18F-FDG PET在肾上腺病变定性诊断中的应用

我们对CT发现的肾上腺肿瘤行^18F-FDG PET全身显像，并与手术病理进行对比分析，评估PET显像在肾上腺肿瘤定性诊断中的价值。现报告如下。     

肾上腺肿瘤44例分析

目的提高对肾上腺肿瘤的诊断水平。方法肾上腺肿瘤共44例，11例行18F-氟脱氧葡萄糖（18F—FDG）PET／CT、CT及MRI检查，余行CT和18F—FDG PET／CT检查，所有病例均行高血压试验和24h尿肾上腺素2项检测，术后病理或临床随访确诊。结果18F—FDG PET／CT对肿瘤良恶性诊断的敏感性、特异性分别为93．7％、100％，肿瘤诊断准确性为82．9％。CT分别为87．5％、96．4％和77．3％。MRI的肿瘤诊断准确性为81．8％。血浆醛固酮最高浓度在各肿瘤中差异无统计学意义（P〉0．05）。髓质肿瘤与其他肾上腺肿瘤相比尿去甲基肾上腺素（NMN）、尿甲氧基肾上腺素（MN）、收缩压、舒张压差异均有统计学意义（P〈0．05）。以3．1作为SUV临界值，得出PET／CT区分肿瘤良恶性敏感性和特异性最佳，分别为100％和96．2％。结论18F—FDGPET／CT在诊断肾上腺肿瘤良恶性上优于MRI和CT。高血压和尿NMN／MN成3倍以上升高对嗜铬细胞瘤的诊断意义重大。髓脂瘤、囊肿和嗜铬细胞瘤运用CT或MRI能较好诊断，非功能性和皮质肿瘤以PET／CT诊断为佳。     

18F-脱氧葡萄糖正电子发射体层显像在食管癌患者中的应用

目的探讨^18F-脱氧葡萄糖正电子发射体层显像（^18F-FDG—PET）检查在食管癌患者诊断、治疗中的应用价值。方法1999年10月～2005年12月，对52例食管癌患者行全身^18F-FDG—PET检查，其中15例在检查前未经任何治疗，37例为综合治疗后复查。采用目测法结合半定量分析法判读^18F-FDG—PET检查结果，并与病理检查和随访结果进行对比。结果在15例行^18F-FDG—PET检查前未经任何治疗的食管癌患者中，11例患者（T2～T4）原发肿瘤显影，4例T1原发肿瘤未显影；^18F-FDG—PET检查定性诊断的灵敏度为73．3％（11／15）。8例手术治疗的患者切除纵隔和腹腔直径〉1cm的淋巴结16处，术前6处经^18F-FDG—PET检查定性为恶性，其中5处为转移淋巴结，1处为淋巴结结核；7例患者经^18F-FDG—PET检查发现有远处器官转移，不适合手术治疗。37例经综合治疗后患者复查^18F-FDG—PET，发现34例有肿瘤复发和／或转移。结论^18F-FDG—PET检查对食管癌原发肿瘤和局部淋巴结转移的定性诊断价值有限，但对发现远处器官转移和判断治疗效果有较大的帮助，^18F-FDG—PET检查需结合其他辅助检查才能发挥其优势。     

18F脱氧葡萄糖-正电子发射体层显像在贲门胃底恶性肿瘤患者中应用价值的探讨

目的探讨^18F脱氧葡萄糖（FDG）-正电子发射体层显像（PET）在贲门胃底恶性肿瘤患者诊断治疗中的应用价值。方法1999年4月—2005年4月间对57例贲门胃底恶性肿瘤患者行全身FDG—PET检查,其中29例在PET检查前未经任何治疗,另外28例为综合治疗后复查。采用目测法结合半定量分析判读PET结果,与病理及随访结果对照。结果29例FDG—PET检查前未经任何治疗的患者中,25例T2～T4期原发肿瘤显影,4例T1期原发肿瘤未显影,FDG—PET定性诊断灵敏度86％（25／29）;其中24例根治性手术治疗的患者切除胸、腹腔直径〉1．0cm的淋巴结40处,FDG—PET正确定性诊断28处为恶性及12处为良性淋巴结;5例患者FDG—PET发现有远隔脏器转移未行根治性手术。28例综合治疗后复查FDG—PET的患者中,FDG—PET发现22例存在复发或转移。结论FDG—PET检查对于贲门胃底恶性肿瘤的定性、TNM分期及判断治疗效果有帮助,但必须结合其他检查才能发挥优势。     

~(18)F-FDG PET/CT显像在泌尿系肿瘤中的临床应用

18F-脱氧葡萄糖正电子发射断层显像/CT技术(18F-FDG PET/CT)显像在多种恶性肿瘤的诊断、鉴别诊断、分期、随访监测、疗效与预后评估中起重要作用,但是其在泌尿系肿瘤中却因为18F-FDG由泌尿系统排泄而影响观察,肾细胞癌与前列腺癌原发肿瘤病灶则表现为少摄取或不摄取18 F-FDG而呈现假阴性表现。本文旨在探讨18F-FDG PET/CT显像在泌尿系统肿瘤中的潜在临床应用价值。     

^18F-FDG代谢显像对肿瘤骨骼侵犯的诊断价值

目的探讨氟代2-脱氧葡萄糖（^18F—FDG）双探头符合线路骨代谢显像（DHCI）及^99m锝-亚甲基二膦酸盐（^99mTc—MDP）骨骼显像对肿瘤骨骼侵犯的诊断价值。方法21例不明原因腰背部疼痛和35例CT或MRI发现骨骼病变疑似恶性肿瘤侵犯共56例患者行^99MTc—MDP骨骼显像及^18F—FDGDHCI,最终结果与病理以及其它影像学结果作对照。并将^99mTc—MDP骨骼显像和^18F—FDGDHCI做对比研究。结果56例中确诊为恶性肿瘤49例（病灶193个）,其中成骨性病灶135个,溶骨性病灶58个。^99mTc—MDP骨骼显像对肿瘤骨骼侵犯诊断的灵敏度、特异性、准确率分别为89．5％,14．2％和81．3％,阳性预报价值为97．8％,阴性预报价值为89．5％。^18F—FDGDHCI对肿瘤骨骼侵犯诊断的灵敏度、特异性、准确率分别为98．3％,100％和98．4％,阳性预报价值为100％,阴性预报价值为87．5％。两者对骨骼病灶的诊断效能相比,^18F-FDGDHCI高于^99mTe—MDP骨骼显像,差异有显著性（x^2=9．77,P〈0．05）。结论^18F—FDGDHCI和^99mTc—MDP骨骼显像对原发骨骼恶性肿瘤及骨骼转移灶均有较好的诊断价值,但前者对恶性肿瘤骨骼侵犯的灵敏度、准确率、特异性均高于^99mTc—MDP骨骼显像。^18F—FDGDHCI除可探测骨骼转移灶外对原发病灶也有很好的探测价值,并较准确地确定恶性肿瘤临床分期。     

18F-FDG PET显像在大肠癌诊治中的应用

目的 介绍18F-氟代脱氧葡萄糖正电子发射型断层显像(18F-FDG PET)在大肠癌诊治中使用的最新进展。方法 对近几年来国外关于18F-FDG PET显像对大肠癌诊治研究进展进行分析和总结。结果 18F-FDGPET显像对早期诊断大肠癌复发、转移及大肠癌的分期均优于CT及MRI检查。结论 18F—FDG PET显像可以作为诊断大肠癌的一种重要检查手段，并有助于治疗方案的选择。     

18F-FDG hPET/CT显像诊断结直肠癌术后复发转移

目的 评价^18F-FDG hPET／CT代谢显像对结直肠癌患者术后复发转移的诊断价值。方法 对81例结直肠癌术后临床可疑肿瘤复发或转移的患者采用GEHAWKEYE符合线路SPECT进行^18F-FDG显像，获得经X线衰减校正后的三维断层图像，由计算机完成各断层图像的融合，以目测法进行诊断分析，并与CT、病理学检查、临床随访作出的最后诊断进行对比。结果 ^18F-FDG hPET／CT代谢显像对结直肠癌术后复发、转移诊断的灵敏度为93％（57／61），特异性为80％（16／20），阳性预测率为93％（57／61），阴性预测率为80％（16／20）；而常规CT对结直肠癌术后复发转移诊断的灵敏度、特异性、阳性预测值、阴性预测值分别为67％（37／55）、73％（19／26）、84％（37／44）、51％（19／37）；^18F-FDG hPET／CT代谢显像共检出病灶126个，65例相同视野hPET／CT代谢显像与诊断CT常规影像检查复发转移病灶检出数分别为91个和46个。结论 ^18F-FDG hPET／CT显像对结直肠癌术后复发转移的诊断价值优于CT；通过与同机定位CT图像融合可有效地对病变进行定性定位。     

18F-FDG PET/CT评价非霍奇金淋巴瘤骨髓浸润

目的探讨^18F-FDG PET／CT评价非霍奇金淋巴瘤（NHL）骨髓浸润的临床应用价值,并与骨髓活检（BMB）及流式细胞分析（FCM）进行比较。方法回顾性分析89例经病理证实且未经治疗的NHL患者^18F-FDG PET／CT资料,其中侵袭性NHL76例,惰性NHL13例。所有患者均在^18F-FDG PET／CT检查2周内接受BMB及FCM,对^18F-FDG PET／CT显示骨髓局灶性^18F—FDG摄取增高而BMB及FCM阴性患者,根据PET／CT所示骨髓异常部位再次行BMB确定骨髓是否受累。结果89例NHL患者中,根据BMB、FCM及PET／CT引导下再次BMB结果,共检出骨髓浸润26例,检出率为29．21％（26／89）,PET／CT检出率为21．35％（19／89）。PET／CT诊断骨髓浸润的灵敏度为73．08％（19／26）,特异度为96．83％（61／63）,准确率为89．89％（80／89）,阳性预测值为90．48％（19／21）,阴性预测值为89．71％（61／68）。BMB及FCM检出率均为19．10％（17／89）,PET／CT较BMB、FCM骨髓浸润检出率稍高,但差异无统计学意义（P〉0．05）。将PET／CT、FCM及BMB三种方法联合诊断骨髓浸润,其检出率高于其中任意一种方法（P〈0．05）。PET／CT对侵袭性NHL骨髓浸润的检出率22．37％（17／76）高于对惰性NHL骨髓浸润的检出率15．38％（2／13,P〈0．06）。结论^18F-FDG PET／CT在诊断NHL骨髓浸润中有较高的应用价值。对局灶性骨髓浸润患者,PET／CT有助于引导BMB部位,提高骨髓浸润的检出率。PET／CT未检出骨髓浸润的惰性NHL患者,应进一步行BMB及FCM检查。推荐PET／CT、FCM及BMB三种方法联合应用判断NHL骨髓浸润,从而更准确地进行分期、治疗及判断预后。     

18F-脱氧葡萄糖正电子发射计算机断层显像CT检查在前列腺癌诊断和分期中的应用价值

目的 评价18F-脱氧葡萄糖(18F-FDG)正电子发射计算机断层显像CT检查(PET/CT)在前列腺癌诊断和分期中的应用价值.方法 经手术或穿刺活检病理证实为前列腺癌患者40例,年龄52 ～ 78岁,平均67岁.其中T24例,T316例,T420例.行18F-FDG PET/CT及99Tcm-MDPECT骨显像检查,统计PET/CT显像对前列腺癌原发灶、淋巴结转移及骨转移诊断的敏感性,对比分析PET/CT显像及99Tcm-MDPECT骨显像对骨转移的诊断效果.结果 40例患者中,18F-FDG PET/CT检查显示前列腺局部结节状放射性浓聚17例,对原发灶诊断敏感性为43％.17例淋巴结转移患者中CT检查发现8例,18F-FDG PET/CT检查发现15例,诊断敏感性为88％,其中5例患者因PET/CT检查改变了临床分期以及治疗方案.18F-FDG PET/CT对骨转移诊断的敏感性与99Tcm-MDP骨显像相近,但特异性(95％)和准确率(96％)均明显高于99Tcm-MDP骨显像,其中6例患者因PET/CT检查改变了临床分期,2例改变了治疗方案.结论 18F-FDG PET/CT对前列腺癌淋巴结转移和骨转移有较高诊断价值,对前列腺的分期具有特殊优势,可为临床医生制定治疗方案提供可靠依据.     

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.