Comparison between isoprenaline infusions and bolus injections to assess β-adrenoceptor function in man,with special reference to cardiac contractility and the influence of autonomic reflexes

The present study was performed to characterize cardiovascular responses to isoprenaline and the influence of autonomic reflexes on these reponses. Nine healthy volunteers received infusions and bolus injections of isoprenaline before and after ‘autonomic blockade’ produced by intravenous atropine 0.04 mg kg^-1 and clonidine 300 μg. Heart rate, blood pressures, systolic time intervals and various echocardiographic measures of cardiac contractility were registered. No significant differences in responsiveness to isoprenaline were seen when infusions were repeated on the same day without ‘autonomic blockade’. After ‘blockade’, Δ responses at 1 nmol 1^-1 isoprenaline (infusions) were increased for diastolic blood pressure and decreased for systolic blood pressure and stroke volume. Bolus injections of 2 μg isoprenaline caused enhanced Δ responses after ‘autonomic blockade’ of diastolic blood pressure, left ventricular diameter in systole, ventricular circumferential fibre shortening, mean posterior wall velocity (V_{mean pw}), stroke volume, systemic vascular resistance, electromechanical systole (QS₂) and pre-ejection period. Systolic blood pressure decreased, in contrast to a small increase without ‘blockade’. These findings are explained by differences in haemodynamic effects of isoprenaline and by the dependence of responses on reflexes when isoprenaline is administered in different ways. When heart rate was increased by bolus doses of atropine, in the presence of β-blockade (propranolol), pre-ejection period and left ventricular diameter in systole were unaffected, and V_{mean pw} and ventricular circumferential fibre shortening showed only small increases (compared with alterations induced by isoprenaline). However, left ventricular ejection time, QS₂ and ejection time (by echocardiography), were markedly dependent on heart rate alterations. Thus, pre-ejection period, left ventricular diameter in systole V_{mean pw} and ventricular circumferential fibre shortening are parameters which can be useful in order to evaluate cardiac β-adrenoceptor sensitivity in vivo in man.     

Real-time identification and archiving of micro-embolic Doppler signals using a knowledge-based DSP system

Identification of micro-emboli in the cerebral circulation using transcranial Doppler ultrasound provides valuable clinical information, but, currently, embolic signal detection and analysis are significantly limited because they mainly rely on costly off-line analysis by human experts. In this study, a reliable, high-resolution, real-time automated system for the detection and archiving of embolic signals was designed and implemented using expert system theory and modern DSP technology. Preliminary tests were conducted to evaluate the functions and the performance of the system using data from ten carotid endarterectomy patients and two normal volunteers. Using the widely accepted 7 dB threshold for human reliability and a human expert, majority-decision gold standard, the real-time system reached sensitivity and specificity of 93.6% and 99.3%, respectively, which were close to the results obtained by three human experts under ideal laboratory conditions (90.1% and 99.8%, 98.4% and 99.9%, 98.9 and 99.9%). The new system has the potential to be used either as a bedside monitoring and signal acquisition device, or as a laboratory investigation tool.     

Left ventricular function following withdrawal of chronic metoprolol treatment in patients with ischaemic heart disease. A double blind study

The effect on left ventricular function of a gradual withdrawalof chronic metoprolol treatment in postinfarction patients wasstudied. All patients were in a randomized double-blind post-infarctionstudy with metoprolol (M 100–200 mg daily; N=14) or placebo(P; N =18). After three years treatment the study medicationwas gradually withdrawn during one week. M-mode echocardiography,guided by concomitant cross-sectional recordings, were performedbefore, one and 12 weeks after the withdrawal. Treatment (i.e.M or P) had to be reinstituted in eight patients (5 M; 3P) becauseof the development of disabling symptoms during the follow-up.Heart rate was lower in patients treated with M (57±4)than with P (69±10) (p<0.01). One week after withdrawalof M, heart rate had increased to 77± 13(p<0.001),while patients on P showed no significant change. In order tominimize the influence of heart rate on the evaluation of timeintervals in the cardiac cycle, heart rate dependent correctionfactors were used. One week after M withdrawal there was a prolongationof the pre-ejection period (PEP) from 120±15 ms to 133±16ms (p< 0.01), mainly due to a prolongation of the intervalfor early isovolumetric contraction (Q Mc) from 87±10ms to 101±11 ms (N=11; p0.001). Simultaneously, valuesfor isovolumetric relaxation increased from 228±28msto 286±39 MS (n = 11; p0.001), starting from a somewhatlower value than P before withdrawal, reaching an insignificantlyhigher level and returning to the levels of P. During withdrawalof P stable values were encountered. Twelve weeks after withdrawal,there were no longer significant differences between M and Pgroups. In conclusion, after a one week gradual withdrawal ofM in patients with ischaemic heart disease, a transient increaseof both isovolumetric contraction and relaxation phases occur,suggesting depressed myocardial function, despite a transientrebound increase in heart rate.     

二维超声诊断胎儿脐带绕颈136例分析

目的 了解胎儿脐带绕颈时对胎儿安危及窘迫和缺氧的影响程度。方法 采用日本Aloka-630型超声诊断仪,孕妇孕周为28-42周。结果 二维超声诊断胎儿脐带绕颈136例,经分娩证实129例。符合率94.85%。结论 二维超声诊断与分娩后证实比较,超声是诊断脐带绕颈的可靠方法之一。为分娩方式提供依据。     

三房心的外科治疗——附4例报告

目的 探讨三房心的临床诊断和外科治疗方法。方法 总结1994年至2000年,4例三房心患施行外科手术的情况。结果 本组4例患畸形矫治满意,术后恢复好。结论 超声心动图对于三房心的诊断具有较高的价值;三房心是一种罕见的心脏畸形,多合并其他心内畸形,手术切除左房内隔膜并同时矫治其他心内畸形可获得满意的效果。     

大鼠磨牙三维有限元模型的建立

目的 :建立大鼠磨牙的三维有限元模型 ,探讨牙及牙周组织的应力分布状况。方法 :采用Sprague Dawley大鼠 2 0只 ,建立大鼠磨牙正畸移动的动物模型 ,制作大鼠上颌第一磨牙牙周连续切片 ;采用计算机技术 ,重建牙及牙周组织三维形态、结构 ,并建立其三维有限元模型。结果 :组织切片的应力分布显示牙周膜是一种存在于两种硬组织之间的软组织 ,有其特有的应力分布状态。结论 :本研究建立的正畸大鼠磨牙三维有限元模型是观察正畸牙移动过程中分析应力的一种简便、准确、可靠的模型及方法。     

三甲医院高层次卫技人才队伍建设发展现状及对策研究

通过对某三甲医院高层次卫技人才的规模、构成、引培和流失进行统计分析,了解医院高层次卫技人才队伍建设现状和流动变化规律,为制定和完善医院高层次卫技人才队伍建设策略提供证据参考。结果显示,该院高层次卫技人才规模、构成均得到有效改善,高层次卫技人才流失情况在可控范围内,但也面临着高层次卫技人才总量相对不足、流失人才中辞职占比较大等问题。未来要继续推动"人才强院"战略,创新人才引培考核机制,完善人才培养体系和计划,建立科学的测评体系以及健全绩效评价机制和薪酬分配制度。     

骨圈对椎弓根钉系统负载影响的三维有限元分析

目的：探讨单枚人体皮质骨圈(allograft fusion cage，AFC)斜植融合术中椎弓根钉系统受力分布，并对临床常见断钉原理进行分析，为临床应用提供理论依据。方法：采用二三维有限元方法(finite element method，FEM)，对放置及不放置AFC的脊柱Steffee钢板固定效果进行评估。结果：未放置AFC时Steffee钢板所受最大应力约为放置AFC状态下的4．8倍；椎弓根钉与螺帽交界处所受应力为最大，尤其上位螺钉与靠近椎体侧螺帽交界处是应力值最大点，未放置AFC时椎弓根钉最大应力点约为放置AFC状态下的5．0倍。结论：螺钉与钢板交界区是容易发生断钉的区域，尤其上位螺钉与靠近椎体侧螺帽交界处是最易断钉的部位；椎弓根钉系统放置AFC会明显增强融合节段稳定性，减少断钉等并发症。     

常压氧治疗胎儿-胎盘循环功能降低疗效的多普勒超声心动图观察

目的评价常压氧在胎儿-胎盘循环功能降低治疗中的疗效.方法应用超声心动图观察52例胎儿胎盘循环功能降低在常压氧治疗前后的变化情况并与45例普通吸氧组及41例未治疗组进行对照.结果52例胎盘循环功能降低胎儿中43倒常压氧治疗后胎盘循环功能恢复正常,有效率82.7%.明显高于对照组(P＜0.01).结论常压氧是治疗胎儿胎盘循环功能降低安全、有效的方法.     

运动强度对幼龄大鼠海马VEGF及其受体Flk-1 mRNA表达的影响

为了研究不同强度跑台运动对5周龄大鼠海马表达血管内皮生长因子(vascular endothelial growth factor,VEGF)和胎肝激酶-1(fetal liver kinase-1,Flk-1)受体mRNA水平的影响,5周龄雄性SD大鼠被随机分为对照组和小强度、中等强度、大强度3个跑台运动组,并通过定量real-time PCR技术,观察不同强度跑台运动1周后大鼠海马内VEGF和Flk-1mRNA表达的影响。采用3-磷酸甘油醛脱氢酶(glyceraldehyde-3-phosphate dehydrogenase,GAPDH)作为管家基因内参,以样品中所测得的VEGF和Flk-1基因拷贝数除以该样品中内参基因拷贝数进行校正后,各组动物海马内VEGF mRNA相对水平分别是:对照组为2740±2229,小强度运动组为3599±2386(P<0.05),中等强度运动组为1654±1136,大强度运动组为1572±1071。各组动物海马内Flk-1mR-NA相对水平分别是:对照组为147±47,小强度运动组为281±182(P<0.01),中等强度运动组为208±100;大强度运动组为54±31。以上结果提示,大鼠海马内VEGF和Flk-1mRNA的表达受运动的调节,且与运动强度有关。小强度跑台运动可对VEGF和Flk-1mRNA的表达产生促进作用,而大强度运动则不影响VEGF和Flk-1mRNA的表达。