢复快,但应严格把握其指证。     

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 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.