PubMed Health⌕ Search

Biomedical subjects

J Ribstein

Publications and source records attributed to J Ribstein.

At least 73 records · Page 4Linked to original sources
PubMed1992

Sodium and left ventricular mass in untreated hypertensive and normotensive subjects.

To determine whether urinary sodium excretion (a rather rough estimate of sodium intake) can influence left ventricular mass independently of arterial pressure, 91 untreated subjects with essential hypertension and 50 normotensive subjects of similar age were studied. Left ventricular mass index (M-mode echocardiography) was positively correlated with urinary sodium excretion in hypertensive (r = 0.22, P less than 0.01) as well as normotensive subjects (r = 0.22, P less than 0.05), and systolic arterial pressure was correlated only in hypertensive subjects (r = 0.23, P less than 0.01). When hypertensive subjects were divided into groups with appropriate or inappropriate left ventricular mass by reference to a theoretical optimal left ventricular mass for each subject's level of systolic arterial pressure, left ventricular mass was appropriate in 68% and inappropriate in 32% of subjects. Urinary sodium excretion was higher in subjects with inappropriate left ventricular mass compared with those with appropriate left ventricular mass. In conclusion, sodium excretion may be an important modulator of the influence of arterial pressure on the left ventricle in normotensive subjects and subjects with essential hypertension.

Adolescent↗
PubMed1992

Mechanisms of renal hemodynamic impairment during infrarenal aortic cross-clamping.

Infrarenal aortic cross-clamping is associated with impairment of renal hemodynamics due to vasoconstriction, the mechanism of which remains under debate. To assess the renal effect of two potent renal vasodilators (enalapril, a converting enzyme inhibitor, and nicardipine, a calcium antagonist), 24 patients scheduled for reconstructive aortic surgery were randomly allocated to one of three treatment groups (n = 8 each) and received either a placebo, nicardipine, or enalapril. Anesthesia consisted of flunitrazepam, fentanyl, pancuronium, and, occasionally, droperidol. Although aortic cross-clamping was associated with no change in mean arterial blood pressure, decreased cardiac output and increased systemic vascular resistance occurred in control patients (33% and 43%, respectively, both P less than 0.05 versus baseline) and nicardipine-treated patients (51.7% and 67.7%, respectively, both P less than 0.05 versus baseline); however, changes in cardiac output and systemic vascular resistance failed to reach significance in enalapril-treated patients. Glomerular filtration rate (technetium 99-diethylenetriaminepentacetic acid clearance) and effective renal plasma flow (iodo-Hippuran 131 clearance) decreased for the duration of aortic cross-clamping in control patients (42.9% and 18.5%, respectively, both P less than 0.05 versus baseline) and enalapril-treated patients (34.0% and 38.1%, respectively, both P less than 0.05 versus baseline), but no change was observed in nicardipine-treated patients. These results suggest that the reninangiotensin system is not an important determinant of the renal vasoconstriction associated with aortic cross-clamping. In contrast, renal dysfunction may be alleviated by the dihydropyridine derivative nicardipine, which probably acts at the level of the preglomerular resistance vessels.

Adult↗
PubMed1992

Antihypertensive therapy in renal disease and transplantation.

HYPERTENSION AND RENAL DISEASE: In experimental models of renal disease not only protein intake and hyperlipidaemia but also hypertension may contribute to the progressive deterioration in renal function; in these models an imbalance in intrarenal haemodynamics appears to be a particularly important factor. ANTIHYPERTENSIVE THERAPY: A reduction in arterial pressure can alter the course of human chronic renal disease. However, it is not clear whether any one class of antihypertensive drug is superior to any other class in these patients. Angiotensin converting enzyme (ACE) inhibitors may prevent the progression from incipient to overt diabetic nephropathy and afford better protection than conventional treatment. In patients with non-diabetic renal disease there is no unequivocal evidence for a protective effect. In renal transplant recipients, mainly those taking cyclosporine, ACE inhibitors are equally effective compared to calcium antagonists in the control of hypertension, but their renal effects in transplant recipients without renal artery stenosis have not yet been assessed.

Acute Kidney Injury↗
PubMed1992

[Left systolic ventricular function and metabolic disorders in untreated hypertensive patients].

Previous studies have shown that essential hypertension is frequently associated with insulin resistance and hyperinsulinism. Because insulin may exert a direct positive inotropic as well as chronotropic effect and controlled the initiation of peptide chains in the heart, we tested the hypothesis that insulin may be a determinant of myocardial hypertrophy and contractility. The relation between glucose metabolism (assessed by the oral glucose tolerance test) and left ventricular (LV) mass and function (assessed by echocardiography) was explored in 47 never-treated lean essential hypertensive patients (EH) of short duration and 19 normotensive subjects (NT). A greater number of EH versus NT (23 vs 5%) had an abnormal glucose tolerance. The fasting insulin-to-glucose ratio was significantly higher in EH as compared to NT. Fasting as well as integrated serum insulin to glucose values ratio were positively correlated with heart rate (r = 0.35, p < 0.05, r = 0.38, p < 0.05) and the LV end-systolic stress to volume ratio (r = 0.48, p < 0.001, r = 0.54, p < 0.001) but not with LV mass (r = 0.02, r = 0.02) in EH. When EH were divided into those with normal (n = 36) and supernormal (n = 11) LV contractility based on the relationship between LV fractional shortening and LV end-systolic stress, integrated insulin level and fasting insulin to glucose ratio were markedly higher in patients with supernormal LV contractility, whereas arterial pressure, heart rate, urinary sodium excretion, and plasma renin activity were similar in the two groups. We concluded that hyperinsulinemia and LV hypercontractility are associated in patients with hypertension of short duration. If chronic hyperinsulinemia is to be causally related to hypertension, one would have to postulate that the effects (inotropism and chronotropism) of insulin on the heart can be dissociated from the resistance to the glucose-lowering action of insulin.

Blood Glucose↗
PubMed1992

Aging and sodium homeostasis.

Deterioration of glomerular filtration rate appears to be progressive throughout life whereas sodium intake tends to remain constant. The influence of aging may be amplified by intrinsic renal disease, unilateral nephrectomy or renovascular abnormalities. Changes in the tubular reabsorption of sodium will allow the excretory capacity of the kidney to adjust to fluctuations in normal sodium intake. However, restriction of dietary sodium may be associated with a sluggish renal response; a sodium wasting state that could lead to significant deterioration in renal function and orthostatic hypotension, may occur. Conversely, increasing dietary sodium in older subjects may result in a rise in arterial pressure more often than in younger subjects. Dietary sodium restriction should be carefully controlled in elderly subjects.

Aging↗
PubMed1991

[Functional reversibility of chronic cyclosporine nephrotoxicity in patients after kidney transplantation].

The long term use of cyclosporin in renal transplant recipients may be complicated by chronic nephrotoxicity, evidenced by renal functional deterioration and suggestive histological lesions. In 11 renal transplant recipients treated with cyclosporin since 28 +/- 5.8 months, we reduced (n = 6) or stopped (n = 5) this drug after chronic nephrotoxicity was diagnosed. Five months later, we conducted hemodynamic studies and observed significant increases in renal plasma flow (I131 hippuran clearance from 239.5 +/- 106 to 327 +/- 50 ml/min/1.73 m2) and glomerular filtration rate (DTPA-TC clearance from 43 +/- 15 to 67 +/- 10 ml/min/1.73 m2) and a decrease in renal vascular resistances. We suggest that cyclosporin-associated chronic nephrotoxicity is accompanied by some degree of reversible vasoconstriction, or that histological lesions, particularly cyclosporin arteriolopathy, can disappear after cyclosporin withdrawal.

Chronic Disease↗
PubMed1991

[Simplified strategy for anesthesia of pheochromocytoma].

The only curative treatment of phaeochromocytoma consists in surgical removal. This carries a high risk due to the acute release of catecholamines. General anaesthesia cannot by itself prevent haemodynamic disturbances during surgical manipulation of the tumour. Careful preparation, based on intravascular volume repletion as well as alpha-, and, if required, beta-adrenergic blockade, has been shown to reduce morbidity and mortality. However, this protocol is often cumbersome, and does not prevent totally the haemodynamic instability as a decrease in blood pressure at the start of treatment, or after removal of the tumour. Since voltage-dependent calcium channels are involved in both secretion and action of catecholamines, calcium-channel antagonists might be an interesting therapeutic alternative. In fact, short-term treatment by dihydropyridines may attenuate blood pressure variability during the preoperative period. During surgery, a dose-dependent reduction in systemic vascular resistances has been shown with intravenous nicardipine. However, dihydropyridines do not control cardiac adrenergic stimulation, which causes tachycardia or persistently increased blood pressure in spite of low or normal systemic vascular resistances. Such an acute cardiac hyperactivity, which can only be assessed by continuous haemodynamic monitoring, is electively sensitive to a beta-adrenergic blocker rather than a calcium channel antagonist with high cardiac affinity (diltiazem, verapamil). Esmolol is available for intravenous administration. It is an ultra-short acting agent, ensuring a selective dose-related cardiac beta 1-blockade. Combining esmolol with nicardipine gives control over almost all episodes of haemodynamic worsening during phaeochromocytoma resection. Preoperative medical treatment no longer aims to suppress adrenergic stimulation completely, but to prevent acute haemodynamic changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗
PubMed1991

Converting enzyme inhibitors and renal function in essential and renovascular hypertension.

Converting enzyme inhibitors (CEI) are useful in the treatment of hypertension. However, acute renal deterioration may occur in some conditions in association with the crucial role of angiotensin in the regulation of glomerular filtration rate (GFR), such as volume depletion, severe stenosis of both renal arteries, and stenosis of a single functioning kidney. CEI-induced acute renal failure can develop in the absence of a fall in systemic pressure, is facilitated by prior sodium depletion, and is reversible upon discontinuation of treatment. In a personal study conducted in 28 patients with CEI-induced renal dysfunction (reversible after discontinuation of CEI), the incidence of stenosis of large renal vessels was 61%, whereas 39% of these subjects had no significant renal artery abnormalities. Although the occurrence of such a complication is not a convincingly accurate predictor of the existence of renovascular hypertension, angiographic detection of renal artery stenosis (bilateral or on a single-functioning kidney) may be justified in some of these patients.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1991

Renal changes associated with cyclosporine in recent type I diabetes mellitus.

The effects of cyclosporine A treatment on arterial pressure and renal function were assessed in 11 young patients with type I diabetes of short duration. Cyclosporine was started at 7.5 mg/kg/day, progressively decreased to 6.3 mg/kg/day at 6 months, and then continued at a lower dose (4.1 mg/kg/day) for an additional 3 months in patients in whom remission of insulin dependency was obtained (n = 6). After 3 months of cyclosporine, a slight but significant increase in arterial pressure (+5.2 +/- 1.5 mm Hg), a rise in renal vascular resistance (approximately 20%), a decrease in glomerular filtration rate (approximately 25%), and a fall in filtration fraction were observed. Such changes were sustained after 6 and eventually 9 months of therapy. The decrease in glomerular filtration rate observed during cyclosporine treatment contrasted with the lack of change in simultaneously estimated creatinine clearance; in fact, the creatinine clearance/glomerular filtration ratio increased from 1.07 +/- 0.05% to 1.33 +/- 0.09% within 3 months of cyclosporine therapy, thus suggesting an enhanced tubular secretion of creatinine. Plasma renin activity and urinary excretion of kallikrein decreased significantly (approximately 50%), whereas plasma aldosterone concentration remained unaltered and plasma concentration of potassium increased during cyclosporine therapy. These changes were observed in the presence of a constant urinary excretion of sodium and potassium and a constant body weight. All parameters returned to pretreatment values within 3 months after cessation of cyclosporine. These results indicate that cyclosporine given for 6-9 months at a moderate dose causes a deleterious but reversible effect on arterial pressure and renal function in young diabetic patients.

Adolescent↗
PubMed1991

Blood pressure reduction as a preventive treatment of diabetic nephropathy.

Arterial hypertension is present in 10-80% of newly diagnosed Type 2 diabetics, and in 30-50% of Type 1 diabetics after some years. In patients with overt nephropathy, correction of hypertension is associated with a reduction in the rate of decline of glomerular filtration rate. In most patients without clinical diabetic nephropathy, arterial pressure remains within normal limits as defined by usual criteria, whether or not microalbuminuria is present. Short-term studies of Type 1 diabetics with microalbuminuria suggest that angiotensin-converting enzyme inhibitors result in a fall in urinary albumin excretion rate more than calcium antagonists and diuretics. Additional studies assessing the long-term effect of different antihypertensive agents on the evolution of early diabetic nephropathy are needed before the superiority of any drug can be claimed. In addition, non pharmacological approaches, including optimal glycemic control as well as modification of dietary sodium and serum lipid profile, may alter the progressive course of elevation in arterial pressure and decline in renal function. The optimal level of blood pressure for diabetic patients remains to be determined.

Albuminuria↗
PubMed1991

[Extravascular transfer of fluids and proteins induced by endothelin in the binephrectomized rat].

To test the possibility that endothelin affects extracellular fluid partition between plasma and interstitium, we compared the effects of endothelin and vehicule in euvolemic binephrectomized anesthetized rats by measuring changes in hematocrit and plasma protein concentration. Forty-five minutes infusion of endothelin (25 ng/kg/min) induced a progressive increase in blood pressure by 1.7 +/- 1.3, 6.8 +/- 1.5 and 12.1 +/- 2.1% at 15, 30 and 45 min respectively from a basal value of 99 +/- 5 mmHg. Hematocrit increased by 8.0 +/- 0.6% (p less than 0.001) after 45 min of infusion, while the vehicle had no significant effect (+ 1.7 +/- 0.7%). The same increase in hematocrit was observed in binephrectomized and splenectomized rats. The calculated loss of plasma volume during endothelin infusion was 13.1 +/- 0.9% as compared to 2.1 +/- 1.2% in rats receiving the vehicle. Plasma protein concentration increased by only 4.2 +/- 0.6% suggesting an extravasation of proteins. To document and localize an alteration in vascular leak of proteins induced by endothelin, albumin-bound Evans Blue (EB) extravasation was measured spectrophotometrically in different tissues after extraction by formamide. Endothelin increased vascular permeation of EB-albumin in skeletal and cardiac muscle, intestine and mesentery. No change was observed in brain, liver, spleen as compared to rats receiving the vehicle. In addition, endothelin infusion elicits a three fold increase of the plasma immunoreactive atrial natriuretic peptide (ir-ANP) concentration (from 196 +/- 50 to 722 +/- 203 pg/ml; p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effect of different calcium antagonists on transcapillary fluid shift.

Chronic treatment with dihydropyridines, and to a lesser extent other calcium antagonists, often results in peripheral edema without fluid retention. The possibility that calcium antagonists affect extracellular fluid volume partition was tested by comparing the effects of nicardipine (Nic), diltiazem (Dil) and Vehicle (Veh) on hematocrit and plasma protein concentration in anephric anesthetized rats. In response to a 45 min infusion of Nic (0.1 or 1 micrograms/kg/min) and Dil (10 or 100 micrograms/kg/min), blood pressure decreased by 4 or 21%, and 4 or 19%, respectively, whereas hematocrit increased only with both doses of Nic (5.3 +/- 0.2 and 5.5 +/- 0.2%). Plasma protein concentration also increased significantly, although slightly, in the Nic group. The possibility of protein extravasation was then assessed using Evans blue dye as a marker. The drug-induced extravasation of dyed albumin in skeletal and cardiac muscles, but not other organs, was significantly increased following Nic, as compared to Dil or Veh. These observations suggest that two structurally different calcium antagonists used at equihypotensive doses may exert different effects on extracellular fluid partition.

Animals↗
PubMed1990

Effect of angiotensin converting enzyme inhibition on blood pressure and renal function during open heart surgery.

Activation of the renin-angiotensin system during open heart surgery may have consequences both beneficial in sustaining blood pressure and deleterious in compromising renal hemodynamics. The influence of short-term pretreatment with captopril on blood pressure and renal function was assessed double-blind versus placebo in 18 patients without pre-existing cardiac or renal failure, and undergoing coronary artery bypass. No difference in blood pressure and fluid requirement during the surgical period was observed between groups receiving captopril or placebo. Effective renal plasma flow and glomerular filtration rate decreased in the placebo group whereas they remained unaltered in the captopril group; during cardiopulmonary bypass, urinary excretion of sodium was greater in patients receiving captopril than those receiving placebo. These results suggest that captopril pretreatment does not compromise the control of blood pressure and renal function during open heart surgery; additional studies on the protective value of angiotensin-converting enzyme inhibitors are warranted in patients at higher risk for developing renal failure.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1990

Diabetic nephropathy in normotensive patients.

Arterial pressure is within 'normal' limits in most diabetic patients with or without microalbuminuria and elevated in 70% of patients with overt diabetic nephropathy. An abnormal increase in the level of urinary excretion is a strong predictor of the subsequent development of overt diabetic nephropathy and ultimately renal insufficiency. Correction of hypertension is associated with a reduction in the rate of decline of the glomerular filtration rate in overt diabetic nephropathy. In patients with microalbuminuria, short-term studies have shown that angiotensin converting enzyme (ACE) inhibitors, in contrast with calcium antagonists, decrease urinary albumin excretion. Additional studies assessing the long-term effect of antihypertensive agents on the evolution of early diabetic nephropathy are needed. The superiority of ACE inhibitors over other antihypertensive agents in the treatment of overt or early diabetic nephropathy remains to be demonstrated. In addition to arterial pressure control, it is possible that optimal glycaemic control in addition to the modification of protein intake, dietary sodium and serum lipid profile may alter the course of diabetic nephropathy.

Animals↗
PubMed1990

Role of atrial peptide in the acute natriuretic response to uninephrectomy.

Unilateral nephrectomy (UNX) is associated with an immediate natriuretic response of the remaining kidney. The role of atrial natriuretic peptide (ANP), as assessed by right atrial appendectomy (APX), was investigated in euvolemic anaesthetized rats. In sham APX rats, UNX resulted in a twofold increase in urinary sodium and potassium excretion (1.03 +/- 0.11 to 2.08 +/- 0.17 and 1.39 +/- 0.05 to 2.26 +/- 0.08 mueq/min, respectively) and a doubling of urinary excretion of guanosine 3',5'-cyclic monophosphate (cGMP). No significant change in glomerular filtration rate, renal plasma flow, and lithium clearance occurred in response to UNX. APX totally prevented the UNX-induced natriuresis and diuresis as well as the rise in urinary cGMP. Post-UNX plasma concentration of ANP was higher in sham-operated compared with APX rats (45 +/- 9 vs. 20 +/- 2 fmol/ml). In sham APX rats, UNX was associated with a transient (less than 15 min) rise in arterial pressure; in APX rats, this immediate increase in arterial pressure was of similar magnitude but of longer (greater than 30 min) duration. The observed stimulation of ANP release after UNX and the blunting of the natriuretic response to UNX by APX suggest that ANP may be an important mediator of the renal response to contralateral renal ablation.

Animals↗
PubMed1990

[Pre- and postoperative antihypertensive treatment with calcium antagonist in pheochromocytoma].

Medical preparation for pheochromocytoma surgery requires adrenergic blockade and restoration of euvolemia. Usually, this preoperative preparation consisted essentially of sequential and progressive adrenergic antagonism, alpha then beta blockade. This therapy is not easy to introduce and exposes to blood pressure collapses after tumor removal. By contrast, calcium channel blocking drugs like dihydropyridines offer efficacy and safety. Moreover, new intravenous (IV) agents (nicardipine, diltiazem) provide useful therapeutic tools to control, rapidly and with a dose-dependent effect, any undesired hemodynamic event during surgery. As a demonstration of this new therapeutic strategy for management of pheochromocytoma resection, we report here the cases of two patients who were exclusively treated with dihydropyridines. A 61 year-old woman and a 41 year-old man were scheduled for pheochromocytoma resection (left and right adrenal tumors, respectively). Both patients received dihydropyridines for preoperative preparation (nicardipine and nifedipine, respectively, 60 mg/day). This treatment allowed a good control of arterial blood pressure (BP) (from 210/110 to 170/90 and 180/100 to 140/80 mmHg, respectively) and was maintained up to the morning of the operative day. After patient installation on the operating-table, IV nicardipine infusion was started (2 mg/hour). Anesthesia consisted of high doses of fentanyl, flunitrazepam and vecuronium. Hemodynamic measurements (radial artery and Swan ganz catheters) allowed adjustment of nicardipine infusion rate to maintain peripheral arterial resistances under 1,000 dynes.s.cm-5, and adequate volume loading. A hypertensive crisis (270/130 mmHg) occurred at the time of the intubation in the first case but responded to higher infusion rate of nicardipine (5 mg/10 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗