Recent trends in studies of the etiology of hypertension: Renal mechanism of blood pressure regulation

The kidney plays an important role in the control of systemic blood pressure by regulating the composition of body fluid and electrolyte and by producing and releasing various vasoactive substances such as renin-angiotensin and prostaglandins(PGs). The kidney possesses an intrinsic mechanism called 'pressure-natriuresis' in which an increase in perfusion pressure promotes natriuresis. According to this mechanism, hypertension can be classified as salt-sensitive or non-salt-sensitive based on the response to dietary sodium loading. Thus, a shift of the curve to the right and a decrease in the slope are the two basic abnormalities seen in the pressure-natriuresis relationship in hypertension, with each representing a different pathophysiology. In non-salt-sensitive essential hypertension, glomerular capillary pressure is within the normal range due to elevated preglomerular resistance, while it is elevated in salt-sensitive hypertension. Such differences may be reflected in the rate of progression of renal dysfunction as well as renal pathology. Finally, the mechanism responsible for the altered renal microcirculation involves dysregulation of intrinsic mechanisms(myogenic responses and tubuloglomerular feedback) as well as various local factors, in particular, angiotensin II, nitric oxide, and oxidative stress.     

单次运动对轻度高血压患者血压、自主神经功能和氧化应激的影响

目的:探索轻度高血压患者单次运动后体内自主神经功能和氧化应激的变化,及其与血压变化的关系。方法:选取29例经过明确诊断的轻度原发性高血压患者。所有受试者进行心肺运动试验检测其峰值摄氧量VO_2peak后,被安排以60%VO_2peak进行40min踏车运动。运动前及运动后2h内,通过心脏超声检测左心室血流动力学指标,并计算体循环血管阻力(SVR);肘前静脉采血,检测脂质过氧化物(LOOH);用心电动态监测仪监测受试者的心率变异性(HRV)指标。结果:与运动前相比,运动后受试者平均动脉压(MABP)降低(P0.05),SVR降低(P0.05),LOOH浓度升高(P0.05)。运动后心率变异性低频指标(LF)、低/高频比值(LF/HF)低于运动前(P0.05),高频指标(HF)、正常心搏间期标准差高于运动前(P0.05)。结论:单次运动后血压下降,同时体循环血管阻力降低、自主神经功能改善、氧化应激增强。提示单次运动后血压的下降与体循环血管阻力降低、自主神经功能改善有关,而与氧化应激无关。     

阻塞性睡眠呼吸暂停综合征伴血压升高患者血压、血糖及血脂控制情况

目的调查阻塞性睡眠呼吸暂停综合征(OSAS)伴血压升高患者在不同状态下血压、血糖、血脂控制情况。方法对57例OSAS合并高血压或正常高值患者的血压、血糖、血脂控制水平进行调查和随访,并与患者住院时的血压、血糖、血脂数值进行比较分析。同时对行腭咽成形术治疗的高血压患者手术前后的血压控制情况进行分析。结果 (1)高血压组调查时收缩压(SBP),舒张压(DBP)与住院时SBP及DBP相比明显降低(P<0.05);空腹血糖(FBG)、总胆固醇(TC)、三酰甘油(TG)调查时与住院时相比无差异(P>0.05)。(2)正常高值组调查时SBP、DBP、FBG、TC均较住院时增高(P<0.05);调查时TG与住院时相比无差异(P>0.05)。(3)合并高血压且行OSAS手术治疗的患者手术后SBP、DBP与手术前SBP、DBP比较明显降低(P<0.05)。结论 OSAS合并高血压患者出院后血压得到控制,但血糖和血脂有增高趋势;血压正常高值患者出院后血压、血糖、血脂均有增高趋势;OSAS伴高血压患者手术后血压水平得到改善。     

原发性高血压患者血压变异与心血管事件的相关性研究

目的探讨原发性高血压患者血压变异与心血管事件的关系。方法选择110例原发性高血压患者作为研究对象,根据24 h收缩压变异性的总变异系数(BPsVC)将患者分为高BPsVC组及低BPsVC组。比较两组患者心血管事件发生率、血压、心室肥厚发生率、颈动脉粥样硬化及肾脏改变。结果高BPsVC组与低BPsVC组心血管事件发生率分别为44.2%和27.6%(P=0.007);高BPsVC组24 h平均收缩压、24 h平均舒张压和左室肥厚发生率显著高于低BPsVC组(P<0.05);高BPsVC组颈动脉内膜-中膜厚度(IMT)、尿素氮、肌酐以及尿微量白蛋白显著高于低BPsVC组(P<0.05)。结论高BPsVC与高血压患者的心血管事件发生率及靶器官损害密切相关。     

The renin-angiotensin system: renal actions and blood pressure regulation

The RAS is part of an extremely powerful feedback system for long-term control of blood pressure and volume homeostasis. Disturbances that tend to lower blood pressure, such as heart failure, cirrhosis, and peripheral vasodilation, cause sodium and water retention until blood pressure returns to normal due, in large part, to the combined actions of ANGII and reduced arterial pressure. In response to increased sodium intake, decreased ANGII formation greatly amplifies the effectiveness of pressure natriuresis, thereby preventing large increases in body fluid volumes and blood pressure. In circumstances in which the RAS is inappropriately activated, the sodium retaining effects of ANGII necessitate increased blood pressure to maintain sodium balance via pressure natriuresis. Because the RAS is so powerful in regulating blood pressure, blockade of the system with ACE inhibitors offers a powerful therapeutic tool in diseases such as hypertension and congestive heart failure. The control of sodium excretion and blood pressure by ANGII is exerted through multiple intrarenal as well as extrarenal effects, including stimulation of aldosterone secretion, which can influence renal excretion. Current evidence suggests that the intrarenal effects of ANGII are quantitatively more important than those mediated by aldosterone in controlling blood pressure and renal excretion. The most important intrarenal effects of ANGII include efferent arteriolar constriction as well as direct effects on sodium transport. The constrictor effect on efferent arterioles also is important in preventing reductions in GFR in circumstances associated with impaired renal perfusion. Therefore blockade of ANGII formation in circumstances such as renal artery stenosis may caused marked reductions in GFR. However, in many patients efferent arteriolar vasodilation caused by ANGII blockade may not lower GFR markedly because of other autoregulatory mechanisms that compensate by causing parallel reductions in afferent arteriolar resistance. In these individuals, chronic ACE inhibition may prove to be beneficial in slowing the progression of renal disease because a reduction in glomerular hydrostatic pressure may help to prevent glomerular damage.     

Blood pressure biofeedback exerts intermediate-term effects on blood pressure and pressure reactivity in individuals with mild hypertension: a randomized controlled study

OBJECTIVE: This randomized controlled study examined whether a 4-week blood pressure (BP) biofeedback program can reduce BP and BP reactivity to stress in participants with mild hypertension. METHODS: Participants in the active biofeedback group (n=20) were trained in 4 weekly laboratory sessions to self-regulate their BP with continuous BP feedback signals, whereas participants in the sham biofeedback group (n=18) were told to manipulate their BP without feedback signals. BP, skin temperature, skin conductance, BP reactivity to stress, body weight, and state anxiety were assessed before training and repeated at the eighth week after the training. RESULTS: The decreases in systolic (12.6 +/- 8.8 versus 4.1 +/- 5.7) and mean BP (8.2 +/- 6.9 versus 3.3 +/- 4.9) from baseline at week 12 follow-up were significantly greater in the active biofeedback group compared with the sham biofeedback group (p=0.001 and 0.017, respectively). Results from analysis of covariance with the follow-up systolic blood pressure (SBP) (or mean arterial pressure [MAP]) as the dependent variable, baseline SBP (or MAP) as the covariate, and group as the independent variable showed that biofeedback training effectively lowered SBP and MAP (p=0.013 and 0.026, respectively). The pre-to-post differences in skin conductance and SBP reactivity were statistically significant for the biofeedback group (p=0.005 and 0.01, respectively), but not for the control group. For the sample as a whole and for the biofeedback group, the state anxiety score and body weight remained unchanged. CONCLUSIONS: BP biofeedback exerts a specific treatment effect in reducing BP in individuals with mild hypertension, possibly through reducing pressor reactivity to stress.     

Cardiac contractility,central haemodynamics and blood pressure regulation during semistarvation

Eight obese patients were studied before and after 2 weeks of treatment by a very-low-calorie diet (VLCD). Cardiac output and central blood volume (pulmonary blood volume and left atrial volume) were determined by indicator dilution (¹²⁵I-albumin) and radionuclide angiocardiography (first pass and equilibrium technique by [⁹⁹Tc^m]red blood cells). Cardiac output decreased concomitantly with the reduction in oxygen uptake as the calculated systemic arteriovenous difference of oxygen was unaltered. There were no significant decreases in left ventricular contractility indices, i.e. the ejection fraction, the peak ejection rate and changes in end-systolic volume. Also the diastolic function evaluated by the peak filling rate remained normal. Furthermore, no sign of backward failure could be demonstrated since the central blood volume was not significantly increased. Both systolic and diastolic blood pressure (BP) declined. The fall in BP was caused by the reduction in cardiac output as the total peripheral resistance was unchanged. Finally, the decline in total blood volume was not significant. These findings together with a reduction in heart rate indicated that a reduced sympathetic tone via increased capacitance of the venous bed was the main operator of a reduced venous return. Thus, the haemodynamic alterations in obese patients during short-term semistarvation may be caused by the fall in oxygen uptake and produced mainly by changes in the sympathetic tone.     

Correlation between neurologic defect and blood pressure regulation in acute phase of ischemic stroke caused by hypertension

Background：Variousmanagementswereemployedforacutephaseofischemicstrokecausedbyhypertension．Regulationofhy－pertensioninacutephasewascloselyassociatedwithprognosisofis－chemicstroke．Objective：Tostudyrelationshipbetweenneurologicfunctiondefectandbloodpressureregulationinacutephaseofischemicstrokecausedbyhypertension．Unit：NervousInternalMedicineDepartmentoftheFirstPeople＇sHospitalofYunnan．Subject：２８subjectswererecruitedwithin２years,including１７males,１１females（agerangingfrom…     

OSAHS伴血压异常患者经鼻Auto-CPAP治疗对血压改变情况的研究

目的:研究OSAHS伴高血压患者,经鼻auto-CPAP治疗对其血压改变的情况。资料与方法:30例OSAHS伴高血压患者,其中包括已确诊高血压患者9例(维持既往口服降压药物治疗方案不变)及本次研究新发现高血压患者21例(既往无口服常规降压药物,暂不给予口服药物治疗)。给予患者每晚有效auto-CPAP(RESmart GII,北京怡和嘉业医疗科技有限公司)连续治疗,分别于治疗前及治疗第1、2、4周复查24 h ABP,比较治疗前后患者血压改变情况。结果:1)30例患者auto-CPAP治疗1周后,24 h ABP各时段血压均较治疗前明显降低,24 h SBP/DBP降低5.73/3.43 mm Hg,d SBP/DBP降低5.40/3.53 mmHg,n SBP/DBP降低7.03/2.73 mm Hg。2)9例既往高血压患者与21例本次研究新发现高血压患者相比,1周治疗后仅n SBP及n DBP的变化有统计学意义。3)部分患者延长治疗至2、4周,仅治疗1周与2周d SBP的变化有统计学意义。结论:1)auto-CPAP治疗OSAHS有助于患者血压的控制与改善。2)OSAHS伴高血压患者经atuo-CPAP治疗(1、2、4周)后,血压的降低主要出现在第1周的治疗上,临床上建议以第1周auto-CPAP治疗结束后的24 h ABP数据作为参考,这对于OSAHS伴有高血压患者的药物干预或调整具有一定的临床意义。3)在auto-CPAP对OSAHS伴高血压患者的治疗中,既往口服降压药物比无口服降压药物患者的夜间血压下降幅度更大。     

Nifedipine retard in the treatment of hypertension. A study using ambulatory blood pressure recordings

The subjects were 24 patients, aged 37 to 66 years, with mild to moderate hypertension, treated with nifedipine retard (mean dose, 47 mg daily) for 7 to 16 weeks. The mean 24-hour ambulatory blood pressure (BP) declined significantly from 158/101 before treatment to 136/87 mmHg after treatment. Daytime BP declined from 160/101 to 133/86 mmHg and nighttime BP from 152/98 to 132/85 mmHg; the diurnal variation in diastolic BP was lost during treatment with nifedipine. The consecutive hourly BPs were all significantly lower after treatment. BPs in response to physiologic tests were significantly reduced after treatment. Heart rate increased significantly during treatment. Side effects (palpitations, pedal edema, and flushing of the face) were reported by four patients. It is concluded that nifedipine retard is safe and effective in the treatment of mild to moderate hypertension.     

Resting and reactive blood pressure. Predictors of ambulatory blood pressure in older adults with hypertension

The study examined whether reactive change scores from a short blood pressure (BP) reactivity protocol, resting BP, or resting pulse pressure (PP) would be predictors of 24-hour ambulatory BP and BP load in cardiac patients. The study used a single-group design, with both an experimental clinical component and an observational field component. Both components used repeated measurement methods. The study population consisted of 45 adult patients with a mean age of 64.6 +/- 8.5 years who were diagnosed with cardiac disease in a cardiac rehabilitation program and who were taking anti-hypertensive medication. Blood pressure reactivity was operationalized with a speech protocol. During the speech protocol, BP was measured with an automatic device (Dinamap) while patients talked about their health and about their usual day. Twenty-four-hour ambulatory BP measurement followed the speech protocol. Resting systolic BP and resting PP were significant predictors of 24-hour ambulatory systolic BP, and resting systolic BP was a significant predictor of systolic BP load. No predictors were significant of 24-hour diastolic BP or diastolic BP load. Initial resting BP and PP may be used in clinical settings to assess hypertension management. Future studies are necessary to confirm the ability of resting BP to predict ambulatory BP and BP load in older adults who are medicated and hypertensive.     

康森降压仪治疗原发性高血压的临床与动物模型研究

目的:观察康森降压仪对原发性高血压患者的作用及机理研究。方法 :将耳夹经电极片对准耳背降压沟 ,分别夹于双耳的穴位 ,频率为每间隔(4±1)s的断续波 ,和大鼠分组实验观察。结果 :109例原发性高血压患者总有效率86.2 %。结论 :临床与实验证明康森降压仪确有良好的降压作用