丹红注射液减轻草酸钙结晶肾损伤的实验研究

目的：探讨丹红注射液对小鼠体内草酸钙结晶性肾损伤的影响。方法：36只C57BL／6小鼠随机分为6组,空白对照组（A组）、正常对照组（B组,生理盐水100mg／kg）、单纯结晶组（c组,乙醛酸盐100mg／kg）、丹红干预低剂量组（D组,100mg／kg）、中剂量组（E组,200mg／kg）、高剂量组（F组,300mg／kg）,丹红干预组为乙醛酸盐诱导结晶肾损伤基础上加用不同浓度的丹红注射液,在连续给药7d后,检测各组小鼠血生化指标,肾组织钙含量水平,比较各组小鼠超氧化物歧化酶（SOD）、谷胱甘肽还原酶（GSH）、过氧化氢酶（CAT）和丙二醛（MDA）含量或活力水平及光镜下观察各组小鼠肾组织切片中草酸钙结晶体分布及组织病理改变。结果：与单纯结晶组相比,给予丹红注射液后的小鼠肾脏组织SOD、GSH和CAT显著上升,而MDA、血清尿素氮（BUN）及肌酐（Scr）水平、肾组织钙含量显著下降（P〈0．05）,肾组织草酸钙结晶沉积及肾脏病理组织损伤均低于单纯结晶组（P〈0．05）。结论：丹红注射液可能通过抑制过氧化应激途径减轻小鼠草酸钙结晶性肾损伤。     

海绵体内联合用药对筛选非血管性勃起功能障碍剂量选择的研究

本文探讨阴茎海绵体内注射前列腺素E1（PGE1）和罂栗碱（PAP）联合用药筛选非血管性勃起功能障碍的剂量选择。对20例勃起功能正常组和25例非血管性勃起功能障碍组采用不同剂量注射,并用多普勒超声检测阴茎海绵体动脉收缩期最大流速（PSV）和舒张期流速（EDV）。结果 1．小剂量（PGE1 10μg PAP7.5mg）联合用药就可明显增加阴茎血流,产生良好的勃起,与ICI前相比有显著差异（P＜0．01）;2．增加剂量与小剂量注射相比阴茎血流稍有增加,但各组间无显著差异（P＞0．05）;3．小剂量联合肜药未出现阴茎持续勃起和局部疼痛。作者认为小剂量联合用药对非血管性勃起功能障碍患者就能产生良好的阴茎血流,多普勒超声可客观地评价阴茎的血流参数,为ICI的药物剂量选择提供依据。     

7种常用中药注射剂与0.9％氯化钠配伍的稳定性研究

目的 观察7种常用中药注射剂与0.9％氯化钠注射液配伍的稳定性,以指导临床药物护理.方法 分别检测红花黄色素、复方苦参注射液、黄芪注射液、康艾注射液、艾迪注射液、注射用灯盏花素、注射用丹参与0.9％氯化钠配伍后0～4 h的颜色、澄明度、微粒数、pH值及吸光度.结果 4h内溶液澄明,未见沉淀生成及变色,pH值在正常范围内略有变化,不溶性微粒未发生大幅度改变,吸光度在正常值范围内.结论 7种常用中药注射剂与0.9％氯化钠配伍后溶液在4h内基本稳定,其中1～2 h配伍使用最为稳定.建议中药注射剂配伍静置一段时间后输注,以提高输液安全性.     

不同剂量丙种球蛋白联合地塞米松治疗小儿特发性血小板减少性紫癜的临床疗效分析

目的：探讨不同剂量丙种球蛋白联合地塞米松治疗小儿重症特发性血小板减少性紫癜的疗效观察。方法将120例小儿特发性血小板减少性紫癜患儿随机分为对照组,小剂量组和大剂量组,每组各40例,所有患者均接受采用地塞米松注射液治疗,大剂量组患儿给予丙种球蛋白400mg/（kg·d）,1次/d,连用5d;小剂量组患儿给予丙种球蛋白200mg/（kg·d）,1次/d,连用5d,观察比较三组临床疗效,血小板上升时间,血小板恢复正常时间,出血停止时间。结果小剂量组与大剂量组临床疗效,血小板上升时间,血小板恢复正常时间,出血停止时间比较,差异无统计学意义（P ＞0.05）,但与对照组比较,差异均有统计学意义（P ＜0.05）。结论丙种球蛋白联合地塞米松能够显著改善小儿特发性血小板减少性紫癜临床症状,迅速提高血小板数,同时小剂量丙种球蛋白与大剂量治疗效果相当,治疗费用更低,值得临床推广使用。     

苦橘咳喘合剂的止咳化痰作用与急性毒性

摘要目的 观察苦橘咳喘合剂的止咳化痰效果，评价其急性毒性。方法采用小鼠氨水引咳实验、小鼠酚红实验、二甲苯小鼠耳廓肿胀实验和最大耐受量实验。结果镇咳实验中苦橘咳喘合剂小、中、大剂量组R值分别为112.26%，143.30%，162.07%，分别呈现为无效、有效和显效；苦橘咳喘合剂大、中剂量组能显著增加小鼠气管酚红排泌量，与正常对照组比较差异有统计学意义（P＜0.05或P＜0.01），且呈良好量效关系；苦橘咳喘合剂小 、中、大剂量组均能显著改善二甲苯所致小鼠耳廓肿胀度（P＜0.01），且呈良好量效关系；其最大耐受量为326.76 g·kg－1。结论苦橘咳喘合剂中、大剂量具有一定的镇咳祛痰作用和良好的抗炎效果，且安全性较好。     

枸杞多糖延缓小鼠皮肤衰老的实验研究

目的：研究枸杞多糖（Lyciumbar barum polysaccharides,LBP）对D-半乳糖拟衰老小鼠皮肤组织的延缓皮肤衰老作用。方法：80只2月龄昆明种小鼠随机分为四组：正常组（N）、衰老模型组（C）、低剂量LBP抗衰老组（L）和高剂量LBP抗衰老组（H）。衰老模型组与抗衰老用药组每日颈背皮下注射D-半乳糖溶液制造衰老模型。抗衰老用药组在注射D-半乳糖期间以LBP灌胃。42天后取小鼠背部皮肤检测。结果：衰老模型组、低、高剂量LBP抗衰老组小鼠皮肤含水量、表皮厚度、真皮厚度以及成纤维细胞数与正常对照组比较差异有显著性意义（P〈0.01）,组间两两比较差异有统计学意义。结论：D-半乳糖诱导的亚急性衰老模型是可靠的衰老实验动物模型,枸杞多糖能延缓皮肤衰老。     

糖尿病大鼠肾脏中vWF的表达及丹红注射液的干预研究

目的 观察丹红注射液干预前后糖尿病大鼠血清血管性假血友病因子（vWF）水平及肾组织中vWF的表达变化,探讨糖尿病肾病发病机制及丹红的干预效果.方法 36只雄性SD大鼠随机分为3组：正常对照组10只、糖尿病组14只、丹红干预组12只.除正常对照组外,其余各组均按55mg/kg剂量一次性腹腔注射1％链脲佐菌素（STZ）建立糖尿病大鼠模型.72h后采尾静脉血测血糖,以血糖值＞16.7mmol/L作为糖尿病大鼠模型建立的标准.造模成功后,丹红干预组按2mL/kg.d剂量腹腔注射丹红注射液.干预为期8周.于第8周末,收集各组大鼠血液、尿液及肾组织标本.然后检测血糖（BG）、总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白胆固醇（LDL-C）、血肌酐（Scr）、尿素氮（BUN）.放射免疫法检测24h尿白蛋白定量.酶联免疫分析法（ELISA）测定各组大鼠血清vWF的水平.肾组织进行HE染色在光镜观察肾脏形态学变化.用免疫组化的方法检测各组大鼠肾脏vWF的表达情况.应用实时荧光定量PCR技术检测肾组织vWF的表达情况.结果 糖尿病组大鼠血糖、胆固醇、甘油三酯、低密度脂蛋白胆固醇、血肌酐、尿素氮、24h尿白蛋白定量、肾脏肥大指数、血vWF水平明显高于正常对照组（P＜0.01）,糖尿病大鼠肾脏出现病理改变,糖尿病大鼠肾组织vWF的表达较正常对照组大鼠明显增加;应用丹红干预8周后,干预组大鼠胆固醇、甘油三酯、低密度脂蛋白胆固醇、血肌酐、尿素氮、24h尿白蛋白定量、肾脏肥大指数、血清vWF水平较糖尿病组明显减低（P＜0.05）,肾组织病理损伤减轻,肾脏vWF表达较糖尿病组明显降低.结论 糖尿病大鼠血清vWF水平及肾组织vWF表达增加,提示vWF与糖尿病肾病关系密切,可能参与了糖尿病肾病的发生、发展;而丹红能通过调节血脂、降低尿白蛋白、降低vWF的表达来发挥肾脏保护作用.     

蛹虫草多糖对四氧嘧啶糖尿病小鼠的调节作用

目的：研究预防性给予蛹虫草多糖（cordyceps militaris）对四氧嘧啶（alloxan momohydrate）糖尿病小鼠血糖及代谢的影响。方法：小鼠随机分为：正常对照组、四氧嘧啶糖尿病模型组（200mg/kg）、阿卡波糖组（20mg/kg）、低剂量蛹虫草多糖组（35mg/kg）、中剂量蛹虫草多糖组（70mg/kg）、高剂量蛹虫草多糖组（140mg/kg）。连续4周灌胃,末次给药后,尾静脉取血测空腹血糖、血清总胆固醇（TC）、三酰甘油（TG）、高密度胆固醇（HDL-C）,颈椎脱臼处死后,摘取心脏、肝脏、肾脏,电子天平称湿重并计算其指数。结果：蛹虫草多糖可显著降低四氧嘧啶糖尿病小鼠血糖,治疗结束后TC、TG含量显著降低（P〈0.01）,各脏器指数与模型组比较有所增强。结论：蛹虫草多糖对四氧嘧啶糖尿病小鼠有降糖作用,对小鼠的免疫功能有一定的保护作用。     

维生素D对前列腺增生小鼠血清生化指标的影响研究

目的 通过观察维生素D对前列腺增生小鼠动物模型血清生化指标的影响,探讨不同剂量维生素D对前列腺增生动物模型的血清生化指标影响.方法 应用丙酸睾酮肌肉注射制造小鼠前列腺增生模型.随机分组,采用不同剂量的维生素D剂喂养4周后,检测小鼠血清电解质、肝肾功能、血脂等指标.结果 应用0.2、1.0和5.0 μg/kg·d~(-1)的各组小鼠检测结果显示:应用维生素D对前列腺增生小鼠的肾功能无明显负面影响;但是大剂量维生素D对血清谷草转氨酶(AST)有升高作用;中、大剂量维生素D可以升高血清钙离子浓度,对镁、磷无明显影响.结论 中、小剂量维生素D对小鼠前列腺增生模型的肝肾功能、电解质未发现明显负面影响,大剂量维生素D可能对血清钙离子浓度、AST有一定影响.     

扶正泄浊保肾汤对CRF大鼠血浆ET-1、Scr、BUN及肾组织病理的影响

目的：观察扶正泄浊保肾汤对慢性肾衰竭（CRF）大鼠血浆内皮素-1（ET-1）、血肌酐（Scr）、尿素氮（BUN）及肾组织病理的影响,探讨其作用机制.方法：采用5/6肾切除的方法制造CRF模型.将60只雄性SD大鼠随机分为6组：假手术组、模型组、尿毒清组及扶正泄浊保肾汤大、中、小剂量组;分别按一定比例予大、中、小剂量组大鼠灌胃,假手术组及模型组同时间予等体积的生理盐水灌胃.所得数据均采用（±s）表示,组间比较用t检验,采用SPSS 18.0进行统计学处理.结果：各治疗组与模型组间比较,血浆ET-1及Scr、BUN水平显著下降,差异有统计学意义（P＜0.05）,且肾脏病理改变较轻;大、中剂量组与小剂量、尿毒清组间差异有统计学意义（P＜0.05）;大、中剂量组间差异无统计学意义（P＞0.05）;小剂量组与尿毒清组间差异无统计学意义（P＞0.05）.结论：扶正泄浊保肾汤具有降低大鼠血清ET-1、Scr、BUN水平,减轻肾脏病理表现的作用.     

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.