Mechanisms underlying the impairment in orthostatic tolerance after nocturnal recumbency in patients with autonomic failure.

In the present study, we have assessed in patients with neurogenic orthostatic hypotension the haemodynamics underlying the reduced tolerance to standing after prolonged recumbency at night. In 10 patients with neurogenic orthostatic hypotension (age 33-68 years), of which seven were being treated with fludrocortisone and/or sleeping in the 12 degrees head-up tilt position, 24 h continuous non-invasive finger blood pressure was recorded by a Portapres device. Beat-to-beat blood pressure, heart rate, stroke volume, cardiac output and total peripheral vascular resistance obtained by pulse contour analysis were assessed during 5 min of standing in the evening (at 22.30 hours) and in the morning (at 06.30 hours). On average, the inverse of the normal 24 h blood pressure profile was found, with a large diversity in blood pressure profiles among patients. Supine blood pressure values were similar, but standing blood pressure values were lower in the morning than in the evening (P<0.01). This resulted from larger falls in stroke volume and cardiac output upon standing in the morning compared with the evening, while total peripheral resistance did not change. There was no relationship between the decrease in body weight during the night (mean 0.9 kg; range 0.2-1.6 kg) and the evening-morning difference in standing blood pressure. We conclude that, in patients with neurogenic orthostatic hypotension, the impaired tolerance to standing in the morning is due to larger falls in stroke volume and cardiac output. Not only nocturnal polyuria, but also a redistribution of body fluid, are likely mechanisms underlying the pronounced decreases in stroke volume and cardiac output after prolonged recumbency at night.     

Hemodynamics in diabetic orthostatic hypotension.

Hemodynamic variables (blood pressure, cardiac output, heart rate, plasma volume, splanchnic blood flow, and peripheral subcutaneous blood flow) and plasma concentrations of norepinephrine, epinephrine, and renin were measured in the supine position and after 30 min of quiet standing. This was done in normal subjects (n = 7) and in juvenile-onset diabetic patients without neuropathy (n = 8), with slight neuropathy (decreased beat-to-beat variation in heart rate during hyperventilation) (n = 8), and with severe neuropathy including orthostatic hypotension (n = 7). Blood pressure decreased precipitously in the standing position in the diabetics with orthostatic hypotension, whereas moderate decreases were found in the other three groups. Upon standing, heart rate rose and cardiac output and plasma volume decreased similarly in the four groups. The increases in total peripheral resistance, splanchnic vascular resistance and subcutaneous vascular resistance were all significantly lower (P less than 0.025) in the patients with orthostatic hypotension compared with the other three groups. The increase in plasma norepinephrine concentrations in the patients with orthostatic hypotension was significantly lower (P less than 0.025) than in the patients without neuropathy, whereas plasma renin responses to standing were similar in the four groups. We conclude that in diabetic hypoadrenergic orthostatic hypotension the basic pathophysiological defect is lack of ability to increase vascular resistance, probably due to impaired sympathetic activity in the autonomic nerves innervating resistance vessels; cardiac output and plasma volume responses to standing are similar to those found in normal subjects and in diabetics without neuropathy.     

Plasma catecholamine responses to change of posture in alcoholics during withdrawal and after continued abstinence from alcohol

Plasma catecholamine, blood pressure and heart rate responses to standing were measured in ten alcoholics during withdrawal, ten alcoholics after 2-7 weeks of abstinence from alcohol, six abstinent alcoholics with orthostatic hypotension and ten normal control subjects. Withdrawing alcoholics had supine and standing heart rates and plasma noradrenaline and adrenaline concentrations that were higher than in abstinent alcoholics or control subjects. Supine blood pressures were also higher in withdrawing alcoholics than in abstinent alcoholics or control subjects, but on standing blood pressures in withdrawing alcoholics fell, four patients having a fall of more than 30/5 mmHg. Abstinent alcoholics without orthostatic hypotension had higher basal and standing concentrations of noradrenaline than control subjects but normal heart rates and adrenaline concentrations. Abstinent alcoholics with orthostatic hypotension showed a wide range of basal plasma noradrenaline concentrations and were found to have variable plasma noradrenaline responses to standing, three subjects having normal responses and three subjects having no or little increase in plasma noradrenaline on standing. It is concluded that alcohol withdrawal is associated with increased sympathetic nervous activity, as reflected by raised supine and standing plasma concentrations of catecholamines, and that even after 2-7 weeks of abstinence from alcohol plasma noradrenaline concentrations may be higher than in control subjects. Despite increased sympathetic nervous responses to standing, alcoholics during withdrawal have impaired blood pressure control and some may exhibit orthostatic hypotension. Orthostatic hypotension may also be observed in alcoholics during continuing abstinence from alcohol; in some of these patients failure of reflex noradrenaline release in response to standing may contribute to orthostatic hypotension.     

Do elderly patients with an excessive fall in blood pressure on standing have evidence of autonomic failure?

1. Blood pressure, heart rate and plasma catecholamine responses were examined in two groups of elderly subjects distinguished by blood pressure responses to standing. Subjects in the control group showed a fall of less than 15 mmHg in systolic blood pressure on standing; subjects in the orthostatic hypotension group had falls of more than 20 mmHg systolic and 10 mmHg diastolic blood pressure on standing. 2. The heart pressure response on standing showed no significant difference between the two groups. 3. The orthostatic hypotension patients had lower plasma noradrenaline concentrations than the control patients (P less than 0.01) in the supine position, but during 10 min standing there was no significant difference in noradrenaline levels between the groups, and the percentage increase of noradrenaline levels in the orthostatic hypotension group was greater (P less than 0.05) than in the control group. 4. In the supine position, diastolic blood pressure was higher (P less than 0.05) in the orthostatic hypotension group than in the control group. 5. We conclude that impairment of baroreceptor function is not involved in most cases of orthostatic hypotension in the elderly, nor is there reduction of sympathetic nervous activity. We suggest that mechanical changes or adrenoreceptor dysfunction are more likely to be important factors in orthostatic hypotension in the elderly.     

Abnormal orthostatic changes in blood pressure and heart rate in subjects with intact sympathetic nervous function: evidence for excessive venous pooling

The normal ranges of orthostatic changes in blood pressure and heart rate have been defined in 92 individuals aged 18 to 64 years. In 34 individuals whose symptoms (especially orthostatic light-headedness) suggested cerebral ischemia, but in whom none of the known causes of orthostatic hypotension could be identified, we have found one or more of five theoretically possible orthostatic circulatory derangements: systolic hypotension, diastolic hypotension, diastolic hypertension, excessive narrowing of the pulse pressure, and tachycardia after standing for at least 3 minutes. The orthostatic disorders of blood pressure and heart rate identified in the 34 patients were significantly reduced, almost always into the normal range, by external pressure of 45 to 50 mm Hg applied through an inflatable pressure suit. After labeling with sodium pertechnetate Tc 99m and reinjecting the erythrocytes contained in 3 to 6 ml blood, external gamma counting over a fixed site in the calf, both in the recumbent and in the standing posture, showed excessive gravitational pooling of blood in the legs of five patients with orthostatic diastolic hypertension, of four with orthostatic narrowing of the pulse pressure, and of 10 with orthostatic tachycardia alone. Plasma norepinephrine concentrations were usually normal in recumbency and elevated above normal limits during standing for 15 to 30 minutes in the 18 patients so observed. Red cell mass, plasma volume, and circulating blood volume were subnormal in more than half the seven patients in whom these measurements were made. We conclude that most of the patients with idiopathic sympathicotonic abnormalities of orthostatic blood pressure control have a venous pooling syndrome often aggravated by hypovolemia, the cause(s) of which remains to be determined.     

斜床站立治疗颈髓损伤后体位性低血压的临床观察

目的 观察斜床站立对颈髓损伤后体位性低血压的治疗作用。方法 将36例颈髓损伤患者随机分为斜床组和常规组，在康复治疗过程中每日监测卧立位血压，治疗前后评定脊髓功能。结果 两组治疗后感觉及运动功能均有显著改善，但两组治疗后脊髓功能评分无统计学差异。36例颈髓损伤患者有27例（75％）出现体位性低血压，其中完全性脊髓损伤患者均出现体位性低血压。治疗后完全性脊髓损伤所致的体位性低血压两组均无明显改善，不完全性脊髓损伤斜床组血压均较治疗前显著改善，卧立位血压差值减少（P＜0．05）。与常规组相比较，斜床组治疗后血压改善（P＜0．05）。结论 颈髓损伤可出现体位性低血压，其中完全性颈髓损伤均不同程度出现体位性低血压。斜床站立可改善不完全性脊髓损伤民致的体位性低血压。     

Evaluation and management of orthostatic hypotension

Orthostatic hypotension is defined as a decrease in systolic blood pressure of 20 mm Hg or a decrease in diastolic blood pressure of 10 mm Hg within three minutes of standing when compared with blood pressure from the sitting or supine position. It results from an inadequate physiologic response to postural changes in blood pressure. Orthostatic hypotension may be acute or chronic, as well as symptomatic or asymptomatic. Common symptoms include dizziness, lightheadedness, blurred vision, weakness, fatigue, nausea, palpitations, and headache. Less common symptoms include syncope, dyspnea, chest pain, and neck and shoulder pain. Causes include dehydration or blood loss; disorders of the neurologic, cardiovascular, or endocrine systems; and several classes of medications. Evaluation of suspected orthostatic hypotension begins by identifying reversible causes and underlying associated medical conditions. Head-up tilt-table testing can aid in confirming a diagnosis of suspected orthostatic hypotension when standard orthostatic vital signs are nondiagnostic; it also can aid in assessing treatment response in patients with an autonomic disorder. Goals of treatment involve improving hypotension without excessive supine hypertension, relieving orthostatic symptoms, and improving standing time. Treatment includes correcting reversible causes and discontinuing responsible medications, when possible. Nonpharmacologic treatment should be offered to all patients. For patients who do not respond adequately to nonpharmacologic treatment, fludrocortisone, midodrine, and pyridostigmine are pharmacologic therapies proven to be beneficial.     

Assessment of orthostatic blood pressure: measurement technique and clinical applications

BACKGROUND: Orthostatic hypotension, a decline in erect blood pressure, is the result of an impaired hemodynamic response to an upright posture or a depletion intravascular volume. The measurement of orthostatic blood pressure can be done at the bedside and therefore is easily applied to several clinical disorders. Despite its usefulness, the measurement is often neglected, possibly because of confusion regarding the appropriate measurement technique and suitable application to patient care. METHODS: Pertinent recent medical literature was reviewed. RESULTS: The normal physiologic response to the assumption of an upright posture is a small drop in blood pressure and a slight rise in pulse rate. Orthostatic hypotension is detected by measurement of blood pressure in two or more body positions. An abnormal blood pressure response can be observed with disorders such as syncope, falling, intravascular volume depletion, and autonomic dysfunction; with the treatment of maladies such as hypertension and heart failure; and with the use of several medications. CONCLUSIONS: The measurement of orthostatic blood pressure is an essential clinical tool for the assessment and management of patients affected by common medical disorders.     

Incidence and outcome of orthostatic hypotension in stroke patients undergoing rehabilitation

OBJECTIVES: To document the incidence and outcome of orthostatic hypotension in stroke patients undergoing rehabilitation and to determine clinical variables associated with it. DESIGN: Cohort study. SETTING: Inpatient setting of a tertiary rehabilitation center. PARTICIPANTS: Seventy-one stroke patients (41 men, 30 women; mean age, 58.4+/-10.7 y) with a first clinical stroke, admitted for rehabilitation within 4 weeks of the stroke. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Patients' blood pressure was measured in supine position and on tilting at 90 degrees within 3 days of admission. Orthostatic hypotension was defined as a drop in systolic blood pressure (SBP) of 20 mmHg or more. RESULTS: Orthostatic hypotension was present in 37 (52.1%) patients, of whom 13 had severe hypotension (standing SBP, < or =100 mmHg). Twelve (32.4%) patients with orthostatic hypotension were positive for hypotensive symptoms and signs, with 2 patients experiencing near syncope. Orthostatic hypotension was significantly associated with older patients, a lower admission functional status (as measured on the Modified Barthel Index), and more severe hemiparesis. It was, however, not related with the site of stroke or the use of antihypertensives. On discharge, orthostatic hypotension had resolved in 23 patients. The presence of orthostatic hypotension did not influence functional outcome or the length of stay in rehabilitation. CONCLUSION: Orthostatic hypotension was common in stroke patients undergoing inpatient rehabilitation. It should be suspected in older patients who have more severe hemiparesis and a lower functional status.     

Fluoxetine in orthostatic hypotension of Parkinson's disease: A clinical and experimental pilot study

Summary— Recent clinical studies have reported a beneficial effect of fluoxetine, a serotonin reuptake inhibitor, in patients with severe refractory orthostatic hypotension. The present study was undertaken to investigate the effect of fluoxetine in orthostatic hypotension occurring during Parkinson's disease on both blood pressure values and number of clinical symptoms during orthostatic procedure evaluated using a validated clinical rating scale. In a pilot study performed in fourteen patients with idiopathic Parkinson's disease plus orthostatic hypotension, fluoxetine hydrochloride (20 mg orally daily during one month) significantly reduced the fall in systolic blood pressure [-33 ± 21 (SD) mmHg before fluoxetine vs -22 ± 19 mmHg after fluoxetine, P = 0.03] elicited by standing without modifying heart rate. The drug also significantly reduced the number of postural symptoms occurring during the orthostatic procedure [2.9 ± 1.5 (SD) before fluoxetine vs 1.2 ± 1.3 after fluoxetine, P = 0.006]. A similar pattern of response was obtained in an experimental model of neurogenic orthostatic hypotension obtained in chronically sino-aortic denervated dogs submitted to an 80° head-up tilt test procedure under chloralose anaesthesia. Fluoxetine did not change plasma noradrenaline levels. This pilot study suggests a slight but clinically significant effect of fluoxetine on both hemodynamic parameters and clinical symptoms in parkinsonian patients suffering from orthostatic hypotension.     

Adaptive Rate Pacing Controlled by Right Ventricular Preejection Interval for Severe Refractory Orthostatic Hypotension

A 72-year-old African-American man with frequent recurrent syncope was found to have severe refractory orihostatic hypotension with concomitant supine hypertension. Pharmacotherupy was successful in controlling his supine hypertension but was unable to resolve his severe orihostatic hypotension. Temporary fixed rate tachypacing was only minimally effective in preventing syncope during upright tilt, while variable rate pacing based on degree of blood pressure fall was far superior. Following these observations, an adaptive rate pacing system controlled by right ventricular preejection interval was implanted (Precept DR Model 1200). The system adequately sensed the patient's fall in blood pressure when sitting or standing and augmented its rate accordingly, thus preventing syncope. While supine, the pacing rate fell to 60 ppm, thereby, avoiding an exacerbation of his concomitant supine hypertension. Over a 3-nionth follow-up period, he has had no further orthostatic or syncopal episodes. We conclude that adaptive rate pacing using right ventricular preejection interval may be an effective treatment for severe refractory orthostatic hypotension.     

Xamoterol in the treatment of orthostatic hypotension associated with multiple system atrophy (Shy-Drager syndrome)

The effect of xamoterol on the orthostatic hypotension associated with Shy-Drager syndrome was investigated in three patients. Intra-arterial blood pressure was measured during a control period and during treatment with xamoterol, both in a cardiovascular investigation laboratory and for 24 h of unrestricted activity using portable apparatus. Xamoterol lessened the total number of symptomatic episodes of orthostatic hypotension by 67 per cent. Average untreated 24-h intra-arterial blood pressure was 132/78 mmHg; during treatment with xamoterol it rose to 138/90 mmHg. However episodes of severe hypertension (defined as a systolic intra-arterial blood pressure above 200 mmHg) were more frequent with xamoterol. Although xamoterol attenuated orthostatic hypotension, careful monitoring of ambulatory blood pressure may be necessary, particularly at the start of treatment, because of the development of severe supine hypertension. Intravenous test doses of xamoterol did not predict either the attenuation of orthostatic hypotension or the development of supine hypertension in all patients.     

Orthostatic hypotension

Orthostatic hypotension is a physical finding defined by the American Autonomic Society and the American Academy of Neurology as a systolic blood pressure decrease of at least 20 mm Hg or a diastolic blood pressure decrease of at least 10 mm Hg within three minutes of standing. The condition, which may be symptomatic or asymptomatic, is encountered commonly in family medicine. In healthy persons, muscle contraction increases venous return of blood to the heart through one-way valves that prevent blood from pooling in dependent parts of the body. The autonomic nervous system responds to changes in position by constricting veins and arteries and increasing heart rate and cardiac contractility. When these mechanisms are faulty or if the patient is hypovolemic, orthostatic hypotension may occur. In persons with orthostatic hypotension, gravitational opposition to venous return causes a decrease in blood pressure and threatens cerebral ischemia. Several potential causes of orthostatic hypotension include medications; non-neurogenic causes such as impaired venous return, hypovolemia, and cardiac insufficiency; and neurogenic causes such as multisystem atrophy and diabetic neuropathy. Treatment generally is aimed at the underlying cause, and a variety of pharmacologic or nonpharmacologic treatments may relieve symptoms.     

Orthostatic hypotension and cerebral blood flow velocity in the rehabilitation of stroke patients

The objective of this study was to investigate the results of transcranial Doppler monitoring during tilt table tests in stroke patients with and without orthostatic hypotension. In stroke patients without orthostatic hypotension, the mean flow velocity was almost similar in both middle cerebral arteries and was stable during the test. In patients with orthostatic hypotension symptoms, a significant difference was found between the two hemispheres. Mean flow velocity in the damaged middle cerebral artery was lower in the supine position and stayed almost the same at 80 degrees standing. In the non-damaged middle cerebral artery, however, the mean flow velocity was much higher when supine and dropped in the standing position. These findings suggest that the appearance of orthostatic hypotension symptoms may be associated in post-stroke patients with decreased blood velocity in the damaged middle cerebral artery. Those patients are at a high risk of developing syncopal reactions and should be treated on the tilt table with caution, especially at the beginning of the rehabilitation.     

Minoxidil therapy for refractory hypertension and chronic renal failure

Minoxidil, a potent vasodilator antihypertensive agent, was given to 14 patients with severe hypertension uncontrolled by conventional agents. Thirteen patients had elevated serum creatinine levels. Over a period of 20 months (mean duration of administration) minoxidil lowered blood pressure from 194/124 to 147/90 mm Hg (mean values), in combination with furosemide and a sympathetic inhibitor (usually propranolol). Progression of preexisting renal disease was halted in all but three patients. Fluid retention, cardiac failure, and angina were troublesome side effects. The occurrence of hypertrichosis also limited the usefulness of minoxidil, particularly in female patients.     

The impact of arm position on the measurement of orthostatic blood pressure

Blood pressure is a standard vital sign in patients evaluated in an Emergency Department. The American Heart Association has recommended a preferred position of the arm and cuff when measuring blood pressure. There is no formal recommendation for arm position when measuring orthostatic blood pressure. The objective of this study was to assess the impact of different arm positions on the measurement of postural changes in blood pressure. This was a prospective, unblinded, convenience study involving Emergency Department patients with complaints unrelated to cardiovascular instability. Repeated blood pressure measurements were obtained using an automatic non-invasive device with each subject in a supine and standing position and with the arm parallel and perpendicular to the torso. Orthostatic hypotension was defined as a difference of ≥ 20 mm Hg systolic or ≥ 10 mm Hg diastolic when subtracting standing from supine measurements. There were four comparisons made: group W, arm perpendicular supine and standing; group X, arm parallel supine and standing; group Y, arm parallel supine and perpendicular standing; and group Z, arm perpendicular supine and parallel standing. There were 100 patients enrolled, 55 men, mean age 44 years. Four blood pressure measurements were obtained on each patient. The percentage of patients meeting orthostatic hypotension criteria in each group was: W systolic 6% (95% CI 1%, 11%), diastolic 4% (95% CI 0%, 8%), X systolic 8% (95% CI 3%, 13%), diastolic 9% (95% CI 3%, 13%), Y systolic 19% (95% CI 11%, 27%), diastolic 30% (95% CI 21%, 39%), Z systolic 2% (95% CI 0%, 5%), diastolic 2% (95% CI 0%, 5%). Comparison of Group Y vs. X, Z, and W was statistically significant (p < 0.0001). Arm position has a significant impact on determination of postural changes in blood pressure. The combination of the arm parallel when supine and perpendicular when standing may significantly overestimate the orthostatic change. Arm position should be held constant in supine and standing positions when assessing for orthostatic change in blood pressure.     

老年高血压病患者体位性低血压的原因分析与护理对策

目的:探讨老年高血压病患者发生体位性低血压的原因,提出临床预防和护理对策,减少体位性低血压以及由此引发的并发症的发生。方法:对100例老年高血压病患者,先测卧位上肢血压,然后请患者直立3 min后,测同侧肢体立位血压,记录血压值、患者的主诉,合并基础疾病、联合用药(降压药)等情况,进行分析与研究。结果:老年高血压病患者体位性低血压发生率为26%;年龄>70岁、合并基础疾病、联合用药患者体位性低血压发生率高于年龄<70岁、无合并基础疾病、无联合用药患者(P<0.05)。老年高血压病患者随年龄增长发生生理、病理性改变,合并基础疾病致自主神经功能紊乱,联合用药致血容量变化是老年高血压病患者体位性低血压发生的主要原因。结论:老年高血压病患者易发生体位性低血压,护理的关键是明确病因,采取预防措施,减少体位性低血压及由此引发的并发症的发生。     

Topical treatment with minoxidil 2% and smoking intolerance.

OBJECTIVE: To report smoking intolerance that occurred in two patients while they were treated with minoxidil. DATA SYNTHESIS: Minoxidil is a potent vasodilator useful in treating severe hypertension. Topical minoxidil was approved as a treatment for androgenital alopecia. Only few side effects have been reported during treatment with topical minoxidil, most of them localized skin reactions. Two of our patients developed smoking intolerance during treatment with topical minoxidil for androgenital alopecia. The relation between treatment with minoxidil and smoking intolerance was emphasized by stopping treatment and the disappearance of the smoking intolerance, and then by rechallenge in both patients. CONCLUSIONS: Topical minoxidil may cause smoking intolerance; further studies are needed to evaluation this side effect.     

Update on the theory and management of orthostatic intolerance and related syndromes in adolescents and children

Orthostasis means standing upright. One speaks of orthostatic intolerance (OI) when signs, such as hypotension, and symptoms, such as lightheadedness, occur when upright and are relieved by recumbence. The experience of transient mild OI is part of daily life. ‘Initial orthostatic hypotension’ on rapid standing is a normal form of OI. However, other people experience OI that seriously interferes with quality of life. These include episodic acute OI, in the form of postural vasovagal syncope, and chronic OI, in the form of postural tachycardia syndrome. Less common is neurogenic orthostatic hypotension, which is an aspect of autonomic failure. Normal orthostatic physiology and potential mechanisms for OI are discussed, including forms of sympathetic hypofunction, forms of sympathetic hyperfunction and OI that results from regional blood volume redistribution. General and specific treatment options are proposed.     

滚筒作业活动对高位脊髓损伤患者体位性低血压的疗效影响

目的：观察滚筒作业活动对改善高位脊髓损伤患者的体位性低血压的临床效果。方法：40例脊髓损伤患者按随机分组原则分为对照组和观察组各20例,2组患者均进行起立床、气压、针灸及物理治疗和作业治疗等康复治疗方法,观察组在此基础上每天进行辅助下的20 min的滚筒作业活动,每周5次,持续6周。记录2组患者在治疗前后晨起卧床时的血压值及站起立床到最高角度时站床角度值和此时血压值,并记录2组患者轮椅端坐位下体位性低血压不适感消失的时间和不适感消失的情况。结果：治疗6周后,2组患者晨起卧床时的收缩压和舒张压均明显高于治疗前(均P＜0.01)。2组患者站起立床最高角度的收缩压均明显高于治疗前(均P＜0.01),观察组的舒张压明显高于治疗前(P＜0.01),且观察组收缩压和舒张压均明显高于对照组(均P＜0.05)。2组患者站起立床到最高角度值均明显高于治疗前(均P＜0.01),且观察组站起立床到最高角度值明显高于对照组(P＜0.01)。观察组不适感消失的情况明显优于对照组(P=0.011),体位性低血压不适感消失时间明显少于对照组(P=0.001)。结论：滚筒作业活动可以改善高位脊髓损伤患者体位性低血压现象：提高体位性低血压的血压值和改善体位性低血压的不适感。