[Large artery wall properties -- what is relevant for the classic management of hypertension?]. / Gefässwandeigenschaften grosser Arterien -- was ist wichtig für das klassische Hypertoniemanagement?

Decisions about the management of patients with hypertension should not be based on the level of blood pressure alone but also on the presence of target organ damage. Apart of classical sites of target organ damage - kidney and heart - the assessment of functional and structural alterations of large arteries is of increasing clinical importance. Modern non-invasive procedures allow the assessment of large artery wall properties within the clinical routine. Hypertension associated large artery damage may present as structural and functional alterations. Structural alterations comprise intima-media thickening, plaque formation, stenosis of the artery and formation of aneurysms. Functional alterations comprise endothelial dysfunction and alterations of the mechanical properties of the arterial wall with increasing stiffness and loss of the Windkessel function. Loss of central artery elastic properties will ensue an early reflection of the pulse wave with a resulting increase in central systolic and central diastolic pressure. This causes an increase in left ventricular afterload and a reduction in diastolic perfusion of the myocardium. In the last decade the relevance of large artery structural alterations, endothelial dysfunction and arterial stiffness for the risk of cardiovascular morbidity and mortality in hypertensive patients could be demonstrated convincingly. Measurement of intima-media-thickness therefore is part of the standard evaluation of hypertensive patients. Because of the equal prognostic relevance of functional properties of the arterial wall, assessment of large artery functional alterations is helpful for the risk stratification of hypertensive patients. Modern antihypertensive drugs have favourable effects on arterial wall properties. Therefore, the quantification of large artery wall properties should be part of the management of hypertensive patients.

Acute effects of haemodialysis on endothelial function and large artery elasticity.

BACKGROUND: Disturbances of functional properties of large arteries contribute to increased cardiovascular morbidity and mortality in patients with end-stage renal disease. However, it is not clear whether haemodialysis per se acutely affects mechanical vessel wall properties or endothelial function. METHODS: Twenty-five chronic haemodialysis patients (mean+/-standard error of the mean (SEM): age 52+/-5 years; time on dialysis 63+/-7 months; blood pressure 132+/-4/72+/-2 mmHg) were studied before and immediately after a haemodialysis (HD) session using a polysulphone dialyser (ultrafiltration 1460+/-54 ml), as well as on the following day. Blood pressure was measured with an automatic sphygmomanometer and applanation tonometry. End-diastolic diameter and distension of the brachial and carotid arteries were measured by Doppler frequency analysis of vessel wall movements in M-mode using a multigate pulsed Doppler system and aortic pulse wave velocity (PWV) by an automatic device (Complior). Endothelial function was determined as brachial artery flow-mediated dilation (FMD) and compared with endothelium-independent nitroglycerine-induced dilation (NMD). RESULTS: FMD was 7.9+/-1.8% in patients before HD and did not change significantly after HD or in the dialysis-free intervall (6.7+/-2.1 and 7.1+/-2.0%, respectively; NS). The same was true for NMD and PWV (12.6+/-0.8 m/s before HD, 12.8+/-0.8 m/s after HD, and 11.9+/-0.7 m/s on the HD-free day). Carotid distensibility coefficients decreased significantly during HD (from 18.1+/-1.9 x 10(-3)/kPa to 16.7+/-2.2 x 10(-3)/kPa, P<0.05) and increased again on the HD-free day (19.8+/-2.4 x 10(-3)/kPa). However, when corrected for blood pressure by tonometry, isobaric carotid distensibility did not change significantly. Brachial artery distensibility also did not show significant acute changes. CONCLUSIONS: Haemodialysis per se did not have a significant effect on endothelial function or large artery mechanical vessel wall properties in patients on maintenance dialysis therapy.

Arterial distensibility and pulse wave velocity in patients with primary hyperparathyroidism before and after parathyroidectomy.

AIMS: There is evidence that secondary hyperparathyroidism alters arterial vessel wall properties. However, it is unclear whether effects of parathyroid hormone (PTH) on the vascular wall are direct or permissive and related to hypertension and renal failure. To assess early direct effects of PTH on large artery wall properties isobaric distensibility (DC), pulse wave velocity (PWV) and intima-media thickness (IMT) were studied before and after parathyroidectomy (Ptx) in patients with primary hyperparathyroidism (pHPT). METHODS: DC and IMT of the brachial and carotid artery were measured by echo-tracking and tonometry, PWV by the automatic Complior-device at baseline and 6 months after Ptx in 20 patients with pHPT (data mean +/- SEM, age 45+/-5 years, PTH 240+/-61 ng/l). Cardiovascular risk factors like diabetes, hypertension, renal insufficiency and hypercholesterolemia were excluded. Twenty healthy volunteers matched for age, sex and blood pressure served as controls. RESULTS: Six months after Ptx, PTH decreased to normal; however, blood pressure levels and vessel wall parameter remained unchanged. At baseline, there were no significant differences in brachial and carotid IMT (0.48+/-0.04 and 0.62+/-0.04 mm vs. 0.47+/-0.06 and 0.61+/-0.06 mm), radial and aortic PWV (9.1+/-0.4 and 9.9+/-0.7 m/s vs. 9.2+/-0.5 and 10.0+/-0.6 m/s), brachial and isobaric carotid DC (10.1+/-1.4 and 19.5+/-3.4 10(-3)/kPa vs. 9.1+/-0.9 and 20.4+/-3.2 10(-3)/kPa) or artery diameter between patients and controls. CONCLUSIONS: Structural and viscoelastic properties of large arteries are not disturbed and not influenced by parathyroidectomy in patients with early pHPT devoid of hypertension and renal disease. We conclude that increased PTH levels per se are not associated with alterations of mechanical arteriall wall properties; permissive factors like renal insufficiency may be necessary to mediate vessel wall alterations in patients with hyperparathyroidism.

Effect of fluvastatin on endothelium-dependent brachial artery vasodilation in patients after renal transplantation.

BACKGROUND: Hypercholesterolemia may affect both endothelial function and arterial distensibility (DC). Renal transplant recipients (NTX) exhibit advanced structural and functional alterations of arterial vessel walls. The aim of this double-blind, randomized trial was to evaluate the effects of fluvastatin (FLU) on brachial artery flow-mediated vasodilation (FMD) and DC in hypercholesterolemic NTX. METHODS: Eighteen NTX received FLU 40 mg/day and 18 NTX placebo (PLA). Before and after six months of treatment, the brachial artery diameter and DC at rest were measured by a Doppler frequency analysis in the M mode, and then changes in diameter during reactive hyperemia (to assess endothelial-dependent FMD) and after 400 microg sublingual nitroglycerin (to assess endothelium-independent vasodilation-NMD). RESULTS: FLU, but not PLA, treatment resulted in significant decreases in total (from 288 +/- 10 to 239 +/- 8 mg/dL, P < 0.05) and low-density lipoprotein cholesterol (from 182 +/- 779 to 138 +/- 8 mg/dL, P < 0.05). Blood pressure did not differ between FLU- and PLA-treated patients and was not affected by either treatment. Also, the brachial artery baseline diameter was not different between groups and was not affected by FLU or PLA. Brachial artery flow at rest and during reactive hyperemia as measured by pulsed Doppler did not differ between groups. Brachial artery FMD increased with FLU from 0.23 +/- 0.08 to 0.54 +/- 0.08 mm (P < 0.05), whereas PLA did not alter FMD (0.22 +/- 0.07 vs. 0.14 +/- 0.05 mm at baseline and after six months of PLA treatment, respectively, P = NS). In contrast, NMD did not change significantly with either treatment (0.76 +/- 0.13 vs. 0.83 +/- 0.15 mm at baseline and after 6 months of FLU treatment, respectively, P = NS, and 0.64 +/- 0.09 vs. 0.66 +/- 0.10 mm at baseline and after 6 months of PLA treatment, respectively, P = NS). Also, brachial artery DC was not altered by FLU (6.4 +/- 1.0 vs. 5.8 +/- 0.6 x 10-3/kPa, P = NS) or PLA treatment (5.8 +/- 0.6 vs. 6.8 +/- 0.8 x 10-3/kPa, P = NS). CONCLUSIONS: In hypercholesterolemic NTX, the HMG-CoA reductase inhibitor FLU significantly improves brachial artery FMD as a measure of endothelial function after six months of treatment. In contrast, FLU does not have a beneficial effect on brachial artery DC.

A novel assay for determination of diadenosine polyphosphates in human platelets: studies in normotensive subjects and in patients with essential hypertension.

OBJECTIVE: Diadenosine polyphosphates (APnAs, n = 3-6) are a family of endogenous vasoactive purine dinucleotides which have been isolated from thrombocytes. Diadenosine pentaphosphate (AP5A) and diadenosine hexaphosphate (AP6A) are more potent than diadenosine tetraphosphate (AP4A) and diadenosine triphosphate (AP3A) and cause skeletal muscle vasoconstriction in rats. Little is known about their physiological and pathophysiological significance in humans. The aims of the present study were to compare thrombocyte APnA concentrations in patients with essential hypertension (HYP) and in healthy normotensive humans (CON) using a novel quantitative assay and to assess a possible relationship between thrombocyte APnA concentrations and skeletal muscle vascular resistance. DESIGN AND METHODS: We describe a novel assay for quantification of APnAs in human platelets, involving platelet isolation from human blood, a solid-phase extracting procedure with a derivatized resin, desalting and quantitative determination of the substances with an ion-pair reversed-phase high-performance liquid chromatography (HPLC) system. The structural integrity of the isolated APnAs was confirmed by mixed assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) measurements and co-elution with added standards. The detection threshold for all four APnAs was 1 pmol/l and the inter-assay coefficients of variation were < 11% (n = 12). After venous blood sampling, mean arterial blood pressure (MAP) and forearm blood flow (FBF, using venous occlusion plethysmography) were measured in HYP and CON. Forearm vascular resistance (FVR) was calculated as MAP/FBF. significantly differ in platelet AP3A and AP4A content, but HYP had significantly higher thrombocyte concentrations of AP5A (56 +/- 7 versus 32 +/- 3 ng/microg beta-thromboglobulin, P = 0.003) and AP6A (10 +/- 1 versus 6 +/- 1 ng/microg beta-thromboglobulin, P = 0.015) than CON. HYP had significantly elevated FVR (50 +/- 6 versus 33 +/- 2 arbitrary units, P = 0.01) compared to CON. Significant correlations were found between AP5A and FVR (p = 0.38, P = 0.04) as well as between AP6A and FVR (p = 0.42, P = 0.02). In contrast, there were no significant correlations between APnAs and MAP. CONCLUSIONS: The study shows that thrombocyte concentrations of AP5A and AP6A are elevated in patients with essential hypertension. Vasoconstriction caused by release of AP5A and AP6A from thrombocytes may contribute to the increase of vascular resistance in hypertensive patients.

Increased membraneous calcium concentrations in primary hypertension: a causal link to pathogenesis?

BACKGROUND: Disturbance in calcium metabolism has been suggested in the pathogenesis of hypertension, however, membrane calcium content in humans has not been studied in detail yet in primary hypertension. We compared plasma, intracellular and membrane calcium concentrations in erythrocytes of patients with essential hypertension and in healthy, normotensive control subjects to determine a possible alteration of membrane calcium in primary hypertension. SUBJECTS AND METHODS: Thirty-four never treated patients with essential hypertension were included and 34 healthy, age- and sex-matched volunteers served as controls. Atomic absorption spectroscopy was used for measurement of intracellular and membrane calcium content in erythrocytes and plasmalemmal preparations. RESULTS: Plasma and intracellular Ca(++) concentrations were not significantly different between hypertensives and controls (plasma: 2.59 +/- 0.18 vs2.50 +/- 0.16 mmol/l, intracellular: 1.89 +/- 0.20 mmol/l vs 1.97 +/- 0.24 mmol/l, NS resp., mean +/- s.e.m.). However, membrane calcium content was significantly higher in hypertensive patients compared to control subjects (2.38 +/- 0.28 micromol/g membraneous protein vs0.86 +/- 0.32 micromol/g membrane protein, P < 0.01). Membrane calcium content was correlated to mean arterial blood pressure (r = 0.59, P < 0.01). CONCLUSION: Membrane calcium content is significantly increased in patients with untreated primary hypertension and correlates to blood pressure levels. This data suggest, that an membrane mechanism may contribute to alterations in calcium metabolism and to the pathogenesis of primary hypertension.

Antihypertensive treatment in renal transplant patients--is there a role for ACE inhibitors?

During the past two decades great progress was achieved with regards to short-term kidney graft survival. However, long-term graft survival did not improve similarly. Many factors contribute to chronic graft nephropathy eventually resulting in late graft loss, among these arterial hypertension is of major importance. In patients with chronic renal disease of diabetic and non-diabetic origin, angiotensin converting enzyme inhibitors have been convincingly shown to slow the progression of renal failure. The achieved nephroprotection correlates with the reduction of proteinuria by ACE inhibitor treatment. Also in renal transplant patients, ACE inhibitors have been shown unequivocally to reduce urinary protein excretion. The prevention of hyperfiltration, particular in the context of a reduced number of functional nephrons in patients with chronic graft nephropathy, could be important to prolong graft survival after renal transplantation. Moreover, ACE inhibitors may exert beneficial effects on immunologic processes contributing to chronic graft nephropathy. Many studies published in the last decade show convincingly that ACE inhibitors are safe and effective for the treatment of hypertension in renal allograft recipients. However, no data exist so far showing that ACE inhibitors are superior to other antihypertensive drugs in renal transplant patients and that they prolong graft survival. Studies investigating this issue are warranted. Apart from effects on the graft, ACE inhibitors may improve alterations of the cardiovascular system generally observed in renal transplant patients, such as structural alterations of large arteries, left ventricular hypertrophy, disturbed mechanical vessel wall properties and endothelial dysfunction. Therefore, angiotensin converting enzyme inhibitors could reduce cardiovascular morbidity and mortality in kidney transplant patients.

Impaired flow-mediated vasodilation of the brachial artery in patients with primary hyperparathyroidism improves after parathyroidectomy.

OBJECTIVE: The endothelium is a newly recognised target tissue of parathyroid hormone (PTH). It is not clear whether hyperparathyroidism affects endothelial function and whether parathyroidectomy (Ptx) has an influence on arterial vessel wall properties. We studied brachial flow-mediated vasodilation (FMD) and brachial and carotid intima-media thickness (IMT) in patients with primary hyperparathyroidism (pHPT) before and after Ptx and in healthy controls. METHODS: 19 patients with pHPT (mean+SEM, age 45+/-4.7 years, PTH 238+/-52 ng/l) were studied. Diabetes, hypertension and vascular disease were excluded. Twenty healthy volunteers matched for age, sex and blood pressure served as controls. Enddiastolic diameter, FMD and nitroglycerine-induced (NMD) dilation of the brachial artery were measured by a multigate pulsed doppler system (echo-tracking), IMT was determined using automatic analysis of the M-line signal. Healthy volunteers where studied on one occasion, patients were studied at baseline and 6 months after Ptx. RESULTS: Six months after Ptx PTH had decreased to normal, blood pressure levels remained unchanged. Endothelium dependent FMD at baseline was impaired in patients compared to controls (4.7+/-1.2 vs. 18.2+/-3.7%, P<0.01), however, FMD improved significantly after Ptx (16.7+/-3.0%, P<0.01). Nitroglycerine-induced dilation, IMT and artery diameter were not different between groups and did not change after Ptx. CONCLUSIONS: Impaired endothelium dependent vasodilation in patients with primary hyperparathyroidism improves after successful parathyroidectomy. Endothelial dysfunction associated with primary hyperparathyroidism occurs without detectable structural wall alterations of the brachial artery and appears therefore to be an early and reversible arterial alteration.

Effects of bicarbonate- and lactate-buffered replacement fluids on cardiovascular outcome in CVVH patients.

BACKGROUND: Bicarbonate-buffered replacement fluid (RF-bic) in continuous venovenous hemofiltration (CVVH) may be superior to lactate-buffered replacement fluid (RF-lac) in acute renal failure. In an open, randomized, multicenter study, we investigated the effects of RF-bic and RF-lac on cardiovascular outcome in patients requiring CVVH following acute renal failure. METHODS: One hundred seventeen patients between the age of 18 and 80 years were randomized to CVVH either with RF-bic (N = 61) or RF-lac (N = 56). Patients were treated with CVVH for five days or until either renal function was restored or the patient was removed from the study. Data were analyzed on day 5 or according to the "last observation carried forward" (LOCF) option. Adverse events were classified according to the WHO-Adverse Reaction Terminology system. RESULTS: Blood lactate levels were significantly lower and blood bicarbonate levels were significantly higher in patients treated with RF-bic than in those treated with RF-lac (lactate, 17.4 +/- 8.5 vs. 28.7 +/- 10.4 mg/dL, P < 0.05; bicarbonate, 23.7 +/- 0.4 vs. 21.8 +/- 0.5 mmol/L, P < 0. 01). The number of hypotensive crises was lower in RF-bic-treated patients than in RF-lac-treated patients (RF-bic 14 out of 61 patients, RF-lac in 29 out of 56 patients; 0.26 +/- 0.09 vs. 0.60 +/- 0.31 episodes per 24 h, P < 0.05). Nine out of 61 patients (15%) treated with RF-bic and 21 out of 56 patients (38%) treated with RF-lac developed cardiovascular events during CVVH therapy (P < 0. 01). A multiple regression analysis showed that the occurrence of cardiovascular events was dependent on replacement fluid and previous cardiovascular disease and not on age or blood pressure. Patients with cardiac failure died less frequently in the group treated with RF-bic (7 out of 24, 29%) than in the group treated with RF-lac (12 out of 21, 57%, P = 0.058). In patients with septic shock, lethality was comparable in both groups (RF-bic, 10 out of 27, 37%; RF-lac, 7 out of 20, 35%, P = NS). CONCLUSIONS: The results show that the administration of RF-bic solution was superior in normalizing acidosis of patients without the risk of alkalosis. The data also suggest that the use of RF-bic during CVVH reduces cardiovascular events in critically ill patients with acute renal failure, particularly those with previous cardiovascular disease or heart failure.

Studies on flow-mediated vasodilation and intima-media thickness of the brachial artery in patients with primary hyperparathyroidism.

The endothelium is a newly recognized target organ of parathyroid hormone (PTH) and may contribute to its effects on vascular tone and blood pressure regulation. Flow-mediated vasodilation (FMD), brachial and carotid intima-media thickness (IMT) were studied in patients with primary hyperparathyroidism (pHPT) and controls to evaluate endothelial function and structural arterial vessel wall alterations. Sixteen patients with pHPT (mean +/- SEM, age 44 +/- 5 years; PTH 229 +/- 72 ng/L; serum calcium 3.0 +/- 0.06 mmol/L; serum phosphate 2.0 +/- 0.2 mg/L) and 16 normocalcemic control subjects matched for age, sex, and blood pressure were included. Diabetes, hypertension, and vascular disease were excluded in both groups. End-diastolic diameter, flow-mediated (FMD) and nitroglycerin-mediated (NMD) dilation of the brachial artery were measured by a multigate pulsed Doppler system (echo-tracking). IMT was determined using automatic analysis of the M-line signal. Endothelium-dependent FMD was impaired in patients compared to controls (4.6 +/- 1.6% v 19.2 +/- 3.9%, P < .001). NMD (23.8 +/- 3.1% v. 22.4 +/- 2.8%, P = NS), carotid and brachial IMT (0.60 +/- 0.04 mm v 0.64 +/- 0.06 mm, P = NS, and 0.46 +/- 0.04 mm v 0.47 +/- 0.08 mm, P = NS, respectively) and artery diameters were not different. Endothelium-dependent vasodilation is impaired in patients with primary hyperparathyroidism despite normal IMT. Endothelial dysfunction may contribute to increased cardiovascular morbidity and mortality in pHPT.

Membrane, intracellular, and plasma magnesium and calcium concentrations in preeclampsia.

Changes in intracellular calcium and magnesium concentrations seem to be involved in the pathogenesis of preeclampsia, whereas the role of cell membranes has not been studied in detail yet. To investigate the changes in calcium and magnesium metabolism in normal pregnancy and preeclampsia, plasma, intracellular, and membrane calcium and magnesium concentrations were determined in a clinical study. Twenty-five control, 18 untreated healthy pregnant, and 16 nulliparas preeclamptic women were investigated. Plasma, cellular, and membrane (erythrocytes) calcium and magnesium contents were measured by atomic absorption spectroscopy. Plasma and intracellular magnesium concentrations were significantly lower in the healthy pregnant group and the preeclamptic group as compared to controls (P < .01). In erythrocyte membranes magnesium content was found significantly decreased in the preeclamptic women as compared to healthy subjects (P < .001). There was a significant decrease in the plasma calcium concentration in the preeclamptic group compared to controls or healthy pregnant women (P < .05). Membranous calcium content was significantly increased in the preeclamptic group versus controls or healthy pregnant women (P < .001) and an inverse correlation with membranous magnesium content was found (r = -0.79,P < .01). Lowered plasma, intracellular, and membrane magnesium concentrations in preeclampsia may contribute to the development in hypertension in pregnancy. In addition, a disturbed calcium homeostasis is observed in preeclampsia.

Measurement of skeletal status after renal transplantation by quantitative ultrasound.

BACKGROUND: Osteoporosis remains a major problem following kidney transplantation. Radiographic measures of bone mass are of limited predictive value after transplantation and are complicated by preexisting renal osteopathy. Quantitative ultrasound (QUS) is a new and non-invasive method to assess skeletal status, however, no data exist on ultrasonic bone parameter after kidney transplantation. We evaluated the potential use of this novel method in renal allograft recipients and studied the accuracy compared to normal controls. METHOD: Thirty patients (NTP, age 47.5 +/- 13.0 years) were studied 4.8 +/- 3.2 years after transplantation. Twenty-five healthy control persons (CON) were matched for age and sex. The left and right os calcis were studied by QUS and speed of sound (SOS) and broadband ultrasound attenuation (BUA) were measured. Bone stiffness (BS) was calculated from these parameters and corrected for age (CBS). Differences between right and left os calcis were compared to CON to assess the side variability. RESULTS: Mean +/- SD BS was 75 +/- 22% compared to young adults, age-corrected CBS was decreased in NTP with 86 +/- 25% of normal, indicating a two-fold increased risk of fracture. SOS was 1525 +/- 47.7 m/s, BUA 105 +/- 22 dB/MHz. Mean difference between right and left os calcis was significantly higher in NTP than in CON (7.2 +/- 7.1% vs. 2.1 +/- 2.1%, p < 0.01). Limits of agreement of the measurements (MW of differences +/- 2 SD) according to a Bland-Altmann-type statistic were -16.9% and 20.7%. There was no correlation between CBS and age, cumulative steroid dose, parathyroid hormone concentrations or time after transplantation. CONCLUSION: Our data show altered bone structure expressed by low bone stiffness values measured by quantitative ultrasound in kidney transplant patients. However, because of relatively high inter-feet variance of QUS results we suggest measurement of both ossa calcis to minimize measurement error after transplantation.

[Alterations of arterial vessel wall properties in hyperparathyroidism]. / Funktionelle Gefässwandveränderungen bei Hyperparathyreoidismus.

Alterations of arterial vessel wall function are associated with increased cardiovascular morbidity and can be measured by noninvasive ultrasound techniques. There is increasing evidence that hyperparathyroidism contributes not only to structural changes of the cardiovascular system but to disturbances in functional arterial vessel wall properties. It has been shown that elevated concentrations of parathyroid hormone are associated with decreased arterial distensibility and increased intima-media thickness in patients with renal insufficiency. A permissive role of parathyroid hormone in the pathogenesis of uremic vessel wall changes has been discussed. The endothelium is a newly recognized target organ of parathyroid hormone. In patients with primary hyperparathyroidism endothelial dysfunction has been demonstrated, that seems to be reversible after parathyroidectomy. Effects on arterial vessel wall function may contribute to increased blood pressure observed in hyperparathyroidism. The complex cardiovascular effects of parathyroid hormone and changes in vascular tone, arterial distensibility and endothelial function in hyperparathyroidism are discussed.

[Extracorporeal renal replacement therapies in acute renal failure]. / Extrakorporale Therapieverfahren bei akutem Nierenversagen.

The most serious forms of acute renal failure (ARF) are nowadays encountered in the intensive care unit (ICU), where up to 25% of new patients are reported to develop ARF. Lethality rates may reach 50 to 90% when the ARF is part of a multiple organ dysfunction syndrome. A multitude of extracorporeal procedures have been introduced into intensive care medicine. Applied with adequate skills and experience, most of these techniques will suffice to replace excretory renal function. However, because of low efficacy arterio-venous procedures (CAVH and CAVHD) have been abandoned for the veno-venous, pump-driven techniques (CVVH and CVVHD). Up to now, there is no consensus whether continuous or intermittent renal replacement therapy is more advantageous. In many cases, oliguric patients with circulatory instability will be treated by CVVH, even though there is no prospective study to show that in terms of outcome continuous treatment is superior to intermittent hemodialysis. It is equally conceivable to treat such patients with daily, prolonged (intermittent) hemodialysis. Apparently, the dose of replacement therapy, be it continuous filtration (36 to 48 l/24 h) or intermittent hemodialysis (daily 3 to 4 h) with a target BUN of less than 50 mg/dl, is more important than the modality of treatment. Moreover, there is good evidence that the use of biocompatible membranes (no complement- or leukocyte activation) is preferable and that with high-volume hemofiltration bicarbonate-containing replacement fluids should be used. However, despite all the technical advances, we firmly believe that the skills and the experience of those physicians and nurses who actually perform renal replacement therapy in the ICU are more important than the modality of treatment applied.

[Alterations of the arterial vessel wall in renal failure]. / Gefässwandveränderungen bei Niereninsuffizienz.

Cardiovascular events are the main cause of death in patients with end-stage renal disease. Functional and structural alterations of the arterial system substantially contribute to the high cardiovascular mortality in these patients. Structural alterations of the arterial wall comprise intima-media thickening and atherosclerotic plaque formation. Moreover, mechanical vessel wall properties of large arteries are significantly disturbed. This is already observed in young patients. Reduced arterial distensibility impairs large artery cushioning function. This results in increased ventricular afterload promoting left ventricular hypertrophy and in reduced coronary perfusion. After renal transplantation, structural alterations of the arterial wall and disturbed mechanical vessel wall properties persist. Moreover, renal failure is characterized by a severe impairment of endothelial function. Disturbed endothelial function results from reduced production of endothelium-dependent endogenous vasodilators and/or blunted vascular effects of these substances. Uremia is associated with the accumulation of an endogenous inhibitor of the endothelial nitric oxide synthase. Impaired endothelial function in renal failure promotes the progression of structural lesions of the arterial wall. Also in renal transplant recipients, substantially impaired endothelial function is observed despite correction of uremia. Hyperparathyroidism commonly observed in renal failure contributes to the disturbed functional vessel wall properties of large arteries. In patients with end-stage renal disease, decreased large artery distensibility is an independent risk factor for increased cardiovascular mortality. This may apply also to intima-media thickening and to impaired endothelial function.

Alterations of plasma calcium and intracellular and membrane calcium in erythrocytes of patients with pre-eclampsia.

BACKGROUND: Changes in plasma and intracellular calcium levels have been suggested in the pathogenesis of pre-eclampsia, however, membrane calcium content has not been studied so far. We compared intracellular and membrane calcium concentrations in erythrocytes of women with pre-eclampsia, healthy pregnant woman and controls to determine a possible alteration of membrane calcium in pre-eclampsia. SUBJECTS AND METHODS: Eighteen untreated, healthy pregnant woman and 16 pregnant nulliparous women with manifest pre-eclampsia were included, 25 healthy, age-matched woman served as controls. Atomic absorption spectroscopy was used for measurement of intracellular and membrane calcium content in erythrocytes and plasmalemmal preparations. RESULTS: Plasma Ca++ concentrations were significantly lower in pre-eclamptic women (1.96 +/- 0.15 mmol/l, P < 0.01, mean +/- s.e.m.) compared to healthy controls (2.43 +/- 0.14 mmol/l) or women with uncomplicated pregnancies (2.20 +/- 0.10 mmol/l). Intracellular Ca++ concentrations were not different between groups, however, membrane Ca++ content was significantly increased in the pre-eclamptic patients (1.23 +/- 0.36 micromol/g membrane protein, P < 0.01) compared to control subjects (0.83 +/- 0.16 micromol/g) and healthy pregnant women (0.77 +/- 0.13 micromol/g). CONCLUSION: Membrane calcium content is significantly increased in pre-eclamptic women despite low plasma Ca++ concentrations. This finding suggests an altered membrane ion transport and may be of importance for the pathogenesis of pre-eclampsia.

Vessel wall alterations in patients with renal failure.

Cardiovascular complications are a major cause of morbidity and mortality in patients with renal failure. Death due to myocardial infarction and to stroke is more frequent in hemodialysis patients than in the total population. These cardiovascular diseases are mainly the consequence of atherosclerosis and cause decreased life expectancy in patients with renal failure. Ultrasound techniques now make it possible to measure atherosclerotic lesions in big and medium-sized arteries. Thickening of the intima-media-complex is an early sign of atherosclerosis in these vessels. It reduces the distensibility of the arteries during systole. The distensibility of big and medium-sized arteries can be determined using ultrasound-doppler-techniques. In our studies, the intima-media-thickness of the carotid artery was significantly (p< 0.01) increased in patients with chronic renal failure (1.32+/-0.49 mm, n=28) as compared with aged-matched healthy control subjects (0.75 +/- 0.20, n= 29). The distensibility coefficient was higher (p< 0.05) in healthy controls (26 +/- 1.8 10(-3)/kPa, n= 12) than in patients with renal insufficiency (19 +/- 1.7 10(-3)/kPa, n = 12). This demonstrates increased stiffness of the vessel wall resulting in loss of Windkessel function and increased work load of the heart.