Vascular distensibility and compliance in salt-sensitive and salt-resistant borderline hypertension

OBJECTIVE: To gain insight into the relationship between vascular compliance and sodium sensitivity. DESIGN: Arterial and venous compliance was determined in 17 sodium-sensitive and 28 sodium-resistant, young, borderline hypertensive males and in 10 age-matched normotensive controls, during regular sodium intake. METHODS: The carotid, femoral and brachial arteries were studied using a non-invasive ultrasound vessel wall movement detector system, and venous compliance was determined using forearm strain-gauge plethysmography. Cardiac output, plasma volume and hormonal factors, such as plasma renin activity, were also measured to assess their possible influence on vascular compliance. RESULTS: Large artery compliance was significantly less in the sodium-sensitive than in the sodium-resistant subjects in all arteries studied. Compared with controls, arterial compliance was reduced significantly in the sodium-sensitive group, whereas the sodium-resistant group did not differ significantly from the controls. Venous compliance was reduced equally in the two hypertensive groups compared with the controls, although the differences did not reach statistical significance. Cardiac output, blood pressure, plasma volume and hormonal factors did not differ between sodium-sensitive and sodium-resistant subjects and could not have been responsible for the observed differences in arterial compliance. CONCLUSIONS: The results of this study suggest that sodium-sensitive borderline hypertensives have reduced large artery compliance compared with age-matched sodium-resistant subjects. Since this finding could not be explained by differences in haemodynamic or hormonal factors between the groups, this suggests alterations to the viscoelastic properties of the arterial walls in sodium-sensitive subjects.     

Evaluation of segmental elastic properties of the aorta in normotensive and medically treated hypertensive patients by intravascular ultrasound

DESIGN AND METHODS: Local elastic properties of the descending aorta at different levels were evaluated by means of intravascular ultrasound images and pressure measurements. For this purpose, 30 normotensive patients and 30 age-matched medically treated patients with essential hypertension, all undergoing diagnostic cardiac catheterization, were studied. RESULTS: Hypertension was well controlled in the essential hypertensives (137.1 +/- 6.79/74.5 +/- 2.65 mmHg). Systolic but not diastolic blood pressure in the hypertensive patients was significantly different from that of the normotensives (118.8 +/- 4.38/69.7 +/- 1.65 mmHg). The continuous loss of volume compliance with increasing distance from the heart was significantly higher in the hypertensives than in the normotensive patients [normotensives (1.45 +/- 0.19) x 10(-10) m5/N at the thoracic aorta, (0.08 +/- 0.05) x 10(-10) m5/N at the external iliac artery; hypertensives (0.81 +/- 0.09) x 10(-10) and (0.05 +/- 0.01) x 10(-10) m5/N at the corresponding sites]. Similarly, the hypertensives had an elevated elastic modulus proximal to the aortic bifurcation compared with the normotensives (244.47 +/- 44.06 versus 108.10 +/- 17.76 m/s, respectively). The decrease in buffering function of the vessel at this site is presumably caused by a turbulent flow pattern. Compared with the normotensives, the treated hypertensives had a significantly higher elastic modulus at each site where this was measured, whereas volume compliance and sectional compliance were lower. CONCLUSION: The differences in elastic modulus and compliance between hypertensive and normotensive patients seem disproportionate to the difference in systolic blood pressure (within the normal range in both the treated hypertensives and the normotensives). Therefore, normalization of high blood pressure by long-term antihypertensive treatment may not fully reverse changes, caused by arterial hypertension, in the viscoelastic properties of the arterial wall.     

Treatment of hypertension at the university medical clinic

The treatment of high blood pressure at the general medical clinic of a traditionally oriented university hospital was found to be unsatisfactory for most patients. Charts of all hypertensive patients (diastolic blood pressure, greater than or equal to 105 mm Hg) who made their first clinic visit in 1964 or 1971 were reviewed. Half of all patients were lost to follow-up within the first year, and blood pressure control was achieved by only one third of the patients. New information contained in the Veterans Administration study reports (1967 and 1970) had no effect on workup, compliance, or blood pressure decline. Furthermore, no significant relationship was found between blood pressure reduction and medical process, therapeutic regimens, or patient compliance. These data suggest that, in contrast to experience obtained in programs specifically designed for long-term management of this chronic disease, the present-day general medical clinic cannot satisfy the needs of most hypertensive patients.     

Hepatic venous compliance and role of liver as a blood reservoir

Changes in hepatic blood volume in response to rapid elevations in hepatic venous pressure were examined in cats using hepatic plethysmography. The liver was intact and received blood from an intact portal vein and hepatic artery. The hepatic blood volume increased in response to elevated venous pressure. Compliance of the hepatic capacitance vessels became greater as the distending venous pressure was increased over the range of venous pressures studied (0-9.4 mmHg). When hepatic venous pressure was elevated to 9.4 MMHg, the hepatic blood volume more than doubled. The liver serves as an important buffer for rapid changes in blood volume, the importance increasing with greater infused volumes of fluid. While overall venous compliance decreased at distending pressures in excess of 5-6 mmHg, the compliance of the hepatic capacitance vessels shows marked increases at pressures above this level. Expansions of the blood volume results in elevations of central venous pressure. Within a few minutes the hepatic capacitance vessels sequester a significant proportion of the added volume. As long as central venous pressure is raised, the liver demonstrates a secondary fluid buffering role by filtering large volumes of fluid across the vascular bed into the peritoneum.     

Effects of hypervolemia on interdialytic hemodynamics and blood pressure control in hemodialysis patients

The influence of hypervolemia on hemodynamics and interdialytic blood pressure, as well as in relation to vascular compliance, was investigated in 10 hemodialysis patients who were not receiving vasoactive medication. All subjects were studied during a relative normovolemic interdialytic period (from 1 kg below dry weight postdialytic until dry weight predialytic) and a hypervolemic interdialytic period (from 1 kg above dry weight postdialytic until 3 kg above dry weight predialytic). Interdialytic blood pressure was measured with an ambulatory blood pressure monitor. Cardiac output was echographically measured and total peripheral resistance calculated postdialytic, mid-interdialytic, and predialytic. At the same time, a blood sample was drawn for analyzing vasoactive hormones, sodium, and hematocrit. In all patients, ideal dry weight was estimated by echography of the caval vein. Arterial and venous compliance were measured with an ultrasound vessel wall movement detector system and a strain-gauge plethysmograph. After fluid load, an increase in intravascular volume, an increase in caval vein diameter and cardiac output, and a decrease in peripheral resistance was observed. No significant influence of a 3-L fluid load was found on interdialytic blood pressure course (153+/-24 mm Hg/90+/-19 mm Hg in the hypervolemic period and 146+/-27 mm Hg/89+/-22 mm Hg in the normovolemic period). Sodium and osmolality were similar in the hypervolemic and normovolemic interdialytic periods. After fluid load, a decrease in arginine vasopressin and angiotensin II was observed, which probably contributed to the decreased systemic vascular resistance. Catecholamines were not influenced by fluid load, but increased during the interdialytic period, suggesting accumulation after dialysis. Three of the 10 patients had higher systolic but not diastolic blood pressures after fluid load (159+/-13 mm Hg/81+/-22 mm Hg in the hypervolemic period and 135+/-16 mm Hg/81+/-22 mm Hg in the normovolemic period). No correlation could be found between arterial or venous compliance and blood pressure changes. We concluded that a 3-L interdialytic fluid load does not result in higher blood pressure in most hemodialysis patients.     

Cardiac function and dysfunction in hypertension

BACKGROUND: Hypertension is the most common condition of increased left ventricular afterload that affects the cardiovascular system. OBJECTIVE: To review the effects of increased blood pressure on cardiac function. SUMMARY: In early or borderline hypertension, cardiac output increases but intravascular volume remains normal. In uncomplicated established hypertension, left ventricular systolic function is generally normal at rest; however, the left ventricular filling rate is reduced in approximately 30% of hypertensive patients without associated alterations in systolic function. In the presence of left ventricular hypertrophy, overall left ventricular systolic performance remains within normal limits; however, left hypertrophy in hypertension is associated with a high morbidity rate, possibly due to increased collagen concentration leading to reduced left ventricular compliance, fewer adrenergic receptors, reduced responsiveness of the adenylate cyclase system, and reduced coronary flow reserve. Acute increases in blood pressure in a hypertensive patient may worsen cardiac function, particularly in the presence of medications that interfere with the adrenergic support of the heart. New, accurate, noninvasive techniques can assess cardiac structural and functional aspects of hypertension under precise circumstances. CONCLUSIONS: Assessing both systolic and diastolic function is important in the follow-up of hypertensive patients and in the choice of therapy.     

Enhancement of latent inhibition in the rat by the atypical antipsychotic agent remoxipride

It has been hypothesized that as large arteries become more rigid with age, the pattern of hypertension changes from diastolic to systolic. Thus, diastolic blood pressure (DBP) may lose its ability to reflect the increase in vascular resistance with age. To assess this, we studied the age-related changes in blood pressure pattern and its steady-state and pulsatile determinants. We performed an epidemiological analysis based on a national survey of 10,462 subjects from Argentina. A hemodynamic analysis (impedance cardiography) was then carried out in 636 consecutive hypertensive patients (age, 25 to 74 years). Whereas the rate of increment in the prevalence of mild to moderate hypertension (MMH) reached a plateau after the sixth decade, isolated and borderline systolic forms of hypertension began a steep and sustained rise. Among patients with MMH, DBP remained stable from the third to the seventh decade, whereas SBP maintained a sustained increase. Despite similar DBP, the systemic vascular resistance index increased 47% (P<.01) and the cardiac index decreased 27% (P<.01), whereas the ratio of stroke volume to pulse pressure, an index of arterial compliance, decreased 45% (P<.01). However, there were no significant differences between older patients with MMH and those with isolated systolic hypertension in the level of SBP, vascular resistance, stroke volume, and cardiac index. Compared with age-matched normotensive control subjects, the ratio of stroke volume to pulse pressure was much more reduced in isolated systolic hypertension (48%) than in MMH (30%). In summary, the present study, carried out in a large sample of hypertensive subjects with a wide age range, showed a simultaneous impairment in vascular resistance and arterial compliance associated with aging in different patterns of hypertension. The magnitude of these changes, with opposite effects on DBP but additive effects on SBP, suggests that a hemodynamic mechanism could determine the transition in the prevalence of diastolic hypertension toward a systolic pattern of hypertension with aging. Also, the results suggest that SBP, but not DBP, is a reliable indicator of the underlying hemodynamic abnormalities (high resistance and low arterial compliance) in the elderly.     

Circadian urinary excretion of catecholamine, plasma atrial natriuretic peptide, endothelin and neuropeptide Y in obese patients with hypertension

Obesity increases the risk of developing hypertension by two-to fourfold, with more that one third of all cases of hypertension attributable to obesity. The present study tested the role of atrial natriuretic peptide (ANP), endothelin-1,2 (ET-1,2) and neuropeptide Y (NPY) in pathogenesis of obesity hypertension. The plasma concentrations of ANP, ET-1,2 and NPY were determined in the peripheral venous blood by radioimmunoassay in 27 obese hypertensive patients (group I), in 24 obese normotensive patients (group II), and in 35 normal subjects (group III). RESULTS: Mean plasma ANP was significantly higher in obese than in normal subjects. ANP levels were higher in patients group I than in those group II and I. In patients of group I plasma ANP concentrations correlated with III BMI and mean blood pressure. Plasma levels of ET-1,2 and NPY were similar in patients group I, II and III.     

Fenfluramine potentiation of antihypertensive effects of thiazides

Hydrochlorothiazide, a drug which is often initially prescribed for mild to moderate hypertension, failed to lower blood pressures in 9 of 43 patients but concomitantly elevated plasma norepinephrine (NE) levels in all patients with hypertension. The 9 obese hydrochlorothiazide-resistant patients were then given fenfluramine, an anorectic, in addition to the thiazide. They were reevaluated after 2 and 5 wk, at which times there were reductions in blood pressures and marked reductions in the plasma NE levels which had been elevated by the hydrochlorothiazide. Since iatrogenic sympathetic activation seems undesirable in treating hypertension, fenfluramine may be useful in obese thiazide-resistant hypertensive patients when used in combination with a thiazide diuretic.     

Obesity and hypertension

An increasing number of clinical trials have demonstrated that obese patients are more likely than lean individuals to be hypertensive. Moreover, both obesity and arterial hypertension have been identified as independent risk factors for cardiovascular disease. Pathophysiologically, obesity appears to have a major influence on the hemodynamic changes associated with hypertension. The available evidence suggests that at any given level of arterial pressure, obese hypertensive patients have a higher cardiac output and lower total peripheral resistance than do lean patients. Recent reports have indicated that obesity exerts a disparate effect on target organs in hypertension. Whereas at rest obesity seems to mitigate cardiovascular changes in the systemic vascular bed caused by hypertension, no such mitigation was observed in the renovasculature; left ventricular hypertrophy as a major cardiovascular risk factor was even exacerbated by the presence of obesity. The different hemodynamic patterns in obese hypertensive patients have recently been shown clinically relevant for treating hypertensive patients.     

Diurnal blood-pressure variations in haemodialysis and CAPD patients

The influence of variations in fluid state on diurnal blood pressure was studied by measuring day-time and night-time blood pressure during a 3-day interdialytic period in 10 normotensive and 10 hypertensive haemodialysis patients using Spacelab 90207 Monitors. Ambulatory blood pressure was also measured during 24 h in 11 normotensive and nine hypertensive CAPD patients, and in nine normotensive and 11 hypertensive control patients with a normal renal function. Antihypertensive drugs had been discontinued for at least 3 weeks before the study period. Optimal dry weight in the haemodialysis patients was estimated by echography of the inferior vena cava and in the CAPD patients on clinical grounds. Although in the dialysis patients and controls a significant nocturnal blood pressure reduction was found, day-night blood pressure difference in the dialysis patients was blunted when compared with the control patients. No significant differences in diurnal blood pressure variation was found between the normotensive and the hypertensive patients. Day-night blood pressure differences in the haemodialysis patients did not change during the 3-day interdialytic period. Also the more stable fluid state of the CAPD patients was not associated with significant different diurnal blood pressure variation compared to the haemodialysis patients. We conclude that factors other than changes in extracellular fluid volume are responsible for a blunted day-night difference in blood pressure in dialysis patients.     

Arterial embolization of bone metastases: is it worthwhile?

Arterial embolization was performed in ten skeletal metastases occurring in nine patients: eight patients presented with renal cell carcinoma and one with bronchogenic carcinoma. Five metastatic lesions were located in the spine, one in the pelvis, three in the proximal humerus and one in the proximal femur. Selective arterial embolization was performed preoperatively in seven cases and as a palliative treatment in three cases. The embolic material used was polyvinyl alcohol particles, gelatin sponge and coils or a combination of these. Arterial embolization was technically successful in all patients achieving subtotal (> 90%) tumour devascularization in five metastases and a 75% devascularization in the remaining five lesions. In operative patients, median intra-operative volume of blood transfusion was 510 mL. Palliative embolization was followed by major pain relief in two cases and moderate relief in one case lasting from 7 to 26 months. Arterial embolization is an effective and safe adjunctive treatment of hypervascular bone metastases.     

Investigation of the loss of bone mineral in patients with spinal cord injury

1. Blood pressure, blood volume and renal blood flow were determined in 101 men; forty-three were normal subjects and fifty-eight were untreated permanent essential hypertensive patients with normal renal function and equilibrated sodium balance. 2. A significant negative pressure-volume relationship was observed overall. The relationship could be expressed as a hyperbola whose slope expressed the reduction in blood volume per unit rise in pressure: the higher the blood pressure, the lower the slope. Thus essential hypertensive subjects have a smaller decrement in blood volume per unit rise in pressure than normal subjects. 3. The relation between change in blood volume and change in pressure was confirmed in each individual by defining for each a ration deltaV/deltaP, statistically identical with the hyperbolic slope dV/dP. The deltaV/deltaP ratio was found to be well correlated with the renal blood flow and the creatinine clearance. No correlation existed between the total blood volume and these two renal parameters. 4. It is concluded that the present study demonstrates a blood volume regulation disturbance in essential hypertension and provides evidence from human studies that a renal defect accompanies high blood pressure.     

The renal factor in the post-traumatic "fluid overload" syndrome

Hypervolemia with hypertension often occurs 36-72 hours following massive blood and fluid replacement for hypovolemic shock. This syndrome of "fluid overload" has been attributed to the rapid intravascular flux of previously sequestered fluid in patients with impaired diuresis. This hypothesis was tested in 35 injured patients who received a mean of 9.3 L of blood and 17.4 L of salt during resucitation. The renal parameters measured soon after resuscitation included: 1) renal clearance of inulin (GFR), para-amino hippurate (ERPF), milliosmoles, sodium, and free water; 2) inulin space, renal vascular resistance (RVR), O2 consumption, renin, renal blood flow (RBF), and response to furosemide. Eighteen patients developed hypertension, hypervolemia, and respiratory insufficiency. When compared to the 17 normovolemic, non-hypertensive patients, the 18 hypervolemic patients had significantly increased RVR, with a significant decrease in RBF despite an increase in plasma volume and cardiac output. Furosemide produced less diuresis and natriuresis in the hypertensive patients. The balance between hypovolemia and "fluid overload" seemed percarious in the hypertensive patients. Peripheral renin and catecholamine levels were normal in both groups. Patients with post-traumatic "fluid overload" appear to have a combination of hypervolemia, respiratory insufficiency, hypertension, increased cardiac output, decreased extracellular fluid space, and decreased renal perfusion. These findings suggest that decreased interstitial fluid space compliance rather than "fluid overload" is the underlying factor leading to respiratory insufficiency. The therapeutic aspects of these findings are discussed.     

Effects of crystalloid solutions on circulating lactate concentrations: Part 1. Implications for the proper handling of blood specimens obtained from critically ill patients

OBJECTIVES: a) To test the hypothesis that circulating lactate concentrations are the same in simultaneously collected arterial and central venous blood specimens; b) to test the hypothesis that even small amounts of crystalloid solutions, which are inadequately "cleared" from these indwelling arterial and venous catheters, can lead to clinically important and misleading changes in the measured lactate values. DESIGN: A prospective, multiexperiment study. SETTING: A critical care research laboratory and a 20-bed intensive care unit (ICU). PATIENTS: Three hundred fifty-five patients. INTERVENTIONS: Blood samples were collected. MEASUREMENTS AND MAIN RESULTS: Experiment 1: Simultaneously collected arterial and central venous blood specimens were obtained on 148 occasions from 48 medical ICU patients receiving no lactated Ringer's solution (RL). Arterial and central venous lactate values were nearly identical in these patients. The correlation between the arterial and central venous lactate concentrations was excellent (r2 = .85; p < .0001) and the agreement between the arterial and central venous lactate concentrations was also excellent (bias and precision = 0.04 mmol/L and +/- 0.38 mmol/L, respectively). Experiment 2: Arterial and mixed venous blood samples were obtained from 100 percutaneous transluminal coronary angioplasty (PTCA) and 75 cardiac surgical patients immediately before the performance of these cardiac procedures. We found the central venous lactate concentrations to be higher than arterial lactate values in the cardiac surgical group, and there was a very poor correlation (r2 = .07) between arterial and central venous lactate values in the cardiac surgical group. The correlation between central venous and arterial lactate concentrations in the PTCA patients was excellent (r2 = .84) and similar to the findings of experiment 1. Since the cardiac surgical patients received RL and the PTCA patients received no RL, we speculated that the intravenous infusion of RL in the cardiac surgical group accounted for these discordant findings. To test this speculation, we performed experiments 3 and 4. Experiment 3: In a large bench study, blood specimens were divided into multiple 1-mL aliquot portions, to which 0.01, 0.05, 0.10, 0.50, or 1.0 mL of various crystalloid solutions, containing or not containing RL, were added. In a volume-dependent and linear manner, solutions containing RL increased the circulating lactate concentration from 10% to > 400% of the baseline lactate value. In a volume-dependent and linear fashion, the non-RL crystalloid solutions decreased the lactate concentration by 0 to 66% of the baseline nondiluted lactate concentration. Experiment 4: In 30 different cardiac surgical patients, we simultaneously obtained central venous and arterial blood specimens. Patients this time received no RL, and catheter lines were adequately cleared (removal > 5 mL) of crystalloid solutions. We found a correlation (r2 = .82; p < .0001) that was virtually identical to the findings of experiment 1 and to the findings in the PTCA group of experiment 2. CONCLUSIONS: a) Arterial and central venous lactate concentrations are similar in hemodynamically stable critically ill patients, b) Even small amounts of RL-containing solutions in catheters used for blood sampling may cause false increases in the circulating lactate concentration. c) Even small amounts of non-RL crystalloid solutions in catheters used for blood sampling may falsely decrease circulating lactate values. d) When blood specimens are drawn from indwelling catheters, all crystalloid solutions must be cleared from the line.     

Duplex sonography of renal arteries as a diagnostic tool in hypertensive children

Computed duplex sonography was used to examine the renal arteries in 36 hypertensive children and adolescents (ages 4-17 years) with arterial hypertension of either renal or non-renal origin. Time-averaged flow velocities, maximum blood flow velocities as well as absolute renal blood flow and renal blood flow per gram kidney weight were measured. Normal flow velocities and normal to elevated renal blood flow volume was found in patients with acute glomerulonephritis and those with signs of chronic glomerulonephritis onset. Patients having advanced stages of chronic glomerulonephritis, on the other hand, were characterized by lower levels of all parameters. Unilateral renal artery stenosis was diagnosed correctly in four patients, although one intra-renal artery stenosis escaped imaging. Scarred kidneys exhibited low-normal or reduced flow velocities and renal blood flow volumes corresponded roughly to kidney size and preservation of normal kidney structure. Hypertension in some patients with normal kidneys showed a tendency to cause higher renal blood flow without consistent acceleration of blood flow velocities. We conclude that duplex sonography is a suitable primary diagnostic tool in measuring blood flow velocities and absolute renal blood flow volume in hypertensive children, thus facilitating the choice of the next diagnostic step.     

Solo and nonsolo dental practices: impact of increasing number of female dentists and the cost of a dental education

This study involved subjective evaluation of airway patency, linear measurement of orocraniofacial architecture, and blood pressure measurement in 38 obese sufferers of sleep apnea and 38 matched controls. The study demonstrated that airway management in the sleep apnea group was difficult on both induction and emergence from general anesthesia. Moreover, a smaller, compressed oropharynx was observed in the sleep apnea group. In addition, patients with sleep apnea were characteristically hypertensive. More nursing research is needed to enhance understanding of patients afflicted with sleep apnea and to improve their life quality.     

Weight reduction regresses left ventricular mass regardless of blood pressure level in obese subjects

The effects of weight reduction on left ventricular mass in obese normotensive and hypertensive subjects were investigated. Previous studies have shown that weight reduction in hypertensive (HT) obese patients is associated with decreased left ventricular mass (LVM) and decreased blood pressure (BP). This study was performed to examine whether weight reduction would also regress LVM in normotensive (NT) obese subjects and to clarify the mechanisms of these effects if they occurred. A weight-reduction program consisted of mild exercise and mild hypocaloric intake. M-mode echocardiography was performed to estimate the LVM. After the 12-week intervention, the mean reductions in body weight (BW) in the NT (n = 11) and HT (n = 11) groups were 4.9 kg (p < 0.005) and 4.6 kg (p < 0.0005), respectively. Systolic, diastolic, and mean BP were significantly reduced by 13, 9, and 11 mm Hg, respectively, in the HT group. By contrast, no significant changes in systolic, diastolic, or mean BP were observed in the NT group. LVM was significantly reduced from 176 +/- 26 gm to 159 +/- 26 gm (p < 0.05) in the HT group and from 167 +/- 33 gm to 145 +/- 34 gm (p < 0.02) in the NT group. These results suggest that weight reduction in obese subjects by mild exercise and mild hypocaloric intake can lead to a reduction in LVM, regardless of whether the subjects have normal or high blood pressure.